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Plants are part of nature and technology is a result of human invention and resourcefulness. Both are united in the horticultural sector. That is true in all countries of the world. The horticulturist is always looking to develop and optimise the production with the local natural conditions: water, light, temperature, soil and nutrients. The Dutch are world famous for their greenhouses and highly developed horticultural technology, which is internationally acclaimed as a world leader for the last several decades. The greenhouses, together with all the associated technology, are also recognised as not only offering an advantage to growing in cold climates but can also be adapted for horticultural production in dry and hot environments. The greenhouse can even make it possible to grow a crop in the snow or in the desert. The difference is in the energy balance. There is one important aspect that all the different countries have in common; the number of mouths that need feeding is continuing to rise. It is therefore more likely that the farmers and horticulturists can resolve this problem more effectively than the politicians. The politicians are expected to create the right conditions whereby the food producers can optimise food production. After the first edition of Holland Horticultural Technology Review we reviewed what would provide a good balance for our thousands of enthusiastic readers; what they found most interesting. We have many thousand keen readers in India, Pakistan, Russia and Eastern Europe, the United States of America, Canada and many other countries. We have chosen to publish in the English language as this will make the publication accessible to the majority of our readers.

Ad van Gaalen Editor-in-chief

Ad van Gaalen Editor-in-chief




contents Preface Ad van Gaalen, editor-in-chief 

Published by Uitgeverij Lakerveld bv, in cooperation with International Horti Fair P.O. Box 160 2290 AD Wateringen e-mail: website: Editorial Team Ad van Gaalen (editor-in-chief) telephone: +31 (0)70 3364600 telefax: +31 (0)70 3364601 e-mail: Frans-Peter Dechering (Horti Fair) Harrie Jabroer (copy-editor) Joeri van der Kloet (editor) Sytse Berends (editor) Paul Waayers (editor)

Preface Frans-Peter Dechering, Director Horti Fair  5 Rolan Robotics

De daylight Greenhouse use of Fresnell-lenses 10



New mobile sorting system 


The plant as evaporator 


handling flowers 

Nanotechnology improves



light transmission 


Greenport Holland International 



reduce water usage

Subscriptions Irene Semp telephone: +31 (0)70 3364660 telefax: +31 (0)70 3364670 e-mail:


Faster and more homegeneous

Photography Joeri van der Kloet

Copyright Š 2012 Uitgeverij Lakerveld bv Copyright Š title International Horti Fair All rights reserved. No part of Holland Horticulture Technology Review may be Reproduced in anyway shape or form without Written permission from the publisher.

Moisture sensor  Washing and chalking

Design Uitgeverij Lakerveld bv Timmy de Jong

Mediaorder Ronald Romijn telephone: +31 (0)70 3364672 telefax: +31 (0)70 3364670 e-mail: Sonja Bruin telephone: +31 (0)70 3364673 telefax: +31 (0)70 3364670 e-mail:


robotising in horticulture 

Translation Vertaalbureau Bothof bv

Advertisement Uitgeverij Lakerveld bv Chris Crauwels telephone: +31 (0)70 3364675 telefax: +31 (0)70 3364670 e-mail:



Growing tomatoes, but in a different way 


Easykit pipe rail trolley 


Building profitable

greenhouses36 Measuring throughout

the greenhouse 


30 Advertisement index Brinkman International  Empas  HortiFair  Klimrek  VDH Solar Systems


2 43 38 43 44


Horti Fair promotes knowledge exchange in horticultural ‘manufacturing’ industry Horticulture is a significant ‘manufacturing’ industry. But where would horticulture be without knowledge exchange? This rhetorical question was the starting point for the HortiSeminars, which were initiated last year during the Horti Fair. The knowledge from those seminars has been collected in a special publication by Horti Fair and Wageningen UR: ‘Knowledge Review: Towards Sustainable Horticulture’. In 2011 Horti Fair had 23,240 visitors from 65 countries. Over the course of four exhibition days, there was a collective total of 27,500 visits to the fair. A survey showed that, of all the visitors, 62 % found the fair to be ‘successful’ to ‘very successful’ in promoting and exchanging knowledge. That knowledge exchange also took place during the HortiSeminars and the International HortiCongress. “In 2011, Horti Fair took on a new dimension: from square metres to cubic metres,” says Frans-Peter Dechering, director of Horti Fair. “Knowledge exchange is one of the most important aspects, which is why we started the International HortiCongress and the HortiSeminars. Visitors were given answers to important and current production issues.” Both parts of the fair will be repeated in 2012. The International HortiCongress will take place on the first exhibition day, 30 October 2012. The theme of this gathering will be Wellbeing, with the precise content being announced in the coming months. As in 2011, we can expect key international speakers during the International HortiCongress. The programme of the HortiSeminars is developed in consultation with exhibitors, with the aim of informing visitors concisely on current horticultural issues. Last year, for example, among the items on the agenda were Supply Chain, doing business in China and LED lighting. Horti Fair and Wageningen UR decided to collate the knowledge that had been exchanged during the HortiSeminars in 2011, and at the end of March the publication ‘Knowledge Review: Towards Sustainable Horticulture’ was issued. Says Dechering: “On the one hand, we are documenting the knowledge from the seminars, for example for horticultural professionals who could not attend. On the other hand, the Knowledge Review is an excellent snapshot of the current situation: what are the issues that are now relevant to horticulture as an important manufacturing industry, and what questions remain to be answered?” The first copies of the Knowledge Review were presented on 21 March to the members of the Horticulture and Propagation Materials top team, including Loek Hermans. This took place during the spring conference of Greenport Holland, of which Hermans is the chairman. The presentation was given also on behalf of the hundred companies who co-operated on the HortiSeminars and the International HortiCongress during Horti Fair 2011. The Knowledge Review is free to participants in the HortiSeminars of 2011 and to the companies that co-operated in the seminars. Preparations for Horti Fair 2012 are now fully underway. Dechering: “In 2011 we redesigned the exhibition, among other things by developing and supporting many new initiatives. Horti Fair 2011 therefore focused on the ‘new’. We will carry on with this innovation and Horti Fair 2012 will focus on the ‘improved’. We will accordingly make it an even better exhibition.” Horti Fair 2012 will be held from 30 October to 2 November in Amsterdam RAI. For more information, go to: and @hortifair–int.

Frans-Peter Dechering Director Horti Fair



Frans-Peter Dechering Director Horti Fair



Robotising according to

Rolan Robotics Many horticultural tasks are already automated. Processing pot plants and plugging cuttings are successful examples. The single-unit processing of vegetables and fruit is often more difficult to automate, however. Rolan Robotics explains why robotising is so complicated and what the future of robots could be like.


Paul Barends of Rolan Robotics says: ‘The well-known sweet pepper traffic light flow packaging, topping off tomato packs or handling small plastic trays: all those labour-intensive processes are done by hand. However, I think that a number of trends will put more pressure on this type of labour in horticulture. Good examples are the low cost price of low-wage countries, salary increases for Eastern European employees and the limited availability of work permits in the Netherlands. In short, enough reasons to justify the use of robots from an economics point of view.’ To decide whether the robot could be of interest for certain applications, it is important to take a closer look at the different aspects of the robot system. Paul explains: ‘The robot consists of two inextricably connected components: the robot arm itself and the controls. The robots that are of most interest for greenhouse horticulture are the 6-axis articulated arm robot and the Scara robots. Other robot types were added in the previous period, such as the Delta robot, also referred to as the Spin robot.’ The articulated arm robot has a relatively large spherical range, comparable to that of a human being, and handling weights in a variety of classes. Paul says: ‘A handling weight of 6 kg and a working range with a radius of 1.40 m will usually be adequate for use in horticulture. Since this robot is also a very common model, the price is relatively low. The number of ‘picks’ (picking up, putting it down and back) is a maximum of 1 to 2 picks per second.’ The Scara robots generally have a lower handling weight, a smaller working range and less height movement, but their advantage is that they are quicker in this smaller working range. Speeds up to 3 picks per second are attainable.


Robot controls Robot arms cannot operate without a brain, and each one of them needs controls that tell each of the movable robot axes what to do. In addition to controlling the robot arm, the controls also communicate with peripheral equipment, such as the gripper, incoming and outgoing conveyor belts and sensors. A robot program (the programming) consists of a movement program and a decision model in the form of a PLC program, which decides, based on sensor output or data from an image recognition system, what movement program must be implemented. ‘Although the logic of the robot programs of the various robot brands is very similar, each one has its own brand-specific programming environment,’ Paul explains. ‘Programming can be done online by means of a teach-in using a program panel, but also offline, whereby the robot world is simulated from a PC in a virtual robot environment and is subsequently programmed. Next, the program is sent directly to the robot via the network or possibly via a conversion by the post processor.’

Image recognition It may be clear that the robot may hold its ground when quick movements are concerned, but whether those movements are utilised effectively is quite a different story. Image recognition is the decisive factor here. According to Paul, ‘Image recognition is used in processing pot plants to select for colour or the number of buds, for example. That selection can often be made fairly easily in a mechanical way, straight forward, with so-called pushers. This is more complex for naturally shaped products, such as chicory, sweet peppers or aubergine,  >>



Articulated arm

Scara staubli

which are not oriented in a fixed position. For example, if a product needs to be packaged lengthwise, the robot must know the grip position as well as the orientation at the moment of pick-up. In simple terms, an image is made, and positions and angles are distilled from the picture of which the x, y and z values as well as the angular displacements are sent to the robot arm. Thus customised software must be supplied for every application, requiring more development hours as the complexity increases. On the other hand, the costs will be lower the more the trick is repeated.’ The picture described above can be made in various ways, depending on the application. Images can be made with relatively conventional and cheap camera technology, comparable to that of a standard photo camera. Paul explains: ‘Cameras can recognise black-white (grey values) or colours and pass on positions in two dimensions utilising conventional camera technology. For robot applications and a variable height of the product present, the need for three-dimensional information will soon arise since the robot needs to know the height of the product for the pick-up position. In that case, several cameras are required. The above-mentioned techniques are within the visible range as far as wavelength is concerned and thus are sensitive to direct sunlight. Multi-spectral image analysis (using infrared or ultraviolet), fluorescence (white T-shirt in disco effect) or X-ray are



Camera recognition

techniques to be used when the chemical composition, the ripeness of a product or the density are of importance. In addition to making the picture using a camera, a three-dimensional image can also be obtained by means of laser triangulation. This can best be compared to a barcode scanner that scans the moving product.’

