Труды Всемирного конгресса Международного общества солнечной энергии

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Proceedings of ISES Solar World Congress 2007: Solar Energy and Human Settlement

812

part of energy is lost due to missing latent heat recovery

which can be realized by a LDS [Waldenmaier 1998]. The

typical indoor temperatures should be between 25 °C and

35 °C and a relative humidity below at least 60 %.

2.7 Heat Recovery in Low Energy Buildings

Latent heat recovery for low energy buildings can be real-

ized by dehumidifying the exhaust air stream from a buildi-

ng [Kerskes 2004]. The more moisture is absorbed from the

exhaust air the higher temperature shift can be realized up

to 10 K above the room temperature.

3. DERIVATION OF A DESIGN GRAPH

Figure 2 represents the summary of the collected informa-

tion: In the lower part of the figure the requested humidity

and temperature levels for the presented applications are

shown. Additionally, the absorption equilibrium curves of

three different aqueous salt solutions i.e. lithium chloride,

calcium chloride [Conde 2004] and Klimat3930 [Walden-

maier 1998] are showing the minimum achievable relative

air humidity. In the upper part of figure 2 recommendations

are given for the selection of the absorber component

design depending on the temperature range. Below that

the possibilities of coupling the absorber to different

cooling and heating technologies are shown. The heating

systems can be coupled with adiabatic absorbers as

auxiliary devices in cases of insufficient performance of the

absorber unit.

4. CONCLUSIONS

Seven application categories could be distinguished and de-

scribed concerning their temperature and humidity require-

ments for LDS. Two general absorber designs were investig

ated for the applications. As the main result a graph was de-

rived from the collected and calculated data which helps to

design an open absorption system and to choose the design

for the absorber component and the type of liquid desiccant

which matches the requirements of the application in ques-

tion.

5. REFERENCES

(1) Al-Jaafari A. M. (2003): Comparative Analysis of

vapor compression and hybrid liquid desiccant

dehumidification systems, Thesis, University of

Florida.

(2) ASHRAE 55 (2004): Thermal environmental condi-

tions for human occupancy. ASHRAE Inc., USA.

Fig. 2: Requested humidity and temperature levels for different applications.

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

813

(3) Bland J., et al. (2002): New Inhibitor System for

Lithium Chloride Dehumidification Systems, Master

Brewers Association of the Americas, Technical

Quarterly, Vol. 39, No. 2, pp. 106-109.

(4) Conde M. R. (2004): Properties of aqueous solutions of

lithium and calcium chlorides: formulations for use in air

conditioning equipment design, International Journal of

Thermal Sciences, Vol. 43, No. 4, pp. 367-382.

(5) Conrad T. (1996): Technische, oekonomische und

oekologische Optimierung eines solaren Gewäch-

shaustrockners, Forschungsbericht Agrartechnik 283,

VDI-MEG.

(6) Davies P. A. (2005): A solar cooling system for green-

house food production in hot climates, Solar Energy,

Vol. 79, pp. 661-668.

(7) DIN 1946 (1994): Raumlufttechnik (Teil 2:

Gesundheitstechnische Anforderungen). Beuth, 1994.

(8) DIN ISO 11799 (2004): Information und Dokumenta-

tion – Anforderungen an die Aufbewahrung von

Archiv- und Bibliotheksgut.

(9) Henning H.-M. (2003): Solar-Assisted Air-Condition-

ing in Buildings – A Handbook for Planners, Springer-

Verlag, Vienna.

(10) ISO 7730 (2003): Gemäßigtes Umgebungsklima – Er-

mittlung des PMV und des PPD und Beschreibung der

Bedingungen für thermische Behaglichkeit. Beuth.

(11) Kerskes H., et al. (2004): MonoSorp – Ein

weiterer Schritt auf dem Weg zur vollständig

solarthermischen Gebäudeheizung, 14. Symposium

Thermische Solarenergie OTTI Energie-Kolleg.

(12) Krause M., et al. (2005): Regenerator Design for open

Cycle Liquid Desiccant Systems - Theoretical and

Experimental Investigations, Proc. International

Conference Solar Air-Conditioning, Staffelstein, 6. -

7.10.2005.

(13) Lävemann E., et al. (2005): Solar Air Conditioning of

an Office Building in Singapore using Open Cycle

Liquid Desiccant Technology, Proceeding of the

International Conference on Solar Air Conditioning,

Staffelstein, 06.-07.10.2005.

