Best Practice Catalogue on Successful Running Solar Air-Conditioning Appliances

Transcription

1 on Successful Running Solar Air-Conditioning Appliances

2 EIE/06/034/SI SOLAIR Work package 2: Market review and analysis of small and medium sized solar air-conditioning (SAC) applications Task 2.2: Preparation of a web based database of best available examples December 21, 2009 Version 2.0 Update of Version 1.0, published June 30, Introduction Technologies Chilled water systems Open cycle processes Solar thermal collectors SOLAIR database of solar cooling and air-conditioning SOLAIR Best Practice Examples Best Practice Examples: AUSTRIA Best Practice Examples: FRANCE Best Practice Examples: GERMANY Best Practice Examples: GREECE Best Practice Examples: ITALY Best Practice Examples: PORTUGAL Best Practice Examples: SPAIN Solar cooling: examples on advanced approaches... 71

3 This report was edited by: Edo Wiemken, Fraunhofer ISE SOLAIR is co-ordinated by target GmbH, Germany Partners in the SOLAIR consortium: AEE Institute for Sustainable Technologies, Austria Fraunhofer Institute for Solar Energy Systems ISE, Germany Instituto Nacional de Engenharia, Technologia e Innovação INETI, Portugal Politecnico di Milano, Italy University of Ljubljana, Slovenia AIGUASOL, Spain TECSOL, France Federation of European Heating and Air-conditioning Associations RHEVA, The Netherlands Centre for Renewable Energy Sources CRES, Greece Ente Vasco de la Energia EVE, Spain Provincia di Lecce, Italy Ambiente Italia, Italy SOLAIR is supported by The sole responsibility for the content of this report lies with the authors. It does not necessarily reflect the opinion of the European Communities. The European Commission is not responsible for any use that may be made of the information contained therein 2

4 1 Introduction In nearly all European countries, a strong increase in the demand for building cooling and air-conditioning is detected and predicted for the following decades. The reasons for this general increase are manyfold, such as an increase in comfort habits, currently still low energy costs, architectural trends like an increased fraction of glazed areas in buildings and last but not least slowly changing climate conditions. This rising demand for cooling and air-conditioning in buildings involves unfavourable fossil fuel consumptions as well as upcoming stability problems in the electrictity supply in mediterraenean countries, which in turn demands for costly upgradings of the grids to handle electricity peak power demand situations. Thus, improved building concepts, targeting on reduction of cooling loads by passive and innovative measures, and the use of alternatives in coverage the remaining cooling demands of buildings, are of interest. Solar driven or assisted cooling is one of the possibilities to provide acively cold. In the context of the SOLAIR project, solar cooling or solar air-conditioning is used for solar thermally driven processes. Solar cooling in this sense may contribute to - replacement of fossil fuel demand by use of solar heat and by this, contributing to the European policy targets on the increased use of renewable energies; - reduction of greenhouse effect emmissions through both, savings in primary energy and avoidance of environmental harmful refrigerants; - support in stability of electricity grids by less electrictiy energy and peakpower demand; - optimized use of solar thermal systems through use of solar heat for combined assistance of space heating, cooling and domestic hot water preparation. The SOLAIR project provides several materials on solar cooling, adressing different levels on information. Within this catalogue, Best Practice examples from the SOLAIR database are presented. Many of this examples went into operation less than one or two years before the compilation of this catalogue, long term operation experience can not be expected so far. Thus, the definition Best Practice refers here to an appropriate system concept and to promising approaches of solar cooling. The catalogue aims to present the applicability of solar cooling technologies within different building environments, at different locations and with different technical solutions. In the beginning, a brief review on solar cooling technologies is presented. More information on the SOLAIR database is provided in the Cross-country report of the review of available technical solutions and successful running systems, prepared in SOLAIR and accessible at 3

