Труды Всемирного конгресса Международного общества солнечной энергии

Подождите немного. Документ загружается.

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

772

exchanger have been developed and tested. Both prototypes

have been extensively tested using different operating

conditions. Test results for the first prototype are presented

in Krause et al. (2005). Fig. 1 shows a photograph of the

second regenerator prototype, which has an improved flow

distribution. Test results for this are presented in Fig. 3.

Fig. 1: Photograph of the second regenerator prototype

installed in the test rig. The schematic on the right

hand side demonstrates the path of air, water and

desiccant flows.

ABSORBER/REGENERATOR MODEL

A numerical multi-element model has been developed for

water cooled/heated absorber/regenerators. The models

calculate the enthalpy balances for the water flow, the

desiccant film and the air stream for each element along the

channels. Both, parallel flow and counter flow conditions

can be considered. For each element, heat and mass transfer

from the desiccant to the air stream as well as heat transfer

through the heat exchanger plates are determined

simultaneously. The single enthalpy equations follow

approaches from Khan and Sulsona (1998).

The heat transfer coefficients are determined using

Reynolds and Nusselt number relationships for laminar and

turbulent flow in channels. In order to model different flow

directions of water, air and solution, an iterative procedure

including all elements is used.

In order to validate the models, comparisons with measured

data are necessary. Since the numerical models are

designed as static models, only quasi steady state

conditions can be used for the comparison.

3.1 Absorber Model

For the validation of the absorber model, test data from

Kessling (1998) have been used. In the tests, which consist

of 14 test sequences with steady-state conditions, the

performance of a single plate absorber instead of a

multi-plate absorber was tested. Due to this, even

distribution of all three fluids could have been assumed.

Thus, a quite reliable validation of the theoretical model

regarding heat and mass transfer phenomena is possible.

The main results of this comparison are presented in Fig. 2.

Since the flow rate of the cooling water was chosen

comparably high, and all inlet temperatures are chosen to

similar values, outlet temperatures of all fluids are not

varying much and are neglected for the comparison. As

Fig. 2 demonstrates, modeled and experimental outlet mass

concentration of the solution show very good agreement.

Simulated and tested air humidity follow the same trend,

however, the slight difference is caused by uncertainties in

the humidity measurement during the tests.

-5

-3

-1

051015

Humidity in g/kg

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Concentration in kg/kg

-40

-20

100

Number of experiment

Effect. in %

100

150

200

Ratio flow rate

Fig. 2: Comparison of data from the absorber model and

14 sets of experiments gained from Kessling (1998).

The top diagram shows air humidity and solution

mass concentration (inlet, modeled outlet and

experimental outlet conditions), the bottom diagram

modeled effectiveness and flow rate ratio between

air and solution.

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

773

Additionally, the performance of the model has been

compared to the finite-difference model from Mesquita et

al. (2006). For the same conditions used in the experiments

1 to 7 in Fig. 2, the humidity of the outlet air stream for

both models and the experiments together with the inlet

humidity are listed in Table 1. It shows that the deviations

of the models related to the overall absorbed moisture are

in the range of 2-3 %.

TABLE 1: COMPARISON OF THE OUTLET AIR

HUMIDITY GAINED FROM THE PRESENTED

MODEL A ND A FINITE-DIFFERENCE MODEL, CF.

MESQUITA ET AL. (2006). THE LAST COLUMN

REPRESENTS THE FLOW RATE RATIO BETWEEN

AIR AND DESICCANT SOLUTION

Number

of test

in g/kg

out-exp

in g/kg

out-mod

in g/kg

out-Mesq

g/kg

Flow

rate ratio

1 14.4 5.3 6.3 6.1 10.2

2 14.5 5.7 6.6 6.4 19.4

3 14.5 6.4 7.0 6.8 33.8

4 14.5 7.2 7.7 7.4 55.2

5 14.5 7.8 8.2 7.8 74.8

6 14.5 8.0 8.5 8.1 89.0

7 14.4 8.5 8.9 8.4 108.9

3.2 Regenerator Model

In contrast to the quasi-isothermal absorber performance,

significant temperature changes occur within internally

heated parallel plate regenerators. Thus, all the temperature

curves, solution concentration and air humidity form the

basis for the comparison of model and experiments.

