Written by IEEE | November 30, 2017
The conversation around solar energy is always hot – no pun intended – but there are still barriers to making it a broad-stroked reality. Researchers at the National Solar Thermal Test Facility in Albuquerque, New Mexico are currently working on a solution that will better concentrate solar energy making it more accessible, efficient and more affordable.
The solution is designed to transmit energy to a receiver from mirrors that are focused on sunlight. This is a spin on existing methods that would transmit the heat to some sort of fluid, raising its temperature until it produces steam, which would ultimately power the system. The new method differs in that it relies on small, sand-sized particles that will constantly fall through the concentrated sunbeam. These particles are able to reach significantly hotter temperatures, having strong implications for efficiency, but not quite on cost.
While this innovative approach to solar energy has federal interest — the Department of Energy (DOE) plans to invest $62 million in 12 projects that follow this model — the path to implementation is both complicated and costly. Existing projects like Ivanpah plant, which uses 170,000 mirrors and is owned by BrightSource, Google, and NRG, held billion-dollar price tags and came with major hiccups around production and safety.
In addition to the New Mexico project, researchers at the DOE have set their sights on transitioning from traditional steam to a supercritical carbon dioxide Brayton cycle, which has the potential to be nearly 30% more efficient than current methods. The barrier across solutions remains the same — each requires powerful heating systems to reach their full potential. The supercritical carbon dioxide Brayton cycle, though effective and efficient, requires a heat source of at least 700 degrees Celsius, and a transfer method that can support those extreme temperatures.
The project by Sandia in New Mexico is the closest iteration — and has reached as high as 900 degrees Celsius, with falling particles made of alumina and iron oxide. The only thing missing from this prototype is the heat exchanger, which the team hopes to implement by March to be powered for the summer of 2018.