5 2 Technologies The focus in SOLAIR is on solar cooling and air-conditioning systems in the small and medium size capacity range. The classification into small and medium aligns with available chiller products; small applications are in this sense systems with a nominal chilling capacity below 20 kw, and medium size systems may range up to approx. 100 kw. Systems in the small capacity range are usually consist of thermally driven chilled water systems, whereas medium sized systems may be open cycle desiccant evaporative (DEC) cooling systems as well. While in the first type of system technology the distribution medium is chilled water in a closed loop to remove the loads from the building, in the latter one supply air is directly handled in humidity and temperature respectively in an open process. Figure 2.1 visualises the two general types of applications. Of course, applications using both types of technology at the same time are possible. In chilled water systems, the central cold water distribution grid may serve decentralised cooling units such as fan coils (mostly with dehumidification), chilled ceilings, walls or floors; but the chilled water may be used for supply air cooling in a central air handling unit as well. The required chilled water temperature depends on this type of usage and is important for the system design and configuration, but the end-use devices are not in the focus of SOLAIR and thus are not presented more in detail. Figure 2.2 illustrates that any thermally driven cooling process operates at three different temperature levels: with driving heat Q heat supplied to the process at a temperature level of T H, heat is removed from the cold side thereby producing the useful cold Q cold at temperature T C. Both amounts of heat are to be rejected (Q reject ) at a medium temperature level T M. The driving heat Q heat may be provided by an appropriate designed solar thermal collector system, either alone or in combination with auxiliary heat sources. While in open cycle processes the heat rejection is with the air flow in the system integrated into the process, closed chilled water processes require for an external heat rejection system, e.g., a cooling tower. The type of the heat rejection system is currently turning more into the field of vision, as this component usually is responsible for a considerable fraction of the remaining energy consumption of solar cooling systems. A basic number to quantify the thermal process quality is the coefficient of performance COP, defined as COP = Q cold / Q heat, thus indicating the amount of required heat per unit produced cold (more accurately: per unit removed heat). The COP and the chilling capacity depends strongly on the temperature levels of T H, T C and T M. This dependency is discussed more in detail in e.g. [Henning, 2006]. In market available products of thermally driven chillers, the COP ranges at rated operation conditions from 0.5 to 0.8 in single-effect machines and up to 1.2 in double-effect machines. 4

6 In open cycle desiccant cooling systems, the COP is more difficult to assess, since it depends more strongly on the system operation. It is useful, to define here the COP for the desiccant operation mode only, since in this operation mode heat is required. Experiences from DEC plants have shown that COP values comparatively to single-effect chillers may be achieved. ~18 C Chilled ceiling Heat > 60 C Supply air Thermally driven Chiller 16 C - 18 C (< 12 C) 6 C - 9 C Chilled water temperature Fan coil Cooled / Conditioned area Heat > 50 C Return air Supply air Desiccant evaporative cooling (DEC) Conditioned area Figure 2.1 General types of thermally driven cooling and air-conditioning technologies. In the figure above, chilled water is produced in a closed loop for different decentral applications or for supply air cooling. In the figure below, supply air is directly cooled and dehumidified in an open cycle process. Source: Fraunhofer ISE. The technologies are outlined more in detail below. Heat is required in both technologies, to allow a coninuous system operation. In the applications surveyed in SOLAIR, the heat is at least to a significant part produced by a solar thermal collector system. Q heat T H T M Q reject T C Q cold Figure 2.2 Basic scheme of a thermally driven cooling process. 5

7 2.1 Chilled water systems Absorption chillers The dominating technology of thermally driven chillers is based on absorption. The basic physical process consists of at least two chemical components, one of them serving as refrigerant and the other as the sorbent. The main components of an absorption chiller are shown in figure 2.3. The process is well documented, e.g., in [ASHRAE, 1988]; thus, details will be not presented here. The majority of absorption chillers use water as refrigerant and liquid lithiumbromide as sorbent. Typical chilling capacities are in the range of several hundred kw. Mainly, they are supplied with waste heat, district heat or heat from cogeneration. The required heat source temperature is usually above 85 C and typical COP values are between 0.6 and 0.8. Until a few years ago, the smallest machine available was a Japanese product with a chilling capacity of 35 kw. Double-effect machines with two generators require for higher driving temperatures > 140 C, but show higher COP values of > 1.0. The smallest available chiller of this type shows a capacity of approx. 170 kw. With respect to the high driving temperatures, this technology demands in combination with solar thermal heat for concentrating collector systems. This is an option for climates with high fractions of direct irradiation. hot water (driving heat) cooling water GENERATOR CONDENSER ABSORBER EVAPORATOR cooling water chilled water Figure 2.3 Scheme of a thermally driven absorption chiller. Compared to a conventional electrically driven compression chiller, the mechanical compression unit is replaced by a thermal compression unit with absorber and generator. The cooling effect is based on the evaporation of the refrigerant (e.g., water) in the evaporator at low pressure. Due to the properties of the phase change, high amounts of energy can be transferred. The vaporised refrigerant is absorbed in the absorber, thereby diluting the refrigerant/sorbent solution. Cooling is necessary, to run the absorption process efficient. The solution is continuousely pumped into the generator, where the regeneration of the solution is achieved by applying driving heat (e.g., hot water). The refrigerant leaving the generator by this process condenses through the application of cooling water in the condenser and circulates by means of an expansion valve again into the evaporator. 6

