But isn't your panel expense 2 to 4 times as much? I looked at powering some Tropos and Cisco mesh with solar and compared 48v with 12 volt. The 12 volt used a really high efficiency inverter to 120v and then to the radio. It was less than half the overall cost of the 48v system.
Ralph -----Original Message----- From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On Behalf Of Christopher Erickson Sent: Thursday, August 27, 2009 2:31 PM To: WISPA General List Subject: Re: [WISPA] solar site * 48 volt power system (actually -48VDC) is a telco standard and there is a LOT of carrier-class telecom equipment and charging systems designed to operate on that voltage. Especially a lot of remote management control and monitoring stuff. * For the same watts, when voltage goes up, amperage goes down. This means less percentage energy loss from voltage drop in wiring and the ability to use smaller gauge wire for power. * Using high-efficiency Picoverters to power 12VDC and 24VDC devices from 48VDC means that your 12VDC devices can still operate reliably when the 48VDC battery plant is down to near exhaustion. "My advice is always free and worth every penny!" -Christopher Erickson Network Design Engineer 5432 E. Northern Lights Blvd., Suite 529 Anchorage, AK 99508 N61?11.710' W149?46.723' > -----Original Message----- > From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org]on > Behalf Of Chuck Profito > Sent: Thursday, August 27, 2009 11:09 AM > To: 'WISPA General List' > Subject: Re: [WISPA] solar site > > > Chris, > Re #4: Is that because the usable voltage? Ie: 11.2V of 12, 18 of 24? 36-38 > of 48? Are these close to correct for std POE? Or what WISP's use? > > -----Original Message----- > From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On > Behalf Of Christopher Erickson > Sent: Thursday, August 27, 2009 10:53 AM > To: WISPA General List > Subject: Re: [WISPA] solar site > > I have designed a fair number of off-grid radio sites and in general, > I have come up with a few additional guidelines. > > 1. Have enough battery capacity to run for 7 days with zero charging. > This will give you a window of response time if the charging system > suffers a failure (or theft/vandalism) or there is an extended > episode of inclement weather. > > 2. Avoid as many power conversions as possible. > > 3. Avoid any equipment that has a built-in cooling fan. > > 4. 48 volt power systems are more efficient than 24 volt power systems > are more efficient than 12 volt power systems. > > 5. Avoid inverters and equipment that is 120VAC only. > > 6. Don't forget to consider environmental issues and projected > temperature extremes. > > "My advice is always free and worth every penny!" > > -Christopher Erickson > Network Design Engineer > 5432 E. Northern Lights Blvd., Suite 529 > Anchorage, AK 99508 > N61?11.710' W149?46.723' > > > > > -----Original Message----- > > From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org]on > > Behalf Of Mike > > Sent: Thursday, August 27, 2009 10:35 AM > > To: WISPA General List > > Subject: Re: [WISPA] solar site > > > > > > Instead of talking 33.3 days and 24 hours of sun, let's just take an > > average day. > > > > At optimal output, and for the sake of argument, let's say our 60W > > rated panels only produce 45W; optimally. Let's lob off 12% of that > > to satisfy the naysayers and devil's advocates, and to account for > > inefficiencies. We have a power output of close enough to 40W. > > > > Not all can do it, but for the short run repeater, and with two > > radios, let's say we run it at 12V, while loosing less heat at the > > voltage regulator on the radio. Since we're rounding numbers, we'll > > call that 3.3A. The radios require .8A. During optimal conditions, > > there are 2.5A free to charge the battery. On our average day, we > > have 6 hours of optimal sun, maybe more, maybe less. We have gained > > 15AH of charge to send to our battery. For 3 more hours of the day > > we will receive less than optimal output -- 2.5A, for another gain of > > 5.1AH. We now have 20.1AH more than we need to run the radios. We > > will get another hour of diminished 1A or less output but will not > > consider that here. > > > > So, during our 24 hours, we are either generating enough, or excess > > for 9 hours. We have to store power for the 15 hours where our > > system is not generating power. We have to provide 12AH for dark > > time. We have already generated an excess of 20.1AH. We can provide > > 8.11AH on our average day to keep our battery charged. > > > > If the 12V storage battery is capable of 800AH, and it is topped off > > with our system it CAN keep the repeater going for 41 days. If you > > monitor battery condition, you should be able to see a net loss > > coming way before it shuts down the repeater. > > > > Assumptions: > > We are using efficient radios capable of running at 12V or > > less. Let's say both are Atheros based Deliberant radios. > > The CAT5 run to our radios is insignificant, and not some 200' run. > > Hams, geeks and wisp owners are cut from similar cloth. > > > > Mike > > > > > > > > > > ---------------------------------------------------------------------- > > ---------- > > WISPA Wants You! Join today! > > http://signup.wispa.org/ > > ---------------------------------------------------------------------- > > ---------- > > > > WISPA Wireless List: wireless@wispa.org > > > > Subscribe/Unsubscribe: > > http://lists.wispa.org/mailman/listinfo/wireless > > > > Archives: http://lists.wispa.org/pipermail/wireless/ > > > ---------------------------------------------------------------------------- > ---- > WISPA Wants You! Join today! > http://signup.wispa.org/ > ---------------------------------------------------------------------------- > ---- > > WISPA Wireless List: wireless@wispa.org > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/ > > > > ---------------------------------------------------------------------- > ---------- > WISPA Wants You! Join today! > http://signup.wispa.org/ > ---------------------------------------------------------------------- > ---------- > > WISPA Wireless List: wireless@wispa.org > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/ ---------------------------------------------------------------------------- ---- WISPA Wants You! 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