Phase Change Heatstorage
Traditionally solar thermal has only been used in the UK for water heating.
Though it is of course possible to oversize a system to enable space heating via radiators or underfloor heating, the problem has always been the same:
When excess heat energy is availble (during the summer months) there is little or no requirement for room heat and when room heating is required (during the winter) there is little or no extra heat energy available.
The solution is to install a quantity of phase change material with a very high latent heat capacity storing a relatively large quantiy of heat during the solar rich months so this heat can be given off when required.
The temperature that the heat is stored at can be varied by the use of different PCMs (phase change material) and for space heating would typically be between 21-28oC.