This document provides an overview of solar air conditioning technologies and best practice examples from several European countries. It describes two main types of solar cooling systems: chilled water systems and open cycle desiccant cooling systems. Chilled water systems use absorption or adsorption chillers to produce chilled water for air conditioning, while open cycle systems directly condition the supply air. The document outlines the technologies used in small and medium sized solar cooling applications and provides examples of installed systems in Austria, France, Germany, Greece, Italy, Portugal, and Spain.
2. EIE/06/034/SI2.446612 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
Best Practice Catalogue
June 30, 2008
Version 1.0
1 Introduction ............................................................................. 3
2 Technologies ............................................................................ 4
2.1 Chilled water systems.................................................... 6
2.2 Open cycle processes .................................................... 9
2.3 Solar thermal collectors ............................................... 11
3 SOLAIR database of solar cooling and air-conditioning.................. 12
4 SOLAIR Best Practice Examples ................................................ 13
4.1 Best Practice Examples: AUSTRIA ................................. 14
4.2 Best Practice Examples: FRANCE................................... 21
4.3 Best Practice Examples: GERMANY ................................ 28
4.4 Best Practice Examples: GREECE................................... 42
4.5 Best Practice Examples: ITALY ...................................... 47
4.6 Best Practice Examples: PORTUGAL ............................... 53
4.7 Best Practice Examples: SPAIN ..................................... 57
5 Solar cooling: examples on advanced approaches........................ 62
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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
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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 con-
tribute 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 peak-
power 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 www.solair-project.eu.
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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 chil-
led water systems, whereas medium sized systems may be open cycle desiccant
evaporative (DEC) cooling systems as well. While in the first type of system tech-
nology 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 humi-
dity 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 chil-
led 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 Qheat supplied to the process at a
temperature level of TH , heat is removed from the cold side thereby producing
the useful ‘cold’ Qcold at temperature TC. Both amounts of heat are to be rejected
(Qreject) at a medium temperature level TM. The driving heat Qheat may be pro-
vided 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 usu-
ally is responsible for a considerable fraction of the remaining energy consump-
tion of solar cooling systems.
A basic number to quantify the thermal process quality is the coefficient of per-
formance COP, defined as COP = Qcold / Qheat , 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
TH, TC and TM. 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.
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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
16°C - 18°C
Thermally (< 12°C)
Fan coil
driven
Chiller Cooled /
6°C - 9°C
Chilled water Conditioned
temperature area
Heat
> 50°C
Return air
Supply air
Desiccant evaporative Conditioned
cooling (DEC) 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.
Qheat
TH
TM
Qreject
TC
Qcold
Figure 2.2 Basic scheme of a thermally driven cooling process.
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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 lithium-
bromide as sorbent. Typical chilling capacities are in the range of several hun-
dred kW. Mainly, they are supplied with waste heat, district heat or heat from co-
generation. 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 tempe-
ratures > 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.
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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 H2O/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, appli-
cable 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 ge-
neral, they are designed to be operated with low driving temperatures and thus
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applicable for stationary solar thermal collectors. The lowest chiller capacity avai-
lable is now 4.5 kW. Some examples of small and medium size absorption
chillers are given in figure 2.4. In addition to the traditional working fluids
H2O/LiBr, also H2O/LiCl and NH3/H2O 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 be-
low 0°C in large capacities. An advantage of this chiller type is especially given in
applications, where a high temperature lift (TM – TC) 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 ma-
terials 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)
chilled water
EVAPORATO R
Figure 2.5 Scheme of an adsorption chiller. They consist basically of two sorbent com-
partments 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 con-
denser and transferred into the evaporator, is vaporised under low pressure in the eva-
porator. 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
version to 7.5 kW (model of 2008). Typical COP values of adsorption chillers are
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0.5-0.6. An advantage of the chillers are the low driving temperatures, beginning
from 60°C, the absence of a solution pump and a comparatively noiseless ope-
ration. 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 adsorp-
tion 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 appli-
cation of this cycle is limited to temperate climates, since the possible dehumidi-
fication is not high enough to enable evaporative cooling of the supply air at con-
ditions 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
high energy storage by means of concentrated hygrocopic solutions are note yet
market available but they are close to market introduction; several demon-
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stration projects are carried out in order to test 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.
ba ckup
hea te r
return air
7
12 11 10 9 8 cooling
humidifie r
loa ds
1 2 3 4 5
6
supply a ir
de hum idifier hea t rec ove ry
whee l 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
saturation line
8 9 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 11the water bound in the pores of the desiccant material of the dehumidifer wheel is
desorbed by means of the hot air
11 12exhaust air is blown to the environment by means of the return air fan.
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Regenerator ⇐ QH driving heat
LiCl/water
regeneration air
concentrated
solution storage
solution
Absorber
⇒ QM rejected heat
supply air 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 increa-
sed 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 sup-
ply 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 cer-
tain 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 appropri-
ate 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 col-
lectors 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 ther-
mally driven chillers with solar heat, at least flat plate collectors of high quality
(selective coating, improved insulation, high stagnation safety) are to be applied.
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
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200°C in order to drive e.g. double-effect chillers or ammonia-water chillers for a
high temperature lift.
glas cover
solar air collector
insulation collector frame
absorber with
air channels
glass cover
flat plate collector
insulation collector frame
absorber with
fluid channels
glass cover
CPC collector
insulation
reflector collector frame
absorber with
fluid channel
evacuated tube collector
evacuated
evacuated tube
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.
