Труды Всемирного конгресса Международного общества солнечной энергии

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

822

mismatch between the load and available radiation intensity

there must be a place for storing energy. This may also be

needed during the cloudy hours. It is important to note that

cool storage is not readily possible in desiccant cooling

systems. Then the only possible storage is heat storage. An

exception is liquid desiccant system which allows storage

of regenerated liquid desiccant media and using it

whenever there is no solar radiation. For closed cooling

systems, both options are applicable. A comparison

between the two methods is presented by Henning [4].

3.6 Heating and Cooling Back-Up Systems

Similar to storage, back-up system can be used on either

the hot or cold side of the system. Back-up heating is used

either as an aid in cooling season or the source of heating in

the heating season. As shown in figure 3, piping connection

can be like the one shown in solid or dashed, based on

application. Chilled system back up may have the same role

as the previous one or used as an add-on system. An

example is the desiccant cooling in hot humid climate

where the air is sensibly cooled before entering the

desiccant wheel and in hybrid desiccant cooling where a

combination of desiccant and vapor compression cooling is

used.

4. CONCLUSIONS

An introduction is made on climate of Iran, in order to

investigate technically the potential of employing solar air

conditioning systems in the country. A review is also made

on solar air conditioning system and its subsystems. The

available solar intensity of the country shows a good

technical potential for solar air conditioning. Economic

feasibility of these systems needs a transfer of subsides

from fuel and electricity to renewable energies. For

comparison, the current average prices of electricity and

natural gas (as the main heating fuel source) are $0.163/kWh

and $0.015/m

, respectively. The other problem which must

be considered more in detail is that in southern coastal

areas where there are both a huge need for cooling and

great solar intensity, humidity levels are also high. Using

desiccant systems in these areas need some special

pre-cooling of the air and higher regenerating temperature.

For closed systems in these areas, using water cooling

towers must be also taken by care. Use of desiccant

systems in central arid areas of the country needs a more

detailed comparison of water consumption of these systems

with available evaporative cooling devices.

5. REFERENCES

(1) H. M. Henning, “Solar Air-Conditioning and

Refrigeration; Task 38 of the IEA Solar Heating and

Cooling Programme”, Sustainability Victoria, May 14,

2007, Melbourne, Austraulia

(2) M. K. Rad, et all, “Feasibility Study of the Application

of Solar Heating Systems in Iran”, Renewable Energy,

2000; 20:333-345

(3) E. Asl-Soleimani, et all, “The Effect of Tilt Angle, Air

Pollution on Performance of Photovoltaic Systems in

Tehran”, Renewable Energy, 2001; 24:459-468

(4) H. M. Henning, “Solar Assisted Air Conditioning in

Buildings – A Handbook for Planners”, Wien: Springer;

2004, ISBN 3-211-00647-8

(5) H. M. Henning, E. Wiekmen, “Solar Assisted Air-

Conditioning of Buildings-An Overview”, ISES Solar

World Congress, June 14-19, 2003, Göteborg, Sweden

(6) W. Pridasawas, P. Lundqvist, “Technical Options for a

Solar-Driven Cooling System”, ISES Solar World

Congress, June 14-19, 2003, Göteborg, Sweden

(7) H. M. Henning, “Concept of the New IEA SHC Task 38

Solar Air-Conditioning and Refrigeration”, Inter-

national Conference onSolar Air Conditioning and

Refrigeration, October18, 2006, Bolzano, Italy

TESTING OF CONTROL EQUIPMENT FOR THERMAL SOLAR

SYSTEMS ACCORDING PREN TS 12977-5

Markus Peter

- Energienutzung mit Verstand

Mengeweg 2, 59494 Soest, Germany

email: markus.peter@dp-quadrat.de

Harald Drück

Universität Stuttgart, Institut für Thermodynamik und

Wärmetechnik (ITW)

Pfaffenwaldring 6, 70550 Stuttgart, Germany

email: drueck@itw.uni-stuttgart.de

ABSTRACT

Since 2004 the three parts of the European Standard series

ENV 12977, Thermal solar systems and components –

Custom build systems are under revision and, among others,

an additional part, titled “Performance test methods for

control equipment” was added. The new part substitute and

complement the specifications concerning testing of solar

loop controllers and temperature sensors previously given

in ENV 12977-2:2001, Annex B. Due to an increasing

complexity of control equipment used for solar and the

remaining heating systems and in order to test controllers

as detailed as it is e.g. already common for solar collectors

and hot water stores, an appropriate part of the standard

series dedicated to controllers and control equipment was

required.[1]

Beside quality assurance and improvement of the reliability

of all control equipment, the parameters determined by the

test procedures defined in the new developed part of the

standard will enhance the possibilities to determine the

performance of thermal solar systems by means of

computer simulation.

