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| Grid Tie Solar Energy System with Battery Backup Power Information How To |
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| Part One Grid Tie with Battery Backup, 1 Find the wattage of every item that can or will be ran at the same time. Remember battery power in a backup system is normally limited so do this with survival mode in mind. Just what you have to have to keep on going for 24 hours. Maybe things like the fridge, alarm clock, a light, coffeepot, the hot water tanks thermostat and most of all, the little ladies hair drier. 2 Total all the wattage and you have your minim inverter size. 3 Next you need to know how many hours or minutes each item will be ran in 24 hours. 4 Based on the information above you will size your battery bank. If the above tells you that you require 5,000 watts of power per day. You already know what inverter you have chose so the battery bank voltage will be 12 volts, 24 volts or 48 volts. Divide the wattage by the volts to get your battery bank AH rating, 5000 watts / 48 volts = 104 Amp-hours in battery power at 48 volts. Double this to 208 AH because you never want to run your battery bank lower then 50% discharge. Part Two Grid Tie with Battery Backup, 1 Gather up your last 12 months electric bills. 2 Total the kWh from all 12 electric bills and divide it by 365 days. (kWh equals 1000 watts.) 3 Look on a solar isolation map and find the average Peak Sun hours for your area. 4 Divide lines two and three. 5 To allow for heat losses in the solar modules, voltage loss in long wire runs, energy loss in the inverter (inverters use electric to operate) add 15%. 6 Get a site shading survey, This will track the sun’s path and give the effect a tree or house might have. Add this percentage to the above. (normally a dealer only item) Example: 12 months electric bill shows a total of 6,600 kWh. Add three zeros to the end to get total watts (6,600,000 watts). 6,600,000 / 365 = 18,082 watts per day For Northwest Arkansas the average Peak Sun Hours are from 4 to 5 hours. 18,082 / 5 = 3,616 watts in solar modules. Now lets add back in the heat, inverter and wiring loss of 15%. 3,616 * 1.15 = 4,158 watts in solar modules To completely wipe out your energy bill you will require 4,158 watts in solar modules as long as there is no problem with the shading survey. Look for a Look for a solar energy grid tie battery backup system in this list by looking at the array size. All you need next is to find a contractor in your area to install it. Or you can do it your self and hire an Electrician to get the permit and twist the wires. You will want a solar grid inverter that will be able to back feed all of the solar energy produced. No need for any larger unless it is a battery backup system. If by chance you have a large starting surge from a compressor in your shop and it requires more power then your solar energy inverter can produce. The system will switch over to the grid to get the extra power required. As in the above example of a grid system we ended up with 4,158 watts in solar modules. Lets make sure this is enough energy to charge your battery bank. Divide 4,158 by the voltage of the system 48 volts = 86 amps out put from the solar array to the battery bank. Now you need a minimum of 5% (better to have 10%) rate of charge. The Battery bank was 208 AH times .05 = 10.4 amps required to charge the battery bank. You are well inside the minimum limit. |
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05-26-08