I got into a pretty good debate about solar photovoltaic (PV) systems and it forced me to double check my facts. Here is what I found, along with some references... Solar photovoltaic systems are not the bargain that many people would like us to believe; however, it is also not a failing technology. People have many motivations for installing a PV system. The facts below only deal with the economic reality of such systems and the likelihood of seeing a financial benefit. Check out one of the many systems that Enphase Energy customers allow you to view; https://enlighten.enphaseenergy/public_systems. From these systems, we can see that daily the systems produce a fraction of the full rated power and the expectation in NC should be about four to five times the installed rating maximum per day when there is a full day of sunshine during the longest days of the year. Verify this using the systems available on the Enphase Website. A Granite Falls, NC example is https://enlighten.enphaseenergy/public/systems/V8zY217622 (32 panels X 225 W = 7,200 W; 7,200 W X 5h = 36,000 Wh = 36 kWh). The assumption that the sun shines this much in NC is not realistic and the reality is that the solar insolation is one half or less of this assumed value. The example system was not installed very long, but others realized approximately one half of the assumed value averaged over a year. Therefore, we should consider 18 kWh for this example system During 2013, the actual cost per watt installed for a PV system in the US is about $5 (nowhere near $1). See this report from Berkely and note the first bullet on page 1; emp.lbl.gov/sites/all/files/lbnl-6350e.pdf. The Berkeley report is also summarized well in this article; thinkprogress.org/climate/2013/08/13/2455121/solar-getting-cheaper/. Note that the second article points out that government subsidies in other countries allow for lower installation costs and these subsidies do not exist in the US yet; however, tax rebates are not explored. Assuming the example system in Granite Falls, NC cost $5 per watt to install, the system might have cost 7,200 W X $5 = $36,000. Note that in the 2013 tax year, NC DOR and the IRS allow for tax rebates for installing renewable energy systems; 30% federal tax rebate and 35% NC state tax rebate. So the example system might cost as little as $12,600. Assuming a displacement of buying power at $0.10 per kWh (typical in NC), the cost of that same power is 18 kWh * $0.10 = $1.80 per day. Recouping $36,000 would take nearly 55 years ($36,000 / [$1.8 per day X 365 days / year] = 54.79 years). Recouping $12,600 would take nearly 20 years ($12,600 / [$1.80 per day X 365 days / year] = 19.7 years). Again, that assumes half of the time the sun shines all day, just like it does on the longest days of summer. At 18 kWh per day, the example system would pay for itself in about 20 years after allowing for tax rebates. Note that the projected lifetime for a PV panel is about 25 years; they will still produce power, but usually at 80% of the rated capacity after 25 years (90% in 10 years). Look at the specs for any panel, but here is a nice comparison of the top ten panels solar-panels-review.toptenreviews/. Note that this site indicates a 20 to 23 year cost recovery, which is close to these calculations on the sample NC system. Soon after recovering your costs, the system will need to be replaced due to the reduction in capacity. There are other costs; the panels need to be cleaned regularly, the elements could cause wiring or mounting failures, wind and hail damage can occur. Most people will not be able to afford the install and will need to finance part of the cost, adding interest to the bottom line. Ultimately, although I think that PV systems will eventually be financially viable, the 2013 pricing is not there yet. Someone installing a PV system will need to have a motivation besides saving money.
Posted on: Mon, 26 Aug 2013 04:45:14 +0000
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