Another Newbie

Re: Another Newbie

welcome to the forum.

coot is right in that the loads determine the stuff needed to provide power for it. i'm hoping you went over your needs already.

often overlooked is the amount of sun that reaches a place at various times of the year, any obstructions, and being able to closely aim the pvs in a southerly direction at a good angle for collection.

keep in mind that with most batteries that you do not want to use more than half of their capacity to help preserve battery life. many don't realize they aren't meant to be discharged that low. most of us use the 50% mark to not be exceeded, but some use as little as 25% of their capacity too. i'm betting you will need more battery capacity and more pv to keep them properly charged up with based on the listed loads.

fyi, you should obtain a sine wave inverter for items that are inductive like fans, compressors, etc to not only keep from using an excessive amount of power, but to also keep the appliance lifespan good. some items requiring ac adapters are prone to blowing out too if not using sine wave. this means that you might as well just stay with a quality sine wave inverter for everything being you have at least one critical item to run being the refrigerator.

btw, you'll find allot of hams here, me included.

Re: Another Newbie

Paul,

Welcome. At this point I would only add to wht has been said already, by stating a couple of cardinal rules about off grid living and off grid solar. First, there is no such thing as "my loads are small". The reason being is that loads, ALWAYS grow with time! For example, we have been off grid for generqtion, our PV system started with a 12 vdc adding light and a small cr battery on a 60 watt panel. Then we addeda light in the kitchen, another overthe desk, a muffin fan, the radio, then some more lights, phone system, SAT ISP, etc, etc etc. we now live in a he with 24/7 120 vac power, hot and cold running water. Our usage is tiny bynmostmstqndqrds but it has trippled in the last few years. We now use between 500-1000 WH/day. We get that consistently out of 400 watts of PV into 450 ah of t105 batteries.

The other cardinal rule is that newbies (almost) always over estimate thier solar potential whilst at the same time underestimating thier loading, leading to double disappointment. My rule of thumb that has been born out thorugh many years of school of hard knocks is this. Take the NMR plate rating of the PV, divide by 2 to account for all cumulative system loses between the PV and the end use out the inverter. Then take that number and multiply it by 4 to represent the average hours of good sun, per day one can reasonably expect over the course of the year, factoring in weather, season changes etc.

So, to use my case as an example, 400 watts of PV,, 400/2=200*4=800 WH/day. Magically you will see it very closely approximates my useage. Now of course ymight get better sun than "average" but dont over estimate,, use pV watts for example for yr location.

As has been suggested earlier, the most expensive lesson of off grid PV is "ready, fire, aim!". Avoid this as much as possible by properly defining yet loads, then design a battery bank to power those loads, then in turn a chrge regimen to charge the batteries (PV, genny charger etc) and an inverter systems mix well with everything else.m anything else is ready fire aim. The result of doing any othe way might result in square pegs and round holes.

One final note. Consider your fridge needs carefully. We hve had propane fridges for decades, and before that kerosene, as the was no viable alternative. Nowadays, the more you use a place, the more cost effective if becomes to buy a good energy star conventional fridge (which will use ~500 WH/day) than it is to use either propane or some exotic off grid fridge. If I had to do it over again, a( and when my current fridge fails) I will add another 400 watts of PV and a pair of batteries for less cost thn a new propane fridge, and buy the best 120 vac fridge I can get for a few hundred dollars, and reduce my propane costs by about 1/2, all while gaining a bigger fridge.

Good luck and keep in touch,

Tony

Re: Another Newbie

paulskirocks wrote: »

Lots to think about!

OK, I have a question: If I go with a 24 or 48 volt system, what is the most efficient way to get 12 volts for my ham stuff and light the place?

There are many very efficient converters that can fit your needs for some things, the other directly with AC power...

Re: Another Newbie

you may be misunderstanding me here paul, it's the pvs that will have the higher voltage and an mppt controller will downconvert the voltage to optimize for your 12v batteries. take a look at the mppt controllers as you can feed various higher voltages as well as the standard 36 cell pvs if you like and they optimize the voltage on your 12v battery bank.

you could still go to a higher battery voltage if you would like, but everything would need to be geared for that voltage. higher battery voltages do mandate higher pv input voltages as well. what many do is get a voltage converter. here's an example of one.
http://www.solar-electric.com/12vodc50ampd.html
now i'm not pushing that one or even saying you should do it this way. you could just plug in a power supply to an inverter.

Re: Another Newbie

Photowhit wrote: »

I think you have some realistic ideas, I totally disagree with looking into a MPPT charge controller (CC) until your array reaches the 12-1400 watt area, they are no more than 10% more effiecent during most of the year in warm climates and cost $300+ more so adding to your array makes more sense (or cents) per Watt!
I also like the idea of Sam's club batteries, I had 4 that lasted 5 years being abused for the last 4 summers being drawn down near 50% DOD often, while running an A/C for a few hours during the summer.

I think that you are not taking into consideration the fact that, at least currently, higher voltage panels intended primarily for grid-tie use have a significantly lower cost per watt than the nominal 12 volt, nominal 24 volt, etc. panels intended primarily for use with PSW CCs.
For someone starting from scratch (or adding to their current system and not committed to getting panels of the same specifications), the cost of high voltage panels and an MPPT CC may be lower overall than the cost of 12 or 24 volt panels and a PWM CC.

For someone who has the extra capacity in their CC and most of the necessary panels, just adding comparable extra panels may well be less expensive than changing CCs, but future expansion also needs to be taken into consideration when making that decision.