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Solar is universal and will work virtually anywhere, however some locations are better than others. Irradiance is a measure of the sun’s power available at the surface of the earth and it peaks at about 1000 watts per square meter. With
typical crystalline solar cell efficiencies around 14-16%, that means we can expect to generate about 140-160W per square meter of solar cells placed in full sun. Insolation is a measure of the available energy from the sun and is expressed in terms of “full sun hours” (i.e. 4 full sun hours = 4 hours of sunlight at an irradiance level of 1000 watts per square meter). Obviously different parts of the world receive more sunlight than others, so they will have more “full sun hours” per day.
There are many components that make up a complete solar system, but the 4 main items on a stand-alone system are: solar modules, charge controller(s), battery(s) and inverter(s). The solar modules are physically mounted on a mount structure and the DC power they produce is wired through a charge controller before it goes on to the battery bank where it is stored. For more detailed information on solar modules, turn to page 20. The two main functions of a charge controller are to prevent the battery from being overcharged and eliminate any reverse current flow from the batteries back to the solar modules at night. The battery bank stores the energy produced by the solar array during the day for use at anytime of the day or night. Batteries come in many sizes and grades, which you can see starting on page 49. The inverter takes the DC energy stored in the battery bank and inverts it to 120 or 240 VAC to run your AC appliances.
No. Photovoltaics converts the sun’s energy into DC electricity at a relatively low efficiency level (14-16%), so trying to operate a high power electric heating element from PV would be very inefficient and expensive. Solar thermal (or passive solar) is the direct heating of air or water from the heat of the sun and is much more efficient for heating applications than photovoltaics.
Maybe. Many older homes were not designed or built with energy efficiency in mind. When you purchase and install a renewable energy system for your home, you become your own power company, so every kWh of energy you use means more equipment (and hence more money) is required to meet your energy needs. Any appliance that operates at 240 VAC (such as electric water heaters, cookstoves, furnaces and air conditioners) are expensive loads to run on solar. You should consider using alternatives such as LP or natural gas for water/space heating or cooking, evaporative cooling instead of compressor based AC units and passive solar design in your new home construction if possible. Refrigeration and lighting are typically the largest 120 VAC energy consumers in a home (after electric heating loads) and these two areas should be looked at very carefully in terms of getting the most energy efficient units available. Great strides have been made in the past 5 years towards improving the efficiency of electric refrigerators/freezers. Compact fluorescent lights use a quarter to a third of the power of an incandescent light for the same lumen output and they last ten times longer. These fluorescent lights are now readily available at your local hardware or discount store. The rule of thumb in the renewable energy industry is that for every dollar you spend replacing your inefficient appliances, you will save three dollars in the cost of a renewable energy system to run them. So you can see that energy conservation is crucial and can really pay off when considering a renewable energy system.
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