Wagner Power Tools

Water or Rocks: What's the Secret Ingredient for Energy Storage?

One group likes water and air. The other prefers heat and earth.

It sounds like a panel that Aristotle might have moderated 2,500 years ago, but actually it marks the difference between two different approaches in modular compressed air energy storage .

SustainX , a well-funded spin-out from Dartmouth College, has come up with a modular energy storage system that relies on water to prepare a mass of compressed air that can later be delivered to a turbine. A 40-kilowatt prototype exists, and in 2012, a 1-megawatt system for AES should be ready.

LightSail , a somewhat secretive startup funded by Khosla Ventures, is taking a similar approach.

England’s Isentropic Energy compresses gases for turbines too, but instead of water, the active ingredients are two gravel-filled tanks:  a cold one with rocks at minus 160 degrees Celsius and a hot one with rocks at 500 degrees Celsius.

In Isentropic’s system, the gas only gets compressed to around 174 psi, but it radically changes temperature. When it comes out, it is at a high pressure and temperature, said CEO Mark Wagner.

In the SustainX and LightSail systems, the gas stays at close to room temperature throughout the cycle, but it gets compressed to 3,000 psi so it comes out at an extremely high pressure.

Who’s right? Utilities will ultimately have to determine that through rigorous testing, but here are the basic differences. Compressed air remains far cheaper than batteries or other means for storing energy, according to EPRI and others. Modular units like these have an advantage over geologically-based storage in that they can be made in different sizes and be placed virtually anywhere on the globe. (General Compression, which just raised $54.5 million, concentrates on geological compressed air storage that uses wind turbines to compress air. So it's mechanical compression, but different in its market approach than these three.)

SustainX. The key intellectual property behind the company is a proprietary compression/expansion motor powered by a hydraulic transmission compresses the air.

The transmission functions essentially the same way as a portable hydroelectric dam: a large volume of water with the help of gravity is harnessed perform mechanical work. Dax Kepshire, co-founder and general manager, wouldn’t describe it much beyond that, but agreed loosely with the hydroelectric analogy.

Wagner Power Products 513040 PaintEater Deal

Reconditioned Power Tools : Wagner Power Products 513040 PaintEater Features Power rotary paint remover and surface-prep tool with replaceable 4-1/2-inch disc Removes paint chips; feathers paint edges; abrades surfaces Retractable, ergonomic handle for one- and two-hand use; great for ladder work Multiple ergonomic hand-holds to minimize fatigue and provide safety on a ladder Weighs 4 under pounds

I had two quotes to paint my 3,000 sq. ft. ranch house: ,000 and ,000. The main reason was a the labor involved in scraping and sanding and the thirty windows. The house was in bad shape.

Not one to easily depart with 5 grand, I decided to paint the thing myself. This was the first tool I bought and I have to say it has payed for itself ten times over. It took an entire week of sanding with the machine and unlike others it performed flawlessly. I went through three disks so you may want to pick up a disk or two depending on how big your project is.

I removed the gray plastic shield surrounding the disk. Simply squeeze it and it pops right off. The reason was I couldn’t get the machine close enough to those tight spots and it was blocking my view. Plus, I was wearing safety goggles and a respirator (a must have unless you like lung cancer, very fine dust particles) so flying chips weren’t a problem.

You can use the machine to feather…

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Works good right out of the box. Died after the first 3 hours. Replaced it. 2nd one died as well. Was working fine, no overheating etc. Shut it off to move the ladder. Tried to turn it back on and nothing. Both units had the same symptoms. Too much money for a product with such a short lifetime and they obviously have a manufacturing defect. You can expect to see a lot of these in discount “refurb” catalogs.

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