1. INTRODUCTION

Beginning in 2004 the three parts of the European Standard

series EVN 12977, Thermal solar systems and components–

Component Testing – System Simulation

Custom build systems are under revision. In this

frame-work, among others, a new part with the title

“Performance test methods for control equipment” was

worked out and added as part 5 to the 12977 series. With

the exception of part 3, Performance test methods for solar

water heater stores, which will be published as EN

12977-3, the other parts will have the status of technical

specifications (TS). In the case of EN TS 12977-5, this

new part of the standard will substitute and complement

the specifications concerning testing of solar loop

controllers and temperature sensors previously given in

ENV 12977-2:2001, Annex B. Due to increasingly

complex control equipment used for solar and the

remaining heating systems and in order to test controllers

as detailed as is it already common for solar collectors and

hot water stores, it was decided to elaborate an

appropriate part of the standard series only dedicated to

controllers and control equipment.

Supplementary to quality assurance and improvement of

reliability of the control equipment, the parameters

determined by the test procedures specified in the new part

of the 12977 standard series will improve the possibilities

to predict the performance of thermal solar systems by

means of computer simulation. Together with the collector

and store parameters, that are determined according to EN

12975-2 and EN 12977-3 respectively, the system

description based on component parameters will be more

complete. The entire set of parameters forms an excellent

basis for performance prediction and evaluation of thermal

solar systems according to the CTSS

method, which is

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

824

standardized in EN TS 12977-2.

With the European standard prEN TS 12977-5 for the first

time a test and evaluation procedure for a comprehensive

examination of controllers and control equipment for

thermal solar systems is available. The consistent

application of the procedures will increase the quality and

reliability of the control equipment and thus of the total

solar heating system. The described procedures enable a

reliable determination of control parameters, needed for

system performance determination according to the CTSS

method and will help to ensure a high level of quality for

the components.

Testing the usability and the quality of sensors and other

electronic equipment as actuators e.g. like pumps and

valves are other items included in the standard.

This paper primary summarizes the application of the new

European standard prEN TS 12977-5 for testing so-called

multi-function controllers and some further control

equipment as well as control algorithms incorporated in the

controller(s).

Furthermore general experience gained by testing

multi-function controllers according to the procedures

specified in the new standard is reported.

During summer 2007 part 1,2,3 and 5 of the 12977 series

were submitted to CEN Technical Comity TC 312 for CEN

enquiry

. After the formal vote the complete standard will

presumably be officially established in 2008.

2. HISTORY AND CONTENT OF EN TS 12977-5

In the first version of the standard series ENV 12977,

issued in 2001, test methods for controllers and control

equipment were described in part 2, annex B. In principle

the described methods were limited to the testing of

temperature sensors and simple solar loop controllers,

mainly differential thermostats. While testing the capability

of temperature sensors to resist to high temperatures was

mandatory, function testing of solar loop controllers was

optional. Due to the described test procedures, in practice

the examination and evaluation of control algorithms and

the investigation of the behaviour of so-called

multi-function controllers was very time consuming and

limited, respectively not possible without restrictions.

Today simple types of controllers and differential

thermostats gradually disappear from the market or their

market share is reduced significantly. More and more

multi-function controllers are used. Multi-function

controllers feature more than one temperature differential

algorithm or use other control algorithms than simple

differential thermostats.

During the revision of ENV 12977-2:2001 the few test

procedures for temperature sensors and controllers given in

annex B were taken out of part 2 and, with changes and

extensive innovations, put into the new developed part 5. In

parallel the other parts were revised. Finally, in the revised

version of the European Standard series EN (TS) 12977,

“Thermal solar systems and components – Custom built

systems“ in addition to the general requirements for control

equipment stated in part 1, more specific qualifications,

further requirements and advanced test procedures for

control equipment are described in the new added part 5,

“Performance test methods for control equipment”.[2]

The test procedures specified in the present version of

prEN TS 12977-5 in general are applicable for testing and

evaluation of any kind of electronic controllers and control

equipment like sensors or electrical actuators, e.g. pumps

and valves.

