I have built and used a totally portable solar heater while camping, household use, emergencies, and businesses.
The idea is quite simple and proven. A dark surface, when exposed to sunlight, quickly heats up, which heats up any surrounding fluid, in this case air. The air is let in at the bottom of the panel and allowed to rise up using convection by the heating air mass rising up and out the top opening. A fan can be used to direct the air to distant parts of a structure or tent.
The Solar Heater can actually be built right into a structure as part of the structure itself. Part of a wall or roof can be built to be or accept this phenomenal Heater.
The best way to make this unit is an insulated box with the interior painted black. Baffles or other air turbulators are employed to transfer as much heat from the black material, (Usually metal but can be concrete, heat and UV resistant plastic or any other hardy material capable of withstanding several hundred degrees), to the air as possible. Over all this is a glazing, such as glass or plexiglass, that transmits as much infrared radiation as possible through to the 'heat collectors', but acts to insulate the air inside the heater from the cold outside air.
Usually passive airflow will work, but often much more capacity can be realized with a small battery operated fan for the portable unit, to a powerful furnace type blower, for the large units. A passive fin type heat exchanger can be used to minimize dust being introduced into the heater. Small photovoltaic solar cells can be used to provide the electric fan power.
Essentially there are no moving parts of the heater itself. Nothing to break down or wear out. Heater can be made to virtually last for a life time.
Some of these units I have built are completely disposable, using weather resistant cardboard, blackened aluminum foil, and plastic film similar to dry cleaner cover.
This heater can be used in shelters where there is lots of sun, and cold temperatures, common in many parts of the country. A standard heater can be stationed for back up.
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