Design

• A passive solar panel is a box designed to absorb light and retain heat. They can be made in any size but the most common dimension is 2 feet by 2 feet.
  
  Paint one side of the box black or cover it with a dark material so that light is absorbed. Angle the box to the sun. The most effective angle is determined by the latitude of the box's location, the time of year and access to southern light if in the Northern Hemisphere.
  
  Line or coat the back of the box with a reflective material so that any light or heat reaching the back of the box is reflected back to the box's interior. This retains heat and light, maximizing the panel's efficiency.
  
  The interior of the panel is where the action is, where the energy of the sun's light is held as heat. Some passive solar panels feature coiled copper, others hoses full of circulating water, and other panels are empty except the air being heated within the box. The purpose of these materials is the same, to circulate the heat within the panel to the outside where it can be used to heat water or air, and eventually, us.
  
  Heat moves from a warmer area to a cooler area. This natural movement is used when planning and designing solar heating systems. Keep this law of thermodynamics in mind when placing your solar panel in a specific location.
  
  

Use

• Passive solar panels do not collect enough high intensity, high concentrated sunlight to generate electricity but they are capable of heating water. Water heated by the sun can be used for a variety of purposes, one of which is storage. Hot water radiates heat and can be used to heat a room.
  
  You can place the solar panels at the bottoms of open windows. The sun heats the air inside the panel. Hot air rises back into the cold room. Cold air is naturally pushed into the panel, heated by the sun and circulates back into the room as warm air. When the sun goes down the system automatically shuts off as there is no longer any heat driving the circulation.