Fig. 3 compares the simulation results with test data of the

regenerator presented in chapter 2. At points with

steady-state conditions, the comparison shows a good

agreement between the outlet temperatures of heating water

and air for most of the operating points. Additionally, the

resulting air humidity shows good agreement with the

experimental data, too, only the desiccant mass

concentration shows some discrepancy. However, the latter

is caused by uncertainties of the non-continuous mass

concentration measurement.

In the experiments, even flow of all three fluids over the

plates could not be guaranteed. Especially the even

distribution of the solution over the plates is very difficult

to realize. Thus, since flow development on the plates is not

calculated in the model, effects of non-even distribution

could only be considered using additional parameters.

However, since the non-even distribution could not be

measured directly, the effective heat and mass transfer area

used for the simulations had been adjusted to the heat and

mass transfer in the experiments. Additionally, the heat

transfer value through the plastic plates was fitted to the

experimental results.

Fig. 3: Simulation and experimental results of the

regenerator. The top diagram shows water and air

temperatures and the three flow rates, the bottom

diagram air humidity and solution mass

concentration.

Considering these adjustments, experiments and model

show good agreement independent on the operating

conditions.

4. RESULTS AND OUTLOOK

Both, experimental and theoretical investigations on heat

and mass exchangers for a liquid desiccant air conditioner

have been carried out. Two prototypes for regenerators

have been build and tested regarding their operational

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

774

behavior. A dditionally, models for regenerators and

absorbers have been developed. The regenerator model has

been compared to measured data from the second

regenerator prototype. The absorber model has been

validated with test data from literature as well as a

finite-difference model.

The investigations showed that a validation is possible

within the limits of the uncertainties of the experimental

tests. Both, experiments and simulations demonstrated the

option of using the presented design for components of

liquid desiccant systems. However, additional construction

work is necessary. Additionally, in order to design solar air

conditioning plants, simulation studies of a whole system

including the building are required.

5. ACKNOWLEDGEMENTS

This research was supported by a Marie Curie International

Fellowship within the 6

European Community Framework

Program.

6. REFERENCES

(1) Afonso, C.F.A. (2006): Recent advances in building air

conditioning systems, Applied Thermal Engineering,

Vol 26.

(2) Alizadeh, S., Saman, W. (2003): An experimental study

of a forced-flow solar collector/regenerator using liquid

desiccants, Solar Energy, Vol. 73, No. 5.

(3) Biel, S., Röben, J. (2002): Entwicklung, Bau und

messtechnische Untersuchung eines sorptionsgestützten

Klimagerätes unter Einsatz wässriger Salzlösungen.

Final report 0329151N

(4) Chengqin, R.; Yi, J.; Guangfa, T., Yianpin, Z. (2005): A

characteristic study of liquid desiccant

dehumidification / regeneration processes, Solar Energy,

Vol 79.

(5) Gommed, K., Grossman, G. (2007): Experimental

investigation of a liquid desiccant system for solar

cooling and dehumidification, Solar Energy, Vol 81.

(6) Kessling, W., Laevemann, E., Kapfhammer, C. (1998):

Energy Storage for Desiccant Cooling Systems

Component Development, Solar Energy, Vol. 64, No.4.

(7) Khan, A., Sulsona, F. (1998): Modelling and parametric

analysis of heat and mass transfer performance of

refrigerant cooled liquid desiccant absorbers,

International Journal of Energy Research, Vol 22.

(8) Krause, M., Saman, W., Vajen, K. (2005): Open Cycle

Liquid Desiccant Air Conditioning Systems –

Theoretical and Experimental Investigations, ANZSES

Conference Solar 2005, Dunedin, New Zealand

(9) Krause, M., Saman, W., Vajen, K. (2006): Optimisation

of a Regenerator for Open Cycle Liquid Desiccant Air

Conditioning Systems, EuroSun 2006, Glasgow.

(10) Lävemann, E., Peltzer, M. (2005): Solar Air

Conditioning of an Office Building in Singapore using

Open Cycle Liquid Desiccant Technology, 1

Intern.

