Solar Energy For The Hard Up.
If you have been living off grid for a while and you have invested in a small solar set-up, which corresponds with your means, but not necessarily with your needs, and should you be living in the Northern Hemisphere, where the sun is now low in the sky, you will spend more and more time idle, as a means of conserving enough electricity to get through the night with the possibility of listening to some music or even watching a low a power consuming television.
I am in the same position, I have a small set-up, one array of ten low power panels, which generate about four hundred watts and two other panels, each of which generate two-hundred and forty watts and are mobile, and which can be moved into a position where the sun still shines.
I have a regulator of 30 amps for the ten small panels and a regulator for each of the other higher powered panels of 25 amps, which were nearly half the price of the 30 amp model.
To store the electricity, which is generated while the sun shines, I have six batteries 115 AH, gel. Which need no treatment but which cost a lot of money. You can find slow discharge lead acid batteries, far cheaper.
This system, generates less than 1kw of power, which allows me to charge the bank of batteries, quite quickly, to a reasonable level, even on winter days with the sun low in the sky. However after two or three rainy days, I have difficulty using even the coffee mill in the morning,
The first problem with setting up your system is information. I asked in a specialist workshop, if they could explain to me how many batteries, could I connect to my system with an input of 800 watts with a storage capacity at the moment of 900 AH?
The guy stared at me for about a minute and then he told me that it does not work like that sir, I’ll give you the form to fill in. He came back with a form asking me to make note of all electrical appliances, fridges, vacuum cleaners etc. in my home. He explained when I had done that he would calculate my energy needs, the amount of battery capacity to store enough of that energy to last for at least five days during bad weather.
I told him, it does not work like that for me, I buy a panel when I have the cash and the same with batteries. The problem for me is, would I be better off buying another panel, which would charge the batteries I have, more quickly, or would I be better off buying another battery.
He said he was sorry, but he had a set of tables, similar to logarithm tables, which gave him the answer which corresponded with the needs of the home and he didn’t even know any other way of calculating the length of time necessary to charge six batteries with four or five hours sunshine as a separate calculation.
If you go to the trouble of searching online, you get this sort of response:
There is not enough information, so I make the assumption that the solar panels are 36 cell panels with Vmp=18V and Imp=7.2A, and the battery is a lead acid battery.
6 * 7.2A = 43.2A maximum charge current if you use a PWM type (cheap) charge controller. if you use an MPPT charger you can get 6*130W/13V=60A charge current at 13V battery voltage.
I don’t know whether that means anything to you, but it means sweet F*** all to me. So in the end you’re more or less on your own.
In the end I thought long and hard, and I decided that as the batteries only deliver a part of their charge, before they set off the alarm on the converter, which means there is in theory enough energy to start your car left in the battery, ensuring that you do not discharge your battery too much which is detrimental for the battery.
So should I choose to buy a battery, which as I have gel batteries, designed for boats, it would in fact cost me more than a solar panel, on the “black-market” where the prices are right. This, I feel sure would put more energy into the bank of batteries as a whole, than would the addition of one battery, which would deliver only part of it’s charge extra. If you see what I mean?
You will also need to buy an inverter or converter to transform your 12 volt battery power, to 220 volt or whatever the number is in your area. As with most things you can pay a lot or a little, I chose the latter, I have a 600 watt converter and a friend has loaned me 2kw converter, they can be modified sine wave, and they cost a fraction of the pure sine wave model. If you enjoy playing vinyl records you will need the pure sine, otherwise the others work fine. Mine are left running day and night, with no problem.
I hope that might help anyone who is thinking about getting off the Grid. I have had long experience of grovelling in the mud and should you need any advice about how to get down and dirty, don’t be afraid to ask. Water can be a problem, you don’t waste too much of it washing.