Re: [RE-wrenches] PV Assist
Eric: It sounds like you are developing a sound knowledge base on your own. I am sure you have lots to contribute. It is nice to see your posts on some interesting subjects. William _ From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of SunHarvest Sent: Saturday, August 17, 2013 2:20 PM To: RE-wrenches Subject: Re: [RE-wrenches] PV Assist As you're aware William, being my mentor, I can't give you advice on your designs...none-the-less I figured I'd throw my hat in the ring of our talkabout (verbal walkabout)... I've seen plenty of wealthy homeowners turn to solar initially for the savings and end up acquiring an affinity for saving energy which, as I've seen, can lead to an awareness on the importance of ecological preservation. Some have even put aside their more conservative sociopolitical ideologies and recalled their inherent desire to connect with their environment, a.k.a. become more hippied-out man. We run up against this concept with every single solar panel we sell. Where is it manufactured? Not at the local, organic, free-range, fair-trade solar farm that's for sure. How much embodied energy and chemical by-product comes with each module (let's not talk about batteries)? Way, way, way too much. But for now, as this is the time of transition, solar is the lesser of two evils. The underlying truth is that in order to establish a sustainable existence, at a bare minimum, we must not consume more resources than we produce. This is hardly possible given any modern lifestyle, even the most eco-friendly. Each and every one of us that are not living entirely off the land and putting back all the nutrients that we consume; despite our best intentions, recycling our plastic bottles, shopping at farmer's markets, driving electric cars, are slowly destroying our planet. So what do we do? We may not be able to save the earth but we can wake as many sleeping zombie-consumers as possible and see where that gets us. The way I see it, our good work is far from perfect but it's a modest means to a greater end and everyone must get on board, fast; even the gluttons; especially the gluttons. As it's been said, we're the pioneers. We're the messengers, the alarm clocks, and the catalysts of this paradigm shift. Energy technology is changing fast, in both the renewable and conventional sectors and we're the ones, selling solar to everything that breathes and has a pocketbook, that are helping renewables to beat coal, oil, natty gas, nuclear; and If we don't do it, who will? In order for the green revolution to contend and win we need to build bridges between the tree-huggers and the oil-mongers and that is accomplished not by creating an eco-elite but through persistent diplomacy... ...Hey, come back here with my soapbox!... ___ 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
[RE-wrenches] SB and SI
Has anyone had a good way of allowing a sunny boy in a remote building talking to an SI in the main building? Maybe wirelessly? I have an application for remote PV but SB Needs to be at remote building where grid backup is needed at main building. Thanks in advance, Erika ___ 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
[RE-wrenches] MC4 center conductors
Hi all, Does anyone have a source of just the center conductor (small metal inserts) for MC4 connectorsI seem to have accumulated a lot of female - plastic without the associated crimpable center conductor Daryl ___ 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
Re: [RE-wrenches] MC4 center conductors
PV-cables.com Jay On Aug 19, 2013, at 4:10 PM, penobscotso...@midmaine.com wrote: Hi all, Does anyone have a source of just the center conductor (small metal inserts) for MC4 connectorsI seem to have accumulated a lot of female - plastic without the associated crimpable center conductor Daryl ___ 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
[RE-wrenches] PV Assist White Paper
Friends: I wrote a draft white paper to discuss the issues relevant to PV Assist systems. If you are up for along read, please feel free. If you have suggestions, I welcome them. This idea is new to me so I am learning as I go. Also, I could not easily past the chart so I included a link to it. Also, the table did not quite line u, but I think you canfigure it out. Thanks, William Miller GENERATOR / BATTERY WITH PV ASSIST August 19, 2013 DRAFT, PRINCIPLES DISCUSSED ARE UNDER RESEARCH Introduction: Whenever we design an Off-grid Alternative Energy systems, we usually design the system so that non-fossil battery charging sources (solar, wind, hydro) provide a majority of the energy for battery charging. Sometimes we come across systems that have loads that are so large that it is not practical to rely solely on non-fossil sources. A large generator will be needed to run on a daily basis. We call these systems Generator / Battery Systems with PV Assist, or PV Assist for short. We use the term PV to describe all RE charging sources since PV is most common in our area. We have found that battery charging in PV Assist systems using traditional settings may cause premature failure in battery arrays for reasons described below. We want everyone to enjoy the longest battery life possible so we have developed some alternative settings for battery charging that will hopefully achieve longer battery life. It has always been the goal of solar technicians to minimize generator run time. In retrospect, this may not be the best idea in PV Assist systems. The consequence may be reduced battery life. Batteries wear out when they are cycled. A cycle is defined as a discharge and charge. Normally, an off-grid system will charge batteries during the day and discharge them at night, resulting in one cycle per day. In the case of a PV Assist, the batteries may cycle multiple times per day. Your battery bank is rated for a finite number of cycles. If they cycle 4 times per day, they wear out 4 times faster than if they cycled once per day. In an attempt to preserve the longevity of a battery bank in a PV Assist system, we are experimenting with alternative generator auto start and inverter / charge battery charge settings. In general, we suggest that if batteries are going to be cycled multiple times per day, that they be cycled less deeply. In other words, do not discharged the batteries to as low a voltage as one would normally. In order to achieve this goal, the generator will run more frequently than in a traditional hybrid off-grid system. In these systems it is already a given that generator run time will occur every day, even multiple times per day. We are essentially embracing generator run time to preserve battery life. We are trading off greater wear-and-tear on the generator for less wear-and-tear on the batteries. The decision to do this belongs with the system owner. Battery DOD versus life span: See figure 1 below that compares the depth of discharge (DOD) of a battery to battery life. Note that the maximum expected cycles is 4,000. If you cycle 4 times per day at this DOD, expect 1,000 days of life, or three years. If you cycle to 80% you can expect 1000 cycles, or 250 days. This is a very short life span and this scenario needs to be avoided. The sweet spot is to be determined for each unique situation, but for discussion we are assuming we want 3000 cycles, or about 2 years. This is not long for a battery bank, but keep in mind this design assumes we have undersized the battery bank significantly. Essentially you are buying two or three small battery banks in the span of time one properly sized battery bank would last. To achieve 3,000 cycles, the DOD must be limited to about 70%. The lowest we can allow the battery bank voltage to get, when measured at rest, is about 49.0 volts. Keep in mind that batteries being discharged will exhibit a voltage lower than the at-rest voltage. Also keep in mind that surge loads will cause the battery voltage to temporarily sag. The above described logic drives our suggested system settings below. http://www.trojanbatteryre.com/PDF/datasheets/L16REB_TrojanRE_Data_Sheets.pd f Generator Auto Start: We will require that generators in a PV Assist system be able to start automatically based on both battery voltage and load. Most common inverter/charger systems are capable of this. The two conditions for auto start are described below. Battery start: In the case of a battery start condition, the master inverter monitors the battery voltage. Generally, if the voltage becomes slightly low for 24 hours, or the voltage becomes moderately low for 2 hours or extremely low for 15 minutes, the generator will start. When the generator starts in these conditions, the system will complete a full three stage charge cycle. An explanation of a three stage charge cycle is beyond the scope of this paper. If we are assuming that the generator will start more than
