This Small Business Innovation Research (SBIR) Phase I project will lower the cost of parabolic trough concentrating solar power (CSP), which uses trough-shaped mirrors to focus sunlight on tubes to harvest heat for generating electricity. The tubes are coated with a dark substance, 'absorber', that efficiently absorbs light and can withstand high temperatures. In present-day commercial designs, the absorber tube is packaged inside a vacuum-holding glass sheathe to form a 'receiver'. Standard receivers have drawbacks: (1) When gas leaks into them, they fail. (2) The absorber pipe radiates heat in all directions through the transparent sheathe, wasting energy. (3) The absorber coatings are complex. Receiver designs that avoid these problems require novel absorber coatings and cost-effective ways to apply those coatings during manufacture. This project will improve a recently developed novel absorber coating and demonstrate a simple, cost-effective method for applying it to receiver tubes. Improvements include experimentally investigating why the coating in its present form resists chemical degradation under realistic operating conditions and adjusting its composition accordingly to further increase its performance. The coating manufacturing and application processes will be demonstrated at laboratory scale by building and performance-testing actual receivers.
The broader impact/commercial potential of this project will be achieved by reducing the cost of parabolic trough CSP. Parabolic-trough CSP is being developed rapidly in the US and other countries that seek to reduce pollution and increase energy security, creating a growing global market for CSP components. Receivers are an indispensable and costly part of parabolic trough CSP. For example, a parabolic trough CSP plant large enough to produce 250 megawatts of electric power contains about 60,000 receiver tubes. This SBIR project, by producing a lower-cost, vacuum-free receiver that uses a novel absorptive coating, will reduce both the capital and maintenance costs of CSP. The new design and materials will simplify receiver manufacture, improve performance, and do away with failure-prone vacuums. Scientific understanding of the properties of absorber coatings will be increased by experiments performed under this project, and new receiver-manufacturing technology will be demonstrated. Reducing the cost of energy from CSP will speed deployment of this inexhaustible, 100% domestic source of power, speeding progress toward a pollution-free, secure energy economy.
Under this NSF SBIR Phase I/IB project, Norwich Technologies (NT) undertook the development and prototype application of a novel light-absorbent coating for receivers (i.e., tubes carrying fluids heated by mirror-focused sunlight) in Concentrating Solar Power (CSP). In general this research is directed to developing a simpler, more-easily manufactured, air-tolerant alternative technology—namely, chains of nickel nanoparticles embedded in silicon-rich ceramic—to achieve performance equal or superior to existing coatings at lower cost and more reliability. This new class of materials, discovered by the group of Prof. Jifeng Liu at Dartmouth, has been provisionally patented and demonstrated in the laboratory. One application for this novel solar selective absorber is with a novel, non-vacuum CSP receiver system being developed by Norwich Technologies. Developing the two technologies together will result in a disruptively more affordable and reliable technology for CSP receivers, a key cost component of this rapidly deploying form of renewable energy. During this Phase I/IB project, Norwich Technologies with the Liu Group at the Thayer School of Engineering, identified, modelled, and tested key aspects of coating techniques for the Ni-nanochain cermet coating application, including the successful dip coating and characterization of a series of samples. These dip coating experiments closely match an empirical model from literature. The Liu Group investigated the chemical mechanism of the coating anti-oxidation performance by comparing the coating structure and performance resulting from various precursor chemistries and identified an optimal approach, as well as worked to tune coating performance for optimal solar-selective properties. Norwich Technologies and Creare, Inc. designed a high-temperature testing system for coating optical properties and performed initial characterization experiments using a similar system at MIT. Norwich Technologies used previously developed optical and thermal test stands to enable full-scale coating testing and performed benchmarking tests with coatings of known properties. This project is focused on materials development of a commercially viable manufacturable solar selective coating particularly suited for concentrating solar power. This research enables development of our SunTrap receiver which will (1) operate more efficiently at higher temperature (T) than existing receivers, (2) decrease acquisition costs, and (3) dramatically increase reliability by eliminating vacuum. The Advanced Materials subtopic seeks "research and development of new materials and systems that have the potential for revolutionary changes and paradigm shifts in U.S. industry." The research and development herein clearly has such potential. Reducing the LCOE of CSP, with its proven ability to supply both peaking and baseload power as well as process heat, is a priority of the US government and energy industry, and this research enables such reduction. In particular, under AM3, "Materials for Energy Applications," the NSF seeks "material innovations for solar energy harvesting," and the proposed research answers to this goal. Our novel solar selective coating and receiver technology, by increasing the reliability, efficiency, and affordability of a key CSP component, will (1) address a burgeoning US and global market opportunity, (2) advance CSP technology, and (3) accelerate deployment of CSP and realization of its social benefits.
