Remember Rube Goldberg?

Rube Goldberg invented ridiculously complex machines to perform simple, ordinary tasks.

His invention that has a napkin automatically wipe your chin was a classic.

There is an annual contest at Purdue University where colleges compete in the Rube Goldberg Machine Contest.

They should look no further than the machinations involved with energy storage.

Energy storage is the Holy Grail for renewables such as wind, which is unreliable and produces electricity when it isn’t needed.

The situation is currently so absurd that owners of wind farms are willing to pay to have the electricity taken off their hands so they can collect the “tax credit” from the government for the electricity they produce that isn’t needed. This is the so-called “negative price” for wind generated electricity.

Storing the electricity that’s produced when it isn’t needed might make renewables more palatable, though still not economical.

Here are typical, generic proposals.

  • Use the excess electricity to produce natural gas and hydrogen and then use these combustible gasses to power a gas turbine to produce electricity when it’s needed.
  • Use the excess electricity to run compressors to produce compressed air, which is then stored until needed to generate electricity.
  • Utilize pumped storage, where water is pumped uphill to a reservoir and then released when it’s needed to run water turbines to generate electricity.

This is where the fun begins.

Let’s look at variants of these proposals.

One proposal is to use huge balloons mounted underwater, on the sea-bed, where the water pressure minimizes the pressure differential to allow using very thin plastic balloons for storing compressed air. The excess electricity from a wind farm would run a compressor where the compressed air would be piped to the underwater storage balloons. When needed, the compressed air would be released from the balloons to run the compressor in reverse to generate electricity. No mention was made as to whether sharks, crabs or swordfish might have an effect on the balloons.

Another proposal is to produce ice from excess wind-generated electricity in some 6,500 units at around 2,000 locations in Southern California. During the day, air would be blown over or through ice-chips to provide cool air without having to fully utilize air conditioning units, thereby cutting peak load.

Another proposal is to drill a 15-foot diameter borehole straight down into the ground for thousands of feet, then filling the hole with water. A huge concrete weight, similar to a piston, would be placed on top of the water. When electricity was needed, the concrete weight would be released and force the water down and out and then up a parallel smaller borehole. As the water is forced up the second narrow borehole, it would drive a turbine to generate electricity. After passing through the turbine, the water would be returned to the large borehole above the concrete weight.

During periods when wind turbines generate excess electricity, the excess electricity would be used to run a motor that would lift the concrete “piston” to the top of the borehole, thereby forcing the water that’s over the concrete “piston” back down the narrow borehole and into the large borehole below the concrete weight. (The system would be a closed loop and continuously use the same water.) The system would then be ready to have the concrete “piston” released to repeat the cycle for generating electricity.

The borehole concept is called “underground pumped storage”.

Other, similar Rube Goldberg approaches have been suggested for storing the excess, unneeded electricity produced by wind farms.

While all these approaches may be technically feasible, it still begs the question, why go to the added expense? Energy is lost every time it is converted from one form to another.

Why try to turn a sow’s ear into a purse?

A fundamental rule in engineering is to keep systems simple and easy to maintain – the fewer the moving parts the better. These Rube Goldberg ideas violate that principle. All these ideas also complicate maintaining the grid in a stable, efficient manner.

Wind-generated electricity is expensive and unreliable, while electricity generated from natural gas and coal is cheap and can be counted on as predicted for use on the grid.

All these proposals for “storing” energy should compete at next year’s Purdue University, Rube Goldberg Machine Contest. One of them is bound to be the winner.

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Additional TSAugust web sites:

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0 thoughts on “Remember Rube Goldberg?

  1. Donn,

    I noticed that Greentech media has a few discussions on energy storage this week that you might find of interest-

    1) Utility-Scale Storage: Moving From Trials to the Real World
    Any day now or not for a decade, depending on whom you ask

    2) BrightSource Adds Storage to Its Solar Thermal CSP
    IPO aspirant enhances its utility-scale concentrating solar power generation technology with crucial storage component-

    As your post notes most RE sources of power are not dispatchable. Adding in some storage will make these sources of power more like traditional electrical energy generation (where levilized costs are a reasonable estimate of what it costs to get power to the folks that want to use it- when they want it). In CA, we have the 33%RES in place so we are going to have more intermittent sources of RE (that are also not dispatchable) so energy storage does seem like a way to reduce the risk of not having power when you want it. The RES time of delivery price factors give the RE providers an economic incentive to deliver at peak times as noted here-
    For PG&E energy supplied during super peak in the summer has a factor of 2.2049. Interesting SCE’s super peak price has a factor of 3.13.

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