Conference on Solar Air Conditioning, Staffelstein.

(11) Liu, X.H. , Zhang, Y., Qu, K.Y., Jiang, Y. (2006):

Experimental study on mass transfer performances of

cross flow dehumidifier using liquid desiccant, Energy

Conversion and Management, Vol 47.

(12) Lowenstein, A., Slayzak, S., Kozubal, E. (2006): A

Zero Carryover Liquid Desiccant Air Conditioner for

Solar Applications, ASME/Solar06, Denver, USA

(13) Mesquita, L.C.S., Harrison, S.J., Thomey, D. (2006):

Modeling of heat and mass transfer in parallel plate

liquid-desiccant dehumidifiers, Solar Energy, Vol 80.

CONFIGURATIONS OF WORLDWIDE FIRST SOLAR COOLING SYSTEMS USING

PARABOLIC TROUGH COLLECTORS ON LOCATIONS IN TURKEY

Ahmet Lokurlu

SOLITEM GmbH, Süsterfeldstraße 83, 52072 Aachen, Germany

a.lokurlu@solitem.de

www.solitem.de

ABSTRACT

In the Mediterranean country Turkey, like in other sunny

countries, almost every hotel, hospital and other public

facilities need air-conditioning during the summer period.

Therefore a very high power requirement is necessary,

because most of the up to date air-conditionings with

coolant are provided by electric powered compression

chillers. Based on the fact that solar radiation appears at the

same time as the need of air conditioning, you can assume

that cooling systems with double effect absorption chillers

combined with parabolic trough collectors can be driven

more suitable and more intelligent than conventional

systems.

The air conditioning systems using solar energy of

SOLITEM systems can be operated in lots of different

areas of energy supply (energy maintenance up to 100%

can be covered by these collector units with additional

components, storage, etc.). The remaining energy will be

transmitted to a steam generator and cooling water systems

of objects like hotels, hospitals and industrial facilities. The

market potential for Mediterranean countries with a high

cooling demand up to 5 or 7 months a year is very

attractive.

The first SOLITEM systems with solar cooling were

installed in “Iberotel Sarigerme Park” (TUI Group) in

Dalaman (Turkey), Hotel Grand Kaptan in Alanya (Turkey)

and Gebze High Technology Institute in Gebze (Turkey)

and are very successfully operated. In the phase of

developing these projects the components had to be

optimised concerning its dimension to obtain the ideal

configuration with existing conventional system of the

hotel to achieve the energy conservation and expenses.

The paper gives a description of the installed systems with

double-effect absorption chillers with special parabolic

trough collectors which can be installed on the roof of

buildings. It will be shown how these systems can not only

reduce the high electricity requirement and the cost for the

provision of cooling in the summer time but also the

possibility of CO2 zero-emission building supply.

1. INTRODUCTION

The sun is the ultimate energy source. Its energy surpasses

the world’s primary energy demand a ten thousand fold.

SOLITEM’s high goal is to optimise the use of this

enormous energy potential, as it will take the largest share

in the future energy mix.

Solar energy is environmentally friendly. It is practically

unlimited and enables energy generation without CO2

emissions. Despite the rising prices for conventional energy

sources, solar energy will always be for free and is

decentralised available.

In the Sun Belt Countries, nearly all public buildings like

hotels and hospitals need air conditioning during the

summer time. For this purpose, there is a great demand for

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

776

electricity since most of today’s air conditioning systems

are based on electricity powered compression cooling

systems. Due to the fact that the solar radiation is

simultaneous with the cooling demand, it is expected that

absorption cooling systems can be operated more

economically compared to the existing conventional

cooling systems.

The SOLITEM Group as a young and innovative company

develops and installs absorption cooling systems operated

with its proprietary developed parabolic trough collectors

(SOLITEM PTC), which not only reduce the high

electricity demand and costs for cooling, but also show a

CO2 emission free supply of the buildings.

The Subject of SOLITEM’s development is an integrated

energy supply system based on parabolic trough collectors

which are combined with a double effect absorption chiller

connected with an existing cooling, steam and hot-water

system for summer application and a warm water system

for winter application e.g. swimming pool heating etc.

