Solar architecture is designing buildings to use the sun's heat and light to maximum advantage and minimum disadvantage, and especially refers to harnessing solar power. It is related to the fields of optics, thermics, electronics and materials science. Both active and passive strategies are involved. The use of flexible thin-film photovoltaic modules provides fluid integration with steel roofing profiles, enhancing the building's design. Orienting a building to the sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air also constitute solar architecture. Improvements in solar architecture have been limited by the rigidity and weight of standard solar power panels. The continued development of photovoltaic (PV) thin film solar has provided a lightweight yet robust vehicle to harness solar energy to reduce a building's impact on the environment.
History The idea of passive solar building design first appeared in Greece around the fifth century BC. Up until that time, the Greeks' main source of fuel had been charcoal, but due to a major shortage of wood to burn they were forced to find a new way of heating their dwellings. With necessity as their motivation, the Greeks revolutionized the design of their cities. They began using building materials that absorbed solar energy, mostly stone, and started orienting the buildings so that they faced south. These revolutions, coupled with overhangs that kept out the hot summer sun, created structures which required very little heating and cooling. Socrates wrote, "In houses that look toward the south, the sun penetrates the portico in winter, while in summer the path of the sun is right over our heads and above the roof so that there is shade." From this point on, most civilizations have oriented their structures to provide shade in the summer and heating in the winter. The Romans improved on the Greeks' design by covering the southern-facing windows with different types of transparent materials. Another simpler example of early solar architecture is the cave dwellings in the southwestern regions of North America. Much like the Greek and Roman buildings, the cliffs in which the indigenous people of this region built their homes were oriented towards the south with an overhang to shade them from the midday sun during the summer months and capture as much of the solar energy during the winter as possible. Active solar architecture involves the moving of heat and/or coolness between a temporary heat storage medium and a building, typically in response to a thermostat's call for heat or coolness within the building. While this principle sounds useful in theory, significant engineering problems have thwarted almost all active solar architecture in practice. The most common form of active solar architecture, rock bed storage with air as a heat transfer medium, usually grew toxic mold in the rock bed which was blown into houses, along with dust and radon in some cases. A more complex and modern incarnation of solar architecture was introduced in 1954 with the invention of the photovoltaic cell by Bell Labs. Early cells were extremely inefficient and therefore not widely used, but throughout the years government and private research has improved the efficiency to a point where it is now a viable source of energy. Universities were some of the first buildings to embrace the idea of solar energy. In 1973, the University of Delaware built Solar One, which was one of the world's first solar-powered houses. As photovoltaic technologies keep advancing, solar architecture becomes easier to accomplish. In 1998 Guha Subhendu developed photovoltaic shingles, and recently a company called Oxford Photovoltaics has developed perovskite solar cells that are thin enough to incorporate into windows. Although the windows are not scaled to a size that can be taken advantage of on a commercial level yet, the company believes that the outlook is promising.
Elements
Greenhouse
A greenhouse keeps heat from the Sun. In a double glazed greenhouse, three effects occur: no convection (air blocking), ray keeping (the ground absorbs a photon, emits it with lower infrared energy, and the glass reflects this infrared to the ground), and little conduction (double glazing). It seems that the convection effect is the most important, as greenhouses in poor countries are made of plastic. The greenhouse can be used to grow plants in the winter, to grow tropical plants, as a terrarium for reptiles or insects, or simply for air comfort. It must be ventilated, but not too much, otherwise the convection will make the inside colder, losing the desired effect. The greenhouse may be combined with heat storage or an opaque mask.
Photothermic module
Photothermic modules convert solar light into heat. They easily heat domestic water to 80 °C (353 K). They are put facing the sunny cardinal point, rather pointing towards the horizon to avoid overheating in summer, and take more calories in the winter. In a 45° North place, the module should face the south and the angle to the horizontal should be about 70°. The use of intermediate solar heat systems like evacuated tubes, compound parabolic, and parabolic trough, is discussed as they correspond to specific, intermediate needs. A customer who wants a cheap system will prefer the photothermic, giving 80 °C (353 K) hot water with 70–85% efficiency. A customer who wants high temperatures will prefer the solar parabola, giving 200 °C (573 K) with 70–85% efficiency. Do it yourself photothermic modules are cheaper and can use a spiral pipe, with hot water coming from the center of the module. Other geometries exist, like serpentine or quadrangular. If on a flat roof, a mirror can be placed in front of the photothermic module to give it more sunlight. The photothermic module has become popular in Mediterranean countries, with Greece and Spain counting with 30–40% of homes equipped with this system, and becoming part of the landscape.
Photovoltaic module
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