----- Original Message ----- From: Lienesch To: Cathy Colwell Sent: Saturday, February 24, 2001 11:15 PM Subject: Re: redone diagram, our interpretation of numbers 1) Micro-inverters are just inverters for a 24V module(s). They're quite simple to install -- it would mount on a module and a cord comes out and plugs into a receptacle. It's not practical for large systems. It's about five times more expensive per watt than a larger HOME sized inverter. For commercial systems it would be even more expensive per watt. It's a perfect starter for guerilla solar. You can use fewer modules but I thought you wanted to make a meaningful impact on a building's electric consumption. 126 modules is more cosmetic than substance for helping supply a building's needs. I would think you would move toward more rather than less. If you wanted a smaller system, we would use single phase grid-tied inverters. Just tell me how large the system is and I can specify an inverter. 2) Modules could be mounted with a 1/2 inch spacing to allow for any thermal expansion. Modules and laminates have the same power rating. We take laminates and add the frame. The glass portion is the same. 3) I'm not sure there is enough information for him to provide cost information. It's lacking detail like how the module's tilt angle is adjusted, what the raceway in which the top support moves looks like, and how are adjacent modules structurally connected across the wall. He may have some industry-standard estimating tools available when detail is not available. For a PV example, thin film gives 5W/square foot and costs $4.50 - $5.50/watt (if I recall correctly). Richard may have his own examples for BIPV. Hope this helps. -Gary- ----- Original Message ----- From: Cathy Colwell To: Lienesch Sent: Saturday, February 24, 2001 8:22 PM Subject: Re: redone diagram, our interpretation of numbers (1) Can you explain about the micro-inverters that were referred to in the last pdf file that I linked on our page? In case 126 windows is too many - the option of using fewer seems like a nice piece of information to include in our presentation. http://www.bpsolar.com/docs/Economic_Optimization_of_BIPV.PDF There are system designs that include the use of micro-inverters, lower cost AC wiring and switch gears for small systems under 100 watts that can be incorporated to help the "startup user." As micro-inverters become more competitive with centralized units, homeowners or small business owners can building systems incrementally by purchasing "trial" PV systems without a major $/Wp penalty. These economics would allow our awnings to be added to existing buildings as needed and give the owner assurances that the piecemeal price not greatly exceed an initial larger voltage central inverter system. (2) We were visualizing an awning as covering only one individual window. If they were to span a larger "collection of windows" how large would the gap be between modules? Are you saying that the laminates can be juxtapositioned with no divisions between them? Is the power production different, or only the framing/support mechanisms? (3) Also, I chose the module because it was already framed. Since I have not heard from Richard, I am not feeling a high level of confidence in acquiring a quote on the framing. Do you think that the current information on our product page http://public.cctt.org/sunlight/components/product.htm is correct enough to get a better reaction from him? Any suggestions? Cathy ----- Original Message ----- From: Lienesch To: Cathy Colwell Sent: Saturday, February 24, 2001 7:02 PM Subject: Re: redone diagram, our interpretation of numbers It looks like you are making great progress! You could string the Millennia modules from six windows to get around 426 Volts (71Vp max * 6). Every six windows/awnings will yield 258 Watts (43W * 6). Depending on how many windows you use will determine the size of the inverter you will use. For example, a 5kW inverter will receive input from: 5000W/0.9/258W = 21 groups connected in parallel of six windows/modules each, that is 126 south-facing windows/modules. This shouldn't be too difficult for a building. Also, the 0.9 is an approximate efficiency for the inverter. You can put in 5000W/0.9 and get the rated 5000W out. Power out of the inverter would be approx. 4.8kWp. I'll have to check the specs of the inverter when I get back to work. As you can see, it takes a lot of area to get 5 kW of power. That would be a lot of Venitian blinds if we went that route. The dimensions you give are for a universal framed module. That would simplify your support structure. However, the modules would have gaps between them. That's probably OK for the project. On a real building, you'd probably want to use laminates (no frame included) and build your own good-looking framing system that hides the unsightly support members as best possible. In your illustration, you could try dropping the walls relative to the suns. It would be good to have the sun bisected by an imaginary line normal to each respective module front surface. That would illustrate the optimum tilt angle as the module in each case would face squarely into the sun. The winter sun currently appears at the horizon relative to the window. That would be true for a polar region. I hope it doesn't happen in Fla any time soon! Keep the questions coming. -Gary- ----- Original Message ----- From: Cathy Colwell To: lienesch@carr.org ; lienesgw@bpsolar.com Sent: Saturday, February 24, 2001 9:10 AM Subject: redone diagram, our interpretation of numbers Gary - you have no idea how confusing all of these numbers are to us. But we did some calculations and have posted our results on the page http://public.cctt.org/sunlight/components/product.htm It seems to us that one MST-43 module is sufficient for each single window (3' x 6' or 4' x 6') or awning. Thus, each awning would have a surface area of 0.8 square meters and produce 43 Wp. Three awnings/modules would produce 200 VDC. But these numbers do not add up to your 480 VDC. I have not written to Trace because I don't understand the numbers that I need to send to them. However we did do some research and have presented our findings on this page. Richard has not answered - probably because my email was so vague. If you could steer us towards the correct query maybe he could help us in time. I am going in to school this morning to work with three students proofreading what has been written on our site for the contest. I should be home by 2 PM. Cathy