Solar Education
When we talk about installing a renewable energy system to help power our homes, we are typically referring to one of three technologies: photovoltaics, hot water collectors, or wind turbines.
PHOTOVOLTAICS
Photovoltaic (PV) cells are made of special materials that are sensitive to sunlight. When light strikes the cell, a certain portion of it is absorbed. The energy of the absorbed light knocks electrons loose in the solar cell, allowing them to flow freely. This flow of electrons is a current, and by placing metal contacts on the top and bottom of the PV cell, we can draw that current off to use as electricity.
Individual solar cells produce very small amounts of power, so many of them are connected together in series to form a solar module. A solar module, or panel, is the basic unit that is installed on the roof. Many of these panels connected together make up a solar array. The array is the complete pv power generating unit.
The array generates direct current (DC) electricity. In a typical grid-tied system, this electricity is fed into an inverter. The job of the inverter is to convert this electricity from DC into high quality alternating current (AC) electricity. From here, the electricity flows into your electric service panel. If there are house loads that require power, the electricity flows there first. Any extra electricity will travel out of the service panel and back to the utility. As the electricity passes through your utility meter, it will turn it backwards. In essence, it is erasing energy that you have already used. This energy pass through arrangement is known as net metering. Depending on how much energy you consume, you may be able to install enough pv capacity to offset all of your electricity needs. How would you like to end up with a $0 electric bill each month?
HOT WATER COLLECTORS
Another way to harness the energy of the sun is to use the sun’s radiation to heat the water that is used in your home. This is accomplished with flat plate solar collectors which are installed on your roof. A heat transfer fluid is circulated to the roof where it adsorbs heat and then it returns to a heat exchanger in your hot water tank where it releases the heat into your water. One of our systems can offset up to 90% of your yearly hot water costs.
WIND TURBINES
Wind is also a form of solar energy. Winds are caused by the uneven atmospheric heating by the sun along with the earth’s surface irregularities and rotation. Wind energy is the fastest growing source of electricity in the world. While most of this stems from large wind farms, wind energy is still a practical small scale energy source.
A residential wind turbine is generally not suitable for urban or small-lot suburban homes due to their size and tower height. Except for very small wind turbines (i.e., with rotors one meter or less in diameter) on very small towers, a property size of one acre or more is desirable.
The economics of a wind system depend on the average wind speed in your area. As a general rule of thumb, you should have at least a 10 mph average wind speed for a wind turbine to be practical. One fact to know about wind speed is that the amount of wind energy available increases by the cube of the wind speed. Doubling the wind speed yields eight times the energy! Even a small difference in wind speed within a given area can have a big impact on the amount of energy a wind turbine can generate. It is also one of the reasons why a taller wind tower can make so much of a difference. If the wind speed increases even a few miles an hour by going with a taller tower the energy generation potential increases appreciably.