Труды Всемирного конгресса Международного общества солнечной энергии

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

892

1-4 on Winter Solstice

Fig. 1: Instantaneous energy gain of SECT in three different

installation on (1-1) Spring Equinox (1-2) Summer

Solstice (1-3) Autumnal Equinox and (1-4) Winter

Solstice; 1. ns-tube tilted at 40e, 2. h-tube, 3. v-

tube.

TABLE 1: DAILY ABSORBED ENERGY & RATIOS AT

NORTHERN LATITUDE 40°

Daily

absorbed

energy gain

(10

J/m)

Spring

Equinox

Summer

Solstice

Autumnal

Equinox

Winter

Solstice

ns1

2.46 2.36 2.27 1.55

1.78 1.56 1.66 1.47

1.98 0.809 1.83 1.57

/ E

ns1

0.72 0.66 0.73 0.94

/ E

ns1

0.80 0.34 0.80 1.01

/ E

0.90 1.93 0.91 0.93

Where E

ns1

represents the Daily absorbed energy gain of

ns-tube tilted at 40°, E

represents the energy gain of

h-tube, E

represents the energy gain of v-tube.

From table 1 we can result that E

ns1

reaches the maximum

value on the spring equinox day. It falls to the minimum

value on the winter solstice day. The E

ns1

of spring equinox

day is about 1.58 times that of winter solstice day. E

reaches the maximum value on the spring equinox day. It

falls to the minimum value on the winter solstice day. The

of spring equinox day is about 1.21 times that of winter

solstice day. E

reaches the maximum value on the spring

equinox day. It falls to the minimum value on the summer

solstice day. The E

of spring equinox day is 2.44 times

that of summer solstice day.

The daily E

or E

on the equinoxes is 73% or 80% of E

ns1

respectively. But they are the most difference in summer

solstice, the E

is 66% of E

ns1

, the E

is only 34% of E

ns1

The E

on summer solstice is lower; the E

is 1.93 times

2-1 on Spring Equinox

2-2 on Summer Solstice

2-3 on Autumnal Equinox

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

893

2-4 on Winter Solstice

Fig. 2: Instantaneous absorber energy of the evacuated

collector tubes in three different installation on (2-1)

Spring Equinox (2-2) Summer Solstice (2-3)

Autumnal Equinox and (2-4) Winter Solstice;

1. ns-tube tilted at 50°, 2. h- tube, 3. v-tube.

TABLE 2: DAILY ABSORBED ENERGY & RATIOS AT

NORTHERN LATITUDE 50°

daily

absorbed

energy gain

(10

J/m)

spring

equinox

summer

solstice

autumnal

equinox

winter

solstice

ns2

2.30 2.35 2.10 1.03

1.68 1.68 1.56 1.02

2.01 1.20 1.84 1.07

/ E

ns2

0.73 0.71 0.74 0.99

/ E

ns2

0.87 0.51 0.87 1.04

/ E

0.83 1.40 0.84 0.95

Where E

ns2

represents the energy gain of ns-tube tilted at

50°, E

represents the energy gain of h-tube, E

represents

the energy gain of v-tube.

The instantaneously energy gains of evacuated collection

tubes in three different installation placed on building at

northern latitude of 50° was shown in figure 2 of

(2-1)spring equinox, (2-2)summer solstice, (2-3)autumnal

equinox and (2-4) winter solstice in a year. The Daily

absorbed energy gains and the ratios of three different

installations were shown in table 2 respectively. Compared

with the ns-tube at the tilted angle and latitude of 40°, the

energy gain increases. The main reason leads to the

increase is the decrease of the incidence angle of sunlight

on southern façade collector during summer days. On

summer solstice day, the energy gain increases greatly. The

energy gain of tubes installed horizontally southern facade

is 1.4 times the value of which installed vertically. For the

tubes on southern building facade with on lower latitude,

the energy gain decreases rapidly, so does the practical

value of the tubes.

Where E

nsa

represents the Annual absorbed energy gain of

ns-tube tilted at angles same as the local latitude, E

represents the Annual absorbed energy gain of h-tube, E

represents the Annual absorbed energy gain of v-tube.