8 Figure 2.4a Examples of small absorption chillers using water as refrigerant and Lithium-Bromide as sorption fluid. Left: air-cooled chiller with a capacity of 4.5 kw of the Spanish manufacturer Rotartica. Middle: 10 kw Chiller with high part-load efficiency and overall high COP of the German manufacturer Sonnenklima. Right: Chiller with 15 kw capacity, manufactured by the German company EAW; this machine is also available in capacities of 30 kw, 54 kw, 80 kw and above. Sources: Rotartica, Sonnenklima, EAW. Figure 2.4b Further examples of absorption chillers. Left: Ammonia-water Absorption chiller with 12 kw chilling capacity of the Austrian company Pink. Middle: This chiller uses water as refrigerant and Lithium-Chloride as sorption material. The crystallisation phase of the sorption material is also used, effecting in an internal energy storage. The capacity is approx. 10 kw; the machine is developed by ClimateWell, Sweden, and can operate as heat pump as well. Right: Absorption chiller with the working fluid H 2 O/LiBr and a capacity of 35 kw from Yazaki, Japan. This chiller is often found in solar cooling systems, since it was for several years the smallest in Europe available absorption chiller, applicable with solar heat. Currently, a smaller version with 17.5 kw chiller capacity from this manufacturer has entered the European market. Sources: Pink, ClimateWell, Yazaki. Recently, the situation has changed due to a number of new chiller products in the small and medium capacity range, which have entered the market. In general, they are designed to be operated with low driving temperatures and thus 7

9 applicable for stationary solar thermal collectors. The lowest chiller capacity available is now approx. 10 kw. Some examples of small and medium size absorption chillers are given in figure 2.4. In addition to the traditional working fluids H 2 O/LiBr, also H 2 O/LiCl and NH 3 /H 2 O are applied. The application of the latter working fluid with Ammonia as refrigerant ist relatively new for building cooling, as this technology was dominantly used for industrial refrigeration purposes below 0 C in large capacities. An advantage of this chiller type is especially given in applications, where a high temperature lift (T M T C ) is necessary. This is for example the case in areas with water shortage, when dry cooling at high ambient temperatures has to be applied. Adsorption chillers Beside processes using a liquid sorbent, also machines using solid sorption materials are available. This material adsorbs the refrigerant, while it releases the refrigerant under heat input. A quasi-continuous operation requires for at least two compartments with sorption material. Figure 2.5 shows the components of an adsorption chilller. Market available systems use water as refrigerant and silica gel as sorbent, but R&D on systems using zeolithes as sorption material is ongoing. CONDENSER cooling water 2 1 cooling water hot water (driving heat) EVAPORATOR chilled water Figure 2.5 Scheme of an adsorption chiller. They consist basically of two sorbent compartments 1 and 2, and the evaporator and condenser. While the sorbent in the first compartment is desorbing (removal of adsorbed water) using hot water from the external heat source, e.g. the solar collector, the sorbent in the second compartment adsorbs the refrigerant vapour entering from the evaporator; this compartment has to be cooled in order to increase the process efficiency. The refrigerant, condensed in the cooled condenser and transferred into the evaporator, is vaporised under low pressure in the evaporator. Here, the useful cooling is produced. Periodically, the sorbent compartment are switched over in their functions from adsorption to desorption. This is usually done through a switch control of external located valves. To date, only few manufacturers from Japan, China and from Germany produce adsorption chillers; a German company is with a small unit of 5.5 kw capacity on the market since 2007 and has increased the rated capacity in an improved versions to 8 and 15 kw (model of 2009). In 2009, a second German manufac- 8

