As of 2018, renewable energy sources such as wind and solar have the lowest unsubsidized levelized cost of energy, and grid-scale storage solutions are being aggressively developed and deployed. However, for a carbon-free energy generation paradigm to be realistic, any impediments to scalability must be addressed. In the wind industry, dependence on rare-earth (RE) magnets in direct-drive generators represents a significant roadblock to widespread technology proliferation. Sandia’s Twistact technology is a fundamentally new rotary electrical contact with only rolling metal-to- metal contact that eliminates the need for RE magnets by enabling a wire-wound generator architecture with no efficiency or cost penalties. This report summarizes work funded by an LDRD in FY16—18, in which we advanced the technology readiness level (TRL) of Twistact technology to TRL 5 and proved the viability of a Twistact-based generator for utility-scale, direct-drive wind turbines. We conducted coupon-level tests of rolling metallic contacts and developed a tribological model that predicts operation in either a low-wear or high-wear regime. We also built device-level testing apparatuses and observed operation of full-scale Twistact devices, which corroborated the predictions of the tribological model and demonstrated over 50 million rotation cycles (30-year lifetime in a direct-drive generator). Indeed, the present work demonstrated that Twistact technology has potential to be an enabling technology that eliminates RE magnet dependence in the wind industry. The next logical step is commercialization of Twistact technology (currently at TRL 5) in partnership with a generator original equipment manufacturer that already has an established presence in the wind power industry.

This report is the final deliverable for a techno-economic analysis of the Sandia National Laboratories-developed Twistact rotary electrical conductor. The U.S. Department of Energy Wind Energy Technologies Office supported a team of researchers at Sandia National Laboratories and the National Renewable Energy Laboratory to evaluate the potential of the Twistact technology to serve as a viable replacement to rare-earth materials used in permanent-magnet direct-drive wind turbine generators. This report compares three detailed generator models, two as baseline technologies and a third incorporating the Twistact technology. These models are then used to calculate the levelized cost of energy (LCOE) for three comparable offshore wind plants using the three generator topologies. The National Renewable Energy Laboratorys techno-economic analysis indicates that Twistact technology can be used to design low-maintenance, brush-free, and wire-wound (instead of rare-earth-element (REE) permanent-magnet), direct-drive wind turbine generators without a significant change in LCOE and generation efficiency. Twistact technology acts as a hedge against sources of uncertain costs for direct-drive generators. On the one hand, for permanent-magnet direct-drive (PMDD) generators, the long-term price of REEs may increase due to increases in future demand, from electric vehicles and other technologies, whereas the supply remains limited and geographically concentrated. The potential higher prices in the future adversely affect the cost competitiveness of PMDD generators and may thwart industry investment in the development of the technology for wind turbine applications. Twistact technology can eliminate industry risk around the uncertainty of REE price and availability. Traditional wire-wound direct-drive generators experience reliability issues and higher maintenance costs because of the wear on the contact brushes necessary for field excitation. The brushes experience significant wear and require regular replacement over the lifetime of operation (on the order of a year or potentially less time). For offshore wind applications, the focus of this study, maintenance costs are higher than typical land-based systems due to the added time it often requires to access the site for repairs. Thus, eliminating the need for regular brush replacements reduces the uncertain costs and energy production losses associated with maintenance and replacement of contact brushes. Further, Twistact has a relatively negligible impact on LCOE but hedges risks associated with the current dominant designs for direct-drive generators for PMDD REE price volatility and wire-wound generator contact brush reliability. A final section looks at the overall supply chain of REEs considering the supply-side and demand-side drivers that encourage the risk of depending on these materials to support future deployment of not only wind energy but other industries as well.

This report describes an FY13 effort to develop the latest version of the Sandia Cooler, a breakthrough technology for air-cooled heat exchangers that was developed at Sandia National Laboratories. The project was focused on fabrication, assembly and demonstration of ten prototype systems for the cooling of high power density electronics, specifically high performance desktop computers (CPUs). In addition, computational simulation and experimentation was carried out to fully understand the performance characteristics of each of the key design aspects. This work culminated in a parameter and scaling study that now provides a design framework, including a number of design and analysis tools, for Sandia Cooler development for applications beyond CPU cooling.