HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
Beth Stackpole
User Rank
Blogger
Another reason windows key to energy bill savings
Beth Stackpole   8/15/2012 8:34:33 AM
NO RATINGS
If these solar cells can really be effective in generating electricity--and consquently saving lots on an energy bill--what a boon for consumers. I would hope that if the technology reaches the commercialization stage that the makers offer both windows with the technology baked in, but also some sort of upgrade or modification kit for those of us who own homes and don't want to go through the expense of subbing out existing windows for new models. That is a major, major project.

Ann R. Thryft
User Rank
Blogger
Re: Another reason windows key to energy bill savings
Ann R. Thryft   8/15/2012 12:20:47 PM
NO RATINGS
I wouldn't mind having those windows, either, even here in the woods. There are various types of films that can be added to windows that purport to do something similar. Here are some recent ones: http://www.pcworld.com/article/241152/3m_film_turns_windows_into_transparent_solar_panels.html http://cleantechnica.com/2012/07/06/39893/ http://www.newenergytechnologiesinc.com/technology/solarwindow

williamlweaver
User Rank
Platinum
Re: Another reason windows key to energy bill savings
williamlweaver   8/15/2012 2:08:05 PM
NO RATINGS
Wikipedia has a nice article on Photosynthetic efficiency
 
It's sources report the following efficiencies for conversion of sunlight into biomass (usable energy)
 
Plants 0.1% - 2 %
Crops 1% - 2%
Sugarcane 7% - 8%
 
At 4%, this device is on the high-side when compared to energy-harvesting bio-fuels. With even more development, this material could be quite a winner -- and we could continue to use our corn and soybeans to feed people and livestock rather than engines...


Ann R. Thryft
User Rank
Blogger
Re: Another reason windows key to energy bill savings
Ann R. Thryft   8/16/2012 12:25:29 PM
NO RATINGS
Thanks, williamlweaver. Many readers don't realize how low solar efficiency conversion rates are in terms of percentages.

Scott Orlosky
User Rank
Platinum
Re: Another reason windows key to energy bill savings
Scott Orlosky   8/15/2012 4:10:56 PM
NO RATINGS
This is a really cool development.  The real key (costs aside) will be integration of "power windows" into a local smart grid. In this case local would mean within the confines of the building that the windows are installed in.  What a great way to harvest power for low voltage lighting, though.

Ann R. Thryft
User Rank
Blogger
Re: Another reason windows key to energy bill savings
Ann R. Thryft   8/16/2012 12:26:13 PM
NO RATINGS
I don't think a smart grid is needed. Some of the original solar power designs in the 70s were passive: the power generated is used by the building that generates it. You don't need a smart grid to do that.

mrdon
User Rank
Gold
Re: Another reason windows key to energy bill savings
mrdon   8/15/2012 4:35:08 PM
NO RATINGS
Beth.

I agree with you totally. This idea of adding solar cell polymer material to windows is the best one yet for generating electricity. With the amount of sunlight passing through windows daily, I would imagine sufficient amounts of electricity can be generated easily. The next item to include in the energy conversion process is an innovative way to store the energy for use on cloudy days.

Ann R. Thryft
User Rank
Blogger
Re: Another reason windows key to energy bill savings
Ann R. Thryft   8/16/2012 12:28:35 PM
NO RATINGS
All kinds of passive storage methods have been developed, many of them in the 70s and 80s, some more recently, Most of them derive from building designs that are thousands of years old. This is not new technology.

Charles Murray
User Rank
Blogger
Re: Another reason windows key to energy bill savings
Charles Murray   8/15/2012 6:37:50 PM
NO RATINGS
Energy harvesting technologies are well-known to produce really tiny amounts of electrical current -- at the microamp- and even nanoamp-level in some cases. Any idea how much these films could produce, Ann?

