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Bold Move! The Future of Solar Cells: Thermophotovoltaic Cells

July 3, 2017

Everyone knows Tesla Motors is widely hailed as a pioneer in electric power. Their relatively successful Model S has helped build Tesla into one of the most valuable motor companies in the world. Tesla has also started to make waves with the release of solar panels and sustainable energy systems designed for the home. Tesla’s Solar Roof tile is a unique product that looks like a traditional roof tile, but is in fact a glass covered solar cell.

Tesla has a unique Intellectual Property in the Solar Roof, and appears to be at the forefront of modern solar cell design. Researchers at MIT, however, have developed a far more interesting technology. In a study published just a few years ago, researchers at MIT have found a way to increase the efficiency of solar cells by using thermophotovoltaic cells.

Traditional solar cells use what are known as photovoltaic cells. They capture light energy and convert that energy into electricity. Photovoltaic cells are physically limited in the amount of energy they can harness from the sun—they are only able to capture a narrow range of wavelengths in the light spectrum. Because the solar cells can only capture a fraction of the wavelengths present in light energy, they are constrained by a peak efficiency. This theoretical maximum, known as the Shockley-Queisser limit, suggests that only 33.7 percent of the suns energy can be converted into electricity from a solar cell. Research has focused on breaking this limit through a variety of means, particularly in nanoscale engineering where material properties can differ from larger scale molecular structures.

Researchers at MIT have found a way to improve the yield of solar cells by using thermophotovoltaic cells over traditional photovoltaic cells. A thermophotovoltaic cell contains a heat energy component in addition to a light energy component. The MIT researchers created the heat energy element with a layer of carbon nanotubes designed to absorb all visible light entering the cell. As it absorbs all the incoming light energy it heats up considerably, then emits that heat energy as specifically tuned light wavelengths. These wavelengths are tuned to fall within the range that the photovoltaic cell can actually use. By capturing all of the light energy from the sun and converting it into specific wavelengths presented to the photovoltaic cell, the carbon nanotube layer reduces the waste inherent in traditional photovoltaic cells. This increased efficiency suggests that the Shockley-Queisser limit may be surmountable.

Because of their inherent inefficiency, photovoltaic solar cells are only viable where they can be used in volume over a large area, such as a roof. It is unlikely thermophotovoltaics will upset Tesla’s market share cornered by the Solar Tile.

Thermophotovoltaics will be key, however, in unlocking the potential of small scale solar cell applications. Achieving efficiency beyond the Shockley-Queisser limit is critical to widespread application of solar energy devices to everyday energy consumption. Imagine a world where you don’t have to fetch gas for your lawnmower, charge your phone, ever, or power streetlights off a city grid. The possibilities could be endless.

Author: Mason Pastrana, Intern

With thermophotovoltaics at the forefront of solar power technology, do not be surprised if more companies or inventors are implementing this technology into their new devices, and with those, their patents. In the fast-paced industry of renewable energy, don’t wait to seek IP protection for your idea. Secure your rights before someone else does!


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