Active Passive

Reader Contribution by Staff
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If wind-power is a no-brainer, what about passive solar power? It’s ubiquitous, clean, renewable and free. Our homes could cut their heating requirements dramatically simply by capturing the solar energy that lands on the house naturally. Imagine if all new homes had a row of tall, insulated windows on their solar exposure (the south side, if the home is north of the equator). Then, we add a heat-absorbing concrete floor in the room with the windows. All day long the sunlight warms the house and heats up the concrete. At night the concrete radiates warmth.

The basics of passive solar architecture are simple.[1] First, the building needs what the engineers call an “aperture” through which the sun can shine – in other words, a window. If the sun shines into a window in your home or office, then you have a passive solar collector.

Second, if you want to store some of that solar energy you need an “absorber,” some “thermal mass” that can be heated by the sun. Dense substances like stone, concrete or adobe are very good for storing thermal energy. Sometimes a water tank is used to store thermal energy with the added benefit of being able to distribute the warmth in pipes. Less dense materials – like wood or carpet – can’t effectively store heat.

Third, for a building to be effectively warmed by passive solar energy there needs to be some way of distributing the warmth through the house. In an Earthship, nearly every room has its own solar aperture and thermal mass, so there’s no distribution problem. In more complex structures, fans, ducts and blowers may be used to circulate warm air.

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