Solar Water Unit For Remote Area
Improving access to Safe Water
Content Abstract Background Madagascar Water Desalination process MEH Design concept Solar concentrato/Receiver Flash Chamber/condenser Flexible solution Sustainable Futur Acknowledgment
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Why SWUFRA ? Project Abstract
n the recent years, factors related to climate change have caused significant issues related to the access of fresh water in Madagascar. On the Southwest coast, a fishermen community is particularly affected by these consequences. Infant population is the most touched by water related illness. UN Water (2008) identified water illness and ‘diarrhea’ as the second highest cause of death amongst children in this area. Local actors, Dr Ramapiherika with the Institute Halieutic and Marine Science (IHSM) of Toliara, are searching actively for an ‘appropriate solution’ to tackle this major issue. One of the approaches envisaged recently, was to use the local resources already available like: solar energy and sea water to produce or treat water on site. There are two options using low investment and energy: solar distillation or solar pasteurization. For its wider range of application the decision to explore solar distillation has been taken. Methods The design methodology used here in this project was varied. Research on ‘Appropriate Technology’ design was helpful to determine the scope and scale of the project. Because of the particular context and the project frame-
work, a scientific approach was taken at the beginning with the analysis of a design matrix. Research ‘through design’ was implemented to determine new discoveries and secondary outcomes. The concept was tested with prototyping, manufacturing and recording the data. Results The first point of the project was to the prove the concept. The testing of the parabolic heat collector prototype demonstrates that water can be heated at a significant temperature (up to 70°C) with UK solar conditions. Those results imply that higher temperatures can be reached with a warmer climate. Through the manufacture of the prototype, appropriate solutions were found in order to decrease the cost of the desalination further. Materials available ‘off the shelf’ or recycled were identified, for example: recycled oil drums, plumbing copper pipe, aluminum foil tape for reflective material. Potentially, those materials will be found locally at a relatively competitive cost. The final design solution has been estimated roughly to £400 (€480). With a collector of 4m2 the design could produce in average: 40 litres/day of distilled water; 290 litres/day of boiled water.
The final design concept will use a: • Compound parabolic solar concentrator • Flash chamber as condenser This improvement was discovered during the manufacturing and development process. The concept with a small alteration can be adapted to be used potentially as a ‘solar pasteurization plant’ also as a‘solar cooker’. Future Out Come In a global Health concern and environmental interdependence, the implementation of solutions (with zero carbon emission) tackling ‘water procurement’ is particularly relevant in the context of sustainable developement. If the proposed design concept is proven to work, it could be implemented with the support of local population in order to produce not only good quality fresh water but also, boil or pasteurize “dirty” water from the well, be used as a cooker and save precious fossil fuel.
Madagascar Madagascar is an island nation separated from the African Continent by the Mozambique Channel, with a population of nearly 20 million. It is the forth largest island in the world with 587,041 square kilometers of land. Madagascar is a country of diversity. The center of the island consists of high plateaus and mountains, some peaking over 2,500 m. The narrow coastal plain that surrounds the central highlands consists of warm areas in the north-west, humid forests in the east and hot arid areas in the south. The island is also well known for its remarkable biodiversity. Madagascar has a high potential for a tourism industry. The country is famous for its unique fauna and flora with high endemism rate. This, combined with the colorful landscapes, provides ideal resources for sustainable tourism. The country is also rich in minerals, oil, and coal, and has seen a surge of foreign investment in its mining sector
during the past years. Another asset of Madagascar is its language. Despite the cultural diversity, people of Madagascar are united with one common language, Malagasy. Due to this advantage, Madagascar enjoys relatively high rates of literacy and school enrollment among Sub-Saharan countries. On the other hand, Madagascar still faces poverty as an imminent issue, with the country ranking at 143rd among 177 countries in the UNDP’s Human Development Index. Despite the efforts made to date, the number of people with access to safe water and sanitation is very low and differs greatly between rural and urban areas. While only 14% of the rural population have access to water compared to 66% of the urban population, 7.5% of the rural and 27% of the urban population have access to adequate sanitation. (WaterAid Madagasar 2010/JICA Madgascar)
Madagascar in Facts: • Population: • Infant mortality: • Child deaths (under five) from diarrhoea per annum: • Life expectancy: • Water supply coverage: • Sanitation coverage: • Below poverty line : • Development index: • Adult literacy:
18.6m 72/1000 17,100 59.9 years 47% 12% 71.3% 145 70.7%
Sources: Human Development Report 2006/09, World Development Report 2006/09, UNICEF State of the World’s Children 2009 and WHO World Health Statistics 2009
