Renewable Energy : Solar Power


Solar means 'sun' in Latin. Solar energy technologies use the sun's energy and light to provide heat, light, hot water, electricity, and even cooling, for homes, businesses, and industry.

Solar Electricity

The photovoltaic (PV) effect is the process of converting light (photons) to electricity (voltage).
Photovoltaic Systems produce electricity directly from sunlight.

Solar panels, or PV panels are flat-plate panels that contain individual photovoltaic (PV) cells. A collection of panels can provide enough power for a single household; a large arrangement of panels, or a solar array, can power large industrial sites; and hundreds of arrays can be interconnected to form a large utility-scale PV System. These panels can be mounted at a fixed angle facing south, or can be installed with a tracking device that follows the sun, allowing them to capture the most sunlight over the course of a day.

Solar panels used to power homes and businesses usually hold about 40 solar cells. A typical home will use about 10 to 20 solar panels mounted at fixed angles facing south to power the home.

With green in vogue, solar panels have become the perfect photo-op. But when considering solar PV panels for historic homes, we must proceed with caution! While we may not be able to put solar panels on the William Aiken House, what about the many historic homes and buildings downtown? articulates more clearly where the line is between acceptable and unacceptable green improvements.

Rough rule of thumb for the continental US = South facing system. Panels must be facing SOUTH, tilted to face the sun, and never shaded. If sited inaccurately, perfectly good (and expensive) PV panels do not produce nearly as much electricity, as they would at the correct solar angle.

Solar Hot Water

Water used for buildings and for swimming pools can also be heated with the sun's energy. Consider natural solar heating. Shallow water in the ocean tends to be warmer than deep water because sunlight can reach the ocean bottom, which in turn, heats the water.

This principle is also used to provide water heating for buildings and swimming pools. Solar hot water heating systems require two main components: a solar collector and a storage tank. This is extremely simple in swimming pool systems. The pool of course serves as the storage tank, full of water. The solar collector is usually made of black plastic or rubber, and the pool's filter pump simply pumps the pool's water through this solar collector, heating it up!

Solar hot water for buildings requires flat-plate rectangular boxes mounted roofs to serve as solar collectors. These boxes look similar to solar panels for electricity. However, the solar hot water collectors are filled with coils of fluid, usually water or a water and glycol mix. The panels are set on planks and as the sun heats up the panels, it also heats the water/glycol mix. Next, the mix must work its way through the system. These systems can be either active or passive. Passive systems are less common and rely on gravity to transfer the fluid mix to the storage tank. Active systems have pumps to move the liquid from the collector panels to the storage tank. Regardless, this mix works its way through the system and returns to the storage tank. In domestic solar hot water systems, this tank is usually located in the basement.

Systems that only use water in their coils are pretty simple. When fluids other than just water are used, the water must be heated by passing it through coils of tubing in the tank,which is full of the hot water-glycol mix. Regardless of the system type, the storage tank must be well-insulated to ensure its efficiency.