Solar air Heating systems

Solar space heating is usually based on hot air (heated in the panels), pumped into the rooms by fans or through a forced air system. But there are also hydronic solutions, based on hot water and radiators or radiant floor... Though simple in its principles, solar air heating systems can pose problems that should be conveniently addressed.

Types of solar air heating systems

Solar air/space heating systems can be based on 1) warm air or on a 2) liquid medium (hydronic systems)

Most solar space heating are hot air systems and are based on solar panels and a fan or fans to blow the hot air into the house... More complex systems involve also storage equipment and activation and deactivation controls.

But solar space heating solutions can also be hydronic, that is, based on solar heated water. In this case they typically combine with baseboards or radiant floor heating systems.

Solar air space heating solutions are usually designed by local installers, taking into account local conditions.

See:
Solar radiant heating
Solar Baseboard Heating

Simpler solar Air heating systems and Climate

Simple solar air heating systems are a good solution to solve problems of ventilation or seasonal coldness in a room, and are largely used in non-residential heating (warehouses, hangars...).

But since they haven't activation and deactivation sensors and controls, or storage components, they can inject too much hot air into the house, or cause other unwanted temperature swings.

Besides, when only used for house space heating they may be useless during a large part of the year, in many climates. And that' s a big disadvantage.

Solar Air Heating Design

Solar Air heating & Forced air ventilation

More sophisticated solar air heating systems use forced air ventilation and ductwork. Air is often drawn from inside the room through the bottom of the solar panels (on the roof), where the air is heated and blown out through a duct located in the top, linked to other ductwork and to the forced air ventilation (see image at left, from AAASolar).

Collectors type

The simpler solar air-space heating systems are often based on unglazed air flat-plate panels, but glazed air flat panels are also common.

These solar air collectors are similar in their operation to liquid solar panels. The only difference is on the use of air - instead of water or other liquid - as the medium of heat transfer. Solar air panels used to be of questionable construction some years ago, and their efficiency was very low, but there are now well-built panels.

Obviously, hydronic solutions require other types of solar panels: common liquid solar flat panels and also evacuated-tube panels. See: Different types of solar panels.

Solar air space heating systems Price

Though simple solar air space heating systems are relatively inexpensive, more complex systems with storage capacities, blowers, ductwork, forced air systems and large solar panels areas can be much more expensive than the more common solar hot water systems.

Location & Solar collectors pitching

Solar air heating systems are very sensitive to the tilt and orientation of the panels or to the impact of the surrounding landscaping. Make sure that the panels aren't shaded by trees, buildings or other obstructions. Panels are typically oriented within 15 degrees of true South (or North, in the southern hemisphere).

Mounting the collectors on a vertical wall is often a good solution: it prevents over-heating in summer (when the sun is higher) and provides a good efficiency in winter, when the sun is lower and the vertical position of the panels is favorable. For the same reasons, panels mounted on roofs should have a relatively high pitch.

See: Solar Panels Location and Tilt

Sizing a solar Air heating system

Solar air heating requires a larger area of solar panels than common solar water heating systems.

2 square feet of collector for each 10 square feet of the footprint of the building/room is a common rule of thumb for sizing a solar air heating system. But only a experienced solar professional can determine the best size and the best configuration, linking it to local climate and weather patterns.

Elements like home insulation, glazing area, climate, landscape, solar resources and the exact purpose of the project should be taken into account.