06-02-2009, 06:33 PM
OK, let's look at your response to my comment below:
quote:
Except for rainy season, we produce quite adequate power.
Quote from TY:"If I install a system and someone utters those words, that's like me selling someone a truck to pull their boat but not telling them it won't have the power to pull the boat uphill. And the thing is, those words are being uttered on GOOD insolation years. What happens when we have a bad one? The system I design will be fine. The system most installers design will be sucking tanker loads of gas to power the generator. I feel generators should only be used for surges, not as a tow truck for the truck that can't pull the boat over the hill."
OK, I honestly had hopes my system would NOT require a backup generator. In fact, I ran it most of the 1st year without one, but I was building and not living there - no lights, no water system, no power needs after dark at all - so not a fair test of the system. But I did come to realize I would need back up, especially once the pool was brought on line.
So let's examine so real data and build me a system that would would need a generator for surge only, not make up for rainy season lack of sun. No doubt, the system designed in previous post would be adequate.
Using my systems actual data, my worse 4 days this rainy season are:
3/5 - 5.2kw
3/6 - 8.3kw
3/7 - 2.3kw
3/8 - 3.8kw
That's an average of 4.9kw per day. Definitely bring my battery bank below 50%.
My requirement is still 15kw per day.
On these days, I only produced 32.7% of my requirement, averaging only 1.09 hours isolation.
So using my current 4.5 kw system as reference, I can figure that those days I produced 1.09 kw per kw of PV. Needing to produce 15kw would require 13.78 kw of panels. My panels are 125watt, therefore 13.78 divided by .125 = 110.2 panels. My arrays are 4 panels each, so 110.204 divided by 4 + 27.55, rounded to 28. 28 arrays of 4 = 112 panels @ 125watts each = 14kw system. 14Kw X 1.09 isolation = 15.26kw production.
Based on the $/kw cost of my current system, this upgraded system would cost me: $143K. Of course, this does NOT include the supporting roof structure I'd need to support it. Obviously, this is a solution only for the well heeled - not me.
So how did I survive with my theoretically inadequate system? My generator. As previously stated, I've run my diesel generator approx 250 hours the last 22 months. For ease of figuring, let's call it 125 hours per year. If it costs me $4 per hour to run my generator, that would be $500 per year - not exactly sucking tanker loads. So to balance this out, I can spend $90K immediately to avoid the genset. To be quite honest, at my present age of 62, even if my generator cost were to double to $1k per yr, I doubt I'll live long enough to break even. I also suspect my wife, son, and granddaughter would prefer we spend $500-$1000 per year rather than drain an immediate $90K out of our retirement and their inheritance.
Bottomline - I don't like the genset, but economically, it's a reasonable tradeoff.
Sidenote: I did another analysis - Windpower vs Genset. Only $20k for a viable wind generator with no guarantee of output. Again, that's 20 plus years of diesel and known output.
OK, break time
David
Ninole Resident
Ninole Resident