OPERATIONAL PROGRAMME SLOVENIA-HUNGARY 2007-2013
GEOTHERMAL HEAT PUMPS MANUAL in a scope of project Screening of the geothermal utilization, evaluation of the thermal groundwater bodies and preparation of the joint aquifer management plan in the Mura‐Zala basin
Geološki zavod Slovenije
Nyugat-dunántúli Környezetvédelmi és Vízügyi Igazgatóság
Report prepared by: M.Sc. Andrej Lapanje M.Sc. Dušan Rajver Edgár Székely Project co-workers: Špela Kumelj M.Sc. Joerg Prestor Simon Mozetič István Juhász Péter Bányai Laura Tóth István Hamza
Doc. Ph.D. Marko Komac
Ljubljana, Szombathely, 30.8.2010
INTRODUCTION ................................................................................................................................ 1
UNDERGROUND TEMPERATURE AND GEOTHERMAL ENERGY ....................................... 2
BASICS OF GEOLOGY..................................................................................................................... 5
PRINCIPLES OF HEAT PUMPS ..................................................................................................... 7
SHALLOW GEOTHERMAL SYSTEMS ..................................................................................................... 11 5.1
GROUND‐COUPLED HEAT PUMPS ............................................................................................... 14
WATER SOURCE HEAT PUMPS .................................................................................................... 18
ADVANTAGES AND DISADVANTAGES OF GROUND‐SOURCE (GEOTHERMAL) HEAT PUMPS ..... 21
PRACTICAL CONSIDERATIONS ..................................................................................................... 23
ENVIRONMENTAL ASPECTS ......................................................................................................... 24
GEOTHERMAL HEAT PUMP MARKET........................................................................................... 25
LEGISLATION........................................................................................................................................ 27 6.1
EUROPEAN LEGISLATION............................................................................................................. 27
SLOVENIAN LEGISLATION ............................................................................................................ 32
HUNGARIAN LEGISLATION .......................................................................................................... 34
PROBLEMS WITH REGULATION OF GSHP INSTALATION IN PRACTICE ........................................ 35
FINANCIAL INCENTIVES SHEMES AND BURDENS FOR GHP................................................................. 35 7.1
FINANCIAL INCENTIVES SHEMES IN SLOVENIA ........................................................................... 35
FINANCIAL INCENTIVES SCHEMES IN HUNGARY ......................................................................... 36
PROCEDURE OF GEOTHERMAL HEAT PUMP TECHOLOGY INSTALATION IN SLOVENIA...................... 37
RELEVANT INTERNET SOURCES ....................................................................................................... 45
At present the use of renewable energy sources (RES) in Europe is on the rise, partly due to tendency for reduction of dependence on import of energy fuels, partly due to the Kyoto protocol obligations on reduction of CO2 releases and partly also due to lower energy price gained in this way. One of renewable energy sources is also geothermal energy. The following definition that is used by European Union and the EGEC community is the most proper: »Geothermal energy means energy stored in form of heat beneath the surface of solid earth« (EU Directive 2009/28/EC on promotion of RES). A wide spectrum of technologies is available for the use of geothermal energy. Their applicability is controlled mostly by the temperature level of the heat source; therefore, the fields of use are divided into shallow geothermal energy and deep geothermal energy. Shallow geothermal systems are situated down to a depth of 400 m with temperature up to ca 25°C according to classification of geothermal systems. This division which was determined in 1987 by the Federal bureau of energy economics of Germany, and since then it is somehow accepted in Europe (i.e. VDI 4640 guideline. This boundary between shallow and deep geothermal systems is not formally defined in Slovenia. One of the most penetrating fields of the RES utilization in Europe is the use of heat pumps for heating and cooling as well as for domestic (sanitary) hot water. There are several heat pump types, i.e. air source, water source and ground-coupled. In these recommendations only Geothermal heat pumps are treated which are in the EU Directive 2010/31/EC defined as a machine, device or system that transfers heat from the natural environment (groundwater or underground) into the building or for industrial use with switching the natural heat flow so that it flows from lower to higher temperature. With reversible heat pumps it is possible to transfer heat from the building to the natural environment. Geothermal heat pumps, also known as ground source heat pump (GSHP) is a highly efficient renewable source of energy, acceptable for space heating and cooling of residential houses as well as offices and for domestic hot water. Their great advantage is that they operate by collecting the natural existed heat, and not by heat generation at the fossil fuel burning. In the recommendations an overview is first given of basic geological and geothermal characteristics and basis of thermogeology that deals with a study of occurrence, moving and use of low-enthalpy heat (with temperature < 30°C) in relatively shallow (<200 m) part of geosphere (Banks, 2008). In the main chapter the principles of heat pump operation, their possibilities and applicability are described. Further on are presented the European, Slovene and Hungarian legal frameworks where the technology of geothermal heat pumps is promoted and regulated. Since this is the technology of the RES utilization and dispersed energy production, it means at the same time that the investment costs are higher and it cannot compete with developed technology of energy production from conventional energy sources. The state should help in overcoming this threshold with supporting mechanisms such as loans with decreased rate of interest, subsidies and partly or complete abolishment of the taxes 1
payment obligation for the geothermal energy acquisition. There is still lot to be done here. As for Slovene circumstances, the process of installation the heat pump technology in a region is described. Therefore, the purpose of these recommendations is to present the basic heat pump characteristics, important heat pump design and installation issues as well as points that attention needs to be paid about their planning. For sustainable and successful planning of geothermal heat pump systems it is necessary to include the knowledge of different experts: architect, installer of heating and air conditioning devices, geologist and driller, because only a team work brings the best solutions. At the end the References and relevant web pages are given where additional information on heat pumps can be found as not all details can be included in these recommendations.
UNDERGROUND TEMPERATURE AND GEOTHERMAL ENERGY
Rocks, sediments and groundwater below the solid Earth's surface store the heat; the shallow subsurface can be defined as a huge heat reservoir. The soil is heated in summer by solar energy. Thermal conductivity (capability of material for heat transfer) of natural materials is low and this prevents immediate dispersing of stored heat, but on the other hand it is not so low, therefore, it allows us to use the heat from the underground by heat exchangers. Capability of material to store the heat is called a specific heat capacity. It tells us how much heat can be get from 1 cubic meter of rock with decreasing of temperature by 1 K. Heat can be transferred with three main mechanisms: - Conduction - Convection - Radiation Thermal conductivity of rocks is mostly influenced by mineral structure (thermal conductivity is greater when the quartz quantity is greater), porosity (water content) and substance permeability. Typical thermal conductivity of rocks and geologic substances lies between 1 and 4 W/(m路K). Specific water heat capacity is 4186 J/(kg路K), and for most rocks this value ranges between 800 and 1000 J/(kg路K). This tells us that great amounts of heat can be transferred by groundwater convection. In designing and dimensioning of geothermal heat pumps it is useful to know how the temperatures in the shallow underground vary in the climatic conditions of central Europe. Long-term measurements down to a depth of at least 20 m can give us an answer.
Fig. 1. Temperature-depth profiles, measured at observatory unit Malence (T-z profiles of average temperatures on 15th day of each month in 2008). Black line is annual mean.
The temperature of shallow subsurface is much influenced by annual mean air temperature, so that the heat which is taken by geothermal heat pumps comes predominantly from the absorbed solar energy in the Earth's surface. The external source of the Earth's heat is the solar radiation. In summer the Earth's surface heats up due to intense solar radiation and increased temperatures. The most typical periodical variations are daily and annual temperatures on the Earth's surface which have influence on the shape of geotherms (T-z profiles) in the underground. The annual temperature variations penetrate almost 20 times deeper than the daily ones (the latter 1 to 2 m only). The annual variations can be illustrated with temperature profiles that are measured on our observatory unit Malence. It may be seen from the following figure that the Sun's heat doesn't reach deeper than just a few tens of meters below the surface. Several years of monitoring at the same observatory give us chance to see (Fig. 2) how daily averages vary in different depths:
Fig. 2. Daily temperature averages in depths of 1 to 10 m, measured at observatory unit Malence in a period Dec. 1, 2003 to Apr. 14, 2005.
From both figures it is clear that annual variations diminish quite a lot already down to 10 m depth although small variations (few tens of degree) still persist to 20 m depth. It is also visible from Fig. 2 that maximums and minimums of temperature curves delay in time. The subsurface geology and thermal properties of rocks and soils have certainly some influence on the values of variations. The present thermal field in the Earth is a consequence of internal (planetary) and external (cosmic) sources. The internal sources mostly include the heat of radioactive decay, and less the energy residues from the condensing during the formation of our planet. The Earth's heat is constantly lost through its surface into the space (Universe) what can be found out with heat flow density (HFD) determination. From the present HFD some 83% derive from heat of the radioactive isotope decay and only 17% from the Earth's cooling (Gosar & Ravnik, 2007). The HFD values are determined in the best way with continuous temperature measurements in deep boreholes (temperature gradient) and with thermal conductivity measurements of rocks in the depth sections where temperature is measured. The average HFD on Earth is 87 mW/m2, on continents only it is 65 mW/m2. In Slovenia the HFD is on average 60 mW/m2, but the values are very different, from just 30 mW/m2 or less in the mountainous regions of western, southern and partly northern Slovenia to around 150 mW/m2 in the Prekmurje region as a consequence of smaller and greater temperature (geothermal) gradients. In the upper few kilometres of the Earth's crust the geothermal gradient shows on continents on average 30째C/km.
