Helios Electric Solar Energy Basics - The World's Leading Renewable Energy Installer

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Photovoltaic's / Solar Electric Systems: Photo is Greek for Light and Voltaic is after Allesandro Volta pioneer in the study of electricity. Thus photovoltaic means *light to electricity*. The photovoltaic's (PV) convert sunlight directly to direct current (DC) electricity by use of a semiconductor.

Solar cells are made from a chemical element called silicon. Silicon is one of the most common substances on Earth and can be found in most semiconductors/integrated circuits today.

A semiconductor p-n junction produces an electric field that is maintained purely by virtue of the material. In other words, no external voltage need be applied. For a solar cell, this means that when light hits the cell, electrons are bumped from atoms and drawn to one side of the junction by the internal electric field producing a current. When current flows you have electricity.

Silicon PV comes in many varieties. Shell PV panels are made with single-crystal silicon. These cells are cut from a single crystal of silicon. Single crystals give the highest efficiency of conversion of light to electricity at 15 to 17%. Solarex panels are made of polycrystalline silicon. Astropower PV panels are made of microcrystalline silicon. A very different type of cell is made of amorphous silicon, that is completely non-crystalline. Efficiencies of these cells are about 6%, much lower than crystalline. The beauty of amorphous silicon is the thin film material which can be made into an ultra thin backing. It can be made into flexible products such as Unisolar PV shingles and PV Laminates.

There is one other type of PV material which is common in the aerospace industry called gallium arsenide. These cells can be 30% efficient and are resistant to radiation damage. They are still very expensive and used only on spacecraft.

Because the solar cell is a solid state device, it can last for decades. The only part of a panel which can degrade is the material which encapsulates the cells. Some of these materials will brown if subjected to multiplied sunlight such as a magnifying glass or after many decades of regular exposure. Solar panels are not fragile. They are subjected to hail tests with 1 inch hail stones at a speed of 50mph.

All indications are that solar panels installed today, will still be working perfectly in 30 years. Most panels have a 25 year warranty from the manufacturer. Some PV manufacturers include GE, Sharp, BP, Atlantis, Shell, Kyocera and Unisolar.

Solar Thermal Systems: Not too be confused with solar hybrid lighting and solar electric systems. Solar thermal is a technology for harnessing solar energy for heat. Solar thermal systems are generally used to heat swimming pools and create hot water for residential and commercial use.

Solar Hybrid Lighting: Also known as passive solar lighting. The use of natural illumination from the sun instead of artificial lighting from conventional light bulbs. Solar hybrid lighting can reduce energy bills by collecting light from the roof of a commercial building and directing the light into the building using fiber optic cabling. It provides a healthy alternative to lighting commercial buildings while significantly reducing energy bills.

Wind Turbines: A wind turbine is a machine that converts the kinetic energy in wind into mechanical energy. Mechanical energy is then converted into electricity. Electric generating devices using wind are known as wind generators, wind turbines, wind energy converter (WEC), horizontal axis wind turbines, and vertical axis wind turbines.

Hydroelectric Turbines: Electricity produced by the flow of water and is used in many of our projects. It is used in both commercial and residential applications to significantly lower electricity bills.

Fuel Cells: A fuel cell is an electrochemical energy conversion device. It produces electricity from external supplies of fuel. Their are several fuels available to power fuel cells. These fuels react in the presence of an electrolyte. Generally, the reactants flow in and reaction products flow out while the electrolyte remains in the cell. Fuel cells can operate continuously with very little maintenance as long as the necessary fuel flows are maintained. They provide power much like a small Honda portable gas generator but operate with zero to minimal emissions and without any noise.

Net Metering: A method of crediting customers for electricity that they generate on site in excess of their own electricity consumption. When connecting to grid power, customers with their own renewable generation offset the electricity they would have purchased from their utility. If such customers generate more than they use in a billing period, their electric meter turns backwards to indicate their net excess generation. With solar, excess electricity generated by PV systems flows back into the power lines for use elsewhere and the PV system owner is credited for the excess at retail prices.

Inverters: An inverter is an electronic device which takes the direct current from the solar cells and changes it to alternating current (AC). Most households run on AC because AC wiring is cheaper and safer than DC wiring. Inverters are made to convert from 12, 24, 48, 225, or 400 volts DC to 120 or 240 AC. The AC output of inverters is either a modified sine wave or true sine wave. Inverters for net metering systems have to meet IEE-929-2000 standards and be UL listed.

Power Factor Correction: Power factor correction is the process of adjusting the characteristics of electrical loads to increase power factor without altering the voltage or current. This is usually achieved by adding a reactive element in parallel with the load in order to increase unity. Power factor correction may be applied to electrical power transmission lines to improve the stability and efficiency of the transmission network or may be installed by individual electrical customers to reduce energy costs. In theory high power factor is generally desirable which can improve voltage regulation. Currently most commercial and residential power factor devices do not reduce energy usage by much if any at all and many will actually use energy in the process. Until these devices are field tested you are better off purchasing new appliances before investing in a power factor correction device.

Batteries: Stand-alone solar electric systems use lead acid batteries to store power for cloudy weather or for night time use. Lead acid batteries can be made to withstand deep-cycling, this means discharging them to near-empty. They do not have any memory like NiCd's do. If charged and maintained properly, good lead acid batteries will last for years. Large deep cycle batteries can last 10 to 15 years.

Charge controllers: A charge controller is a solid state electronic device which measures the charge state of the batteries and turns the current from the PV cells on if the batteries need charging or off if they do not. This device protects the batteries from over-charging which can shorten their life.

Wiring: Since solar electric and wind power systems are DC they have wiring requirements different from AC systems you see in your home. All disconnects and fuses have to be rated for DC and large wires are often needed to avoid voltage losses if panels are far from the controllers. Combining DC and AC wiring needs to be done by qualified electricians or electrical engineers and must meet all NEC electrical requirements.