(14) Lowenstein, A. (1992): The Effect of Regenerator

Performance on a Liquid-Desiccant Air Conditioner,

ASHRAE transactions, Vol. 98, pp. 704-711.

(15) Lowenstein A., et al. (1998): Advanced Commercial

Liquid-Desiccant Technology Development Study,

Report Proj.-No. NREL/TP-550-24688.

(16) Lowenstein A., et al. (2006): A Zero Carryover Liquid

Desiccant Air Conditioner for Solar Applications,

ASME/Solar06, Denver, USA.

(17) Oelsen T. v. (2001): Experimentelle Untersuchung an

einem offenen Absorptionssystem zur Entfeuchtung in

Kreuzstromfahrweise, Dissertation, Universität Essen.

(18) Saman W. Y., et al. (2002): An experimental study of a

cross-flow type plate heat exchanger for de-

humidification/cooling, Solar Energy, Vol. 73, No. 1,

pp. 59-71.

(19) Simader G. R., et al. (2005): Klimatisierung, Kühlung

und Klimaschutz: Technologien, Wirtschaftlichkeit

und CO

-Reduktionspotenziale. Austrian Energy

Agency, Wien.

(20) Socher H-J. (1993): Warum Luftentfeuchtung? Ver-

fahren und Anwendung der Luftentfeuchtung, Kälte-

und Klimatechnik, September 1993.

(21) Steimle F., et al. (1998): Sorptive Entfeuchtung und

Temperaturabsenk ung bei der Klimatisierung,

BMBF-Abschlußbericht Band A bis F.

(22) Waldenmaier M. (1998): A Sorption Heat Storage Sys-

tem for Dehumidification of Indoor Swimming Pools,

IEA Annex 10, Phase Change Materials and Chemical

Reactions for Thermal Energy Storage, First

Workshop, 16 - 17 April 1998, Adana, Turkey, 1998.

TWENTY-EIGHT YEAR CONTINUED PERFORMANCE OF THERMAL

AIR COLLECTOR SYSTEM

Douglas A. Wilke

38 Roosevelt Avenue

Glen Head, New York 11545 USA

WilkeAE@Optonline.net

ABSTRACT

This report covers development, testing and continuous

successful 28 year operation of an air solar collector

heating system developed for the US Department of

Agriculture servicing rural housing 1975-1979. The 44.13

SQ Meter (475SF) surface area test collector has operated

continuously without physical deterioration at a New York

USA test facility since 1980.

The collector consists of a series of parallel horizontal thin,

steel ducts with thermal transfer mechanism forming the

absorber plate. The steel absorber has aluminum-zinc-

silicon coating overlayed with select black paint baked in

under a factory coil coating process. Glazing is of two

sheets of 0.03% iron oxide rolled tempered glass 3.2mm

(1/8") thick. Insulation is of polyisocyancurate. The

components are site assembled.

Three prototype collectors were developed and tested

beginning at the Brookhaven National Laboratory in New

York 1976. Primary testing for record was conducted by

D.S.E.T. Laboratory in Arizona during 1980 in accordance

with ASHRAE 93-77. Efficiencies recorded, double glazed

collectors 0.521; Single glazed 0.457.

In 1980 a five unit 44.13 SQ Meter (475SF) collector was

installed on a residence in New York State 40°N. Lat, Elev.

35 Meter constructed as a long term test facility. The units

were ducted to run in series or in parallel. All air ducts were

fitted with a series of five thermistars forming a

thermocluster for accurate temperature recording. Per

ASHRAE 93-77; temperatures, solar insolation, air flow

and pressure drop were data logged. Variable speeds of air

flow were tested with collector units operated in both series

and parallel.

Following twenty-eight years of monitored operation the

thermal yield remains approximately consistent with the

D.S.E.T. test results. Day long efficiency is .43 and above.

1. INTRODUCTION

In 1974 the United States Department of Agriculture

required a solar thermal system to replace electric thermal

for rural home heating, domestic hot water and crop drying.

The solar collector specification required efficient solar

system operation in all agricultural regions of the United

States. Collectors were to provide approximately 66% of

thermal energy requirements for a 100 Square Meter house

and have an installed cost not to exceed $17,000 (2007) US

dollars. Collectors were to be of durable maintenance free

materials and have no deterioration under prolonged

periods of stagnation and abandonment. Low carpentry

technology was required for new and retrofit installation.