BASICS OF GEOLOGY
Geological situation is that part of GSHP design which cannot be changed by the planner. Design needs to adapt to geology, and thus requires knowledge of geological data (Sanner, 2010): Rock type and hardness (for GSHP drilling; i.e. drilling of boreholes or wells) Ground thermal characteristics (for GSHP operation) Groundwater situation (for GSHP drilling and operation) Geological development of a region can be quite variegated in the geologic time. In the course of time different rocks and soils were deposed, which have suffered many processes of diagenesis, mostly consolidation and solidification, depending on physical conditions (temperature, pressure) during the sedimentation and, of course, on presence of fluids. Thus, owing to motley geological structure of Slovenia, we may expect quick variableness of drilling conditions in areas with the contacts of different types of rocks. In the north-eastern Slovenia (as well as in the Zala and Vas counties in Hungary) where Tertiary clastic sedimentary rocks together with Quaternary sediments prevail, the rotary (mud) drilling (including temporary casing) predominates and is a preferred method. In areas with carbonatic, magmatic or metamorphic rocks the hammer method is the preferred one at least to depths of about 250 m.
Fig. 3. Areas with preferred drilling methods in Slovenia. The basic map is a simplified geological map of lithological units.
The hydrogeological structure of the land has an influence on decision about the drilling method and especially on type of the used heat pump technology. We distinguish the following aquifer types (Struckmeier et al., 1995):
Fig. 4. Aquifer types, standard hydrogeological legend (adapted after Struckmeier et al., 1995)
Knowledge of geology on site is important for selecting the correct drilling method, and to avoid problems with lithological surprises, that is when hard or on the other hand soft layers are encountered, or with hydrogeological risks. Specific situations are possible where during the drilling it is necessary to change from one drilling method to another, especially when boreholes are drilled in areas with rocks of mixed lithological structure (e.g. alternation of carbonate and clay rocks) with varying hardness and permeability. In fractured aquifers the hammer drilling is the preferred method. We need to be cautious in situations when there is a possibility of drilling into confined or artesian aquifer, especially for drilling for (vertical) borehole heat exchangers (BHE). In cases of artesian aquifers also the reinjection is more difficult. In the unconsolidated sediments with intergranular porosity the temporary casing is required, and drilling is predominantly the rotary one. Knowledge of ground thermal parameters is important for correct design of BHE (Sanner, 2010). For BHE in such ground where the heat conduction prevails, the thermal conductivity 位 is crucial; its values in practice are between 1 and 4 W/(m路K). Knowledge of permeability and groundwater flow is important for groundwater heat 6
pumps, but groundwater can also have an influence on efficiency of BHE (when Darcy-flow is high). For projects with the installed thermal power of ca 50 kW and upwards the Thermal Response Test is a standard procedure for determining ground thermal parameters.
4 PRINCIPLES OF HEAT PUMPS A heat pump is a device that pumps heat from a low-temperature environment (surface water, groundwater, rocks) to a high-temperature one (central heating). The heat pumps need an electric energy to perform mechanical work. The lower temperature primary heat source must be connected to an evaporator; hence we get a geothermal (ground-source) heat pump. Geothermal heat pumps use the fact that the Earth (below the surface) stays at relatively constant temperature throughout the year, warmer in winter than the air above it and cooler in summer, something similar as in a carstic cave. In winter the stored heat from the ground or groundwater is transferred to the building, and in summer it is transferred from the building back to the subsurface (underground). In other words, the ground soil acts as a heat source in winter and as a heat sink in summer. Heat pumps transfer heat by means of circulating a refrigerant fluid around a compression-expansion cycle (Banks, 2008, p.62): 1. In the heat exchanger (evaporator) the refrigerant fluid is circulating at very
low temperature. When the refrigerant fluid begins boiling during the heat exchange with primary fluid, it absorbs a large amount of latent heat of vaporisation. 2. The refrigerant fluid, now a vapour at higher temperature, then passes through
a compressor, powered by the electrical energy. When a gas is compressed, the temperature rises. The pressurised gas thus emerges from the compressor at a high temperature. 3. The heated refrigerant fluid passes through another heat exchanger (the
condenser), where heat is delivered to the heat consumer circuit (e.g. for space heating). The vapour starts to condense back to a liquid, shedding more latent heat as it does so. After passing through the condenser the refrigerant fluid is still pressurised. 4. The refrigerant completes the cycle by passing through an expansion valve,
where the temperature drops significantly. The fluid is also depressurised.
Fig. 5. Principle of heat pump (after http://www.heatpumpcentre.org/)
The refrigerant fluid within a heat pump should be thermally stable, have a suitable specific heat capacity, have a volatility/boiling point tailored to the operating temperature and pressure of the heat pump and be environmentally benign. Electrical energy used to power the heat pump's compressor is converted, partly to sound energy (the hum of the compressor), but mostly to heat energy, which is absorbed in the refrigerant and must be discharged at the condenser to the heat consumer side (Fig. 5). The working temperature of the heat pump fluid, that is adequate to support our domestic heating system, may be: >60°C 45-55°C 30-45°C 25-30°C
if we have an old conventional hot water central heating system, if we have a more modern low-temperature central heating system, with a high radiator surface area in our house, if we have underfloor waterborne central heating, if we use warm air circulation as our means of heating.
The efficiency of the heat pump is usually referred to as its coefficient of performance (COPH) and it depends on a level to which delivering temperature must be increased. The efficiency of the heat pump decreases with increasing delivering temperature and decreasing source temperature. A given heat pump does not have a fixed COPH: this will depend on the operating conditions and temperatures. The efficiency of the heat pump (COPH) is greatest when the difference between the temperatures at the delivery side and the source (environmental) side is minimised. Coefficient of performance for an idealised Carnot cycle (Heap, 1979), is: , where H heat delivered at elevated temperature, E electrical power input for the heat pump compressor, Θ1 fluid temperature at the delivery side and Θ2 fluid temperature at the source side (groundwater, rocks or soil). 8
The real COPH of a heat pump is in practice lower than the ideal, for several reasons Heap, 1979): The evaporator temperature (Θ2) is usually significantly below the environmental source temperature in order to ensure a kinetically rapid transfer of heat from the environment to the refrigerant. Similarly, the condenser temperature (Θ1) is higher than the temperature of the space to be heated, Real vapour compression heat pumps do not use the ideal Carnot cycle of vapour compression but often a cycle called the Rankine cycle, which is more practical but slightly less efficient, Compression inefficiencies and other inefficiencies in the system. Let us consider a simple water-source heat pump, based on groundwater being pumped from a well, and see how much heat can we extract in ideal conditions. In Slovenia and Hungary groundwater might be expected to be at a temperature of around 11°C. We can thus pump groundwater from the ground at a rate Q=1 l/s that it passes into our heat pump's evaporator. The heat pump will extract a heat energy flux (G) from the groundwater and its temperature will drop. A typical temperature drop (Δθ) might be around 5°C, leaving us with a cool groundwater at a temperature of 11°C – 5°C = 6°C to dispose of (back to the same aquifer). The heat extracted is upgraded in the heat pump to a higher temperature which is used for domestic heating system. Assuming that energy loss due to acoustic noise is negligible and that all extracted heat and heat of compression is efficiently delivered to a point of use, the total heating effect (H) is given by H ≈ G + E, where G is the heat extracted from the ground, and E is the electrical power input:
We can relate the heat extracted from the groundwater to the flow rate Q, the temperature drop across the heat pump (Δθ ≈ 5°C) and the specific heat capacity of water (Sw = 4186 J/(L·K)): Thus, if Q = 1 L/s, then G = Q · Δθ · Sw = 1 L/s · 5 K · 4186 J/(L·K) = 20,93 kW. If we can obtain a heat pump with a COPH of 4, and knowing that means that
H = 20,93 kW * 4/3 = 27,9 kW in E = 6,97 kW.
We should consider that the electricity is also spent for pumping water from the well with submersible pumps and that electricity is also used by circulation pumps of the heating system too. For this reason the seasonal performance factor of heat pump SPFH, which is an average coefficient of performance COPH for entire heating season, and a system seasonal performance factor (SSPFH), that takes into account all power expenditure in the system were defined.
Geothermal heat pumps for cooling If we invert the geothermal heat pump, so that it extracts the heat from the building and reject it to the ground or groundwater we are talking about the heat pump in the cooling mode. The temperature of ground or groundwater increases for few degrees in that process. We can also define the coefficient of performance COPC, which is equal to , where C is heat removed from the building (kW). The total heat rejected to the ground is . If we compare this equation with equation for heat pump in the heating mode we will see that the amount of heat rejected to the ground to deliver 1 kW cooling effect is significantly higher than amount of heat extracted from the ground to provide 1 kW heating effect. In the heating mode the electrical energy powering the heat pump compressor turns up as a useful heat, contributing to satisfy the heating load of the building. In the cooling mode the electrical energy transforms in yet more waste heat to be rejected from the building. Use of heat pumps in cooling mode is not cheap neither efficient in terms of CO2 emissions as free cooling, where cold water circulates through the central heating system, but may be for 20-40% more efficient than conventional air heat pumps (Banks, 2008).
