Clean Power molten-glass

Published on April 8th, 2012 | by Susan Kraemer


Halotechnics – Molten Glass Thermal Storage Could Mean 6 Cent Solar

April 8th, 2012 by  


Halotechnics, an early-stage solar-thermal startup and ARPA-E recipient, has developed two radical new materials for storing solar heat energy, using new kinds of salts and even a new kind of glass.

These allow much higher temperatures than have been used to date to store the heat in solar thermal power plants so they can produce power at night. This will greatly improve the efficiency and lower the costs for solar thermal power.

This is a first. While practically every other day we hear about efficiency innovations that will lower the costs of PV solar, this is a major innovation for solar thermal.

Unlike solar PV which makes electricity directly, solar thermal makes heat that runs turbines driven by steam. So, unlike solar PV, it has the potential for night time solar generation, because thermal is steam-turbine-driven energy, so it can store the days heat in molten salt solutions for tapping later as needed. This evening peak hours flexibility is its advantage over (now) cheaper PV.

Improving energy storage would reduce the cost per kilowatt-hour of the electricity produced by a solar-thermal plant, because the turbines and generators can produce power for more hours, more cheaply, if the temperatures can be kept high enough. Being able to store energy at higher temperatures is the key to cutting the costs of solar thermal, and that is what Halotechnics has pioneered.

“To hit that six-cent goal, or get close to it, you have to go to a higher-temperature system,” says Mark Mehos, manager of the National Renewable Energy Laboratory’s  Concentrated Solar Power program, in Golden, Colorado. “The systems that are commercial today are limited to about 565 °C—that’s the molten salt tower plants,” says Mehos. “The tower and optics themselves can hit higher temperatures, but you’re limited by the salt temperature right now.”

Halotechnics was a spin-out from a chemical screening company Symyx (now a part of Accelrys).  And that is key to its success, because to find the perfect material to allow the heat to be raised in solar energy storage, Halotechnics was able to comb through nearly 18,000 mixtures using this type of high-throughput chemical screening process. It was an ARPA-E grant recipient ($3.3 million) last year as a result.

“Without an amazing ability to screen samples, it’s an intractable problem. That’s what we’re trying to do with our high-throughput technique,” says Justin Raade, CEO of Halotechnics.

The materials they have devised, which include new mixtures of salts as well as new forms of molten glass materials, could be key to making solar-thermal power plants cheap and reliable enough to compete with fossil fuels on a large scale.

The U.S. Department of Energy’s SunShot Initiative has the goal of reducing solar costs to six cents per kilowatt-hour. Last year it gave the start-up a $1 million NREL subcontract with the goal of developing thermal energy storage that could operate at 700°C.

Halotechnics not only met but surpassed that 700°C goal: one of their new molten glass materials can work at temperatures up to 1,200 °C, says NREL’s Mehos.

According to MIT:

“This is a form of glass that melts at 400 °C (typical window glass melts at about 600 °C) and can operate up to 1,200 °C. It could be used to heat up air to drive a gas turbine, with the leftover heat used to drive a steam turbine, much as is done in a natural-gas combined-cycle plant. Such a system could be about 52 percent efficient using existing turbine designs. (Natural-gas combined-cycle plants can reach 60 percent efficiency, but the natural gas burns at temperatures higher than 1,200 °C.)”

Operating at such high temperatures, however, will bring engineering challenges, including finding relatively inexpensive materials to contain the extremely hot molten glass. Commercialization of this technology could be many years away.

Or perhaps its time to go searching through anouther 18,000 combos to devise that perfect material to build the container!

Check out our new 93-page EV report, based on over 2,000 surveys collected from EV drivers in 49 of 50 US states, 26 European countries, and 9 Canadian provinces.

Tags: , , , , ,

About the Author

writes at CleanTechnica, CSP-Today and Renewable Energy World.  She has also been published at Wind Energy Update, Solar Plaza, Earthtechling PV-Insider , and GreenProphet, Ecoseed, NRDC OnEarth, MatterNetwork, Celsius, EnergyNow, and Scientific American. As a former serial entrepreneur in product design, Susan brings an innovator's perspective on inventing a carbon-constrained civilization: If necessity is the mother of invention, solving climate change is the mother of all necessities! As a lover of history and sci-fi, she enjoys chronicling the strange future we are creating in these interesting times.    Follow Susan on Twitter @dotcommodity.

  • Gary Tulie

    One concern if using such high temperatures to run an air turbine is the generation of NOx. which is a powerful greenhouse gas and a serious pollutant able to damage plants through acid rain. A good catalytic converter or other system to remove NOx would be essential at this temperature.

  • Desalt seawater can also reduce a cost and inhance the yeld of CSP, because in MENA area the fresh water is as necessary as electric power!

  • Deasalt seawater can also reduce a cost and inhance the yeld of CSP, because in MENA area the fresh water is as necessary as electric power!

  • Donald Cochran

    I would like to add a further comment about the hot glass concept: because I have been working on my own project of an All Alternate Energy Fuels Engine since my son went to and returned from Iraq, I have been dealing with the issues of 1200 to 1600 degrees F containment. It is not fun, not even NASA can provide lubricants at those temperatures. So my reply to 1200 degrees being not a problem is true. I can put together a unit that will deal well with the hot glass if temperature is the only issue. Who do I contact? Contact me:
    Don Cochran
    Learium Development Technologies

    • Gary Tulie

      The glass is capable of of storing heat at up to 1200 centigrade, not 1200 Fahrenheit. This is nearly 2200 Fahrenheit and not nearly so easy to manage.

  • Donald Cochran

    If 1200 F is the only problem you have the whole thing is a slam dunk, let the light shine in.

  • Awesome…I hope this succeeds. Good Luck!

  • In a grid where the price of electricity frequently drops towards zero, say a grid with lots of wind and/or solar capacity, thermal storage could be used with electrical resistance heating instead of concentrating solar or other methods. Such a facility would have the advantage of potentially being quite small. If such a facility was built where I am now it could take advantage of low early morning and weekend electricity prices that often result from our wind power capacity and sell it during the daytime peak or evening peak.

    • jim

      Uhh, the round-trip efficiency of thermal storage would be around 30% best case with current thermoelectric conversion technologies (steam turbines). Even though they’re much more expensive on a capacity basis, batteries, with more like 70%+ round trip efficiency (you get back 0.7kWh for every 1kWh you put in), are making entry into the rate-arbitrage markets you mention now.

      • Gary Tulie

        This would be the case if you were using electricity to generate the heat, however in this case, you are generating the heat anyway and the thermal storage only defers converting it to electricity. The efficiency penalty of storage is therefore much lower.

  • Solar heat is often overlooked, but we need to do this. The materials challenge with solar PV is toxicity and whether you can recycle it. Solar heat requires more constant sun, but some places like Nevada or the deserts of the world can be used for this more efficient form of solar power.


    • Dihydrogen_Monoxide

      Not to mention that CSP can provide “base-load” power. Eliminating one of the objections to using renewable energy.

    • Yes, it is a big part of the first of the Desertec solar projects because of its great suitability to desert solar

Back to Top ↑