Passive solar energy can be used to heat and cool buildings, and provide light. Passive solar technologies can often be built into new buildings without significantly adding to the constructions costs and saving up to 40% in energy savings. Designing and building with passive solar in mind is the least expensive and most environmentally friendly ways of providing our energy needs.
Every year, there is a great amount of solar energy that reaches earth. Most of this energy is reflected back out into space by clouds and lost. Ninety-nine percent which reaches the ground is turned into heat and radiated back out into space, the other 1% is used by plants for photosynthesis. If we could capture only a small amount of this energy, we could meet the worlds energy demands. Even in Canada, with it's cold climates, the amount of good solar energy that reaches the ground in winter is much more then the daily heating requirements of a house.
Passive solar technologies has almost no effect on the environment. It gives off no toxic air or water emissions and does not add to the environmental problems that plague us today, such as global warming and acid rain. The sun is an inexhaustible source of energy and in renewable and will never become depleted.
"There's nothing new under the sun", is true for passive solar techniques. Mankind has been using the suns energy for thousands of years. Rediscovering this inexpensive and abundant energy source could go long way towards a more sustainable future.
Most buildings have limited passive solar heating. Sunlight passing through windows is a source of heat; but real passive solar is achieved by specifically designing buildings to use solar energy. Proper building insulation enhances the use of passive solar energy, since a well insulated building needs less energy to heat and therefore it's heating needs can be easily met by passive solar techniques.
Direct solar gain, increased thermal mass, and attached sun spaces are the most common features of passive solar power. Direct solar gain captures the sun's energy from large areas of south facing windows. When sunlight enters the windows it is converted into heat which isn't transmitted back out the window and this results in a heat gain inside the house. Glass is not a good heat insulator however, so any heat gain during the day can be offset by heat loss at night. This can be reduced by using triple glazed windows with various special coatings that have a high insulation value, and placing shutters over the windows at night.
Sun spaces are glassed enclosures attached to the outside of a building. (Figure 1). These spaces act like greenhouses, trapping the heat during the day and some of this heat is transferred to the inside of the building or stored for release at night.
Direct solar gain and heat from thermal storage can be distributed though a building by mechanical ventilation or natural air currents. Hot air rises and cold air sinks. Using this fact, passive solar heat can be distributed in a building.(Figure 2)
Day lighting is a way of using sunlight to replace electric lighting in a building. As of yet there is no way to store sunlight and release it at a later time. Dilating is most valuable in office buildings where most of the lighting is only needed during the day. Windows can supply lighting for the perimeter of the building and light-pipes, and light-shelves, can transport light into the inside of the buildings. This in combination with photo-sensor controls that can adjust electric lights according to sunlight levels, can reduce the amount of electricity needed to light up a building.
There are two common methods of passive cooling, vegetation and natural ventilation. Painting buildings a light color is another obvious form of passive cooling.
Deciduous trees planted around a building can cool a building down by shading it. Vines and ivy growing on the walls serve the same purpose. Tree planting within cities also reduces the "urban heat island" effect, caused by the sunlight hitting the roofs and paved areas of the city, raising the temperature. Another advantage to using deciduous trees is that when they lose their leaves in winter, they allow passive solar heating by letting the sun's rays hit the building.
For a properly designed building, passive solar heating can supply a large amount of it's energy needs. The best time to for using passive solar in in new constructions, since the re-fitting of a building with this technology is fairly expensive. Though often seen as "low technology", the advances of todays science has made passive solar technology a inexpensive, practical, alternative energy source.
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