Abengoa, designer of novel concentrating solar power towers, is a participant in several new ARPA-E funded projects for storing thermal energy. Credit: Abengoa

Last week Eileen reported on ARPA-E’s new awards in rare-earth alternative technologies. This week I thought I would take a look at APRA-E’s $37.3 million initiative to find a disruptive thermal storage technology(ies), an effort cleverly called HEATS (high energy advanced thermal storage), all of which seem to have a novel material at their cores.

General speaking, the awards went to R&D groups working in three arenas: Large and medium-scale (utility-scale) storage systems, “thermal fuels,” and vehicular support systems.

In regard to large-scale awards, the quest is to find out if thermal storage could be used as a massive controllable and distributed load for grid stabilization. The technologies include supercritical fluids, molten salts, molten glass, metal hydrides and phase change materials.

The vehicular systems are mostly aimed at developing special “hot-cold batteries” for interior climate control to extend the mileage of an electric vehicle’s main battery pack. Some of the materials include PCMs, solid state thermal energy conversion materials and electrical metal-organic framework

Utility-scale HEATS

Navitasmax: Navitasmax, Cornell and Harvard Universities, Nano Terra and Barber-Nichols are getting $812,000 for a project, targeted at concentrating solar and nuclear applications, which involves evaluation of simple and complex supercritical fluids. They hope to show these fluids can be “tuned” to have very high heat capacity, which will provide the potential of developing low cost and efficient thermal storage.

Abengoa Solar: Abengoa Solar Inc. is getting $3.6 million to develop a new type of large-scale CSP conversion (salt?) tower and a novel thermal energy storage technology, which they predict can save 30 percent over parabolic mirror molten-salt system costs, along with higher performance. Abengoa has been developing projects based on new tower architecture, superheated steam and salt storage components

Halotechnics: This is a $3.3 million project by Pratt & Whitney Rocketdyne based on a low melting-point molten glass thermal storage system. Besides using abundant raw materials, the group predicts it can reduce costs by a factor of ten. It’s aimed at CSP and nuclear applications. The company, heretofore, has focused on molten salt technologies, but CEO Justin Raade says on its website, “We’ve been thrilled by the discoveries we’ve made with our molten salts and are very excited to explore the use of molten glass to reach even higher temperatures for more efficient energy storage.” It will optimize the material in order to develop a complete system to pump, heat, store and discharge the molten glass.

Pacific Northwest National Lab: PNNL’s Energy Materials Group and University of Utah will use $712,500 for a reversible high-temperature metal hydride thermal storage system exploiting recent breakthroughs. In particular, the team will try to demonstrate the desired cycle life in a reversible hydride and demonstrate an order-of-magnitude increase in storage density compared to existing systems. PNNL’s website says, “The team will first develop a metal hydride with a suitably long lifetime. If successful, they will then create a small prototype system.”

University of South Florida: USF and SunBorne Energy (a company that has tended to focus on India’s energy needs) have $2.5 million to develop a low-cost, industrially scalable system based on high-temperature phase change materials. They will use an electroless encapsulation technique (pdf) to enhance the heat transfer to overcome the low thermal conductivity of common PCMs. The proposed low-cost (75 percent reduction) system will operate at high temperatures with a small footprint. The idea is to prepare macrocapsules, from porous pellets of low-cost PCMs (salts, eutectics, metal alloys, polymers) and then encapsulate the pellets in high temperature material. Convective heat transfer would occur by submerging the PCM capsules in a liquid.

MIT: Like the project above, MIT and Boston College will use phase-change materials for high-temperature thermal energy storage. The team’s metallic composites-based PCMs will have high phase-change temperatures, high thermal conductivity values, long lifetime and low cost. The team intends to use its characterization and modeling skills to optimize the properties of these materials.

Thermal Fuels

University of Florida: With nearly $3 million, UF hopes to demonstrate a “thermal fuel,” a thermochemical fuel production system that uses a low-pressure, magnetically stabilized, nonvolatile iron oxide looping process. UF’s system uses a new dual-cavity, high-temperature chemical reactor that converts CSP to syngas with a process that uses water and recycled CO2 as the sole feedstock.

University of Minnesota: UM, along with Caltech and Abengoa Solar Inc, says it can develop technology for a solar thermochemical reactor to make fuel production more efficient. With $3.6 million, the team is ambitiously aiming for solar-to-fuel conversion efficiencies of more than 10 percent.

Vehicular Storage

University of Utah: The university, with HRL and General Motors Global R&D will use $2.7 million to demonstrate a high-density thermal battery based on metal hydrides. The thermal battery will be used for warm and cold climate control to provide heating and cooling to electric vehicles without draining the EV’s electric battery.

PNNL: PNNL’s Energy and Environment Directorate, in partnership with the University of South Florida, will be pioneering an electric-powered adsorption heat pump for EVs. Researchers will use $813,000 to develop new metal-organic frameworks with larger sorption capacities and can be regenerated electrically. The PNNL website says a heat pump based on electrical metal-organic framework material the size of a 2-liter bottle could theoretically handle the heating and cooling needs of an electric vehicle with far less impact on driving distance.

TREATS: Sheetak Inc, with partner Delphi Automotive, received one of the largest awards, nearly $4,7 million. TREATS, thermoelectric reactors for efficient automotive thermal storage, would provide EVs with a new HVAC system option that can store the energy required for heating and cooling. Sheetak has a solid state thermoelectric energy converters to recharge a dedicated hot-cold battery. The converter can also eliminate the need for an EV’s traditional compressor and heater.

University of Texas at Austin: UTA and Sinoev will use $2.5 million for R&D for a hot-cold battery. They will demonstrate a high-energy density, low-cost system based on new composite PCMs with an energy density they say is two- to three-times above the state-of-the-art PCMs for low-temperature applications.

United Technologies Research Center: UTRC and Ricardo Inc will use a $2.7 million award to demonstrate a “hybrid vapor compression adsorption” hot-cold battery system based on a metal salt that has a high mass and volumetric capacity tailored to the refrigerant.

MIT: With the University of Texas at Austin, UCLA, Ford and $2.7 million, MIT hopes to demonstrate what it calls a thermo-adsorptive battery climate control system. This hot-cold battery would eliminate the vapor compression cycle, and if it works with EVs, it may be applicable to residential and commercial buildings displacing electricity consumption during peak demand times.

MIT: Based on its HybriSol Hybrid nanomaterials, MIT will use $3 million to demonstrate the use of nanostructures for high-energy-density thermal energy storage device. The HybriSol device would be rechargeable and transportable.