Hi Allan, While you want to get as close as you can on voltage, look at the actual power mismatch loss and you can use current modules with very little loss. I looked at Suntech 175s because that is what we stock. The voltage with 9 or 10 modules was either 6% low or 4% high. If your Vmp is 5% off between strings, the actual power mismatch for the array will be less than 2%.
Cary Cary Lane Energy Concepts Corporation HC 68 Box 11AA Sapello, NM 87745 Ph: 505-454-0614 ext 4 Toll Free: 877-765-2713 Fax: 505-213-0985 Email: [email protected] Web page: www.energyconcepts.net ----- Original Message ----- From: Allan Sindelar To: RE-wrenches Sent: Thursday, February 18, 2010 8:07 AM Subject: [RE-wrenches] Grid-Tie Upgrade Problem Fellow Wrenches, One of our first batteryless grid-tied installations needs an upgrade and I need to ask this list for suggestions re how it might be done. In late 2001 we installed two poles in the ground at a home. On one pole we mounted ten BP SX120s on a dual-axis Wattsun tracker. Input fed an SMA SB2500 inverter. The idea was that we would install 1/2 of the system then (what the customer could afford), with the infrastructure in place to add a second tracked array later. The system has worked flawlessly since then. Nine years (!) later the customer wants to add to the system, and I'd like to use the original approach if at all possible. We can fit up to around 1500 watts onto the existing inverter, but it must be in the form of ten 72-cell modules of similar Vmp, temperature deration coefficient, and fill factor. I am imagining ten 150W 24Vnom polycrystalline modules, but I don't know of any currently made. I thought it would be easy - ten Kyocera KC130s or KD135s, until a coworker pointed out that these are 12V modules - duh... Any suggested solutions out there? Thank you, Allan -- <![endif]--> Allan Sindelar [email protected] NABCEP Certified Photovoltaic Installer EE98J Journeyman Electrician Positive Energy, Inc. 3201 Calle Marie Santa Fe, New Mexico 87507 505 424-1112 www.positiveenergysolar.com
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