5 SHALLOW GEOTHERMAL SYSTEMS Geothermal (ground-source) heat pumps of both types (ground-coupled and watersource) use the ground temperature (shallow subsurface), that is mostly in a range of 5 to 30°C, by either (Lund, 2000, p.209): transferring heat from a low-temperature resource to that of a hightemperature reservoir (heating), or removing heat from a high-temperature resource and rejecting it to a lower temperature reservoir, thus providing cooling to a space. In general, to use the constant low temperatures of the ground, there are 2 options: 1. Increase temperature of geothermal heat to usable level by heat pump – geothermal heat pump or ground source heat pump (GSHP), 2. Increase temperature in the ground by storing heat (in a cooling mode) or decrease temperature in the ground by extracting heat (heating mode); we artificially change the temperature in the subsurface - Underground Thermal Energy Storage (UTES). Shallow geothermal systems are very adaptable and can be arranged to almost every underground situation. The ground system is typically coupled to heat pump for attaining high enough temperatures. Two major types of geothermal heat pumps exist: ground-coupled heat pumps or GCHP (closed loop) and water source heat pumps (open loop). The various shallow geothermal methods exist to extract heat from the shallow underground (Sanner, 2010; Lund, 2008): Closed loop (ground-coupled):
Horizontal loops Borehole heat exchanger (vertical loops) Energy piles (encased in a foundation) »slinky« in a horizontal trench
Open loop (water source): Ground water wells Water from mines and tunnels Water from ponds and lakes
Depth 1.2 to 2.0 m 10 to 250 m 8 to 45 m
4 to 50 m
An efficient method with open loop system is, for example, a groundwater well. Here we have a heat transfer from a ground to a well by pressure difference (pumping). It is necessary to drill both, a production and an injection well (Sanner, 2010). 11
The energy performance of a GSHP system can be influenced by three primary factors (Lund, 2000, p. 219): ď‚ˇ The heat pump machine, ď‚ˇ The circulating pump or well pumps, ď‚ˇ Ground-coupling or groundwater characteristics. The heat pump is the largest single energy consumer in the system (Lund, 2000, p.219). Its performance is a function of two things: the rated efficiency of the machine and the water temperature produced by the ground-coupling (either in the heating or cooling mode). The most important strategy in assembling an efficient system is to start with an efficient heat pump. It is difficult and expensive to enlarge a groundcoupling to improve the performance of an efficient heat pump. Another efficient method with closed loop system is, beside the horizontal loop, a borehole heat exchanger (BHE). At these systems the antifreeze based carrier fluid circulates inside the closed tubing loop that is coupled through the borehole or in a horizontal trench. In the heating mode a cooled fluid ( typically water with additives as glycol or other antifreeze solution, for example ethanol or salt) circulates from a heat pump and absorbs the heat by conduction from the ground, then returns to a heat pump where the heat is taken away. The fluid is cooled again and is ready for a new cycle. In the cooling mode the warmed carrier fluid circulates from the inverted heat pump into the ground and delivers partly its heat to relatively cooler ground. Horizontal loops in trenches are one of the cheapest heat pump methods with closed loop. The optimal depth of trenches is 1.2 to 2.0 m, which is simple to dig with a trench-digger, and it is deep enough to assure the thermal energy storage high enough for the heating in winter time. At the same time it assures a suitable wetness and insulation to winter frost, and on the other hand it is shallow enough to enable the solar heat and heat of the atmosphere to substitute the thermal storage around the loop in summer months.
Fig. 6. Borehole heat exchanger (Lund, 2008).
Heat is transferred from a ground to the BHE by temperature difference (Sanner, 2010). The advantages of this method are: No regular maintenance necessary Safe operation Possible virtually everywhere Disadvantages are: Limited capacity per borehole Relatively low temperature level of heat source With regard to aforementioned shallow geothermal methods the following types of geothermal heat pumps are usually set up (Sanner, 2010): Coaxial BHE U-pipe BHE 13
Spiral BHE Groundwater wells Horizontal loops with glycol or with direct expansion or direct circulation (DX). For the former it is alcohol that is not as corrosive as brine (CaCl2). As for the latter the intermediate heat exchanger and fluid are eliminated. Larger charges of refrigerant are required and system reliability is compromised. Therefore, the future of DX GCHP is not clear because of environmental concerns (Lund, 2000, p.211). DX schemes were more common in the early years of GSHP systems (Banks, 2008).
Fig. 7. Types of geothermal heat pumps as to the loop settings (Sanner, 2010).
5.1 GROUNDCOUPLED HEAT PUMPS Taken as a whole there are these heat pump settings (Lund, 2008): Ground-coupled or earth-coupled (closed loop), where tubing network is directly buried in the ground. Generally this is a thermally-fused plastic pipe 14
with water or antifreeze (20% propylene glycol) solution circulated through the tubing: o Horizontal o Vertical (BHE) o Spiral coil in vertical hole o »Slinky« in a horizontal trench o Encased in a foundation pile o Direct expansion (no heat exchanger) One or more loops in a single hole or pile. Heat is collected by horizontal ground loops that are usually straight pipes or slinky pipes (spirals) buried in trenches from 1.2 to 2 m deep and spaced a minimum 1.5 m apart in case of straight pipes, or 3 to 5 m apart in case of slinky pipes (Lund, 2000, p.211; Banks, 2008, p.192-193). This allows for minimum thermal interference between pipes; however, this system is affected by solar radiation. Thus, it is the solar energy stored in the ground that is mostly used here. The length of copper pipes with a hard PVC coating or polyethylene pipes reaches several hundred meters. Soil temperature is predominantly influenced by the air temperature variations. Solar radiation causes a cycling of soil temperatures that lags in time and decreases with depth due to the insulating properties and thermal diffusivity of the soil, as shown in Fig. 2. However, the temperature is much more stable than for air-source HP units. Moist soil has greater temperature swings than dry soil. The horizontal loops can be placed in a double layer, i.e. first pipe (flow) in a depth of 1.2 m, second (return) pipe 1.8 m deep. There exist many different configurations of horizontal ground loops in trenches (Banks, 2008; Lund, 2000). Their efficiency is primarily influenced by the soil thermal conductivity and moisture, as well as by the presence of groundwater.
Fig. 8. Installation of horizontal ground loop system (after www.hgd.hu)
The area overlying the horizontal ground loop needs to be large enough to receive sufficient replenishment of solar and atmospheric heat during the summer season to compensate the utilized heat (Banks, 2008, p.184). The ground should be conductive enough to transmit heat efficiently to the loop. The contact between the ground and the pipe should be thermally efficient, and the pipe should be constructed of a material that is durable, tough and sufficiently thermally conductive. Also very important is the right choice of the carrier fluid, as it should efficiently exchange heat with the loop wall, should have some properties as: low viscosity to assure a 15
turbulent flow in pipes, high specific heat capacity, a freezing point below the minimum operating temperature, and should be environmentally acceptable (low toxicity, inflammable). Borehole heat exchanger (BHE) is a ground-coupled vertical loop of the coils in a drilled borehole. The pipes are filled with water-based or antifreeze solution for heat transfer. The vertical loops are controlled by the mean annual temperature of the area and the geothermal gradient and thus, geothermal energy is mostly utilized. Vertical loops have a more stable temperature environment. The borehole depths are usually from 70 to 150 m, but could be slightly shallower in areas of increased geothermal gradient. In Germany and Austria the spacing between two borehole heat exchangers should not be less than 6 m and 5 m, respectively. Vertical loops are used where land space is limited for horizontal loops or trenching would disturb the surface landscape. However, drilling costs are expected to be reasonable.
Fig. 9. Installation of borehole heat exchanger (after www.hgd.hu)
The required depth design for small BHE systems is usually set according to tabled values of specific heat extraction (e.g. in VDI 4640 Bl. 2; Sanner, 2010).
A mistake that is usually seen in many projects around Europe is that typically a value of 50 W/m is used for all sites, neglecting geological differences! Usually specific heat extraction rate is tabled for 1800 h/a (heating only) or 2400 h/a (heating and domestic water).