10 turer entered the market with adsorption chillers in a simila capactiy range. Typical COP values of adsorption chillers are An advantage of the chillers are the low driving temperatures, beginning from 60 C, the absence of a solution pump and a comparatively noiseless operation. Figure 2.6 shows as an example two adsorption chillers. Figure 2.6 Examples of adsorption chillers. Left: Chiller with 70 kw capactiy of the Japanese manufacturer Nishiyodo. Adsorpition chillers of similar medium capacity are available from the Japanese manufacturer Mayekawa as well. Right: Small-size adsorption chilller with approx. 7.5 kw capacity from SorTech company, Germany. An overview on closed cycle water chillers is given in [Mugnier et al., 2008] 2.2 Open cycle processes While thermally driven chillers produce chilled water, which can be supplied to any type of air-conditioning equipment, open cooling cycles produce directly conditioned air. Any type of thermally driven open cooling cycle is based on a combination of evaporative cooling with air dehumidification by a desiccant, i.e., a hygroscopic material. Again, either liquid or solid materials can be employed for this purpose. The standard cycle which is mostly applied today uses rotating desiccant wheels, equipped either with silica gel or lithium-chloride as sorption material. All required components are standard components and have been used in air-conditioning and air-drying applications for buildings or factories since many years. The standard cycle using a desiccant wheel is shown in figure 2.7. The application of this cycle is limited to temperate climates, since the possible dehumidification is not high enough to enable evaporative cooling of the supply air at conditions with far higher values of the humidity of ambient air. For climates like those in the Mediterranean countries therefore other configurations of desiccant processes have to be used. Systems employing liquid sorption materials which have several advantages like higher air dehumidifiation at the same driving temperature and the possibility of 9

11 high energy storage by means of concentrated hygrocopic solutions are now market available and offered by few companies. Several demonstration projects were carried out in order to test the applicability of this technology for solar assisted air conditioning. A possible general scheme of a liquid desiccant cooling system is shown in figure 2.8. backup heater humidifier return air 7 6 cooling loads supply air dehumidifier wheel heat recovery wheel Figure 2.7 Scheme of a solar thermally driven solid Desiccant Evaporative Cooling system (DEC), using rotating sorption and heat recovery wheels (source: Fraunhofer ISE) and below: sketch of the DEC unit (source: Munters). The successive processes in the air stream are as follows: 1 2 sorptive dehumidification of supply air; the process is almost adiabatic and the air is heated by the adsorption heat released in the matrix of the sorption wheel 2 3 pre-cooling of the supply air in counter-flow to the return air from the building 3 4 evaporative cooling of the supply air to the desired supply air humidity by means of a humidifier 4 5 the heating coil is used only in the heating season for pre-heating of air 5 6 small temperature increase, caused by the fan 6 7 supply air temperature and humidity are increased by means of internal loads 7 8 return air from the building is cooled using evaporative cooling close to the 8 9 saturation line the return air is pre-heated in counter-flow to the supply air by means of a high efficient air-to-air heat exchanger, e.g. a heat recovery wheel 9 10 regeneration heat is provided for instance by means of a solar thermal collector system 10

12 10 11 the water bound in the pores of the desiccant material of the dehumidifer wheel is desorbed by means of the hot air exhaust air is blown to the environment by means of the return air fan. Regenerator regeneration air Q H concentrated solution driving heat LiCl/water solution storage supply air Absorber Q M rejected heat diluted solution Figure 2.8 General scheme of a liquid desiccant cooling system. The supply air is dehumidified in a special configured spray zone of the absorber, where a concentrated salt solution is diluted by the humidity of the supply air. The process efficiency is increased through heat rejection of the sorption heat, eg., by means of indirect evaporative cooling of the return air and heat recovery. A subsequent evaporative cooling of the supply air may be applied, if necessary (heat recovery and evaporative cooling is not shown in the figure). In a regenerator, heat e.g. from a solar collector is applied, to concentrate the solution again. The concentrated and diluted solution may be stored in high energy storages, thus allowing a decoupling in time between cooling and regeneration to a certain extent. Source: Fraunhofer ISE. In general, desiccant cooling systems are an interesting option if centralized ventilation systems are used. At sites with high latent and sensible cooling loads, the air-conditioning process can be splitted into dehumidification by means of a thermally driven open cycle desiccant process, and an additional chilled water system to maintain the sensible loads by means of e.g. chilled ceilings with high chilled water temperatures, in order to increase the efficiency of the chilled water production. More details on open cycle processes are given in [Henning, 2004/2008] and in [Beccali, 2008]. 2.3 Solar thermal collectors A broad variety of solar thermal collectors is available and many of them are applicable in solar cooling and air-conditioning systems. However, the appropriate type of the collector depends on the selected cooling technology and on the site conditions, i.e., on the radiation availability. General types of stationary collectors are shown in figure 2.9. The use of cost-effictive solar air collectors in flat plate construction is limited to desiccant cooling systems, since this technology requires the lowest driving temperatures (starting from approx. 50 C) and allows under special conditions the operation without thermal storage. To operate thermally driven chillers with solar heat, at least flat plate collectors of high quality (selective coating, improved insulation, high stagnation safety) are to be applied. 11