Beside the advantages listed above, not at least the

advanced and detailed test procedures can be used for

development and optimization of controllers and control

algorithms as well as durability and reliability tests of

sensors.

For quality assurance and to improve the reliability of

thermal solar systems as well as for further development

and high quality of system simulations and performance

predictions, a separate standard dealing with test methods

for control equipment was necessary.

CEN, Comité Européen de Normalisation,

CEN Enquiry, Procedure within the European

standardization process, taking place before the formal

vote on the drafts of the standards.

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

825

3. MULTIPLE ADVANTAGES OF TESTING CONTROL

EQUIPMENT

Examination and certification supports the quality of all

kinds of system components as well as of the complete

system. Supplementary in most cases the performance and

the reliability increases. Already at the very beginning,

during planning of the system and mainly when designing

the hydraulics and control concept, particularly with respect

to large-scale thermal solar systems the presented test and

evaluation procedures will contribute to minimize planning

failures and to optimize the system operation and

performance. A scheme demonstrating the multiple

advantages of testing of control equipment is shown in

Figure 1.

prEN TS 12977-5

fortestmethods

control equipment

secured planning

and design

quality assurance

operational

safty

optimisation

of operation

complaint

management

Fig. 1: Multiple advantages of testing control equipment

according to prEN TS 12977-5.

In addition to the multiple advantages that are shown above,

the test procedures given in prEN TS 12977-5 for the first

time allow the determination of the control parameters and

the testing of control equipment on the same level of detail,

as it is already usually for the solar collectors and heat

stores.

Particularly for combisystems, plants for solar cooling and

air-conditioning as well as for large-scale thermal solar

systems with and without seasonal storage a deviation of

the control algorithms from the intended ones or an

unwanted behaviour of the control regime might result in a

considerable reduction of the solar energy gain, failures

within the system or even a total breakdown of the system.

For that reason especially the knowledge of the control

algorithms of complex multi-function controllers and the

real behaviour of those controllers in combination with all

connected sensors and actuators is of great importance.

With regard to acceptance and market penetration of

thermal solar systems, detailed system simulation with

reliable results concerning energy gains and reliable

operation are crucial items. Not at least for optimisation of

custom built or specific adapted systems and concepts the

verification and adjustment of the control equipment is

necessary. In general the test procedures described in

prENV TS 12977-5 enable a direct coupling between the

controller and a real time system simulation.

Hence the procedure might also be used for development

and optimisation of controllers and control algorithms.

With the introduction of prEN TS 12977-5 an important

step towards testing of multi-function controllers has been

made and a deficit concerning quality assurance and

reliability is eliminated.

4. TEST PROCEDURES FOR CONTROLLERS ACC-

ORDING TO PREN TS 12977-5

A detailed description of the test procedures is given in

prEN TS 12977-5 /1/. One possibility of a test facility for

controller testing is shown in Figure 2.

flowmeter

hydraulic circuit

multimeter

personal

computer

controller

input/output

emulator

optional resistors/

temperature baths

Fig. 2: Schematic of a controller test facility including an

input/output emulator.

The controller to be tested will be examined under

“real“ operation conditions. In order to do this, the

connection terminals for inputs to the controller, which are

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

826

normally occupied by temperature depending resistors, are

connected to an input/output emulator generating variable

resistors. The input/output emulator can be supplied with

programmable temperature profiles of any pattern from a

PC. In parallel the status of the relevant outputs of the

controller are monitored contemporaneous. The

temperature profiles and the response of the controller are

stored on the PC. For examination of controllers featuring

variable flow, a hydraulic circuit is available, see Figure 2.

For more detailed information it is referred to /1/, /2/ and

/3/ respectively.

The overall procedure to determine control parameters in

accordance to prEN TS 12977-5 is shown in Figure 3.

