Cryogenics, Superconductivity Play Major Roles in Renewable Energy

Several technology developments demonstrate the importance of cryogenics and superconductivity in the quest for eco-friendly, affordable energy generation and storage. A keynote address and a facility tour at the upcoming ICEC/ICMC conference will highlight two of these developments.

Attendees at ICEC/ICMC will tour the pilot-scale liquid air energy storage (LAES) facility at the Birmingham Center for Cryogenic Energy Storage at the University of Birmingham. Research here contributed to development of the world’s first grid-scale LAES plant, launched in June by Highview Power in Bury, near Manchester UK.

A keynote address by Prof. Ing Tiemo Winkler from the University of Twente on the EcoSwing superconducting wind turbine project will highlight that effort to demonstrate the world’s first superconducting low-cost and lightweight wind turbine drivetrain, demonstrated on a large-scale wind turbine.

In her WomenofGreen blog, Megan Ray Nichols reports that some forecasts predict that 80 percent of the United States’ total power generation will come from renewable sources by the year 2050. She calls for experts in the energy sector to act quickly to accommodate the expected growth over the next two or three decades. She goes on to examine the potential of cryogenic energy storage (CGS).

At the Birmingham Center for Cryogenic Energy Storage (BCCES), which is an ICEC/ICMC tour choice, researchers carry out detailed study for both component and system level performance improvement, validating their work on integration and optimization and providing education and training for undergraduate and postgraduate students and engineers working in the area. The center partners with Highview Power Storage, the Dearman Engine Company, Air Products, Energy Generation and Supply Knowledge Transfer Network, ARUP, and the Energy Technologies Institute.

The center’s website reports that though thermal energy storage has been commonly thought of in terms of heating (relative to ambient), energy can just as well be stored by cooling materials. Cryogenic energy storage systems use off-peak electricity to liquefy air. The cryogenic liquid that is formed is stored in a vessel, then vaporized into a gas during an expansion process, which drives a turbine. This system generates electricity when it is most needed; taking off-peak electricity and using it at peak times will help to solve the ‘wrong-time wrong-place’ energy generation and supply problem.

“Cryogenic liquid can additionally be used to improve the efficiency of diesel generators, routinely used as reserve capacity for the UK national grid. The system is also an efficient method of generating electricity from low-grade waste heat from power stations or industrial processes. Furthermore, CES can be built alongside liquefied natural gas (LNG) terminals to recover cold energy. Unlike some other energy storage technologies, CES does not require scarce resources, and is not limited by geography or geology.

“The early work behind CES was undertaken in the UK by Professor Yulong Ding, the incoming Chamberlain Chair at the University of Birmingham and BCCES director. The center is the first in the UK to have a research facility for energy storage using cryogenic liquids, comprising new laboratories, state of the art equipment, and a major demonstration plant. The new facility, which is housed on the University of Birmingham’s campus, is also connected to the university’s electrical grid, providing a small amount of power to the campus.”

Highview Power’s LAES plant is located at the Pilsworth landfill gas site in Bury. The plant has been developed in partnership with recycling and renewable energy company Viridor.

Gareth Brett, Highview Power CEO, said, “The plant is the only large-scale, true long-duration, locatable energy storage technology available today, at acceptable cost. The adoption of LAES technology is now underway, and discussions are progressing with utilities around the world who see the opportunity for LAES to support the transition to a low-carbon world.”

Highview says, “Demand response aggregator KiWi Power will draw energy from the LAES plant to power about 5,000 average-sized homes for around three hours. The plant will demonstrate how LAES can provide a number of reserve, grid balancing and regulation services. Yet the opportunity is far greater: LAES technology can scale to hundreds of megawatts in line with the energy demand of urban areas the size of small towns up to large cities. This means that LAES plants could easily store enough clean electricity generated by a local windfarm to power a town like Bury (around 100,000 homes) for many days, not just a few hours.

“LAES technology makes use of a freely available resource, the air, which is stored as a liquid and then converted back to a gas, involving an expansion process that releases stored energy, and this drives a turbine to generate electricity. In addition to providing energy storage, the LAES plant at Bury converts waste heat to power using heat from the on-site landfill gas engines.