13 Not shown in the figure are concentrating and tracked collectors, which may be applied to supply heat at a medium temperature level above 100 C and below 200 C in order to drive e.g. double-effect chillers or ammonia-water chillers for a high temperature lift. glas cover insulation collector frame absorber with air channels solar air collector glass cover flat plate collector insulation absorber with fluid channels collector frame glass cover CPC collector reflector insulation absorber with fluid channel collector frame evacuated tube collector evacuated tube evacuated glass tube optionally: reflector Absorber with fluid channel (forward/return) Figure 2.9 Examples of stationary collectors, applicable for solar cooling. Source: SOLAIR didactic material base / Fraunhofer ISE. More technical information on solar cooling technologies and components can be found in the Guidelines Requirements on the design and configuration of small and medium sized solar air-conditioning (SAC)applications, accessible at 3 SOLAIR database of solar cooling and airconditioning Within SOLAIR, data from successful running applications on solar cooling and air-conditioning in the small and medium cooling capacity range were collected. Table 3.1 summarises briefly the content of this database. More details are given in the Cross-country analysis report of the database within SOLAIR [SOLAIR: Review technical solutions, 2009]. The Best Practice Examples, presented in the following section, are extracted from this database. 12

14 Type of application Counts in database Technology Chilling capacity range [kw] Country Hospital (& retired people building) 1 Ab 10 FR Laboratory (for public hospital) 1 Ad 70 DE Public library 1 DEC 81 ES Public office 3 DEC liq, DEC DE, AT, PT Public seminar area (College) 1 Ab 20 DE Other public 2 Ad, DEC DE, GR Commercial office 12 Ab 9-70 AT, FR, DE, GR, IT, PT, ES Comercial hotel 1 Ab 105 GR Commercial seminar area 1 DEC 60 DE Commercial wine storage 1 Ab 52 FR Other commercial 1 Ab 35 ES Residential 3 Ab, Ad AT, IT, ES total: 28 Table 3.1 Type of application, technology, cooling capacity and distribution by country of the sytems in the SOLAIR data base. Abbreviations: Ab = Absorption; Ad = Adsorption; DEC = Desiccant Evaporative Cooling; DEC liq = liquid desiccant cooling. 4 SOLAIR Best Practice Examples Many of the Best Practice examples presented in the following went into operation less than one or two years before the compilation of this catalogue, long term operation experience can not be expected so far for this reason. Thus, the definition Best Practice refers here to an appropriate system concept, successful operation and to advanced and promising approaches of solar cooling. The catalogue aims to present the applicability of solar cooling technologies within different building environments, at different locations and with different technical solutions. The examples are transferred into this catalogue according to their presentation at the SOLAIR web page. In some examples, more information is available in an additional file, indicated right hand of the example and accessible for download from the web page. 13

15 4.1 Best Practice Examples: AUSTRIA Examples presented at the following pages: 1. Ökopark, Hartberg 2. Bachler, Gröbming 3. SOLution, Sattledt 4. Residential Building, Thening 14

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17 View at the Ökopark Hartberg, Austria 16

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19 Components of the Ammonia/Water chiller, installed at the Bachler system, Gröbming, Austria. Source: PINK Energie- und Speichertechnik. 18

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21 Scheme of the solar cooling system at Sattledt, Austria 20

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23 4.2 Best Practice Examples: FRANCE Examples presented at the following pages: 1. Résidence du Lac, Maclas 2. GICB building, Banyuls sur Mer 3. CNRS PROMES Research Center Office, Perpignan 22

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25 Scheme of the solar cooling system at Maclas, France Sc 24

