Energy


Efficient planar solar concentrators have the potential to massively improve the efficiency of solar power. However, efforts to create them have proven difficult. The HyMoCo project is developing novel waveguides that could help these devices become a reality


Hybrid waveguides for highly efficient planar solar concentrators


As the world’s need for energy increases every year, solar power represents one of the greatest


sources of clean energy


available. As noted by Dr Gerhard Knies while he pondered alternative sources of clean energy in the wake of the Chernobyl disaster, “in just six hours, the world’s deserts receive more energy from the sun than humankind consumes in a year.” However, the challenge remains of how to harness this energy efficiently and cheaply. The two preeminent technologies used to


convert sunlight into electrical power are photovoltaics (PV) and concentrated solar power (CSP). The concept behind a CSP plant is relatively simple – light is collected with thousands of mirrors (which are


mechanically moved to track the position of the sun) and focused into one place where solar energy is converted into thermal energy. This energy is then converted first into mechanical energy and then into electricity using a heat engine and an electrical power generator. The efficiency of state-of-the-art CSP plants is fairly high — about 30 per cent — but the maintenance costs and difficulties of working in the desert environment mean that


they are


often too expensive. Photovoltaic solar cells use a different


approach, directly converting solar power into electrical power. Their conversion efficiencies are comparable to that of CSPs plants, although they are more expensive to


produce than mirrors and so their cost per area is larger. However, significantly, their maintenance costs are much lower than what is required for CSP plants. Reducing the production cost of solar cells would thus make them the more attractive option. Efforts have been made to increase the


efficiency of photovoltaic solar cells using solar concentrators that take sunlight from a wide area and bunch it together into a specific,


smaller location – similar in


concept to CSP, but with no expensive moving parts. This combination of concentrating sunlight onto solar cells has the potential to push the efficiencies of solar power beyond what has been achieved before. “The concept can revolutionise


Figure 1: The proposed device reduces optical loss by placing scattering bodies at the point of the node where there is no light inten- sity. The scattering bodies strongly interact with incident light but stay “invisible” and so propagation is not affected.


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