Труды Всемирного конгресса Международного общества солнечной энергии

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PASSIVE SOLAR HEATING METHODS FOR ENERGY EFFICIENT ARCHITECTURE

Silke A. Krawietz

University of Catania

Faculty of Architecture

Via Luclio 11, 00136 Rome

seta@gmx.net

ABSTRACT

The likely increase in global warming over the coming

century means that designers will require greater creative

skills and better understanding of building performance in

order to ensure that low energy and passive buildings can

continue to meet end-user needs and expectations. The

priority is to find alternative, preferably ‘natural’ means of

achieving benign environmental conditions. Energy

efficiency in architecture, and as one important factor in

this area the natural ventilation, present important ways of

“Climate conscious” design and the reduction of energy

consumption in buildings. In this paper are presented the

main objectives and the view into past and present methods

and concepts of passive solar heating adapted in the

building sector, to assure comfort for the users together

with the most effective methods of energy efficiency in

buildings. Various concepts for passive solar heating are

discussed with specific architectural design possibilities,

including executed projects in the field.

1. INTRODUCTION

The steadily decreasing natural resources and the parallel

increasing world energy consumption are important factors

for the actual situation in the world and are indicators to

think about an enhanced use of renewable energy sources.

Global prognoses and the problem of climate change and

it’s consequences on life and the planet indicate, that a

change towards sustainable development is very important.

The energy situation in the world, in combination with the

rapidly rising global energy consumption and the increase

of the world population are reasons to act in various global

levels, to meet the challenges of the future. With 50% of

the World Energy consumption being used for houses, the

responsibility of architects and engineers for a sustainable

development presents an important factor in the world-wide

activities and projects. Energy efficiency is very important

and essential for the future ‘security’ of energy supply.

How can design mitigate this alarming statistic and address

the fact that climate change in general is threatening the

future existence of mankind? There will be increasing

challenges to design a sustainable built environment over

the next 100 years. Working with the climate, rather than

trying to defeat it, means accepting, for example, that

architecture should respond to its location, a building in

Morocco should not be a duplicate of one in Montreal.

Passive Solar Heating and Cooling Methods are important

factors for energy efficient architecture and bioclimatic

efficient design.

2. BASIC ELEMENTS

2.1 Thermal Comfort

The human body has its own mechanism for heat

production. The heat generated by metabolic activity

greatly exceeds that required to maintain deep body

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

863

temperature at its normal level. Strictly speaking, we have

no need for any external sources of heat; the principal

physiological requirement for thermal comfort is to

discharge the excess heat. In order to do this, however, we

require surroundings that will allow us to keep cooling

without stress: the body's cooling processes are suppressed

under very hot or humid conditions and exaggerated when

they are too cool, dry or draughty. Between such extremes

is a range of conditions perceived as comfortable or

unstressful. Creating such conditions in buildings is a

fundamental design objective. [1]

2.2 Heat Gain

At any given time Passive and internal heat gains may be

met by one or more of three main sources:

- solar radiation admitted indoors (through windows or

other glazed elements) and retained within the building

fabric in the form of heat, through processes commonly

known as passive solar heating.

- the heat generated by occupant activity and the operation

of household appliances, collectively known as internal,

casual or Incidental heat gains.

- the output from purpose-made heating appliances,

commonly referred to as auxiliary backup or conventional

heating.[1]

2.3 Processes of Passive Solar Heating

Solar radiation is transmitted indoors through windows or

other glazed elements and converted into heat by

absorption on opaque room surfaces. It is then stored,

released and distributed within a building through

processes generally known as passive solar heating. The

benefit to occupants can be assessed on two criteria: the

amount of conventional heating fuel that is displaced by

passive solar heating, and the effect this has on indoor

environmental conditions and amenity. Internal neat gains

from occupancy and household appliances can be assessed

in the same way.

In an ideally controlled space, amounts below the heat

demand would be instantly balanced by inputs from other

heat sources, while those above might be stored for later

use, transferred to any adjacent spaces requiring heat, or

rejected. Such controls would maximise the use of solar

gains by displacing (and thus saving) conventional heating

fuel, while preventing undesirably high temperatures. At

the other extreme, in a space with no temperature controls

the heating appliances would be unaffected by the presence

of any solar or internal heat gains and operate as if they

were not present. In such circumstances there would be no

energy savings. In addition, at times of high incidence of

solar or internal gains, the space temperature would rise

above that maintained by the heating appliances, possibly

to undesirable levels.

