Mind giving away your selected module? Or at least module Voc and Vmp with temp coefficients?
Phil Schneider Creative Energies On Mon, Dec 7, 2009 at 10:28 PM, Jeff Yago <[email protected]> wrote: > We are completing an institutional solar project about 120 kW going on a > large parking deck. The large spans require some really large beams to > support the multiple rows of modules since support columns are as much as 60 > feet apart. In other words, adding more modules to each multiple row is a > really big structural issue and they are at the limit now. > > However, no matter how we design the strings, the number of modules in each > row can only be divided by 12 and multiples of 12 which is the only > combination of modules per string that also works with the number of modules > per row, the number of rows per system, and the number of modules stacked > N-S related to shading issues between rows. However,the inverter > manufacturer wants 13 modules per string to avoid low voltage cutoff on hot > summer days. if I go to 13 modules per string, I am really hitting voltage > max during average cold days and believe me, this site will see more cold > and snow days (reflections) with temperatures far below average winter > temperatures, then it will have hot summer days. The summer average > temperature is 83 degrees and I calculate the minimum array voltage is still > over 316 volts, on a 480 VAC 3 phase inverter. > > Since by both structurally and module count, there is no way we can > increase row lengths to provide 13 module strings, and we cannot reduce > modules per row to achieve 13 module strings as this would make the system > far below what the client expects in system capacity. > > Weather data for this location indicates it exceeds our summer design > temperature by onlyv60 hours total per year, and no doubt most of these > hours occur near the late afternoon at the end of a solar day. > > Whats the best way to deal with this less than ideal combination of string > sizes since we are getting nailed at both ends - too few modules per string > can shut down inverters when hot summer days drop module voltages, and too > many modules per string can do some real high voltage damage on a very cold > sunny day with a foot of snow on the ground. > > What say yea? > > Jeff Yago > > _____________________________________________________________ > Netscape. Just the Net You Need. > _______________________________________________ > List sponsored by Home Power magazine > > List Address: [email protected] > > Options & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org > >
_______________________________________________ List sponsored by Home Power magazine List Address: [email protected] Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
