I am curious about how much of the energy that a solar panel of a given size and capacity will produce in it's lifetime, and what fraction of that energy was required to produce it in the first place?
Best way to determine that is to find the retail cost of a solar panel and compare it to the retail cost of oil. Assuming similar profit margins a $300 solar panel costs the same to produce as 00 gallons of oil.
At present the technology to create silicon solar cells is incredibly energy intensive. It is not logical to compare the cost of oil to the cost of a solar cell because they are not priced according to energy input. Oil has a strong advantage in that it is concentrated solar and geothermal chemical energy that has accumulated over millions of years. The price of oil does not reflect its energy content, but the cost to retreive it. Electrical energy used to produce a Photovoltaic cell is not priced in any proportion to oil. By some calculations it will take about 50,000 KWh of energy produced by the PV cell before it can recover the energy used to manufacture it.
The attached link is to an article from the 200 Home Power magazine. In that article the energy payback was found to be between 2 and 4 years. Newer panels are more efficient primarily because the silicon wafers used today are thinner. The silicon cell embodies most of the energy required to make a solar panel. Today most solar panels will produce the amount of energy required to manufacture them in between about 9 months and 2 years depending upon the specific technology used to make it. Solar panels are expected to produce energy for between 30 and 50 years. Therefore it takes around 5% of their total energy production to produce them. Note that these figures depend upon where the panels are installed. Panels in very sunny areas may generate more than 3 times the energy of panels in a cloudier area. Edit - The energy payback meta-study that carbonates references below mention one particular study Alsema (2000), which the authors used as a baseline to come up with their 4 year payback figure. These studies DO NOT assume ideal conditions. The Alsema study assumes an annual an irradiation of 700 kWh/m2/yr. That is the United States average irradiation and does take into account cloudy weather and the like. Under idea conditions the amount of energy collected can be almost twice as much. Albuquerque New Mexico is an example. The figures I mentioned above are recent values reported by several different panel manufacturers with whom I discussed the issue at the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion held this May. The very long payback times that carbonate highlights are almost certainly wrong. The study he references concludes that paybacks range between 2 and 8 years with 4 years being the most likely. In my opinion payback times are actually a fair bit shorter based on conversations with the manufacturers.
