Active solar home heating employs solar thermal energy to heat space in the home. First, solar collectors transfer the sun’s heat to air or liquid. Once the solar radiation is absorbed, the air or fluid is transferred either directly to a space in the home or to a storage tank. Often a back-up system provides any additional heat that the solar home heater cannot produce.
Learn more about different types of solar heating:
- air space heating is best for directly heating rooms
- liquid space heating is best for central heating
Cost and Performance
Solar space heating systems are most economical when they are used for the majority of the year – that is, in cold climates with good solar resources where the home requires heating – and when used in place of more expensive heating methods.
EnergySavers.gov recommends installing a solar heating system to provide 40%-80% of your heating needs. A heating system to satisfy your full heating needs may be impractical or expensive. Also, many building codes and loan lenders require a back-up heating source.
Most solar heating systems have at least a 10 year warranty, and some states offer tax credits for home solar thermal heating. If using a liquid space heating system, it is more economical to use the solar collector for hot water heating, too.
Because air-based systems produce heat earlier and later in the day, solar air heaters may produce more usable energy over a longer time period.
Solar Air Home Heating
Air in the solar collectors cannot freeze in the winter, and small cracks in the collectors or piping are not problematic. But air is a less efficient than liquid for transferring heat.
Air space heating systems are usually room air heaters, which directly heat individual rooms. A fan pulls air from the room into the collector. The air is heated as it travels through the collector, and is then blown back into the room. There are two ways to mount a solar air heater:
- roof-mounted room heaters need ducts to transport air from the collector to the room
- wall-mounted room heaters are placed on a south-facing wall, with holes cut through the wall to allow the air to pass through to the room
Liquid solar thermal heating systems are best for central heating in the home.
Solar Water Home Heating
The solar collectors use either water or a non-toxic glycol antifreeze to absorb the thermal energy. With the help of a controller, a circulating pump moves the fluid through the collector. The liquid flows quickly through the collector, resulting in an increase in temperature of 10°–20°F (5.6°–11°C).
The warm liquid flows to a storage tank or a heat exchanger. The heat is then spread through the home via one of the methods described below.
Heated liquid from the solar collector travels through pipes in a concrete slab flooring, usually covered with tiles. The heat radiates to the room.
This kind of solar home heating system can work without a heat storage tank, although a tank is needed to control the temperature.
These systems take longer to warm up but, once operating, provide a consistent temperature. Carpets and rugs will reduce the effectiveness of radiant floors.
Hot Water Baseboards or Radiators
These need water heated between 160° and 180°F (71° and 82°C). However, flat-plate solar collectors – the most common type of collector – heat liquid to a lower temperature. In this case, the liquid from the collectors needs to be heated more by the backup system, or that a higher temperature collector be used (such as an evacuated tube collector).
Central Forced-Air System
This kind of system works through a heat exchanger in the air duct. As air from inside the home passes over the heat exchanger, the liquid inside heats the air. The coil must be big enough to transfer enough heat to the air at the collector’s lowest operating temperature.