2.4 Designing with Climate

It is important as well to understand and evaluate the

architectural traditions in the various climatic regions,

which normally are influenced by culture, society needs

and habits. There are as well several ancient examples

which show the principles of passive solar design in their

architectural expression.

In the northern climatic regions the solar energy has been

used to heat buildings and to store it’s energy in the masses

of the building in order to release the heat in the night

times.

In southern climates instead, the protection and natural

ventilation has been one of the most important design

criteria. The linear building facing the sun can be found for

example in southern Italy and Scandinavian alike, in the

one place detailed to exclude summer sun, and in the other,

designed to admit the sun in winter.

“In each case, the complexity of approaches and means, the

manipulation of the site, the use of materials, the

interaction with cultural patterns of use and occupancy,

allows a similar form to operate in different climatic zones

and under dramatically different conditions.” [2]

The techniques required to heat and cool a building

passively have been used for thousands of years. Early

societies such as the Native American Anasazis and the

ancient Greeks perfected designs that effectively exploited

these natural processes. The Greeks considered anyone

who didn't use passive solar to heat a home to be a

barbarian! [3]

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

864

3. PASSIVE SOLAR DESIGN PRINCIPLES

3.1 Passive Solar Heating

General Principles:

Passive solar heating is the warming effect produced

naturally by the absorption of solar radiation on landscape

elements, building materials, room surfaces and furniture,

and/or on human clothing and skin. In the North Europe

climate, the solar radiation absorbed by outdoor surfaces

can help reduce thermal discomfort in open spaces, making

them feel more pleasant; it should therefore be an important

consideration in site planning and landscaping. Solar

radiation absorbed indoors can contribute to space heating

and thermal comfort.

Except where special measures have been taken to exclude

solar radiation, the physical phenomena of passive solar

heating occur spontaneously in all buildings. Without some

planning, however, solar heat gains may have little effect in

displacing conventional heating and can at times become a

nuisance. Planning for the admission of solar radiation

indoors, and for its exclusion at certain times, requires

consideration of a site's sunshine availability. The

orientation, size and specification of windows and other

glazed elements are the main building design measures for

exploiting solar gains.

The physical processes involved in solar gain and passive

solar heating can be considered under the following

headings:

 site parameters and availability of sunshine / Effect of

Latitude and orientation.

 solar radiation on external building surfaces.

 solar radiation indoors.

 interaction with occupants and other heat sources.

Any external building element may be combined with

glazing to create the conditions for passive solar heating.

Different combinations provide alternative ways in which

incoming solar radiation will interact with occupied spaces

like windows, conservatories and glazed atria and as well

as glazed walls.

3.3 Solar Gains and Heat Loss Through Windows

The potential for solar gain is diminished by un-favourable

orientation and external or internal obstructions.

Single glazing and poor detailing exacerbate heat loss.

3.4 Conservatories

Conservatories are an archetypal form of climate-

responsive structure. Like their Victorian antecedents,

contemporary applications for horticultural and agricultural

uses aim to create a milder climate than outdoors while

retaining the benefits of daylight and sunshine. In Britain,

conservatories have been used as home extensions for more

than a century, and they appear to be increasingly popular

for this purpose. The large area of glazing on their envelope

entails the collection of considerable amounts of solar

radiation. This can lead to high temperatures on sunny days,

while the relatively poor thermal properties of the glazing

tend to lead to low temperatures at night. (Heated conven-

tionally, conservatories consume large amounts of energy

and are therefore very expensive to run; left to the mercy of

summer sunshine they become uninhabitable.)

3.5 Glazed Walles

The addition of glazing on the outer side of an external wall

provides a means of trapping the solar radiation transmitted

through the glazing by suppressing part of the convective

and radiative heat losses from the face of the wall. Given a

suitably dark colour, the surface of the wall behind the

glazing will absorb the incoming radiation and release heat

to the cavity between the wall and the glazing. The wall

may also store heat in its mass. In consistently sunny

climates (such as those around the Mediterranean) the

magnitude of the radiation striking such a wall may be

sufficient to produce temperatures in the air cavity which

are high enough for the wall to operate as a natural heating

appliance. It might then supply adjacent rooms with warm

air by means of natural convection, as well as transfer

indoors the heat stored in its mass. In more cloudy climates,

however, temperatures in the cavity may not be high

enough for this process and there may be little solar gain to

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

865

store in the mass of the wall. In such circumstances

convection in the cavity and long-wave radiation from the

surface of the wall should be discouraged in order to reduce

heat loss (2.31). The key issue is whether the heat retained

by the wall can match a dwelling's heat demand pattern or

compensate for the wall's heat losses. [4]

There are variants of glazed Wall principles. The

differences are in the way the absorber and heat storage and

distribution functions are handled behind the glazing. There

are the types of Trombe Micheal Wall, Mass Wall,

Thermosiphon air panel (TAP) and Transparent insulation

material (TIM).

