May 2008

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I realize that this post is dead, But I think that there is a relatively easy fix.
the issue is that a chemical battery (gas, storing chemical potential energy, for example) is better than a physics based battery, which would be subject to friction, etc.

we know that water can be separated into oxygen and hydrogen with electricity

we also know that recombining into water inside a fuel cell yields power (don't know how much, doesn't really matter)

if we have massive solar farms constantly making electricity, then using it to divide water, then we recombine it in car fuel cells, we have a transportible way to store energy, with 0 emissions and minimal toxic waste (only what goes into replacing fuel cells over time)


I want a yabba-dabba-do big gravity battery to mount onto my electric car. I could hook the winding line up to trucks on the interstate, let them pull out ahead of me, and disconnect to get all that recovered potential energy! Yee-haw!


Would just say that we value you work I the office-environment in Denmark :-)


Hi Scott:
Colorado has had a system like this for years in near Glenwood Springs. During the night when electricity is cheaper, they pump water to a high reservoir. Then during the day when the electricity is more expensive, they run the water back through turbine/generators. Using excess capacity at night is another way to save the energy (in a virtual sense).

Dan Kennedy

Pumped hydro storage is in use in the Canary islands.

Wind powered pumped hydro storage systems, a means of increasing the penetration of renewable energy in the Canary Islands, by C. Buenoa and J.A. Carta
(disclosure, I work at elsevier)

Also wikipedia has a good page listing known pumped hydro insilations worldwide.



You have stopped being witty. That was the best part of your blog. Lots of people are commentators, but few are witty ones. Sorry, but your blog's sometimes becoming tedious to read!

Anarchy In Your Head

If you're on the grid, any energy your solar panels or windmills or whatever produces beyond what you need feeds the grid and reduces the amount of power needed from other sources throughout the day, thereby saving those other forms of energy for nighttime use. If you want to be off the grid, the batteries are an issue, but otherwise solar power or something else is still very useful and storage is not really a problem. The meters of people with solar panels can potentially run backward during the day making up for energy they took form the grid at night. In some places, if you actually produce more than you consume, you get paid something by the power company for that energy.

Larry S

A pumping power plant exists in Luxembourg, where off peak electricity from the power grid is used to fill a reservoir. During peak electrical use periods, the water in the reservoir is released to power geneerators. See the following link.


Yeah, first post is right. It's widely used in Europe, where there's "cheap" energy during the night (nuclear power stations can't be stopped just for the night) and dams with big lakes. Water is pumped up at nighttime and is used to generate power during daytime.


I can't believe nobody realy answered your Question yet...

So let's try:

say we need to store 2 kWh, that is 7.2 MJ. If we use a storage height of 5m by average, we need 144 tons of Water.
If the reservoir is 1m deep, that is 12mx12m wich is a pretty big swimming pool...

keep up the nice posts!


What about maglev highspeed flywheels? Tech is getting better fast, and looks veeery good. Perfect for home, no way to use it in a car though...


I'd like to point out that long-distance travelling via car will also pretty much require a gas tank (unless you can get enough batteries to not have to stop at all). Otherwise, the length of time it takes for the recharge will make gas fairly necessary. (unless you want to envision a multi-hundred amp circuit at the "filling station", I suppose :).


You can store energy very efficiently with a flywheel rotating in a vacuum.

You can get the energy in using a motor, which can have efficiencies approaching 98%, and when driven by the flywheel, become generators, also about 98% efficient.

One thing that flywheels are good at that motors aren't is dumping a lot of horsepower very quickly, through a mechanical transmission/clutch. This makes them ideal for electric cars.

If your commute doesn't involve a lot of hill-climbing (most don't), then you can use the flywheels for regenerative-braking, storing the kinetic energy of the vehicle at-speed in a flywheel whenever you hit a red light. That same kinetic energy will be available when the light turns green, less a tiny loss incurred during the duration of the red light, generally less than a couple minutes.

You only need about 30HP to maintain a midsized car at 60mph, well-within the range of available electric motors.

BTW, this scheme still requires batteries, it just provides V-8 performance for the consumers who don't like taking half a minute to get up to highway speeds.

Aluminum-air and aluminum-H2O2 batteries tend to have about 20x the energy-density of lead-acid batteries, and we already have a robust infrastructure for making metallic aluminum using hydroelectric generators. Refilling at the service station would involve swapping-out spent standardized batteries for fresh ones, with credit given for remaining metallic aluminum in the old ones.

