The sun is a powerful source of renewable energy. In fact, it is currently the only energy source capable of supplying the energy needs of the human race, so it’s no wonder that the use of solar energy is increasing. But there are a number of technological limitations when it comes to photovoltaic cells.

Photovoltaic, a method for generating electric power by using solar cells to convert energy from the sun into a flow of electrons, cells utilize a very narrow range of the solar spectrum – the broad light supplied by the sun. Radiation not within this narrow range merely warms these cells but is not utilized. This energy loss limits the efficiency of current solar cells to around 30 percent.

Researchers at the The Technion – Israel Institute of Technology in Haifa have developed a new technology that could improve the efficiency of photovoltaic cells by nearly 70 percent.

Left to right: Assaf Manor, Assistant Professor Carmel Rotschild and Nimrod Kruger

The Technion team’s method is based on an intermediate process that occurs between sunlight and the photovoltaic cell. The photoluminescence, light emission from any form of matter after the absorption of photons, material they created absorbs the radiation from the sun, and converts the heat and light from the sun into an “ideal” radiation, which illuminates the photovoltaic cell, enabling higher conversion efficiency. As a result, the device’s efficiency is increased from 30% (the conventional value for photovoltaic devices), to 50%.

The study was conducted at the Technion’s Excitonics Lab, headed by Carmel Rotschild, Assistant Professor at the Faculty of Mechanical Engineering, with the assistance of the GTEP Energy Center and the Russell Berrie Nanotechnology Institute at the Technion, and as part of the lab’s ERC project on new thermodynamic tools for solar cells.

An alternative to fossil fuels

But can solar indeed become an affordable alternative to fossil fuels? The scientists at the Technion believe it can.

“Today costs of photovoltaics are comparable to fossil fuels,” Rotschild tells NoCamels. “The prices of photovoltaics are dropping every year due to collective effort of the scientific and engineering community. This ensures that solar energy will become significant.”

“Taking into account the damage to the environment and health, solar energy is a much better solution,” he adds. “Also, taking into account that we’ll run out of fossil fuels (and uranium for nuclear energy), than only renewable energy can help us.”

Inspired by optical refrigeration

The inspiration for the breakthrough comes from optical refrigeration, where the absorbed light is re-emitted at higher energy, thereby cooling the emitter. The researchers developed a technology that works similarly, but with sunlight.

“Solar radiation, on its way to the photovoltaic cells, hits a dedicated material that we developed for this purpose, the material is heated by the unused part of the spectrum,” graduate student Assaf Manor, who led the study as part of his PhD work, said in a statement. “In addition, the solar radiation in the optimal spectrum is absorbed and re-emitted at a blue-shifted spectrum. This radiation is then harvested by the solar cell. This way both the heat and the light are converted to electricity.”

Just five years away

The group hopes to demonstrate a full operating device with record efficiency within 5 years’ time. If they are successful, they feel could become a disruptive technology in solar energy. “Solar is here already in the large scale instillation, it will take 10 years to become significant in the global energy supply. In 5 years I believe we can introduce a disruptive technology to photovoltaics, ” Rotschild tells NoCamels.

“In our generation we will run out of oil, gas, coal, etc,” Rotschild tells NoCamels. “Solar is here, and it is the only sustainable solution.”

Photos: Technion