Fig. 10. Borehole drilling for a vertical heat exchanger (Photo: Aleksander Bokan)
For borehole heat exchangers with heat pumps that operate annually from 1800 to 2400 hours and do not include cooling, the specific heat extraction rate can be determined according with the following table (Sanner, 2010). For design plan a heat demand for heater and for domestic water must be considered. Knowledge of thermal parameters of the ground is important for the correct BHE design (Sanner, 2010). For borehole heat exchangers in ground with heat transfer dominated by conduction, the thermal conductivity λ is crucial; its values in practice are between 1 and 4 W/(m·K). Knowledge of permeability and groundwater flow is important for groundwater heat pumps, but groundwater can also have an influence on the BHE efficiency (when Darcy-flow is high, but not too high, otherwise it's negative influence). Table 1. Values of specific heat extraction rate from VDI 4640 part 2, status 2001
Underground General guideline values: Poor underground (dry sediment) (λ < 1,5 W/(m·K)) Normal rocky underground and water saturated sediment (λ < 1,5 – 3,0 W/(m·K)) Consolidated rock with high thermal conductivity (λ > 3,0 W/(m·K)) Individual rocks: Gravel, sand; dry Gravel, sand; saturated with water For strong groundwater flow in gravel and
Specific heat extraction, W/m for 1800 h for 2400 h 25
< 25 65 - 80 80 - 100
< 20 55 – 65 80 – 100 17
sand, for individual systems Clay, loam; damp 35 - 50 30 – 40 Limestone (massive) 55 - 70 45 – 60 Sandstone 65 - 80 55 – 65 Siliceous magmatite, a lot of quartz (e.g. 65 - 85 55 – 70 granite) Basic magmatite (e.g. basalt) 40 - 65 35 – 55 Gneiss 70 - 85 60 – 70 The values can vary significantly due to rock fabric such as crevices, foliation, weathering, etc. For greater number of operational hours (e.g. for the sake of the heating of swimming pools, extreme climate zones, etc.) it is necessary to decrease the aforementioned heat extraction rates so much that a maximum allowed extraction work (heat extraction rate x 1800 h/a or 2400 h/a) is not exceeded. If this extraction rate is exceeded we must expect an undercooling and frequent changing of the frost and melting conditions around the borehole heat exchangers. The heat pump efficiency can be decreased significantly. The aforementioned values of extraction derive from the existing BHEs and should be followed if there is no other data on thermal conductivity of the underground on specific site. For a larger number of small BHE systems the aforementioned tabled values should be reduced. When we have an alternating operation of heating and cooling it is favourable to have some thermal regeneration in the underground. If the detailed analyses of thermal conductivity of the underground rocks and soil have not been done it is not allowed to exceed 25 W/m of heat input for cooling the single family houses and similar objects; this applies to the BHEs for heating and cooling. For projects with installed thermal power of 50 kW and more (in some cases in Germany 30 kW is considered) a thermal response test is a standard procedure for determining the underground thermal parameters (thermal conductivity, borehole thermal resistance).
5.2 WATER SOURCE HEAT PUMPS The water source heat pumps are usually of 2.5 to 35 kW rating capacity. Groundwater or water source systems (open loop) use well or lake water. Water sources can be abstracted from (Lund, 2008): Well water Lake (pond) water Mine water Tunnel water Refrigerant fluid: since 2003-2004 these fluids are in use mostly: R-410A and R407C. The efficiency (COP and EER-Energy Efficiency Ratio) depends on the inlet water temperature.
The fundamental types of information required to design a well for a heat pump are as follows (Banks, 2008; p.113): We must ascertain the existence of an aquifer on our project site and assess its properties, For the designed depth of well we should know the depth of the aquifer stratum, the groundwater level in the aquifer and, to some extent, the hydraulic conductivity of the aquifer, Diameter of the well depends on the yield of the well, and consequently the diameter of the required pump (which must fit comfortably within the well), The design yield of the well depends on the hydraulic properties of the aquifer and by the desired heating/cooling load, Aquifer lithology and its hydrogeological properties govern the type of well required and hence its cost. When developing the groundwater heat pump system it is necessary to acquire a water permit for heat use from groundwater. To do so it must be proved with a pumping test that the desired water quantity can be pumped from well without influences on the environment and without any harm for the other aquifer users.
Fig. 11. Pumping test (Photo: Aleksander Bokan)
The necessary drilling depth of the abstraction and injection well is determined from hydrogeological maps and cross-sections, or from existent data on up-to-date wells and boreholes. These heat pump type systems are usually used in the already known areas, in the sedimentary basins and valleys. Usually such a depth is sufficient to reach the first important gravel or sandy-gravel aquifer, unless there are restrictions 19
on water supply that in turn shows the need for greater depths, or if the exploitation from the aquifers in the water restricted areas is not allowed at all. The common design flaws (difficulties) in developing the open loop heat pumps systems are (Banks, 2008; p.148): Lack of hydrogeologists design input (recommendations, etc.), Overestimation of the hydraulic properties of aquifers, which brings up to a lower water flow rate than it has been projected for a chosen heat pump, Lack of consideration given to disposal of rejected water, or to reinjection of thermally used water, Lack of appreciation on possible complications with water chemistry and microbiological composition of groundwater (water quality could be problematic owing to CaCO3 and/or Fe bacteria, which form the scaling or damage the heat exchanger), Lack of consideration of possible thermal-hydraulic breakthrough between reinjection and production well, compromising the efficiency of the system. Difficulties can be minimised by (Banks, 2008; p.116): Maintaining a high pressure within the groundwater circuit to prevent degassing of CO2 within the heat exchanger, Preventing contact between the groundwater and oxygen in the atmosphere (i.e. closed systems), Addition of small amounts of biocide chemicals or reducing chemicals to prevent the formation of biofilms and the oxidation of ferrous iron, respectively, Regular maintenance: flushing of the exchanger with acid or proprietary detergents or reagents to remove build up of calcite or manganese/iron oxyhydroxide deposits; selecting a heat exchanger that can be taken apart for cleaning. Groundwater, which has delivered heat to the heat exchanger in the heating mode or has accepted heat in the cooling mode, is to be reinjected into the same aquifer from which has been removed.
Fig.12. A series of reinjection wells of water source heat pumps heating system for larger public facility (Photo: Aleksander Bokan)
5.3 ADVANTAGES AND DISADVANTAGES OF GROUNDSOURCE (GEOTHERMAL) HEAT PUMPS In this section we will present the comparison of the water-source heat pumps (openloop) with ground-coupled heat pumps (closed-loop) and the comparison of geothermal heat pumps with air-source heat pumps and natural gas heating systems. Each of these technologies has certain advantages in disadvantages; which one will prevail in the choice of heating depends from many factors. Geothermal heat pumps overcome the problem of resource variations, because ground temperatures remain fairly constant throughout the year. Depending upon the soil type and moisture conditions, ground (and groundwater) temperatures experience little if any seasonal variations below about 10 m (Lund, 2000; p.209).
Comparison of the water-source heat pumps (open-loop) with ground-coupled heat pumps (closed loop) Advantages of open-loop heat pump systems are as follows (Banks, 2008, p.122; Sanner, 2010): High specific heat capacity of a natural medium (groundwater) that occurs at constant temperature in the subsurface; relatively low cost, Heat is extracted by forced convection of groundwater rather than by subsurface conduction; thus more heat is extracted per borehole than closedloop systems do, Relatively high temperature level of heat source. There are also disadvantages of open-loop heat pump systems (Banks, 2008, p.122; Sanner, 2010) as they: Are geology-dependent. They require an aquifer, capable of providing sufficient yield, Need two properly constructed, durable (i.e. expensive) water wells with pump installations, monitoring and control mechanisms, Incur pumping costs associated with abstracting the groundwater from the well, Generate a used water flow that must be legally reinjected into the same aquifer or sinking trench, Will usually require water permit for pumping and reinjecting the groundwater, May need to be monitored for water chemistry; maintenance required for wells and other equipment to prevent clogging, biofilms, fouling or corrosion of heat pump, exchangers or wells. Comparison of geothermal heat pumps with air-source heat pumps Geothermal heat pumps have several advantages over air-source heat pumps (Lund, 2000, 2008): They consume less energy to operate, the operational costs are lower, They tap the earth or groundwater, a more stable energy source than air, (hence they are 50 to 100% more efficient than air-source heat pumps), They do not require supplemental energy during extreme outside air temperature, They use less refrigerant, They have a simpler design and consequently less maintenance, Do not require the unit to be located outside exposed to the weather, Longer equipment life, Have lowest emission of CO2 among all heating sources. The main disadvantages as compared to air-source heat pumps are (Lund, 2000, 2008): Higher initial capital cost: due to extra expense to bury heat exchanger pipes in the trenches or for drilling the boreholes in closed-loop or open-loop (water source) systems; hence they are 30 to 50% more expensive than air-source units, Lack of trained and experienced designers and installers, Lack of understanding by government regulators, 22
Shallow horizontal heat exchangers are affected by surface (air and sun) temperature variations –thus, requiring 30 to 50% more pipe in the ground for the sake of safe energy supply. Comparison of geothermal heat pumps with the natural gas heating system Disadvantages of geothermal heat pumps are higher initial capital cost compared to the costs of heating with natural gas from the gas network. Advantages are: lower CO2 emission and longer life of the heat pump equipment (20 – 25 years) compared to a gas heater (12 years); no costs for regular annual checkups of the gas equipment; the economics is supported by state subsidies. In sites where there is a gas network, usually not financial viewpoints but the environmental viewpoints prevail for installing the GHP system, which are additionally directed by the renewable energy sources (RES) regulations. It is important to know that bigger is the geothermal heat pump, cheaper is as regard to installed heating power (kW). Therefore, bigger is the building, lower are the initial capital costs for the GHP system, thus more economically justifiable is its installation.
5.4 PRACTICAL CONSIDERATIONS GSHPs are low-noise installations, but no no-noise. Make sure they are installed in an insulated and vibration-proof cabinet in a separate room away from main living areas. GHSPs use electricity very efficiently. A 10 kW unit may only consume 2.5 kW electrical energy (Banks, 2008). On start-up, the compressor will draw significantly more power than its normal running (up to three times more). For heat pump installations in excess of 20 kW, a three-phase electricity supply may be necessary. GHSPs operate most efficiently (highest COPH) with a low-temperature output, running steadily for longer periods. GHSPs can be retrofitted to older heating systems, but they may not provide a wholly comfortable level of heat. A simple, flexible solution for ground source cooling and heating in larger commercial or industrial complexes is to circulate a fluid, chilled or heated by the heat pump, around a so-called building loop within each heating/cooling block. Fan-coiled units, mounted on this loop, will distribute warm or cool air throughout the space (Banks, 2008). GHSPs can also be used to supply domestic hot water. However, the efficiency of most GSHP systems decreases at such high temperatures. For example, the COPH of a heat pump delivering hot water at 55°C may not be more than 2 (Banks, 2008). Furthermore, domestic hot water should ideally be delivered at temperatures in excess of 60°C to avoid problems with bacteria Legionella. An alternative option might be to use the heat pump to raise water temperatures to around 45°C, and then a conventional resistive element immersion heater to boost the temperature above 60°C.
