A solar combisystem provides both solar space heating and

cooling Cooling is removal of heat, usually resulting in a lower temperature and/or phase change. Temperature lowering achieved by any other means may also be called cooling.ASHRAE Terminology, https://www.ashrae.org/technical-resources/free-resources/as ...

as well as hot water from a common array of

solar thermal collector A solar thermal collector collects heat by absorbing sunlight. The term "solar collector" commonly refers to a device for solar hot water heating, but may refer to large power generating installations such as solar parabolic troughs and so ...

s, usually backed up by 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 (also known as heat networks or teleheating) is a system for distributing heat generated in a centralized location through a system of insulated pipes for residential and commercial heating requirements such as space heating a ...

tend to be called

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 (central solar heating plants - CSHPs) and distributed through dis ...

schemes. Many types of solar combisystems are produced - over 20 were identified in the first international survey, conducted as part of IEA SHC 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 "Passive house" (german: Passivhaus) is a voluntary standard for energy efficiency in a building, which reduces the building's ecological footprint. It results in ultra-low energy buildings that require little energy for space heating or coo ...

''-type buildings; even up to 100% where a large interseasonal 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 A ground source heat pump (also geothermal heat pump) is a heating/cooling system for buildings that uses a type of heat pump to transfer heat to or from the ground, taking advantage of the relative constancy of temperatures of the earth through ...

is used, the combisystem is called geosolar) and, sometimes,

rechargeable batteries A rechargeable battery, storage battery, or secondary cell (formally a type of energy accumulator), is a type of electrical battery which can be charged, discharged into a load, and recharged many times, as opposed to a disposable or prima ...

. During 2001, around 50% of all the domestic solar collectors installed in

Austria Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...

, Switzerland,

Denmark ) , song = ( en, "King Christian stood by the lofty mast") , song_type = National and royal anthem , image_map = EU-Denmark.svg , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of Denmark , establish ...

, and

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and the ...

were to supply combisystems, while in Sweden it was greater. In

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

, 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 is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

since the mid-1980s. Some combisystems can incorporate solar thermal cooling in summer.

Classification

Following the work of IEA SHC 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 Stratification may refer to: Mathematics * Stratification (mathematics), any consistent assignment of numbers to predicate symbols * Data stratification in statistics Earth sciences * Stable and unstable stratification * Stratification, or st ...

); 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

(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 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. The term ...

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 collectors through

underfloor central heating Underfloor heating and cooling is a form of central heating and cooling that achieves indoor climate control for thermal comfort using hydronic or electrical heating elements embedded in a floor. Heating is achieved by conduction, radiation and ...

pipes embedded in the concrete floor slab. The floor slab is thickened to provide

thermal mass In building design, thermal mass is a property of the mass of a building that enables it to store heat and provide inertia against temperature fluctuations. It is sometimes known as the thermal flywheel effect. The thermal mass of heavy structura ...

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 A nomogram (from Greek , "law" and , "line"), also called a nomograph, alignment chart, or abac, is a graphical calculating device, a two-dimensional diagram designed to allow the approximate graphical computation of a mathematical function ...

s (such as the one developed for IEA SHC 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 coolingbr>
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 water and for regular

central heating A central heating system provides warmth to a number of spaces within a building from one main source of heat. It is a component of heating, ventilation, and air conditioning (short: HVAC) systems, which can both cool and warm interior spaces. ...

and

underfloor heating Underfloor heating and cooling is a form of central heating and cooling that achieves indoor climate control for thermal comfort using hydronic or electrical heating elements embedded in a floor. Heating is achieved by conduction, radiation and ...

, as well as those used in the auxiliary systems -

microgeneration Microgeneration is the small-scale production of heat or electric power from a "low carbon source," as an alternative or supplement to traditional centralized grid-connected power. Microgeneration technologies include small-scale wind turbin ...

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 water systems had been capable of meeting a significant portion of domestic hot water requirements in many

climate zone Climate classifications are systems that categorize the world's climates. A climate classification may correlate closely with a biome classification, as climate is a major influence on life in a region. One of the most used is the Köppen climate ...

s. However it was only with the development of reliable

low-energy building A low-energy house is characterized by an energy-efficient design and technical features which enable it to provide high living standards and comfort with low energy consumption and carbon emissions. Traditional heating and active cooling systems ...

techniques in the last decades of the century that extending such systems for space heating became realistic in temperate and colder

climatic zone Climate classifications are systems that categorize the world's climates. A climate classification may correlate closely with a biome classification, as climate is a major influence on life in a region. One of the most used is the Köppen climate ...

s. 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

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.

External links

IEA SHC Task 26 official siteTest of Thermal Solar Systems for Hot Water and Space Heating (June 2004)
* ttp://www.spf.ch/spf.php?lang=en&fam=2&tab=3 Combisystem test reports - Mostly in German

References

*''Solar Heating Systems for Houses – A Design Handbook for Solar Combisystems'', James and James, (by the Task 26 team)

Footnotes

{{HVAC Geothermal energy Solar power Solar thermal energy Heating, ventilation, and air conditioning Residential heating