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); 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.
| 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 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 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 (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 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 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.
Read more about this topic: Solar Combisystem