Ann R. Thryft
User Rank
Blogger
Re: Another reason windows key to energy bill savings
Ann R. Thryft   8/23/2012 2:54:54 PM
NO RATINGS
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).

kf2qd
User Rank
Platinum
It all comes down to cost..
kf2qd   8/15/2012 12:23:32 PM
NO RATINGS
At 4% efficiency, and a practical application on the south side of office buildings, cost is going to be the deciding factor. Let's hope that taxpayers don't get stuck funding this as the total outpput could be rather restricted.

tekochip
User Rank
Platinum
Re: It all comes down to cost..
tekochip   8/15/2012 4:44:14 PM
NO RATINGS
I agree entirely.  With a consumer grade cell at 15%, a 4% cell that will probably not be properly aligned is going to need to be fairly cheap.  Don't get me wrong, I love solar, I even converted my lawn mower to solar.  The idea of a window that still functions as a window while collecting solar energy is fantastic, but if each window only collects 1Wh for a sunny day, the window will need to be as cheap as glass.


Rob Spiegel
User Rank
Blogger
Re: It all comes down to cost..
Rob Spiegel   8/15/2012 5:59:46 PM
NO RATINGS
I would guess the most efficient use of this technology would be on high-rise office buildings. The tall buildings have acres of windows, far more per square foot than a private residence.

Beth Stackpole
User Rank
Blogger
Re: It all comes down to cost..
Beth Stackpole   8/16/2012 8:44:36 AM
NO RATINGS
Commercial buildings would be a great application and these mega buildings also have some sort of budget which would allow them to invest in the storage capabilities that are so critical to making this effective. Especially since many mega buildings in cities (I'm thinking NYC) have lots of self-induced shade due to their size and number--a factor that could limit the windows' ability to harvest energy even on sunny days.

Rob Spiegel
User Rank
Blogger
Re: It all comes down to cost..
Rob Spiegel   8/16/2012 10:29:39 AM
NO RATINGS
I agree, Beth, the large buildings have the scale. A small savings per window would deliver significant power. In a dense area like Manhattan, there may be some limitations on direct sunlight, but around most of the country, these large buildings are pretty clear of obstruction.

Ann R. Thryft
User Rank
Blogger
Re: It all comes down to cost..
Ann R. Thryft   8/20/2012 11:40:45 AM
NO RATINGS
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.

kodaiflow
User Rank
Bronze
Re: It all comes down to cost..
kodaiflow   12/6/2012 12:03:27 PM
NO RATINGS
I think the main question is mean life span.  This currently is the largest draw back to PV in it's current form.  If these units can produce power for 30 years at a constant level then they justify the investment.  The average solar panel that people are rushing to put on their roofs will have a life span (90% of peak) of about 10 years. In that time they may only generate 50% of the energy used to fabricate them. 

Ann R. Thryft
User Rank
Blogger
Re: It all comes down to cost..
Ann R. Thryft   12/6/2012 12:19:55 PM
NO RATINGS
Good point, kodaiflow. Like many alternative energy technologies, especially those taking advantage of existing semiconductor infrastructure, the big push has been to make the technology a) work efficiently and b) be manufacturable. I wonder how much LCA studies have been done--that would be really interesting to know, although there may also not be enough data yet.

Ann R. Thryft
User Rank
Blogger
Re: It all comes down to cost..
Ann R. Thryft   8/17/2012 11:38:55 AM
NO RATINGS
tekochip, you converted your lawn mower to solar?! Please tell us how.

tekochip
User Rank
Platinum
Re: It all comes down to cost..
tekochip   8/17/2012 12:10:12 PM
NO RATINGS
Not much to it, really.  I took an off the shelf electric mower and added some panels to charge batteries.  I've since replaced the very heavy SLA cells with a 10AH NiMh pack, and that makes the machine much easier to navigate.  It takes about three good days to recharge the cells, so sometimes I mow on a particular day to make sure I get a good solar harvest.

Ann R. Thryft
User Rank
Blogger
Re: It all comes down to cost..
Ann R. Thryft   8/17/2012 12:14:08 PM
NO RATINGS
Thanks, that's more or less what I guessed. I think solarizing one's machines is a great idea.