The thermal collector developed employs air as a transfer

medium, has a steel absorber plate and a tempered glass

cover. The collector system is site-built from factory

manufactured modular components. The installed collector

is designed to be a complete roof segment.

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

815

2. COLLECTOR DESIGN CONCEPTS

A flat plate collector configuration was selected. The design

concept was to employ a low mass air transfer medium to

respond to intermittent direct solar insolation throughout

the solar day plus optimum utilization of the diffuse

component. Heating season energy delivery was to be 40°C

or higher at -6°C and 60°C at 27°C during non heating

months. The thermal mass of the steel collector was to

provide thermal inertia for continued air heating during

short periods of cloud cover. The glazing was to be a sealed

cover to prevent exterior low temperature air infiltration.

The system was to operate under negative pressure drawing

air through the collectors. Any air leakage into the collector

chamber would be from the conditioned space of the

building served. The collector array framing components

would not be sealed from the building interior so as to

allow any negative system air leakage to purge the glazing

and absorber surfaces of condensation with interior air from

minor leakage. The steel duct collector configuration had to

provide for continued efficient heat transfer to the air

medium through turbulent flow at varying air flow

velocities regulated to address fluxuation in solar insolation

and ambient air temperatures. Airflow resistance had to be

designed to minimize pressure drop and required blower

power.

The absorber (Figure 1(a)) consists of parallel 24 gage

(0.6096mm) sheet steel ducts 19mm high h457mm wide

h 3.6 to 5.5Meters long. Intake and outlet manifolds

provide uniform air flow through parallel ducts forming an

absorber width of 1.83Meters. The absorber coating is of a

formulationed select paint; solar absorptance 0.95; thermal

emittance 0.78 factory coil coated on an aluminum-zinc-

silicone substrate. The absorber ducts are fitted with

internal projections to facilitate turbulence at low velocities

to optimize thermal transfer during periods of reduced solar

insolation. The absorber duct length and internal

projections are determined by the micro climate profile of

the immediate area of installation and the required

application thermal gradient. The glazing is 3.2mm 0.03%

iron oxide tempered rolled glass in 1.93Meterh0.863Meter

sheet modules. The total collector glazing cover (Figure

1(b)) of one or two layers of glass is framed with aluminum

extrusions and gasketed with preformed EPDM rubber

gaskets.

(a)

(b)

(1) Select Paint Absorber Surface

(2) Sheet Metal Absorber Duct

(3) Building Roof Structure

(4) Isocyanurate Insulation

(5) Intake Manifold

(6) Exit Manifold

(7) Site Built Collector Frame

(8) Low Iron Glass Cover

Fig. 1: Sketch map of the collecter.

2.1 1980 ARIZONA TESTING

Development tests to optimize collector array components

and collector configurations were conducted by DSET

Laboratories, Phoenix, Arizona, USA in 1980. Two duct

configurations were tested under ASHRAE 93-77. 12.7mm

h152.4mm h5.5Meter and 19mm h457mmh5.5Meter.

The ducts were manifolded and glazed to form a 10.76

Square Meter collector set in a simulated roof unit. The

total unit was set on a rotating tilt table to track the sun.

A 3-day preconditioning stagnation test was performed in

accordance with para. 5.1.1 of ASHRAE Standard 93-77.

The collector was mounted facing south at a tilt which is the

test angle of the angle required to meet the total insolation

minimums specified. Preconditioning consisted of stagnation

exposure without air flow for three days in which the

cumulative daily insolation measured in the plane of the

collector is at least 1.7h10

KJ/M

/day (1,500BTU/FT

/day).

No failure or degredation was observed.

Proceedings of ISES Solar World Congress 2007: Solar Energy and Human Settlement

816

Testing to optimize efficient operation determined that the

19mm x 457mm x 5.5Meter absorber duct created

minimum pressure drop while retaining turbulated air flow

and heat transfer efficiency. A single diffuser baffle at the

exit end of the collector created equal air flow in all

absorber ducts with a minimum pressure drop. Negative air

flow with leakage of 6%. Collector pressure drop of under

13.72mm± of water was recorded at an air flow of

0.071CuMeter/Min/Square Meter (2.5CFM/SF) of collector

in the air passage length of 5.5Meters. Instantaneous spot

operating efficiency of the collector with double glazing

was determined to be 53% at the slope intercept operating

under high temperature conditions as recorded by DSET in

Arizona during 1980 (Figure 2).

Fig. 2: Instantaneous efficiency graph.