Gripper Once the product is conveyed within the robot’s range and detected by the cameras, and the image processing software has decided what must be done with it, the product does still have to be picked up and it is precisely at that point where the crux lies for many applications in horticulture. Paul says: ‘The products are not uniform in shape and are also vulnerable when dealt with too roughly. Lacquey in Delft has developed grippers just for manipulation of AGF (potatoes, fruit and vegetables) products by means of patented gripper technology. The fingers in this application fold around the product at a preprogrammed pressure force until they are in position.’ Lacquey originated at Delft University of Applied Sciences in 2009 and is now collaborating with companies such as Rolan Robotics to provide total solutions in the AGF sector. The Lacquey gripper assortment now includes grippers for chicory and cucumbers (oblong products), sweet peppers, potatoes and aubergine (irregularly shaped

products) and apples plus citrus fruit (round products). Three types of grippers are now available for the product groups above.

Safety and miscellaneous issues Not only must a robot do its work rapidly, it also must be safe. Paul: ‘RAB (Benelux Robot Association) has audited suppliers for correct application of the safety conditions in their systems. System builders certified by RAB are permitted to carry the RAB certificate. ‘As you can see,’ Paul continues, ‘quite a few disciplines must be brought together for a properly functioning system. Moreover, the developments in cameras, software and robots are moving right along. The user is interested in a properly functioning system and does not feel the need to do any developing themselves, nor to run the risk involved in the technical aspects of the system. A systems integrator brings together all disciplines and carries the final responsibility for the entire system. To give an example: Rolan Robotics developed the FlexCel especially for the AGF sector. This installation is mobile and therefore easy to move. The sensors and cameras can be integrated in the housing of the installation if so desired. Due to a quick-change system, the robot can work with various grippers and can thus be used for more than one culture.’



The daylight

greenhouse You must have heard about the Fresnel greenhouse at some point: a greenhouse with so-called Fresnel lenses in the greenhouse roof. By now a much bigger greenhouse has been built in Bleiswijk (the Netherlands), in which the Fresnel lens again plays a central role: the daylight greenhouse.

The outer wall immediately lets you see that what is before you is a type of greenhouse quite different from the type we have been used to thus far. In contrast to a standard Venlo greenhouse, the roof is asymmetrical. On the south side, the roof has a gentler slope than that on the north side; therefore there is more surface area on the south side than on the north. If you were to take a stepladder and examine the greenhouse roof from close up, you would find it even stranger than the overall anatomy of the greenhouse. Odd structures are incorporated in the double pane, which an expert might be able to identify as Fresnel lenses.

Fresnel lens You are undoubtedly already familiar with the Fresnel lens, but for the sake of clarity let us go over precisely how the lens works once more. Simply put, a Fresnel lens consists of a lens made up of rings or zones. The various rings are more or less the same thickness, but their shapes differ. The closer the rings lie to the middle of the lens, the slighter the angle with the frontal incidental light. The analogy with a normal convex lens is immediately clarified by Figure 1. The only difference is that the unnecessary material is omitted from the

lens. However, due to the rings, a Fresnel lens is much more subject to deformation than a convex lens. Thus you will not find the Fresnel lens in applications where optic quality is of importance. So where will you find such lenses? In applications where optic performance is subordinate to the importance of weight and dimensions of the lens, for example in overhead projectors, car lights, stage lights and the best known one: lighthouses.

The greenhouse? The greenhouse is one of the applications in which the qualities of the Fresnel lens are theoretically done the most justice. After all, optic performance does not play any role and the glass surfaces in horticulture are so enormous that a convex lens would require a completely different greenhouse structure. A window that normally weighs sixty kilos could easily weigh six hundred kilos. But first a much more basic question: why on earth would you want to have a lens on your greenhouse at all, instead of an absolutely normal window? The answer is obvious: you can use a lens to collect energy and then harvest it. And that is exactly what takes place in the daylight greenhouse. Figure 1: The Fresnel lens on the right

Photo 1: The focus is a line

Source: Wikipedia


Photo 2: The asymmetric daylight greenhouse

Focus The windows on the south side of the daylight greenhouse have double panes with Fresnel lenses placed on the inside. The better known rings were not selected in this case, but rather a straight structure. You could say that the rings were straightened out and laid down under the glass one after another. While a Fresnel lens that consists of rings has a circular focus, the focus in this case is a line (see photo 1). All the direct light that hits one window is thus concentrated on one line: the focus. A collector is installed exactly at the location of that focus, and consists of a gutter containing a black tube with water. The concentrated direct light heats up the water in the tube; the water can then be stored in a water tank. Feije de Zwart works for the Wageningen UR (Wageningen University & Research Centre) as a researcher. He explains, ‘What you do with these solar collectors is capture part of the energy from the direct light. That means you are cooling. In very concrete terms, you capture about twenty percent of the direct solar radiation, which you can store as heat to be used again in winter. The last path is equipped with photovoltaic cells, also called PV cells. The single PV collector, which is also installed in a gutter that runs parallel to the middle path through the entire greenhouse, allows us to collect about 7.5 kWh per square metre. This is thus an interesting structure too.’


Photo 3: Sun on the greenhouse roof

the sun revolves and the focus moves, the collector shifts with it. If there is inadequate sunlight to collect sufficient energy, the collector is parked under the gutter to minimise light loss.’ A thick cloud suddenly moves in front of the sun and a short time later the collector moves towards the gutter. ‘Setting the best time for the collector to move to the side is of course a matter of proper calibration,’ Peter explains. ‘But the most important thing is that now it is possible.’  >>

Parking So you can collect both electricity and heat, depending on which is most interesting for your cultivation. The question remains: how do you ensure that your collector stays precisely in the focus of your Fresnel lenses, since the sun revolves and thus the focus moves with time. Peter Zwinkels works for Technokas and carried out this interesting project together with the Wageningen UR. ‘The collectors can move under the greenhouse roof by means of a number of pull chords. As Photo 4: Cold and hot water supply and discharge



Results of a greenhouse with daylight system regulation Summary after 100 days from 28 March 2011

Hours in focus 543 Heat collection 220 MJ/m2 Estimated electricity production 7.5 kWh/m2 Energy

Average 24-hour temperature Average air humidity Average light intensity at Iglob>500

22.8 °C 78% 378 µmol/(m2 s)

48 MJ/m2 (1.5 m3)

Total heat consumption

Solar radiation 1873 MJ/m2 Direct solar radiation 1114 MJ/m2 (59%) Average outside temperature 14.1 °C

(which amounts to 40% of the daytime period) (which amounts to 20% of the direct solar radiation) (which amounts to 2.42 % of the direct solar radiation)


Number of energy screen hours 436 hours Number of additional shade screen hours 65 hours

Figure 2

Faster growth Clearly the daylight greenhouse is of special interest for cultivation with surplus light, as the direct light is partially captured and the diffuse light is for the cultivation. This diffuse light is particularly of interest for various crops, however, due to the following advantages that have meanwhile been identified: less shade effect, better red/far red ratio and thus more assimilation and production. Furthermore, the daylight greenhouse also has the advantage of the double pane: better insulation and thus less heating in cold periods. The north side of the greenhouse has small air vents. ‘However, they are still a bit large for this cultivation,’ says Feije. ‘Since you can divert a major part of the heat with your collectors, you scarcely require air capacity.’ A glance at the plants, mostly pot plants, shows that they are looking good. Feije explains, ‘Some plants grow quicker than in a regular greenhouse with no diffuse glass. In the case of this Calanthea we are actually talking about forty percent faster growth. We have already increased the EC to fairly high values, but the way it looks this may even be a bit more. We are working together with a number of pot plant growers who have placed their plants here and most of them are very enthusiastic about the results.’ Providing cultivation-specific results is not an issue yet: this will come up in a next study. However, several general but very interesting numbers can be presented, see Figure 2: Results of a greenhouse with a regulated daylight system.

would not have started on it. However, I do have to make a few subtle observations in this regard. This greenhouse is particularly interesting for growing plants that like shade. Of course you need surplus light to make the return attractive. Moreover, you have to look beyond the assumptions we now make with respect to greenhouse construction. We write off a greenhouse in twenty years. So during this period all the investments have to be recovered. However, it is very doubtful whether this is necessary. Look, if you really want to be involved in sustainable culture, it means you are also involved in sustainable construction. Approaching a greenhouse as a shell is perhaps no longer justified over the long term. You can also call a greenhouse a ‘cultivation building’ and continue using it beyond those standard twenty years. The greenhouse structure we used here makes that very possible.’ Of course, but most greenhouses are not replaced because they are worn out, but because something more efficient is available. Won’t this problem come up again in twenty years? ‘That may not be true at all,’ Peter observes. ‘I think that the greenhouse has just about reached the end of the development process. Thus we will no longer be making profits from greenhouse construction itself, but from associated matters.’

more information:

Development process

The Daylight Greenhouse was developed by Bode Project- en Ingenieursbureau BV, in collaboration with the Wageningen UR. Technokas BV, partner of Bode PI BV, built the greenhouse.

And again that annoying but essential question: can you turn it off? Peter responds, ‘If we had any notion that this was not the case, we



Moisture sensor in substrate

The new Decagon MAS1 sensor can accurately and reliably measure moisture in substrate mats at an affordable price.

