There are various reasons for switching to renewable energy sources and it’s not too hard to find one to justify doing this. In my particular case it’s about being as friendly as i can with the environment i live in and as autonomous as i can (i do have a “fetish” for the idea of being “self sustaining”).
Years ago I started looking into this matter and after doing a bit of math the numbers told me it was not doable for me then and, even if we could afford it, the technology itself was not efficient enough meaning that a return for this investment would have come after 10 – 20 years which made it not so desirable for us at that time.
I recently started looking into this matter again and this time the math told me it is doable and worth the effort. Our average electricity bill is 50£ – 60£ per month meaning if we manage to save most of it we could be saving about 600£ – 700£ per year so one could be tempted to invest maybe 2000£ in one of them big solar and wind kits and get a return on this investment in as little as 3 years which is quite cool.
Because we as a family have a different approach on things i’m thinking start small (build a proof of concept) and do it as flexible as you can (do not buy a complete kit, buy individual items that will work together and with time upgrade the individual components or add more ) so that you spend as little as you can on this stuff and not run out of money.
Here’s what i bought for my first kit (the proof of concept – poc):
- 2 x 2 solar panel kit – 12V – 100W/panel that came with a controller and cables (can add more with time and top up with a few wind mills if you want to) – this was about 350£
- 1 x 12V AGM battery 100A – this was about 150£
- 1 x 1000W 12V Pure Sine Inverter – this was < 50£
Some maths:
One should design their systems starting with how much energy they want to be able to use on a day to day basis. An average household should not need more than 5KW / day so i’m going to do the maths with respect to this value (feel free to adjust for your needs)
To be able to use 5KW / day one needs to be able to charge at least that amount during one day (taking into consideration them bad winter days as well) OR store enough energy to last for a few days when sunt is not arround so that you get max efficiency from your panels.
A good calculation starts with assuming that you’ll get 4 – 5h/day of sun which means to get 5KW / day you need to have a solar panel kit that can deliver 1 – 1.5 KW / h so make sure you get enough solar panels to generate a minimum of 1 – 1.5KW / h of energy (in my case, 100W / panel that means I’d need 10 – 15 panels to generate this much energy)
You can also consider adding a wind generator to the mix (it will need to have its own controller or you can use a hybrid one that does both solar and wind) if you know you can rely on wind power as well but remember , work out how much power you need to be able to generate in 1h then decide on the capacity of your kit.
Generating the energy is one thing , storing it is another. Saying this because you’ll NEVER get the energy directly from the solar panels , it will first go to your battery THEN will get to you (the consumer) so you need to be able to store at least 5KW of energy in your battery bank.
If say you buy 12V – 100A batteries that means you have 1.2KW of energy stored and if you need to have 5KW then you’ll probably need 4 – 5 batteries with these spec connected in parallel (parallel will give you more amps, series will give you more Volts – should be able to find some videos online on how to do this)
You can also consider storing energy for more than 1 day, in that case you’ll need more batteries (ex. for 3 days you’ll need 3 times more batteries … )
Also, to be able to use this energy properly you will need decent solar charge controllers (notice the s at the end – yes, you need to have more than one) and a decent Inverter that can deliver you peak power when you need it for how long you need it. What i mean by that is , for example your washing machine, which say you use for 30 min once a week , which will most likely spike at 3 – 4KW/h when starting then probably have an average consumption rate of 1 – 2KW/h which combined with your kettle which does something like 1.5 – 2KW/h but which you only use for say 3 min to boil the water you need to make your tea which combined will give you a spike of maybe 6KW which will probably cause your Inverter to stop (enter protection mode) unless it was designed to deliver spike loads for a set amount of time.
Remember, you store 5KW in your batteries BUT for 10 min you need to be able to serve a high amount of amps for some specific tasks meaning you might probably need to draw 3KW from your batteries in 10 min and the remaining 2KW you have left you’ll use for the TV throughout the remainder of the day -> this is why you will probably need to have some decent AGM batteries and a pure sine wave inverter that can deliver 6KW/h at a constant rate and which can spike at 10 – 12 KW (so that you can cope with the spikes generated by washing machine engine or the compressor inside your fridge)
Get the math right and you’ll be generating the energy you need thanks to sun and mybe wind. Get it wrong and you’ll either have invested more than you should have or not enough for the workload you have
In my case i wanted a small kit to play with and maybe use for powering a NAS , a notebook, some TVs, charging phones, etc (small appliances)
The DIY part
Step1: I connected the battery to both solar controllers (in parallel to get more amps and had to do this first because battery needs to be connected first according to instructions)
Step2: I installed the 4 panels on my garden shed (2 panels / kit) and connected them to their controllers (you can’t make any mistakes here because they come with their own cables which have special sockets)
Step3: I connected the Inverter to both solar charge controllers (in paralle to get more amps)
Remember! Order of installing / connecting these things is importand! Same goes for uninstalling (which is the other way arround)!
After all this work i was able to confirm everything was ok by checking the LCDs on the controllers which were showing that energy was being generated by the solar panels which was collected by the battery which then was powering the consumers.
What I can tell you now is that I’m writing this article from my notebook which is running on solar energy (which is giving me an incredible amount of satisfaction) and that soon i’m going to add more batteries to the kit to store more energy which should give me more autonomy.
Why should you do this?
Because you’ll get a return on your investment in a few years and not only that you’ll be friendlier with nature in the process.