- A ‘Trombe-Michel Wall’ combines heat storage and

transfer through the mass of an un-insulated solid wall with

natural convection.

- mass wall excludes heat distribution by convection,

relying solely on heat transfer through the mass of the wall.

- A Thermosiphon Air Panel (TAP) includes a metallic

absorber (separate from the wall) and relies mainly on

natural convection, with heat distribution through channels

in the floor and ceiling.

- A ‘Transparent Insulation Material’ (TIM) can be fitted

behind glass on the external surface of a solid wall. TIM

allows incoming radiation to be transmitted through its

structure and absorbed by the surface of the wall while

restricting heat losses back to the outside.

The glazing on a wall has no other purpose than to provide

space heating and, unlike conservatories, glazed walls have little

amenity value. However, in contrast to windows, the mediation

of a wall prevents exposure of occupied spaces to the incoming

radiation, and this can be an advantage in some cases.

4. PAST PASSIVE SOLAR EXAMPLES

4.1 Past Experiences

Over the last thirty years a number of different approaches

to passive solar heating have been tried out. Few of these

applications were either entirely new in concept or very

different from conventional building practice. The history

of the exploitation of sunlight for daylight and passive solar

heating is as long as the history of building itself. The onus

on contemporary applications has been to meet the higher

comfort expectations of present-day living while at the

same time avoiding undesirable overheating or other side

effects.

5. CONTEMPORARY PASSIVE SOLAR EXAMPLES

5.1 Retscreen

The RetScreen software programme (www.restcreen.net/)

is a software tool which has been developed by the

Canadian Ministry in collaboration and support of NASA,

UNEP and GEF. One of the examined types of renewable

energy and energy efficiency in buildings is the passive

solar heating project model, which can be downloaded free

of charge like also all the other programmes, case studies

and e-manuals.

The Passive Solar Heating Project Model (Version 3) can

be used world-wide to easily evaluate the energy

production (or savings), life-cycle costs and greenhouse gas

emissions reduction for passive solar designs and/or energy

efficient window use in low-rise residential and small

commercial building applications. The model can be used

where there is a relatively significant heating load. The

model calculates, for both retrofit or new construction

projects, the difference in heating and cooling energy

consumption between a proposed passive solar building

design (or energy efficient window use) and an identical

building but without the passive solar (or energy efficient

window) features. The software also includes product and

weather database and an online manual. Version 3 upgrades

include a Sensitivity & Risk Analysis worksheet. [5]

The Example in Bozen, Italy shows that

- Passive solar heating (PSH) can significantly reduce

space-heating costs.

- High performance windows are a key component of PSH

and even very advanced window systems can be cost

effective in new construction when compared to windows

typically installed using conv. building practices

conservatory sunspace incorporated into the building

shortens the heating season.

5.2 BedZed Example in UK

BedZED (Beddington Zero Energy Development)

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

866

Helios Road, Wallington, Surrey, SM6 (London Borough of

Sutton)

Developer: Peabody Trust

Architect: Bill Dunster Architects

Environmental Consultant: BioRegional

Development Group, Completed: 2002

The BedZED design concept was driven by the desire to

create a net ‘zero fossil energy development’, one that will

produce at least as much energy from renewable sources as

it consumes. Only energy from renewable sources is used

to meet the energy needs of the development. BedZED is

therefore a carbon neutral development - resulting in no net

addition of carbon dioxide to the atmosphere. [6]

Space Heating

Through the innovative design and construction, heat from

the sun and heat generated by occupants and every day

activities such as cooking is sufficient to heat BedZED

homes to a comfortable temperature. The need for space

heating, which accounts for a significant part of the energy

demand in conventional buildings, is therefore reduced or

completely eliminated. BedZED homes and offices are

fitted with low energy lighting and energy efficient

appliances to reduce electricity requirements.

To enable residents and workers to keep track of their heat

and electricity use, meters are mounted in each home and

office kitchen. The buildings are constructed from

thermally massive materials that store heat during warm

conditions and release heat at cooler times. In addition, all

buildings are enclosed in a 300mm insulation jacket.