The most customary methods for measuring the moisture content in substrate is by weighing. Nowadays this is done automatically in all cultivations and the data are usually sent to the climate computer. In theory, weighing is a fairly accurate method of measuring moisture content, but it is not generally representative, as it rarely happens that more than one mat is weighed. And that is unfortunate, as no one can guarantee that the one mat is just as wet as the next. Many horticulturists therefore tend to just add a bit more water than necessary, and even though this is not necessarily bad at all for cultivations, it does cost more money: circulating more water; keeping it clean; and checking it for a variety of values simply costs more. Paul Hofstede of Catec, importer for Decagon in the Benelux, explains why that is a thing of the past. ‘We now have a sensor that can very accurately and reliably measure the moisture in substrate and is still affordable.’

Test The MAS1 sensor consists of two conductors, one of which sends a high-frequency pulse to the other. The sensor is capable of calculating the Volumetric Water Content (VMC), or the moisture percentage in the substrate mat, on the basis of the signal returned. ‘It works very simply,’ finds Paul. ‘You insert the sensor into the mat, and since the signal is analogous with a current of 4 to 20 milliamperes, the signal can be input into the climate computer as it is. The sensor works in all types of substrates, with the exception of coarse coconut fibre, which contains too much air to be able to obtain a reliable measurement.’ A test involving cut hydrangeas that started last year is positive. According to Paul, ‘Growers must get used to the idea of watering on the basis of that sensor, but the way we see it now, it has positive results on production. And the horticulturist now dares to plan his

cultivation activities more tightly. Two sensors were used per watering section in this test, and I would recommend using at least one sensor per watering section.’

Compatible Not only substrate growers, but also open field growers can use the MAS1. Since you can insert the device as far as you want, it is in principle even possible to measure deep under the ground, near the roots. The sensor measurements are accurate from -40 degrees to +50 degrees Celsius. The 5TE is an advanced sensor, also made by Decagon. This sensor measures VMC, EC as well as the temperature at a random depth in substrate and open ground. The difference is not only the price (it is almost twice as expensive), but also the performance. Paul explains, ‘The 5TE emits a digital signal and this is currently not yet compatible with climate computers. Due to the big interest from growers it will not take too much longer, however, before climate computer suppliers will get moving on this. Even though the sensor is more expensive than the MAS1, it also provides valuable extra information. You could also install one MAS1 and one 5TE per watering section.’

More vital Kees Stijger in Honselersdijk is using the MAS1 sensor in his tomato greenhouse. ‘I bought two sensors per watering section after they let me use the system for a while. By now I have about four years of experience with it and I have begun to water much more conscientiously. You can tell from the plants: they look much more vital. The sensors (5TE) are not very cheap, but if you can keep your plants infestation free, you will recover the costs quite quickly.’

More information:



Less expensive

washing and chalking Roof washers are expensive machines not everyone can afford to buy, which is why many Dutch horticulturists have their roofs cleaned by agricultural contractors. Foreign countries do not have such a contractor system and thus growers are left to their own resources. In that case washing the roof of the greenhouse is something that is simply not done.

In the Van der Waay Machinebouw workshop, work on a Top Cleaner greenhouse roof cleaner, one of Van der Waay’s best known machines, is in full swing. However, a very different kind of machine, at first glance smaller than the Top Cleaner, is set up on the experimental greenhouse outside. ‘That’s right,’ says Van der Waay’s Tom Zwanenburg. ‘The SafetyCar is a multi-purpose compact greenhouse roof cleaner and chalker and costs just half of what a Top Cleaner costs.’

Abroad The Safety-Car was designed a long time ago for safely making repairs to greenhouse roofs. The existing structure was used as the basis for the new Safety-Car. ‘Actually, the entire concept was reviewed and reconstructed in an improved manner,’ according to Tom. ‘We knew there was a demand for affordable roof cleaners and chalking machines abroad, but such a machine could also be advantageous in the Netherlands. Considering our expertise in the area of such machines, continuing the development of the new Safety-Car was a logical step.’


Local electrician The Safety-Car is a machine you can build up in modules. As Tom explains, ‘So you can purchase it as your roof washer and add a chalking module or the other way round. We kept the controls very simple to maintain affordability. Look, a Top Cleaner can clean your greenhouse roof automatically, it waits for open air vents and you do not have to keep track of it. That is very nice, but it also costs money. The Safety-Car can do three things: forward, backward and vary speed continuously. That’s it. It means fewer components, shorter installation time, less risk of failure and thus cheaper. It is built in such a way that a local electrician in Poland can repair it if necessary.’

Different roof sizes Another attractive point is the wide variety of uses for the Safety-Car. Tom clarifies, ‘You can work more than one roof size with the same machine. That is very handy for us, because every Safety-Car is in principle identical and therefore we can more or less mass produce them. This is also smart in view of the market abroad, since there are quite a few growers there who have two greenhouses with different roof sizes.’

Remote control The basis of the Safety-Car is an aluminium chassis that runs through the gutter on two electrically driven wheels. Two plastic lined guides are attached to either side of the machine; these guides are supported


by the greenhouse rails. If the roof needs to be cleaned, you attach the brush set on either side of the car; this set consists of interconnected disc brushes driven by an electric motor. The brush set is adjusted to the roof size by adding a disc brush or removing one. A hose can be attached to supply water for the brushes. Another handy feature: the Safety-Car has remote control, so no up-close attention required.

Up-close The Safety-Car can be transformed into a chalking machine by mounting a set of spray booms. It can handle two roofs (again in any size), and in that case it is indeed handy to have up-close attention by someone checking whether the chalk is applied evenly. ‘Something else not to forget,’ Tom adds, ‘is that the Safety-Car can of course also be used for what its basis initially was made for: small maintenance/ repair jobs on the green house roof. You can actually do almost any job from the Safety-Car safely, and that is something that should not be underestimated. The greenhouse gutters can be cleaned with a gutter brush, for example, even when the air vents are open.’ The Safety-Car can be placed on the greenhouse roof with a crane and moved from roof to roof via a platform attached to the service rail. If you do not yet have a service rail, no problem: Van der Waay will install one for you right away.

More information:



New Mobile Sorting system increases horticulturalists clout

In mid-April, WPS Horti Systems (WPS) in De Lier delivered a mobile sorting machine to Van der Valk Patioplant in Naaldwijk. The machine, the first of its kind, is a real success, helping the horticulturist save money on personnel, among other things, and generating uniformity of the culture to benefit the customer.

As far as sorting systems are concerned, a large group of pot plant horticulturists fall between the cracks: too big for one size system, too small for the other. A permanent integrated and expensive sorting system is only profitable after all, if the volumes of plants to be sorted are high enough. Many seasonal pot plant growers are often below those volumes and thus sort their plants by hand, which leads to problems. As Ben van der Valk of Van der Valk Patioplant in Naaldwijk explains it: ‘Sorting is somewhat of a specialised task. You must be able to quickly estimate the height and diameter of a plant. Some people do this better than others and the result is that a person who is good at it is automatically made to do this work too long without breaks. Logically, attention drifts away, which in turn takes its toll on uniformity. Big growers with integrated sorting systems can deliver this uniformity, which the market is also demanding more and more. Add to this that you miss the continuity in production with seasonal cultivation. Result: an expensive sorting machine that is regularly both idle and in the way when changing from one cultivation to the next. This is why we went to Peter van der Knaap of WPS Horti Systems a year ago with the request: “Help us devise a mobile sorting system.” In mid-April of last year the first mobile sorting machine was delivered to us.’


Sorting machine overview.

Peter van der Knaap explains: ‘This system is used to divide the plants into single stems and present them one at a time on a conveyor belt of the sorting machine. This can be done manually or by means of a supply system already in place. The plant first passes a gate on the conveyor belt that measures the height and diameter of the plant. This is done not with expensive camera technology but using much cheaper photocells with special software. We use these measurements to assign the plant a certain value via this special software. When the pot plant has passed the measuring gate with photocells, it continues its way along a number of gutters with more conveyor belts perpendicular to the supply conveyor belt. Based on the measuring data, that plant is then pulled into a certain gutter by a square hook, where plants of exactly the same diameter and length have been assembled. Finally, the sorted plant is moved by the



Arrival at the sorting gutters.

The first plants pass the measuring gate

Square hook pulls the plant into the gutter to join its congeners.

On the way to the pick-up point

discharge conveyor belt to the final pick up point. If a plant is smaller or larger, it is pulled into a different gutter where its ‘congeners’ as far as length and diameter are concerned have been collected.’

made his wishes known can these variables be filled in and a price be quoted. Positive points are: the market of the discerning customer who wants uniformity will be in reach; the time-consuming sorting by expensive personnel is a thing of the past; and one can see at the touch of the button how many plants were sorted in a day. Production per sorting is also displayed. Moreover, the ergonomics were also carefully considered. All actions take place at workbench height and the machine is certainly not a noisemaker. Furthermore, the mobile nature of the sorting machine makes it suitable for a grower to purchase one machine jointly with a fellow grower. Finally: with a minor adjustment, the machine can also be used outdoors.

Continuity The gutters have a certain buffer length. If the pick-up process is too slow because, for example, the attendant has to get new packaging material and the gutter is too short, it will create a mess. The current buffer length guarantees continuity since the sorting machine actually never has to be halted due to minor stagnation in pick-up. To improve the buffer space and thus the continuity even further, one can adjust the machine in such a way that two gutters can jointly process one sorting. Peter continues, ‘Our mobile sorter is suitable for pot plants as well as for conifers and shrubs, etc, thus for growers who work on a seasonal basis and often also at different locations. If you take into consideration how many pot plant growers there are and how many of them use a sorting or delivery system, you are talking about a large group that could benefit from this system.’

Ergonomics It is difficult to say anything about the price of mobile sorting machines because variables such as length, width, the number of gutters and sorting criteria all influence the final price. Only after a grower has

‘We are very happy with it’ Peter says: ‘The machine at Van der Valk Patioplant is suitable for a range of pot sizes from 10 to 13 cm. Sorting pot sizes 9 through 19 is possible with this sorting system, provided you tell us in advance. If after some time you want to move to a totally different pot size, the sorting machine can be converted. However, this is not a simple process, so before assembling the machine, it is important to know what pot size the grower uses.’ Back to Patioplant in Naaldwijk. Ben van der Valk expresses his satisfaction, ‘We have been using the sorting machine for a year now and we are very happy with it.’



