Dyebased cells

The dominance of silicon is being challenged by a new generation of solar cells that mimic the process of photosynthesis. Developed by Michael Gratzel and Brian O'Regan of the University of Lausanne, this cell uses a dye containing ruthenium ions that absorb visible light analogous to chlorophyll in nature. The dye is applied to nanocrystals of the semiconductor titanium dioxide or titania. The titania has the electronic property of being able to draw electrons from the ruthenium and propel them off into an electrical circuit.

The construction of the cell involves sandwiching a 10-^m-thick film of dye-coated titania between two transparent electrodes. The tightly packed nanocrystals form a porous film that maximizes the light-absorbing capacity of the cell. The space between the electrodes is filled with a liquid electrolyte containing iodine ions. These ions replace those knocked out of the dye by the action of the photons. The two electrodes are connected to form a circuit that carries the electrical discharge (see Fig. 6.2).

Photons

Iodine solution

Transparent electrode

Transparent electrode

Photons

Transparent electrode

Transparent electrode

Nanocrystals of titania coated with ruthenium dye

Figure 6.2 Titanium-ruthenium dye-coated PV cell electrons

Nanocrystals of titania coated with ruthenium dye

Figure 6.2 Titanium-ruthenium dye-coated PV cell

The conversion efficiency is around 10% in direct sunlight but up to 15% in the diffuse light of cloudy days, which makes these cells especially suitable for northern climes. The cost is claimed to be only 20% of the price of crystalline silicon, and may be even less since huge deposits of titanium have been discovered in Australia.

Solar cells which are transparent are the solution to the wider application of fa├žade PVs. This means creating cells which can produce a significant amount of electricity by absorbing light only in the infrared end of the spectrum. These would be coated with a dye that is transparent yet absorbs light in this invisible part of the spectrum. Michael Gratzel of the University of Lausanne considers that such cells could achieve a conversion rate of 10%.

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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