Interesting abstract. One thing that struck me was the lack of measured data on power production (if that indeed is the object of this study). I guess one can infer the Pmp from "the short circuit current (Isc ), the open circuit voltage (Uoc ) and the cell temperature (T) of each cell". I also wonder how often the data points were recorded. With the general availability of micro-inverters, their use would have been a better choice.
In the final analysis, if the data is sound, the result may only apply to Hannover (high latitude and low-insolation) and similar sites. How orientation-dependent is indirect radiation? It would be great if we could read the whole article... - Peter Peter T. Parrish, Ph.D., President California Solar Engineering, Inc. 820 Cynthia Ave., Los Angeles, CA 90065 CA Lic. 854779, NABCEP Cert. 031806-26 peter.parr...@calsolareng.com Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885 ________________________________________ From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of North Texas Renewable Energy Inc Sent: Saturday, February 19, 2011 8:04 PM To: RE Wrenches Subject: [RE-wrenches] Array tilt angle doesn't matter? At least that's the conclusion of Gottfried Wilhelm Leibniz. "The largest difference of the [PV] plant yield was less than 6% for tilt angles between 0° and 70°." This begs the question, where did the notion that tilt to latitude is critical come from. Surely NREL or someone else has tested this concept before. Anyway if N-S angle energy production loss is only 6% to +/-35° then E-W should be too, right? But it's not. Here's why. If you measured irradiance at 10°-70° only at noon over 12 months, the air mass would at its minimum during the entire test and so irradiance deviation would be too. AM would not be constant at +/- 35° E-W which has been verified by NREL and others for a long time, AM increases the further from solar noon the sun gets. But if the Earths tilt is 23.5 degrees and Gottfried measured to 35 degrees, the difference is 11.5 degrees at summer and winter solstice. And if your array angle is +/- 11.5 deg from true south, rule of thumb is that irradiance losses are minimal. Maybe only 6% or so. This puts the significance of array tilt in a whole new light. Pun intended... Of course there is a fee to download the entire document but the abstract is here http://tinyurl.com/4zf2syk http://www.scopus.com/record/display.url?eid=2-s2.0-78951495350&origin=inwar d&txGid=kX6CkwoH_w_VL01NbmaciIC%3a2 Jim Duncan North Texas Renewable Energy _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org 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
