Solar thermophotovoltaic breakthrough from MIT: Harnessing both light and heat for electricity

A team at the Massachusetts Institute of Technology (MIT) is developing a new approach to making solar cells. The technology, ‘solar thermovoltaics’ or SVT, would utilise not only the light from the sun, as conventional silicon-based photovoltaic (PV) cells do, but would also be able to harness heat.

Standard silicon solar cells can only produce electricity from a limited range of bandwidths of light (called the material’s ‘bandgap’); the rest of the energy goes to waste. The MIT team who conducted the research, whose work on the subject was recently published in the journal Nature Nanotechnology, introduced an intermediary level of carbon nanotubes combined with photonic crystal to act as an absorber. This layer can absorb significantly more of the photons that fall on its surface than silicon, heating up as it does so. The innovative absorber then ‘translates’ this heat into light that is compatible with silicon’s bandgap.

The concept of solar thermovoltaics (SVT) has been under investigation for a number of years, but has not yet broken into the commercial sphere. Currently, the most efficient commercially produced solar panels have peak efficiencies (percent of sunlight converted into electricity) in the low 20% range. By contrast, the MIT team’s SVT cell demonstrated a conversion efficiency of about 3.2%–that itself a dramatic improvement on the ~1% routinely achieved by other researchers investigating the technology to date. 20% efficiency, the team says, would allow the technology to become commercially viable, but the upper limit on its efficiency could be as high as 80%. The upper limit for a plain silicon solar cell is 33.7%.

The researchers also point out that there would be the added bonus arising from generating power from heat as opposed to light: heat can be more easily stored. Electricity produced by conventional solar photovoltaic panels must be used immediately or stored in batteries; other, more affordable solutions may be available or more easily developed for storing heat directly.

A video from MIT about the research is embedded below.

Top image by John Freidah, via MIT News

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James Martin II