Transparent solar panels could help achieve global net-zero targets and improve the aesthetic appearance of buildings by turning windows or any glass sheet into a photovoltaic cell. Michigan State University (MSU) researchers first created a transparent solar concentrator in 2014. By 2020, they achieved full transparency for the solar glass. This technology has the revolutionary technological potential of transforming buildings into solar energy producers.

History of Solar Energy Technology and Efficiency Improvements

Solar energy has been used since the 7th century BC, from lighting fires and torches, to creating sunrooms. Passive solar refers to the heating and cooling of living accommodation through exposure to the sun.

Horace-benedict de Saussure invented the world’s first solar collector cell in 1767, using an insulated box and layers of glass to magnify the sun’s heat.

Edmund Bacquerel, a 19-year-old French scientist discovered the photovoltaic effect in 1839.

The photovoltaic process is where the electrical current in the form of voltage, is created when electromagnetic radiation is exposed to certain materials. Solar cells are used to create the photovoltaic effect.

The first, albeit inefficient, solid-state photovoltaic cell was created by Charles Fritts in 1883. Fritts coated a selenium semiconductor with a thin layer of gold.

In 1954, Bell Laboratories demonstrated the first practical use of a silicon solar cell by attaching one to a small Ferris wheel and solar-powered radio transmitter. This solar cell was expensive and only 6 percent efficient at converting sunlight into electricity.

Many companies have developed and improved upon the technology, which is mainly focused on improving the efficiency of PV cells and making them commercially viable.

By 1985, sales of photovoltaic cells reached US $250,000,000. Efficiency for silicone cells increased to 20 percent, followed quickly by a thin-film module. In 1994, a gallium indium phosphide and gallium arsenide cell was made, with 30 percent efficiency.

By 2000, production reached 100 megawatts of power a year, and became a huge market for producers and sellers globally, including interest from governments who began to see the potential to reduce reliance on fossil fuels.

The largest solar energy plant is currently in China, with a capacity of 200 megawatts, although Germany is the biggest market for domestic photovoltaics.

The price of solar systems continues to fall as demand for solar technologies increases.

Transparent Solar Technology

With technology improving year on year, next-generation solar cells have been created, eliminating the use of lead. Some incorporate the mineral perovskite, producing a 28 percent efficiency outcome.

One of the latest developments at Michigan State University is near-transparent cells made from glass-like plastic, which are paper-thin and allow electricity to be generated from windows.

They work by selectively harnessing a portion of the solar spectrum invisible to the naked eye, whilst at the same time allowing normal visible light to pass through. This is achieved using a transparent luminescent solar concentrator (TLSC), which comprises organic salts designed to absorb specific UV and infrared light wavelengths, which luminesce as another invisible wavelength.

The efficiency is currently only around 10 percent, but considering every home and office building could be transformed, the impact it could have on society could be huge.

Partially transparent solar panels exist, which were developed by Heliatek Gmb in Germany. These absorb approximately 60 percent of sunlight and have a lower efficiency of 7.2 percent.

The fully transparent solar panels developed by MSU produce a fully transparent glass-like photovoltaic panel, achieving a higher 10 percent efficiency once in commercial production.

Benefits of Fully Transparent Solar Panel Technology

Although solar window efficiency is lower than many other solar PV panels and partially transparent ones, their aesthetic look, combined with their ability to be integrated into large window spaces on almost any building, provides a higher potential for everyday and ongoing use.

In addition to solar window technology, solar panel blinds can harvest sunlight to produce electricity and can be used in conjunction with transparent solar panels to block direct sunlight, whilst still producing 100 watts of power.

Solar blinds can be installed inside or outside, and controlled by an app to optimize performance using angle and positioning controls incorporated within the app.

Transparent solar panels have the additional benefit of operating in low lighting, as little as 10 percent, which extends the number of hours over the year in which electricity can be generated. They are also less affected by shading.

The panels have superior heat tolerance, so do not require ventilation to achieve optimal performance. They also operate at higher efficiency over a greater temperature range.

They are economically advantageous because they cost around the same as conventional building materials, but are multi-functional, providing electricity as well as just being a window. They could eliminate the need for conventional electricity generation systems, reducing bills for homes and businesses.

The panels are very strong, with laminated glass to increase functionality, safety and improve aesthetics. They could potentially be used in many heritage, or listed buildings where preserving aesthetic appearance is highly desirable.

Michigan State University Commercial Partnerships

MSU has partnered with manufacturers Ubiquitous Energy, Physee, and Brite Solar.

Ubiquitous Energy is in partnership with NSG group, producing ClearView Power technology, which integrates transparent solar panels into architectural building designs, with the aim of achieving net-zero energy buildings.

Physee is a European manufacturer and uses PowerWindow, which makes use of small solar panels installed along window pane edges, but with potential for scaling up and improving efficiency.

Brite Solar is also a pioneer in using and promoting the new solar panel hybrid systems.

Transparent Solar Technology Future Potential

MSU researchers are confident that transparent solar panel technology has the potential to meet around 40 percent of US annual energy demand, potentially even more when combined with rooftop solar, as they act to complement each other.

Energy storage improvements are still needed, but MSU indicates that 100 percent of the US electricity needs could be met in the not too distant future if storage improvement technology is achieved.