2.2 1980 NEW YORK TESTING

During September 1980 a series of four 8.83 Square Meter

collectors each of 4-19mm h 457mm h 5.5 Meter

absorber ducts forming a 35.3 Square Meter area started

long term testing on a test bed constructed to meet

ASHRAE 93-77 standards. An additional 8.83 Square

Meter reference collector was installed for calibration and

test comparison. Radiation was recorded on a Fluke 2008

datalogger. Under colder climatic conditions -5°C, as

compared to 40°C+ Arizona temperatures instantaneous

spot operating efficiency temperatures increased up to 5%.

The difference is attributed to higher temperature radiation

loss.

The series of tests conducted to study 0°C day long

operation resulted in optimization for winter heating at 0°C

by allowing the temperature of the 646.37KG (1,425lbs)

thermal steel mass to rise 38°C - 40°C above ambient before

starting air flow. The thermal inertia of the collector thermal

mass provided energy past the end of the effective solar day

insolation. The resulting day long efficiency achieved

averaged 43% (Figure 3). 20°C intake air was raised to 59°C

with optimized air flow at 0.0637 CuMeter/Min/Square

Meter (2.25CFM/SF) of collector. The thermal energy was

used to heat a 100SQMeter residence and to maintain a

151.4L (40gallon) tank of domestic hot water with a air to

water thermal siphon system.

During 1981 following one year of operation the total array

had glazing removed to inspect the absorber plates

condition. The reference collector had been left in

stagnation for 90 days. There was no evidence of material

or coating failure. The total collector array was reglazed

and has been operated for twenty-eight years. Spot

monitoring has been made throughout that time period. The

temperature gradient achieved and operating efficiency has

been consistent with the results of the 1980 tests.

2.3 2007 MONITORING

During the 28 years of operation of the system the test

blower drive was changed to a maximum operation of

0.057 CuMeter/Min/Square Meter (2.0CFM/SF) of

collector. Winter operation under solar radiation of 7.351 to

8.277Watt/Square Meter/Hr (270 to 304BTU/SF/Hr) at

ambient temperatures of -6°C to 0C recorded collector

supplied air of 56°C from return air of 20°C when

employing variable velocity air flow. The air supplied from

the collector was recorded at 55°C to 66°C above ambient

temperatures.

Instantaneous efficiency dependant upon radiation and air

mass flow is calculated to be 48.5% at 0.04

CuMeter/Min/Square Meter (1.4CFM/SF) to 54% at 0.056

CuMeter/Min/Square Meter (1.96CFM/SF) of collector

absorber plate. The optimum air flow is determined to be

0.045 to 0.057 CuMeter/Min/Square Meter (1.6 to

2.0CFM/SF) (Figure 4).

The collector was physically inspected without disassembly.

The collector has been cleaned only by natural rains and

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

817

snow. No deterioration of materials and the absorber

coatings were observed.

3. CONCLUSIONS

The air medium collector of low iron glazing and steel

absorber plate can operate at moderate temperatures for

space heating, farm process drying and domestic hot water

without failure in excess of thirty years. The coil coated

formulated select black absorber paint substrate retains its’

original properties. Air flow should exceed 0.045

CuMeter/Min/Square Meter (1.6CFM/SF) of collector. The

allowance of 6% leakage air from the interior of the

building to circulate throughout the void with negative

pressure between the absorber and the glazing purges

condensation from the collector. No collector maintenance

is required. Further improvements in operational efficiency

can be gained by application of computer programmed

controls. The thermal gradient of air produced by the

collector is suitable to operate a ceramic desiccant wheel in

regions of high summer humidity.

Fig. 3

Fig. 4

4. REFERENCES

(1) “ASHRAE Standard 93-77,” The American Society

of Heating, Refrigeration, and Air-Conditioning

Engineers, Inc., ASHRAE Publications, New York, NY,

1973.

(2) ASHRAE GRP170 Application of Solar Energy for

Heating and Cooling of Buildings, ASHRAE

Publication NYC 1977.

(3) Simon, F.F., and Harlament, P., “Flat-Plate Collector

Performance Evaluation: The Case for a Solar

Simulator Approach,” NASA TM X-71427, October

1973.

(4) Gupta, C. L., and Garg, H.O., “Performance Studies on

Solar Air Heaters,” Solar Energy, Vol. 11, No. 1, 1967.

(5) Whillier, A., “Design Factors Influencing Solar

Collector Performance, in Low Temperature

Engineering Applications of Solar Energy”, R. C.