The pumping water uphill as a means of energy-storage idea isn't new, BTW, it was used as an illustration in my Thermodynamics class back in '76. Not as good as one might hope. There are better ways of storing energy.


You don't use a battery at home.
You sell your excess to the power company: they either sell it to those that need it at the time, or store it much more efficiently than you can at home in pumped storage: effectively reverse hydroelectric where you use surplus power to pump water uphill to a reservoir, then drain it for power as needed.
We did that in the uk to remove cyclical loading from nuclear plants.


Why not just have a block of DU that is spun once at a high velocity, give it a small motor just to maintain the velocity for a while, and let it keep going.
Obviously the block would have to be spun again occasionally.
But, then again I wouldn't have a clue about this stuff.

Lets Go Banners

Interesting idea. It will all come down to supply and demand. I think Solar is the way to go (isn't it obvious with the sun shining everyday? There HAS to be a way we can tap it efficiently.


Actually, large vehicles may be well able to efficiently carry the heavy weight of electric motors and batteries. Seems logical that SUVs, trucks, busses, etc would be ideal platforms for adapting.

(Can't believe I'm writing another comment to this blog -- it's so time consuming and probably nobody cares ... well briefly, hello enterelligencia.)

Are not diesel/electric locomotives (train engines) basically really big "hybrids"

GIVE ME A MOMENT a lifestyle


Cool post


Of course, if the solar cells are in orbit with constant exposure, you don't need a damned battery...

[reply as I don't wade through the comments here]


Space Based Solar Power FTW. :D

"Ultimately, the report estimates, a single kilometer-wide array could collect enough power in one year to rival the energy locked in the world’s oil reserves.

As envisioned, massive orbiting solar arrays, situated to remain in sunlight nearly continuously, will beam multiple megawatts of energy to Earth via microwave beams. The energy will be transmitted to mesh receivers placed over open farmland and in strategic remote locations, then fed into the nation’s electrical grid. The goal: To provide 10 percent of the United States’ base-load power supply by 2050."


"I know, I know, you will point out that even if such systems of energy storage existed, they would be inefficient. It takes more energy to move a rock up a hill than you can capture from the return."

Scott, it is a very basic principle of physics (conservation of energy) that it takes exactly as much energy to move a rock up a hill than you capture as it comes back down. The gravity battery described is probably almost 100% efficient. The problem is that it is inconvenient - requiring a lot of mass and a very strong structure to store any significant amount of energy.

Gustaf Sjoblom

I think that you will find that most scientists if given an infinite timescale will agree that solar power will eventually easily handle all our energy needs. However there are huge disagreements as soon as you limit the timescale.

How many major breakthroughs are we looking at? Two? Five? Fifty-seven?


[So if, for example, solar panels became 1,000 times more efficient and cost you next to nothing, it might not matter if your storage device could only capture half of what you generated.]

Scott, If my Dad had balls, I wouldn't have been adopted. Solar panels cannot become 1000 times more efficient. They're already within 1/3 of their theoretical limits per square foot. Unless you want an Amazon rain forest of super tall solar trees dangling their solar cell leaves down to the ground and crawling with monkeys and halucinogenic frogs, it ain't gonna happen.


Forgot to mention on the EEstor battery claims: Non-toxic and non-explosive.

One more intriguing tech that is available right now is geothermal. From memory, a well is drilled in your backyard to touch earth ~150 feet down where there is a constant 65 degrees F. A pipe circulating water is looped down and back up. Something very similar in size to a standard heat pump is on top and provides a VERY efficient heat exchanger for your AC system. Supposed to pay for itself in a couple of years.

Given that the geo-based temperature differential is available to just about everyone, everywhere, it seems like a Stirling Engine could generate energy from that. Or, maybe this: the inventor of the Super-Soaker has developed a heat-difference *closed system* engine that has claimed 60% efficiency. Now as it turns out that inventor is a nuclear engineer who used to work for JPL until his Super Soaker made him so very rich...


Lockheed Martin just signed an agreement in January with EESTOR, a company that claims to be **commercially producing** (in 2008) a battery with 10X the energy density of lead-acid at 1/10th the weight and volume and costing half as much per stored watt-hour. With virtually unlimited charging/recharging. And charge time limited mainly by the electrical system delivering the charge (as quick as 5 minutes). Canadian car-maker Zenn is an investor (
Sure sounds good.

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