Active Solar depends on movement from a collector to the area that the heat will be used. Sometimes the heat is used for water heating and other times it is used for space heating.
There are two basic types of active heat collection: Air and Liquid.
Hot water heating is a good example of an Active Liquid Heating System.
A collector is placed on the roof of the building and a insulated hot water storage tank is located within the building. Storage tanks are similar to a regular hot water heater tank of either electric or gas design but in addition to the heating elements found in a normal hot water heater a heat transfer coil will allow the collected hot water from the roof top collector to warm the water in the storage tank.
To get the heat transfer liquid usually a glycol or antifreeze type liquid to circulate from the storage unit to the collector a pump is used. The pump is controlled by a thermostat that reads the temperature of the transfer fluid, the fluid in the storage tank and the temperature of the fluid in the collector.
Because the movement of water in the collector is relatively fast the temperature of the liquid that runs through the collector only rises about 20F. Over time the temperature in the storage unit will rise to a set temperature of about 140F to 160F as the transfer liquid continues to circulate through the collector.
If the heat in the storage tank reaches optimal temperature then the pump will stop.
If the outside temperature falls below a point where collection from the roof top grid collector is not sufficient then the pump will stop.
When the outside temperature is too low to collect heat the transfer liquid will drain back into a reservoir tank inside the house to eliminate the possibility of cracking or bursting pipes in the collector.
When the collector is not serving the home for hot water then the hot-water heater will work in standard mode and use gas or electricity to heat the water for the home.
Solar collection of heat from liquid transfer is not only for drinking water but it can also be used to feed heat into baseboard heaters or it can be passed over an evaporator type device and used for HVAC forced hot air heating.
Hot-water baseboards and radiators require water between 160° and 180°F (71° and 82°C) to effectively heat a room. And for this reason a dual system will probably be required to separate the Hot Drinking Water which should be about 140F from the House Heater or scalding can occur. Another option may be installing Point Of Use faucets that let you mix hot and cold water within the faucet and show you the accurate temperature so scalding won’t occur.
Specific Designs of the system you will use will need to be developed for your application. This may also require additional reinforcement in your attic rafters or truss system to support the additional weight of the collectors.
Active Solar Air Systems
Some homes may use passive and active air heat collection to provide space heating for the home. Some systems are designed by including a black surface collector on a outside wall and when the sun heats the surface the temperature rises. To store the heat a heat sync or pad is installed in the basement of the home.
To move the heat from the collected area to the storage area fans and duct work are used.
Another simple method of active heat use is when a ceiling fan in a great room or in a area with high ceilings is reversed to force the warm are in the home back down into the living area.
Although Active Air Systems may seem to be limited at first glance, you can easily increase the temperature of the home up-to 40 degrees even in winter.
This is why it is so important to make use of your homes natural collection of heat by just keeping South / Southwest window shades open during the day. Even on the coldest winter days with proper wall insulation a home may get to 70-75F while the sun is out alleviating all need for supplemental heat during the day and into the early evening hours.