Jordon, ed., ASHRAE, NYC 1967.

THE POTENTIAL FOR SOLAR COOLING IN IRAN

Farzad Jafarkazemi

Islamic Azad University, South Tehran Branch

North Jamalzadeh Street, Tehran, Iran

Member ISES

fjkazemi@parsonline.net

ABSTRACT

It is the aim of this paper to investigate the potential of

applying solar air conditioning and solar refrigeration in

Iran. The motivation for this research is the growing energy

use in the country which put it on the rising energy

intensity curve in recent years.

First a review is made on climatic conditions of the country

and air conditioning systems in use. Then the whole solar

air conditioning system and its components are introduced.

A conclusion is made on potential and barriers of

employing solar air conditioning systems in Iran.

1. INTRODUCTION

Environmental pollution norms, mark et fuel prices and

depleting fossil fuel resources impose stringent rules on

rational use of high grade energy consumed for air

conditioning of buildings and refrigeration.

This brings new opportunities for using renewable energy

sources wherever applicable. Among many other energy

conservation opportunities in air conditioning and

refrigeration systems, solar cooling is a very efficient mean,

especially in the countries where the solar energy is

abundant.

Solar cooling started in the 19

century when Pifre in 1872

in Paris produced ice by using steam from a solar system to

regenerate an absorbing solution. Regeneration of

absorbing solutions using parabolic mirrors was in 1953.

Solar assisted absorption chillers operating on H

O-LiBr

were constructed in Brisbane in 1955 and in Queensland in

1966.

However, with this background, commercial availability of

these systems in the desired capacity ranges and with

acceptable cost economics still remains a challenge [1].

The average solar energy radiation in Iran is quite

acceptable with and average sunshine hours of about 2800

h/year.

What makes the selection somewhat complex is different

climatic condition of the country from hot arid to hot humid.

This brings some limitation on selecting appropriate system

for each region. Also there is a wide variation in summer

temperature of about fifty degrees Celsius between coldest

and hottest cities.

In this paper further to a review of Iran climatic condition,

an introduction is made on current statues on solar driven

cooling system components. Finally a conclusion is made

on future perspective.

2. IRAN CLIMATE

Iran lies in the western part of the Iranian plateau about

north of eastern hemisphere and the south-west of Asia, and

is located approximately between 44° 02′ E and 63° 20′ E

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

819

eastern longitude and 25°03′ N to 39°46′ N northern

latitude. The country covers an area of about 1.648 million

km2. Its neighbors consist of Azerbaijan, Turkmenistan and

Armenia in the north, which are around the Caspian Sea,

Afghanistan and Pakistan in the east and Turkey and Iraq in

the west. Since Iran is situated at a considerable height above

sea level, the humidity is generally low except for the coastal

regions in the north and south of the country. A simplified

climatic map of the country is shown in Figure 1.

Fig. 1: Climatic map of Iran[2].

In summer hot weather generally prevails, in particular, in

the low land area and enclosed valleys such as those of

Khuzestan and Lorestan where the daily maximum often

exceed 44°C. Summer temperatures of more than 55°C

have been recorded.

About 52% of precipitation occurs in 25% of the area of the

country; hence some parts of the country will suffer a lack

of water resources and water crises in the near future.

Summer cooling is needed in hot dry central area,

temperate humid northern coast and hot humid southern

coast. While evaporative cooling is common in hot arid

area, recent installation of room air conditioners and

compression and absorption central air conditioners is

increasing. The humidity in northern and southern coastal

area limits the use of water cooled absorption systems. The

logical result is an ever increasing use of room air

conditioners and vapor compression chillers in these areas.

Iran is potentially one of the best regions for solar energy

utilization. The average solar energy radiation in Iran is

about 4 KW h/m2 with and average sunshine hours of

about 2800 h/year. The maximum values are considerably

higher in some central parts of the country.

A distribution of annual mean daily global solar radiation

of the country is shown in Figure 2.

Fig. 2: Solar radiation in different regions of Iran [3].

It can be seen that central arid and south coastal areas have

the largest potential for solar system application. The

important point which makes the decision somewhat

complex is that the best locations for solar system

utilization have the most humid climate. This brings some

limitation on using systems with water cooled heat

rejection.

3. SOLAR AIR CONDITIONING SYSTEMS

A solar air conditioning system in its complete form

comprises subsystems as shown in Figure 3. There are

some technical options for each subsystem, some arbitrary

and independent of the other ones and some dependent. A

review is made in the following sections on each

subsystem.

