Solar Home Lighting Systems
SHS systems are small low cost 12-volt lighting
systems for remote villages in developing countries. Utility grid extensions to service the millions of people in remote villages is unlikely, and they often get their room lighting from dangerous and poorly
illuminating kerosene lamps. Government subsidies and microfinancing are often used to help make these simple solar systems affordable. A typical SHS package consists of a single 50-100 watt solar module, a small charge
controller and locally available battery, and a 7-15 watt fluorescent lamp assembly. Small appliances like TV, radio, or ceiling fan can be added as budgets allow.
Remote Home and Clinic Power Systems
are stand alone DC power systems with multiple solar modules in 12- or 24-volt configurations, charge controller, and a battery bank of deep cycling batteries. The array supplies all the energy needed for a wide variety
of loads, including TV/VCR, radio, ceiling fans, small appliances and tools. Systems can easily expand as budget or load demand increases.
AC/Hybrid Power Systems
When load demand is larger than just a few
light (perhaps at 3 kWh/day or greater), AC loads are more economical, and a DC-AC inverter is included in the system. If load demand is great enough, it often is economical to also include a generator and rectifier in
the system, to allow full operation during severe bad weather and to insure that the battery bank can be fully charged at any time during the year. Ranches and farms, small villages, and large off-grid residential homes
can use such hybrid systems to provide 100% of the power needed, anytime, anywhere.
Grid Connected Systems
In urban centers with well established utility grid
systems, reliable electric power can still be a problem. There may be intermittent grid brown-outs or shortages that are very disruptive to business, food storage and security. Grid connected pv systems can be designed
to operate with batteries in a UPS (uninterruptable power supply) type mode, so that in case of prolonged utility outage, the pv modules and batteries operate all the AC loads.
If the urban utility grid is highly
reliable, then grid connected pv systems can be designed to simply work with the grid, producing utility quality AC power that is either consumed by the home or sent on to the grid, giving credit to the home owner to be
applied against the power they consume at night. Such grid interactive systems can reduce daytime demand for utility power, and operate to their maximum exactly when urban grid power is most in demand (for example
during hot summer days when air conditioning is increases). Distributed grid connected systems help reduce greenhouse gasses by directly displacing centrally generated power from coal-fire power plants.