The plant as

evaporator We know by now that the traditional method of dehumidification by increasing the heating in the pipes and opening a crack unnecessarily wastes a great deal of energy. The new way of growing teaches the horticulturist to use an active greenhouse climate to the best extent in order to heat as little as possible. This can also be done in another way: the Eco Climate Converter dehumidifies the air and recovers energy from condensation.

While the new way of growing already requires a considerable change in thinking, the idea behind the Eco Climate Converter (ECC) goes much further. Leo Boon, director of Arcazen and importer of the ECC, says: ‘Many people see the plant as an organism that produces a certain product and evaporates a certain amount of water in the process: a bit more when it is warm, a bit less when it is cold. According to the growers, that vapour is more or less a necessary evil, but the developers of the ECC see that in very different light. An evaporator, in this case thus a plant, supplies water vapour that is full of latent energy, for if you condense that vapour against a condenser you can capture and utilise that energy, just as in a cooling system. However, in glass horticulture all that precious water vapour is ventilated from the greenhouse. A pity, because it can be done in quite another way.’

Kitchen salt The ECC works as follows: the relatively moist greenhouse air (which the ECC is intended to dehumidify) is suctioned up in the greenhouse. The air subsequently passes a laminated packet through which a lithium chloride (LiCl) solution circulates. LiCl is a so-called hygroscopic substance, meaning that it has the natural property of absorbing water from the air around it. A very well known (slightly) hygroscopic substance is sodium chloride: kitchen salt. Without any rice grains in your salt jar, you run the risk that the kitchen salt will lump together because it absorbs moisture from the surrounding air. For exactly the same reason, you pour kitchen salt on your table cloth after spilling a glass of wine. Back to the ECC. The moisture in the greenhouse air condenses against the salt solution and the heat released in the process is absorbed by the solution, thereby increasing its temperature and volume. The water and salt solution mixture is pumped to the regenerator via a heat exchanger. The salt water mixture is heated to above 80 degrees Celsius in the heat exchanger and then spread across a laminated packet in the regenerator. Since LiCl has a boiling point far in excess of one thousand degrees, the salt solution is left behind and only the water is evaporated from the salt. Following evaporation, the pure LiCl

is returned to the greenhouse vapour collector. The water evaporated from the LiCl is condensed via a condensation unit in the regenerator, which condensation water is hot and will release its energy to the greenhouse air via a heat exchanger. Another option is to store the superfluous heat in an aquifer or a different kind of heat buffer. Another advantage of using an aquifer is that the cold water can be used to cool down the salt solution further in order to capture more condensation. The cooled condensation water can be discharged or used for other applications. In brief, the evaporation energy locked in the water vapour in the greenhouse air is recovered, resulting in lower relative humidity (RH) and energy recovery, or actual reuse of energy. An external boiler with a capacity of up to 40 kW is required for heating and evaporating the LiCl solution. The total air output of the ECC is 9,000 cubic metres per hour. A built-in heater block provides the option of heating the air even more and thus reducing the RH even further, but would be at the expense of the heat recovery.

Savings Marnix ten Kortenaar, physical chemist for Arcazen explains, ‘You have to figure that the heat you introduce with the boiler in the ECC is completely recovered and blown back into the greenhouse as hot air. This dehumidifies the air by ten to twenty-five litres per hour at an RH of 75 to 90 percent. Of course the ECC does use electric energy, which you have to calculate at approximately 1.7 kW. The total energy savings, in comparison to a conventional growing method in which the heating pipe does the work, is about 60 percent.’ The impressive numbers Leo comes up with are from an Israeli study by the Agam firm, which is also the inventor of the Agam system. The Agam system is identical to the ECC and sixty units have been sold by now to various companies round the world. A considerable share of those companies operates in glass horticulture. Various systems have meanwhile also been delivered in the Netherlands. Moreover, the Wageningen UR (Wageningen University & Research Centre) has concluded a preliminary study and a follow-up study was begun on the possibilities of the ECC. Says Marnix, ‘This study actually reads: yes, the


ECC is an interesting piece of equipment that will certainly be able to prove its usefulness in glass horticulture. The next step is to investigate how the ECC could be implemented in the greenhouse the best way.’ Leo continues, ‘Not only does the efficient dehumidification and energy savings make the ECC interesting to entrepreneurs. The air that is extracted is a lot cleaner and this gives aerobic pathogens (of which there are many) less of a chance to proliferate, as pathogens that come into contact with the LiCl are desiccated and therefore die. This is a very effective way to keep your greenhouse air clean and thus also of special interest for organic cultivation.’ How much does the machine actually cost and how many do you need? Leo says, ‘The machine costs EUR 25,000; an ECC unit can handle 1,000 to 1,500 m2 of greenhouse surface area, depending on the evaporation per square metre. The ECC also qualifies for subsidies.’

Realistic? This must be said: the ECC is completely new and the underlying principles are unprecedented in glass horticulture. What do climate experts actually think of it? Jan Voogt, researcher at Hoogendoorn Growth Management comments, ‘I must say I am enthusiastic about the principle of discharging moisture via a hygroscopic substance. This is a good idea in theory. I also find it interesting to think of the plant as an evaporator and that you capture energy released in condensation. However, I do have a number of reservations concerning how such a machine would have to be designed for large scale horticulture. First of all, you must budget at least five to six machines for a one-hectare greenhouse to obtain even distribution of dehumidification at sufficient


capacity due to the limited reach of 80 metres and 9,000 cubic metres. This will already put you at about 15 euros per m2, meaning a fairly expensive system. Plus, as with greenhouse air recirculating systems, you must take into account uneven temperature distribution, differences in air speed, cold spells as well as high energy consumption because you have to move air over great distances. Recovery of water and energy thus has quite a number of disadvantages and also low return. The situation in Israel is quite different, as you have a desert climate with cold nights, and water is much more costly than it is here. Under those circumstances, being able to recover condensation is a big advantage.’ ‘Another issue is the claimed sixty percent savings. I believe it, but the reference point, which is stated as heating and drying out with the heating pipe is no longer realistic. You should actually compare the system with the new growing method in which air is dehumidified by blowing in air from the outside.’ Still, it does not mean that the ECC is not useful in the Netherlands. Jan continues, ‘I consider dehumidification via a salt solution as a possible addition to a system of blowing in air from the outside and good vertical temperature distribution. The principles of the ECC may be incorporated in different installations.’ Leo adds, ‘We are now working with a large tomato grower to see if we can install a larger unit centrally in the greenhouse and take in and exhaust air via a heating pipe system in the greenhouse. Heating pipes under the gutter are becoming more common of course.’

More information?



Faster and more

homogeneous The Bercomex Furora was first presented at the 2010 Hortifair, and since then several dozen machines have been sold. Van Veen Alstroemeria has had the Furora in operation for more than a year and a half: high time to have a peek behind the scenes.

According to Bas Goede of Bercomex, there are two reasons to purchase a Furora: ‘First, the improvement in the quality of your final product. You want to be able to offer a better and above all more homogeneous product. The second reason is to increase the capacity per person. Manual sorting tallies up to a maximum of eight hundred stems per person per hour. A sorting machine puts this at approximately fifteen hundred, but the Furora will sort as many as two thousand five hundred stems per person per hour. The difference in speed between Furora and other sorting machines is in dividing the stems into single units, which the Furora can do extremely rapidly.’

Modules The most characteristic quality of the Furora is undoubtedly the hanging transport of the stems. They pass at an unbelievably high speed. ‘And these stems are hanging for a good reason,’ explains Bas. ‘Vertical transport ensures that the flower is not damaged. In addition, vertical transport makes it possible to evaluate the flower more carefully than if it is lying on a belt.’ The flowers can be evaluated in many ways. ‘It is a machine that can be built up from and expanded using modules,’ Bas begins. ‘The revolving part forms the base of the machine, but you can link a variety of modules to the platform, for example different measuring instruments, >>

The bundles are placed here and the stems are put at roughly the same height.

Before the stems actually enter the machine, they pass through visual inspection one time. Very bent stems are removed here.



Stems change position: the black guide string moves them quickly into a hanging position, without damaging them.

To facilitate sorting for the camera system, the distance between the stems is doubled. The row of stems is divided into two rows.

The stems are divided into single units and then picked up by a gripper. Any stems not sorted further on in the process go an extra round and when they come back the gripper is already busy. The computer calculates when the stem can be picked up by which specific gripper.


such as an IR camera, a colour camera, an X-ray instrument, a weighing instrument, etc. You can also add various modules to handle processing, such as a saw or a defoliator. Thus you can, depending on your modules, sort by length, weight, bud maturity, number of buds and actually all variables that could be of significance for your specific culture. The brilliant thing is that the Furora can also process various sortings at the same time. So you do not have to run all 72 centimetre bundles. Instead, everything can be intermixed and at the end of the run you still have all those neatly sorted bundles on your belt.’ 

Recovery Fedor van Veen is very happy with the machine’s performance: ‘Initially, the quality improvement of my final product was the most important


reason for purchasing the machine. However, it is difficult to express that variable in money, while it is easy to do so in labour savings. Thus if I only include those savings, I will have recovered the costs of the machine in two to five years, which is very quick for such an expensive machine. Let me be quick to add that that higher quality was immediately noticeable. Buyers were calling me to ask how I was suddenly able to deliver such tight bundles.’ There are also points for improvement. Fedor says: ‘The percentage of stems that fall is still a bit high and this number needs to come down. We are now working on a fairly simple mechanical solution, which I suspect will work well. Of course such a machine also has consequences for your cultivation. You have to pay more attention to the lengths in the garden, but if your people are good, it is no problem.’

A camera and a mirror analyse and record the length and the curvature of the stem.

Behind closed doors: the X-ray unit. This is where the thickness of the stem and the number of buds are measured. Radiation measured outside the housing is zero.