Beside the test procedures for controllers, prEN TS

12977-5 includes detailed descriptions for testing the

functionality and reliability of common sensors, actuators

like pumps and valves and other control equipment.

sensors

analog and digital controller inputs

external signals

controller and/or

control equipment

timers and clocks parameters

behaviour of

controller

parameters

Fig. 3: Overall procedure for determination of control

parameters according to prEN TS 12977-5.

5. EXPERIENCE FROM APPLYING PREN TS 12977-5

In the following some experience from controller testing

according to prEN 12977-5 is summarized. For more

detailed information it is referred to /2/ and /3/. During a

test sequence all important data like signals to the controller,

temperatures, the response of the controller under test and

optional a volume flow rate are stored in a data file using

ASCII format. In parallel all important information is

displayed on the PC screen.

After performing a test, the data can be evaluated using

spreadsheet programs like Microcal Origin

or Microsoft

Excel

. As described the data contain information about the

response of the controller and its behaviour caused by

supplying defined temperature profiles as input values. The

temperature profiles can be comparable to situations in real

systems or represent extraordinary temperature courses.

Virtually all kinds of controller functions can be inspected.

By calculating the temperature differences from appropriate

sensors out of the measured data and plotting the results

together with the corresponding response of the controller,

the real behaviour as well as extraordinary effects of the

control equipment becomes visible.

In the following, some findings gained from controller

testing are presented. In order to underline the necessity

and the relevance of the introduced controller test method,

objectionable behaviour of control equipment is shown.

It was observed that in some cases the stability of control

algorithms or settings was not sufficient. For some

differential thermostats it was noticed, that the desired

switch ON and OFF temperatures were not constant over

the entire temperature range. With regard to the operation

of the collector loop pump this can lead to the situation that

the pump is still active at negative temperature differences

and hence discharges the store – instead of charging it.

In some cases controller with a large number of features

and options show interactions between functions that are

not specified in the documentation and that are not

meaningful for the system.

Due to inaccuracy of measurements, e. g. caused by

temperature sensors and/or the transfer or conditioning of

signals to and within the controller, some response

observed during the tests was faulty.

It should be noted, that the function of numerous

controllers was already tested without any serious failure in

the behaviour or within the electronic parts of the control

equipment. Nevertheless at least for some systems the

control equipment seems to be a weak point.

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

827

In practice the proper mounting of sensors and all other

control equipment is an additional, very important item. All

control equipment, particularly when it is mounted outside

and/or exposed to extreme operation conditions, has to be

suitable for the actual purpose.

In order to minimize the risk of insufficient behaviour, it is

recommended that in general the control equipment as well

as the complete solar heating system should be as simple as

possible and not more complex as necessary.

6. CONCLUSIONS

With the European standard prEN TS 12977-5 for the first

time a test and evaluation procedure for a comprehensive

examination of controllers and control equipment for

thermal solar systems is available. The consistent

application of the procedures enable a significant

improvement of the quality and the reliability of the control

equipment and thus of the entire solar heating system.

On the other hand the test procedures enable a reliable

determination of control parameters, needed for system

performance testing and evaluation according to the CTSS

method. In the framework of a comparison test of 16 solar

domestic hot water systems and 11 combisystems, carried

out for the German consumer magazine ‘test’ in 2000 and

2001, the method was successfully applied to determine

controller parameters for system simulations and

performance predictions using TRNSYS /5/.

Last but not least the detailed test procedures can be used

for development of controllers and control algorithms as

well as durability and reliability tests of common sensors and

other control equipment. Testing of controllers and control

equipment improves the transparency of the products and the

knowledge particularly necessary for planning and designing

of complex systems. At least, failures resulting from

objectionable controller behaviour might be detected faster

and an optimization of a system is easier.

