Energy is very important to the world as a driver of the modern society. According to estimations done by the International Energy Agency (IEA), the total global energy consumption is about 17 500 TW·h/yr . In the past, fossil fuels like coal, oil and natural gas supplied the biggest part of this global consumption, and they were far larger than those of the renewable energy sources as Fig. 1 shows for 1973 . In 2011, the production of renewable energy and global energy consumption increased, even though renewable energy was still much smaller than fossil fuels as Fig. 1 shows. .
I E E E Instrumentation and Measurement Magazine, 2014, Vol 17, Issue 2, p. 27-32