Energy

Thin plastic overlayer doubles efficiency of rooftop solar panels

Thin plastic overlayer doubles...
Insolight's solar panels have achieved a possible record-breaking 36.4 percent efficiency
Insolight's solar panels have achieved a possible record-breaking 36.4 percent efficiency
View 2 Images
Insolight's solar panels have achieved a possible record-breaking 36.4 percent efficiency
1/2
Insolight's solar panels have achieved a possible record-breaking 36.4 percent efficiency
The top layer of tiny lenses directs sunlight to a small, very high performance solar cell
2/2
The top layer of tiny lenses directs sunlight to a small, very high performance solar cell

While the latest commercially available rooftop solar panels boast conversion efficiencies around the 18 to 20 percent mark, there are solar cells capable of achieving efficiencies of over 40 percent. So why aren't these making their way onto roofs? The answer is cost. But that could be about to change with Swiss startup Insolight developing a thin plastic layer that sits atop a panel and directs the sun's rays to a small area of very high performance solar cells.

While some researchers are devoted to improving the efficiency of solar cells themselves, other efforts to increase energy output involve developing systems that focus as much sunlight onto the cells as possible. But the efficiency is still dependent on the solar cells' performance, while existing concentrators can be cumbersome and need to constantly be repositioned to reap their full benefits.

Insolight's strategy was to use some of the highest rated solar cells already available, which yield 42 percent efficiency by capturing different wavelengths of light. These cells are prohibitively expensive for all but special uses, notably in aerospace, so to keep costs down the company only uses small numbers of the super cells.

They then turned to the issue of how to concentrate the sunlight hitting the cells and 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.

"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," says Laurent Coulot, Insolight's CEO.

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, which can prove especially important for higher latitudes.

The Fraunhofer Institute in Germany has independently validated performance of a prototype, which Insolight claims achieved a yield of 36.4 percent, or roughly double that of traditional solar panels for the same footprint – which the company says, "is a potential world record for a flat panel that can be mounted on a roof."

The prototype with now be 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 produceable. It's also comparable in size to conventional solar panels, and can be installed with standard mounting systems.

The company believes their cells will be a little more expensive than conventional solar panels, "but this will be quickly offset by the additional energy that will be generated," says Florian Gerlich, Insolight's COO.

The company developed their concept with a grant from the Ecole Polytechnique Federale de Lausanne (EPFL) in the Laboratory of Applied Photonics Devices.

The video below gives an overview of the system.

Source: EPFL, Insolight

An optical overlayer makes residential solar panels twice as efficient

7 comments
StéphanAubin
Fine looks promising but can you tell us how many solar cells they use per m². As they use >40% efficiency solar cells and pretend to reach 36% efficiency, it would be good the ratio is lower than 36/40 :)
Future3000
They don't double the efficiency, they collect more sunlight on a smaller PV cell surface. Thats well known since the beginning of PV collectors. If you can install 100 m² PV modules on your roof, conventionally you have 20 KWp. With this shown lenses you cover also 100 m² and have also 20 KWp, but you need only 60 m² PV Modules + 100 m² Lenses. If this is cheaper and easier to clean as 100 m² nanocoated regular PV modules... I don't know. If they cover 100 m² and produce 40 KWp, then they have doubled the efficiency, but they didn't. Yes, there are PV Modules 40% efficiency, but NOT these! Don't trust stories, think for yourself please!
Rocky Stefano
They seem to be taking up the same amount of space which is too bad. Would have been nice to decrease the overall footprint.
Fritz
In the real world there is diffuse sun light, min 30% 1). 2) the multiple surface / air transitions costs each 4%min. So you loosing at the directed beam at least 40% Further on the sunlight on the chip is not equally distributed. The border cone of the lens does not hit exactly only the cell, it must be larger this costs you another min 15%. So you are down to about 45 -50% of the irradiation of a flat panel. In best case you end up with the same amount of electricity like on a flat panel. Well, you spending more money. By the way even space crafts never use concentrating sp.
Calson
A 100% solid state solar panel can operate for more than 30 years with no maintenance required. A panel that depends on moving parts that need to stay clean to function and that will wear down over time is going to require regular maintenance and periodic repairs. When panels are located on a roof 20 feet off the ground this is a very big issue.
There is also the mention that this will work at any latitude which means it must have a tilt range of at least 15 degrees for the lower 48 in the USA and 30 degrees or more for home in Canada and Scandinavia and other places at greater latitudes.
It is also assumed that panels are less efficient due to the angle of the sun and this is not the case. Solar panels work very well with a very low sunlight incidence. Light striking the panel that is 25 degrees off from being perpendicular to the panel will still provide 90% as much radiation to the PV cells.
The real problem with solar energy production is the abundance of government subsidies done directly or forced onto utility customers for fossil fuels that create artificial costs when externalities (like polllution and waste and healthcare costs and road construction and maintenance costs) are not included in the cost of the energy produced.
sidmehta
I'd wait for the real world tests before posting an article here. @Fritz you may be right.
Ray Boggs
This is nothing new. It's just a concentrator solar module. The problem is that the concentrated sunlight dramatically heats up the cells causing them to degrade faster not to mention the higher cost of the specialized solar cells. With standard solar modules hitting the mid $0.30 per Watt range, I doubt that this product can be commercially competitive.