7. REFERENCES

(1) Draft European Standard prEN TS 12977-5 Thermal

solar systems and components - Custom built systems,

Part 5: Performance test methods for control equipment,

submitted to CEN Enquiry

(2) Peter, M., Drück, H., “Testing of controllers for thermal

solar systems”, Proceedings ISES Solar World

Congress, June 14th to June 19 2003, Gothenburg,

Sweden, ISBN 91-631-4740-8

(3) Bachmann, S., Peter, M., Drück, H., Heidemann, W.,

Müller-Steinhagen, H., “Prüfung von Reglern für ther-

mische Solaranlagen”, Proceedings of “vierzehntes

Symposium Thermische Solarenergie”, Otti- Technologie-

Kolleg, Pages 193 – 197, Regensburg, April 2004,

ISBN 3-934681-33-6

(4) European Pre-Standard ENV 12977-2:2001, Thermal

solar systems and components – Custom built systems -,

Part 2: Test methods. Annex B: Testing of solar loop

controllers with temperature sensors

(5) Klein S. A. et al. (07/1996), TRNSYS 14.2, User

Manual University of Wisconsin, Solar Energy

Laboratory

THERMAL MODERNISATION THROUGH UTILISATION OF SOLAR ENERGY

Dorota Chwieduk

Institute of Fundamental Technological Research, Polish Academy of Sciences

ul. Swietokrzyska 21, 00049 Warszawa, PL

dchwied@ippt.gov.pl

ABSTRACT

The paper presents idea of modernization of energy system

in buildings through implementation of traditional energy

efficiency measures and introduction of modern options of

utilization of solar energy systems and recuperation of

waste heat. Sanatorium buildings in Busko Zdroj have been

modernizing since beginning of 90-thies. Coherent

traditional and innovative modernization actions have

resulted significant fossil fuel reduction and CO

emission.

1. INTRODUCTION

“Wlokniarz” sanatorium in Busko-Zdroj in Central Poland

(latitude – 51°N, longitude – 21°E) has been selected for

consideration because thermal modernization of this

sanatorium represents joined measures of standard energy

efficiency improvement and introduction of innovative

energy-saving solutions based on application of solar

energy. Busko is a small town with one of the best

insolation conditions in the country. Distribution of

monthly total solar radiation sums for Busko region is

presented in Fig. 1[1]. The monthly irradiation from April

to July is relatively high (for Polish conditions) and nearly

at the same level for these 4 months (about 150 kWh/m

In Busko, as in other health resort places, it is important to

keep the air pollution at very low level. Thus the conditions

for rest and health recovery are improved by clean

environment. The introduction of solar energy systems and

100

120

140

160

I II II IV V VI VII VIII IX X XI XII

Ic Swiety Krzyz

Fig. 1: Distribution of monthly total solar radiation.

other innovative technical solutions has been done not only

to improve the image of the resort, but mainly in order to

enhance energy efficiency effect of energy production and

use, and in a result to achieve significant reduction of

pollution and fossil fuel use. The paper presents some

results of the conceptual study of modernization of energy

system in sanatorium [2] and elements of internal reports of

CAMELIA project [3].

2. ENERGY INTENSITY OF THE SANATORIUM

COMPLEX BEFORE MODERNISATION

A sanatorium building complex, erected in the 70-thies,

consists of hotel buildings, the Natural Medicine Ward

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

829

linked with a swimming pool and gym facilities with a

sub-pool and a heat exchanger room underneath. On the

sanatorium area there is also a boiler house. For many years

boilers with capacity of 6.9 MW were fired by coal. The

coal with the quantity of 6000 tons/year was used. Annual

space heating energy of all sanatorium complex buildings

was equal to 6638 MWh (temperature inlet/outlet

90/70°C). Annual technological water heating energy +

domestic hot water heating energy was about 3390 MWh.

Taking into account relevant efficiencies total primary

energy for heat production accounted for 37.31 GWh,

with 24.7 GWh for space heating and 12.61 GWh for

DHW and technological hot water heating. Total annual

emission of CO

was equal to 12312.3 tons, with 4161.3

tons, i.e. 1/3, responsible for DHW + technological

water heating.

3. TRADITIONAL THERMAL MODERNISATION

The first phase of modernization of the heating system

started in the beginning of 90-thies. The most important

measure was switching from coal to gas. However, also

other modernization works were developed. In the years

1993-2003, these works were as follows:

- Heat source modernization:

 Exchange from coal boilers of 6.9 MW (0.6

efficiency) to gas (oil) boilers of 3.45 MW (0.88

efficiency) – 50% reduction of installed capacity;

 Modernization of the heat exchanger room,

facilities, and automatic control system in the

boiling room.

- Modernization of heat distribution system:

 Exchange and insulation of district heating

network;

 Modernization of infrastructure devices and end

users units.

- Reduction of space heating demand through thermal

refurbishment of buildings, including:

 Exchange of windows;

 Partly exchange of external walls with aluminum

plates into concrete blocs (administration

building);

 Insulation of all buildings with styrophoam.