3-1 Annual absorbed energy at latitude of 40e

3-2 Annual absorbed energy at latitude of 50e

Fig. 3: Annual change in daily-absorbed energy of ECT in

three different installations 1. ns-tube tilted at local

latitude, 2.h- tube, 3.v-tube.

We calculate the energy gains of tubes installed in three

different directions at latitude of 40° and 50°. The results of

yearly energy gains are shown in Fig 3 and table 3. The

energy gains of tubes on southern façade are 75% that of

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

894

tubes installed in north-south direction, the solar resource

on the southern façade is relatively insufficient. The energy

gains of the h-tubes are relatively stable. The daily energy

gain of v-tubes varies with the season, it decrease a lot

during summer. To apply the solar energy on southern

façade, the tubes should be installed horizontally.

TABLE 3: ANNUAL ABSORBED ENERGY & RATIOS

daily absorbed

energy gain (10

J/m)

northern

latitude of

40°

northern

latitude of

50°

nsa

7.916 7.138

5.998 5.512

5.581 5.571

/ E

nsa

0.75 0.77

/ E

nsa

0.70 0.78

/ E

1.07 0.99

4. CONCLUSIONS

The concepts of solar irradiance ratio on heat absorber of

different shapes in ECT and absorbed energy factor

proposed in REF. {1} is the basis of establishing a model

for calculating the daily absorbed energy of ECT, and it

provides a new way available to analyze quantitatively the

thermal performance of ECT.

At latitude 40eand 50e, the energy gains of vertical and

horizontal tubes on southern façade are only 75% of the

ns-tube tilted at local latitude.

The annual energy gain of h-tube is 7% more than v-tube.

During summer, on simmer solstice day, the energy gain of

h-tube is about 2 times that of v-tube. The vertical tubes

on southern façade are not recommended, the energy gains

of sun energy plane collector on southern façade is less

then the vertical tubes, so the horizontal installed tubes are

the best for applying.

At high latitude, the ratio of the annual gains of v-tube and

h-tube is more than ns-tube; more solar energy could be

used. But at low latitude, it is less obviously.

The results in our paper can be used for design the vacuum

cylindric tube collector installed southern façade to meet

various needs of applying solar energy by the device in

various regions.

5. REFERENCES

(1) He Zinian, Ge Hongchuan, Jiang Fulin, Li Wei. (1997)

A comparison of optical performance between

evacuated collector tubes with flat end semicylindric

absorbers [J]. Solar Energy 60 (2) 109-117.

(2) Duffue J A and Beckman W A (1980) Solar engineering

of thermal processes. Wiley. New York.

(3) Li Shensheng(1996), Solar Energy of Physics. Capital

Normal University Publisher, Beijing.

A SOLAR-POWERED COMPOUND SYSTEM FOR HEATING AND COOLING

Wen-Shih Chang, Chih-Cheng Wang, Cheng-Chou Shieh, Biing-Yow Shen, Chao-Yang Huang,

Energy & Environment Research Laboratories, Industrial Technology Research Institute

Bldg. 64, 195, Sec. 4, Chung Hsing Rd., Chutung, Hsinchu, Taiwan 310, China

WS.Chang@itri.org.tw

ABSTRACT

In this paper, a solar-powered compound system for heating

and cooling was designed and constructed in a golf course

located in Hsinchu, Taiwan. Taiwan cocates in subtropical

area and has abundant solar energy resource. In summer,

about one third of the electricity may be consumed for

air-conditioning in buildings. The need of air-conditioning

is consistent with the solar radiation of the day and the

season. Therefore, it would be very meaningful to use solar

energy to produce chilled water for air-conditioning with

the heat-driven chiller.

An integrated, two-bed, closed-type adsorption chiller was

developed in the Industrial Technology Research Institute

in Taiwan. Plate fin and tube heat exchangers were adopted

as an adsorber and evaporator/condenser. Some test runs

have been conducted in the laboratory. Under the test

conditions of 80 hot water, 30ć cooling water, and 14ć

chilled water inlet temperatures, a cooling power ofć 9

kW and a COP (coefficient of performance for cooling) of

0.37 can be achieved. It has provided a SCP (specific

cooling power) of about 72 W/(kg adsorbent).

