Solar energy produced is a function of how many photons from the sun strike your solar cell, and how many of these photons actually get an electron moving to create a current. The number of photons, or amount of sunshine, that strikes your solar cell needs to be determined to see how many cells or solar panels you will need for your solar energy system. This free solar energy will vary considerably depending on your latitude, the time of year, and cloud cover that your region can expect.
How do we Measure Solar Energy?
Free Solar energy is a combination of the hours of sunlight and the strength of the sunlight you can expect at your site. This combination is expressed as insolation and is expressed as an average irradiance measured in kilowatt hours per square meter per day. By definition, solar irradiance of 1,000 watts per square meter is what is expected for noon in the middle of summer when the sun is highest. Normally solar irradiance is measured in the number of kilowatts per square meter per day so if it were possible for the sun to be up for 8 hours and always at the highest strength, solar irradiance would be 8.0.
Solar irradiance will vary significantly during the year particularly in northern latitudes. As an example, the irradiance for New York City is 6.0 in June and only 1.7 in December yielding a average for the year of 4.0. This means that solar energy in December is 70% less than in June. Compare this to Phoenix where the irradiance is 7.8 in June and 3.0 in December or 5.5 for the year. If you are not tied to the grid, this means your capacity has to be over 2.3 to 3 times the size that would be dictated by June numbers. Values for your location are easily available on the internet since NASA's weather satellites have been compiling this information around the world for many years.
How Do We Use Irradiance To Plan The Size Of Your System?
If we know how many kilowatts we need to meet the electric requirements of our home, we are now in a position to size our system. If we are building a grid-tie system, you can use the average annual irradiance for your calculation since the objective is to make our payment to your utility company zero for a full year. If we are building a off-grid system, we need to pick the irradiance value for December since we need to produce sufficient power all year.
If you divide your requirements for the day by the irradiance, you will get the number of watts your system must generate. For example, if your home in Phoenix requires 600kw per month, or 20kw per day, your system would need to generate about 3600 watts per hour of full sun. Since solar panels quote the watts of power they produce based on the standard of 1,000 watts per square meter you can divide the 3600 watts by the output of your panels to get the number of panels required for your system. In our example, if the panel is rated at 150 watts, you would need 24 panels.
Please visit at this short and informative blog, http://free-home-solar-energy.blogspot.com to know how to build your own free solar energy power generator and save a lot of money on electricity.
Author Resource:-
Rita Weeks is a part-time Ph.D student from Houston University and doing thesis on how to use:free solar energy and solar energy for home use. Her forte is her passion in studying free solar technologies and writes about it for general awareness.
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