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Re: [Phys-l] Efficiency problem



Most certainly the economic feasibility of these ideas depends more on factors that don't involve physics rather than factors that do involve physics. I'll state some questions, then explain why they're important.

(1) Where will you get the electricity to do the pumping?

(2) Where/How will you use the electricity you generate?

(3) How is the distribution, switchover, etc. handled?

If you are not the power company, but you buy/sell from/to the power company you cannot win with a scheme like this. When you buy the electricity to pump the water, you pay the generation cost, the transmission cost, a distribution management cost, and some administrative costs. In my area these all add up to about 9-cents per kilowatt-hour. The generation portion costs users about 5 cents-per-kilowatt-hour, however, the actual cost for the power company to generate the electricity (that is, to operate just their generators) is about 3 cents-per-kwhr. When you buy from the power company you have to pay all costs (9 cents). When you sell to the power company they only pay you their actual generation cost (3 cents). Thus, you buy at 9 cents and sell at 3 cents. Please tell me how to make money from this scheme. You lose big time even if you have 100% efficiency. Even if the power company offers non-peak rates, that only lowers it from 9 cents to 7 cents in my area. You still cannot win. Worse, the power company can limit the electricity they buy from you if they don't need all that you generate. You might not even have a market for the full generating capacity you have invested in.

In order to win at this game (assuming you are not the power company yourself) you have to directly use the electricity you generate. If you buy at off-peak rates, then use the the energy yourself during peak times, you are pumping water with energy that costs perhaps 7 cents/kwhr and then you are using the stored energy to offset your peak usage that otherwise would cost you 9 cents/kwhr. If you could reach 100% efficiency you could save 2 cents/kwhr during your peak usage times. However, there is a huge "gotcha" in this process...

If you are going to use your electricity directly (rather than selling it to the power company) you have to be able to distribute your electricity (get it to your usage points, or to your local buyers) independently from the distribution system owned by the power company. If you are able to save 2 cents per kilowatt hour, how long is your payback period if you not only invest in the installation of the reservoir system with pumps/generators, but also the cost installing a distribution system, and also the costs of maintenance for both the generation and distribution. The payback is either non-existent or is getting well over 25 years, which puts it far enough out that you can't guarantee it will ever actually pay back. The only people who can make this work are the power companies themselves.

Remarkably, the same is true for wind power and solar power (where you don't even have to buy electricity for your generation process.) I was on a team that explored installing a 3MW Vestas wind turbine on Bluffton University land. The wind study was positive. The site was excellent. Including the purchase, installation, maintenance of the turbine, and selling the electricity to the power company at 3 cents per kWhr, the payback appeared to be 10 to 15 years if the turbine on average operated at 50% capacity, and if the power company would always purchase the entire output of the turbine (something they would not guarantee).

With a possible payback of 10-15 years, and without a guarantee that American Electric Power would buy the full output of the turbine for the next 15 years and beyond, there was no guarantee this project would ever pay back. Even if we could guarantee a 10-year payback, the administration is looking for guaranteed paybacks of 5 or 6 years or less.

However, if the energy from the turbine could be used directly on campus, then the turbine's electricity is worth 9 cents rather than 3 cents/kwhr. That cuts the payback down to 3 to 5 years... a definite green light... except... we don't have the distribution system on campus that would allow us to do this. Universities that already generate their own electricity from coal or natural gas could do this because they are already set up to use the electricity they generate. But a university or small town that is not already set up this way would have a tremendous cost involved. The local distribution cost (including controls to utilize power from AEP when the turbine is not generating the full needs of the users) was projected to cost up to twice the cost of the turbine itself. That puts us right back into a the long payback period.

The picture looked better if we would install 4 to 8 turbines and try to power the whole university plus the whole Village of Bluffton and surrounding area, but that moves the project from a 4 to 5 million-dollar project to a 20 to 40 million dollar project and involves a partnership between a private university, a village, a county, and American Electric Power. Bottom line... not interested. The university is in the business of education. The village is in the business of providing schools, roads, police, fire protection, etc. Neither wants to become the power company.

I found this whole study to be very sad and very discouraging. It made me realize that doing the right thing is not something that individuals, or small groups, or small communities can pull off. Getting us off of fossil fuels and onto alternative sources (whether the sources are wind, solar, nuclear, whatever) needs to be done on scales much larger than grass-roots projects can pull off.


Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Bluffton University
1 University Drive
Bluffton, OH 45817
419.358.3270
edmiston@bluffton.edu