Innovative CPV to boost solar efficiency

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The market has witnessed solar taking the lead in clean energy transformation. According to New Energy Outlook 2016 published by Bloomberg New Energy Finance, solar technologies have become one of the cheapest way to generate power. It’s predicted that the cost of PV panel is going to fall by 60% by 2040. While the solar cell technology has been evolving over the past decade, the solar efficiency still has significant room for improvement. 


What are the key aspects to increase solar panel efficiency?

There are two main ways. One is to use better solar PV cells; the other is to use what’s called “concentrator photovoltaics (CPV)” so as to concentrate as much sunlight as possible on the solar cells.

To improve PV cells, the Boeing Spectrolab has developed a “upright metamorphic 3-junction solar cell” that can reach an efficiency level as high as 41.6%. However, this technology is prohibitively expensive at the moment for commercial use. That is why it is primarily used in aerospace facilities.


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WHAT IS CONCENTRATOR PHOTOVOLTAICS?

Contrary to conventional photovoltaic systems, Concentrator photovoltaics (CPV) uses lenses and curved mirrors to focus sunlight onto small, but highly efficient, multi-junction solar cells.

 

Current CPV technologies, in the meantime, have only come up with a cumbersome design where a tracking system constantly reposition solar panels following the direction of the sun. Moreover, current CPV have strict requirements on location and system design as:

  1. CPV system performs best under direct solar insulation, so it is better fit in low latitude locations;
  2. In areas with low insulation, the added cost of CPV may not be captured in increased solar output;
  3. The addition of trackers usually means shading issues, so system design and the placement of high-performance solar cells need to avoid potential shades.

Recently, a Swiss startup called Insolight introduced an innovative system that combines both better cells and CPV. The system blends high-performance solar cells with conventional ones, and uses a layer of tiny “magnifying lenses” on top of the cells to concentrate sunlight.

Laurent Coulot, Insolight’s CEO explains its design using a metaphor.  “It’s like a shower. All the water goes down one small drain, there’s no need for the drain to cover the entire floor of the shower.¨ So to boost solar PV system efficiency, we just need to focus all the sunlight on that ¨drain¨, which is high-performance solar cells themselves.

With CPV, the process of capturing sunlight is no longer as such:

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It is like this:4567Insolight developed an injection-molded plate arrayed with plastic bubble lenses that act like a network of tiny magnifying lenses. These focus the light hitting the panel onto segments of the solar cells that are only several square millimeters in size.     

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The plate is attached to a metallic frame that moves just several millimeters throughout the day, guided by a sensor that tracks the sun’s position. As a result, this micro-tracking system is able to capture 100 percent of the sunlight regardless of the angle of the sun.

The Fraunhofer Institute in Germany has independently validated performance of Insolight’s prototype, which Insolight claims achieved a yield of 36.4 percent, or roughly double that of traditional solar panels for the same footprint.

The prototype is now subjected to real-world testing and the company is hopeful they could be on the market before too long. This is in large part because the system is already near market ready as it was designed with components that are easily mass-producible. It’s also comparable in size to conventional solar panels, and can be installed with standard mounting systems.