Solar design in architecture Solar design can be used to achieve comfortable temperature and light levels with little or no additional energy. This can be through passive solar, where maximising the entrance of sunlight in cold conditions and reducing it in hot weather; and active solar, using additional devices such as pumps and fans to direct warm and cool air or fluid. Solar heating systems Solar hot water systems use sunlight to heat water. These systems may be used to heat domestic hot water or for space heating but are most commonly used to heat pools. These systems are basically composed of solar thermal collectors and a storage tank. The three basic classifications of solar water heaters are: Active systems which use pumps to circulate water or a heat transfer fluid. Passive systems which circulate water or a heat transfer fluid by natural circulation. These are also called thermosiphon systems. Batch systems using a tank directly heated by sunlight. A Trombe wall is a thermal mass that is heated by sunlight during the day and radiates stored heat during the evening. Solar cookingr Pictured: Solar CookerA solar box cooker traps the Sun's power in an insulated box; such boxes have been successfully used for cooking, pasteurization and fruit canning. Solar cooking is helping many developing countries, both reducing the demands for local firewood and maintaining a cleaner environment for the cooks. The first known western solar oven is attributed to Horace de Saussure. Photovoltaics The solar panels (photovoltaic arrays) on this small yacht at sea can charge the 12 V batteries at up to 9 Amps in full, direct sunlightSolar cells, also referred to as photovoltaic cells, are devices or banks of devices that use the photovoltaic effect of semiconductors to generate electricity directly from sunlight. Until recently, their use has been limited due to high manufacturing costs. One cost effective use has been in very low-power devices such as calculators with LCDs. Another use has been in remote applications such as roadside emergency telephones, remote sensing, cathodic protection of pipe lines, and limited "off grid" home power applications. A third use has been in powering orbiting satellites and other spacecraft. Total peak power of installed PV is around 5,300 MW as of the end of 2005. This is only one part of solar-generated electric power. For solar reflector plants see below.Declining manufacturing costs (dropping at 3 to 5% a year in recent years) are expanding the range of cost-effective uses. The average lowest retail cost of a large photovoltaic array declined from $7.50 to $4 per watt between 1990 and 2005. With many jurisdictions now giving tax and rebate incentives, solar electric power can now pay for itself in five to ten years in many places. "Grid-connected" systems - that is, systems with no battery that connect to the utility grid through a special inverter - now make up the largest part of the market. In 2004 the worldwide production of solar cells increased by 60%. 2005 is expected to see large growth again, but shortages of refined silicon have been hampering production worldwide since late 2004. Solar fibers A photovoltaic device not using silicon is currently in development. The device consists of a "solar tape," containing titanium dioxide (TiO2) in the form of a tape or fiber that could be combined with clothing or building materials. The material has inferior efficiency to conventional photovoltaics (5% for an initial commercial version to "near 12%" in the lab as of 2004, versus 15-30% for conventional cells). Its advantages are its low manufacturing cost, low weight, flexibility, function in artificial light, and resulting versatility.
