Energetic Windows

(Image from Google search: bild.edu.stockholm.se)


I've been watching some interesting developments in the field of turning light into electricity. This past July researchers at Massachusetts Institute of Technology announced a new process they developed that concentrates the light collected over a large area of glass to its edges. This means that the solar cells only need to be located around the edges of the flat glass panel rather than covering the entire panel. Also, this means that light can pass through, or you can see out of the glass plane while it collects light at the edge to generate electricity. According to Marc Baldo, the leader of the development team, the focused light increases the electrical power obtained from each solar cell by a factor of over 40.


(image from article in Technology Review published by MIT)

The system appears to be relatively easy to manufacture and the team (consisting of Michael Currie, Jon Mapei and Timoth Heidel, and Shalom Goffri) believes they can implement commercial applications within three years. They may even be able to modify the process to work with existing solar-panel systems, increasing their efficiency by 50% at a reasonable incremental cost. The team recognized that recent developments in optical techniques developed for lasers and organic LED's could be re-applied to experiments in the 1970's that failed because too much light was lost en route to the edge. By allowing light to travel a much longer distance the team was able to reduce the transport losses and increase the amount of power converted at the solar cell tenfold.


(image from Photonics.com article)

Something I didn't realize before reading about this was that solar cells are essentially 'tuned' to specific wavelengths of light. Much of the light that hits a solar cell is simply not harvested if the cell is not sensitive to that wavelength and is energy lost. By adding dyes to the glass plates, the MIT team has been able to allow the glass to filter specific wavelengths that are then focused to the edge of that particular colored layer of glass. Sequential layers of different color 'filters' allow much more of the available light to be collected and harvested from the same unit. Each wavelength of light passes through the colored layers until it reaches the filter layer designed for it at which point it is redirected to the perimeter and the waiting solar cell specifically tuned to that wavelength. Additional cost savings are seen in the size of the edge collectors. Where a large sheet of solar cell that would traditionally cover the entire face of the collector is expensive and difficult to manufacture, this new approach requires much smaller collectors only at the edge of the glass.

We can watch for products incorporating this new development from a company the team has started to commercialize these discoveries called Covalent Solar.

Imagine stained glass windows that power your lights at night.

;-)

Put them together and what do you get?:

I hope that the team at MIT knows someone at Rensselaer Polytechnic Institute. A new anti-reflective film coating has been developed by scientists there that could help solar panels collect sunshine at 96% efficiency from nearly any angle. Their film uses layers of nanoscopic silicon and titanium-oxide rods (you got me...) in a funnel-like setup that captures light from almost every direction and focuses it onto the photovoltaic panel while inhibiting reflection. This advancement would help collect 20% more light while eliminating the need for systems that rotate the panels to follow the path of the sun across the horizon. This one's a little further afield yet as the outermost layers are almost as porous as air and they would need to be protected from heat, wind and weather. Sure seems like a good match for the MIT technology. And yet, like everything, the devil is in the details.
(What happens when you increase the collection by 40 fold and simultaneously improve collection by 96%? What's the math on that one? I'm not sure but it sounds like a promising result).


The information from this post was culled from the following secondary sources:

MIT development>

• http://www.technologyreview.com/energy/21217/
  
• http://www.photonics.com/Content/ReadArticle.aspx?ArticleID=34508

(Photonics.com is an excellent source for reviews of all types of scientific discoveries and developments related to light)

RPI development>

• "A funnel for Sunlight," Popular Science Magazine, February 2009, pg.34
  

Winter Light

Growing up in California, my experience with snow was fleeting and recreational. We would shoot up to the Sierra Nevada Mountains on Interstate 80 through 15 foot banks cut cleanly through the snow to ski for a weekend and return. Sometimes we'd have to install chains to make it there or back, but we always returned to the green and verdant hills of the San Francisco Bay.

My experience of Winter since moving to Iowa 7 years ago has been vastly different. I have yet to see snow higher than 2 feet, but neither can I drive away from it in a couple of hours. Today it is -3 degrees which is also a bit different from the Sierra Nevada, where it is the sheer perseverance of storms that keeps snow piled up through the winter, as opposed to bitter cold.

But this is not a complaint! I truly love the Winters here in Iowa. I love the dramatic change of the seasons which now mark my continued annual existence. It has forced an awareness of time and a necessity of planning not required of my youth. If you want to build something in the ground, you had better plan to dig before it freezes to granite-like density. Or if you want to eat fresh vegetables you had better plan and time your garden carefully in the Spring. (I missed mine by a week last year, and a month and a half of carefully nurtured kitchen table seedlings turned to dripping sludge as Winter cast a parting shot across my delicately manicured new garden one evening).

I enjoy this sense of time and place the seasons bring and the meaning and humility they bestow.



But what I think I love most about Winter in Iowa is the quality of light. Or perhaps a better term would be clarity of light. It was one of the first things I noticed after my move here. The quality of light was different. Sharp and crisp in the Winter, rich and warm through the summer. My early interest in photography has never left me as my career has taken various turns toward a path following light more directly. In Winter you can see the stars more clearly and crisply than any other time of the year here in Iowa. They literally explode across the moonless sky. It is almost enough to make you forget the cold creeping into your toes (which are singularly not impressed by the heavens above and would rather you had the sense to go inside and sit by the fire than hang around outside in the middle of the night in -3 degree weather while you stand dumbfounded at the magnitude of the heavens). I have never seen the Milky Way as I have seen it here.

One Winter I even witnessed the Aurora Borealis, something I was surprised at given our latitude. For someone impressed by light, that is truly a phantasmagorical experience.



In the morning, when morning breaks over the woods after a cold night, the trees awaken covered in millions of diamonds. The light refracting through ice on every branch.

The cold seems to make sound stand still and the snow commands calm all around. Watching the sun break into the day, slowly lavishing this quietude with a desperately warm embrace is exhilarating. The pink color of the early sun sweeps slowly up the white snow-laden hillside followed shortly by the warm orange glow of full day.

A strange thing happened on our pond last year one morning that I have never seen again. (And this is the nature of this Iowa place, you find quickly that if conditions are good, you must engage your opportunity in that time as it rarely lasts more than a day). I descended one morning that was exceptionally cold, easily into the -teens and encountered an acre of ice crystals standing straight up from the surface of the pond. Some an inch tall. It was a surreal and foreign environment on micro/macro scale.



The light swept across it, igniting each crystal in a micro fire of temporal existence.

It was gone the next day.