Just as solar thermal greenhouses are a way to apply solar thermal technologies to an everyday need, solar thermal chimneys, or thermal chimneys, also capitalize on thermal mass materials. Thermal chimneys are passive solar ventilation systems, which means they are nonmechanical. Examples of mechanical ventilation include whole-house ventilation that uses fans and ducts to exhaust stale air and supply fresh air. Through convective cooling principles, thermal chimneys allow cool air in while pushing hot air from the inside out. Designed based on the fact that hot air rises, they reduce unwanted heat during the day and exchange interior (warm) air for exterior (cool) air.
Thermal chimneys are typically made of a black, hollow thermal mass with an opening at the top for hot air to exhaust. Inlet openings are smaller than exhaust outlets and are placed at low to medium height in a room. When hot air rises, it escapes through the exterior exhaust outlet, either to the outside or into an open stairwell or atria. As this happens, an updraft pulls cool air in through the inlets.
In the face of global warming, rising fuel costs and an ever-growing demand for energy, energy needs are expected to increase by nearly the equivalent of 335 million barrels of oil per day, mostly for electricity [source: Meisen]. Whether big or small, on or off the grid, one of the great things about solar thermal power is that it exists right now, no waiting. By concentrating solar energy with reflective materials and converting it into electricity, modern solar thermal power plants, if adopted today as an indispensable part of energy generation, may be capable of sourcing electricity to more than 100 million people in the next 20 years [source: Brakmann]. All from one big renewable resource: the sun.