The sawing unit cuts every stem to the right length. Despite the fact that the space between two individual stems is a mere twenty centimetres and the speed is fairly rapid, the gripper jumps to the correct height every time superfast to have the stem cut to the right length.



In the bundle formation stage, five bundles can be formed and put on the belt simultaneously.

On the basis of a number LEDs next to the belt, the packaging machine receives information on the type of sorting, since the Furora can run various sortings simultaneously.

Tight bundles: buyers notice it, but it is difficult to express this in recovery time.



Nanotechnology improves light transmission Van Looveren in Oelegem, Belgium, has been supplying greenhouse horticulture with the most diversified types of glass for 70 years. Hortifuse AR is the latest descendent in the assortment of diffuse greenhouse roof glass that has a spectacular anti reflective effect due to nanotechnology.

Diffuse glass is in the focus of interest. Of course the light permeability of a diffuse greenhouse roof is considerably less than its crystal-clear brother, but the advantage is in the diffusion of the PAR (Photosynthetical Active Radiation) light, so necessary for the plant, the wavelength of which is between 400 and 700 nanometres. Diffuse PAR light is distributed better throughout the greenhouse, and also amidst the culture, so the culture experiences balanced growth with no plant stress.

Shop window Yves Milonas discusses it: ‘Diffuse glass has a so-called HAZE factor. If the incident light deviates 2.5 degrees or more from the straight incident light, we use the term HAZE factor. Suppose, for instance, that 30 percent of the incident light does not deviate as much as 2.5 degrees and 70 percent does. In that case we use the term 70% Haze, whether that light diffusion deviates 2.5 degrees or let’s say 40 degrees from the incident light. It makes no difference. To date, there is as yet no real scientific support for which HAZE factor generates the most suitable diffuse light for the culture.

Originally it was thought that the HAZE factor should be 30. Thus 30 percent of the incident light gradually deviates more than 2.5 degrees from the incident light. Silke Hemming of Wageningen University & Research Centre (Wageningen UR) explained to me that this could also be HAZE factor 50, just to show that science cannot provide an unambiguous answer to this either. What is clear, however, is that the PAR light transmission through the diffusing greenhouse roof is reduced spectacularly. If you start treating a clear piece of glass with an original PAR light transmission of 90.5 percent, for example, the light transmission is reduced by 50% HAZE to about 81-82%. This does not seem like much, but it is really quite a high amount over a large greenhouse roof. And so we wondered if we could do anything about the light reflection of that diffuse glass to increase the light permeability, as reflection reduces the light yield in the greenhouse. Of course anti reflection treatment of glass is nothing new. A standard shop window is usually anti reflective because you want to have a good view of the items in the display. Anti reflection is expensive though, especially if you are talking about surface areas such as those in large-scale greenhouse horticulture. An adequate good immersion coating, whereby the glass is immersed in an anti-reflective coating, adds EUR 10 to the price per m2. Moreover, you have to temper the glass afterwards or else the immersion coating will start losing its effect after a few years due to aggressive environmental factors. Maximum light permeability with an anti-reflective immersion coating is 95 percent, so you must try to tackle the higher cost price of diffuse glass plus the anti-coating by increasing the light transmission of the PAR light to above that 95 percent, whereby you also increase the yield with diffuse light. That was our starting point when developing a new anti-reflection technology.’

Average wavelength So in collaboration with a European glass supplier Van Looveren went looking for a different way of anti-reflection. In that search, they deviated from the path of coating, i.e. the application of an


anti-reflection layer on the glass surface. Their thoughts gradually shifted to treating the glass itself. And in the back of their minds they held the thought that this new method was not going to be permitted to be more expensive than the time-honoured immersion method. The way to treat glass instead of coating it turned out to be possible using nanotechnology. Yves explains: ‘The glass used the most is float glass. In production, one allows the glass to flow as a liquid into a tin bath. Just like mercury, tin has a high density: you cannot compress it. The liquid hot glass therefore floats on the tin. This gives it the tight smooth surface. Next, we start follow-up treatment of the glass with nanotechnology in such a way that the surface structure changes. A surface that is slightly rougher, although this is still invisible to the eye, reflects less than a smooth surface. After treatment, the PAR light strikes the glass in such a way that it is not reflected. PAR light has a wavelength between 400 and 700 nm. We take the average of that and end up at 550 nm. Follow-up treatment with this wavelength has the best anti-reflection result.’


And according to Yves those results are worth mentioning. For example, clear horticulture glass has a light permeability of 90.5. The anti-reflection effect applied by nanotechnology increases this light transmission to 97-98 percent. When you go from clear to diffuse glass, light transmission falls to 81-82 percent. With the nano treatment (and thus blocking reflection) one can count on the same percentage increase of the light transmission in diffuse glass, at a percentage of 8%. This puts the light permeability of diffuse glass at an unprecedented 89-90 percent. The fact that the glass treated with nanotechnology costs the same as glass with an immersion coating, while the latter must moreover be tempered to retain the coating, is of course a pleasant side effect.

But there is more Yves says: ‘A horticulturist wants to control the variables. As glass suppliers, we can in turn play with those light frequencies. Suppose that science discovers that a certain culture grows better with a little more light of a certain frequency. That being the case, we can treat this glass with nanotechnology in such a way that this specific light frequency is allowed to pass at a higher rate than another light frequency. This is already happening now with UV light. UV light has a wavelength of less than 400 nm. The glass we supply to Lolo Rosso lettuce growers, for example, has a higher UV permeability. This turns the lettuce red and gives it a different flavour than the regular head of lettuce. It could very well be that something similar is at play in the PAR light for certain crops that are sensitive to a certain light frequency between 400 and 700 nm. But we haven’t come that far yet. However, we have already managed to get to the point where the diffuse light, in combination with the new nano anti reflection treatment, gives a diffuse greenhouse roof an unprecedented light transmission.’

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‘a horticultural partnership’

The Greenport Holland International Foundation (GHI) is an independent organisation, set up by Greenport Holland and the Dutch horticultural Industry. GHI’s unique strength lies in the combination of experienced and specialised businesses, governmental organisations and knowledge institutes, a professional organisation and a global network.

GHI’s mission is to enhance the quality of international horticulture through successful local projects. By bringing together the strengths, expertise and experience of the leading Dutch companies and the local circumstances and parties, GHI is able to complete major, complex, multidisciplinary cluster projects in the horticulture sector in international markets. GHI is the ideal single-source partner for implementing ambitious horticultural projects anywhere in the world

Projects clearly signify large projects, as GHI cannot refer to one single technical supplier or greenhouse-producer for example. The Dutch horticulture sector is regarded worldwide as an industry leader in added value, knowledge and innovation, marketshare export, productivity and sustainability. The Dutch network of many innovative companies, the excellent knowledge model of the Dutch Agribusiness and the close cooperation with governamental organisations, benefits our partners to get the best adapted solutions.

Type of projects GHI wants to be the contactpartner for horticulture cluster projects abroad. Horticultre refers to all covered and uncovered cultivation of (horticulre) fruit, vegetables and ornamental plant cultivaion products.

Partners Greenport Holland International’s activities focus on three potential partners in existing and new horticulture areas all over the world.


For national governments that prioritise sustainability and guaranteed food supply , that embrace ‘local for local’ concepts and want to successfully solve the food supply problem in major cities, GHI is the ideal partner. For investors that see opportunities for modern, large-scale horticulture projects, GHI offers chain-focused solutions. The future lies in joint horticulture projects. GHI brings together the expertise and knowledge required to make those projects a success. For local horticulture in all areas of the world, GHI offers modernisation of and increased professionalism in domestic production and distribution; the road to achieving greater turnover. GHI also offers solutions for

issues of topical interest: growing food using less water and less energy, improving post-harvest operations and professionalizing the market.

GHI Organisation GHI was founded with support from the Dutch government. Over thirty organisations, varying from knowledge and research institutions to greenhouse construction and installation companies, financed the project and have joined under their own initiative. Reinforcement of the international position of Dutch horticulture is also a goal of these companies. All participating organisations have played a role in founding GHI. Most of the organisations are also represented in one of GHI’s committees, which are set up to give a tangible interpretation to its consultancy function.

GE Energy GE Energy is one of the thirty founders of GHI. The GE Energy’s Gas Engines division is a manufacturer of gas engines, generator sets, combined heat and power (CHP) modules, Organic Rankine Cycle (ORC) systems and auxiliaries. With a legacy of technological innovation across three product lines, including Jenbacher gas engines, Waukesha gas engines and Heat Recovery Solutions technology, GE’s gas engines set the industry standard for flexible fuel capability, low emissions and efficiency. Engines can operate not only on natural gas, but on a broad range of alternative gases such as biogas, landfill gas, coal mine gas, flare gas and sewage gas featuring impressive fuel flexibility. Solutions include combined heat and power, gas compression, and waste heat-to-electricity generation in industries ranging from oil & gas and agriculture and are deployed in over 80 countries. With this ability to provide diverse power output, ranging from 0.12 – 9.5 MW, and eight products and solutions qualified

through the GE ecomagination program, GE’s Gas Engines business offers specialized local power solutions to deliver cleaner, more efficient, affordable energy around the world. GE’s Gas Engines business has its headquarters, main production facilities, and more than 1,400 of its 2,600 worldwide employees located in Jenbach, Austria. GE’s Jenbacher gas engines also operates two regional gas engine assembly facilities in Hangzhou, China, and Veresegyház, Hungary. The Waukesha gas engines facility is located in Waukesha, Wisconsin, and the Heat Recovery Solutions facility is in Stuart, Florida. Participation in GHI is important for GE Energy. GHI brings government, business and knowledge closer together in projects, combining each others expertise and networks. A huge synergy to the members and the international partners abroad!


Reduce water usage by 90% Use of stonewool substrate

On average, the cultivation of one kilo of field-grown tomatoes requires some 100 litres of water. However, if the plants are cultivated on stonewool substrate, with recirculating irrigation water, only ten litres of water are used for every kilo of tomatoes. Moreover, the whole growing process is managed more easily. A highly efficient method, therefore.