It is also important how to design a heat pump according to the peak heating demand on the coldest day in an average year. If we consider the daily temperatures fluctuations throughout the year, we can see that the lowest temperature (and thus highest heat demand) occurs only a few days a year. Since investment costs are related to the pump capacity, it makes sense to select a heat pump that is not designed for the peak heat demand. In Scandinavia they have calculated that the GHSPs with the capacity around 60% of the calculated peak heat demand would fulfil 90% of the heat demands for the heating season (Banks, 2008, p. 107). The remaining 10% is necessary to provide with an additional source of heat. If we install a GHSP with a too high capacity and have a too small thermal storage to act as buffer, it will constantly switch on/off, which will result in faster wear of the compressor. In addition, it is important to know that GHSPs work with maximum energy efficiency at base load and are not particularly responsive to short-term temperature fluctuations. To fulfil peak heat demands more conventional sources should be used, which would enhance the level of system responsiveness. For safe and reliable operation of the GHSP is also recommended that we use heat storage, such as hot water tanks, that way the system is protected from sudden short-term needs. Heat pump is switched on again when the water temperature in the heat storage falls below a certain threshold. This prevents repeated switching of the compressor and protects it against fast wearing. An alternative method of heat storage, for example, is the installation of underfloor heating system in the thick concrete slab that is heated by GHSP at night, by day it radiates heat into space. If we use the GSHPs for combined heating and cooling, capacity of the heat pump should be selected on the basis of summer cooling load and not on the need for heat.
5.5 ENVIRONMENTAL ASPECTS In many areas of ground source heat technology, laws regulating the use and abuse of subsurface heat resource in Slovenia and Hungary do not exist. In the absence of binding legislation, regulators and professional trade organisations are seeking to develop codes of best practice, especially in countries with a developed market of heat pumps such as USA, Germany, Sweden, Switzerland and Austria. In this chapter, we will try to identify primary impacts that regulators and developers of ´best practice´ will seek to address. These typically take three forms (Banks, 2008): -
regulations regarding buildings thermal efficiency and the performance of heat pump systems, concerns over groundwater contamination and the hydrogeological impacts of ground source heat schemes, concerns over impact of changing the temperature of the subsurface by extraction or reinjection of heat.
From the perspective of environmental protection are of interest only the last two indents, the first one is described in Chapter 5. Environmental regulators often have concerns over the potential hydrogeological impact of borehole drilling and ground source heat technology on aquifers. For closed-loop systems, as there is usually no actual abstraction or discharge of groundwater, or any discharge of pollutants (only the possibility of a leakage), the legal tools may not exist for environmental regulators to control such systems. Regulators will thus be concerned that uncontrolled drilling of closed-loop systems by inexperienced drillers, could result in the pollution of aquifers by migration of surface contaminants down poorly constructed boreholes, the connection of separate aquifer horizons and the unwitting penetration of artesian aquifers (Banks, 2008). Furthermore, regulators may be concerned about the pollution potential from leakage of refrigerants into the ground (Banks, 2008). As regards open-loop systems, regulators have some existing legal framework to exercise control, especially the Water Act which usually regulates water permits for water production. The environmental regulator will usually seek to limit detrimental effects on aquifers, and to protect the interests of the environment and other users. Regulators may seek to prevent wastage of groundwater reserves by placing limits on the abstraction rate permissible or insisting on 100% re-injection (doublet system mandatory) of used water back to the original aquifer, prevent detrimental changes to the temperature or chemical quality of surface water, prevent or limit widespread changes in aquifer water levels and prevent large-scale changes in aquifer groundwater temperatures beyond the immediate location of the GSHP (Banks, 2008). Detrimental effects may be the following: Extraction of heat causing ground freezing and frost heave. Freezing of ground causing damage to built structures, buried services and plant roots, Warming of ground causing thermal expansion with the geotechnical consequences, or desiccation of soils due to vapour migration, Thermal interference between neighbouring closed-loop schemes, decreasing the efficiency of the scheme for their respective users.
5.6 GEOTHERMAL HEAT PUMP MARKET Heat pumps are used for both heating and cooling. Their heat capacity range between 3 kWt to 150 kWt, a typical unit has a capacity of 12 kWt. There is 1, 7 million units in 33 countries around the world. Growth in the number of units is around 20 to 30 % annually. Assuming that the average COP is 4, it means a 75 % saving of electricity. The figure below shows the increasing market of geothermal heat pumps in Europe (Saner, 2010).
Fig. 13. The increasing market of geothermal heat pumps in Europe (Sanner, 2010).
In most leading European countries in the use of geothermal heat pumps is detected a rapid growth in the number of units set. As an example we show on Fig. 14 the trend of sales of geothermal heat pumps (GSHP) in Germany from 1996 to 2009.
Fig. 14. The number of units (GHSP) sold in Germany (Sanner, 2010).
6 LEGISLATION This chapter gives an overview of European, Slovenian in Hungarian legal framework within which the geothermal heat pumps technology is promoted and regulated.
6.1 EUROPEAN LEGISLATION Directives Legal framework for enhancing the use of heat pump technology for covering EU energy demands and emergent replacing is adopted in two European directives: Directive 2009/28/EC1 on the promotion of the use of energy from renewable sources and Directive 2010/31/EC2 on the energy performance of buildings. In accordance with Directive 2009/28/EC all Member States had to establish a national renewable energy action plan and send it to the European Commission by 30.6.2010. Contents of the RES action plan had been set by the Commission decision of 30 June 2009 on proposal for national action plans for renewable energy in accordance with Directive 2009/28/EC of the European Parliament and Council. From the viewpoint of heat pump technology for heating and cooling and domestic water preparation directive 2009/28/ES provides that the geothermal heat captured by heat pumps shall be taken for the purposes of gross final consumption from renewable sources for heating and cooling if the final energy output significantly exceeds the primary energy input required to drive the heat pumps. The quantity of heat to be considered as energy from renewable sources for the purposes of this Directive shall be calculated in accordance with the methodology laid down in Annex VII. Directive 2009/28/ES further dictates the simplifying and speeding up the licensing procedures and certificate issuance as well as the definition of technical specifications for the equipment. It also encourages the demonstrational project for production of electricity, heating or cooling from renewable energy sources and definition of minimum standards for the use of RES in the construction of new facilities. It is also regulated to financially encourage only the installation of heat pumps that fulfil the minimum requirements of eco-labelling established in Commission Decision 2007/742/EC of 9 November 2007 establishing the ecological criteria for the award of the Community eco-label to electrically driven, gas driven or gas absorption heat pumps3.
http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2009:140:0016:0062:en:PDF http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2010:153:0013:0035:EN:PDF 3 http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2009:140:0016:0062:en:PDF 2
Until 31.12.2012 is necessary to ensure the availability of the certification system or equivalent qualification systems for installers of shallow geothermal systems and heat pumps. Criteria and guidelines for the certification of installers are given in annex IV of the Directive. Each country of the European Communities must also recognize certificates issued by other countries in accordance with these criteria. Certification of installers of heat pumps and shallow geothermal systems is carried out by an accredited training program or by an accredited training provider. The installer certification should be time restricted, so that a refresher seminar or event would be necessary for continued certification. 2010/31/ES Directive on Energy Performance of Buildings requires that new buildings meet minimum energy efficiency. Measures are needed to increase the number of buildings which not only fulfil current minimum energy performance requirements, but are also more energy efficient, thereby reducing both energy consumption and carbon dioxide emissions. The responsibility of the Member States is to set the minimum requirements for the energy performance of buildings or building elements. These requirements should be set with a view to achieving the cost-optimal balance between the investments involved and the energy costs saved throughout the lifecycle of the building. For new buildings, Member States shall ensure that prior to the start of construction, is required to take into account the technical, environmental and economic feasibility of high-efficient alternative systems, if they are available. Major renovations of existing buildings, regardless of their size, provide an opportunity to take cost-effective measures to enhance energy performance. For reasons of cost-effectiveness, it should be possible to limit the minimum energy performance requirements to the renovated parts that are most relevant for the energy performance of the building. Standards The main goal of standardization is to improve quality, design, technical specifications, safety, reliability, installation procedures and lifetime of the final product. Standards, which are used for geothermal heat pumps are: European Standards (EN), which are in general normative International Standards (ISO), which are regulatory, although they should be the "best practice" and therefore followed National Standards (DIN, VDI, …)
Application of standards varies from one country to another, although every country should follow technical standards on the principle of "best practice". Standards for the heat pumps cover: 28
o general definitions, o standards for estimated capacity, efficiency and safety, o standards for installation and drilling that consider environmental requirements o standards relating to the certification of the installers and drillers, o standards for system testing, o regulations and guidelines for the approval / permitting of the systems (which usually focus on the protection of groundwater).