3 SOLAIR database of solar cooling and air-
conditioning
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, 2008]. The Best Practice Examples, presented in the
following section, are extracted from this database.
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Type of application Counts Technology Chilling Country
in capacity
database range
[kW]
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 DECliq, DEC 11-30 DE, AT, PT
Other public 2 Ad, DEC 5.5-6 DE, GR
Commercial office 11 Ab 9-70 AT, FR, DE, GR, IT, PT, ES
Commercial seminar area 1 DEC 60 DE
Commercial wine storage 1 Ab 52 FR
Residential 3 Ab, Ad 4.5-10 AT, IT, ES
total: 24
Table 3.1 Type of application, technology, cooling capacity and distribution by coun-
try of the sytems in the SOLAIR data base.
Abbreviations: Ab = Absorption; Ad = Adsorption; DEC = Desiccant Evaporative Cooling;
DECliq = liquid desiccant cooling.
4 SOLAIR Best Practice Examples
Many of the Best Practice examples presented in the following went into ope-
ration 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 cata-
logue aims to present the applicability of solar cooling technologies within diffe-
rent 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.
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4.1 Best Practice Examples: AUSTRIA
Examples presented at the following pages:
1. Ökopark, Hartberg
2. Bachler, Gröbming
3. SOLution, Sattledt
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To be continued at the following page
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View at the Ökopark Hartberg, Austria
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Components of the Ammonia/Water chiller, installed at the Bachler system, Gröbming,
Austria. Source: PINK Energie- und Speichertechnik.
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Scheme of the solar cooling system at Sattledt, Austria
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4.2 Best Practice Examples: FRANCE
Examples presented at the following pages:
1. Résidence du Lac, Maclas
2. GICB building, Banyuls sur Mer
3. Kristal building, Saint Denis de la Réunion
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Scheme of the solar cooling system at Maclas, France
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Collector array and heat rejection unit of the Saint Denis de la Réunion solar cooling
system, France
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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
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Solar cooling system at Fraunhofer ISE in Freiburg, Germany. Top: cooling operation during
summer. Bottom: heat pump operation during winter.
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Vacuum tube
collectors
Local steam
81 m² network
90 m²
Cooling Closed wet
circuit cooling tower
Solar heat storage
Heating
flap bypass
Solar
circuit circuit 2
1 2 3
Water / air heat exchanger flap storage
Buffer storage
ventilation system
Heating
circuit 1
A/C- Winter
supply valve heating
circuit Cold storage Adsorption chiller
70 kW
Chilled water circuit Chilled water circuit
secondary primary
Scheme of the solar cooling system at the University hospital laboratory building,
Freiburg, Germany
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Scheme of the Desiccant Evaporativ Cooling (DEC) system at IHK-SO, Freiburg, Germany
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Heat production sub-system of the solar cooling system at Ott Ingenieure, Langenau,
Germany
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Cold production sub-system of the solar cooling system at Ott Ingenieure, Langenau,
Germany
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Solar Info Center SIC, Freiburg, Germany
To be continued at the following page
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Installed solar driven liquid desiccant evaporative cooling system and scheme of the
system at the Solar Infor Center (SIC), Freiburg, Germany
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Scheme of the solar cooling system at IBA AG, Fürth, Germany
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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
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Scheme of the solar driven desiccant evaporative cooling system at Lavrio/Koropi,
Greece
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Scheme of installations of the solar energy building in Palaio Faliro, Greece
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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
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Scheme of the solar cooling system in Bolzano, Italy. Top: cooling operation mode in
summer; bottom: heating mode in winter
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Scheme of the cold production and cold distribution system at Trento, Italy
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4.6 Best Practice Examples: PORTUGAL
Examples presented at the following pages:
1. INETI building, Lisbon
2. Office building Vajra, Loulé
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Scheme of the desiccant evaporative cooling system (top) and of the solar / auxiliary
heating sub-system (bottom) at the Ineti building, Lisbon, Portugal
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4.7 Best Practice Examples: SPAIN
Examples presented at the following pages:
1. Pompeu Fabra Library, Mataró
2. Headquarter building of CARTIF, Valladolid
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Scheme of the desiccant evaporative cooling system (DEC) in the public library at
Mataró, Spain
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5 Solar cooling: examples on advanced approaches
The majority of installed solar cooling systems use stationary solar thermal col-
lectors, 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 perfor-
mance of values > 1.0 allows to decrease the solar thermal collector capa-
city 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 tempe-
rature 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 NH3/H20
absorption chillers for process cooling of a winery in Tunesia and of a dairy in
Marocco. The first system went into operation in April 2008.
For the first reason mentioned above, a demonstration system was recently in-
stalled 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 statio-
nary 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-
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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 appli-
cation. 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)
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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, 27-30 June, 2006.
[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. 2nd revised edition 2008; ISBN 3211730958.
[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 11th,
2008.
[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 11th, 2008.
[SOLAIR: Review technical solutions, 2008].
Task 2.1: Review of available technical solutions and successful running systems. Cross
Country Analysis. Public accessible report in SOLAIR.
www.solair-project.eu
[MEDISCO, 2006]
Mediterranean food and agro industry applications of solar cooling technologies. Contract
032559 (EU-INCO). Co-ordination: Politcnico di Milano, Italy. Duration: 01.10.2006 –
30.09.2009. www.medisco.org
[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 11th, 2008.
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