During first modernization phase the standard of living

conditions in some buildings was improved. That was

mainly done through meeting new energy needs. For

example the HVAC system with the heat recuperation for

dining room, kitchen and common living room in one hotel

building was constructed.

Due to the all described modernization works total final

annual heating energy was reduced by 6773 MWh. Annual

energy consumption for space heating, i.e. 3383 MWh, was

nearly at the same level as annual energy consumption for

hot water heating energy (DHW + hot technological water),

i.e. 3390 MWh. Total primary energy use was equal to

9.861 GWh, with: 4.926 GWh for space heating and 4.935

GWh for DHW and technological hot water heating. After

the 1

phase of modernization CO

emission accounted for

1972.2 tons/year with 987 tons for hot water heating and

985.2 tons for space heating. It is necessary to mention that

thanks to traditional standard measures, mostly because of

switching from gas to coal and partly thermal

refurbishment of buildings the total CO

emission was

reduced more than 8 times.

Thanks to the first phase of modernisation of energy system,

it was evident that the sanatorium facilities consume

significant amount of heat for heating domestic hot water,

therapeutic treatment water and technological water. The

hot water heating demand became slightly higher than

space heating for all buildings. It was obvious that further

thermal modernization of all the facilities should be

directed to reduction of energy consumption for water

heating. With ongoing improvement of the buildings

envelope, including additional insulation, exchange of

windows, introduction of automatic control system of space

heating inside buildings, the space heating demand of all

the buildings can be lower by 30 - 40% of total heating

demands which makes demand for domestic hot water

heating the dominating element, at least 60%, of the

sanatorium heat balance. Thus measures towards energy

savings during preparation of domestic hot and therapeutic

treatment water have became crucial.

4. MODERN THERMAL MODERNISATION

In the second phase of modernization the priority has been

given to reduction of energy used for water heating at low

and medium level. This modernization phase has been

based on using innovative solutions like application of solar

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

830

thermal energy systems and recuperation of waste heat

present in sulphur sewage. A heat pump using the sulphur

sewage as a heat source has been applied to heat the

domestic and therapeutic treatment water. These modern

options of energy conservation have been coupled with

more traditional energy efficiency measures. All

modernization works after the year 2003 were as follows:

- Heat source modernization: New energy sources for hot

water:

 Solar heating system, flat plate solar collectors of

515 m

and capacity of 250 kW;

 Heat recovery from the waste sulphur water baths

by heat pumps that heats the treatment water in

the Natural Medicine Ward, 6 heat pumps each 50

- Modernization of heat distribution system:

 Cleaning the heaters of space heating system.

Installment of thermostatic valves at one hotel

building.

- Space heating reduction: Thermal refurbishment of

buildings:

 Insulation of the roof of the Natural Medicine

Ward;

 Exchange of windows (continuation).

During second modernization phase, similarly to the first

one, some actions were undertaken to improve indoor

comfort in some spaces. The new HVAC system with the

heat recuperation was installed in the second hotel building.

The completely new investment was the construction of

HVAC system with heat recuperation of the swimming pool

and gym of the Natural Medicine Ward, (only space heating

for gym was provided before modernization). This system

ensures appropriate air quality, maintains the constant

temperature and air humidity (dehumidification of pool air).

Heat is recovered from exhausted air of the swimming pool

and gym of the Natural Medicine Ward by the heat

exchangers at 78% of total efficiency. Recovered heat is

supplied to the air-water heat pump that heats water in the

pool. An alternative mode of operation is possible when the

air–water heat pump uses waste heat produced by the ice

water aggregator to heat the pool water.

4.1 Solar Heating System

The most important pro-ecological energy saving action

realized in the second phase of the modernization of the

energy system was the introduction of renewable energy in

a form of solar energy used by an active solar system with

flat plate solar collectors with total area of 515 m

to heat

domestic hot water at temperature 55°C (consumption 7300

/a by hotels, 7100 m

/a by the Natural Medicine Ward,

12000 m

/a by the hotel kitchen and laundry), for

therapeutic treatment (4000 m

/a), and for other heating

purposes 17570 m

/a). The solar system was designed to

supply 232 MWh/a of heat (834.0 GJ). In the solar heating

system antifreezing mixture circulates between solar

collectors and heat exchanger in a boiler house. The figure

presented below shows the general idea of one solar

collector loop and its integration into hot water system in

the boiler room.

