Solar combisystem
Encyclopedia
A solar combisystem provides both solar space heating and cooling as well as hot water
from a common array of solar thermal collectors, usually backed up an auxiliary non-solar heat source.
Solar combisystems may range in size from those installed in individual properties to those serving several in a block heating scheme. Those serving larger groups of properties district heating
tend to be called central solar heating
schemes.
A large number of different types of solar combisystems are produced - over 20 were identified in the first international survey, conducted as part of IEA
Task 14 in 1997. The systems on the market in a particular country may be more restricted, however, as different systems have tended to evolve in different countries. Prior to the 1990s such systems tended to be custom-built for each property. Since then commercialised packages have developed and are now generally used.
Depending on the size of the combisystem installed, the annual space heating contribution can range from 10% to 60% or more in ultra-low energy Passivhaus type buildings; even up to 100% where a large seasonal thermal store
or concentrating solar thermal heat is used. The remaining heat requirement is supplied by one or more auxiliary sources in order to maintain the heat supply once the solar heated water is exhausted. Such auxiliary heat sources may also use other renewable energy
sources (when a geothermal heat pump is used, the combisystem is called geosolar) and, sometimes, rechargeable batteries
.
During 2001, around 50% of all the domestic solar collectors installed in Austria
, Switzerland
, Denmark
and Norway
were to supply combisystems, while in Sweden
it was greater. In Germany
, where the total collector area installed (900,000 m2) was much larger than in the other countries, 25% was for combisystem installations. Combisystems have also been installed in Canada
since the mid 1980s.
Some combisystems can incorporate solar thermal cooling in summer.
Task 26 (1998 to 2002), solar combisystems can be classified according to two main aspects; firstly by the heat (or cool) storage category (the way in which water is added to and drawn from the storage tank
and its effect on stratification
); secondly by the auxiliary heat (or cool) management category (the way in which non-solar-thermal auxiliary heaters or coolers can be integrated into the system).
Maintaining stratification
(the variation in water temperature from cooler at the foot of a tank to warmer at the top) is important so that the combisystem can supply hot or cool water and space heating and cooling water at different temperatures.
A solar combisystem may therefore be described as being of type B/DS, CS, etc.
Within these types, systems may be configured in many different ways. For the individual house they may – or may not – have the storage tanks, controls and auxiliary heater and cooler integrated into a single prefabricated
package. In contrast, there are also large centralised systems serving a number of properties.
The simplest combisystems – the Type A – have no "controlled storage device". Instead they pump warm (or cool) water from the solar collector
s through underfloor central heating pipes embedded in the concrete floor slab. The floor slab is thickened to provide thermal mass
and so that the heat and cool from the pipes (at the bottom of the slab) is released during the evening.
Tools for designing solar combisystems are available, varying from manufacturer's guidelines to nomogram
s (such as the one developed for IEA
Task 26) to various computer simulation
software of varying complexity and accuracy.
Among the software and packages are CombiSun (released free by the Task 26 team, which can be used for basic system sizing) and the free SHWwin (Austria, in German ). Other commercial systems are available.
Solar combisystems generally use underfloor heating and cooling http://www.mining.ubc.ca/files/EnergyCourse2005.pdf.
Concentrating solar thermal technology may be used to make the collectors as small as possible.
and for regular central heating
and underfloor heating
, as well as those used in the auxiliary systems - microgeneration
technologies or otherwise.
The element unique to combisystems is the way that these technologies are combined, and the control systems used to integrate them, plus any stratifier technology that might be employed.
systems had been capable of meeting a significant portion of domestic hot water in many climate zones. However it was only with the development of reliable low-energy building techniques in the last decades of the century that extending such systems for space heating became realistic in temperate and colder climatic zones.
As heat demand reduces, the overall size and cost of the system is reduced, and the lower water temperatures typical of solar heating may be more readily used - especially when coupled with underfloor heating
or wall heating. The volume occupied by the equipment also reduces, which also increases the flexibility of its location.
In common with other heating systems in low-energy buildings, system performance is more sensitive to the number of occupants, room temperature and ventilation rates, when compared to regular buildings where such effects are small in relation to the higher overall energy demand.
Water heating
Water heating is a thermodynamic process using an energy source to heat water above its initial temperature. Typical domestic uses of hot water are for cooking, cleaning, bathing, and space heating...
from a common array of solar thermal collectors, usually backed up an auxiliary non-solar heat source.
Solar combisystems may range in size from those installed in individual properties to those serving several in a block heating scheme. Those serving larger groups of properties district heating
District heating
District heating is a system for distributing heat generated in a centralized location for residential and commercial heating requirements such as space heating and water heating...
tend to be called central solar heating
Central solar heating
Central solar heating is the provision of central heating and hot water from solar energy by a system in which the water is heated centrally by arrays of solar thermal collectors and distributed through district heating pipe networks .For block systems, the solar collectors are...
schemes.
