Transparent solar collectors may replace conventional windows


August 25, 2014

Researchers at Michigan State University claim to have a solar collector so clear that it could replace conventional glass in windows

Researchers at Michigan State University claim to have a solar collector so clear that it could replace conventional glass in windows

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Researchers working at Michigan State University (MSU) have created a completely transparent solar collector which is so clear that it could replace conventional glass in windows. The new devices – dubbed transparent luminescent solar concentrators – have the potential to not only turn windows into solar electric generators, but the screens of smartphones, vehicle glazing, and almost anything else that has a see-through surface.

Experiments with transparent solar collectors have been conducted for quite some time now, but they have resulted in variable success and many poor results – particularly around the inefficient production of energy. More to the point, most of the produced materials weren't completely transparent, rather being brightly-colored or too darkly tinted.

"No one wants to sit behind colored glass," said Richard Lunt, assistant professor of chemical engineering and materials science at MSU. "It makes for a very colorful environment, like working in a disco. We take an approach where we actually make the luminescent active layer itself transparent."

Unlike standard photovoltaic solar cells that capture energy mainly from the visible part of the light spectrum, the transparent solar collectors developed by the MSU team use microscopic organic molecules designed to absorb specific wavelengths of light invisible to the human eye. To accumulate and use this solar energy, the collector channels the light to the perimeter edge of the plastic where it is transformed into electricity by thin strips of photovoltaic solar cells.

"We can tune these materials to pick up just the ultraviolet and the near infrared wavelengths that then 'glow' at another wavelength in the infrared," explained Lunt. "Because the materials do not absorb or emit light in the visible spectrum, they look exceptionally transparent to the human eye."

As previously stated, one of the proposed uses of this completely transparent material would be in its use as a solar collector in place of conventional glazing or where transparent plastics are now used. The team admits that the technology is still at an early stage in its development, but claims that it holds the prospect of being scaled-up to commercial levels for use in industrial applications and can be produced at a reasonable cost.

"It opens a lot of area to deploy solar energy in a non-intrusive way," said Lunt . "It can be used on tall buildings with lots of windows or any kind of mobile device that demands high aesthetic quality like a phone or e-reader. Ultimately we want to make solar harvesting surfaces that you do not even know are there."

The research is also at an early level of efficiency as well; despite references to the inefficiencies of colored solar collectors, the prototype MSU devices barely produce a solar conversion efficiency of 1 percent. As a result, the team aims to reach efficiencies "beyond 5 percent" at some stage, noting that the best colored solar collectors developed elsewhere have a conversion efficiency of about 7 percent.

The research recently featured in the journal Advanced Optical Materials.

Source: MSU

About the Author
Colin Jeffrey Colin discovered technology at an early age, pulling apart clocks, radios, and the family TV. Despite his father's remonstrations that he never put anything back together, Colin went on to become an electronics engineer. Later he decided to get a degree in anthropology, and used that to do all manner of interesting things masquerading as work. Even later he took up sculpting, moved to the coast, and never learned to surf. All articles by Colin Jeffrey

So the prototype has a 1 percent conversion efficiency. I would rather sit behind a colored glass with 7 percent efficiency.


The technology we really need is a very inexpensive way to collect this minute energy and be able to apply to our building's local grid. Almost every building needs windows so if these are almost as cheap as regular ones, why not? Same with solar shingles for houses. You have to have a roof made of something, even if you live in a place without a lot of sunlight if they can make the difference in price not that much more, why not just put them on?

Rann Xeroxx

@Rann, The solar cells themselves are not the most expensive or problematic part of the equations though. in order to tie it to the grid you need expensive Inverters that can match and sustain the same phase as the local grid power and this usually also involves large expensive batteries to smooth out the power generation to something stable. I love the idea of replacing current "unused" space for clean energy production but the overall technology and install methods need to be perfected as how often are you going to want to be replacing commercial windows or re-shingling your roof. It would be nice if the power companies could lease our roof space to place their own solar collection systems in place.


Their biggest problem will be manufacture - bespoke, or 'new home' windows are one thing, making enough varied sizes to retrofit existing home and structures will be the problem. Present day solar panels for roofs are tolerated but roof windows may not be.

The Skud

mass produce? awesome & for hotels, resorts, colleges, apts, condoes worldwide.

Stephen Russell

I wonder if the amount of UV and IR that is rejected is similar to low-e glass. That would offset some of the cost for energy harvesting. If UV/IR rejection is similar, and if the price is not too much more than low-e glass (a couple of big "ifs" I realize), however much energy might be captured would be quite the bonus.


“Nibblonian” raises an interesting point by mentioning “Low-e glass”.

Vendors of architectural Low-e glass claim benefits of blocking non-visible (UV and Infrared) light.

Blocking infrared light significantly lessens the warming of interior spaces. So, especially in hot climatic zones, blocking of infrared light will reduce one’s air conditioning bill. In fact, low-e should be somewhat beneficial in any climate. As PPG claims, “The silver low-e coating reflects the interior temperatures back inside, keeping the room warm or cold.” See:

Blocking UV light is also beneficial. UV light bleaches wood and fabrics (including carpets, curtains, and furniture). And UV light breaks down most plastics.

I’m surprised that neither this article nor the original MSU article mention the benefits of blocking non-visible light. Until these new Transparent Solar Collectors achieve efficiencies significantly better than 1%, the blockage of non-visible light might be more valuable than the energy collected.


Blame it on OCD, but window "glazing" is not like food glazing -- window glazing seals a window in place but food glazes cover the food. So "replacing the glazing" of the window is not what is being done here. It's more like the coatings on high e rated windows (which also need inert gas between panes for high-e".

On another energy issue: there are no discussions regarding energy harvesting and its effect on the reallocation of energy at it relates to the environment. If we harness the oceans waves and the wind, then less of that is available for what they normally do (e.g. dispersal of toxins to "freshen" the air or ocean, habitat effects, etc.). If our windows absorb specific energy bands (rather than pass them through or reflect them), is there any balance being upset?

As for efficiency: if these cells absorb that energy band with a 1% efficiency, but the majority of the sunlight's spectrum is in that band, then maybe 1% is efficient relative to something that absorbs 7% of something that constitutes a lesser percentage of the energy. So it seems that there are more questions than answers in this article.

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