Some field tests have been performed from July to October

2006 for providing air conditioning and hot water. The

efficiency of the collector field lies in 18.5%~32.4%, with

an average value of 27.3%. The COP of the adsorption

chiller lies in 33.8ˁ~49.7ˁˈwith an average COP of

40.3% and an average cooling power of 7.79 kW. A typical

daily operation shows that the efficiency of the solar

heating system, the adsorption cooling and the entirely

solar cooling system is 28.4%, 45.2%, and 12.8%

respectively.

1. INTRODUCTION

Adsorption refrigeration technology is attracting more and

more attention in recent years because it can save energy

and is environmentally friendly. Adsorption cycles can be

driven by low-grade waste heat or solar energy under 80 . ć

They do not have to use ozone-depleting

chlorofluorocarbons (CFCs) and do not need electricity or

fossil fuels as driving sources.

Silica gel-water adsorption chiller can be used in

combination with solar energy because of the possibility

using the low-grade solar energy under 80 , which can be ć

easily obtained with flat-type collectors or vacuum tube

collectors. Although the adsorption chillers are thought to

be very promising in the future for the application of solar

cooling and waste heat recovery, the wide spread of this

technology is not yet possible. The reason is mostly

attributed to the poor COP value and higher product cost of

adsorption chillers.

In an authors’ previous study (Chang et al., 2007) an

integrated, one-bed, closed-type silica gel-water adsorption

chiller was developed and experimentally studied. Flat-tube

heat exchangers with corrugated fins were adopted as an

adsorber and evaporator/condenser. To further realize

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

896

commercialization of this kind of adsorption chiller, a

two-bed silica gel-water adsorption chiller that can provide

chilled water continuously was also developed and studied

(Chang et al., 2006).

In this paper, a two-bed silica gel-water adsorption chiller

with plate fin and tube heat exchangers is newly developed.

In order to conduct a field test, a solar-powered compound

system for heating and cooling was designed and

constructed in a golf course located in Hsinchu, Taiwan.

2. SYSTEM DESCRIPTION

Fig. 1 shows a schematic diagram of the entire system. The

system described in this paper is composed of 3 subsystems,

i.e. the solar heating circuit, the hot water supply circuit

and the adsorption cooling circuit.

The solar heating circuit possesses 108.5 m

flat-plate solar

collectors, whose efficiency is η

=0.76-4.7(T

-T

amb

)/G,

mounted on the roof ground surface of the building. The

collectors are installed at an azimuth of 30˚ south by east

and tilled at the angle of 20˚ to the ground. A solar hot

water storage tank of 1300 L in volume is used to store

solar heat with the design temperature of 80 . On the test ć

run a Temperature of 90 could be reached. This storage ć

tank would not only provide hot water higher than 65 ć as

heat source to drive the adsorption chiller but also provide

50 hot water to the dormitory.ć

Fig. 1: Schematic diagram of the system for heating and

cooling.

The hot water supply circuit is connected to the solar

heating circuit via a plate heat exchanger. The cold makeup

water will be heated to 50 by the solar hot water and ć

stored in 2 buffer tanks (each 1000 L). The hot water will

be supplied to the dormitory for bathing use of 50 persons

for a day. Eventually, the backup gas-fired boiler will be

automatically turned on to heat the water to the required

temperature.

The core component of the cooling circuit is an adsorption

chiller with about 10 kW cooling power, which was newly

developed in this study. This adsorption chiller is driven by

the solar hot water with the temperature of 65~95 and ć

will produce about 10 chilled water. The chilled water ć

will then be circulated to the employee restaurant for 3

hours around noon (from 10:40 to 13:40) in the summer

time (from May to September).

