Since we're talking about a relatively small system, I would base whether to do a 24v or 48v system on what the majority of the load is going to be. If it's going to be like 70% 24v gear, I'd go with 24v, but otherwise, I'd probably lean towards 48v.
Bill's numbers look about right for what you'd want for a system that you aren't going to need to worry about. If you're not opposed to the risk of maybe occasionally needing to go out and swap out some batteries in the middle of winter, and that sort of thing, it's possible to do it with a smaller system. We have a micropop with a roughly 10-12 watt load running on 200 watts of solar panel and ~5KWH of lead acid batteries (that happened to be what I had on hand at the time... there wasn't any logic involved in picking that size)... so far it seems to be surviving the Wisconsin winter. On Tue, Jan 12, 2021 at 12:55 PM Bill Prince <[email protected]> wrote: > If your load is 50W, then you need to deal with ~~ 1.2 KWH of energy > usage per day (50*24). > > We don't know your latitude, or location, so you will have to plug in > whatever solar values are typical for your area. However, a good rule of > thumb for mid-latitude areas is to have enough battery for 10 days of > operation without sun. So you will need about 12KWH of battery storage. > If you're using lead acid batteries, double that for 24KWH of storage. > > Then you will need enough solar for you to recover that in one or two > days. For example, if you have 1200 watts of solar, you can typically > expect to get back 4.8KWH per day (5 hour day at 80%). > > A 48V system would be the most efficient. It will require smaller wires, > and converting from 48->24 is more efficient than the other way around. > > Separately, I would suggest to examine your sanity for thinking you > might be the only one in the US to make TVWS actually work. > > > bp > <part15sbs{at}gmail{dot}com> > > On 1/12/2021 10:42 AM, D. Bernardi wrote: > > > > Hi, > > > > I'm considering some fixed wireless (TVWS) trials and/or the ability > > to deliver temporary service where there's no available power source. > > I've done some basic solar system calculations (and there are plenty > > of calculators) but I'm looking for some real world pointers from > > those that have deployed off-grid micro-PoPs. > > > > DC only, no inverters required. We may need 24v PoE and 48v PoE so > > would a 48v system with step down to 24v be more efficient than 12v or > > 24v with a step up? Other trade-offs to consider for 12v/24v/48v > > storage systems? > > > > I don't have actual load measurements yet but at this point I'm > > currently sizing for a 50w load. The base station and backhaul radios > > combined should be ~ 30w. > > > > Thanks, > > Dave B. > > > > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com >
-- AF mailing list [email protected] http://af.afmug.com/mailman/listinfo/af_af.afmug.com
