Use of solar energy on a small scale is happening on two fronts: solar thermal and solar electric. Traditional solar panels are solar electric; they generate electricity from the sun. Solar thermal panels are used to heat water or air which is in turn used as hot water or to heat spaces. These systems take advantage of the average 1400 Watts per square meter of solar energy that the Earth receives.
The major advantage of using thermal solar energy panels to heat water is that there are fewer energy conversions in the system. Each conversion of energy from thermal to electric and back to thermal creates a loss. If a solar electric system were used to heat water for home use, losses can be very high. But utilizing the thermal energy from the sun to directly heat water means that there are fewer losses and higher efficiency. This means that less water needs to be heated by the solar energy panel.
For all other uses, solar electric energy panels are the most useful. The energy that they generate can be stored in a battery bank and used later when it is needed. This is especially useful because the amount of power that a solar panel can generate during the day is relatively constant, however at night there is no power generated. Storing this energy means that solar energy panels can be used to power your home even when the sun isn’t shining.
All solar energy panels are most efficient when they are pointed directly at the sun. Most panels are fixed to a roof or other portion of the structure which means that the sun strikes them at different angles throughout the day. When space permits, mounting the panels on a freestanding structure with a sun tracker is the most efficient; however even this doesn’t guarantee that the panels will provide full rated power all day. The amount of energy that reaches the surface of the Earth from the Sun is greatly affected by the amount of atmosphere between the sun and the point on the surface.
When the Sun is low in the sky, there is significantly more atmosphere between the Sun and your solar energy panel. This means that the amount of energy generated will be lower than full rated power all day. This doesn’t mean that they aren’t useful, but it must be taken into account when planning any renewable energy system. Since most renewable energy systems utilizing solar energy panels will have some degree of intermittent power generation, a method to store this energy is required.Solar electric panels will have their energy stored in a battery bank, and solar thermal panels will most likely still require a hot water holding tank of some sort. An electric or gas element may still be required to maintain temperature in the tank, but this will require much less energy than heating up cool water. This is the major benefit found when using solar thermal panels; reduction in electricity use is a major concern in any renewable energy system.