A large number of different types of solar combisystems are produced - over 20 were identified in the first international survey, conducted as part of IEA
International Energy Agency
The International Energy Agency is a Paris-based autonomous intergovernmental organization established in the framework of the Organisation for Economic Co-operation and Development in 1974 in the wake of the 1973 oil crisis...
Task 14 in 1997. The systems on the market in a particular country may be more restricted, however, as different systems have tended to evolve in different countries. Prior to the 1990s such systems tended to be custom-built for each property. Since then commercialised packages have developed and are now generally used.
Depending on the size of the combisystem installed, the annual space heating contribution can range from 10% to 60% or more in ultra-low energy Passivhaus type buildings; even up to 100% where a large seasonal thermal store
Seasonal thermal store
A seasonal thermal store is a store designed to retain heat deposited during the hot summer months for use during colder winter weather...
or concentrating solar thermal heat is used. The remaining heat requirement is supplied by one or more auxiliary sources in order to maintain the heat supply once the solar heated water is exhausted. Such auxiliary heat sources may also use other renewable energy
Renewable energy
Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable . About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from...
sources (when a geothermal heat pump is used, the combisystem is called geosolar) and, sometimes, rechargeable batteries
Rechargeable battery
A rechargeable battery or storage battery is a group of one or more electrochemical cells. They are known as secondary cells because their electrochemical reactions are electrically reversible. Rechargeable batteries come in many different shapes and sizes, ranging anything from a button cell to...
.
During 2001, around 50% of all the domestic solar collectors installed in Austria
Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...
, Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
, Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
and Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
were to supply combisystems, while in Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
it was greater. In Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, where the total collector area installed (900,000 m2) was much larger than in the other countries, 25% was for combisystem installations. Combisystems have also been installed in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
since the mid 1980s.
Some combisystems can incorporate solar thermal cooling in summer.
Classification
Following the work of IEAInternational Energy Agency
The International Energy Agency is a Paris-based autonomous intergovernmental organization established in the framework of the Organisation for Economic Co-operation and Development in 1974 in the wake of the 1973 oil crisis...
Task 26 (1998 to 2002), solar combisystems can be classified according to two main aspects; firstly by the heat (or cool) storage category (the way in which water is added to and drawn from the storage tank
Storage tank
A storage tank is a container, usually for holding liquids, sometimes for compressed gases . The term can be used for reservoirs , and for manufactured containers. The usage of the word tank for reservoirs is common or universal in Indian English, American English and moderately common in British...
and its effect on stratification
Stratification (water)
Water stratification occurs when water masses with different properties - salinity , oxygenation , density , temperature - form layers that act as barriers to water mixing...
); secondly by the auxiliary heat (or cool) management category (the way in which non-solar-thermal auxiliary heaters or coolers can be integrated into the system).
Maintaining stratification
Stratification (water)
Water stratification occurs when water masses with different properties - salinity , oxygenation , density , temperature - form layers that act as barriers to water mixing...
(the variation in water temperature from cooler at the foot of a tank to warmer at the top) is important so that the combisystem can supply hot or cool water and space heating and cooling water at different temperatures.
| Category | Description |
|---|---|
| A | No controlled storage device for space heating and cooling. |
| B | Heat and cool management and stratification enhancement by means of multiple tanks and/or by multiple inlet/outlet pipes and/or by three- or four-way valves to control flow through the inlet/outlet pipes. |
| C | Heat and cool management using natural convection Convection Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids.... in storage tanks and/or between them to maintain stratification to a certain extent. |
| D | Heat and cool management using natural convection in storage tanks and built-in stratification devices. |
| B/D | Heat and cool management by natural convection in storage tanks and built-in stratifiers as well as multiple tanks and/or multiple inlet/outlet pipes and/or three- or four-way valves to control flow through the inlet/outlet pipes. |
| Category | Description |
|---|---|
| M (mixed mode) | The space heating loop is fed from a single store heated by both solar collectors and the auxiliary heater. |
| P (parallel mode) | The space heating and cooling loop is fed alternatively by the solar collector Solar collector -See also:*Solar thermal collector*Solar water heating*Solar air heating*Photovoltaic module*Renewable heat*Concentrating solar power... s (or a solar water storage tank), or by the auxiliary heater or cooler; or there is no hydraulic connection between the solar heat and cool distribution and the auxiliary heat emissions. |
| S (serial mode) | The space heating and cooling loop may be fed by the auxiliary heater, or by both the solar collectors (or a solar water storage tank) and the auxiliary heater connected in series on the return line of the space heating loop. |
A solar combisystem may therefore be described as being of type B/DS, CS, etc.
Within these types, systems may be configured in many different ways. For the individual house they may – or may not – have the storage tanks, controls and auxiliary heater and cooler integrated into a single prefabricated
Prefabrication
Prefabrication is the practice of assembling components of a structure in a factory or other manufacturing site, and transporting complete assemblies or sub-assemblies to the construction site where the structure is to be located...
package. In contrast, there are also large centralised systems serving a number of properties.