BedZED houses are arranged in south facing terraces to

maximise heat gain from the sun, known as passive solar

gain. Each terrace is backed by north facing offices, where

minimal solar gain reduces the tendency to overheat and

the need for energy hungry air conditioning.

Beyond BEDZed: In order to reverse the trend for

increasing carbon dioxide emissions from housing an

imaginative reappraisal is needed of the way homes are built.

BedZED demonstrates that comfortable, attractive,

affordable and energy efficient buildings are the homes and

workplaces of the future. [6]

6. CONLUSIONS

As to the passive design development, the question of how

far to take these objectives can be answered only in relation

to the site conditions and specific requirements of a design

brief. The related topics include

- Siting and site layout

- building form

- internal planning

- glazing and window design

- ventilation and air-tightness

- heating appliances and control

- conservatories

Passive Solar Heating is important for energy efficient

architectural design, most of all in cool and cold climatic

regions. Passive Solar Cooling instead is an essential factor

in hot climate regions.

7. REFERENCES

(1) S. Yannes, “Solar Energy and Housing Design”, Vo lum e

1, Architectural Association, Department for Enterprise,

Bond Ltd 1994, p. 10, p. 14

(2) O. Cofaigh, J. Olley, J. O. Lewis, “The Climatic

Dwelling”, James & James Publisher Ltd, London 1998,

p.8

(3) D.D. Chiras, “The Solar House – Passive Heating and

Cooling”, Chealsea Green Publishing, 2000

(4) S. Yannes, “Solar Energy and Housing Design”,

Vo lume 1, Architectural Association, Department for

Enterprise, Bond Ltd 1994, p. 40

(5) RetScreen.net, “www.retscreen.net”, Passive Solar

Sistems, Version 3, Natural Resources Canada, 2006

(6) C. Twinn, “BedZED”, The Arup Journal, ARUP Uk,

http://www.arup.com/_assets/_download/download68.

pdf

MONITORING RESULTS OF A COMBINED PELLET AND SOLAR HEATING SYSTEM

Frank Fiedler

Solar Energy Research Center SERC,

Högskolan Dalarna, S-78188 Borlänge, Sweden

ffi@du.se

Chris Bales

Solar Energy Research Center SERC,

Högskolan Dalarna, S-78188 Borlänge, Sweden

Johan Vestlund

Solar Energy Research Center SERC,

Högskolan Dalarna, S-78188 Borlänge, Sweden

ABSTRACT

In this study the monitoring results of prototype installation

of a recently developed solar combisystem have been

evaluated. The system, that uses a water jacketed pellet

stove as auxiliary heater, was installed in a single family

house in Borlänge/Sweden. In order to allow an evaluation

under realistic conditions the system has been monitored

for a time period of one year.

From the measurements of the system it could be seen that

it is important that the pellet stove has a sufficient buffer

store volume to minimize cycling. The measurements

showed also that the stove gives a lower share of the

produced heat to the water loop than measured under

stationary conditions. The solar system works as expected

and covers the heat demand during the summer and a part

of the heat demand during spring and autumn. Potential for

optimization exists for the parasitic electricity demand. The

system consumes 680 kWh per year for pumps, valves and

controllers which is more than 4% of the total primary

heating energy demand.

1. INTRODUCTION

Solar heating systems that provide domestic hot water and

space heating, so called solar combisystems, have become

more and more popular in the Middle and Northern

European countries. Solar combisystems usually require an

auxiliary heat source to be able to provide enough heat

even in the seasons with low solar irradiation. In Sweden,

electrical heaters and wood boilers are typically used as

auxiliary heaters in solar combisystems. In recent years

wood pellet boilers and stoves have also become a good

alternative. The design of solar combisystems has been

studied intensively in the IEA-SHC Task 26 “Solar

combisystems”. A number of systems have then been,

based on system simulations, optimised and improved. The

results from Task 26 including a variety of technical reports

and design tools are available for the public[6].

Within the Nordic research project REBUS a new

combined solar and pellet heating system for the Nordic

market has been designed, built and tested[4]. During this

project typical existing system solutions for this

combination have been investigated by the help of

measurements and computer simulations[2]. It has been

shown that these system solutions, due to their design and

size, are often not suitable for typical Swedish houses

without heating room. Also the thermal performance, such

as heat losses and solar savings, offered potential for

improvements. These finding have been included for the

design of the new system. The first prototype of the

REBUS system was tested intensively in the lab. The

second improved prototype was installed in a single family

house and has been monitored for a time period of one year.

