Folks, I've heard lots of good advice on this subject and as an old off-grid system designer, energy conservation has long been a field I take seriously. Generating power that you wouldn't otherwise need because you refuse to use the power wisely is just... Stupid. Stupid financially and stupid in just about any other category I can think of. To quote some redneck (but funny!) comic, "You can't fix stupid." Like Todd, I've walked away from big money clients who just didn't -and wouldn't- get it. Heresy, I know, in a capitalistic economy. I blame my Hippie roots, but I make no apology for them. We am what we am. That said, I disagree with Eric that excess PV is a waste. At a module price of $6.00/Watt, you bet! At $1.50/W or less to the end user these days, not so much. I live off-grid and have for 40 years. I have what you might consider to be "excess PV" in the air. Ya know, if you don't take it to ridiculous lengths, there really ain't no such thing. During the high season, you will have electrons coming out your ears. As Jay and others have said, use them! Make hot water. Don't need hot water in the summer? Pump some water! Run an evaporative cooler. A freakin' water feature. Whatever. Be creative! Make your clients' lives funner and maybe make a few bucks at that. It's in the early Spring and Late Fall that excess PV really pays for itself. What's the real cost of an hour of generator time? I reckon it's somewhere between $4 and $8/ hour depending on fuel type, size, yada yada. The heavier the consumption, the more those sorta sunny or sorta cloudy PV days count. Even if you saved just 10% of genny time during those periods, do that math. Plus, for whatever that extra PV saves in genny time, the planet thanks you -and them. As a side bene, they don't have to listen to the damn thing. A feature, sell it! I also disagree with his suggestion to do things that "minimizes user interaction" I strive to MAXIMIZE user interaction! My experience shows me that the more the client relates to his/her system, the more reliable it is. That goes triple for generators. "Did I just hear the generator start? Damn, I was gonna check the oil. Ah well, next time." Ya know? I totally understand that some folks will just not pay attention no matter how logical it is or despite your best efforts to explain that. But you have to try. It's an important part of our job and we need to do it. With passion. Ya gotta do what ya gotta do, but those uninvolved folks will be a thorn in your side for a long time. Sooner or later, there is a VERY good chance that they will cost you money. Believe it. Good Luck, bob-O
On Aug 16, 2013, at 2:24 PM, eric.bent...@schneider-electric.com wrote: Hi William, In off grid applications, you want to have sufficient RE to keep up with load demand and only run the generator when RE cannot keep up. However, having too much RE is a waste because it will result in energy not harvested (if regulating), however, diversion controllers can allow the excess energy to be utilized (i.e. water heating). Running the gen up to the bulk level replaces approx 80% of capacity, and maximizes fuel consumption, allowing RE to get the batteries charged the last 20%. Automatic gen start capability with staggered start voltages allow you to target 50% discharge more accurately, and minimizes user interaction. Try to calculate the total daily kWhrs and match the demand with RE as closely as possible. Hope that helps, Rgds, _____________________________________________________________________________________ Eric Bentsen | Schneider Electric | Solar Business | UNITED STATES | Technical Support Representative Phone: +(650) 351-8237 ext. 001# | Email: eric.bent...@schneider-electric.com | Site: www.schneider-electric.com/solar | Address: 250 South Vasco Rd., Livermore, CA 94551 <Mail Attachment.jpeg> *** Please consider the environment before printing this e-mail From: Jay Peltz <j...@asis.com> To: RE-wrenches <re-wrenches@lists.re-wrenches.org> Date: 08/16/2013 02:01 PM Subject: Re: [RE-wrenches] PV Assist Sent by: re-wrenches-boun...@lists.re-wrenches.org Hi William Thx helps a lot. I can only say how I do it. I'll give the client some options, including the change of appliances and usually the price difference makes the sale one way or the other. Funny reminds me of the old days, only with much smaller loads/$. Good luck Jay Sent from my iPhone On Aug 16, 2013, at 12:49 PM, "William Miller" <will...@millersolar.com> wrote: Jay: There are four systems in question. In three the loads are year round and one is summer only AC loads. The year round loaded systems have loads day and night. One is a highway maintenence station with at least 4 residences. One is a family compound with two homes with electric ranges, water heaters, AC units (I know its stupid, lord knows I've tried to convince them to change appliances.) One is an animal rescue operation with heater loads. One is a large home with 5 very small, very new, very sophisticated and frugal AC units I know it is silly to move these loads off-grid, but people do it and they will hire someone to work on the systems. It may as well be me, doing the best I can to use the resources as wisely as possible. William PS: It always happens like this: I get a call from a client with problems. Well, of course their expensive battery bank died and it died because of wasteful appliances. The prescription is a new, expensive battery bank and, at the same time, new, expensive, efficient appliances. They complain can't afford both and they have to have the batteries, so that is what they get. Repeat every two years. Sad.... Wm From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jay Peltz Sent: Friday, August 16, 2013 12:22 PM To: RE-wrenches Subject: Re: [RE-wrenches] PV Assist Hi William I feel it's impossible to discuss without more specifics. For example if the extreme loads are only every ( just run the genny) so often vs seasonal ( maybe AC coupling makes more sense vs cycling a extremely expensive battery 4 x day), vs year round vs what is do able etc I would be curious to know what some of the parameters are, as I'm sure others as well Jay Peltz power. Sent from my iPhone On Aug 16, 2013, at 10:53 AM, "William Miller" <will...@millersolar.com> wrote: Friends: We have been receiving a flurry of requests for design of off-grid systems where the loads are enormous, relative to normal off-grid requirements. It is obvious that the size of PV and battery arrays to power these loads is beyond what is practical. We have dubbed these systems Generator/battery with PV assist, or PV assist for short. These systems will cycle batteries multiple times per day. It is my understanding that the extra battery cycels will shorten battery life. Since generator run is expected, we are willing to increase generator run time in order to prolong battery life. The parameters I suggest are an aggressive load start and a very high battery start parameter. This will prevent deep discharge of the battery bank. I know shallow discharge is not the norm, but I don't believe shallow cycling is a problem as long is it as at the top of the voltage window, i.e. the batteries achieve absorption at least once per day. We know a load start ciuld result in an abbreviated run time, curtailing absorption period, but we are assuming there will be a battery votage start at least once per day allowing full absorption. Has anyone else considered these issues, and what conclusions did you make I am looking forward to a spirited discussion as usual. I throuroughlyenjoy and beneift from them, even thought the advice is usually conflilcting. Thanks in advance. William Miller _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address & 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 Change email address & 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 ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. _____________________________________________________________________________________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address & 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 Change email address & 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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