At the “Iberotel Sarigerme Park” of the TUI group in

Dalaman/Turkey, the first SOLITEM solar cooling system

was installed and has been operated successfully since

winter 2003/2004. In the project development phase, the

components had to be optimised in terms of size to get the

optimal design by means of energy saving and investment.

Since then, another solar cooling system has been installed

in Turkey, and at present we are installing some other

systems in different countries with the aim of supplying air

conditioning and steam for summer applications, as well as

warm water for winter applications in hotels, hospitals and

industrial facilities.

2. GENERAL EXPLANATIONS

Conventional Solar Systems

The biggest problem of flat plate and evacuated tube

collectors is their low outlet temperature and connected

with this their efficiency at high temperatures that prevents

them from being efficiently used for air conditioning due to

a COP (Coefficient of Performance) of approx. 0.4 to 0.6

small sized applications. In order to satisfy a certain

demand, a larger collector area is needed. But at many

locations, like hotels, especially on roofs of buildings,

space is limited. As a result, the application range of

conventional solar systems is also limited.

3. THE PARABOLIC TROUGH COLLECTORS OF

SOLITEM (PTC)

To overcome these problems and to widen the applications

range for solar energy, SOLITEM developed two different

sized Parabolic Trough Collectors (PTC): The SOLITEM

PTC 1800 for large applications as well as the small sized

PTC 1100 for residential buildings. Both collectors have a

supply temperature of 200 °C to 250 °C and are capable for

roof mounting. The following standardised curve shows the

efficiency versus DT/G of the SOLITEM PTC 1100 for

different solar radiation and temperature values.

4. SOLAR COOLING APPLICATIONS

A very promising application of the system is solar cooling.

The high temperature level of the parabolic trough

collectors allows the operation of a highly efficient two

stage absorption chiller. With a performance almost three

times higher than the one of a single stage absorption

chiller (COP up to 1.5), the technology of solar cooling

becomes much more attractive. For the first time, there is a

real alternative to conventional air conditioning systems.

5. FIELDS OF APPLICATION

In contrast to flat plate and vacuum tube collectors the solar

high temperature range is opened through the SOLITEM

PTC. The results of this are many additional application

fields for solar energy use. These application fields are

incorporate solar cooling and air conditioning, process heat

supply for hotels and hospitals (laundries, kitchens,

sterilisers) as well as solar energy supply of production and

storage facilities with process steam demand.

Solar process steam generation, cooling and heating are the

already mentioned basic applications of the system. But

this is only the beginning: process steam with a pressure of

4 to 8 bar is a highly valuable energy source and can be

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

777

used for numerous other applications:

 Electricity Generation

 Desalination

 Combined Heat, Cooling and Power (CHCP)

 Chemical Industry

 Food Industry

 Textile Industry

The system can provide cooling, heating and process steam

at the same time. To make it even more profitable, it is

operated bivalent and also tariff depending. The control

unit is adjusted to the customers’ individual needs and thus

helps saving as much energy costs as possible.

The solar combined heat, cooling and power is a crucial

economical and ecological, highly efficient application. In

the first step of the application, solar energy is used for

electricity generation and in the second step, the heat

supplied by the power process is used for generating chilled

water and for supplying heat consumers. This example

shows a clear advantage of parabolic trough systems in

comparison to solar electricity generation with photovoltaic

systems.

6. A MODEL APPLICATION FOR AN INTEGRATED

ENERGY SUPPLY SYSTEM

An example for an integrated supply system developed by

SOLITEM is the “Iberotel Sarigerme Park” in

Dalaman/Turkey, which is equipped with an air

conditioning system that is operated with a double effect

absorption chiller.

As one can see in the schematic diagram below, the main

principle of the SOLITEM system is that the collector field

delivers high temperature heat at the level of 200 °C to 250

°C in the first cycle. In a steam generator that is placed

between the first and the second cycle of the process,

saturated steam is produced at 4 bar, which can be used for

the air conditioning in the double effect absorption chiller

on the one hand and, on the other hand, for the steam

supply of the laundry of the hotel. For different seasons, e.g.

for summer and winter applications, an improved system

configuration has also been developed for this location to

maximize the economic use of solar energy. An important

aspect of the use of the SOLITEM system is that this

system is not limited to only supplying buildings with air

conditioning and/or laundries and kitchens with steam

during summer time: it can also be used for the heating of

buildings or swimming pools in transition periods so that

profitability increases significantly.