3.1 Building Load

Building load plays an important role in solar air

conditioning system. A sample cooling load for the design

day of a shopping center in Tehran, Iran is shown in figure

4 as an example.

Proceedings of ISES Solar World Congress 2007: Solar Energy and Human Settlement

820

Fig. 3: A solar air conditioning system with its subsystems.

Fig. 4: A typical load profile of a shopping center.

The sunset time in the same city is shown in Figure 5, in red

as a function of day of the year. Other lines show the peak

electricity consumption limiting hours and the mean line.

The figure shows that the sunset in Tehran in summer days

is quite sooner than the peak electricity consumption time.

It is estimated by comparison with a sample load profile

like Figure 4 that most of this electricity usage peak is due

to the air conditioning devices.

Fig. 5: Peak electricity consumption period and sunset time.

3.2 Building Air Conditioning Systems

The type of air conditioning system has an important role

on the type of solar cooling machine selected. Generally

building air conditioning systems can be divided into all

air, water, air/water and refrigerant based systems.

Excluding the refrigerant based systems which is not the

case for consideration in this paper, a review of the

relevant systems and their application is given by

Henning[4]. As a general rule, open systems like desiccant

based air conditioning is used in all air systems while

closed systems like absorption, adsorption and ejector

cycles are used in water or air/water systems. A

combination of the systems is also possible based on

technical and economical feasibility studies.

3.3 Solar Cooling Device

There are many different ways of converting solar energy

into cooling. Two different views of the available options as

introduced by Henning[5] and Pridasawas[6] during

ISES2003 are shown in Figures 6,7, respectively. As shown

in the figures, solar energy can be transformed either to

electricity or to heat, enabling different refrigeration

technologies to be driven by it. Based on both

classifications, solar cooling systems can be divided into

electric and thermal processes. Further classifications in

Figures 6, 7 are based on system type and cooling service

temperature, respectively. In Figure 6, commercially

available techniques are marked in dark grey and those at

the pilot project stage are shown in light grey. As can be

seen, techniques available either commercially or in test

stage are all in the thermal process subgroup. A comparison

is made in Tables 1 and 2 among closed and open cycles,

Average peak hour

Sunset hour

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

821

respectively which are mostly used. The literature on

describing the operating principle of each method is quite

large and it is not repeated here due to brevity and space

limits. The reader may refer to interesting recent papers by

Henning and Pridasawas[4,5,6].

Fig. 6: Solar cooling path according to Henning[5].

Fig. 7: Solar cooling path according to Pridasawas[6].

A recent report by Henning [7], shows the distribution of

installed solar driven cooling systems in Europe, among a

total of 100-120 units installed are as follows:

- Absorption: 60%

- Adsorption: 12%

- Solid desiccant system: 25%

- Liquid desiccant system: 4%

TABLE 1: CLOSED CYCLE METHODS

METHOD Closed cycle

CHILLED

MEDIA

Water

PROCESS Absorption system Adsorption

system

TYPE Single

effect

Double

Effect

Single

effect

____

WORKING

FLUID

Water Water NH3 Water

CAPACITY

(KW)

Few<100

Many>100

>100 Small

Large(US)

50-500

DRIVING

TEMP.(

○

80-110 140-160 80-120 60-95

COP 0.6-0.8 1.1-1.3 0.3-0.7 0.4-0.7

TABLE 2: OPEN CYCLE METHODS

METHOD Open cycle

CHILLED MEDIA Air

PROCESS Solid sorbents Liquid sorbents

DRIVING

TEMP.(

○

>60 >60

COP 0.5-0.8 >1

These may change in the near future based on the results

obtained in demonstration units and new developments in

adsorption and liquid desiccant systems.

3.4 Solar Collectors

Collector types in aforementioned solar cooling systems are

generally selected based on required driving temperature as

follow:

-Desiccant systems: Solar air collectors, Flat plate

collectors

- Adsorption systems: Flat plate, evacuated tube collectors

- Absorbtion (Single Effect): Flat plate, evacuated tube,

optical concentration without tracking

- Absorption (Double Effect): High efficiency evacuated

tube collectors, Optical concentration with tracking

3.5 Heat and cold Storage

The discussion in section 3.1 shows that due to the partial

Труды Всемирного конгресса Международного общества солнечной энергии - 2007. Том 2

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