William K.
User Rank
Platinum
Solar-window cells?
William K.   8/16/2012 9:55:46 PM
NO RATINGS
This is an interesting concept indeed. But aside from the discussions about relative efficiency, how much useful power is a window-cell going to produce? Then, consider the logistics of transporting the power from a window that can open, because some folks do open windows for ventillation at times. Finally, consider the expense of the hardware needed to convert whatever power is produced to a voltage-current level that can actually be useful.

My whole point is that what we have here is an interesting developement that may not be "worth the effort" to implement it. At that point it becomes valid to question how much effort and resources should be expended in that direction.

Mydesign
User Rank
Platinum
Re: Solar-window cells?
Mydesign   8/17/2012 4:45:01 AM
NO RATINGS
1 saves
William, all the natural energy conservation methods require a little bit upfront investment and we can have a fair ROI in long term. The immediate ROI is less because, we are using the generated power for domestic use and it has to be calculated according to the tariff sheet provided by the local energy distributor. I had done a similar calculation before going for solar power to my house and it found that it will take minimum 20 years for cover up the initial investment cost. But have the proud that am using natural resources and no need to worry about tariff hike or power cuts.

Ann R. Thryft
User Rank
Blogger
Re: Solar-window cells?
Ann R. Thryft   8/17/2012 11:44:26 AM
NO RATINGS
I agree with Mydesign about the investment in active PV solar being worth it over the long run. However, homeowners have to be able to afford the several thousands of dollars investment and not everyone can do it. Regarding solar panel thickness, yes, that's one of the whole points of this project.

Mydesign
User Rank
Platinum
Re: Solar-window cells?
Mydesign   8/22/2012 12:59:39 AM
NO RATINGS
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.

Ann R. Thryft
User Rank
Blogger
Re: Solar-window cells?
Ann R. Thryft   8/22/2012 12:29:10 PM
NO RATINGS
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
User Rank
Platinum
Re: Solar-window cells?
Mydesign   8/24/2012 1:13:30 AM
NO RATINGS
1 saves
Ann, in the scheme which I mentioned, the upfront cost is only 40% of the total cost and the rest is a subsidy from government, which goes directly to the service provider’s account. So customer has to pay only 40% of total cost, that too in interest free installments (2-6 EMI based on various schemes from different companies).

Ann R. Thryft
User Rank
Blogger
Re: Solar-window cells?
Ann R. Thryft   8/24/2012 12:29:24 PM
NO RATINGS
Mydesign, that does resemble some US programs. However, because the cost of installing solar can be around $20,000 (depending on several variables), an often-quoted figure, "only" 40% would be $8,000. Not many people have that amount available for this purpose, even in installments.

Mydesign
User Rank
Platinum
Re: Solar-window cells?
Mydesign   9/4/2012 1:14:28 AM
NO RATINGS
1 saves
Ann, that’s surprising for me. I though all US citizens are financially well settled peoples. As far as my knowledge, the per capital income of US citizens are more than 10 times of Indian citizens. Through my previous post, I mentioned about the government initiatives for promoting solar energy.

Ann R. Thryft
User Rank
Blogger
Re: Solar-window cells?
Ann R. Thryft   9/4/2012 12:23:04 PM
NO RATINGS
Mydesign, your impression is incorrect. The US has been experiencing a major economic downturn for several years, including many people losing their jobs and their homes. Also, per capita average income figures are highly misleading, since a given dollar amount often buys much less here than it does in India. Classic examples are the costs for surgery and prescription drugs. In any case, it's a complex picture, especially when making comparisons.

Jack Rupert, PE
User Rank
Platinum
Re: Solar-window cells?
Jack Rupert, PE   8/22/2012 1:34:10 PM
NO RATINGS
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
User Rank
Blogger
Re: Solar-window cells?
Ann R. Thryft   8/23/2012 12:09:02 PM
NO RATINGS
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
User Rank
Platinum
Re: Solar-window cells?
Jack Rupert, PE   8/24/2012 9:58:50 AM
NO RATINGS
Ann, do you know how that compares with your standard high-efficiency home or office window?  Just thinking that if this has similar optical properties, there might be a savings in the base cost of the glass that would normally by used (by reducing the amount of "doping chemicals" which would help in the implementation of soemthing like this.