Fig. 1: Schematic diagram of the SOLITEM System at the

Iberotel Sarigerme Park, Turkey.

The absorption system installed at the “Iberotel Sarigerme

Park” is supplied by solar generated steam with parameters

of up to 4 bar saturated steam with approx. 144 °C.

Furthermore, a small storage tank is needed to fit the

energy demand over the day. In case the outlet temperature

of the collectors is not high enough to drive the steam

generator (and thus the absorption chiller), auxiliary

heating with the fossil fuel boiler is necessary. In the case

of “Iberotel Sarigerme Park” the system is connected to the

existing steam system of the hotel, so that the remaining

power can be used from the steam power supply of the

hotel.

The aim was the optimal design of the components of the

plant, which means the capacities of the storage tank, the

boiler and especially the collector area, to cover the cold

and heat demand of the building. The configuration of the

plant is economically optimal, if a high level of fuel costs

savings with a low capital investment can be attained. In

operation, the system is regulated in a way that the greatest

possible part of cold and heat load is covered by solar

energy supplied by the installed collector area.

In Turkey, electricity costs are different depending on the

time of day. Between 5 and 10 p.m., electricity costs are

higher than during the normal tariff zone. In this high tariff

zone, it is important to reduce the share of the cooling

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

778

supply of the conventional cooling system, increasing the

solar contribution of the SOLITEM System to achieve

greater efficiency.

7. ENERGY SYSTEM DESCRIPTION

The SOLITEM PTC’s new roof mountable Parabolic

Trough Collector Series for temperature levels of up to 250

°C has been developed. The collector system is tracked by

a one axis tracking system and consists of modules with an

aperture width of 1.8 m and a length of 5 m each. Solar

radiation is focussed on an absorber tube which has a

diameter of 38 mm. The focussing element is an aluminium

reflector with a concentration measure of up to 30.

Fig. 2: SOLITEM PTC 1800 collector field at Gebze High

Technology Institute, Gebze/Turkey.

The figure shows a parabolic trough collector row of the

PTC 1800 with reflector surfaces. The thermal losses at the

high operating temperature level are reduced by a glass

envelope tube. Out of the consideration of the higher costs,

the glass envelope tube is not evacuated. The torsional

stiffness is enhanced by an additional metal tube (torsion

tube) behind the collector modules. A major part of the

collector components are manufactured in Ankara, where a

subsidiary of SOLITEM has been established. The rest of

the components are produced in Germany, in Turkey and

Switzerland. The tracking system of the Dalaman plant

operates with wire ropes and allows the tracking of six

collector rows with a number of eight modules each. A

controller for two-axis tracked mirrors was modified for

control requirements for the tracking of the parabolic

trough collectors. A calculation of the position of the sun

gives the input for an approximate positioning of the

collectors while sun sensors installed in different places of

the collectors provide data for a precise positioning (fine

tuning) of the collectors.

The collector field of the pilot plant consists of five parallel

rows with four modules each and a total aperture area of

180 m². Pressurised water is used as the heat transfer

medium. The inlet temperature of the collector field is

about 155 °C. 180 °C is the measured outlet temperature of

the field. With a downstream steam generator, saturated

steam with 0.4 MPa and 144 °C is generated.

8. SYSTEM OPERATION MODES

The SOLITEM system has at least two operation modes.

These modes are helpful to replace high fuel and electricity

costs with the available solar power, which depends on

general boundary conditions like price level for electricity

and fuel etc. But the operation modes are also dependent on

the behaviour of energy consumers, time of day and energy

consumption.

Fig. 3: Diagram showing the heat and cold supply.