Water desalination & MEH process Multi Effect Humidification technology Solar distillation is by far the most cost effective solution to produce fresh water from seawater.The main task was the reduction of energy consumption that requested solar aperture area for water produced daily. One of the most efficient concept developed is the Multiple Effect Humidification (MEH). In this concept the enclosure comprising heat and mass transfer is separated from the solar collectors for heat supply of the process. Evaporation and condensation surfaces are oriented to enable continuous temperature stratification along the heat and mass transfer process, resulting in small temperature gap to keep the process running. Most of the energy afforded in the evaporator is regained in the condenser keeping the energy demand on a very low level of less than 120 kWh/m3. Low energy requirement is essential for cost-effectiveness. The energy use for desalination is often cost-prohibitive: electricity is either expensive and/or not available within the required capacities. A MEH desalination system will surmount this obstacle through drastically reducing energy demand within the desalination process, applying a very effective and energy saving heat recovery system. The optimisation of solar multi-effect desalination plant design is very sensitive to the collector cost. Previous studies by ‘El Nasser’ (1994) has shown that a reduction in collector cost by 50% could re-
sult in a decrease in the minimum cost of potable water from US $4.77/m3 to US $3.03/m3. The minimum water cost is always achievable with an evaporator having the highest performance ratio that corresponds to the largest number of the effects possible. Therefore the design effort was focus on the heat collector, in order to find the ‘most appropriate heat concentrator’ suitable for the context and capable to be manufactured locally. Several design of heat collector are possible: 1.Flat heat collector (used to heat water in developed countries) 2.Linear parabolic heat collector (used for electricity generation plant) 3.Concentrator Parabolic (used for furnace or in solar cooker design) Heat collector selection Because of the abundance of direct sunlight through out the year in this part of the world, parabolic concentrator should be the best suited for the final result. By keeping in mind that the efficiency of the design solution is guided by the efficiency of the heat collector and its ability to transfer heat to the sea water, we can imagine a solution with high concentrator factor.
Mage International (Oman
Concept to prototype Cost effectiveness
Design concept 1
Design and Evaluation of Solutions
The design solution’s criteria have to be related closely to the research question, in order to draw a solution, adapted to local people and using appropriate technology. Therefore the criteria retained for the design solution are:
• Easy to manufacture / reproduce by local workers • Easy to run • Easy to maintain / repair • Easy to Scale up • Long resistance to arid climatic condition • Sufficient freshwater productivity • Cost effectiveness • Supply Chain/ material availability
Concept ‘Flash Chamber’ or condenser The flash chamber is made of 2 recycled oil drums, or one oil drum and one PVC drum. A copper pipe (or plasticpipe) coiled inside the drum collect the heat lost when the hot seawater is flowing inside the chamber.
seawater will return to the lower reservoir finishing the cycle. Within this concept the heat losses are greatly reduced, and the length of outside pipe is also reducing to a minimum. The water travels only upwards to go up to the receiver and then come down through ‘the shower’. At the end of the cycle (evening) the remaining seawater containing a high level of salt, the ‘brime’ is discharged at the bottom of the drum. The parabolic solar collector is placed on top of the upper drum. This disposition allow minimum heat lost in the pipe circuit due to a minimum pipe length.The total height of the unit is 2.76m. 1.Receiver 2.Solar Concentrator 3.Flash Chamber 4.Sea water tank
The bucket at the bottom collects the ‘brime’ which returns back to the lower reservoir. The excess of Bob.G.Williams©2010
Solar Collector/Receiver The Solar Collector The design is a solar dish of 3.2m2 with a focal point located at 28cm from the bottom of the dish. The structure made of fine metal rim could be manufactured with a more malleable material such as bamboo or rattan rods (fig. 22)
The ‘Receiver’ The main innovative aspect of the ‘solar concentrator’ is the elaboration and design of an ‘efficient receiver’ capable of receiving the greatest heat possible. Several studies were made to find a suitable concept.
The principle innovation in the prototype was the elaboration and design of an efficient receiver able to exchange the energy collected by the parabola. Several drawings were made. After more in-depth research using the laws of thermodynamics the choice of a double coil exchanger was made. The double coil of Ø 8mm copper pipe was coated with heat absorbent black paint in order to absorb maximum radiation.
The receiver is painted with a black metallic pipe with high temperature BBQ paint. Inside a coiled copper pipe pass through to enable heat exchange with the water inside. The total pipe length trough is 7m.
Materials used for the collector: • An electric water pump , 12 V of 500Gallon/h • 12 V battery fully charged • 2 m of rubber pipe, insulated with foam • A valve to adjust water flow rate circulating in the pipe • An insulated bucket with 2/3 litres of water • The Parabolic Solar collector • A digital thermometer
The prime aim of the receiver is to collect the heat and transfer it to the water. To do so the maximum pipe area needs to be concentrated at the focal point. A design saving space allowing maximum length has been specially made. A double coil circuit with 5 m of coper a pipe was manufacture. The coil Ø 8mm is covered with a ‘hat’ to stop radiation heat losses. Further development would help to increase the total length to 6 or 8 m of the copper pipe. The entire coiled pipe should, be positioned at the focal point of the parabola, in order to received the rays of light.
