November 10, 2009 | 16
Editor’s Note: Scientific American ‘s George Musser will be chronicling his experiences installing solar panels in Solar at Home (formerly 60-Second Solar). Read his introduction here and see all posts here.
I’ve gotten some great responses to my call for stories about solar installations. In this post, I’ll describe the grid-tied photovoltaic arrays that people told me about, and in a subsequent one, I’ll mention other approaches such as solar thermal. I’m struck by the commonalties among our experiences. People report comparable subsidies and payback periods.
We have a 6.6 kW system, and maximum instantaneous generation I’ve observed is 5 kW. It has generated power for two years and covers all our household needs and one plug-in hybrid car (an A123 Systems/Hymotion); it generates about 15 days/yr more than I need (currently, the utility just keeps the excess). We converted our house space heating to electric space heaters and have seen significant savings in electricity (blower in furnace) and natural gas.
We had some installer problems (design). The electric utility wasn’t going to approve such a "large" system. We received a $2k tax credit and $20k rebate over 5 yrs.
I live in a sixteenth-century thatched cottage in the South West of England. The cottage faces almost exactly due south but is a listed historical building, so I cannot put panels on top of the thatch. However the garage is separate with a pitched roof facing 190 degrees (see photo above). As I write 1.8 kW panels are being fitted. This is the biggest array that will fit. In UK money, there is a government grant of 2,500 pounds towards the installation and a 0.39 pounds per kW-hr "feed in tariff". This should give me about 8% return on investment assuming 1,000 kWh per kW installed. That is reasonably conservative for this part of the UK. I costed purchasing the individual components and fitting it myself. It did not make sense for the saving compared to paying for the installation. In addition the grant requires use of an approved contractor. Because of the historic status of the house, officially described as grade 2 listed, I had to get planning permission to put in the panels (even though they were not on the house itself). This took two months, to allow for objections. The planning department were very helpful and other than the delay and a small fee it is not an onerous requirement.
Generally the climate is warm by UK standards though rather on the wet side as we get the first taste of Atlantic weather, so it’s not the best place for solar but not that bad either. In the first two days we’ve got just over 6 kW-hr, about as much as we could expect for this time of year. At 1330 UTC on a November afternoon we have a clear sky with the sun already quite low in the West (we are 51 degrees North, 3.5 West here). Nevertheless I’ve got an output of 1.15 kW from my 1.8 kW installation. I have attached some photographs of the installation on the roof, the inverter installation in the garage and for good measure the house. I hope you will recognise why putting panels on the house roof is not permitted under our historic-buildings legislation!
I don’t believe in doing eco things unless the economics adds up. The UK government changed its incentives recently, coming into line with Germany, to encourage take up. The theory is that this will generate enough economies of scale to do away with the subsidy. We’ll have to see how that pans out. I’m quite happy to update you on how we get on with this.
Our home solar installation could not have been easier. I believe the key is to find a knowledgeable installer. We have a 5,100 W roof-mounted, grid-connected system that went into operation in January 2009. Our installer, Rochester Solar, knew exactly what to do with the paperwork as well the actual construction. After a site survey they wrote a descriptive estimate for the system. Then we went to our town hall and got a building permit with absolutely no hassles. The installer did all the applications for the New York State incentives. This size system costs over $40k. NYS paid half that amount in incentives directly to the installer.
We did have to wait a few months for the state approval. That was because New York ran out of rebate funding and had to have the legislature renew it. Because Rochester Solar was confident of the approval, they pre-ordered materials. When constriction did begin it went smoothly and quickly. Less than two weeks after final approval, all the parts were installed and functional. The installer arranged for independent electrical inspection and we then informed the town to do their inspection to close out the building permit.
The system has now been operating for 10 months and has given us about 6,000 kW-hr of power. Our home is all-electric with a ground-coupled heat pump, so the PV system gives us about half our total electrical needs.
The final, great part of the story is yet to come. When we file our State and Federal income taxes in 2010 we expect to get credits of $5K and $6K respectively. That means our entire cost is under $10K. A simple calculation of the "pay-back" period is less than 13 years at our current electric rate. This is for a system we expect to last more than 25 years!
We think the governments are doing the right thing to promote everyone’s better heath, economic growth, and energy source security.
It’s been almost one year since I installed six panels on my roof and I have now proudly produced close to 1 MW-hr of electrical energy and fed it into the power grid. My six panels are rated for 170 W each, so 1,020 W total. These are connected to two converters, each taking a string of three panels.
The system is subsidized by the Dutch government by a payment per kW-hr fed into the grid. The subsidy has been designed so that the payback time for the investment should be around 13 years. The amount of paperwork was not too bad, although it took a long time before I finally received the first payments. The maximum amount of subsidy is based on multiplying the peak power by 850 equivalent hours per year (our country is not known for its sunny climate). Based on this I was expecting to produce about 870 kW-hr per year and I am actually delighted to see that I will end up at around 1,000 kW-hr. Perhaps this is due to the favorable orientation of my roof, which is almost perfect south with a slope of about 45-50 degrees.
Out of personal interest I read out the converters with my laptop PC once a week, and type the numbers into a spreadsheet. It yields an interesting record of the hours of sun per day and the generated energy during the various seasons. At some point when the year is complete, I will produce a few graphs.
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