Imagine a world where we could generate electricity using the surface of our windows, smartphones, our car's sun roof or the glass roof of our office building. What sounds like a far-away dream, is on its way to become reality thanks to transparent solar panels.
Conventional solar panels, more specifically solar photovoltaic panels, absorb sunlight and convert photons (particles of sunlight) into usable energy. The difficulty with making transparent solar panels is that the sunlight passes through the transparent material. This means that the process that generates the electricity in the solar cell can not be started because no light is absorbed. This article presents two interesting attempts to overcome this obstacle: partially transparent panels and fully transparent panels employing organic salts, detailing the advantages and disadvantages of solar panels of these kinds.
Partially Transparent Solar Panels
Heliatek GmbH, a German company, has developed partially transparent solar panels, which absorb 60% of the sunlight they receive. The efficiency of these panels is 7.2%, compared to an efficiency of 12% for conventional solar photovoltaic panels of this manufacturer. The efficiency is reduced because only 60% of the light is absorbed by the panel while the remaining 40% is transmitted through the panel. Heliatek hereby shows how the solar energy production can be adjusted by adjusting the balance between light transmitted and absorbed.
Office buildings with large south-facing glass areas are already employing tinted glass to reduce the transmitted sunlight. The partially transparent solar panels have a high commercial potential for situations like these.
Fully Transparent Solar Panels
Although partially transparent solar panels are suitable for the previously mentioned cases, they are not perfectly suitable for clear windows or touchscreens. A breakthrough achieved by the Michigan State University where scientists produced a fully transparent solar panel that resembles normal glass could however fulfil this need.
The fully transparent solar panel may by definition not absorb visible sunlight. However, researchers at Michigan State University used organic salts that absorb specific invisible wavelengths of light, such as ultraviolet light. This light is then transformed and the material of the panel moves it to its edges, where stripes of photovoltaic solar cells convert it into electricity.
The efficiency of the fully transparent solar panels is currently about 1% with an estimated potential of 5%. Compared to the average efficiency of 15% for conventional solar panels, efficiencies of 5% and 7.2% for the fully and partially transparent panels respectively are still quite low.
However, solar panel efficiency does not mean everything. In practice it only means that the less efficient panel needs to be larger than the more efficient one in order to produce the same amount of electricity. As transparent solar panels can be integrated into windows in buildings, it means that the lower efficiency is overcompensated by the potential areas of employment.
There is still a long way to go before transparent solar panels become reality, but if the innovations introduced in this article can be scaled and produced more cheaply, then the seemingly far-away dream of a 'solar-powered future' is not so far away.