In principle, it is possible to supply the whole hotel with

solar cooling provided by the SOLITEM System, but based

on efficiency, the optimal solar supply is between 40 and 80

%. That is why – at least presently – the SOLITEM System

is combined with conventional systems (bivalent operation),

which considerably adds to profitability. Besides, it is

differentiated between high and low tariff zones depending

on the time of day. In low tariff zones, in which electricity

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

779

is cheaper, less cold is produced, which means that more

process steam is available. In high tariff zones, when

electricity is more expensive, cold is the main product of

the system in order to save electricity. This operation mode

is characteristic for the summer mode (cooling/process

steam).

Another huge advantage is the possibility to also operate

the system in winter mode (heating). In this mode, the main

purpose of the system is to heat the buildings and/or

swimming pools and generate hot water. The operating

temperature in the collector field is lower than in summer

mode with around 60 °C to 80 °C, which raises the overall

degree of efficiency of the system due to lower heat losses.

In winter mode, the heat of the collector field is transmitted

to the warm water cycle of the hotel through a separate heat

exchanger.

The absorption chiller can be operated exclusively by solar

generated steam during peak load of the collector field.

Because of the two-stage design, the chiller reaches 140

kW cooling capacity at the fully loaded level with a

guaranteed Coefficient of Performance (COP) of 1.3 and

with a cooling water inlet temperature of 29 °C. The

conversion process of solar heat in chilled water for air

conditioning by the absorption chiller can be fundamentally

improved if it is operated on part load. In the part load

operation area, the COP value can achieve up to 1.5.

uring the initial phase of operation, adaptation problems

occurred, which have been eliminated by the optimisation

of the installation under consideration of the existing

structure. Since the optimisation of the installation has been

finished, the next step is to follow this year: The dimension

of the system will be extended significantly by a doubling

of the collector field area. With the magnification of a solar

energy deposit, a thermal capacity of about 200 kW will be

made available. With this energy amount, cooling demands

of up to 140 kW and steam demands of up to 100 kW can

be covered at the same time.

PTC Collector Field:

Manufacturer SOLITEM

Model PTC 1800

Aperture Area 180 m²

Heating Power 100 kW (Peak)

(DNI 800 W/m²)

Collector Temp. 180/155 °C

9. CONCLUSION

The solar energy based SOLITEM High Temperature air

conditioning system can be operated on a large share in

energy supply (up to 100 % of the power demand can be

covered by the solar unit).

The remaining energy is connected to the existing steam

and chilled water system of the hotel. The market potential

seems to be very attractive for Mediterranean countries

with a large cooling demand of about 5-7 months per year.

Further details of the concept will be presented at the

meeting. For this example, the savings in energy and costs

will be shown compared to a state of the art system. As

fossil fuel is substituted by solar energy, the emissions will

be reduced significantly.

ENERGY SAVINGS FOR A SOLAR HEATING SYSTEM IN PRACTICE

Simon Furbo, Jørgen M. Schultz

Department of Civil Engineering

Technical University of Denmark

Brovej, Building 118

DK-2800 Kgs Lyngby, Denmark

sf@byg.dtu.dk & js@byg.dtu.dk

Alexander Thür

AEE INTEC

Feldgasse 19

A-8200 Gleisdorf, Austria

a.thuer@aee.at

ABSTRACT

In July 2006 a new developed high efficient solar

heating/natural gas heating system was installed in an old

one family house in Denmark. The new system was based on

6.75 m² solar collectors and a condensing natural gas boiler.

Before the installation of the solar heating system, the house

was heated by a non condensing natural gas boiler.

The heat demand, the electricity consumption for the

energy and heating system as well as the natural gas

consumption were measured before and after installation of

the solar heating system. Based on the measurements the

energy savings of the solar heating system were estimated

to 4200 kWh per year, corresponding to 620 kWh/m²

collector per year. The energy savings will vary from year

to year. In years with a high heat demand the energy

savings will be high. In years with a low heat demand the

energy savings will be low.

1. INTRODUCTION

Only few investigations on energy savings for solar heating

systems in practice have been carried out. This is really

remarkable since most solar heating systems are installed

with the aim to save energy. The reason for the few

investigations is that it is extremely difficult to

measure/document the energy savings for solar heating

systems in practice.

In order to determine the energy savings, seven energy

quantities/efficiencies must be considered.