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

868

2. SYSTEM DESCRIPTION

The REBUS system concept consists of two compact units;

the solar store unit and the technical unit that contain the

hydraulic components including the pellet boiler and an

auxiliary store for the hot water production (see also

Figure 2). Both units are built in cabinets of 60cmh 60cm

(width, depth) which are the standard dimensions for

kitchen and bathroom units like refrigerators and washing

machines. The system uses a 12 kW water jacketed pellet

stove with an internal water volume of 20 litre. The stove

heats an auxiliary standby store and the upper part of the

solar buffer store. The solar store comprises a water

volume of 360 litre and has, due to high efficient vacuum

insulation at the hottest parts of the store, a low UA-value

of about 1.8 W/K. The solar system can provide heat to

both stores. Instead of the separate water jacketed pellet

stove, an integrated or separate pellet boiler can be used

without any changes in the hydraulic layout. The system

is equipped with one central controller with a specifically

developed software for the control for all system

components except the pellet stove. A detailed description

can be found in [2].

In July 2006 a prototype of the REBUS system was

installed in a single family house in Borlänge/Sweden that

had earlier been heated with electrical radiators. In the main

house these heaters were replaced by water based radiators.

First the two units were installed without a pellet heater. In

the middle of October 2006 the water jacketed pellet stove

was added in the living room where a chimney was

accessible. Up until this point a 6 kW electrical heater in

the 80 litre standby store in the technical unit was used as

the auxiliary heater. The stove has an integrated 38 kg

pellet store which is fed manually by the owners (see

Figure 1, left). The technical and store units were installed

in a small room that earlier was used as a second bath room.

(see Figure 1, middle). The collector field of 10 m

(Figure

1, right) consists of four modules of Svesol premium AR

with a standard rated output of 465 kWh in Stockholm at

constant 50°C. It was placed on the main roof facing 40°E

with a slope of 40°.

3. MONITORING

Monitoring started at the end of July 2006, thus results are

presented for August 2006 onwards.

Fig. 1: The demonstration site in Borlänge, with (left) water jacketed stove, (middle) technical and store units in a bathroom

under the stairs, and (right) view of the 10 m

collector array on the roof.

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

869

The heat flows in all hydraulic loops have been measured

with calibrated sets of flow meters and temperature sensors.

The air flow through the stove has not been measured.

Instead, the measured values from the lab for the stove

efficiency have been used to calculate the flue gas heat

losses based on measured pellet use. Heat transferred from

the stove directly to the building was calculated as the

balance of the pellet energy and the flue gas losses together

with the measured heat transferred to the water loop. Two

separate electrical meters were installed to log the

electricity consumption of the system and the electrical

auxiliary heater. A simple pyranometer has been used to

measure the solar radiation. A number of temperature

sensors have been installed to give additional information

about the status of the system components and the

functioning of the system. Figure 2 shows the REBUS

system schematic with sensor positions. The electrical

meters and the pyranometer are not shown. The data were

logged using a Campbell CR10 data logger with attached

multiplexers. Average data values were stored with an

interval of one minute.

The owner has kept good records of bought energy for the

year previous to the installation, and these values are

presented in some of the figures. The amount of wood used

was estimated by the user and the tiled stove was assumed

to have an efficiency of 50%.

4. MONITORING RESULTS

In Figure 3 the heating energy supply for the building is

presented from January 2006 to June 2007. The data before

the installation of the REBUS system are calculated from

the readings of the house owner from the main electrical

meter and his records of wood use. The electricity for

heating has been calculated based on measured household

electricity in 2007. It can be seen that almost all bought

electricity for heating was replaced by pellet and solar

energy. About 200 kWh electricity were used by the

electrical back up heater in the standby store in October

2006. The pellet stove was installed in the middle of

October and not enough solar radiation was available,

which explains the use of the electrical heater that month.

Some electricity was also used in December 2007. Reason

here was that the 80 litre standby volume heated by the

Fig. 2: REBUS system schematic with sensor positions for the REBUS controller (blue with subscript c) and the

monitoring system (red with subscript d).

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

870

pellet stove was too little to cover the peak heat demand so

that the electrical heater in the standby store was backing

up the heating.

This has also caused a high number of starts and stops with

stove run times often not more than one hour. Consequently

in the end of December 2006, the hydraulics have been

modified so that also the upper third of the solar store,

which is connected in serial with the standby store, is

heated by the boiler.

