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Photovoltaic (PV) Electricity
The idea of ‘living off the grid’ may stir mixed emotions in hurricane-weary Gulf Coast residents, but there are situations where making your own electricity from the sun is the best solution. The cost of running service from main power lines to secluded rural home sites or camps may tip the scales in favor of self-generated electricity. The quiet power of a PV / Battery system is nicer than the drone of a generator and the hassle of transporting fuel and keeping it running.
Metering’ is in place in
Alabama for Alabama Power customers. In August, 2008, the Alabama
Public Service Commission authorized Alabama Power's rate plan
'PAE' which permits buy-back of PV- and wind-generated electricity.
See the Alabama Power website for further details. Other
state electric cooperatives and organizations have various policies and
approaches to ‘Net
Types of PV SystemsThe different configurations of PV systems you can put in are (in order of increasing complexity and cost):
We treat each PV system as a separate design project with unique requirements to give a firm quotation. But, to give an overall idea of the money involved, sizing and cost estimating for PV grid-tie systems goes roughly like this.
PV system size is measured in KW, or thousands of watts of solar panels. A 200 watt (0.2 KW) rated panel nominally makes 200 watts per hour in full sun. Panels make more power when it is cold and less when they are hot. Simplisticly assuming 5 hours of full sun per day, this panel would generate 1000 watt-hours of power daily. With a $0.10/KWH electricity price that would be a dime's worth of power a day and $3 per month (30 KWH) off of an electric bill.
A system with ten 200 watt panels would be called a 2 KW system. For a simple example, an estimating price of $10 / watt of installed panel for grid-tie systems would give a rough price of $ 20,000 for that system making $1 worth of power a day and $30 (300 KWH) per month. (Costs simplified for ease of calculation. System prices have been trending much lower and electricity prices higher than shown.)As you see, things get very, very, expensive in a hurry without rebates and incentives. A PV system big enough to take $100 per month off of a utility bill would use 60 3'x5' panels. The payback periods for domestic PV systems in Alabama is around 20 years with current electricity prices. Payback periods are a lot less in parts of the world that might pay 40 or 50 cents per KWH.
Domestic PV systems should be used in conjuction with solar water heating systems, LED lighting, and other improvements. Solar is a much more economical way to collect water heating energy.
Florida offers a significant rebate for domestic PV which helps the economics a lot. Commerical PV systems qualify for the 30% Federal Investment Tax Credit. With the two credits combined, a Florida business can get into PV very economically. Florida solar rebate details are found here. . Alabama and Mississippi must rely on the federal tax credits only. TVA offers some PV incentives through some local distributors. A nationwide listing of available state incentives is found here.
Battery System CostsThe costs for adding batteries to a PV system for backup or off-grid are dependant on how much backup you want and how long you want the batteries to last. Batteries last longer with lighter discharge cycles. You only get back out 80% of the power you put into batteries, so that must be factored in, too. You must decide whether you want maintenance-free AGM or gel batteries or conventional lead-acid ones that will last longer and hold more power. All these considerations make battery selection a case-by-case situation that can't be addressed with an estimating rule of thumb.