“No exotic metals or harmful chemicals are involved and the process does not release any carbon emissions. The plant comprises mostly of steel, which has a lifespan of between 30 to 40 years, in comparison with 10 years for batteries. At the end of life, a LAES plant can be decommissioned and the steel recycled. LAES plants can be located at the point of demand, which makes them highly flexible and able to supply energy to help urban areas keep the lights on.”

By March 2019, Ecoswing's 3.6-megawatt superconducting generator is expected to be installed in an Envision turbine like this one in Denmark. Image: Envision

By March 2019, Ecoswing's 3.6-megawatt superconducting generator is expected to be installed in an Envision turbine like this one in Denmark. Image: Envision

In an article in the IEEE Spectrum, Samuel K. Moore presents an in-depth report entitled, “The Troubled Quest for the Superconducting Wind Turbine: To keep offshore wind turbines light, engineers look beyond superconductors to a new permanent magnet tech.” He reports that the market is calling for ever bigger machines, posing huge challenges. He cites a European Union project, InnWind, that calculated that “if a 20 mw wind turbine were to be built with today’s technology, its nacelle alone would weigh nearly 1,100 metric tons—the mass of 11 blue whales!”

Moore notes: “To remove hundreds of tons from the mass of a machine made of magnets, gears, iron cores, and kilometers of copper winding, the solution brought forward is to exchange the magnets and maybe even the copper winding for coils of superconductors. However, he points out that years-long multinational research efforts have recently concluded that, while feasible, building such a turbine would be a monumental tech challenge.” And complicating things even further, permanent magnets are getting “better and cheaper.”

Among the fixes being proposed is direct drive, which requires no gearbox, with the stator surrounding the rotor and containing coils of copper wire, with voltage induced by the rotor’s magnetic field. Superconductors can reduce weight by replacing the direct drive’s permanent magnets with lighter electromagnets made from coils of superconducting wire. Superconductors using yttrium barium copper oxide (YBCO) use liquid nitrogen to provide high current density. A newer superconductor is being tried, magnesium diboride, MgB2, which is much less expensive than YBCO. However, it only becomes superconducting below 40 K and it is difficult to work with. Another new concept is the magnetic pseudodirect drive (PDD) a magnetic gearing system in development at Magnomatics in Sheffield UK, which is extremely efficient, smaller and requires less copper winding than existing technology.

Another EU project, EcoSwing, is attempting to prove that superconducting generators can compete at more modest scales. It plans to demonstrate the world’s first superconducting low-cost and lightweight wind turbine drivetrain, mounted on a large-scale wind turbine at Envision’s site in Thybor0n in western Denmark. The consortium aims to “design, develop and manufacture a full-scale multi-megawatt direct-drive superconducting (HTS) wind generator including dedicated power converter suitable for current mass mainstream markets.” They plan to prove that “this drivetrain is cost competitive to direct-drive permanent magnet generators and geared drivetrains in series production.” They will “develop and manufacture a cost-efficient cryogenics package that can be maintained atop a wind turbine by regular service people, as well as a low-cost and maintenance-friendly HTS coil package based on second generation wire.”

The Envision turbine is designed based on two blades and a partial pitch, generating power similar to conventional three bladed turbines. It is designed to stabilize the rotor in a nearby horizontal by splitting the aerodynamic loads over the rotor plane.

The consortium members and contributors to the project:
– Envision Energy (Denmark) ApS will coordinate the project and provide the test site.
– ECO 5 GmbH will provide the core design.
– Jeumont Electric SAS will utilize its experience in all types of rotating machines to manufacture the stator.
– Delta Energy Systems GmbH will contribute a high quality power converter and communication and protection electronics.
– THEVA Dünnschichttechnik GmbH will deliver superconductive wire and will process into coils.
– Sumitomo Cryogenics of Europe, Ltd will supply the cryogenic equipment.
– DNV GL Renewables Certification will handle pre-certification issues.
– University of Twente will assemble the superconductive rotor. Dr. Ing Tiemo Windler witll give a plenary talk on EcoSing at ICEC/ICMC.
– Fraunhofer Institute for Wind Energy and Energy System Technology (IWES) will run a ground-based test prior to installation on the Envision wind turbine. ■