I thought I would make a thread about some basics of self-sufficiency. The information is all relatively available, but I havent seen a post here that
combines it into a thread. And, I was thinking that my last thread on tech may simply be too much for many to take in. Noting, however, that I only
skimmed the surface there and what was referenced wasnt just hypothetical ideas. And look how long it was
Before I start, it might be a good idea to check regulations and laws for your area.
This will focus on Electricity. Im going to try to keep it as basic as absolutely possible, because I think that anyone and everyone can use this
stuff, but many resources have a steep learning curve and those that dont tend to be conveniently provided by companies selling product. And, if you
know more than the basics, this probably isnt going to contain new info. Though please feel free to help in any way you can! I will almost certainly
miss stuff, and my goal is to essentially avoid all math and try to just give universal numbers while also avoiding too many links that might get
outdated. This is.. A very tricky task on this topic and I would still strongly suggest doing research. Just be very, very wary of getting info from
those also selling products. Remember, you can ALWAYS scale up!
Everything here is calculated for about a 10kWh system, with some info for smaller systems. The average house in the US uses ~30kWh per day, but note
that this will include large power drain systems like central AC, water heaters, typical incandescent bulbs, etc. The 10kWh is, in my opinion, a very
good platform to either jump off from, or as a goal to try to achieve. We can discuss a bit about technology that can complement this lower power
usage than average, but its something to keep in mind. It is also all 12v, and based on 5 hours of sunlight/day.
The three main types of batteries are AGM, Gel, and Lithium Iron Phosphate (LiFePo). The latter is arguably the "best," however, it is also the most
expensive. AGM (absorbed glass mat) and Gel are quite similar, but I would genuinely suggest just going for the Gel. Gel type batteries tend to be
made for slower, continuous use and for our purposes, thats perfect. If you can afford it, LiFePo really is great, but Ill only expand on that if
someone is interested. There are pros and cons to all of these though, and its strongly advised to use the same type for the whole bank. Theres
nothing saying you cant have multiple banks though. In fact, for our system, thats exactly what we will do!
When it comes to selecting the actual batteries, you may notice that many state "10hr" and "20hr." Neither is necessarily better,
are made for different purposes. The 10hr batteries will have a different internal construction that is made for quick discharge. Basically, they are
designed for emergency use when the power goes out. The 20hr construction is made to be used as a daily power source. Depending on what you want to
achieve, emergency power or supplemental power, both can work great. Either can technically be used in any system, but they arent as efficient when
deployed outside of what they were designed for. So, if you have a bunch of 10hr golf cart batteries laying around, dont think you CANT use them for
continuous power, because ya can.
Now we move on to capacity. There are plenty of calculators out there.. But the astute may notice that they are usually on sites that are.. wait for
it.. selling products. The NREL
site actually has some pretty good tools (and you only need to put in
city/state). But, for the purposes of making this is as easy to digest as possible, you are probably looking at about 2,000ah of storage for our 10kWh
system, using AGM or Gel batteries. This number accounts for the fact that you want to *avoid* discharging the batteries less than 50% and certainly
never more than 80%. It also provides a bit of a buffer for some cloudy days, etc. Batteries come in many capacities, but as capacity per battery
increases.. so does weight. Two common capacities are 100ah, which usually weighs 60-70lbs, and 200ah, which usually weighs 125-140lbs. The cost per
ah tends to be less with a 200ah battery, but thats also quite a bit of weight to deal with.
NOTE: This does not necessarily include major power hogs like central AC. Systems like that consume so
much power that if you are looking to do
that, you are starting to really jump up system size for single devices. Its also not necessarily considering some large appliances, or anything that
might use something other than ~120v (typical US power in a house). There are so many variables with it though, that it makes it immensely difficult
to give a one-size-fits-all solution. Despite trying to do just that in this thread
Important to note again, is that these systems are quite scalable. So, you can start with much less and then slowly expand over time. A good starting
point with that in mind, would be a 500-600ah battery bank. That would be something like 5 x 100ah or 3 x 200ah and will run around $1k(us) for the
batteries. Check your area too though, since there are many programs that will offset costs. The most direct is simply savings on the monthly power
bill. This size of bank might require a bit of thinking to figure out what may be necessary or not. The actual use scenarios are so specific to each
individual & house that it is very difficult to give hard numbers. But, as the systems are scalable, we can just expand as needed. If you have the
money, just go all out. If you do not, getting a single 100ah battery ($200-$250) is a great place to start.
Next up are the solar panels. Like everything else, the amount required will depend strongly on location and application. Areas that get a lot of
sunlight, and placements that get a lot of sunlight, can get away with less than areas & placements that do not. During the daytime, you ideally want
the panels to both handle power needs as well as recharge whatever was drained from the battery banks overnight. There are a lot of different
efficiencies and sizes and designs, but mainly we will look at Poly and Mono panels. Poly isnt as efficient, but it is cheaper. Dont avoid them!
For our 10kWh/day system, we will be looking at roughly 1500w-1750w of solar panels. There are a ton of different options here, but aim for that. So,
if you look at 250w panels, you will need 6-7 and for 100w panels, you will be looking at 15~17.