Window power (Day 99)

WindowIn theory, there’s enough light from the sun to provide all of the world’s energy needs. Clean, limitless and renewable it is a very attractive proposition.

Of course, it is not as simple as that. It doesn’t work at night and seasonality, atmospheric conditions and variable climate conditions (mostly clouds) mean it is less viable in some parts of the world.

There are other practical challenges too. Solar farms need to cover large surface areas to be commercially viable. This demand for space is also reflected for home-based solar power generation. Large solar panels are dotted on house roofs and buildings – not pretty and certainly not integrated into house design the way architects would prefer.

But that may change in the future. A team of researchers at Michigan State University (MSU) has developed a new type of solar concentrator that can be integrated into windows. It creates solar energy and allows people to actually see through the window.

The prospects of a window design that retains heat through double and triple glazing, and generates energy seems like a very attractive and discreet solution.

In fact, the transparent luminescent solar concentrator (LSC) and can be used on buildings, cell phones and any other device that has a clear surface.

And, according to Richard Lunt, an assistant professor of chemical engineering and materials science at MSU’s College of Engineering, the key word is “transparent.”

Research in the production of energy from solar cells placed around luminescent plastic-like materials is not new. These past efforts, however, have yielded poor results – the energy production was inefficient and the materials were highly colored.

MSU Solar Glass Project

Yimu Zhao, a doctoral student in chemical engineering and materials science, and Richard Lunt, assistant professor of chemical engineering and materials science, run a test in Lunt’s lab. Lunt and his team have developed a new material that can be placed over windows and create solar energy. Photo by G.L. Kohuth.

“No one wants to sit behind coloured glass,” said Lunt. “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.”

The solar harvesting system uses small organic molecules developed by Lunt and his team to absorb specific nonvisible wavelengths of sunlight.

“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,” he said.

The “glowing” infrared light is guided to the edge of the plastic where it is converted to electricity by thin strips of photovoltaic solar cells.

“Because the materials do not absorb or emit light in the visible spectrum, they look exceptionally transparent to the human eye,” Lunt said.

One of the benefits of this new development is its flexibility. While the technology is at an early stage, it has the potential to be scaled to commercial or industrial applications with an affordable cost.

“It opens a lot of area to deploy solar energy in a non-intrusive way,” Lunt said. “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.”

Lunt said more work is needed in order to improve its energy-producing efficiency. Currently it is able to produce a solar conversion efficiency close to one per cent, but noted they aim to reach efficiencies beyond five per cent when fully optimised. The best coloured LSC has an efficiency of around seven per cent.

We wish them good luck with their work which has great potential to take solar energy to a new level.

One thought on “Window power (Day 99)

  1. According to a presentation by a German chemical engineer I heard in Manchester there is sufficient solar energy falling on 1% of the Sahara Desert to power all of mankind’s activities. So there is plenty of solar energy to go around.

    Finding an unobtrusive way to collect some of this for generating electricity looks like a good idea.

    One thing that I have never had the time to figure out is the energy balance of collected solar energy. If we collect the energy and it is not reflected back into space what is the impact on the Earth’s temperature?

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