The simplest combisystems – the Type A – have no "controlled storage device". Instead they pump warm (or cool) water from the solar collector
Solar collector
-See also:*Solar thermal collector*Solar water heating*Solar air heating*Photovoltaic module*Renewable heat*Concentrating solar power...
s through underfloor central heating pipes embedded in the concrete floor slab. The floor slab is thickened to provide thermal mass
Thermal mass
Thermal mass is a concept in building design which describes how the mass of the building provides "inertia" against temperature fluctuations, sometimes known as the thermal flywheel effect...
and so that the heat and cool from the pipes (at the bottom of the slab) is released during the evening.
Combisystem design
The size and complexity of combisystems, and the number of options available, mean that comparing design alternatives is not straightforward. Useful approximations of performance can be produced relatively easily, however accurate predictions remain difficult.Tools for designing solar combisystems are available, varying from manufacturer's guidelines to nomogram
Nomogram
A nomogram, nomograph, or abac is a graphical calculating device developed by P.E. Elyasberg, a two-dimensional diagram designed to allow the approximate graphical computation of a function: it uses a coordinate system other than Cartesian coordinates...
s (such as the one developed for IEA
International Energy Agency
The International Energy Agency is a Paris-based autonomous intergovernmental organization established in the framework of the Organisation for Economic Co-operation and Development in 1974 in the wake of the 1973 oil crisis...
Task 26) to various computer simulation
Computer simulation
A computer simulation, a computer model, or a computational model is a computer program, or network of computers, that attempts to simulate an abstract model of a particular system...
software of varying complexity and accuracy.
Among the software and packages are CombiSun (released free by the Task 26 team, which can be used for basic system sizing) and the free SHWwin (Austria, in German ). Other commercial systems are available.
Solar combisystems generally use underfloor heating and cooling http://www.mining.ubc.ca/files/EnergyCourse2005.pdf.
Concentrating solar thermal technology may be used to make the collectors as small as possible.
Technologies
Solar combisystems use similar technologies to those used for solar hot waterSolar hot water
Solar water heating or solar hot water systems comprise several innovations and many mature renewable energy technologies that have been well established for many years...
and for regular central heating
Central heating
A central heating system provides warmth to the whole interior of a building from one point to multiple rooms. When combined with other systems in order to control the building climate, the whole system may be a HVAC system.Central heating differs from local heating in that the heat generation...
and underfloor heating
Underfloor heating
Underfloor heating and cooling is a form of central heating and cooling which achieves indoor climate control for thermal comfort using conduction, radiation and convection...
, as well as those used in the auxiliary systems - microgeneration
Microgeneration
Microgeneration is the small-scale generation of heat and power by individuals, small businesses and communities to meet their own needs, as alternatives or supplements to traditional centralized grid-connected power...
technologies or otherwise.
The element unique to combisystems is the way that these technologies are combined, and the control systems used to integrate them, plus any stratifier technology that might be employed.
Relationship to low energy building
By the end of the 20th century solar hot waterSolar hot water
Solar water heating or solar hot water systems comprise several innovations and many mature renewable energy technologies that have been well established for many years...
systems had been capable of meeting a significant portion of domestic hot water in many climate zones. However it was only with the development of reliable low-energy building techniques in the last decades of the century that extending such systems for space heating became realistic in temperate and colder climatic zones.
As heat demand reduces, the overall size and cost of the system is reduced, and the lower water temperatures typical of solar heating may be more readily used - especially when coupled with underfloor heating
Underfloor heating
Underfloor heating and cooling is a form of central heating and cooling which achieves indoor climate control for thermal comfort using conduction, radiation and convection...
or wall heating. The volume occupied by the equipment also reduces, which also increases the flexibility of its location.
In common with other heating systems in low-energy buildings, system performance is more sensitive to the number of occupants, room temperature and ventilation rates, when compared to regular buildings where such effects are small in relation to the higher overall energy demand.
See also
- Geothermal heat pump
- Renewable heatRenewable heatRenewable heat is an application of renewable energy and it refers to the renewable generation of heat, rather than electrical power ....
concentrating solar (used in theses systems to produce heating and not to make electricity) - Renewable energyRenewable energyRenewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable . About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from...
- Seasonal thermal storeSeasonal thermal storeA seasonal thermal store is a store designed to retain heat deposited during the hot summer months for use during colder winter weather...
- Solar cooling
- Solar heating
- Central solar heatingCentral solar heatingCentral solar heating is the provision of central heating and hot water from solar energy by a system in which the water is heated centrally by arrays of solar thermal collectors and distributed through district heating pipe networks .For block systems, the solar collectors are...
- Central solar heating
- Solar thermal energySolar thermal energySolar thermal energy is a technology for harnessing solar energy for thermal energy . Solar thermal collectors are classified by the United States Energy Information Administration as low-, medium-, or high-temperature collectors. Low-temperature collectors are flat plates generally used to heat...