HI Allan, I suggest you use Solid State relays.
They come in 12v power voltage and up to 300VDC switched voltage, no arcs, low power draw and more reliable than mechanical relays, just make sure you use a good heat sink. jay peltzpower On Jul 9, 2011, at 7:26 AM, Allan Sindelar wrote: > Phil and Wrenches, > Thank you for the response; good food for thought. > > We looked at Aerovironment as a result of your suggestion, but it appears to > be out of production and unavailable. > > Kent's suggestion to use the gennie starting battery also makes sense, as the > battery would be recharged daily and the load is negligible. I also suspect > that a Morningstar SunLight controller with a small PV module would provide > the daily start/stop signal to the Relay Driver. > > However, as Kent points out, finding a relay would be difficult, as the > customer is looking at controlling multiple (four?) SQF pumps from AC or > their respective arrays. That's too many poles at too high a DC voltage to > prevent arcing - multiple relays with 240V AC coils paralleled would handle > control of the relays, but can anyone suggest a relay that can handle 100-150 > VDC array voltage? MDI mercury contactors, as were used in early APT/Pulse > powercenters, come to mind, available in 1-3 poles. Any better ideas? > > While solutions to some of the issues are workable, ultimately I don't see an > easy way to accomplish what he wants to do. He's talking 10-12 gpm > continuously 24/7. That's 30gpm raised 400' if array-direct, more than any > solar pumps I know can supply. Thus the diesel generator for night operation. > Ranchers are used to diesel generators. > > Allan Sindelar > al...@positiveenergysolar.com > NABCEP Certified Photovoltaic Installer > NABCEP Certified Technical Sales Professional > New Mexico EE98J Journeyman Electrician > Positive Energy, Inc. > 3201 Calle Marie > Santa Fe, New Mexico 87507 > 505 424-1112 > www.positiveenergysolar.com > > > > > On 7/5/2011 6:57 PM, Phil Undercuffler wrote: >> >> Use an ac charger to charge a small battery when the generator runs each >> evening, and then power a timer or photosensor from the battery. Sears, >> <$40. I wouldn't worry about the phantom load of the timer -- you're >> running an 8kW diesel genset throughout the night. It oughta keep up. >> >> The question I can't answer is how this makes sense, with diesel above >> $4/gallon and service every 100 hours. Did you look at an Aerovironment UPC >> controller running array direct with a standard AC pump? >> >> Phil >> ----------- >> "When we learn how to store electricity, we will cease being apes ourselves; >> until then we are tailless orangutans. You see, we should utilize natural >> forces and thus get all of our power. Sunshine is a form of energy, and the >> winds and the tides are manifestations of energy. Do we use them? Oh, no! >> We burn up wood and coal, as renters burn up the front fence for fuel. We >> live like squatters, not as if we owned the property. >> >> There must surely come a time when heat and power will be stored in >> unlimited quantities in every community, all gathered by natural forces." >> -- Thomas Edison -- >> >> >> >> On Tue, Jul 5, 2011 at 4:28 PM, Allan Sindelar >> <al...@positiveenergysolar.com> wrote: >> Wrenches, >> A good client of ours is a rancher in the New Mexico/Arizona border area. He >> has a specific need for which I couldn't offer a simple system. >> >> He needs to raise water from a lake 400+/- vertical feet to a 100K gallon >> storage tank for agricultural use. The site is remote. The amount is >> substantial - about 10-12 gpm continuously, 24/7. He would like to use 4 >> Grundfos SQ Flex pumps at about 2.5-3 gpm, each running array-direct feeding >> a common pipe to the tank. He then wants to use about an 8kW (derated to 6kW >> for 7,500' elevation) diesel generator (with standard two-wire automatic >> start) to run all four pumps when the sun goes down, and shut off and >> transfer back to PV when the sun comes up the next morning. >> >> How might this be done? If we assume that each pump has four 210W modules, >> that would be an 80Vnom array with MPP around 120V and Voc around 150V. I >> would assume that both of these voltages are too high to use any stand-alone >> AGS, such as Atkinson or Magnum. We considered a separate tiny 12V or 24V >> battery with small PV module, used just to power an AGS voltage sense >> signal, with the voltage difference between float (13.6V) and rest (12.7V) >> triggering a voltage-actuated start signal, but rejected this as problematic >> as battery temperatures affected charge voltages. A self-contained time >> switch, such as some of the newer Intermatic units, might work, if the right >> model can be identified and isn't a substantial phantom load. >> >> We would also have to adapt a relay to switch between sources, with a 120 or >> 240 V AC relay coil current, energized by the generator. The Grundfos IO101 >> AC interface unit is manual only. >> >> Has anyone solved this problem? Any ideas for a reasonably simple and >> trouble-free approach would be welcome. >> Thank you, >> Allan >> >> -- >> Allan Sindelar >> al...@positiveenergysolar.com >> NABCEP Certified Photovoltaic Installer >> NABCEP Certified Technical Sales Professional >> New Mexico EE98J Journeyman Electrician >> Positive Energy, Inc. >> 3201 Calle Marie >> Santa Fe, New Mexico 87507 >> 505 424-1112 >> www.positiveenergysolar.com >> >> >> >> >> _______________________________________________ >> 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 >> >> >> > _______________________________________________ > 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 >
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