Friday, September 21, 2012

Home Photovoltaic (PV) System -- For Archival Purposes Only

Link at The Oil Drum

Data points:
  • sunny San Diego
  • personal hobby
  • solar panels
  • batteries to store electricity
  • provides electricity for refrigerator, attic fan, television and associated entertainment components, two laptop computers, the cable modem and wireless hub, and a printer;
  • what is not provided for: heating water; washer; dryer; heater; air conditioner; all lights (interior/exterior); freezer (unless part of refrigerator); dishwasher; power tools; electric pencil sharpener; electric toothbrush; 
On the economic side, taking the advertised capacity for a lead-acid battery at face value, I can get a Trojan T-1275 for $235, and if treated gently it will provide an energy outlay of 750 full-cycle-equivalent discharges. Each full discharge has 12 V times 150 Ah, or 1.8 kWh. This works out to $0.17 per kWh
If I instead cycle at 50% and get 575 full-cycle equivalent outlay at a de-rated 1.5 kWh/cycle, the cost is about $0.28/kWh
Since my system uses the battery for half its energy needs, the effective cost of electricity for battery replacement alone is about $0.14/kWh, which is pretty close to the utility rate in San Diego.
Bottom line:
So why would anybody go this route? 
In remote locations, the cost of running utility power lines can be prohibitively expensive, quickly tipping the scales in favor of off-grid PV (the sunk investment in panels, etc. can be less than that in utility installation, in which case the cost of batteries offsets the steady utility bill). And I must say I enjoyed having power during the San Diego blackout of 2011. Moreover, I get pleasure out of having my own power generation capability. It’s part hobby, part independence, part practical. All cool.
  • some years ago (2010, time frame) when I was tracking the cost of solar energy, it was about 30 cents/kWh; not much change over the years
  • battery replacement: a) lump sum, front-end cost; b) disposal issues for the old batteries; c) batteries alone exceed slightly the total utility rate
  • part hobby, part independence, part practical; one could add: part tedious
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