Salient White Elephant

April 10, 2009

Wind Turbine Energy Storage and Highly Distributed Renewables

Filed under: Brash Environmental Commentary — Salient White Elephant @ 9:58 am

According to Wikipedia, energy storage mediums are matter that store some form of energy. The need for more diverse, stable, and clean sources of energy has engaged scientists and engineers around the world in a mad race to be the first to develop a reliable, economical, and safe means of energy storage. The team that first attains this goal will certainly be knighted, earning a place right alongside of no less than Sir Elton John himself, and will also be the envy of tech junkies like me from Singapore to New York City. I wonder if they’ll do better than the Persian engineers of the 9th century? They invented one of the greatest energy storage mediums of all time you know. It’s called “flour”.

Though Webster does not describe flour as a form of energy storage, it does have some remarkable properties that suit this application.We go to a lot of expense and trouble to raise the voltage of electricity to a level that could melt an aircraft carrier in order to avoid losing too much of its energy while transmitting it over a distance of just 30 miles. But once stored in the form of flour, energy is delivered to its destination with an efficiency that is not often witnessed in the world of science – a whopsnoggling 100%! (Provided, of course, the cashier doesn’t accidentally poke a hole in the bag while scanning it.)

Of course, these days people that grind grain for a living prefer to do their grinding between the hours of 9 and 5, whether or not the wind is blowing. But one of the houses I grew up in had a solar water heater on the roof, and that thing worked like a charm for years! This medium of energy storage – hot water – seems better than flour because hours of business do not have to be scheduled around it. But is this really the case? If the sun shines so much that you have more hot water than you need, then much of the solar energy that was harvested is wasted. But if you’re in the business of selling flour (rather than just grinding grain for your own personal use) then this problem goes away. Well, we don’t want to waste energy, and we don’t want somebody to have to go to work at 3 am just because the wind started blowing. Is there any other alternative?

I know of only one answer to this question, and it’s pretty lame – install a solar water heater that isn’t large enough to ever produce more hot water than you can use. But doesn’t it seem like there should be some kind of task that is completely automated (doesn’t require human intervention), and whose input and output can be stored indefinitely? Suppose, for example, there is some chemical that is used in some industry in large quantities. Call it X. And suppose X is produced by adding mechanical or electrical energy to chemical Y. Y + energy = X. And finally, suppose X and Y can be stored indefinitely, and that the production process is completely automated. Now a truck hauls Y to the wind farm, and picks up whatever X is available for delivery. Here’s some ideas to give you a general flavor of what I’m talking about here. I don’t have a clue as to whether any of these ideas will work, and some of them are pretty ridiculous, but I’ll go ahead and post them anyway:

  • forcing water through some kind of purification filter to make drinking water (do you really believe they have enough spring water in the world to fill up all those bottles of spring water in all those Walmarts across the country? I don’t. I think it’s just tap water.),
  • oxygenating water,
  • removing CO2 from the atmosphere or putting oxygen into the atmosphere to help make up for deforestation,
  • cleaning polluted water or getting algae out of water,
  • treating sewage,
  • killing bugs that eat crops.

Another angle to this line of thinking involves small wind turbines. Years ago, I made some estimates of the cost per kilowatt hour of various small wind turbine designs. It was really depressing. Small machines do not make good use of assets such as the tower they are perched on, the power electronics that interface them to the electricity grid, and so forth. I guess this is to be expected. Even people that don’t understand a thing about business know of the concept of economies of scale, if only because their aunt’s small town florist shop was driven out of business by Walmart. And it’s not surprising that the manufacturers of utility scale wind machines are in a race to extract the economic benefits of scale by designing larger and larger turbines. But the idea of energy storage seems to suggest different applications for small wind turbines. There are lots of ads these days on the web for small rooftop wind turbines. It’s interests me because it seems to say that if I can’t provide a good return on investing in an 80 foot lattice tower for your backyard, then maybe I should stop trying to be a utility scale giant and start trying to be what I am better suited for – energy storage. The use of a small turbine to heat water, for example, has a number of natural advantages. It even has some advantages over the utility scale monster turbine! For one thing, all of the costs of distributing the electricity generated by the utility scale wind machine completely disappear in the roof top water heater application! You could even go as far as to say that if enough people had these small machines, it would reduce the utility company’s cost of transmitting electricity, regardless of how it was generated. This is true because if a lot of people have these devices, and if these people live in lots of different places, then the probability that the wind will not be blowing in any of these places is lower than the probability that the local coal-fired power plant will be down for equipment failure or for maintenance. This means the utility company doesn’t have to have as many megawatts of capacity standing by in case all of you super-techie bloggers who follow me suddenly decide to shower all at the same time. (I’ve written many angry letters to my local utility explaining that the probability of this event is smaller than the probability that Elvis is alive and well on the moon, but they are too snooty to answer my valid concerns.) Returning to the problem of the small turbine tower, I now wonder if I didn’t fool myself with the cost estimates I mentioned earlier. Seeing that the small turbine was not providing a good return on investment for its tower, my reaction was to speculate about taller and taller towers. I figured you needed to get the higher energy density at altitude to pay for the tower. But now I wonder if it wouldn’t be better to go in the opposite direction! Just eliminate the tower altogether, mount the machine on the roof of a house, and let its energy be stored in the form of hot water. In this case, the tower is the house. You could say that the cost of the tower is zero because you will pay for the house whether or not you put a turbine on top of it. The same argument applies to any structure, such as a street light pole, whose purpose in life has nothing to do with electricity, but which can nevertheless support a small wind turbine. And I wonder if the same logic could not be applied to the turbine’s electronics. If the cost of synchronizing the turbine’s electricity with the grid is not well leveraged by a small machine, then maybe the answer is to eliminate the electronics altogether, and use an entirely mechanical means of heating water. Actually, the wind turbines of the 70s and 80s also had a dirt simple electrical design. That industry was spawned by the observation that there’s no difference between a simple induction motor and a generator. Use some wind turbine blades to try to make an induction motor turn faster than it wants to go, and voila!… you’re pumping electricity back into the grid! Here’s a company that has a turbine that does just that, and plugs into the wall right next to your microwave!

Jellyfish Wind Turbine

I got the water heating ideas from a post on greenpowertalk.org:

greenpower post about heating water with wind

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