Where to start

James Gautsch Posted By James Gautsch, Dec 12, 2008 at 4:17 PM

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  1. James Gautsch

    James Gautsch
    Member 2.

    Apr 2, 2008
    central susquehanna valley PA
    Starting to research the feasibility of generating solar electricity with thin film pv panel. How do you size the system. Is it based on the highest daily usage of the year? Is there a good website with info. Have looked at some, but they were mostly calculating your saving, if you knew the size of the panels.

    Thanks for any help you can offer.
  2. Dune

    Minister of Fire 2.

    Jan 14, 2008
    Commonwealth Of Massachussetts
    I just found a new (to me) magazine called HOME POWER. It is full of the type of info you are looking for, in addition to contact info for a large number of manufacturers. Plus there is a very large question and answer section, and the publishers seem very well informed.
  3. peakbagger

    Minister of Fire 2.

    Jul 11, 2008
    Northern NH
    Home Power is an excellent resource, they have a special right now where you can pick up a CD with their first 100 issues.

    The basics are

    1. Minimize your load in your house to the maximum amount possible. The dollars spent to reduce your load are a lot less than buying PV panels.

    2. Figure out what sort of rebates are availlable for your area. The fed rebate is now unlimited for 30% of the cost of your system after January 1st and throw in whatever state and utility rebates are out there. There may be a "sweet spot" where you maximize your rebate. Be careful of state and utility rebates to make sure that you can do the installation yourself, many of the rebates require a qualified installer (which may be a good thing dependent upon your skill level). While you are at it make sure you dont have some neighborhood association or deed restrictions that prevent you from installing panels.

    3. Plan on an install cost of between $8 and $ per installed watt, less if you install yourself.

    4. Figure out your average load over the course of a year from your power bill. Dependent upon your load and location, there are creative ways to reduce the number of panels by using time of day metering but for most folks it doesnt break even.

    5. Get some specs on the type of panels you are interested in, then plug them into the PVWATTS program (search for it on the web).

    6. Determine the location for the panels and detemine that you have zero shade from 9 am to 3 pm, year round. There is a device called a solar pathfinder that is real handy for determining this, but you can do it by looking up your lat and long at the US naval observatory web site for sun angle and location on June 21st and Dec 21st. Assume that the panels angle will be roughly your latitude. and see how may will fit without shading each other. Typically a shallow roof pitch can screw up how many panels you can install because of shading. The trade off is that panels mounted at other than roof pitch arent very attractive.

    7. Figure out how many panels you want to buy based on PVWATTS and then pick an inverter manufacturer. Look on any solar website and there are several manufacturers of grid tied inverters. Unless you need battery backup and have extra money to spend (far more than a generator), pick a batteryless inverter. There should be a link to a sizing program for the inverter on the website. Enter the number of panels and type and some other basic data and the sizing program will determine what size inverter you need and the possible wiring configuration of the panels. You may have to add or subtract panels to optimize the fit with the inverter.

    9. Now its reality check time. Add up the costs of the panels, inverter and mounts add $1 to $2 per watt for install and see if you can tolerate it once the rebates are figured in. Unless you have great rebates, your decision to add solar panels are not going be economic, rather you are doing it to lock in power costs for the long term or have political or technical reasons to generate your own power.

    10 If you can live with the cost, search for John Wiles on the internet and you should be able to find his detailed PV design instructions to download that reference the national electric code, read through it and if you dont understand what he is talking about, pay an electrician who knows solar to design and install to code. Alternatively buy a preengineered kit woth good instructions.

    11. Be aware you are dealing with very high DC voltages (up to 400 volts) that are present whenever the sun is out and potentially are going to be present for 20 to 30 years. If you dont follow the code and make a mistake, someone can get zapped and unlike AC, DC doesnt give you the option of letting go.

    Good luck
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