This section is a brief review of solar energy systems and concepts.
All the solar systems listed here are called active solar systems. They are called active solar systems because they require assistance to move the energy generated from the collectors. For example an solar water system requires the use of a pump to move the heat to the tank.
Passive solar uses the heat generated from the sun to warm up interior surfaces. There is no use of fans or blowers to move the heat. The passive solar gains during the day are absorbed for release at night as radient heat. Care must be taken in the design of passive solar structures to maintain proper orientation, shading and insulative values. Passive building construction and active solar systems are an excellent complement to each other.
Each general type of solar system is further detailed in the web pages for air, water or electric systems.
Controller: the component that automatically turns on the blower or pump when the heat in the collector is greater than the temperature inside the house or water tank. These can be a simple, one function unit or a more complex multi-function unit with temperature readouts. Requires a "sensor" outside on the collector and one inside the house.
Blower: usually a squirrel cage type (wheel) which pushes air through the insulated flexible duct to the solar air collector and back into the house.
Pump: the component that pushes water through the pipes to the solar water collector and back into the water heater or storage tank.
Solar Collector: is an ambiguous term - "collects energy from the sun" - generally divided by "thermal" or "electric." Solar thermal collectors will be either air or liquid. They are made of aluminum, hardened solar glass, and rigid insulation. They are usually 4' x 8' and weigh about 80-100 pounds. The air collectors are "hollow" and connected to ducts. The water collectors have a copper plate, painted black inside and are connected to water pipes.
Solar electric collectors (also called photovoltaic or PV) have silicon wafers inside with very tiny wires that collect the electricity. They are sized by watts and usually range from 25 - 125 watts. The smaller panels are about 2' square and the bigger panels are about 3' x 5'. They weigh about 5 - 30 pounds.
Solar Storage: generally refers to hot water systems where the heat from the collector is transferred to an insulated water tank for storage.
Heat Exchanger: used in hot water systems. A water-to-water heat exchanger has heated water from the solar pass by cooler water from the tank and they exchange energy. Water-to-air heat exchangers have heated water from the tank pass through a coil with air blowing over it.
Radiant floor heat: great idea, rarely seen in the Midwest, works fabulously well with solar hot water systems. Tubing is placed in the concrete floor and the water running through it is heated by solar. This technique produces a very even, steady heat with no drafts. The concrete mass becomes the distribution and "storage."
Solar System: is another ambiguous term - the components necessary to collect energy from the sun and transfer that energy to another media or area.
* Solar Air System includes a controller, collector, blower and ductwork.
* Solar Water System requires a controller, collector, pump, heat exchanger and pipes.
* Solar Electric System contains a controller (or inverter which flips solar DC to household AC), collector, battery charger, and batteries.
Insolation: The rate of delivery of solar radiation per unit of horizontal surface. Nebraska and Iowa average 3.5 to 4 vs. 5.5 to 6 for Arizona. The measurement is in kWh/m2/day.
Rule of Thumb for calculations - figure 1000 BTUs per square foot of collector. If you have a 4'x 8' collector, that is 32 square feet or 32,000 BTUs per square foot per day.