Researchers at the University of Arkansas in the US set out to invent an efficient and economical energy storage system that would improve the overall efficiency of solar thermal plants. The team has developed a thermocline solar energy storage system that stores absorbed heat at 93.9% efficiency and a material cost of only $0.78 US per kWh.
The University of Arkansas’ invention represents progress from conventional thermal energy storage methods like tanks of molten salt or beds of packed rock. “We are trying to come up with energy storage systems for high temperatures — up to 600 degrees Celsius. We are also trying to use economical materials, like concrete, to store thermal energy,” explains Panneer Selvam, PhD, Professor in the Department of Civil Engineering at the University of Arkansas. “For big solar thermal power plants, this type of energy storage can reduce the overall cost of producing electricity.”
The novel structured thermocline system employs parallel plates of concrete with steel pipes running through them. The steel pipes transfer absorbed heat into the concrete, which holds it until needed. During testing, the thermocline system withstood temperatures up to 600 degrees Celsius and absorbed heat at an efficiency of 93.9%. What are the implications of providing such an inexpensive solar energy storage solution, $0.78 US per kWh? “This is the cost of material alone,” Selvam clarifies. “When you include the other costs, thermal energy storage costs $30 to $34 US per kWh-thermal. This is very low compared to other methods of storing energy. This is why solar thermal energy systems are getting to be attractive.”
The team has done modeling and testing at the University. “Currently molten salt is used in every plant, and we used that fluid to see how our concrete material is able to store the heat and how well it performs in the environment,“ Selvam says, adding that they are “continuously looking into new ideas to improve the technology so that high efficiency and low cost can be achieved.” Testing the thermocline system in a laboratory setting on a smaller scale turned out to be the team’s most difficult task. The researchers are still working on overcoming this challenge.
In the meantime, Selvam is ready to talk business. “If there are power plants that want to implement [our system], we will try to work with them,” the James T. Womble Professor of Computational Mechanics and Nanotechnology Modeling says. Solar thermal power plants are not the only application Selvam envisions for his energy storage system. “With adequate modifications, the system can also be used for heating houses, farm houses, chicken houses, melting ice on a bridge deck etc.”
Selvam is confident his research success will contribute to the growth of the solar energy sector. “This is a viable technology for storing thermal energy. Energy storage is the major challenge at this time. If a reasonable solution is derived from this, producing [solar thermal] energy will be cheaper and reliable.”
Image: Panneer Selvam (center), Micah Hale (left) and Matt Strasser showcase the thermocline energy storage test system; coutesy of the University of Arkansas.
Source: Sandra Henderson, Research Editor, Solar Novus Today