----- Original Message ----- 
From: Lienesch, Gary W. (BP Solar) 
To: 'Cathy Colwell' 
Sent: Monday, February 19, 2001 9:02 AM
Subject: RE: Mainland High School Project (Round #6) - Our product


Hello!
-----Original Message-----
From: Cathy Colwell [mailto:colwell@mindspring.com]
Sent: Monday, February 19, 2001 8:31 AM
To: Lienesch, Gary W. (BP Solar)
Subject: Mainland High School Project (Round #6) - Our product


Gary - I am working all day today on this project with my kids on line. Thank-you for your reply to round #4 ... we will work on incorporating the information into the project. (our current development site is http://public.cctt.org/sunlight )

Last night, two of my students and I thought of a "twist" ... do you think this would be possible?

There are smart windows that change transparency with temperature that need a DC power source to make the conversions - I do not know the exact voltage/wattage required. A PowerView cell supplies DC voltage.
[Gary Lienesch] I think you are referring to liquid crystal.  I believe someone makes such a product for windows.  The current consumption is tiny -- microamps to milliamps.  That's why they are used for watches and other battery-powered displays. 

However, could we recommend a self-contained window that incorporates these two technologies?

Our "window" would be like a stained-glass window ... 

(1) part of it - perhaps around the edges - would be "colored" with the thin-film cells (their grid lines literally looking like the solder-lines of stained glass)
[Gary Lienesch] That is a lot of overhead for a small amount of PV. That's like setting up a phone company for a dozen telephones.  Yes, it could be done.  You should avoid custom modules for cost and external certification reasons.  You'll be spending a dollar to gain a penny.

(2) the center would be a smart window with the voltage required to facilitate the transparency changes being supplied by the PV cell
[Gary Lienesch] The power required for the smart window (liquid crystal) is very small. PV would be an expensive way to provide it.  Better to just use the grid.  If you want to generate power from the sun, it shouldn't be a casual aside.  Do it in a major way.

My understanding of smart windows is that they are "temperature" dependent - heating and cooling; while, PV are dependent on insolation values, or "radiation" depedent.  Can these be linked together?[Gary Lienesch]   The smart windows get a control signal from some source like a PC board with a small computer on it.  It could accept temperature as one input.  You want your PV making power whenever possible without regard to whether the smart window want the power or not.

Any excess electricity from the PV cells could be stored for later use  - assuring a room with proper lighting 24/7.[Gary Lienesch]   I would say use the grid for storage. (Put it in now, withdraw some out later.) However, There would be no excess electricity.  Your building would consume it before it ever hit the grid. 

I hope that you see some promise (or at least nothing unreasonably impossible) in our scheme. The contest requires that we submit something "new." We have not found this "window" anywhere.
[Gary Lienesch] I hope you don't mind my criticism of brainstorming ideas.  I don't like my brainstorming ideas criticized during a session.  However, time is short so I wanted to save you some time.  Everything you suggest can be done.  It's doubtful that anyone would pay to have it built is some cases.  That's why it's good to consider the economics of the proposal.  (Sure, one could build a solar-powered car.  But they could only be used to cross Death Valley or a paved road in the Australian Outback.  It goes back to practicality and economics - cost vs. benefit.)  

Also consider simple and clever.  Simple = cheap to implement.  

With fingers crossed!
Cathy