A solar heating panel is a device that traps solar radiation and delivers that energy as usable heat inside a structure. This radiation includes everything from infrared through the visible spectrum to ultraviolet.

What's a passive solar heating panel?

A passive solar heating panel requires only the sun - no fans, blowers, or pumps are needed for it to operate at peak efficiency. It uses the heat produced to provide a convective flow that moves the heat from the collector into the structure. This means that the installed panel has a zero operating cost.

Do solar panels replace my furnace system?

Not unless the structure is specifically designed to be solar heated. For nearly all existing structures suitable for solar panel installation, solar heating panels may provide substantial reduction of fuel consumption, with a corresponding reduction in fuel and operating costs.

How does it work?

The DeSoto Solar heating panel has an efficiently combined radiation trap and heat exchanger. The radiation trap absorbs solar energy and the exchanger releases it into the air inside the panel. The heated air rises and is heated continuously until it flows out of the collector and into the structure. As heated air flows out of the collector, cool air is drawn into the collector from near the structure's floor. The greater the amount of energy collected by the radiation trap, the higher the temperature of the heat exchanger and the faster the resulting airflow. The DeSoto Solar heating panel is designed to produce a maximum temperature between 110°F and 115°F. Unlike some solar panels, the airflow inside the collector body is controlled in such a way that the heating panel can't run in reverse at night in extreme cold.

The vertical orientation produces two important behaviors: [1] The panel operates most efficiently in mid-winter. In mid-summer, when the sun is high in the sky, most of the radiation is reflected (downward) by the polycarbonate glazing; and [2] if the ground in front of the panel is snow-covered, the snow reflects a significant amount energy into the panel's radiation trap.

How much heat is produced?

As Mark Twain (mis)quoted: "There are three kinds of lies: lies, damned lies, and statistics." The only honest answer to this question is: The quantity of heat produced depends on [1] orientation, [2] shading, [3] latitude, and [4] prevailing weather patterns. Let's briefly examine each of these variables:

Orientation

Our collector is designed to be installed vertically. It will trap the greatest amount of solar radiation if it faces true (not magnetic) south; and the least if it faces true north. If it faces a little east of south it will trap more energy in the morning; and if it faces a little west of south it will trap more energy in the afternoon.

Shading

Shading occurs when solar radiation is blocked from reaching the collector by plants, other structures, an object, or even the planet itself (night). The collector can only trap the energy that reaches it.

Latitude

The collector is only useful in the temperate zones. In the equatorial zone the sun is too directly overhead; and in the polar regions the sun remains below the horizon throughout the heating season. Within the temperate zones, efficiency will be highest as the distance from the equator increases.

Prevailing weather patterns

Some areas like Southern California, Arizona, Minnesota, and Florida normally receive above average amounts of solar radiation while other areas such as Seattle receive below average amounts. Although this is a form of shading, it's unlike the clear-cut behavior of object shading because the weather is a difficult-to-predict variable.

How much solar collector is enough?

If the goal is to go with solar heating only, this question should be directed to a local architect with substantial experience with solar heating systems. If the goal is to produce substantial savings using solar in conjunction with an existing system, a workable rule of thumb is to determine the "footprint" of the structure in square feet and divide it by four. Take the square root of this quotient and round up to the nearest whole number. This result is the number of two-foot wide solar panel sections needed to heat the structure during sunny winter days.

How long will it last?

If not abused, and if the exterior wooden surfaces are kept painted, our collectors should have a service life of at between fifteen and thirty years.

How do I control the temperature?

Vertically mounted solar panels naturally produce a maximum amount of heat at the winter solstice and a minimum amount of heat at the summer solstice as a result of the same axial tilt that produces winter and summer. If there isn't enough panel area to satisfy the heating requirement, then the conventional heating system is used to make up the difference. If the panels are producing too much heat, then the temperature can be lowered by allowing warm air to escape outdoors (by opening a window, for example.) During warm seasons, a cover or shutters can be used to block sunlight and prevent heat production.