A concentrating solar photovoltaic (PV) design from a Swiss company called D Solar shows a promising blend of multiple technologies that concentrates the sun by a factor of 2,000 but keeps the resulting temperature below the boiling point of water.
Concentrating solar uses mirrors to reflect sunlight onto a small PV chip to create electricity or on a heat collection liquid to create thermal energy. The D Solar system does both at the same time. The new design, called Sunflower, merges advanced concrete engineering with low-cost optics and a water cooling system designed by IBM scientists to provide a cheap method of turning sunlight into electricity and hot water.
At the heart of the Sunflower system is a receiver on which the sunlight is concentrated. Any attempt at concentrating sunlight onto a PV cell faces a fundamental problem: concentrated sunlight gets too hot for the PV chip. By running water through the chip at a high rate of speed, that heat can be carried away. But cooling such a system is an extremely complex engineering task that requires space-age ceramics, precise flow control, and sturdy pumps. IBM has been working on thermal control of computer chips at data centers, and its engineers saw a use for their cooling technology in the concentrating PV space.
Another fundamental problem of concentrating PV is that the mirrors or lenses used to concentrate the sunlight are often as expensive as the PV chips themselves. To get around this, the Sunflower system uses stretched membranes of reflective plastic. The Sunflower system resembles a large satellite dish, but instead of a sheer dish, the reflective area comprises multiple round mirrors, each consisting of a stretched foil that’s focused by putting it under vacuum pressure. The pressure of the vacuum can alter the direction in which the foil reflects sunlight. The entire dish is then covered by a bubble of another thin film of transparent plastic, which keeps dust, birds, and rain off the reflectors.
The sunlight is reflected onto a central receiver that contains the PV chip and the water-immersed ceramic receiver. The dish is held up on a pylon of low-cost concrete, making all the materials in the device (save for the square inch of high-efficiency PV) very low cost.
Heat and Power
One of the economic attractions of the design is that, in addition to producing electricity from the PV chip, it also produces a significant amount of hot water, which can then be used for space heating, industrial processes, or even desalination. The value of the electricity and the thermal energy together means more income can be produced by the same device.
While D Solar isn’t providing any cost estimates for the system (the small-scale prototype has not been completed yet), it’s clear that the design has the potential to be an extremely low-cost method of producing solar power. While there have been many attempts at designing concentrating PV systems, none have quite been as unique and creative as the Sunflower system.
Tags: Concentrating Solar Power, Distributed energy, Renewable Energy, Smart Energy Program
| No Comments »