Solar Air Heater – Supplement to Conventional Heating

As homeowners are considering measures to reduce energy consumption solar energy invariably becomes a topic of discussion. The challenge in taking the discussion to the next step is that building a new solar home or implementing an extensive retrofit of an existing home is extremely expensive and it is particularly daunting given the uncertainties regarding economic payback. There are, however, a number of incremental changes that could be considered, not only because of their relative affordability, but also because of reasonable certainties that tangible benefits will be realized. Solar thermal energy as a supplement to an existing heating system offers one such an opportunity.

Solar Air Heater

A solar air heater is an active system, in that it uses solar panels to collect the energy and fans to move the energy to other places. It is meant to be a supplement to an existing heating system, and it is best positioned when it can direct warm air directly into a room with a lot of daytime use. It typically pulls cooled air from the bottom of a room, circulates it through a solar collector, and then blows the warmed air back into the room. There are various types:

• Roof, wall or window mounted solar collectors heat the air that passes through them and are most effective when facing the south and where the sunlight is not obstructed by trees or tall buildings.
• Smaller solar collector window units, mounted on a south facing window, extend through the window. They avoid the need for ducts or vents. However, these act as simple transfer systems, have no heat storage capability, and are ineffective at night or on cloudy / overcast days.
• Heat sinks, applicable to the larger systems, can absorb and hold heat for a short time. Any excess heat generated during the day is transferred to the heat sink for storage to be later transferred to the home when the sun goes down. Though heat sinks allow for the extension of solar thermal energy into the night, it is expensive and can be hazardous to one’s health. The moisture that collects in a heat sink can become mold and bacterial growth, which can accompany the warm air that is blown into the home.

The Cost and Benefits of a Solar Air Heater

Commercial solar air heaters range from $1,000 for a single room heating system to $6,000 for a large space or multi-room application. Designed to replace between 40 and 80 percent of conventional heating, these supplemental heating sources are most cost-effective providing for 50 percent of the home’s heat.

As this represents an additional expense, there is a natural tendency to do it yourself. Short of simple unit installations which may be within the capacity of a “do it yourself,” these systems often require building permits, are large and heavy enough to exceed roof load limits, and typically involve duct work and electrical wiring. Therefore, homeowners embarking on this project should allow additional funds for a contractor experienced in solar installation technology.

The financial benefits of installing and operating a solar air heater vary widely, based on the condition of the home and its location:

• A poorly sealed and insulated home will not benefit significantly from the investment. Solar heated air leaks the same as conventionally heated air.
• Best results are achieved in areas with long, cold, but sunny winters.
• In warmer climates with short winters, designing the system to supplement water heating during the summer increases cost effectiveness and accelerates ROI.