New solar heat technology could produce cheaper renewable energy
An important technological innovation developed by a team at Purdue University could lead to a significant improvement in the process of green electricity taking advantage of the sun’s heat.
Kenneth Sandhage, Purdue’s Reilly Professor of Materials Engineering, explained why this discovery could be extremely relevant for the renewable energy sector and the future of implementation of sustainable energies:
“Storing solar energy as heat can already be cheaper than storing energy via batteries, so the next step is reducing the cost of generating electricity from the sun’s heat with the added benefit of zero greenhouse gas emissions.”
In the US alone fossil fuel generated electricity still represents 60% of the overall energy utilized, and this new process could make heat-to-electricity systems as cost-effective as the fossil fuel ones.
The research was published in the journal Nature and was conducted by Purdue University in collaboration with the Georgia Institute of Technology, the University of Wisconsin-Madison and Oak Ridge National Laboratory.
How solar heat Energy works
Solar power is mostly known for the energy generated by photovoltaic panels that can be placed on the rooftop of buildings or organized in large energy farms. However, sunlight can also be used by concentrated power plans to generate heat energy.
This technology uses solar energy and transforms it into electricity by using lenses and mirrors to apply as much light as possible into small areas and then transfer the heat generated by this process to molten salt.
A supercritical carbon dioxide then receives the heat from the molten salt and, while expanding, it spins a turbine which produces electricity.
At the moment, the heat exchangers that act as a conductor between the fluid and the molten salt are mostly made of nickel-based alloys and stainless steel that still don’t offer best performances at elevated temperature and pressure required by the process.
Researchers soon realised that if they wanted to make this energy more efficient and produce more electricity with the same amount of heat, the key was to adopt materials that could withstand hotter engines.
A new, innovative composite material
Determined to follow this approach, the team lead by Professor Sandgae, in collaboration with Asegun Harry at MIT, decided to develop composite materials that could resist high heat and pressure like the one used for solid-fuel rocket nozzles.
After some research, the team realized that a ceramic-metal composite made of zirconium carbide and metal tungsten was offering promising results.
Additional corrosion and mechanical tests showed how this composite could support more efficiently the supercritical carbon dioxide at higher pressure and temperature allowing the process to produce more electricity and be more efficient compared with the heat exchangers currently used
The research team also conducted an economic analysis on the composite material and came to the conclusion that if scaled-up the manufacturing process of this new heat exchangers could be even more cost-effective than the current stainless steel or nickel alloy-based ones currently used.
The future of the new technology looks very positive.
The team has now submitted a patent application and U.S. Department of energy as has recently awarded more funding for the scaling up development of this technology.
“Ultimately, with continued development, this technology would allow for large-scale penetration of renewable solar energy into the electricity grid”, Sandhage said. “This would mean dramatic reductions in human-made carbon dioxide emissions from electricity production”.