Solar Power Calculations.pdf

Solar Power Returns|Solar Calculations| benefits from installing ...http://www.solar-estimate.org/?page=solar-calculations Click on our free solar estimate tool to do an accurate solar cost benfeit analysis About Us Terms of Use MY SOLAR ESTIMATOR MY WIND ESTIMATOR FIND A PRO How it Works IMPORTANT STUFF Frequent QUESTIONS RESOURCES & LINKS JOIN The Network We could not set a Cookie in your browser. To use all features on this site you must enable cookies in your browser. If you have cookies enabled, click "REFRESH" on your browser to try again. » How to enable Cookies in your browser Solar & Wind Energy Calculations: The (very) Basics This is a simplified, "lay persons'" overview of how solar energy systems calculations are made. The solar estimates provided via our solar estimators are much more complex and complete. This simplified overview is meant only to provide the reader with a very basic understanding of some solar energy system calculation methods. In addition to the information provided below, try our Solar & Wind Estimator and here are some books we suggest you read to help you learn more .... Photovoltaics Solar Water heating Wind Energy General Terms Photovoitaics (PV) is the direct conversion of light into electricity. Certain materials, like silicon, naturally release electrons when they are exposed to light, and these electrons can then be harnessed to produce an electric current. Several thin wafers of silicon are wired together and enclosed in a rugged protective casing or panel. PV panels produce direct current (DC) electricity, which must be converted to alternating current (AC) electricity to run standard household appliances. An inverter connected to the PV panels is used to convert the DC electricity into AC electricity. The amount of electricity produced ¡s measured in watts (W). A kilowatt (kW) is equal to 1,000 watts. A Megawatt (MW) is equal to 1,000,000 Watts or 1,000 Kilowatts. The amount of electricity used over a given period of time is measured in kilowatt-hours (KWh). For a more in depth overview, please see our General Overview: About Solar Energy & Solar Power What is a solar rating? The solar rating is a measure of the average solar energy (also called "Solar Irradiance") available at a location in an average year. Radiant power is expressed in power per unit area: usually Watts/sq-meter, or kW/sq-meter. The total daily Irradiation (Wh/sq-meter) is calculated by the integration of the irradiance values (W/sq-meter). Click here for the Solar Radiance map of the USA. Shading: If your solar collectors or solar panels experience any shading during the day the output of your solar energy system can be dramatically reduced. This is especially true of photovoltaic (PV) solar panels since a partially shaded PV panel can result in a loss of power across the PV array. Some solar incentive programs, such as the California Solar Initiative (CSI) reduce the incentive available to you if your solar system is impacted by any shading. Solar Electric (Photovoltaic) System Calculations Estimating Solar Electric (PV) System Size: Are of Solar Panels 1 of 5 3/12/2013 2:54 PM a solar energy system will provide output for about 5 hours per day. South facing None PV Energy delivered as % of manufacturers rating 95% Wiring & power point tracking losses Inverter Efficiency Total Energy Delivered 9% (91% delivered) 90% 95% x 91% x 90% = 78% 2 of 5 3/12/2013 2:54 PM . the panels are shaded 1 divided by 5 = 20% of the time (80% of assumed direct sun shine hours received). http://www. washed frequently: 98% design sunlight transmission 25C. Converting Power (watts or kW) to Energy (kWh) One kilowatt-hour (1 kWh) means an energy source supplies 1. the output of a 200 square-foot PV panel system would be 3.. For example.800 watts (1. if you have a 1.285 kWh per year x 80% = 2. This would produce.8 kW system size and it produces for 5 hours a day.org/?page=solar-calculations On average (as a general "rule of thumb") modern photovoltaics (PV) solar panels will produce 8 .8 kW) of electric power.000 watts (1 kW) of energy for one hour. including the following . calm wind Non-battery tilted at your latitude. Estimating Solar Electric (PV) System Size to Replace a Specified Amount of Utility (grid) electricity PV System Capacity Required (kW of PV) can be roughly calculated as follows: Annual electricity usage = Monthly Usage x 12 months.628 kWh per year.285 kWh in a year (1.. the output would be reduced in accordance to the shading percentage. if the PV panels receive 4 hours of direct sun shine a day (versus the standard 5 hours). 9 watts per sq-foot. a roof area of 20 feet by 10 feet is 200 square-feet (20 ft x 10 ft). So. If the PV panels are shaded for part of the day.solar-estimate. or 200 sq-ft x 9 watts/sq-ft = 1. roughly. the "78% used above assumes the following losses across the PV system: Factor Solar resources Soiling or contamination of the PV panels Temperature System configuration (battery or non-battery) Orientation to the sun Shading Assumption Assumed solar availability: As per PV Watts Clean. In this case.10 watts per square foot of solar panel area.8 kW x 5 hours x 365 days).Solar Power Returns|Solar Calculations| benefits from installing ... Electricity usage is express in kilowatt hours (kWH) KW of PV = (Annual Usage) / (78% x kWh/kW-year from Solar Radiance chart below) Energy production from a solar electric (PV) system is a function of several factors. For example. Generally. 