Passive solar: Systems that convert sunlight into usable heat or provide cooling through architectural design and building materials that take advantage of natural energy flows. They are inexpensive to operate, perform quietly and have few, if any, moving parts. Examples include the basic greenhouse, as well as properly orienting the building, shading windows, using specialized windows and using dense materials in the floor, walls or roof that absorb and re-release heat into the home.
Active solar: Systems that use solar collectors and need electricity to power pumps or fans to distribute the sun’s energy. Many systems heat and circulate either liquid or air. Solar-powered water heaters are typically an active system, though there are also passive designs. The most commonly used photovoltaic systems on rooftops are considered active solar.
Thermal mass: A measurement of how well a material stores and releases heat energy. Used correctly, materials with high thermal mass can delay heat flow through a building by as much as 10 to 12 hours, producing a warmer house at night in winter, and a cooler house during the day in summer. Water has exceptional thermal mass properties for this application, but there are many others, including concrete and bricks.
- Dept. of Energy’s energy efficiency site
- California California Energy Commission’s solar site
Resources on green building and solar energy:
- Harold Hay’s site
- Magazine about home energy solutions
- American Solar Energy Society
- National Renewable Energy Laboratory
Web sites that explores passive solar energy
- UNLV’s Natural Energies Advanced Technologies Laboratory
- Sustainable Building Sourcebook
- Gary Reysa’s Build-It-Solar
- Australia’s guide to environmentally sustainable homes
Links to other examples and to the work of people quoted in the story: