‘Hydricity’ concept uses solar energy to produce power round-the-clock… really?
Researchers are proposing a new “hydricity” concept aimed at creating a sustainable economy by not only generating electricity with solar energy but also producing and storing hydrogen from superheated water for round-the-clock power production.
“The proposed hydricity concept represents a potential breakthrough solution for continuous and efficient power generation,” said Rakesh Agrawal, Purdue University’s Winthrop E. Stone Distinguished Professor in the School of Chemical Engineering.
“The concept provides an exciting opportunity to envision and create a sustainable economy to meet all the human needs including food, chemicals, transportation, heating and electricity.”
Hydrogen can be combined with carbon from agricultural biomass to produce fuel, fertilizer and other products.
“If you can borrow carbon from sustainably available biomass you can produce anything: electricity, chemicals, heating, food and fuel,” Agrawal said.
Hydricity uses solar concentrators to focus sunlight, producing high temperatures and superheating water to operate a series of electricity-generating steam turbines and reactors for splitting water into hydrogen and oxygen. The hydrogen would be stored for use overnight to superheat water and run the steam turbines, or it could be used for other applications, producing zero greenhouse-gas emissions.
“Traditionally electricity production and hydrogen production have been studied in isolation, and what we have done is synergistically integrate these processes while also improving them,” Agrawal said.
The paper was authored by Gençer; former chemical engineering graduate student Dharik S. Mallapragada; Francois Marechal, a professor and chemical process engineer from Ecole Polytechnique Federale de Lausanne in Switzerland; Mohit Tawarmalani, a professor and Allison and Nancy Schleicher Chair of Management at Purdue’s Krannert School of Management; and Agrawal.
In superheating, water is heated well beyond its boiling point – in this case from 1,000 to 1,300 degrees Celsius – producing high-temperature steam to run turbines and also to operate solar reactors to split the water into hydrogen and oxygen.
“In the round-the-clock process we produce hydrogen and electricity during daylight, store hydrogen and oxygen, and then when solar energy is not available we use hydrogen to produce electricity using a turbine-based hydrogen-power cycle,” Tawarmalani said.
“Because we could operate around the clock, the steam turbines run continuously and shutdowns and restarts are not required. Furthermore, our combined process is more efficient than the standalone process that produces electricity and the one that produces and stores hydrogen.”
The system has been simulated using models, but there has been no experimental component to the research.
“The overall sun-to-electricity efficiency of the hydricity process, averaged over a 24-hour cycle, is shown to approach 35 percent, which is nearly the efficiency attained by using the best photovoltaic cells along with batteries,” Gençer said.
“In comparison, our proposed process stores energy thermo-chemically more efficiently than conventional energy-storage systems, the co-produced hydrogen has alternate uses in the transportation-chemical-petrochemical industries, and unlike batteries, the stored energy does not discharge over time and the storage medium does not degrade with repeated uses.”
Agrawal said, “The concept combines processes already developed by other researchers while also improving on these existing processes. The daytime and night-time systems would use much of the same equipment, allowing them to segue seamlessly, representing an advantage over other battery-based solar technologies.”
Aside from the lab:
Not to be a downer or anything, but it would seem to this humble engineer that using all that energy to superheat water is inefficient. Why would we need to superheat water to the point that we are creating hydrogen when we could do something far more simplistic. Instead I would propose to use the extra solar energy or even dedicated solar energy to pump water into a giant tank (Think city sided tank that would slowly raise and lower as it is filled and emptied with parks or even buildings on top).
Then we could just use hydroelectric power to create the extra needed energy at night and repeat the storage process. The best part is you can have unlimited storage for an indefinite amount of time without energy loss like you would see from a long term battery storage. Eventually, you wouldn’t even need to worry about not getting enough solar energy during the winter months because you could store so much potential energy that you could make up the deficit when there are times of heavy rain, snow, or clouds.
Furthermore, the water from rain and snow can be collected in these tanks which would help reduce flooding. So while it might not be much in the grand scheme, it still adds to the power supply allowing us to use some of the energy that goes into making rainfall for our own power needs. So what’s the catch? Well given the amount of hydroelectric power that is produced and its reliability the only catch is that this wouldn’t be the city of the future, this could be the city of today. Let’s face it, hydrogen powered vehicles are like zeppelins, they’re just not a good idea.
But that’s just me, maybe there is some process that means hydropower is not as efficient as turning water into hydrogen, or maybe it just isn’t as sexy. Heck, maybe I’m just complaining and there is some problem with my idea, but it seems to me that we are overthinking this a bit much…
Emre Gencer, Dharik S. Mallapragada, Francois Marechal, Mohit Tawarmalani (2015). Round-the-clock power supply and a sustainable economy via synergistic integration of solar thermal power and hydrogen processes Proceedings of the natural sciences academy of the United States of America : http://www.pnas.org/content/early/2015/12/09/1513488112.abstract