Researchers at IBM claim to have made a breakthrough in photovoltaics technology that could significantly reduce the cost of harnessing the Sun’s power for electricity.
IBM scientists are using a large lens to concentrate the Sun’s power, capturing a record 230W onto a centimetre square solar cell, in a technology known as concentrator photovoltaics, or CPV.
That energy is then converted into 70W of usable electrical power, about five times the electrical power density generated by typical cells using CPV technology in solar farms.
If it can overcome additional challenges to move this project from the lab to the fab, IBM believes it can significantly reduce the cost of a typical CPV based system. By using a much lower number of photovoltaic cells in a solar farm and concentrating more light onto each cell using larger lenses, IBM’s system enables a significant cost advantage in terms of a lesser number of total components.
For instance, by moving from a 200 sun system (‘one sun’ is a measurement equal to the solar power incident at noon on a clear summer day), where about 20W per square centimetre of power is concentrated onto the cell, to the IBM Lab results of a 2300 sun system, where approximately 230W per square centimetre are concentrated onto the cell system, the IBM system cuts the number of photovoltaic cells and other components by a factor of 10.
Concentrating the equivalent of 2000 suns on such a small area generates enough heat to melt stainless steel, something the researchers experienced first hand in their experiments. But by coupling a commercial solar cell to an advanced IBM liquid metal thermal cooling system using methods developed for the microprocessor industry, the team was able to cool the solar cell from greater than 1600oC to just 85oC.
Specifically, the IBM team used a very thin layer of a liquid metal made of a gallium and indium compound that they applied between the chip and a cooling block. Such layers, called thermal interface layers, transfer the heat from the chip to the cooling block so that the chip temperature can be kept low.
While concentrator-based photovoltaics technologies have been around since the 1970s, they have received renewed interest in recent times. With very high concentrations, they have the potential to offer the lowest-cost solar electricity for large-scale power generation, provided the temperature of the cells can be kept low, and cheap and efficient optics can be developed for concentrating the light to very high levels.