In the field of heat pumps many technical standards for equipment exist. EC Member States (+ Switzerland, Norway, Iceland) implemented EN standards for testing, evaluation and safety of heat pumps. There are no EN standards regarding drilling and installation of the horizontal loop systems. The existing EN standards in this area cover safety requirements for the use of drilling rigs for shallow boreholes and deep boreholes in oil industry. Technical standards for heat pumps exist only in countries in which the market is developed, such as Germany, Sweden, Austria and Switzerland. These countries have also developed a system for licensing installers and drillers. European and international standards for heat pumps are presented in the text below. Existing standards for heat pumps • EN 378-1:2000 Refrigerating systems and heat pumps – Safety and environmental requirements – Part 1: Basic requirements, definitions, classification and selection criteria • EN 14511-1:2004 Air conditioners, liquid chilling packages and heat pumps with electrically driven compressors for space heating and cooling – Parts 1-4 • ISO 13256-2:1998 Water-source heat pumps -- Testing and rating for performance -- Part 2: Water-towater and brine-to-water heat pumps Existing drilling standards, which relate to geothermal heat pumps • EN 791:1996 Drill rigs. Safety 29
• ISO 3551:1992 Rotary core diamond drilling equipment -- System A • ISO 3552:1992 Rotary core diamond drilling equipment -- System B • EN 12717:2001 Safety of machine tools. Drilling machines • EN ISO 22475/1:2006 Geotechnical investigation and testing -- Sampling methods and groundwater measurements -- Part 1: Technical principles for execution In addition to European and International standards, some countries developed their own standards to regulate the market and guidelines for installation of GSHP. This standards and guidelines are also followed by Slovenian and Hungarian installers. AT
AWP T1 SIA D 0190
SIA 384/6 (SN 565)
VDI 4640 Blatt 1-4
Thermal use of the groundwater and the underground, heating and cooling Heating system with heat pumps Use of the earth heat through foundation piles etc. Borehole heat exchangers for heating and cooling Refrigerating systems and heat pumps Protection of soil, ground and surface water Thermal use of the Underground – part 1 -4 Drilling for water wells and energy
2009 2007* 2005 2009 2002 20002009** 2008
*Switzerland: AWP T1 First guideline to call on grouting, from bottom to top of BHE **Germany: VDI 4640 VDI 4640 „Thermal Use of the Underground“ • Part 1: General / Licenses / Environment, status 2009 • Part 2: Ground Source Heat Pumps, status Dec. 2000, under revision • Part 3: UTES, status 2000 • Part 4: Direct uses (cooling, air-heat-exchanger), status 2004 EN 12828:2003 Heating systems in buildings. Design for water-based heating systems EN 12831:2003 30
Heating systems in buildings. Method for calculation of the design heat load EN 15316/4/2:2008 Heating systems in buildings. Method for calculation of system energy requirements and system efficiencies. Space heating generation systems, heat pump systems EN 15450:2007 Heating systems in buildings. Design of heat pump heating systems One important instrument for quality assurance of installed heat pumps is also quality label from European Heat pump Association – EHPA4. It originates from activities of heat pump associations of Austria, Germany and Switzerland to create a common set of requirements to ensure product and service quality for heat pumps (named D-ACH quality label after the countries country codes). The idea has been further developed in the European Heat Pump Association. In addition to the founding countries the EHPA quality label will be granted in Sweden from this year onward, other countries are considering use of EHPA quality label too.
The label can be granted to standardized space heating electrically driven heat pumps, with or without domestic hot water heating capability, with heat outputs up to 100 kW from air, geothermal or water heat sources. In order to qualify for the EHPA quality label, the heat pump in question must comply with EHPA heat pump test criteria and the distributor must provide a defined level of service. The key requirements are (list not exhaustive): a) Conformity of all main components and compliance with the national rules and regulation (CE marking) b) Minimum efficiency values defined as follows (operating points - required COP): - Brine to water B0/W35 - 4.0 - Water to water W10/W35 - 4.5 - Air to water A2/W35 - 3.0 - Direct exchange ground coupled to water E4/W35 - 4.0 c) Declaration of sound power level.
Homepage of the EHPA is www.ehpa.org
d) Existence of sales & distribution, planning, service and operating documents in the local language of the country where the heat pump is distributed. e) Existence of a functioning customer service network in the sales area that allows for a 24h reaction time to consumer complaints. f) A two year full warranty which shall include a declaration stating that the heat pump spare parts inventory will be available for at least ten years.
6.2 SLOVENIAN LEGISLATION The renewable energy sources, including heat pumps, are discussed in the next national development documents: 1. Resolution on the National energy programme5 (Official Gazette RS, no. 57/2004) 2. The National Efficiency Energy Action Plan for the period 2008-20166 contains an analysis of the current energy situation in Slovenia (the use of energy, existing measures EE and RES, the obstacles for improving energy efficiency), instruments designed to improve energy efficiency of each sector and designed contractors. 3. Renewable energy sources action plan for the period 2010 – 20207 is more recent than the National Efficiency Energy Action Plan and is entirely devoted to measures to increase the use of OVE, including heat pumps. Legislative Acts and Bylaws The requirements of Directive 2009/28/EC on the promotion of renewable energy and Directive 2010/31/EC on the energy performance of buildings are transferred to Slovenian legislation. The existing regulations are published on the website of the Ministry of Economy8. A rule on efficient use of energy in buildings9 (OG RS, no. 52/10) is based on the Directive 2010/31/ES. This rule dictates minimum requirements for achieving energy efficiency of buildings with RES. Energy efficiency of buildings is achieved when at least 25 percent of total energy needed for the operation of systems in a building is provided by the use of renewable energy. Energy efficiency is also achieved if at least 70 % of the energy needed for heating and cooling of building and hot water preparation is captured by geothermal heat pumps.
http://www.uradni-list.si/1/objava.jsp?urlid=200457&stevilka=2669 Nacionalni akcijski načrt za energetsko učinkovitost za obdobje 2008-2016 /AN-URE/ 7 http://www.mg.gov.si/fileadmin/mg.gov.si/pageuploads/Energetika/Porocila/AN_OVE_20102020_final.pdf 8 http://www.mg.gov.si/si/zakonodaja_in_dokumenti/energetika/ 9 http://www.uradni-list.si/1/objava.jsp?urlid=201052&stevilka=2856 6
In 2010 technical guideline TSG-1-004:2010 Efficient energy use10 was made, which regulated among other things, also the methodology for calculating the necessary energy for the operation of the heat pumps, required energy for heating and preparation of hot water, thermal power of the heat pumps and COP of the rated load in accordance with group standards SIST EN 14511, the calculation of heat loss and operating time of the heat pumps and heat. Rules of Construction include mandatory feasibility study of alternative systems for energy supply. This study is a mandatory component of the project for the acquisition of the building permit in accordance with the regulations on construction. The methodology and required contents of a feasibility study are prescribed in the Rules on feasibility study of alternative energy systems for energy supply in buildings11 (OG RS, no. 35/08). Installation of heat pumps type water - water is regulated under the provisions of the Water Act (ZV-1, Official Gazette RS, no. 67/02) and the Rules on the content of application for acquiring water permit and on the content of application for acquiring groundwater research permit (Official Gazette RS, no. 79/07). In accordance with this rules it is required for all wells (boreholes) in the water protection area and all wells that are more than 30 m away from the water protection area to obtain a permit for groundwater research. It is also required for the installation of a heat pump to obtain permission for the direct use of groundwater for heating purpose. The authorization procedures are described in Chapter 8 ''Procedure of geothermal heat pump technology installation in Slovenia''. For the use of groundwater for heating, water rates are not charged. The new Mining Act12 (ZRud-1, Ur. List RS, 61/10, 62/10) follows the recommendations of the Directive 2009/28/ES to simplify licensing procedures. The law itself has brought new definitions for the geothermal energy source, which is heat from geological formations under the Earth's surface and is renewed by means of heat flow from the Earth`s inside. Utilization of geothermal energy source with a ground-coupled heat exchanger or a borehole heat exchanger means that the heat removal from the geological formations is performed with a closed loop system of pipes that are installed in the borehole (vertical collector) or buried horizontally in a certain depth beneath the surface (horizontal collector). An appropriate fluid, airtight closed in such a system, is used as a carrier fluid for the thermal energy transfer (Mining law, ZRud-1, Official Gazette RS, 61/10). Exploitation of a geothermal energy source with reinjection means that the heat removal from the geological strata is carried out using two boreholes (wells), which are (not necessarily) close together on the surface and are connected to each other via heat transfer system, while in the underground geological structure they are at least 25 m apart. Groundwater is used as a carrier for the withdrawal of thermal energy. This groundwater is pumped from the aquifer through the first borehole, and after removing the heat, the water returns through the other borehole back into the original geological structure or aquifer (Mining law, ZRud-1, Official Gazette RS, 10
http://www.mop.gov.si/fileadmin/mop.gov.si/pageuploads/zakonodaja/prostor/graditev/TSG-01004_2010.pdf 11 http://www.uradni-list.si/1/objava.jsp?urlid=200835&stevilka=1429 12 http://zakonodaja.gov.si/rpsi/r06/predpis_ZAKO5706.html
61/10). Implementation of the borehole heat exchangers to a depth of 300 m is totally unregulated, but also in such cases, the boreholes should still be drilled in accordance with the rules of the mining profession (the competent department under the new Mining law must prepare new Rules on requirements for safety and health at work and technical measures for research and exploitation of mineral resources by drilling). Exploitation of geothermal energy resources with a ground-coupled heat exchanger or a borehole heat exchanger can be implemented without a license under this act, while for the exploitation of geothermal energy sources with reinjection the license for research and water permit can only be obtained in accordance with the regulations that govern the water sources. Standards There are no existing standards for installing heat pumps in Slovenia, only a group of EN standards (mostly in English only) is introduced into Slovenian legislation. Most of the relevant international and European standards are stated in paragraph 5.1 European legislation. Installers in Slovenia usually follow the standards and instructions for installation of geothermal heat pumps, which were developed in Switzerland, Germany, Sweden and Austria.