Ann R. Thryft
User Rank
Blogger
Re: Solar-window cells?
Ann R. Thryft   8/27/2012 12:00:55 PM
NO RATINGS
Jack, can you clarify your question: do you mean eliminating the doping chemicals that are usually used to increase efficiency and replacing them with this film?

Jack Rupert, PE
User Rank
Platinum
Re: Solar-window cells?
Jack Rupert, PE   8/31/2012 11:30:25 AM
NO RATINGS
Yes, Ann, that's what I was wondering.  I don't know the proper percentages, but say an average high effieciency window block 65% of a certain type of energy (heat, uv, whatever).  If the solar cells take out 25% by themselves, that might mean that the cost of the base window could be reduced by eliminating an amount of the doping, and thereby helping to offset some of the cost of the solar cells.

Ann R. Thryft
User Rank
Blogger
Re: Solar-window cells?
Ann R. Thryft   9/4/2012 12:24:11 PM
NO RATINGS
Thanks, Jack, for the clarification. I think that's an excellent question for a solar cell or window manufacturer.

Ann R. Thryft
User Rank
Blogger
Re: Solar-window cells?
Ann R. Thryft   8/17/2012 11:52:08 AM
NO RATINGS
William, windows may not generate a lot of power on their own. But with conventional electricity produced by fossil fuels, we have been conditioned to think of only a single power source technology. With alternative energy sources, the idea is often to combine different power sources and with multiple energy inputs. I've become more aware of that mix living out in the forest with electricity for lights and powering the ceiling fan (for cooling and heating), a woodstove for heat, and propane for hot water. So the idea of getting energy in a single building from solar and wind, for instance, and from window films plus panels on the roof, or those plus passive solar collection methods, makes sense.

Kevin
User Rank
Platinum
Re: Solar-window cells?
Kevin   8/19/2012 2:50:53 PM
NO RATINGS
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

Rob Spiegel
User Rank
Blogger
Re: Solar-window cells?
Rob Spiegel   8/20/2012 12:47:15 PM
NO RATINGS
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.

Mydesign
User Rank
Platinum
Thin Solar panel
Mydesign   8/17/2012 4:34:08 AM
NO RATINGS
1 saves
Ann, the normal Solar panels are of thick in size and it cannot be used other than fix in terrace of buildings. If the thickness is less and of comfortable size, they can be fixing in outside walls and window doors. So most of the people may prefer and in turn more natural energy can be produced.

William K.
User Rank
Platinum
Solar power, smart grid reasons, and hard reality.
William K.   8/17/2012 2:05:50 PM
NO RATINGS
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.



Partner Zone
Latest Analysis
Adam Berger hacked a computer keyboard into a mini key-tar to play with his band.
Altair has released an update of its HyperWorks computer-aided engineering simulation suite that includes new features focusing on four key areas of product design: performance optimization, lightweight design, lead-time reduction, and new technologies.
At IMTS last week, Stratasys introduced two new multi-materials PolyJet 3D printers, plus a new UV-resistant material for its FDM production 3D printers. They can be used in making jigs and fixtures, as well as prototypes and small runs of production parts.
In a line of ultra-futuristic projects, DARPA is developing a brain microchip that will help heal the bodies and minds of soldiers. A final product is far off, but preliminary chips are already being tested.
If you're planning to develop a product that uses a microcontroller, you'll want to take note of next week's Design News Continuing Education course, "MCU Software Development – A Step-by-Step Guide."
More:Blogs|News
Design News Webinar Series
9/10/2014 11:00 a.m. California / 2:00 p.m. New York
7/23/2014 11:00 a.m. California / 2:00 p.m. New York
7/17/2014 11:00 a.m. California / 2:00 p.m. New York
6/25/2014 11:00 a.m. California / 2:00 p.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Sep 22 - 26, MCU Software Development – A Step-by-Step Guide (Using a Real Eval Board)
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Next Class: September 30 - October 2
Sponsored by Altera
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service