MIT develops hot carbon nanotubes that lets solar panels draw more sun


Solar energy has been receiving more and more attention as governments are trying to shift from fossil fuel-based energy sources to more natural and renewable options.

While solar panels have been around for a while now, scientists have been struggling to increase the efficiency of current panels to make it a more viable option for fueling modern power-hungry homes and cities. Solar panels work by converting the energy found in the sun's rays to electricity. Due to the sheer amount of energy emitted by the sun on a daily basis, solar systems could very well provide all the power modern society will ever need.

Even the best solar panels currently available, however, are only able to achieve a 21.5 percent conversion rate. Theoretically, the current photovoltaic systems used on solar panels can collect solar energy with an efficiency of up to 33.7 percent. However, even a solar panel operating at the theoretical maximum still won't be able to collect a large portion of available energy. Scientists have long been trying to increase the efficiency of these systems and the answer may lie in the use of carbon nanotubes. While things like Dyson Spheres or even solar lasers could take tens or maybe even thousands of years to develop, this new type of solar cell could be a sign of things to come.

A team of researchers from the Massachusetts Institute of Technology (or MIT) is developing a new type of solar cell that uses a very thin layer comprised of carbon nanotubes to boost efficiency. One of the difficulties that scientists face when designing and developing new types of solar cells is that not all available wavelengths of light can be converted into energy. The carbon nanotube layer may, however, allow a new generation of solar cells to harvest energy from certain wavelengths that normal photovoltaic cells cannot collect.

The carbon nanotubes experience an increase in temperature after being heated by the sun's rays. Under the right conditions, sunlight can be focused and concentrated to heat up the carbon nanotube layer to 1,763 degrees Fahrenheit or 962 degrees Celsius. At these temperatures, the carbon nanotubes can heat up a layer of photonic crystals, another critical component of the new system, which can generate light at certain temperatures. The light emitted by the photonic crystal array can then be turned into electricity using photovoltaic systems. Thus, the carbon nanotube layer and the photonic crystal array functions as an absorber and emitter respectively. The carbon nanotubes absorb heat directly from the sunlight and the photonic crystals emit a type of light that can be converted to electricity by photovoltaic systems more efficiently.

Experts such as MIT associate professor of mechanical engineering Evelyn Wang say that carbon nanotubes heated to a certain temperature will be able to provide a dramatic increase in solar cell efficiency. If the new method works, the next generation of solar panels could operate at an ideal efficiency of over 80 percent. A solar system with this efficiency covering a large enough area could very well power an entire city with ease, provided that adequate energy storage systems are also in place.

The MIT research was funded by the U.S. Department of Energy, the Martin Family Society, the the National Science Foundation, and the MIT Energy Initiative.

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