The installation location Shinchu is located in the north of

Taiwan. The geographical position of Shinchu is at a

latitude of 24.8° north and a longitude of 121° east. It

belongs to the subtropical climate zone. Fig. 2 shows the

monthly-average daily irradiation on a horizontal surface

and the ambient air temperature. The irradiation in summer

can be almost 3 times higher than in winter. Because the

solar hot water is usually consumed for the purpose of

bathing in Taiwan, the solar heat gain will not be consistent

with the heat demand by season. If the collector area is

determined by the winter demand, it will lead to excessive

solar heat gain in summer.

123456789101112

Month of the year

Irradiation [MJ/(m .day)]

Temperature [

]

Horizontal irradiance in

Shinchu

Average temperature

Fig. 2: Monthly average of horizontal irradiation and

ambient air temperature in Shinchu.

Fig. 3 shows the predicted daily solar heat gain of the

collectors. The hot water demand is indicated as a solid

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

897

curve. It is assumed that 50 L water of 60 is needed for ć

each person. 50 persons are considered. The daily hot water

demand varies from 464 MJ/day in January to 324 MJ/day

in July because of different makeup water temperature. We

can see that the solar heat is insufficient from December to

February. The backup gas-fired boiler would be necessarily

brought into operation. The white bars from May to

September indicate the solar heat used as driving heat

source of the adsorption chiller. Even though part of the

solar energy is used for air-conditioning, the rest heat is still

enough for the dormitory heat demand.

100

200

300

400

500

600

700

800

900

123456789101112

Month of the year

Daily heat quantity [MJ/day]

Solar heat for air-conditioning

Solar heat for dormitory

Fig. 3: Predicted solar heat gain for dormitory and for

air-conditioning.

3. ADSORPTION CHILLER

Fig. 4 shows a schematic view and a photograph of the

adsorption chiller developed in this study. It consists of 2

same units, the so-called integrated, one-bed, closed-type

silica gel-water adsorption chiller. Each unit mainly

consists of 2 heat exchangers. The upper one, i.e., the

adsorber is composed of copper plate fin and tube heat

exchangers (920.8*550*60 mm, fin pitch 2.54 mm). Silica

gel with corn diameter of 0.5-1.5 mm is packed between

the fins together with the PVAc binder. There are 4

vertically arranged adsorption heat exchangers in one

adsorption bed and 62.64 kg silica gel is employed.

The under one, i.e., the evaporator/condenser is composed

of 5 fin-tube heat exchangers (serve as evaporator and

condenser), which are horizontally placed on the bottom of

the vacuum chamber. This evaporator/condenser heat

exchanger is used as an evaporator during adsorption cycles

and as a condenser during desorption cycles.

(900*190.5*60 mm, fin pitch 1.8 mm)

Fig. 4: Schematic and photograph of the adsorption chiller.

The 2 chiller units were connected with 6 4-way valves. By

appropriate switch of the valves, it is then possible to

produce chilled water continuously. Heat recovery

processes for desorber/adsorber and for condenser/

evaporator were conducted to improve the COP.

The adsorption chiller has been tested in the laboratory. Fig.

5 shows the result of the test runs. The cooling power and

the COP increase with decreasing cooling water

temperatures as expected, because lower adsorption

temperatures lead to higher adsorptive capacity and then

higher cooling power. Under the standard test conditions of

80 к hot water, 30 к cooling water, and 14 к chilled

water inlet temperatures, a cooling power of 9 kW and a

COP of 0.37 can be achieved. The corresponding SCP

(specific cooling power) is about 72 W/(kg adsorbent).

Fig. 6 and 7 shows the measured temperatures and heat

transfer rates under the test conditions of 80 hot water, ć

25 cooling water, and 14ć chilled water inlet ć

temperatures. After the heat recovery processes the rest

water temperature in the desorber fell to about 57 ć while

the water temperature in the adsorber raised to about 53 к.

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

898

24 25 26 27 28 29 30 31 32

Cooling water temperature[

]

Cooling power [kW]

0.30

0.32

0.34

0.36

0.38

0.40

0.42

0.44

˖ˢˣ

Cooling Power

COP

Fig. 5: Experimental results by variation of cooling water

inlet temperature.