6.3 HUNGARIAN LEGISLATION There is a complicated and expensive licensing procedure for ground-coupled heatpumps. Simplification of licensing procedures and taking over the fees by the state is necessary in order to installation of the modern thermal exothermic equipment in the same market conditions could be concurrent. Some other measures should be applied too (e.g.: construction of a chimney in case of new buildings should be restricted except fireplace and bio-furnace). Effective measures: The Act LVII of 1995 on water management ― The Act XVIII of 2005 on district heating ― Government Decree No. 118/2003. (VIII. 8.) on determination of rules for calculation of the value or rather specific value of solid minerals and geothermal energy ― Government Decree No. 219/2004. (VII. 21.) on the protection of subsurface waters ― Government Decree No. 264/2004. (IX. 23.) on taking back the waste of electrical and electronic equipment ― KTM Order No. 10/1995. (IX. 28.) on enforcement of the Act LVI of 1995 on environmental protection green tax moreover environmental protection green tax of different products ― 34
Ministry of Economy and Transport Order Nr. 96/2005. (XI. 4.) GKM on regulation about construction authority procedures regarding special structures under the function of mining inspectorate ― TNM Order No. 7/2006. (V. 24.) TNM on determination of the energetic features of the buildings (this is our first measure introducing 2002/91/EC EU directive) Standards From the 1980’s onwards requirements and examinations regarding heat pumps are fixed in national and international standards. At the moment there are 21 national MSZ and MSZ EN valid standards in force (only ten is in Hungarian of them) and 6 international ISO and IEC standards (only one is domesticated of them). Most of the important international and European standards are cited in subchapter 5.1 European legislation. Hungarian installers are also inspired by standards and guidelines for GSHP installation, developed in Switzerland, Germany, Austria and Sweden.
6.4 PROBLEMS WITH REGULATION OF GSHP INSTALATION IN PRACTICE The difficulties encountered in the installation of geothermal heat pumps in Slovenia and Hungary, are the typical problems of technologies that are in the rapid initial state of development: -
implementation of the geothermal heat pumps avoiding current regulations. Therefore, is not possible to control the quality of production as well as their potential negative effect on environment, inadequate installation of low quality instruments and materials at low prices, lack of inventory or register for heat pumps, which makes impossible to calculate accurately the share of renewable energy generated by heat pumps. Therefore, these calculations cannot be included in the energy balance for Slovenia or Hungary, which is required by directive 2009/28/EC on the promotion of the use of energy from renewable sources.
7 FINANCIAL INCENTIVES SHEMES AND BURDENS FOR GHP 7.1 FINANCIAL INCENTIVES SHEMES IN SLOVENIA Support mechanisms that are available in Slovenia include the promotion/information and energy consulting as well as granting credits and subsidies for the installation of heat pumps. In the Ministry of the Economy, Directorate for Energy, sector for
efficient energy use and renewable energy sources13 is responsible for expert and related promotional tasks regarding the establishment of national programs and governmental regulations for boosting environmentally friendly and energy efficiency, use of renewable energy sources (RES) as well as the implementation of national programs to promote, colaborate and participate in programs and comply to international obligations in this field. Among other things, they finance project ENSVET14, in frame of which energy consulting offers more than 30 energy consulting offices around Slovenia provide the energy advices. EKO Fund, a Slovenian Environmental Public Fund15 is responsible for nonrefundable grants and loans for the heat pumps installation with subsidized interest rates through public tenders for households and legal persons of independent entrerpreneurs and private persons. System resources for operation of the EKO Fund are provided since January 1, 2010 from fees and allowances set out in Regulation on energy savings at final consumers (Official Gazette of RS 114/2009): ''Financial resources for the implementation of programmes to increase the efficiency of electrical energy use are provided by all costumers. They are obliged to pay a contribution to the electrical energy supplier for each individual locality of energy receiving/delivering. Financial resources for the implementation of programmes to increase the energetic efficiency of heat use from a distribution network, gas and liquid fuels, are provided by all final consumers of the aforementioned sources. They are obliged to pay a supplement to supplier. The amount of contributions and allowances is contained in Annex 1, which is a part of this ordinance. Utilization of heat from ground and groundwater with heat pumps is free of charge (concessions, water rates,). Problems may appear as a result of vague legislative solutions and bureaucratic administrative procedures.
7.2 FINANCIAL INCENTIVES SCHEMES IN HUNGARY In Hungary, it is possible to get subsidy typically only by way of application. So far, calls for proposals for promoting investments aiming at the enhancement of utilising geothermal energy were published in the 2007-2013 application period mostly in the Environment and Energy Operative Programme. Rate of subsidy regards mainly for central budgetary organizations and their institutes, enterprises, and non-profit organizations that is different by beneficiaries and regions (40-70%). Rate of subsidy varies between minimum 1 million and maximum 1 billion. Since the "geothermal" energy (according to the calls for proposals) is a way of utilisation by transporting of minimum 50 °C fluid, heat carrier and/or heat-transfer agent to the surface. According to this heat-pump systems utilising low enthalpy
http://www.mg.gov.si/si/delovna_podrocja/energetika/sektor_za_aktivnosti_ucinkovite_rabe_in_obnovlj ivih_virov_energije/ 14 http://gcs.gi-zrmk.si/Svetovanje/index.html 15 http://www.ekosklad.si/html/razpisi/main.html
ground heat from shallow or cold low temperature water do not belong to the scope of geothermal energy. Furthermore wells to be installed connecting to heat-pump technology exclusively belongs to the scope of supported activities neither. From the end of 2009, there was an opportunity to apply for subsidy in the frame of a call for proposals published in the Green Investment System, Climate Friendly Home Energy Efficiency Sub Programme. It aimed at creating heat or electricity generating capacity produced from renewable energy that can be linked to buildings (with the help of geothermal heat pumps), provided that the investment results decrease in energy consumption and. in CO2 emissions. Individuals, housing cooperatives and block of condominiums were eligible to the fund. Rate of basic fund is about 30 % and that of investment can vary between 555 000 1.47 million forint. However, this call for proposals, 6 months after publication, has been closed, due to the lack of additional allocated fund. On the one hand, this reflects the growing interest of the public in energy efficiency, but on the other hand the allocated financial resources for this purpose are little that can be one of the reasons for the slow spread of heat pump technology.
8 PROCEDURE OF GEOTHERMAL HEAT PUMP TECHOLOGY INSTALATION IN SLOVENIA
As assistance with designing of a ground-source heat pump installation in accordance with national regulations and expert standards, the professionally correct procedure of choosing and installation of a ground-source heat pump primary (earth) circuit is described and some other facts that have to be considered in the process are mentioned. The ground-source heat pump primary circuit includes drilling of a pumping and injection borehole for water-source heat pump, or the construction of horizontal or borehole heat exchanger for ground-coupled heat pump. Also lake and rivers can be used, namely in two manners, as an open-loop (much like water-source system) or a closed-loop heat pump system (much as the ground-coupled system). The procedure for ground-source heat pump installation is shown on Figure 18. What to do when planning to supply a part of energy needs with a heat pump? A suitable type of heat pump will be chosen according to heating and cooling demand calculations as well as geology and hydrogeology of the selected site and national legal regulations. We can distinguish five procedure phases: preparation phase; permits acquisition, borehole implementation, borehole utilization and additional water consent phase.
Preparation phase: 1. First of all, it has to be established if the selected site is categorised as building lot. For the installation of heat pump primary circuit only building lot is appropriate, as the construction of boreholes on agricultural land is not permitted (Spatial Planning Act, Official Gazette RS, No. 33/2007). 2. At the same time we check if the site of foreseen heat pump installation is located in water protection area. (i.e. web pages of Slovenian Environmental Agency). If the site is in the zone A of the water protection area, the heat pump is not allowed to install. (zone A of the water protection area is a spatial water reservation in which new facilities are not allowed). Water consensus has to be acquired in the other water protection areas from Slovenian Environmental Agency (ARSO). 3. In the next step an energy expert has to calculate the required heat demand and obtain key data about geology and hydrogeology of the site. This step is of utmost importance, but the key factor is the choice of an experienced energy expert (installer)16. If the energy expert over- or under-estimates the heat demand, unnecessary costs will be added and the system efficiency will be suitably 4. Based on these data appropriate type of heat pump, either water-source or ground-coupled, is chosen. 5. Project designer then determines necessary groundwater flow rate and well diameter in case of water source heat pump, and necessary pipe length of a horizontal heat exchanger or necessary borehole depth in case of groundcoupled heat pump. This calculation gives us the first estimation of investment costs. After that we could begin with acquisition of necessary permits. Permits acquisition: 6. According to the new Mining Law that will come into force on 1. January 2011 it will not be compulsory to get a mining permit for works down to the depth of 300 m in the cases of drilling boreholes for geothermal energy source utilisation in closed loop. Also the mining rights will not be necessary for the use of a geothermal energy source17. As a borehole interferes with ground 16
According to the Directive 2009/28/ES of the European Parliament and Council dated 23 April 2009 on the promotion of the use of renewable energy resources the member states must assure that certification systems or equivalent qualification systems be available to the installers of small biomass furnaces, solar fotovoltage and solar thermal systems, shallow geothermal systems and water pumps (see Article 14 and Appendix IV). (When the 2009/28/ES Directive requirements for certification of near-surface geothermal systems and heat pump installers will be fulfilled, the circumstances will be more transparent (energy experts and installers will be distinguished from sellers)). Directive 2009/28/ES is available at: http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2009:140:0016:0062:en:PDF 17
Geothermal energy resource is heat from geological formations under the Earth's surface and is renewed by means of heat flow from the Earth`s inside (Mining Law, Official Gazette RS, 61/2010).