Solar heating constitutes the preheating of DHW system.

There is a storage – buffer tank with a volume of 10 m

(number 3 in Fig. 2). This capacity is nearly two times

smaller than it was proposed in conceptual stage (2) (it was

17 m

). In summer there is overproduction of heat and the

extra mixture valve (number 2 in Fig. 2) had to be installed

to assure that temperature in the solar loop is not increasing

above safety limit. When necessary, especially in winter the

auxiliary heat in the second heat exchanger (number 4 in

Fig. 2) is provided by the gas-oil boilers.

–

mixture valve

4 - auxiliary heat from gas boiler –heat exchanger

1 - solar collectors

3 – storage - buffer tank and heat

Fig. 2: The general idea of solar hot water system in Busko.

The whole solar system constitutes 2 solar loops, each with

the same type of flat plate solar collectors and total area of

277.5 m

(150 panels of solar collectors in each loop). The

annual efficiency of the solar system is about 52%. Solar

collector thermal performance is approximated by the

parabolic efficiency curve with the following coefficients:

=0,794; c

=3,780 W/(m K); c

=0,017 W/(m K)

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

831

The azimuth angle of all collectors is equal to 0° and the

slope is equal to 40°. Collectors are located on different

buildings, what is shown in the Fig. 3, and therefore they have

different working conditions, because of shading and exposure

to wind. The high hotel building (at the right side of Fig. 3)

causes shading for solar collectors situated on the roof of the

Natural Medicine Ward (long building in the middle of Fig. 3),

at its east side in the morning hours. Also the length of piping

and pipework between solar collectors and the boiler house

depends on location of solar collectors. (In Fig. 3 the square

building is the gym with swimming pool and the building at

the down left side is the boiler house).

Fig. 3: The overall view of sanatorium complex in Busko.

The storage tank (in the boiler house) has the volume of

5000 liters for one loop of solar collectors, for two loops it

is 10 000 liters of storage capacity. The maximum storage

temperature is 75°, the minimum storage temperature is 42°C.

The solar loop is calculated for the daily heating DHW of

2035.25 kWh/day, i.e. for heating of 50 000 liters of water

per day from the temperature 10°C to 45°C. The second

loop is calculated in the same way, using the same

assumptions.

According to the calculation the average annual solar

energy gain is about 460 kWh/ m

of a solar collector. The

maximum daily heat production by solar collectors 5 GJ/

day, the average is about 2.9 – 3.5 GJ/d.

4.2 Heat Recovery Via A Heat Pump

Heat pumps use the waste heat recovered from the post-

sulphur bath sewage with flow of approximately 17 000 m

year at the temperature in average equals to 32

C. This

system constitutes four separate loops that are linked

together through heat exchangers. The simplified scheme of

the heat pump based on the waste heat recovered from the

post-sulphur bath sewage is shown in Fig. 4.

(1) Sewage storage tank

(2) Heat exchanger: sewage – heat sink liquid for the heat pump

evaporator

(3) Heat pump

(4) Heat exchanger: water heated by the heat pump condenser –

sulfur bath water

Fig. 4: The simplified scheme of a heat pump based on

waste heat recovered from the sulphur bath sewage.

Sewage water is directed to two tanks (number 1 in Fig. 4)

in alternating way. The tank, that is full of sewage at the

given moment of time, is the active source for the heat

recovery system. Sewage from the active tank is directed to

a heat exchanger. When heat is recovered the sewage

wastes are sent to the treatment sewage plant.

The next loop is between sewage heat exchanger (number 2

in Fig. 4) and the heat pump evaporator. The third loop

constitutes the heat pump (number 3 in Fig. 4) working

fluid that flows from evaporator to compressor, than to

condenser and to expansion valve, and next again to

evaporator. In the fourth loop water flows between the heat

pump condenser and the heat exchanger (number 4 in Fig. 4)

used to warm up sulphur bath water. The cooled water is

sent back to the heat pump condenser.

The most advantageous conditions for a heat pump

operation are when the operation is continuous with

possibly constant performance (both at lower and upper

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

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