The simplest and easiest way for humans to directly harness energy from the sun is by using light to produce heat. This process is referred to as solar thermal.

1. Thermoregulation
   Cold blooded animals like lizards and snakes keep themselves warm with solar thermal energy. They lie out on rocks during the day to absorb heat from the sun.
   
   
2. Solar Thermal Collectors
   Solar hot water heaters can be used to heat water with the sun. These are one of the most efficient uses of solar energy. Black tubing in a black insulated box with a glass top traps sunlight, allowing water to heat up even during the winter. A solar oven is another type of collector which can be used to cook food.
   
   
3. Orientation
   By orienting a house in an east/west direction, the sun can be let in when it’s cold and kept out when it’s hot. During the summer the sun is high in the sky. At this time of year overhangs above windows can prevent the sun from heating a house. During the winter the sun is low in the sky. This allows sunlight to go under the overhangs, entering the house and warming the interior.
   
   
4. Windows
   A passive solar home will have most of its windows on the south side of the house. This allows the sun to heat the house in the winter, but not in the summer. Double pane window glass helps to keep heat inside in winter, and out in the summer.
   
   
5. Insulation
   A well insulated home is essential to passive design. It reduces the amount of heating and cooling a home requires. Insulation can be in the form of fiberglass, foam, straw bales, adobe and other types of thick walls.
   
   
6. Thermal Mass
   A passive home must be able to store heat in the winter and keep cool in the summer. Thermal mass, like bricks, concrete, water and other heavy objects can keep a home warm at night by storing the energy they gain from sunlight during the day. In the summer they can keep a home from getting too hot if they are cooled at night.
   
   
7. Shading
   Trees on the west side of the house can provide shade in the summer afternoon, reducing the need for cooling.
   
   
8. Ventilation
   Proper ventilation can help cool a home in the summer. However, a home should also be airtight so that it can hold warmth in the winter.

solar energy | chemical energy | photovoltaics | solar thermal
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