water, it is necessary, if the well is deeper than 30 m, to get a Groundwater Research Permit (GwRP). 7. In the case that we decide to make borehole for heat utilisation from groundwater deeper than 30 m, groundwater research permit (GwRP) has to be obtained. The same is true for all boreholes in water protection areas. It is necessary to fill the application, prepare the hydrogeological report with borehole design, submit the application at Slovenian Environmental Agency (ARSO) and wait for granting of the research permit (Groundwater research permit). If the provided borehole is deeper than 300 m, it is necessary to file with the application also the revised mining project for borehole construction. (Application Form for groundwater research permit with compulsory appendices can be found at the Slovenian Environmental Agency (ARSO) website18.) 8. If it happens that borehole is in the groundwater protection area (except narrowest) the risk analysis for water source is compulsory appendix for groundwater research permit application. Risk analysis could foresee additional security measures, which the designer has to consider in designing because it can affect the investment costs. In the worst case the risk analysis can prove that the chosen heat pump installation design is not acceptable. It depends from case to case and from water protection area. Therefore, it is recommended that designer previously obtains the information from ARSO for respective water protection area. 9. In the case, that we chose the water-source heat pump technology and we use pumped water only as transfer or heat exchange, the Slovenian Environmental Agency will require that all amount of pumped water will be return to the aquifer in unchanged condition. That means that we have to make the injection borehole or injection field. If we will utilize pumped water or its part for other purposes, we have additional to obtain water permit for each purpose.
Groundwater Investigation â€“ application for groundwater investigation permit (Article 115 of the Water Act, Official Gazette RS, No. 67/02, 110/02-ZGO-1, 2/04-ZZdrI-A, 41/04-ZVO-1 in 57/08) available at: http://www.arso.gov.si/vode/vodna%20dovoljenja/.
Fig. 15. Where borehole would be? (Photo: Aleksander Bokan)
Borehole implementation: 10. In spite of the fact that no mining permit is needed for borehole heat exchangers shallower than 300 m, a technical leader of drilling works is responsible for the consistence of the constructed borehole with the mining technical documentation, technical regulations and safety and health regulations, so designing of a mining project19 for a borehole construction is recommended. 11. Groundwater research permit also describe the compulsory actions that have to be taken, such as obligation to sample the drilling debris and a coring at the borehole bottom, delivering of samples to the Geological Survey of Slovenia, conducing of pumping test, permeability measurements and borehole logging. Contractor must file the research report latest 30 days after termination of research. It is obligatory both for boreholes for water-source heat pumps and ground-coupled heat pumps.
Hydrocarbon exploration and geothermal energy sources utilisation borehole is a point surface pit with underground exploitation of a mineral resource (Mining Law, Official Gazette RS, 61/2010).
Fig. 16. Positioning of the drilling rig (Photo: Aleksander Bokan)
12. After the borehole is constructed all necessary measurements are performed to determine if the constructed borehole fits expected characteristics and design requirement. Testing should be made according to the requirements of the groundwater research permission and manual for pumping and injection tests for heat pumps20.
Pumping test instructions are available at: http://www.arso.gov.si/vode/vodna%20dovoljenja/.
Fig. 17. Activation of the pumping well (Photo: Aleksander Bokan)
Borehole utilization: 13. For geothermal energetic source utilisation as a ground-coupled system we donâ€™t need any permits. 14. The next step is to fill the application form for acquiring water permit for direct use of water for heat use (when source is not a thermal aquifer) 21. According to the instructions that can be obtained at the ARSO website, a minimum hydrogeological report has to be made when the scheduled water use is less than 2 l/s, or hydrogeological report in case of higher scheduled use. Contractor should prepare already the hydrogeological research report in such a form, that it could be used for water permit application. 15. Other compulsory administrative appendices stated in the application for water permit for use of ground water for heat utilization must also be presented. 21
Water Permit â€“ application for water permit for direct use of water for generation of heat (when the aquifer is not thermal aquifer) (Article 125 of the Water Act, Official Gazette RS, No. 67/02, 110/02zgo-1, 2/04-zzdri-a, 41/04-zvo-1 in 57/08) is available at: http://www.arso.gov.si/vode/vodna%20dovoljenja/.
16. After the water permit is issued, the well can be utilised. If groundwater pumping rate is higher than 2 l/s, monitoring of groundwater usage22 has to be established and annual reporting to ARSO is obligatory. Water consent: 17. In cases, when construction work is intended, for which a building permit under the construction regulations is not required to obtain, but a water consent under the Water Act must be obtain, the entity or individual intending to carry out construction work must obtain the conditions, which planned activity has to comply with (hereinafter referred to as conditions for other construction works) before the start of the work. Those conditions relate to the protection of water, water management, protection of the natural balance of aquatic and riparian ecosystems, and existing water rights of others. For the intervention, which may cause an impact on groundwater, especially recharge of the aquifer or in particular the reinjection of water into the aquifer, it is necessary to obtain a water consent23 for the drilling of pumping and reinjection wells (simple construction works) in the local ARSO department. Water consent is issued based on a valid groundwater research permit. 18. Based on the issued water permit for direct use of water for heat use (when source is not a thermal aquifer), water permit to use the facility must be obtained from the local ARSO department.
Groundwater monitoring report form is available at: http://www.arso.gov.si/vode/vodna%20dovoljenja/porocilo-odvzemi.xls). 23
Forms for aquisition of water consent are available at: http://www.arso.gov.si/vode/Urejanje%20voda/Vodno%20soglasje/
Fig. 18. Heat pump installation procedure in Slovenia
9 SOURCES Banks, D., 2008. An introduction to thermogeology: Ground source heating and cooling. Oxford: Blackwell Publishing, 339p. Gosar, A. & Ravnik, D., 2007: Uporabna geofizika. Naravoslovnotehniška fakulteta, Oddelek za geotehnologijo in rudarstvo, Univerza v Ljubljani, 218p.., Ljubljana. Heap, R.D., 1979: Heat pumps. 155p. E & F.N. Spon Ltd., London. IOVE, 2009: Raba energije Zemlje in podzemnih voda. Avstrijski predlog pravne ureditve. Dukič B. (ured.), študijsko gradivo, zbirka Modro Sonce, IOVE, Kranj, 52p. Lund, J.W., 2000: Ground-source (geothermal) heat pumps. V: P.J Lienau (conv.), Course on »Heating with geothermal energy: Conventional and new schemes«. WGC2000 Short Courses, Kazuno, Japan, 209-236. Lund, J.W., 2008: Characteristics, development and utilization of geothermal resources. Geothermal (ground-source) heat pumps. Interactive Seminar – Workshop 26: Geothermal fields development, e-Proceedings, PESS, June 9-13, Dubrovnik. Sanner, B., 2010: GeoTrainet 01: Overview shallow geothermal systems. 05: Basics on geology – what engineers and drillers need to know. GeoTrainet Course for designers and drillers, Peine, Germany, 17.-19..3.2010. Struckmeier, W.F. & Margat, J. 1995: Hydrogeological Maps: A guide and a standard legend: international contributions to hydrogeology, volume 17, 177p. International Association of Hydrogeologists. Verlag Heinz Heise, Hannover.
10 RELEVANT INTERNET SOURCES Vast amount of additional information about geothermal heat pumps is available on internet. Only few of them, with the relevant data about GSHP, are listed below: Wiki (general about heat pumps) http://en.wikipedia.org/wiki/Heat_pump http://en.wikipedia.org/wiki/Geothermal_heat_pump European Geothermal Energy Council (EGEC): http://www.egec.org/ International Ground Source Heat Pump Association (IGSHPA): http://www.igshpa.okstate.edu European Heat Pump Network: http://www.ehpn.de/en/
IEA Heat Pump Programme http://www.heatpumpcentre.org/en/aboutHPP/Sidor/default.aspx European heat pump Association (EPHA): http://www.ehpa.org German heat pump association (Bundesverband WärmePumpe Deutschland - BWP) http://www.waermepumpe.de Austrian heat pump association (Bundesverband WärmePumpe Austria - BWP) http://www.bwp.at/ Switzerland heat pump association (Fördergemeinschaft Wärmepumpen Schweiz - FWS) http://www.fws.ch/ Homepage of Geothermal Technologies Program (USA) http://www1.eere.energy.gov/geothermal/heatpumps.html
Published on Oct 5, 2010
Screening of the geothermal utilization, evaluation of the thermal groundwater bodies and preparation of the joint aquifer management plan i...