In many countries, including Mexico, the Netherlands and Canada, stonewool substrate is widely used in horticulture. However, in countries with a more recent horticultural history, such as many African and Asian countries, substrate is not often used as a growing medium. Considering the increasing attention to efficiency in water usage and the focus on optimum production results, these countries are now also showing increasing interest in stonewool substrates.

Water and substrate The increasing scarcity of high-quality water is forcing horticulturists around the world to use water more efficiently. A carefully controlled water supply, in combination with efficient water usage, is a necessary precondition for good growing results. Stonewool substrate offers the possibility to handle water and fertiliser very

sparingly. Fertiliser can be added very well to systems in which water is recirculated. As opposed to many other substrates, the water in stonewool substrate is fully and easily available to the plant. Therefore, the water is not bound to the material, which facilitates management and control. One of the major manufacturers of stonewool substrate is Saint-Gobain Cultilene. In collaboration with horticulturists, this company is currently carrying out tests in countries that only rarely use substrates (for example in Africa and Asia). The tests are carried out in collaboration with Dutch horticultural advisors. The stonewool slabs are measured horizontally, which means that across the full length, as well as at different heights within the slabs, the temperature, the amount of moisture, and the EC are monitored. The practical experience and knowledge of stonewool-substrate supplier Cultilene concerning irrigation strategies and modern substrate


Glass by Cultilene Cultilene is a subsidiary of Saint Gobain. This French superpower in the building industry is among other things known for its glass production. From the beginning of 2012 Cultilene supplies the innovative glass products by the parent company to the horticultural market. These concern high-quality glass products, such as diffuse glass.

systems contribute to the optimum use of water and substrate. In addition to the environmental advantages, which focus on water savings and the frugal use (and prevention of leaking away) of fertiliser, horticulturists can look forward to other, considerable benefits. For example, horticulture is much less exposed to external factors, such as soil condition and soil-borne diseases. As a result, there will be considerable savings on plant protection agents. In addition, fertilisation is managed more easily.

Material The substrate is made of basalt, which is a volcanic type of rock. By reheating the basalt, it is melted down in a natural way to form a liquid material. This material is put into large centrifuges where long fibres are formed. These fibres are compressed into stonewool plates. By varying the density and composition of the fibres, Cultilene has assigned special features to the substrate. Cultilene’s product range comprises substrate products with a varying water-bearing capacity. By selecting from the different water buffers, an optimum match can be made between the substrate and the specific growing conditions (such as the capacity of the irrigation system).

company’s own production sites, but also, and especially, to ensure the recycling of manufactured materials after use. Initially, the recycling process comprises the separation of different materials. Next, these materials are channelled towards their own specific type of reuse. For example, the recycled stonewool granulate can be processed into raw materials for the production of bricks for the building industry, or as a soil improvement agent for the potting compost industry. To obtain the best recycling solution, local options must be investigated in order to avoid extra transport movements. That is why there are continually international project studies in the area of recycling.

Alternative substrates Next to stonewool, Cultilene’s R&D department is also actively searching for alternative substrates to be used – both organic and inorganic types. These alternatives do not, as yet, offer the required quality concerning, for example, the homogeneousness of the material; however, hopeful steps have already been taken. Because of the innovative nature of Cultilene, the company is focussing on the searching for new substrates and substrate systems, and the optimisation of the current ones.

Product types Stonewool is particularly supplied in the form of plugs and blocks for the growing of young plants and in the form of slabs for vegetable cultivation and the cultivation of ornamental plants. In vegetable cultivation, stonewool is especially used for the growing of cucumbers, tomatoes, aubergines, and peppers. Four different types of slabs have been developed for these purposes; each with its own waterbearing capacity. In addition, there are various products for the cultivation of ornamental plants, such as roses and gerberas. Next to the standard products, it is not uncommon for Cultilene to develop customised products according to the specific wishes of horticulturists.

High Tech and Innovative


For the development of its products, Cultilene is fortunate to be able to make use of its large parent company Saint Gobain. Including an R&D team numbering 3500 people, who are also contributing to Cultilene’s innovations. The stonewool products by Cultilene meet very high standards, which is demonstrated, among other things, by the product ‘CultiWall’. This system is used to create green wall decorations and even complete façade coverings. The mission of Cultilene is to provide innovative solutions that contribute to the optimisation of water management and energy consumption so as to enable growers to improve the quality of their processes and to save on fertilizers, water and energy, and to contribute to sustainable horticulture.

To promote sustainable development, Cultilene is continually paying much attention to the recycling of raw materials. Not just at the

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Growing tomatoes, but in a different way The new section in the back of Demokwekerij Westland, a demonstration plant breeding station, is equipped with a new growing system for tomatoes. The plants are grown with no substrate, in gutters that can be height adjusted. This new revolutionary growing method produces more per square metre and saves labour.

The test took an entirely new tack here. The idea of growing tomatoes without substrate is already fairly progressive, but we added another set of new ideas, so it can easily be called revolutionary cultivation.

Circulation The best way to describe this cultivation system is by starting at the basis: the cultivation gutter. These gutters are suspended in the greenhouse from a hoisting installation that enables us to stagger the gutters in height, alternating them with mature plants and young plants. The distance between the individual gutters growing the same plants is 1.60 m and the gutter holds no substrate. Peet van Adrichem explains: ‘We grow plants in a drip system, because that way the plant can take exactly what it needs and when it needs it. The gutters are slanted in two ways: sloping a bit to the right and also towards the end of the gutter. Fresh water is dripped near each plant straight across the gutter. The water flows to the end of the gutter via the drainage channel, and there it is collected and pumped to the central water unit. In this unit the water is decontaminated, checked for pH and EC and prepared for reentering the cycle. For now there is still a narrow strip of cloth in the gutter to retain a bit of water, but in the long term we will replace this with a compostable alternative. If we can implement this, we can rip the entire thing from the gutter at the end of cultivation and throw it on the compost heap. We can circulate water continuously now, but we have already discovered that semi-continuous also works well. The water flows along the roots half the time, and the rest of the time it doesn’t, thereby reducing energy consumption.’


Hoisting installation for cultivation gutters

The cultivation starts with a young plant in such a gutter with dripping water. As always, the plant starts producing leaves and clusters and these start ripening from the bottom up. At the eighth cluster the top is cut and the plant will grow no higher. As soon as the sixth cluster starts flowering, a sucker is taken and used for new cultivation. The new plants end up at the top of the greenhouse, roughly at  >>





‘With a view to the use of a harvesting robot, it is smart to keep the variation amongst the plants to a minimum’

the height of the top of the first cultivation. This gutter is also suspended from steel wire, but much higher. As soon as the eighth and last cluster of the first cultivation can be picked, the first cluster of the new cultivation starts to ripen. The old growth is thrown on the compost pile and the new cultivation is subsequently lowered to the level where the old cultivation was suspended. Thus the circle is completed. The advantage is that the greenhouse always has vigorous plants in it. ‘The suckers for the second cultivation are still sent to Wageningen University & Research Centre (Wageningen UR) for rooting and come back to us with small root balls, but soon we will be able to do this ourselves, after making a few adaptations. We have also experimented with growing plants from seed for the new cultivation. The wonderful thing about seeding is that you start very small and thus the plant produces plenty of roots before extending and spreading out. The problem with suckers is that they start shooting up too soon, without a good root ball. You have to try to find a good balance here.’ The near future will prove which concept is the better one.

LAI Thus there will be a gutter diagonally above the old planting during the last stage of new cultivation. Doesn’t this actually block too much light? ‘No,’ says Peet, ‘in a normal situation the top with the matching leaf cover blocks some of the light from the clusters, which is actually a good thing. You could say that the young, new cultivation forms the top for the old cultivation. Incidentally, we are also taking regular measurements and we know exactly what needs to be done on the basis of the LAI (Leaf Area Index). For example, if there is a lot of sun, the new cultivation can be moved up a bit to capture some light, while the gutter can be lowered if there is little light. We can play very nicely with this.’ In fact, the LAI is optimal the entire year. Harvesting can be done while standing on the ground as usual, all within reach up to the sixth cluster. A pipe rail trolley is required above that. Even though this does take a bit more time than in a regular greenhouse where one can always harvest while standing


on the ground, it results in much higher labour savings in other areas. As Peet says, ‘We do not have to pick any leaves, because here the plants just grow straight up and therefore you have no thick tangle of stems where leaf is a potential hazard. That saves a great deal of time. Another thing that saves time is not having to lower the tomatoes.’ ‘For that matter, we are also already looking for a way to harvest all clusters while standing on the ground,’ Pete continues. ‘This could easily be done by first laying the plant flat, letting it grow towards the side for a stretch, and only then allowing it to grow vertically.’ And fewer clusters, is that an option? ‘Eight clusters is actually the optimum number for such a plant and for the production, so we shouldn’t change that,’ Peet observes. Incidentally, there is another advantage in the plants growing straight up, which is that this makes the distance between the tomatoes much more even than between plants that continue to grow up to thirty clusters. With a view to the use of a harvesting robot, it is smart to keep the variation amongst the plants to a minimum.

Profit The results make it all worthwhile. Peet explains, ‘I expect us to increase production ten to twenty percent by utilising our space better, really growing year round, and due to the fact that the plants just grow fantastically well on water. Summer crops are nice, but your profits are of course really made in winter. While everyone is busy changing crops, you are still producing and picking a full load as usual. Then it suddenly becomes much more attractive,’ says Peet. Even though the experiment is done in a standard greenhouse, some subtle adjustments are required. Peet continues, ‘We were unable to do this experiment until after we expanded. Cultivating two stages at once does require a certain height. We have six metres here and that is sufficient.’ In addition, there is the rail system against the outer wall for hoisting operations. One rail is installed for each gutter in order to link them together. ‘It looks like a simple system, but someone


had to think it up,’ Peet laughs. ‘The steel wires run around that pipe and the motors turn the pipe. Gutters suspended from steel wires would initially make you think of pulleys, but those are too sensitive to failure. In this system nothing can in fact go wrong.’ The bar is fitted with a rail in between on which the second screen can run. The first screen runs along the top runner of the bar and the bottom of the bar gets too close to the hoisting system. ‘You don’t want your screen to suddenly be grabbed by the tackle system,’ Peet says, ‘and you also still have to hang your lights. ‘When growing year round, lights are naturally not a luxury. Above the tomatoes in the drip system hang fixtures producing 15,000 lux in anticipation of the dark days.’