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30 4.3 Best Practice Examples: GERMANY Examples presented at the following pages: 1. Fraunhofer ISE, Freiburg 2. University Hospital, Freiburg 3. Chamber of Commerce Südlicher Oberrhein (IHK-SO), Freiburg 4. Office building of Ott Ingenieure, Langenau 5. Solar Info Center SIC, Freiburg 6. Office building of IBA AG, Fürth 7. Technical College for Engineering, Butzbach 29

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32 Solar cooling system at Fraunhofer ISE in Freiburg, Germany. Top: cooling operation during summer. Bottom: heat pump operation during winter. 31

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34 Vacuum tube collectors 81 m² Local steam network 90 m² Solar circuit Heating circuit 2 flap bypass Solar heat storage Cooling circuit Closed wet cooling tower Water / air heat exchanger ventilation system A/Csupply valve Winter heating circuit Buffer storage flap storage Heating circuit 1 Cold storage Adsorption chiller 70 kw Chilled water circuit secondary Chilled water circuit primary Scheme of the solar cooling system at the University hospital laboratory building, Freiburg, Germany 33

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36 Scheme of the Desiccant Evaporativ Cooling (DEC) system at IHK-SO, Freiburg, Germany 35

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38 Heat production sub-system of the solar cooling system at Ott Ingenieure, Langenau, Germany 37

39 Cold production sub-system of the solar cooling system at Ott Ingenieure, Langenau, Germany 38

40 Solar Info Center SIC, Freiburg, Germany To be continued at the following page 39

41 Installed solar driven liquid desiccant evaporative cooling system and scheme of the system at the Solar Infor Center (SIC), Freiburg, Germany 40

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43 Scheme of the solar cooling system at IBA AG, Fürth, Germany 42

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45 Scheme of the solar autonomous cooling system at the Technical College for Engineering in Butzbach, Germany 44

46 4.4 Best Practice Examples: GREECE Examples presented at the following pages: 1. Center for Renewable Energy Sources, Koropi 2. Promitheus building Sol Energy Offices, Palaio Faliro 3. Rethymno Village Hotel, Crete 45

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48 Scheme of the solar driven desiccant evaporative cooling system at Lavrio/Koropi, Greece 47

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50 Scheme of installations of the solar energy building in Palaio Faliro, Greece 49

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53 4.5 Best Practice Examples: ITALY Examples presented at the following pages: 1. Manufacturing area, Bolzano 2. Residential building, Milan 3. ISI Pergine business center, Trento 52

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55 Scheme of the solar cooling system in Bolzano, Italy. Top: cooling operation mode in summer; bottom: heating mode in winter 54

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58 Scheme of the cold production and cold distribution system at Trento, Italy 57

59 4.6 Best Practice Examples: PORTUGAL Examples presented at the following pages: 1. INETI building, Lisbon 2. Office building Vajra, Loulé 58

60 To be continued at the following page 59

61 Scheme of the desiccant evaporative cooling system (top) and of the solar / auxiliary heating sub-system (bottom) at the Ineti building, Lisbon, Portugal 60

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63 4.7 Best Practice Examples: SPAIN Examples presented at the following pages: 1. Pompeu Fabra Library, Mataró 2. Headquarter building of CARTIF, Valladolid 3. Agència de la salut pública, Barcelona 4. Residential solar cooling and heating, Derio 62

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65 Scheme of the desiccant evaporative cooling system (DEC) in the public library at Mataró, Spain 64

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69 Scheme of the system at a laboratory building in Barcelona, Spain. The summer operation mode is shown. 68

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71 Scheme of the residential solar cooling and heating system in Derio, Spain. 70

