Energy Efficiency Really IS a Big Deal
Frequent commenter and alternative fuels expert Ben Thorp responds to my piece on electric transportation the other day, noting:
Energy efficiency … may be the largest issue if saving fossil fuel or the global environment is a major concern. The US utility energy efficiency has been ~34% for decades as reported by the Department of Energy. When you add line losses and battery efficiency and driving losses there are huge efficiency challenges. Let’s focus on the major issues to see if anyone has solutions.
Ben: I think you’re right on here. It’s true that the efficiency of energy generation, transmission, and distribution is a big deal. If we start with a certain amount of chemical energy from coal or natural gas, for instance, obviously we want as much of that as possible to be delivered to the end customer. And even where efficiency appears to be inconsequential, that’s really not the case.
For example, let’s take solar PV. Efficiencies range from the high single digits into perhaps the low 30s. Of course, we’d all like this to be better, as improvements will decrease the cost per Watt. But is efficiency really the main issue? The fuel’s free; regardless of how much you use, the cost is still zero.
But let’s talk about the other components of the cost equation: the footprint of building the PV, shipping it, installing it, connecting it, maintaining it and disposing of it at the end of its useful life. And what about the land use? We love PV on our rooftops, but we get concerned when solar projects contemplate covering big chunks of the desert.
And what happens when the land we’re talking about is extremely valuable because of supply and demand, e.g., Bermuda? Last time I was there, one of the purposes of my trip was to advise the island national on the use of renewable energy and electric vehicles. They have 160 MW of diesel plants, and they hate them with a passion, but replacing them with solar really isn’t an option.
So yes, let’s drive those efficiencies. Thanks for the note.
Islandable micro-grids are what we need, and slowly and surely, no matter what the Too-Bigs want, we are going to get them. The other day my local community-supported-everything group made gas in a trash can out of compost. I’m not sure what they plan to do with it, maybe just heat hot-tub water, but people are going to be doing this stuff. I also live in a place famous for crazy, and one guy I met at a solar-car show turned his favorite retro-vehicle into an electric commute car. He charges it with his roof-top solar. Sounds like he considers the time spent doing all this as entertainment, entertainment with production. Kids can do this kind of thing also. Education-with-production is a school-reform idea that has been percolating for maybe 50 years.
Don’t expect to see dramatic efficiency gains for any energy production that involves steam driven turbines. The present engineering for coal, gas and nuclear has pushed the efficiency into the mid 30% range which is near the theoretical maximum delineated by the Carnot cycle. Now if all generation could take place on the Lake Superior, environmental effects being ignored, we could boost efficiency to maybe 40% Of course that is not going to happen. The more realistic route to increased efficiency that does not violate the laws of thermodynamics involves cogeneration or alternate uses for waste heat. For many yeas the sidewalks in Milwaukee were heated to prevent ice formation in the winter. They used waste heat. Heat from spent steam has also been used to heat green houses. Why take heat generated from off the grid 35% efficient turbine power when you can capture the 65% waste heat for a useful purpose?
Great info,and why are we not pushing for more enhanced geothermal plants, I think we’re missing the boat, and the heat
Unfortunately most geothermal sites do not have a good heat sink for the spent steam. After it goes through a turbine it must be condensed to reduce the pressure on the downside. When air cooling is used, the steam is not efficienty condensed. The overall efficiency of such a system is way below that of natural gas fueled turbine sited on a cold body of water. But, the steam is “free” so efficiency doesn’t matter, right? Wrong. The capital costs associated with a kwh of electricity generated from geothermal are negatively affected by the inability to cool the spent steam quickly. It would take a lot of green house tomatoes to replace the value of that lost efficiency.
Geothermal power in Iceland is optimal and that’s why it is so popular and cost effective. The spent steam has a lot of uses on the frozen tundra and the cold temperatures needed for maximum efficiency are readily available.