Parties involved Peet van Adrichem lists the contributors: ‘Quite a few parties were involved in this experiment: Wageningen UR, Groen Agro Control, Priva, Metazet FormFlex, Demokwekerij Westland, Inno Agro and grower Jos Kouwenhoven. This project was co-financed by the European Regional Development Fund of the European Commission as part of the Zuid Holland Cluster Project subsidy scheme under the Opportunities for West Operational Programme.’




pipe rail trolley Berg Product has been setting the tone as market leader for crop handling trolleys, spray trolleys, transport trolleys, up to complete harvesting systems for vegetables, flowers and pot plants for many years now. The EasyKit pipe rail trolley was added to this product list in January 2011. Originally intended for growers in low wage countries, the EasyKit pipe rail trolley is managing to also find its way to the Dutch growers.

Van Kester-Weijs, a tomato nursery specialised in snack tomatoes, decided at the end of the growing season that a few additional pipe rail trolleys would be very welcome. As manager Samir Bouzalmad says, ‘Hydraulic pipe rail trolleys are really rather costly machines. We learned via Steenks Services that Berg Product offers an alternative in the form of a pipe rail trolley with a manually adjustable tray height. Of course this is somewhat more labour intensive than its hydraulic brother, but it does make the EasyKit much cheaper. If you constantly have to adjust the height of your work tray on a path, you cannot get away from using a hydraulic system. But in our culture, for example when pruning or culling, you actually work fairly constantly at the same height. You may have to adjust that height once every 2 to 3 days. And in that case, the EasyKit is the perfect solution. Inexpensive, anyone can operate it, and it is economical. Since the hydraulic pipe rail trolley is much heavier, a charged battery lasts 2 days, while the battery of the much lighter EasyKit lasts 4 days.’ Samir pulls an EasyKit from a path to illustrate his point. The trolley has clear usage marks and that is a good sign, as this indicates intensive use.

Operation Two men are required to adjust the tray. They do this by first pulling together two locking handles of the securing and stabiliser rods that run at an angle from underneath the tray to the uprights. These two locking handles can be operated with one hand. Once the securing and stabiliser rods have been disconnected, they hang straight down from the platform. The tray, with its locking handles directly beneath it, is disconnected in the same way and can be adjusted. Once the right height has been decided on, the locking handles are released and a spring shoots them into the round openings of the uprights. The


securing and stabiliser rods are anchored the same way. After that, the EasyKit is stabilised against back and forth longitudinal movements. Stabilisation against back and forth movements in transverse direction is provided by the adjustable steps. These are caught in a triangular profile in the uprights specially designed for that purpose. Thus the steps have a double function: stairs and stabiliser.

User friendliness The control panel is installed on the floor of the tray itself and is very simple: a switch to set the direction of movement (backward or forward); a rotary switch to regulate the speed; and finally an emergency stop button. Once the direction of movement and speed have been programmed, the eclectic motor can be switched on and off with a foot pedal in the middle of the work tray. The transmission from the motor to the drive wheels is by chain drive. Samir says, ‘We started using this trolley last season and we like it well because it is exactly the combination of what you need if you do not have to change heights too often. And its simplicity combined with the clear operating symbols on the trolley itself makes operating it much easier, and thus takes less time to explain to the many Polish people who work here, for example. In brief, we are enthusiastic about this trolley and we currently have three of them in use.’

Low budget According to Hans Fakkert, Berg Product salesman, ‘There were a number of reasons why we started to develop this trolley ourselves. First of all, it is easy for us to produce the EasyKit and send it as a kit. Due to its simplicity, it is easy to stack as a kit and thus you can fill an export container very easily and very economically with


these EasyKits. In addition, it is a low budget pipe rail trolley, as we call it. The price is about 60 percent lower than a hydraulic pipe rail trolley, the price of which you can only recover if the work involves regularly readjusting the height, as the cost of wages will thereby start increasing. In low wage countries people aren’t losing any sleep because of the cost of wages, but they do worry about the purchase price of a more expensive hydraulic pipe rail trolley. This is one of the reasons why they care less about very advanced technology there, as machines must be cheap and functional. Moreover, the hydraulic pipe rail trolleys are much more difficult to stack and thus also more expensive to transport to the user. All these types of factors resulted in EasyKit finding its way to Poland, Turkey and Mexico, for instance. And the Dutch growers whose tray level is fairly constant during various cultivation operations, such as cucumber cultivation, are also starting to discover the EasyKit.’

From prototype to production The power of simplicity certainly applies to the EasyKit, but the road to that smart technical simplicity was not simple. Hans explains, ‘We did spend quite some time on development. It all looks very simple, but by the time you have invented something that is inexpensive to buy, functional, easy to operate, inexpensive as far as export transport costs are concerned and complying with the Pipe Trolley Policy Rule standard, another year has gone by. We finally presented the EasyKit at the HortiFair in October 2010. We started production in December of that year.’ EasyKit was the latest addition to Berg Product’s already sizable product range. EasyKit’s flying start makes us surmise that there is a great future in store for this pipe rail trolley.



Building profitable

greenhouses Bram Vanthoor received his PhD from Wageningen UR (University & Research Centre) in 2010. His research entailed developing a method to design profitable greenhouses under various climatological and economic conditions. Bram relates what exactly the content of his thesis is.

‘You come across different types of greenhouses all over the world. These differences are due to local conditions such as the weather, the economy, social conditions, statutory requirements and the availability of resources such as water, energy and CO2. Because of the fact that there are also many different design components (e.g. structures, greenhouse roofs, heating systems and cooling systems) available, designing greenhouses is very difficult. This is why there are greenhouse designs that are not well adapted to the local conditions, and therefore they do not render the best financial result. A systematic approach that uses physical, biological and economic models is a promising method for designing greenhouses. This approach may make it possible to adapt greenhouses better to local conditions and to point out improvements for existing greenhouses.’ ‘The purpose of my thesis was to develop a method for generating greenhouse designs suitable for the local climate and economic conditions. This method must function for the various conditions one encounters worldwide. Since greenhouse design is a complicated optimisation problem, we developed a design method that uses computer models. This method maximises the financial result of the greenhouse by adapting it to the local conditions. The financial result of a greenhouse is the difference between the economic yield of tomatoes, for example, and the variable and fixed costs of the greenhouse. In the study, we focused on tomatoes as a crop, and the climate and economic conditions were selected as preconditions. The design problem is also reduced to components that have an effect on the greenhouse climate. A greenhouse climate model was developed to predict the climate in the greenhouse (air temperature, humidity and the CO2 concentration in the air as well as the plant temperature). The following variables are included in the model: the outside climate (e.g. incident sunlight, temperature, humidity, wind velocity and CO2 concentration), the climate control, the greenhouse design and the crop. In order to be able to design greenhouses for different climates, the model contained generic greenhouse design components. The predicted

climate was compared with the measured climate for four different greenhouses and three different climates: a moderate sea climate, a Mediterranean climate and a semi-desert climate. The model predicted the greenhouse climate accurately for all these cases. The deviation between the simulations and the measurements was less than 10% in more than 78% of the cases.’ ‘My thesis describes the model that predicts the tomato yield depending on the plant temperature, the photosynthetic active radiation (PAR, the part of the sunlight that the plant uses for growth) and the CO2 concentration in the greenhouse air (a higher CO2 concentration stimulates growth). The solution to the problem with the greenhouse design will be inclined toward greenhouses that allow both extremely low and high temperatures in order to keep investments and energy costs to a minimum. Therefore it is very important that these effects of the temperature on the tomato yield are described properly. A literature study made it clear that both low and high temperatures have a negative effect on various growth and development processes of the plant, which subsequently results in a lower yield of tomatoes. Both direct and average temperature effects influence the growth of tomatoes and these effects are implemented in the model in a simple way. Without adapting the preset model parameters, the model we developed was able to accurately predict the tomato yield for four different temperature trajectories: for nearly optimal temperatures for Dutch greenhouse climate conditions; for non-optimal temperatures for Southern Spain greenhouse climate conditions; for extremely low and high average temperatures; and for extreme daily temperature fluctuations.’ ‘In my thesis I then describe a sensitivity analysis to disclose the parameters that have the biggest effect on the greenhouse design and to improve our understanding of the design process. Three sensitivity analysis techniques were applied to the combined greenhouse climate-tomato yield model in order to measure the sensitivities for a greenhouse with a low technology level in Almeria, Southern Spain, and for a greenhouse with a high technology level in Texas, the United



Bram presents his calculation model.

