Lawrence Livermore National Laboratory recently released the 2012 U.S. Energy Flow Chart. The chart shows how energy flows through major sectors of the U.S. economy, and how efficiently that energy is used. Most striking is that overall the U.S. is only 39% efficient at converting energy into useful services. Put another way, it takes over 2.5 units of energy to generate 1 unit of useful energy services. Most of the rejected or wasted energy is in the form of waste heat. In the electric generation sector transmission and distribution (T&D) losses are also a major source of rejected energy. The Energy Information Administration (EIA) estimates that T&D losses average about 7% in the U.S.. Though there is room to increase efficiency in every sector, the greatest opportunities lie in the electric generation and transportation sectors.
Where there is significant waste, there is also significant opportunity. Cogeneration or combined heat and power (CHP) has great potential to increase overall efficiency. Where buying electricity from the grid and generating hot water or steam from a boiler is about 50% efficient, CHP systems are up to 80% efficient at providing both services. This explains why CHP is increasingly popular, particularly in industrial and institutional settings where full advantage can be taken of both the electrical and heat outputs.
Other highlights from 2012 include:
- Overall energy use was down 2.2 Quads in 2012
- Natural gas use rose in 2012 while coal and oil use both decreased
- Wind power made the greatest overall gains in 2012, adding .19 Quads of generation
- Solar had the greatest percentage increase rising 49%
- Shutdown of 4 nuclear power plants accounted for the first measurable decrease in nuclear power in a decade