48VDC equipment is almost always carrier-class and that is where the expense is. That isn't quite the same as having a 48VDC power plant with non carrier-class equipment running on it.
What is really absurd is converting a 12/24/48VDC battery plant to 120VAC to feed a piece of equipment that is going to convert it back down to 5VDC and 12VDC using a reasonably reliable but highly inefficient computer type switching power supply. Cisco and Motorola make some of the most power-inefficient networking and radio equipment on the market. No big deal when you are on the grid. But a real big deal when you are not. I guess off-grid sites are just too tiny a portion of their market to worry about. "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 ralph > Sent: Thursday, August 27, 2009 1:26 PM > To: 'WISPA General List' > Subject: Re: [WISPA] solar site > > > 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! 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