Wednesday, September 15, 2010

Energy Efficiency and Leverage - It's not about caulking and insulation.

Lawrence Livermore National Labs published a very interesting diagram of energy usage in the US for 2009 (above picture).
One thing to take away from it is that most of the inefficiencies ("rejected energy") come from:
  • transportation (37%)
  • losses during electricity generation (48%)
Combined commercial and residential losses amount to about only 7%.
So even if I could make all commercial buildings and houses 30% more efficient through energy efficiency retrofits, new appliances, smart monitoring, lighting and HVAC feedback controls, etc, that would only reduce the rejected energy by 2%.

Leverage comes from addressing transportation and energy generation and transmission.
  • Electric Cars:
    • LLNL assumes 25% efficiency for conversion of petroleum energy to useful transportation energy. If you assume that electrifying all transportation could improve this to 90%, that would reduce rejected energy by 24%. That's 12x the impact of green building on energy usage.
  • Distributed Generation: Solar panels and wind in your backyard.
    • Transmission losses are estimated at about 6.5% for 2007. If those losses were eliminated (optimistically) by putting solar panels and wind farms near the consumers, that would reduce rejected energy by ~1.5%, or slightly less than making all buildings "green" with respect to their energy usage.
    • A much bigger deal is the reduction in fossil fuel usage this would allow. Assuming that wind, hydro, geothermal, nuclear and solar are 100% "efficient"(no rejected energy), that means fossil fuels are only about 24% efficient. If you could replace all the coal with some combination of these other sources (preferably wind or solar to allow for distributed generation), that would reduce rejected energy by ~25%. That's 12x the impact of green building (albeit at potentially high cost).
This is not to say that green building is unimportant but, if this analysis is correct (or even in the ballpark), then it's far less important in the big picture of energy efficiency than I thought.
It is important to concede that the changing all transportation to electric drive and replacing all coal with solar or wind is a HUGE hurdle to overcome. Making buildings greener may not be the longest lever but it's one that is easier to deal with.