759 1518 2277 3036 3795

Operating time [sec]

Temperature [

]

Fig. 6: Measured temperatures during the operation

(80/25/14ć).

-240

-210

-180

-150

-120

-90

-60

-30

120

150

180

759 1518 2277 3036 3795

Heat Transfer Rate [kW]

Desorber

Evaporator

Adesorber Condenser

Opering Time[sec]

Fig. 7: Measured heat transfer rates during the operation

(80/25/14ć).

In the beginning of a cycle, there is a peak of the chilled

water outlet temperature. This resulted from the fact that

the rest water with higher temperature during the

desorption/condensation mode flowed into the chilled water

outlet circuit. This is a negative characteristic of this kind

of integrated adsorption chiller and should be avoided as

far as possible. One can conduct heat recovery of the

evaporator and condenser with a few seconds time delay

(relative to heat recovery of desorber and adsorber) to

depress this temperature peak. Alternatively, one can add a

buffer tank to the chilled water outlet circuit downstream to

diminish the temperature fluctuation.

4. MONITORING RESULTS

Fig. 8 shows a typical system operation result in the

cooling period on a normal sunny day (Sep./2/2006). The

chiller was operated from 10:40 to 13:40 for 3 hours. In this

period for air-conditioning, the average solar radiation is

about 721.8 W/m

. The temperature of the hot water tank

ranges from 71 ć to 80 ć, with an average value of 75.2

ć. The average solar energy collecting efficiency is about

28.4%. The highest COP of the adsorption chiller achieved

0.6. The average cooling power and COP is 8.39 kW and

0.452 respectively. The corresponding efficiency of solar

cooling system is about 12.8% (product of the efficiency of

the solar heating.

100

Local time

100

200

300

400

500

600

700

800

900

1000

1100

1200

Solar radiation [W/m ]

Solar radiation Collector efficiency

COP_adsorption cooling Solar hot water tank

Fig. 8: A typical system operation result during the use of

air-conditioning in one day (2 September 2006).

Fig. 9 shows the monitoring results in the period from April

to December. The adsorption chiller is operated from July

to October. The efficiency of the collector field lies in

18.5%~32.4%, with an average value of 27.3%. The COP

of the adsorption chiller lies in 33.8%~49.7%ˈwith an

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

899

average COP of 40.3% and an average cooling power of

7.79 kW.

Cooling power[kW]; Solar radiation[W/m ]

100

COP [%]; Collector efficiency[%]

Solar radiation Collector efficiency

COPchiller Cooling power

Fig. 9: Daily monitoring data of collector and chiller

efficiency from April to December.

5. NOMENCLATURE

COP Coefficient of performance, ratio of the output

cooling power and input heating power

SCP Specific cooling power, produced cooling power

per kg adsorbent [W/kg]

Inlet temperature of collector [ ]ć

amb

Ambient air temperature [ ]ć

G Global irradiance [W/m

]

Collector efficiency [-]

6. ACKNOWLEDGMENTS

The authors wish to thank the Energy Bureau, “Ministry of

Economic Affairs”, Taiwan, China, for the financial support

on this study.

7. REFERENCES

(1) W.S. Chang, C.C. Wang, C.C. Shieh, “Design and

Experiment of a solar-powered compound system for

heating and cooling”, HPC’06, Heat Powered Cycles,

Newcastle, England, 11~14 Sep., 2006

(2) W.S. Chang, C.C. Wang, C.C. Shieh “Experimental

study of a solid adsorption cooling system using

flat-tube heat exchangers as adsorption bed”, Applied

Thermal Engineering, Volume 27, Issue 13, 2007, pp.

2195-2199, Heat Powered Cycles – 04

EXPERIMENTAL STUDY ON THE SOLAR-WALL-AIR-COLLECTOR

AND SOLAR HOUSE

Liping Zhang, Hongju Ma, Haibo Liu, Jianli Zu

Technical Department of Himin Solar Energy Group Co.,Ltd,

No.37, Hubinbei Road

DezhouCity, Shandong Province, 253092,China

zliping2004@163.com

ABSTRACT

A solar-wall-air-collector used for heating buildings is

introduced. In the paper, using natural flow and forced flow

transfer for collector are all investigated. In the experiments,

the collector’s heat efficiency is abort 30.4% when heated

air is natural convection, and is about 60% when the

collector is placed vertical with ventilating device. Using

two collectors with ventilating device to the solar house

which heat load is 82.6W/m

, the temperature of the

indoors is abort 15.7

C, in author’s opinion, it is feasible to

use in the schools or factories’ heating where have enough

sunlight.