Fig. 3: Monthly heat supply for space heating and domestic

hot water, *Electricity SH + DHW is the calculated

electricity use for SH + DHW before the detailed

monitoring.

This increases the standby volume to in total 200 litres. As

a result of this modification it can be seen that the number

of starts and stops have decreased drastically (Figure 4).

The average run time increased to about 3 to 4 hours per

start. Due to the longer run time of the stove also the

proportion of the useful heat delivered from the stove to the

water jacket has increased from 61% in December to 67%

in January. This is still lower than the average 80% for the

combustion range that is has been measured for the stove at

the Austrian test institute BfL[1].

In figure 5 the energy use for the monitored time period is

presented. The monthly hot water demand varies between

240 and 400 kWh. The annual space heating demand is

about 7400 kWh, which is relatively low for a building

with a heated area of approximately 130 m

and indicates a

good thermal insulation.

Fig. 4: Monthly heat delivery of the pellet stove and

number of starts and stops.

Fig. 5: Monthly heat use of the building, *Electricity SH +

DHW is the calculated electricity use for SH +

DHW before the detailed monitoring.

During one year the solar collectors have delivered about

2529 kWh which is a reasonable value considering the

small solar store volume, the non-optimal orientation of the

solar collectors and the low heat demand. In terms of

bought energy this gives a solar fraction of 19%.

5. DISCUSSION AND CONCLUSION

The newly developed solar combisystem has been

monitored for one year. For the most part the system is

working as expected. All loops and components are

properly controlled by the new controller software. Only

some fine adjustments of some parameters were necessary.

Most adjustments were necessary for the settings of the

3 SOLAR COLLECTOR TECHNOLOGIES AND SYSTEMS

871

pellet stove controller to ensure a proper interaction with

the main system. A modification of the hydraulic

connections was done to increase the buffer volume of the

pellet stove. Using only the 80 litre volume of the standby

store led to very short run times and many starts of the stove.

After the change the run times of the stove increased and the

number of starts and stops decreased drastically. Similar

findings have been reported also in other studies[3,5].

From the annual energy values in Table 1 the system

efficiency can be calculated using the following equation:

heatingforenergyprimarypliedsupannual

heatusefulannual

sys

=η

TABLE 1: ANNUAL HEAT SUPPLY AND USEFUL

HEAT

Annual heat supply (kWh)

Annual useful heat

(kWh)

Pellet 9319 Space heating 7611

Wood 1434 Hot water 3673

Solar 2543

Electricity 278

Total 13574 11284

With a primary energy factor of 0.4 for electricity the total

system efficiency is 0.83. Including also the parasitic

electricity consumption of pumps, valves etc. decreases the

system efficiency to 0.74. The parasitic electricity of 680

kWh accounts for almost 5 % or the total energy input to

the system. It is obvious that the parasitic electricity

consumption should be reduced e.g. by the use of more

efficient pumps which stand for the main part of the parasitic

consumption.

6. ACKNOWLEDGMENTS

We are grateful to the Nordic Energy Research and the

Dalarna University College for their financial support for

this work within the REBUS project.

7. REFERENCES

(1) BfL, “Prüfbericht Pelletskaminofen EVO AQUA.” BLT

Aktzahl: 053/04, Bundesanstalt für Landtechnik,

Wieselburg, Austria. 2003.

(2) F. Fiedler, “Combined solar and pellet heating systems-

Study of energy use and CO-emissions,” PhD thesis,

Mälardalen University, Västerås. 2006.

(3) F. Fiedler, C. Bales, and T. Persson, “Optimisation

Method for Solar Heating Systems in Combination

with Pellet Boilers/Stoves.” International Journal of

Green Energy, 4(3), 325 - 337. 2007.

(4) S. Furbo, A. Thür, C. Bales, F. Fiedler, J. Rekstad, M.

Meir, D. Blumberga, C. Rochas, T. Schifter-Holm, and

K. Lorenz, “Competitive Solar Heating Systems for

Residential Buildings (REBUS).” Byg, DTU,

Copenhagen, Denmark. 2006.

(5) A. Heinz, “Fortschrittliche Wärmespeicher zur Erhöhung

von solarem Deckungsgrad und Kesselnutzungsgrad

sowie Emissionsverringerung durch verringertes

Takten.” Technische Universität Graz, Institut für

Wärmetechnik, Graz, Austria. 2006.

(6) IEA, “International Energy Agency - Solar Heating and

Cooling Program.” IEA-Task 26. 2002.

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

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