Solar combisystem

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 by an auxiliary non-solar heat source.

Solar combisystems may range in size from those installed in one or more of the following three types of heating systems. Those serving larger groups of district heating properties tend to be called central solar heating schemes.

A large number of different types of solar combisystems are produced in the first international survey, conducted as part of the IEA SHC Task 14 [1] in 1997. however, as different systems have been developed in different countries. Prior to the 1990s such systems are built for each property. Since then commercialized packages have been developed and 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 interseasonal thermal store or concentrating solar thermal heat is used. The remaining heat requirement is supplied by the supplier. Such auxiliary heat sources aussi May use other renewable energy sources (when a geothermal heat pump is used, the combisystem s’intitule geosolar) [2] and, sometimes, rechargeable batteries .

During 2001, around 50% of 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 was installed (900,000 m2), 25% was for combisystem installations. Combisystems have also been installed in Canada since the mid-1980s.

Some combisystems can be used for solar thermal cooling in summer. [3]


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 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 the air of a tank to warmer at the top) is important that the combisystem can supply hot or cold water at different temperatures.

Heat and cool storage categories
Category Description
AT 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.
C Heat and cool management using natural convection in storage tanks and / or 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 and multiple pipes and / or multiple pipes and outlets.
Auxiliary heat and cool management categories
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 by solar collectors (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 and the auxiliary heater connected in series of the space heating loop.

A solar combisystem can therefore be described as being of type B / DS, CS, etc.

These types of systems can be configured in many different ways. For the individual house they may – or may not – have the storage tanks, the controls and auxiliary heater and the integrated coolant in a single prefabricatedpackage. In contrast, there are also large centralized 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 pipes embedded in the concrete floor slab. The floor slab is thickened to provide thermal mass and so the heat and cool of 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 made easily, but accurate predictions remain difficult.

Tools for designing solar combisystems are available, varying, from manufacturer’s guidelines to nomograms (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, [4] which can be used for basic system sizing) and the free SHWwin (Austria, in German [5] ). Other commercial systems are available.

Solar combisystems generally use underfloor heating and cooling [1] .

Concentrating solar thermal technology can be used to make collectors as small as possible.


Solar combisystems use similar technologies To Those used for solar hot water and for regular central heating and underfloor heating , as well as Those used in the auxiliary systems – Microgeneration gold Otherwise technologies.

The single element to combisystems is that these technologies are combined, and the control systems used to integrate them, plus any stratifier technology that may be employed.

Relationship to low energy building

By the end of the 20th century solar hot water systems HAD beens able of meeting a significant portion of domestic hot water requirements 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 such climatic systems have become climatic .

As heat demand reduces, the overall size and cost of the system is reduced, and the lower water temperatures may be more often 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.

Incomplete heating systems in the field of low-energy buildings, where the temperature of the room is greater than that of the room temperature and the ventilation rates, when compared to conventional buildings.

See also

  • Geothermal heat pump
  • Renewable heat concentrating solar (used in these systems to produce heat and not to make electricity)
  • Renewable energy
  • Solar cooling
  • Solar heating
    • Central solar heating
  • Solar thermal energy

External links

  • IEA SHC Task 26 official site
  • The European Altener Program Project: Solar Combisystems
  • Test of Thermal Solar Systems for Hot Water and Space Heating (June 2004)
  • Interseasonal Heat Transfer integrates solar thermal collection and thermal storage
  • Combisystem test reports – Mostly in German


  • Solar Heating Systems for Houses – A Design Handbook for Solar Combisystems , James and James, ISBN  1-902916-46-8 (by Task 26 team)


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