1. INTRODUCTION

Solar house is one of the earliest forms which is used in

heating by human being. Also, it is an important application

way in using solar energy. In 1939, the first solar

architecture for heating was built by MIT (abbr.

Massachusetts Institute of Technology). After 1960s

world’s energy crisis, solar architecture’s progress was

increasing sharply. Solar house is the building which can

use solar energy to substitute some general energy, which

can make the room get a certainly air temperature or a

comfortable living atmosphere. The early solar house used

solar heat energy and ray energy natural transfer to make

living room bright, as we known, which is called” passive

solar house”. Among of them, “Trombe Wall” is the

representation of collector-store-wall passive solar house

[1-4]. After it, with technology progress and inhabitancy

condition’s requirement, negative solar house was

developed, which comprises solar collector, store vessel,

bump, heat exchange and controller etc. heating system or

absorbed type cooling solar air-condition solar system,

which structure should have good insulation performance

which be same as passive house.

In the world, there are still any questions in using solar

house with “Trombe Wall”. For example, to the chilliness

areas, to the house requires more heat load in a whole day,

“Trombe Wall” is disadvantage in satisfying to heat load to

buildings in the morning because of thick wall’s heat inertia

which made wall body temperature’s up slowly very much

and thermosiphon press is low. In my country, outside

insulation technology is carried out in many areas because

the former “Trombe Wall” heat performance analysis will

be not able to new wall structure. The heat loss to ambient

of traditional “Trombe Wall” is bigger than modern’s [5].

Based on the passive solar house, we devised a

solar-wall-air-collector which can be used in common

buildings, also which was developed heating investigation

with building.

2. EXPERIMENT EQUIPMENT

The structure of solar-wall-air-collector are showed in

figure 1, including cross section (a) and vertical section (b)

(length (X) is1200mm, width (Z) is 9mm, height (Y) is

1780mm, absorber area is about 2.85m

). The absorber plate

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

901

is used V type plate with solar selective coating. The

insulation material is used in collector’s bottom and sides.

Air flows from collector two sides’ inlet to outlet via V type

absorber plate’s up and down. All the experiments are

tested outside completely.

(a)

(b)

Fig. 1: Structure ofsolar-wall-air-collector.

3. A SOLAR-WALL-AIR-COLLECTOR EXPERIMENT

3.1 Natural Flow Test

The collector is placed in YZ position, and air flow uses

natural convection. The experimental result of variation of

air flowrate of the collector and collector efficiency as a

function of irradiance with time are shown in figure 2 and 3

under the natural flow condition. The test result as follows:

average ambient air temperature is 21ć, average outlet

temperature is 106ć, average outlet velocity is 1.05m/s,

average air flowrate is 32.1m

/h, mean solar irradiance is

786W/΃, mean output energy is 680.5W, mean collector’s

heat efficiency is 30.4%.

3.2 Force Flow Test

The collector is placed in YZ position also, air flow is used

a ventilating device which power is 28 W. Under force flow

condition, the experimental result of variation air flowrate

Fig. 2: Variation of air flowrate and solar irradiance with

time.

Fig. 3: Variation of efficiency and solar irradiance with

time.

of the collector and collectoU efficiency as a function of

irradiance with time are shown in Figure 4 and 5. The test

result as follows: average ambient air temperature is 4.8ć,

average outlet temperature is 41.3 ć , average outlet

velocity is 3.7m/s, average air flowrate is 104.2m

/h, mean

output energy is 1194.7W, mean solar irradiance is

691.5W/m

, mean collector’s heat efficiency is 60.6%.

Fig. 4: Variation of air flowrate and solar irradiance with

time.

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

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