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Sneak Preview of a New Book Available In a few months |
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Wagonteamster |
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WAGONTEAMSTER .COM |
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Introduction This article is intended to show the monetary costs of constructing and maintaining a photovoltaic electric system in 2012. Whenever possible, I used actual or advertised figures to obtain the numbers shown on this webpage. Before setting out to build your own photovoltaic system it’s a good idea to add 10 to 15% to the figures you see in this article - because, that’s usually how things work out. Off the Grid System Material Costs The major material costs for an Off the Grid solar-electric system include: the solar panels, racks to hold the solar panels, a charge controller, storage batteries, inverter, wiring and connectors. In addition, there is also shipping and handling fees for the material that is purchased. Here’s a chart showing the costs of materials for my 720 watt systems that I have installed on the wagon: |
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When designing my system, I had to make some assumptions about the availability of sunshine and how much my panels would produce. Being in the Western United States, where it’s normally sunny I conservatively assumed the following: 1. An average of at least 6 hours of sunshine per day 2. No more than one completely cloudy day in a row. With these assumptions, I should be able to draw about 180 watts of power from my system, 24 hours a day, 7 days a week. I’ll explain: Average solar panel output - 720 watts for 6 hours = 180 watts (average for 24 hour period) Battery storage capacity = 534 Amp/hours x 12 volts per battery = 6,408 watts of storage capacity. Divide this by 36 hours to allow for one cloudy day; and I have 178 watts of storage capacity per hour for a 36 hour long cloudy or dark period of time. This system allows for the daily consumption of 4.32 Kilowatt/Hours of Electricity Monthly KWH production = 130 KWH
Multiply my wagon design by three times and others could install an electric system for a 2000 square foot home that does NOT use electricity for heating, air conditioning, drying clothes or cooking. A normal 21st century lifestyle can be maintained with this amount of electricity. If you reside in a less sunny area of the world, I would double the size of this installation to achieve the same amount of electricity for the home. If you need to also supply 240 volts AC for a well pump, you will have to go with a more expensive inverter that supplies 240 volts along with 120 volts. |
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Grid Tie System Material Costs A Grid Tie photovoltaic system has both advantages and disadvantages over and off the gird installation. The major advantages include: the owner is not limited to his peak loads - air conditioners and electric clothes dryers can still be used. Also, it’s not necessary to buy and maintain storage batteries. Disadvantages include: the owner still needs to be tied to the grid, inverters are more expensive, and a Licensed Electrician will probably be required to tie-in and install and wire your system. To look at material costs for such a system, I used a system that has (9) 240 watt panels (essentially three times the size of the Off-the-Grid wagon power system). I tried to size this for a 2000 square foot home that was fairly frugal in their use of electricity. |
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If we make the same assumptions for the amount of sunshine the system will receive, then the panels will produce a full output for approximately 6 hours per day on average. Since it is a grid-tie system, I don’t have any batteries to worry about. When I’m producing an excess of power I get paid for it. When my system is not producing electricity, then the power comes in off the pole and I pay for it. At 6 hours per day, a 2160 watt system will make 12.96 Kilowatts Hours a day; or, 389 KWH per month. To see how this compares with your electric use, look at your electric bill. If it’s about the same, then your electric bill for KWH’s used will be about zero. However, still expect some payment as there are also charges for just being connected to the utility. If you want to increase the size of the system (to lower your bill further, or because you have a larger electrical need, then multiply the cost proportionally and you should come up with a number that is close. |
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Installation Costs These are going to vary, depending upon how much you know and your abilities. Unless you are competent working with electrical energy, always have Licensed Electrician do the wiring. Depending upon where you live and what you are doing, it may also be a legal requirement. Remember - once the light hits the panels, they start producing electricity. If you tie more than one panel is series to increase the voltage, you can produce a voltage that can be lethal. Also, there are a lot of hazards associated with working with batteries. My best estimate for pricing the installation costs are; I would assume about 10 to 20% of material costs for mechanically installing the panels. I would also assume 10 to 20% of material for wiring the system by an Electrician. |
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Summary The costs of a photovoltaic electric system have been coming done steadily. It’s possible to install a system that can produce approximately 400 KWH of electricity a month for a reasonable cost. If you kept your electricity use fairly low, you can end up without a monthly bill, or even independent of the electric utility. The following chart compares the estimated price of the two systems: |
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