Your Questions About Renewable Energy Content

admin answers:

In 2004, the worldwide energy consumption of the human race was on average 15 TW (= 1012 W) with 86.5% from burning fossil fuels.[1] This is equivalent to 471,000 PJ (= 1015 J) per year. As shown by the difference between the first two images in this article, there is at least 10% uncertainty in the world’s energy consumption. Not all of the world’s economies track their energy consumption with the same rigor and the exact energy content of a barrel of oil or a ton of coal will vary with their quality.

The remaining worldwide energy resources are large, with the remaining fossil fuels totaling an estimated 400 ZJ and the available nuclear fuel such as uranium exceeding 2.5 YJ (1 YJ = 1024J). Mostly thanks to the Sun, the world also has a renewable usable energy flux that exceeds 120 PW

admin answers:

There’s an old paper floating around that you can find by Googling “nrel energy payback”. At least, the consumer summary of the study will come up. You can then pursue the original paper. That’s from about 10 years ago, and suggests an energy payback of 1 to 4 years, depending on the type of panel. We assume photovoltaic panels, of course. Additionally, the National Renewable Energy Labs could be a good source for finding other papers.

If you are at a University or large Corporation, ask your librarian for help.

I was at the Engineers for a Sustainable World conference a couple years back, and one of the presenters pointed out the fact that carbon payback time depends on the source of energy used to produce the panels, and the source of electricity that the panels are displacing. For example, it takes a certain number of kWh to produce a kg of aluminum for the frame. If the electricity came from a coal-burning plant, the carbon content is high. If it came from hydroelectric, the carbon content is nil.