Laserfiche WebLink
Page 3 <br /> Energy City Commission Minutes <br /> December 21,2011 <br /> Ms. Deckert questioned whether any of the downtown businesses are involved in Project <br /> • Conserve. Chair Zehringer commented that there are a couple of businesses interested but there <br /> is no certification program for commercial audits so the auditors are not "official" commercial <br /> auditors. Discussion followed regarding differences between residential and commercial audits. <br /> Different equipment is necessary for commercial audits. Commissioner Setterholm shared that <br /> commercial audits through Centerpoint Energy are done by engineers. Downtown businesses <br /> may receive an energy "walk through" versus "audit". <br /> 8. Photovoltaic Discussion — Scott Hagen <br /> Commissioner Hagen discussed a concept with micro-inverters that monitor energy consumption <br /> and production regarding solar (photovoltaic) systems. He stated that there is direct current (DC) <br /> at the panel and alternating current (AC) output at the inverter. The output is then sent directly to <br /> the electrical grid. <br /> The set up Commissioner Hagen discussed involves one micro-inverter per 60 cell panel which <br /> essentially makes each panel its own array so that they can operate at optimum efficiency. <br /> He explained that with a central or string inverter, the array is only as efficient as its weakest panel <br /> so if one panel is functioning at less than 100% (for example if a leaf falls on the panel), they all <br /> function to that new, lower level (rather than only the panel with the issue being at lower <br /> efficiency). <br /> Currently there is only one known Enphase micro-inverter grid-tied system to Elk River Municipal <br /> Utilities in Elk River (north of town). Discussion followed regarding companies that are working on <br /> • AC arrays, load factors, and future costs of electricity due to old coal plants being closed. <br /> Panel costs as well as inverter costs are coming down. Commissioner Hagen commented that <br /> passive systems do help conserve energy. On the wholesale side, cost is below two dollars per <br /> watt. It was commented that the cheapest rates seen for installed (central inverter) systems is <br /> $7/watt. <br /> Further discussion followed regarding system sizes. China is planning a 2-gigawatt solar <br /> photovoltaic system. The largest in the United States is in Arcadia, Florida (25 Megawatts). <br /> Commissioner Hagen answered questions regarding the micro-inverter approach. He stated that <br /> each one syncs to the grid system and they are powered by the generated DC voltage, but require <br /> AC voltage present to function (booting up at 24 volts DC, then warming up and starting) so if the <br /> electricity goes out, the inverters de-energize and go dormant. The micro-inverters are purely grid- <br /> tie and do not lend themselves to a battery storage system like the DC central inverter projects. <br /> Micro-inverters cost between $130 - 150 each and are warranted to 20 — 25 years. A comment <br /> was made that rebates artificially keep the costs high but do help keep the industry going. <br /> Elk River Dave Raymond installed a 4 KW system for $45,000 (with rebates). A comment was <br /> made that on a 4 KW system, a person would not want to have an electric stove, water heater, or <br /> dryer. <br /> • 9. Other <br /> No other topics were discussed. <br />