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Ann R. Thryft
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Re: Another reason windows key to energy bill savings
Ann R. Thryft   8/23/2012 2:54:54 PM
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Chuck, I didn't see any data on actual energy produced, only efficiency ratings. Kevin did some rough back-of-envelope calculations in his comment, and came up with an estimate of 1.2 KWH of power per square meter of window per month (given certain reasonable assumptions).

Ann R. Thryft
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Re: Solar-window cells?
Ann R. Thryft   8/23/2012 12:09:02 PM
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Jack, the material is slightly less than 70% transparent, letting in less light than 100% transparent materials. That may account for what you see in the photo, and it would presumably block some heat and possibly some UV.

Jack Rupert, PE
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Re: Solar-window cells?
Jack Rupert, PE   8/22/2012 1:34:10 PM
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From the photo (which might be photoshopped) it appears that glass has some "light blocking" properies as well.  I wondering if the use of this technology would eliminate or reduct the need for tinting which will help reduce the heat and UV energy like what is currently in autos or even new residential windows.

Ann R. Thryft
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Re: Solar-window cells?
Ann R. Thryft   8/22/2012 12:29:10 PM
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Mydesign, we have somewhat similar programs here. The programs still have an initial up-front cost that can be beyond the resources of many people. Other programs with practically zero up-front costs leave the homeowner a renter, or lessor, of the system, not its owner. At least in my state, the offers I've seen from various solar panel installation companies seem to be aimed primarily at people who use electricity for heat. Those of us in rural areas use other sources for heat, and many, like me, are under a forest canopy so there's not a lot of sun.

Mydesign
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Re: Solar-window cells?
Mydesign   8/22/2012 12:59:39 AM
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1 saves
Ann, in our country both federal and state governments are offering 60% (30+30) discount for domestic house hold consumers, how are willing to invest in solar energy as a part of promoting ecco friendly energy sources. So the end customers have to bear only 40% of the cost and can have green energy with minimal investment. Am not sure about other countries, but if they are also able to follow similar policies, then investmental cost may not be a big issue.

Rob Spiegel
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Re: Solar-window cells?
Rob Spiegel   8/20/2012 12:47:15 PM
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Kevin, I agree that much of the potential success of deploying a new technology like these solar windows will depend on the simple economics. There is a certain portion of the population who would invest without a positive economic calculation -- those who buy EVs -- but in most cases, the technology will have to pay for itself.

Ann R. Thryft
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Re: It all comes down to cost..
Ann R. Thryft   8/20/2012 11:40:45 AM
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Rob and Beth, I think that's a good point: this kind of technology may be best applied to large buildings with a much higher ratio of glass surface area to total exterior surface area.

Kevin
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Re: Solar-window cells?
Kevin   8/19/2012 2:50:53 PM
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It's true - we are very "spoiled" by the concentrated energy delivery of today's electricity and natural gas.  Renewable energy sources are by nature more diffuse and present a great challenge in concentrating / converting / storing it.  I think that energy-efficient designs of the future will tap into multiple energy-saving and energy-production sources (passive and active), to acheive an overall energy footprint that makes a difference in our homes.

For example, in Southern California we often pay to have our south-facing windows covered in reflective solar film to keep the home cooler - why not pay a bit more and get the added benefit of a little power?  The key to practicality, of course, will be low enough cost.

I ran a thumbnail "back of envelope" calculation on the economics:  A 1 square meter window can get ~1Kwatt of solar flux in optimum conditions.  Derate for geometry of orientation, let's say 50%.  Let's optimistically use 10 hours of sun for 30 days, and the 4% efficiency of the conversion.  That gives 1.2 KWH of power per square meter of window per month.  At a rate of 14 cents per KWH (my local total rate), that gives a payback of 17 cents per month, or a couple bucks per year (per window)...and that is assuming all sunny days.  Sadly, I don't think this is going to produce a reasonable break-even timeframe, esp. if you include the true time-value of money in the calculation.

So...my intuitive take-away is that for solar energy to become economically viable - one needs to push as hard as possible on reducing cost and increasing efficiency.  Even then, it's a challenge.  To give up a huge amount of efficiency for the novelty of using windows (vs. say on your roof) for solar power does not seem to make economic sense.  Note that my opinion shifted over the course of writing this comment, after I ran the calculations!

Kevin

William K.
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Solar power, smart grid reasons, and hard reality.
William K.   8/17/2012 2:05:50 PM
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Ann, my point is that at least for me, the things that I use that use electric power need a good bit more than small amounts. Even my computer to participate in this discussion and answe all of my daily emails needs quite a few watts. And collecting the power from a dozen windows effectively is not trivial, particularly if one complies with all of the codes, which have no regard concerning the cost of implementation. Of course in a sunny cliamte and in a building designed for maximum efficiency, things could be different. But I don't live in that part of the world.

As for the smart grid, what the main benefit would be is the quick isolation and shedding, of sections that are in a failure mode. Dumping overloaded sections quickly in order to avoid massive failures is the only way to avoid repeating the massive failures of the past. Adding additional capacity will only increase the amount of power sold, since unused capacity provides no return on investment. BUt an effective smart grid, coupled with small enough sections, will be able to shed overloads quickly, avoiding the dreaded ripple effect that caused the past power outages. 

Of course critics will complain that disconnecting overloads is a lot like rationing, which it may indeed be a form of rationing. But sometimes rationing does need to happen.

Ann R. Thryft
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Blogger
Re: It all comes down to cost..
Ann R. Thryft   8/17/2012 12:14:08 PM
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Thanks, that's more or less what I guessed. I think solarizing one's machines is a great idea.

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