I do not agree. However I can not disagree with such logic. I hve done some demand reduction, and I am doing some more. I did not say it was easy. In fact it is hard, it is expensive, and in my area the energy saving for solar for anyone on the general service rate (demand billing) is a fool to invest on a ROI basis. HOwever if the demand can be reduced in my area it is more valuable than the saving from energy reduction. My present customer has a load factor of 10% I am studing this load profile on a fifteen minute recorder. I hope to in about 2 weeks have enough data to make my predition as to energy saving from the solar with demand reduction As a note, I do not need to see the future, but the use structure has to be known, so as matt says the unlikley day does not show up and ruenin the month. Indeed not all buildings can be demand reduced. It is possible the "electricity use profiles" in your location is different from Minnesota, . Darryl --- On Fri, 3/19/10, Matt Lafferty <[email protected]> wrote:
From: Matt Lafferty <[email protected]> Subject: Re: [RE-wrenches] Demand Charge Reduction by PV To: "'RE-wrenches'" <[email protected]> Date: Friday, March 19, 2010, 2:26 PM _filtered #yiv1389061065 { font-family:Arial Narrow;} _filtered #yiv1389061065 { font-family:Palatino Linotype;} _filtered #yiv1389061065 {margin:1.0in 1.25in 1.0in 1.25in;} #yiv1389061065 P.MsoNormal { MARGIN:0in 0in 0pt;FONT-FAMILY:"Times New Roman";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 LI.MsoNormal { MARGIN:0in 0in 0pt;FONT-FAMILY:"Times New Roman";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 DIV.MsoNormal { MARGIN:0in 0in 0pt;FONT-FAMILY:"Times New Roman";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 H1 { TEXT-ALIGN:justify;MARGIN:12pt 0in 3pt;FONT-FAMILY:Arial;COLOR:navy;FONT-SIZE:16pt;FONT-WEIGHT:bold;} #yiv1389061065 H3 { MARGIN:6pt 0in 0pt;FONT-FAMILY:Arial;LETTER-SPACING:-0.5pt;COLOR:windowtext;FONT-SIZE:12pt;FONT-WEIGHT:normal;} #yiv1389061065 A:link { COLOR:blue;TEXT-DECORATION:underline;} #yiv1389061065 SPAN.MsoHyperlink { COLOR:blue;TEXT-DECORATION:underline;} #yiv1389061065 A:visited { COLOR:blue;TEXT-DECORATION:underline;} #yiv1389061065 SPAN.MsoHyperlinkFollowed { COLOR:blue;TEXT-DECORATION:underline;} #yiv1389061065 P { FONT-FAMILY:Arial;COLOR:navy;MARGIN-LEFT:0in;FONT-SIZE:10pt;MARGIN-RIGHT:0in;} #yiv1389061065 P.alist { MARGIN:0in 0in 0pt 0.5in;FONT-FAMILY:"Times New Roman";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 LI.alist { MARGIN:0in 0in 0pt 0.5in;FONT-FAMILY:"Times New Roman";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 DIV.alist { MARGIN:0in 0in 0pt 0.5in;FONT-FAMILY:"Times New Roman";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 P.ahead3 { MARGIN:6pt 0in 0pt;FONT-FAMILY:Arial;LETTER-SPACING:-0.5pt;COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 LI.ahead3 { MARGIN:6pt 0in 0pt;FONT-FAMILY:Arial;LETTER-SPACING:-0.5pt;COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 DIV.ahead3 { MARGIN:6pt 0in 0pt;FONT-FAMILY:Arial;LETTER-SPACING:-0.5pt;COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 P.StyleaparaJustifiedAfter0pt { TEXT-ALIGN:justify;MARGIN:0in 0in 0pt;FONT-FAMILY:"Arial Narrow";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 LI.StyleaparaJustifiedAfter0pt { TEXT-ALIGN:justify;MARGIN:0in 0in 0pt;FONT-FAMILY:"Arial Narrow";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 DIV.StyleaparaJustifiedAfter0pt { TEXT-ALIGN:justify;MARGIN:0in 0in 0pt;FONT-FAMILY:"Arial Narrow";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 P.alistnead { MARGIN:0in 0in 0pt;FONT-FAMILY:Arial;COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 LI.alistnead { MARGIN:0in 0in 0pt;FONT-FAMILY:Arial;COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 DIV.alistnead { MARGIN:0in 0in 0pt;FONT-FAMILY:Arial;COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 P.anumlist { MARGIN:0in 0in 0pt;FONT-FAMILY:"Times New Roman";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 LI.anumlist { MARGIN:0in 0in 0pt;FONT-FAMILY:"Times New Roman";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 DIV.anumlist { MARGIN:0in 0in 0pt;FONT-FAMILY:"Times New Roman";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 P.aHead1 { TEXT-ALIGN:center;MARGIN:0in 0in 6pt;FONT-FAMILY:Arial;COLOR:navy;FONT-SIZE:16pt;FONT-WEIGHT:bold;} #yiv1389061065 LI.aHead1 { TEXT-ALIGN:center;MARGIN:0in 0in 6pt;FONT-FAMILY:Arial;COLOR:navy;FONT-SIZE:16pt;FONT-WEIGHT:bold;} #yiv1389061065 DIV.aHead1 { TEXT-ALIGN:center;MARGIN:0in 0in 6pt;FONT-FAMILY:Arial;COLOR:navy;FONT-SIZE:16pt;FONT-WEIGHT:bold;} #yiv1389061065 P.StyleHeading3Left0Firstline0 { MARGIN:6pt 0in 0pt;FONT-FAMILY:Arial;LETTER-SPACING:-0.5pt;COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 LI.StyleHeading3Left0Firstline0 { MARGIN:6pt 0in 0pt;FONT-FAMILY:Arial;LETTER-SPACING:-0.5pt;COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 DIV.StyleHeading3Left0Firstline0 { MARGIN:6pt 0in 0pt;FONT-FAMILY:Arial;LETTER-SPACING:-0.5pt;COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 P.a-text { MARGIN:0in 0in 0pt;FONT-FAMILY:"Times New Roman";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 LI.a-text { MARGIN:0in 0in 0pt;FONT-FAMILY:"Times New Roman";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 DIV.a-text { MARGIN:0in 0in 0pt;FONT-FAMILY:"Times New Roman";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 P.apara { TEXT-INDENT:0.35in;MARGIN:0in 0in 6pt;FONT-FAMILY:"Palatino Linotype";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 LI.apara { TEXT-INDENT:0.35in;MARGIN:0in 0in 6pt;FONT-FAMILY:"Palatino Linotype";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 DIV.apara { TEXT-INDENT:0.35in;MARGIN:0in 0in 6pt;FONT-FAMILY:"Palatino Linotype";COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 P.StyleHeading1Centered { TEXT-ALIGN:center;MARGIN:0in 0in 6pt 0.5in;FONT-FAMILY:Arial;COLOR:navy;FONT-SIZE:16pt;FONT-WEIGHT:bold;} #yiv1389061065 LI.StyleHeading1Centered { TEXT-ALIGN:center;MARGIN:0in 0in 6pt 0.5in;FONT-FAMILY:Arial;COLOR:navy;FONT-SIZE:16pt;FONT-WEIGHT:bold;} #yiv1389061065 DIV.StyleHeading1Centered { TEXT-ALIGN:center;MARGIN:0in 0in 6pt 0.5in;FONT-FAMILY:Arial;COLOR:navy;FONT-SIZE:16pt;FONT-WEIGHT:bold;} #yiv1389061065 P.Styleapara1TimesNewRomanFirstline025 { TEXT-ALIGN:justify;TEXT-INDENT:0.25in;MARGIN:0in 0in 0pt;FONT-FAMILY:"Times New Roman";LETTER-SPACING:-0.25pt;COLOR:windowtext;FONT-SIZE:12pt;} #yiv1389061065 DIV.Styleapara1TimesNewRomanFirstline025 { TEXT-ALIGN:justify;TEXT-INDENT:0.25in;MARGIN:0in 0in 0pt;FONT-FAMILY:"Times New Roman";LETTER-SPACING:-0.25pt;COLOR:windowtext;FONT-SIZE:12pt;} Wrenches, I agree with Joel. This is my policy on the matter: Consider any Demand Charge reductions to be bonuses in favor of the customer. I think it is OK to say that there MAY be some savings, but DO NOT try to guarantee or insinuate that there WILL be any Demand related savings. Here's why: UNLESS you have multi-year interval data for the site... AND the ability to accurately interpret it.... AND the facility has a favorable tariff... AND a site with a very predictable load (think in terms of being able to predict the 15-minute interval which will set the Demand Charge within +/- 1 hour)... AND the 15-minute period which would otherwise set the Demand Charge coincides with a period when the PV system is operating at a predictable output.... AND your overlay of predicted generation on top of predicted load indicates a FANTASTIC Demand reduction... AND your proposed system has multiple inverters (the more the merrier here)... AND the weather is reliably predictable around the 1-hour period you predict the "new" Peak Demand to occur... Don't bother having the conversation or spending otherwise productive time analyzing the matter... If all the the ANDs above are true and you really want to go thru the exercise, for whatever reasons you may have, be sure to consider the following: In order to "prove" whether or not there was an effect on the Demand Charges due to the PV system after the fact, you will need to have interval data for both the generation and the facility. You will need to be able to evaluate whether or not the customer's load profile, independent of the PV, changed from the predicted values and, if it did, what the reasons for that were. For example, if they increase or decrease their loads independent of the PV, the net change is due to the customer's actions and the PV. Once you have determined these factors, then you can begin to calculate the effective "value" of the PV was on a Demand Charge basis. It is possible and, in fact, likely that the PV will have some positive effect on the Demand Charges for a given facility. It is, however, very difficult to predict what that will be unless all of the ANDs noted above are true. One of the keys driving the final calculation is the ratio of the PV system's power rating to the customer's load coincident to the 15-minute interval when the Demand Charges are set. The larger the system is, compared to the facility load, the more likely and greater the savings will be. Embedded in this relationship are the seasonal and hourly load profiles of the facility, the reliability of the weather during this period, and how closely they line up with the production profile. If you are intending to "guarantee" some number of kW reduction, be sure you have multiple inverters on the project. The more inverters you have, the more confidence you can have in your predictions. Over the years, I've spent plenty of brain-damaging hours (weeks & weeks) working on this. For utility companies, large integrators, and small integrators. Before and after installation. With and without complex load and generation profile data. On facilities with loads of all magnitudes and hourly/seasonal profiles. The end result is the same... The effective Demand Charge savings due strictly to the PV is relatively small and terribly difficult to predict from year to year. I've had to analyze and report on "why" the mucky-muck MBA & Engineers' predictions were so far off from the actual experience after the projects went in. In the minds of these folks, it seems like a no-brainer and just another column in their spreadsheets during the sales cycle. It's a lot more complicated than that. I know of several institutional customers who bought into paying the integrator for these Demand savings on projects and have walked away from doing it on future projects. The ones who have bought into paying for projected future Demand reductions in the up-front cost of the project have regretted it. The