365 days a year: This solar energy system will produce 3. water temperatures.7 watt Then the power that can be extracted from the wind assuming 20% turbine efficiency is: Pturbine=0. Wind Turbines: How Much Power and Energy Does a Wind Turbine Generate Only a fraction of the wind`s power can be actually extracted out of the wind. There are many other factors which affect the performance of a solar thermal collector. Small wind turbines tend to have efficiencies at the lower end of this range.750 hours = 177. the air that hits the blades keeps some speed allowing the air to move out of the way.650 kWh. and the thermal losses (efficiencies) inherent in the solar thermal system. over the course of a year (365 days) about 3. Solar Rating & Certification Corporation (SRCC) is generally used as a reference for solar thermal system performance ratings. a typical unit of measure for electricity. The kBTU units can be converted to kWh.4 mph). there is no way to harvest all of the wind`s power. usually expressed in thousands of BTU's per day (kBTU/Day). a typical solar collector about 100 sq-ft in area will produce about 32 kBTU on a clear (no shade) day. the theoretical limit of wind energy that can be converted to rotational energy at the turbine`s shaft is about 59%.2 kg/m3) 3 of 5 3/12/2013 2:54 PM . Wind Example: If you have a small wind turbine with a blade diameter of 1 m (about 3 ft) and an operating efficiency of 20% at a wind speed of 6 m/sec (about 13.Solar Power Returns|Solar Calculations| benefits from installing . For example.e. then the air that hits the blades would have to come to a complete stop (i.3 watts × 8. which is about 1. http://www. This is not possible because continuous operation of a wind turbine requires that the air that hit the blades then "get out of the way" to let the air that is behind also hit the blades. In reality. Or. the volume of water being heated. the air would stack up in front of the turbine. Each collector will have a rated output.solar-estimate.3 watts If this ran continuously for a year (about 8. to calculate how much power the turbine can generate at this wind speed: Rotor swept area: Area = Π × (Diameter/2)2 = 3. This value is known as the Betz Limit. If all the energy from the wind was transferred to the blades. According to the laws of physics..625 watt-hours. please see our General Overview: About Solar Energy & Solar Power Most typically.20 × 101. the collection efficiency of commercially-manufactured wind rotors is typically 25% to 45%. Then. a solar water heating system for a home or small building will use "glazed" flat-plate collectors. rather than through it. If all of the wind's energy was transfered to the wind turbine.785 × 63/2 = 101. or about 177 kWh in a year.785 m2 Available power in the wind: Pwind= Air Density × Area × v3/2 = 1. In practice.org/?page=solar-calculations Solar Thermal System Calculations for Water Heating Solar thermal collectors come in many types and sizes. thus allowing continuous flow of the air into the turbine. including ambient air temperature.14 × (1/2)2 = 0. You might want to visit their web site to learn more. Then the wind would have to blow around the turbine.750 hours) then it would produce: 20.. A typical solar thermal collector will produce about 10 kWh per day. (Note: we used the density of air at sea level.7 = 20.2 × 0. For a more in depth overview. all the wind`s energy was absorbed in the blades). you'll probably have some fun doing it. you might want to monitor the wind speed at your location.solar-estimate.Solar Power Returns|Solar Calculations| benefits from installing .org/?page=solar-calculations Wind Turbine Metrics Wind Energy Curve of a typical wind turbine Tip: Measure the wind characteristics at your location. The one pictured to the right is about $100 at Amazon.. White Wind Resource Maps are available from http://www.windpoweringamerica.gov Suggested Books to Help You Learn More Photovoltaics Solar Water heating Wind Energy 4 of 5 3/12/2013 2:54 PM . http://www. And. If you are thinking of installing a wind turbine. There are several weather stations and wind speed meters (anemometer) available that can provide this information to you at a reasonable price.com: La Crosse Technology WS-1612AL-IT Professional Weather Station. first.. As a business verification service. user-friendly means for home and small commercial building owners to make preliminary evaluations of renewable and solar energy options for their location. energy efficiency data. public service. solar energy and energy efficient measures.Solar Power Returns|Solar Calculations| benefits from installing . including financial analysis tools. and utility information about renewable energy. install a solar system for your home. 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