21 avril 2017

Novel utility-scale solar electricity generation strategy 

In the framework of a collaborative research project between Ben Gurion University and PROMES-CNRS, we offer 3 post-doctoral positions at Ben-Gurion University (1 year). One of these 3 post-doctoral position will be extended for a one-year supplementary contract at PROMES (Odeillo, France).

Motivation: The proposed project aims at a novel utility-scale solar electricity generation strategy, with day-night storage and unprecedented efficiency, via an innovative conflation of high-efficiency photovoltaics (for direct conversion of sunlight to electricity), high-temperature solar thermal (for conversion via Rankine cycles), and a new genre of innovative concentrator optics that facilitates these ambitious objectives.

The system design is predicated on new unprecedented 3D concentrator optics - to wit, aplanatic solar tower systems - where a completely static secondary mirror atop the tower can be used to actually increase flux concentration (in contrast to conventional Cassegrain beam-down solar tower optics), while simultaneously permitting a receiver (focus) at or below ground level, with prodigious practical advantages. This core concept can also be implementated as part of a multi-tower system, where a given heliostat can be aimed at more than one tower, depending on solar geometry, thereby substantially reducing shading and blocking losses, as well as markedly increasing system ground-cover ratio.

Multi-junction photovoltaics currently lack the affordable, efficient storage capability of solar thermal. Hence the paramount importance of storage skews the system optimization toward a limited fraction of photovoltaic direct conversion.

The importance of operating at high concentration (e.g., exceeding 1,000 suns) is multi-fold. First, solar cell efficiency can increase as the logarithm of concentration. Second, high concentration basically removes the per-cell cost of expensive multi-junction solar cells from the cost equation. Third, system heat loss need not exceed more than a few percent of the the collected solar beam radiation, even at these high temperatures, simply for geometric reasons, also obviating the need for selective coatings used extensively in line-focus solar thermal power systems. And fourth, the high collection temperature needed for high-efficiency turbines is readily achieved at high concentration.

The project divides into three linked scientific realms: photovoltaic materials, optics, and thermal design, as follows.