ones who have agreed to pay for it as a line-item on a PPA bill, aren't doing it in the future. It's simply too much brain-damage. Too complex. If they are going to have to pay somebody for it, it's a lot easier to pay the utility company. I've had to analyze and report on cases where the facility Demand Charges have increased after installation of PV systems. After you isolate the load and generation factors, and demonstrate that the customer's load profile has changed from the historical (generally larger loads later in the day when the PV can't help as much), you can do the dance of trying to show them that they avoided something and trying to quantify exactly what that is/was. A lot of Demand tariffs actually punish lower kWh consumption, so you have to factor that negative impact into the value analysis. A LOT of time goes into this when you consider all the communication, data gathering, analyisis, presentation, and negotiation. Remember, it only takes one 15-minute period that occurs outside of your effective generation curve to blow the whole theoretical thing up. IF you are set on going thru the exercise with the intent of predicting/promising something, you need a facility with a very stable load profile that occurs during peak PV periods, stable utility voltage, a tariff that doesn't punish lower consumption, reliably predictable & favorable weather coincident with facility peak demand, a large PV to Load ratio (>50%), and multiple inverters. The combination of requisite weather, PV:Load ratio, and favorable tariff pretty much makes the number of facilites, which you can model accurately, very small. I recommend going to the beach or mountains instead. $0.02001 Solar Janitor From: Joel Davidson Sent: Thursday, March 18, 2010 7:47 PM To: RE-wrenches Subject: Re: [RE-wrenches] Demand Charge Reduction by PV Hello Peter, I have seen 40% to 70% monthly demand charge reduction for some southern California PV projects for some months, but it is still a crap shoot. 15 minutes and 1 second of clouds during the peak demand period will trump a client's energy management efforts unless they are willing and able to shed loads during cloudy periods. I tell clients that they cannot rely on the weather to cooperate, to monitor and control their demand, and to think of any PV savings on their monthly demand charge as a windfall. Joel Davidson ----- Original Message ----- From: Peter Parrish To: 'RE-wrenches' Sent: Thursday, March 18, 2010 9:38 AM Subject: [RE-wrenches] Demand Charge Reduction by PV I failed to clean up the subject line on this post a few minutes ago. Please respond to this post so that we can keep track of the topic properly. Esteemed wrenches, I have been wrestling with this concept about as long as we have been in business. How to estimate how much a pv system will reduce the demand charge for a customer. I know the “worst case” goes as follows: (1) Demand is based on measuring the consumption every 15 minutes and keeping track of those numbers for the entire billing period. (2) The customer gets socked with a demand charge that is based on the highest 15 minute consumption for the entire billing period. (3) The customer also gets soaked with a “facilities charge” that is equal to the greatest monthly demand number for the trailing 12 months. (4) Now you have a solar system pumping out Wac varying over the familiar bell-shaped curve during the day. (5) In the southwest US, peak demand typically occurs early in the afternoon in the summer, during the week. Our LADWP has a mantra that goes something like this, “Peak demand occurs at 3pm PDT on the third Thursday in August!” I believe them. (6) So one would expect something like 40% of the peak Wac to offset the peak demand, but what happened if the sun goes behind a cloud for those 15 minutes? Answer, “Bad luck. Your demand is back to what it was before you bought your solar system. (7) It is actually worse than that. Peak demand recurs with approximately with the same value with some regularity for an extended period of time, so the sun will have to shine with full intensity every day when peak demand is expected to occur, which in LA could be every day (M-F) of the 30 day billing period. I have always taken the position that we can’t guarantee that any of the demand charge will be reduced with a solar system. But what do other PV integrators tell there customers? Better yet is there any actual data on demand reduction with PV systems? It seems to me that occasionally the monthly peak demand will in fact be shaved by PV production, the question is how often in practice? I once thought of taking actual insolation data and comparing it with actual demand data and doing a Monte Carlo simulation (throwing the dice = randomly matching up demand data with solar production data) – but I haven’t retired yet. I would love to hear what others are doing about this. - 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 [email protected] Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885 -----Inline Attachment Follows----- _______________________________________________ List sponsored by Home Power magazine List Address: [email protected] 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: [email protected] 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