Before installation of the solar heating system:

 Utilization of energy for the energy system.

 Electricity consumption for the energy system.

After installation of the solar heating system:

 Net utilized solar energy of the solar heating system.

 Saved energy by turning off the auxiliary energy supply

system during the summer.

 Utilization of energy for the auxiliary energy supply

system.

 Electricity consumption for the auxiliary energy supply

system.

 Electricity consumption for the solar heating system.

Further, to make the determination even more difficult, the

energy savings are influenced by the heat demand and hot

water consumption, which will vary from year to year due

to weather variations, variations of user habits and due to

changes of the hydraulics of the energy system.

A Swedish investigation of solar heating systems, based on

questionnaires filled in by home owners, showed

unexpectedly high energy savings for solar heating systems

in practice [1]. Also unexpectedly large variations of the

energy savings were reported. Solar heating systems with

collector areas between 4 m² and 25 m² were included

in the investigations. The reported energy savings ranged

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

781

from 0 kWh per m² to 2750 kWh per m². The average

collector area of the investigated systems was 11 m², and

typical energy savings ranged from 650 kWh per m²

collector to 900 kWh per m².

A theoretical investigation showed that the energy savings

of solar heating systems are strongly influenced by the

efficiency of the energy system prior to installation of the

solar heating systems [2]. Especially the efficiency during

the summer period is of great importance.

An investigation of new natural gas boilers and oil fired

burners installed in one family houses without solar heating

systems showed unexpectedly low utilizations of natural

gas and oil in the summer and in periods with low heat

demands [3]. This is of great interest in countries, such as

Denmark, where oil and natural gas are often used as

primary energy sources in houses, where solar heating

systems are installed. A condensing and a non condensing

natural gas boiler as well as a non condensing oil fired

burner were included in the investigations. In spite of high

yearly utilizations of natural gas and oil between 80% and

95%, the utilization of natural gas/oil decreased to values

between 50% and 80% for the boilers/burner in the summer

months. In the 5 summer months May-September the

energy loss defined as the oil/natural gas consumption

minus the space heating demand minus the hot water

consumption was about 1000 kWh for the oil fired burner

and the non condensing natural gas boiler and about 500

kWh for the condensing natural gas boiler. These energy

quantities can easily be saved by well performing solar

heating systems.

2. DEMONSTRATION SYSTEM IN A ONE FAMILY

HOUSE

A new developed solar heating/natural gas heating system

was installed in a one family house with three inhabitants in

Helsinge, Denmark, latitude 56°N, in July 2006. The house,

which is shown in figure 1 before the installation of the

solar heating system, has three floors: A basement

including a bedroom and bathroom, a first floor including a

kitchen and a second floor including two bedrooms and a

bathroom.

Fig. 1: Demonstration house from the south before

installation of the solar heating system.

Before the installation of the solar heating system the house

was supplied with heat from a Vaillant non condensing

natural gas boiler from 1990 with a nominal power of 22

kW. For domestic hot water preparation the natural gas

boiler heated a 50l hot water tank, see Figure 2.

The solar heating system installed in the house has 5 Velux

solar collectors, type S08 with a total collector area of 6.75

m². The collect orientation is 15° towards east from south

and the collector tilt is 45°. The collectors have a start

efficiency of 0.79, a first order heat loss coefficient of 3.76

W/m²K, a second order heat loss coefficient of 0.0073

W/m²K² and an incidence angle modifier of

)/(tan 21 θ− ,

where θ is the incidence angle.

The solar heating system is based on a technical unit and a

heat storage unit produced by METRO THERM A/S. The

technical unit includes a modulating condensing natural gas

boiler from Milton A/S, type Milton Smart Line HR24, with

a nominal power for space heating of 5.7-23 kW and a

nominal power for hot water preparation of 5.7-28.5 kW, a

heat exchanger producing domestic hot water, and all

equipment needed to operate the solar collectors, the natural

gas boiler and the heating system. The heat storage unit

includes a 360l solar tank which can be charged by means of

the solar collectors and the natural gas boiler (4). The tank

insulation is partly PUR foam, partly vacuum panels.

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

Подождите немного. Документ загружается.