72 5 Solar cooling: examples on advanced approaches The majority of installed solar cooling systems use stationary solar thermal collectors, either of flat-plate type or evacuated tube collectors as shown in section 2.3. These collectors are sufficient to provide driving heat for the type of cooling technologies as presented in the examples of section 4. However, there are reasons for the application of advanced cooling technologies, requiring for driving temperatures above 100 C, to maintain the chilling process. Some of the reasons are: - the irradiation conditions at the site are favourable, to allow the operation of high efficient thermally driven cooling processes, e.g., the application of a double-effect absorption chiller. The higher thermal coefficient of performance of values > 1.0 allows to decrease the solar thermal collector capacity as well as to decrease the heat rejection system significantly. Driving heat has to be provided at temperature levels typically > 150 C; - the system is used in an industrial or commercial application and cold is required for process cooling at temperature levels below the typical levels for building air-conditioning (e.g., < 0 C). Then, thermally driven chillers with ammonia-water as working fluid pair can be applied, but requiring for higher driving temperatures than for building air-conditioning; - water consumption of the heat rejection system may be a critical point in some mediterranean areas; thus, only dry cooling can be applied, resulting in heat rejection temperatures above 40 C. Consequently, a high temperature lift from chilled water temperature level to the heat rejection level has to be maintained. An appropriate technology in this case again is a thermally driven chiller with ammonia-water as working fluid, operated at driving temperatures > 100 C. The latter type of application is the subject of the ongoing project MEDISCO [MEDISCO, 2006], co-ordinated by the Politecnico di Milano and carried out with additional European partners from Tunesia and Marocco. The project is supported by the European Commission. In this project, two systems will be demonstrated using linear concentrating collector technologies in combination with NH 3 /H 2 0 absorption chillers for process cooling of a winery in Tunesia and of a dairy in Marocco. The first system went into operation in April For the first reason mentioned above, a demonstration system was recently installed at the University of Sevilla, Spain. A linear concentrating Fresnel collector is installed at the roof of the Escuela Superior de Ingenieros (ESI) of the Faculty of Engineering. The aperture area of the collector is 352 m², the rated thermal capacity is 176 kw. Figure 5.1 shows the construction principle of this collector, which was supplied by the company PSE, Germany: lines of primary mirrors are individually single-axis tracked in order to focus the irradiation towards a stationary receiver, located in a support above the mirrors. The receiver is equipped with a secondary reflector in order to minimize radiation losses. Advantages of this collector technology are the low wind-resistance and the a high surface co- 71

73 verage. Both allows for the installation at flat roof tops, e.g. on commercial or industrial buildings. The collector provides pressurised hot water at a temperature of approx. 170 C to the double-effect chiller with a rated chilling capacity of 174 kw in this application. This is currently the double-effect chiller with the smallest rated chilling capacity, delivered by the manufacturer Broad, China. Heat rejection is done in this installation with river water, runnng throgh an external heat exchanger, thus no cooling tower is applied. More information on this type of installations are given in [Zahler, 2008]. Figure 5.1 The Fresnel collector at the University of Sevilla is the solar heat source for the double-effect chiller. Top: the primary mirrors are moved off focus; a simple method to avoid stagnation problems. Bottom: view at the collector primary mirrors. Right: the double-effect absorption chiller. Sources: AICIA, Seville (top and right), PSE, Germany (bottom) 72

74 References [Henning, 2006] Hans-Martin Henning: Solar cooling and air-conditioning thermodynamic analysis and overview about technical solutions. Proceedings of the EuroSun 2006, held in Glasgow, UK, June, [ASHRAE, 1988] ASHRAE handbook (1988) Absorption Cooling, Heating and Refrigeration Equipment; Equipment Volume, Chapter 13. [Henning, 2004/2008] Hans-Martin Henning (Ed.): Solar-Assisted Air-Conditioning in Buildings A Handbook for Planners. Springer Wien/NewYork. 2 nd revised edition 2008; ISBN [Mugnier et al., 2008] D. Mugnier, M. Hamdadi, A. Le Denn: Water Chillers Closed Systems for Chilled Water Production (Small and Large Capacities). Proceedings of the International Seminar Solar Air-Conditioning Experiences and Applications, held in Munich, Germany, June 11 th, [Beccali, 2008] Marco Beccali: Open Cycles Solid- and Liquid-based Desiccant Systems. Proceedings of the International Seminar Solar Air-Conditioning Experiences and Applications, held in Munich, Germany, June 11 th, [SOLAIR: Review technical solutions, 2009]. Task 2.1: Review of available technical solutions and successful running systems. Cross Country Analysis. Public accessible report in SOLAIR. [MEDISCO, 2006] Mediterranean food and agro industry applications of solar cooling technologies. Contract (EU-INCO). Co-ordination: Politcnico di Milano, Italy. Duration: [Zahler, 2008] Chr. Zahler, A. Häberle, F. Luginsland, M. Berger, S. Scherer: High Teperature System with Fresnel Collector. Proceedings of the International Seminar Solar Air-Conditioning Experiences and Applications, held in Munich, Germany, June 11 th,

75 Supported by The sole responsibility for the content of this publication lies with the authors. It does not necessarily reflect the opinion of the European Communities. The European Commission is not responsible for any use that may be made of the information contained therein.