Solar space heating
Appropriately designed and orientated buildings are able to benefit from direct solar gains from sunshine through windows warming floors and walls. Indirect solar gains may be obtained by constructing walls and floors from dense (high thermal mass) materials. This creates a solar thermal store which absorbs solar radiation during the day and releasing heat when it is required.
Sunrooms, conservatories and greenhouses attached to a house can provide (isolated) passive solar gains by the circulation of warmed air into living spaces.
NB These spaces are often misused. By using conservatories as normal living spaces, i.e. providing additional heating and/or permanently open access from adjoining rooms, much energy can be wasted.
The Trombe wall is another method of passive solar space heating. This employs an area of glazed external wall with high thermal mass and with an air gap between the wall and glazing. Ventilation slots are provided at the bottom and top of the wall permitting air to circulate, by convection, from the room through the airspace where it is heated, and then back in the room. Solar radiation is absorbed by and stored in the wall.
Passive solar design needs to provide for potential solar overheating problems which may occur during summer months and even in winter. Solutions include: sizing and placement of windows; providing a roof overhang or sunshading to limit direct solar radiation in summer, whilst in winter months, when the sun's angle is low, maximising solar gain; passive stack or wind tower ventilation techniques.
Active Solar Space Heating
The two main forms of active solar space heating are solar liquid collectors
and solar air collectors. Solar liquid collectors (i.e. solar flat plate collectors, described on the solar water heating page), can be used to provide underfloor heating. Space heating applications require a larger area of solar collectors. Ideally the heat from solar collectors are stored in an efficient thermal store. The thermal store helps to regulate supply and demand for space heating and hot water throughout the day.
Solar air collector
In its simplest form, a Solar air collector resembles the flat plate solar collector used for heating water. A black absorber plate is housed in an insulated and glazed enclosure. However, rather than solar energy being transferred to liquid filled pipes in thermal contact as with the flat plate collector, air drawn by a fan through the collector extracts heat from the absorber plate. Typical uses are preheating a ventilation system and/or preheating water via an air-to-water heat exchanger.
Another use of solar air heating uses the heat from solar photovoltaic panels. Not surprisingly perhaps, photovoltaics get hot and as the efficiency of solar photovoltaic panels decreases with increase in temperature, they need to be cooled through ventilation. Combined PV air / water heating utilises heat from PVs in the manner of a solar air collector.
Solar transpired air collectors
Solar transpired air collectors are used mainly for commercial applications such as contributing to space heating on large buildings. They are constructed by erecting unglazed perforated metal cladding on south-facing walls, leaving an airway behind. The cladding is heated by the sun. Fans at the top of the wall draw air through the perforations, up the airway and into ducting to perfom a preheating function for the HVAC system.
General solar space heating info.
Trombe wall info.