States. The model made realistic prognoses on the indoor climate and the tomato yield for both locations. Results of the sensitivity analysis focused on the effect of one parameter showed that the outside climate had the biggest effect on the performance of the greenhouse, followed by the design parameters and the set points for the indoor climate control. Thus the selection of the right site on which to build a greenhouse is very important. As to the greenhouse parameters, PAR turned out to be the most important factor for greenhouse performance. In order to increase the yield of tomatoes one must design structures with higher permeability to the grow light. The greenhouses must also be sprayed with chalking or fitted with a screen that selectively allows the near-infrared radiation (NIR, the part of the sunlight that acts as a heat source for the greenhouse) to pass. Results of this sensitivity analysis showed whether the capacity of the heating system and the CO2 application was sufficient. Greenhouse parameters that must be adapted to save water, energy and CO2 were also revealed. The impact of light on the tomato yield varied over the seasons, which suggests that adaptable greenhouse roofs have properties that are advantageous over those of fixed roofs. Results of the sensitivity analysis focused on combined effects of parameters revealed intense combined effects of the PAR transmission and ventilation set point

on tomato yield. The sensitivity analysis techniques are capable of quantifying the impact of one parameter, combined parameters as well as their time dependency on tomato yield, the indoor climate and the consumption of resources. However, in order to improve the insight into important greenhouse design aspects, the impact on the net financial result of the greenhouse has to be measured.’ ‘My thesis also describes the economic model that calculates the net financial result (NFR) as a function of the tomato yield, the consumption of the resources and the write-off and maintenance of the greenhouse. The economic model was combined with the greenhouse climate-tomato yield model in order to enable selection from ten different greenhouse designs, all varying in technology level, of the tomato greenhouse with the highest net financial result for conditions in Southern Spain. The greenhouse designs were a typical plastic Parral greenhouse with a slight roof incline or a curved greenhouse equipped with various combinations of technologies to influence the greenhouse climate, such as heating systems, atomising systems (to cool the air) and systems to dose CO2. Results showed that a curved greenhouse with only an atomising system was the most profitable, followed by a curved greenhouse equipped with  >>




‘a greenhouse with a low technology level depends less on variations in the price of tomatoes and that a greenhouse with a high technology level depends less on climate variations’

heating, atomising and CO2 dosing. The difference in financial result between such a greenhouse and a relatively cheap Parral greenhouse was small, however, in comparison with the difference in investment. A sensitivity analysis of the net financial result for the two technological extremes showed that the price of tomatoes, the fraction of tomatoes suitable for sale and the PAR permeability of the greenhouse roof had the biggest impact on the NFR. The results showed that the financial performance of the greenhouse was strongly affected by four factors: the weather; tomato prices; the combined impact of technologies to control the climate; and the type of climate control system used. As the level of technology increased, the net financial result depended less on annual variations in the outside climate and more on the annual variations in tomato prices. This shows that a greenhouse with a low technology level depends less on variations in the price of tomatoes and that a greenhouse with a high technology level depends less on climate variations. In order to select the best greenhouse from many alternatives relatively quickly and easily, we integrated an optimisation algorithm in the design method. This algorithm maximises the net financial result by optimising the selection from alternatives to substantiate the following eight design components: (1) the type of greenhouse structure; (2) the greenhouse roof material; (3) the presence and the type of outside shade screen; (4) the properties of chalk to reduce incident sunlight; (5) the presence and the type of thermal screen; (6) the type of heating system and its capacity; (7) the type of cooling system and its capacity; and (8) the type of CO2 supply system and its capacity. A controlled random search algorithm was applied to 50 fast PCs and adjusted the greenhouse design to the local climate and economic conditions for two different sites: Almeria and the Netherlands. The model selected a greenhouse with a relatively large ventilation surface area (this surface area was the size of 20% of the ground surface area, while this was 14% for Dutch

conditions), chalk to reduce the temperature of the greenhouse air and a relatively low-capacity hot air blower (50 W/m2 in comparison to 200 W/m2 for Dutch conditions) for the sunny, warm climate in Almeria. Chalking was not required for the relatively cold and dark climate in the Netherlands, and the greenhouse was fitted with a 100% aluminium energy screen. The design method selected realistic greenhouses and matching net financial results for both sites, which indicates that we had developed a robust and reliable method. An analysis of the best greenhouses showed that a greenhouse structure with high light permeability improved the economic performance of the greenhouse for both sites, while an outside shade screen, geothermal heating and mechanical cooling caused the greenhouse performance to deteriorate.’ ‘In conclusion, my thesis discusses the model-based design method we developed. Based on the results presented we can conclude that the objective of my thesis was achieved, as the greenhouse design method generated two different greenhouses suitable for the local climate and economic conditions in Spain and the Netherlands. It is to be expected that the design method will also generate reliable greenhouse designs for other sites since the underlying models have been thoroughly validated for a broad range of climates. Insofar as we know, this is the first time that a greenhouse design optimising problem has been described in detail and partially solved. To optimise the entire design problem, the effect of social aspects, labour and logistics on the greenhouse design must be integrated in the greenhouse design method. Aspects to improve the reliability of the three models are under discussion. Since the design method was set up generically, these aspects can easily be integrated in the method. The effect of climate and price uncertainty on the greenhouse design is described and measures have been proposed to limit their influence. Finally, the future perspectives of the design method are presented.



Measuring throughout

the greenhouse You can no longer open a horticulture magazine without reading something about The New Cultivation Method: a homogeneous climate, less heating and thus more efficient cultivation. But what can you actually tell about your climate if you only have one climate box installed per hectare? Wouldn’t it be handy to measure temperature and RH at many more points?

The introduction above is of course a bit oversimplified. The principles of The New Cultivation Method are in fact based on measurements for which more than one measuring box was used per hectare. Nevertheless, you could say that introduction of the New Cultivation Method makes it more important to have insight into the climate’s homogeneity, since it is just that improvement in homogeneity that makes an increase in production possible. Most horticulturists are familiar by now with the possible measures for improving homogeneity but are not monitoring the result, apart from an increase in production. And that is a real pity, because you still do not know what exactly you are doing. You could install several measuring boxes per hectare instead of one, and then you would already be able to tell more about your climate. Of course it would be even nicer to install even more measuring boxes, but the disadvantage of that is that the boxes are not cheap, and thus whether you could easily recover that investment it is highly questionable. In the past few years the term ‘smart dust’ began to come up with some regularity in reference to sensors the size of a grain of sand that were to send all kinds of interesting information to a base station via a wireless network. ‘That is not very realistic,’ observes AgriSensys’ Jouke Miedema. ‘The sensors you see here, however, are realistic.’

Real time and remote Wireless Value, producer of AgriSensys, was founded nine years ago and is working on wireless sensor technology, among other things. According to Jouke: ‘The demand for development of technology enabling supply of information came from diverse directions. For example, a supermarket can no longer get by with a thermometer in a refrigerated section being checked for the right temperature every morning. No, it must be possible to read that type of information nearly real time and remotely. Not only because people want that, but also because regulations make it mandatory. We were already producing such sensors for a variety of companies years ago.’




Decline uncertainty


Uncertainty margin as a result of more sensors and more frequent measurements Figure 1: Reduction in uncertainty

‘Four years ago Wageningen University & Research Centre (Wageningen UR) approached us with respect to a smart dust project. They knew that we engage in that technology and asked us if we could see a possibility of installing a large number of sensors in a greenhouse. We used an existing sensor, modified it and fitted it with a thermometer and an RH gauge. Next we installed a hundred of these small boxes in a one hectare garden, after which measuring could begin.’

Uncertainty To the amazement of the researchers, and the horticulturist who had wireless sensors installed in his garden for the experiment, the variation between the sensors was a maximum of seven degrees. The RH even reached a maximum variation of 32 percent. Jouke continues: ‘As a horticulturist, you do know that there is some variation in your greenhouse as a consequence of a variety of natural and less natural factors, but you do not know precisely how much that variation is, since there are just not enough measuring boxes installed. Now there is an interesting little graph (see Figure 1) in which you plot the number of sensors on one coordinate and the measuring frequency on the other. If you draw a line through these, you plot the reduction in uncertainty in regard to your variation. You reduce your uncertainty concerning the variation in temperature and RH by installing more sensors and measuring more frequently. However, that line is an asymptote and thus will flatten out as you measure more frequently and install more sensors. If you install 25 sensors and measure once every six minutes your uncertainty on the variation will be reduced from 5 degrees to 1 degree; thus an enormous difference and in this case the optimum balance between investment and result.’  >>




Homogeneity in the green house

Homogeneity = 100% when all T-values are in one area: Figure 2: Homogeneity in the greenhouse



It becomes even more interesting when you look at Figure 2, in which the green line represents the temperature measured by the standard measuring box. The red line represents the average temperature, measured by all wireless sensors. Vertical bars indicate what the lowest and what the highest value measured is for every measuring point. Finally, the purple line indicates the degree of homogeneity. Homogeneity is thereby defined as ideal (100%) if all sensors measure a temperature lying within a band width of the average plus/ minus 0.75 degrees Celsius. Jouke says: ‘Homogeneity is best when the temperature is dropping and when it is rising. At a constant temperature, you see that the variation between sensors is fairly large. In Figure 3 you can again see precisely which sensor the variation is the largest for. You can see that not one sensor is inside the bandwidth of three quarters of a degree, but also that the difference in variation is very significant between sensors as well. In concrete terms the figure demonstrates that the sensors that show the most variation are in the problem areas. Because it is of course known what sensor is installed where, you can take a closer look at the part of the greenhouse near the sensors that indicate problems. Causes of differences in temperature and RH include, among other things: non-regulated path heating; insufficient closure of the outer wall screen; poorly closing screen cloths and windows, and poor synchronisation between the outer wall network and heating. These are all matters that were not detected until after the variation was measured. Thus you can imagine that the horticulturists who came to observe this system were enthused.’

The wireless system is now available on the market under the name AgriSensys. A system consists of a number of sensors (available in various quantities), a base station and a range extender, if necessary. Jouke explains: ‘The base station collects the data from the individual sensors and forwards it to your computer. If the distance between the sensors and the base stations is too great, a range extender will ensure that the signal is forwarded. At the suggestion of several horticulturists, the sensors were adapted to make them less sensitive to external radiation.’ That sounds good, but can the data be loaded into a climate computer? ‘Not yet,’ Jouke admits. ‘But we are already talking with the climate computer boys, as they are just as interested in this as the horticulturists are.’ You can purchase a complete AgriSensys system starting at 4,000 euros, plus 1,000 euros for a subscription to the server where all data are sent. According to Jouke you must count on recovering the investment in a year, depending on the situation. In the world of horticulture that is pretty fast. But couldn’t you just rent the system for a while, identify the problem spots and spend a lot less money? ‘That is also a possibility,’ says Jouke. ‘We do have a carry-in option. But don’t forget that some problem areas shift. These are the so-called floating hot and cold spots. If you want to identify them, you will have to measure all the time. Perhaps the best way to regard the system is as a so-called spec-check: you check whether the specifications that your climate system should meet are actually right.’

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Holland Horticulture Technology Review (HHTR) 2012/01