Test results: parabolic collector, Plymouth 03/09/2010
The Condenser/ Flash chamber
Principle of the ‘Flash Chamber’ The Flash chamber or Condenser is the cold part of the desalination system. Its aim is to enable the hot seawater to evaporate and condensate on the side. The chamber will be made of recycled oil drum, for economic purposes. However, this material should be perfectly appropriate for the used as condenser. Made of metal covered with anti-oxidant paint it should over time in theory resist seawater corrosion. A longer period of testing should be carried, in order to give the results. The chamber is made of two recycled oil drums. The top one is “domed” on the top, to help the condensate water to drip on the side of the drum and be collected at the bottom. A significant amount of heat is lost when the hot seawater flows inside the chamber, as heat will be transferred to the drum skin and lost to the outside air. One solution, which could be used, is a heat system to recover the heat transferred by the hot water. To do so a coiled pipe inside the drum circulate cool seawater. This water enable the hot vapour to condensate on the inner skin, and in the same time recollect the heat, transferring it directly to the heat collector.
2 The bottom drum, serve as seawater reservoir. Once filled up, (with a max capacity of 42 gallons or 159 litres) the water is pumped to the upper chamber, the cool water circulates in the coil to the top of the second chamber. The pipe comes back to into the chamber after passing the heat collector. The water heated and then realised with showerhead. The dripping hot water is recollected in a recipient who flows into the lower reservoir. The cycle is closed and the water carries its cycle until 50% of the original seawater is left. Due to practical limitation, only 50% of water can be removed from the initial volume . Therefore if the reservoir were full, the maximum water production would be 65litres of fresh water from seawater. However, the system has the capacity to treat any kind of water and grey water, by boiling or even bring lower temperature up to 70°C a much bigger quantity of water
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7 1. Shower/hot sea water 2. Cooler pipe 3. Bucket/retrun seawater 4. Freshwater Tap 5. Seawater Tank 6. Water Pump Specification: SWUFRA ‘Flash Chamber’ 7.Brime discharge 22/09/2010 mameodesign.Ltd© 2010 mameodesign.Ltd
Flexible Solution Concept The design presented is a compact solution with two parts: a solar collector with receiver and a flash chamber to condensate the hot water and collect the freshwater.
The solution needs a pump to circulate the seawater throughout the system. In absence of source of electricity, a photovotaic panel (5 to 10 watt PV recharging a battery) is needed. A water pump of 500Gal/h has been used for practicality purposes. The Solar collector The design of the heat collector has been inspired by a generic concept: Ø1.4m parabolic concentrator (focal 28cm) The first prototype was a parabolic trough built with 4mm plywood and is covered with a reflective material (thermal blanket, Glass mirror cuts). The totalsurface-area of this prototype is 3.8m2. Final Design specification In order to accommodate a family of 15, the desalination plant would have to produce an average of 30 litres of fresh water/day. Therefore the quantity from the final solution is calculated to be sufficient to meet basic needs. The final desalination plant, will use oil drums as reservoir and flash chamber’. An oil drum contain up to 150 litres of seawater. With maximum efficiency, it could produce up to 60 litres of water by
distillation. The flexible use, of the plant allow to boil or pasteurize ‘dirty water’ by heating it up 70°C. By using dirty water instead of seawater, the plant could treat a much greater quantity of water, meeting the needs of several families, a community or a small village. For example, an extra of water could be used for agricultural purposes, grow vegetables and enrich the daily diet.
SWUFRA to meet UN millenium goals Outcomes If this concept could be developed at industrial scale. It could be used to: • Distill water seawater • Doil water • Pasteurise dirty water • Cook with sunshine This project has been an opportunity to explore a range of design solutions which have all the potential to solve the issue of ‘fresh water procurement’. The final concept is a compromised between complexity/efficiency/cost: a compromise made in order to satisfied the constraint of costeffectiveness and meet the greatest number of criteria. In order to manufacture and test the concept in Southern Madagascar the design phase would have to be done locally with the final user input and approval. By testing the various concepts presented in this report within the community a clearer idea of the optimal design solution would came out. An advantage of the proposed design concept, discovered during the project development, is its flexibility to adapt to different case scenario. Be-
cause the community needs might change, it would be possible to use the design also to pasteurise grey water or to boil it. This option allows the plant to treat a greater quantity of water than if it was to distil seawater. For example, dirty water collected from well could become safe if heated to the temperature of 70°C. This temperature (achieved in UK condition), could be achieved in the real conditions at a minimum time. A second important point within the ‘SWUFRA’ concept, is its potential to be used as ‘solar cooker’. This type of cooker is already widely used in this country, where fuel scarcity for cooking purposes has become an issue since deforestation began. The next step with the project will be to integrate the community at the start of a new design process, gathering new information concerning more specific needs, preferred technology, skills, knowledge and other wishes of the community.
Acknowledgements I would like to recognise the special contribution of the following individual, each of whom brought an important input and critic in this project: Dr Ramapiherika Daniel from IHM, Solange&Marcelin Chanmane, Robert Allen Univeristy Plymouth, Rogers Andrew, Chave Malcom Plymouth University Clement Kassandra, Lee Davis, My family, my wife Leila,
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