Bank interest is at an all time low, inflation is high, invest in? Power.
his was a decision I made a year ago, it wasn’t easy, it was scary but it's working!
In 2021 I purchased approximately 15 x 305W solar panels which were redundant to a solar farm which, as part of their cycle, get rid after some time. These panels, although are not 100% efficient due to their age, were cheap enough per watt to make the purchase.
Hooking these panels up in the best configuration possible (Some string some parallel) I was eventually pulling in 2.5Kw/h with a 24v setup using old car batteries on a summer's day in June. It worked, the home RedFire office was powered (in the day at least) with the batteries not lasting long into the night they'd deplete until the next solar day.
The home office runs 3 screens, a computer and phone charger runs at about 750W, but we haven't turned the kettle on yet. RedFire likes their coffee!
The average house kettle touches 3000-3500W when it's boiling water, my 24v solar setup simply couldn’t supply that kind of power, only at midday in the middle of July I think I managed it once. So I purchased a camping kettle from Argos, 500W, does the job just takes 4 times as long to boil.
I wanted to go one step further, the whole house.
It's a normal house, 1930s normal semi, dishwasher, washing machine and all the other daily white goods, TVs, Playstations etc. How much power?
This is a huge question in terms of how you run your household. To do this, I had a list of things on most of the time, TVs, fridge/freezer, Google devices a few other bits, these top out at about 200-300w which in the scheme of things isn’t bad. The big power hungry items are what you need to keep an eye on. Dishwasher, Washing machine, iron, hair dryer, kettle and the oven. These can hit 3kw each easily. So how do you run your house?
Washing Machine and tumble dryer have a good chance of being on at the same time, there’s 6kw there, maybe its a Sunday, and the oven is on too, thats 9kw, not put the kettle on yet… Yes a lot to consider. The last thing you want is a power cut midway through a decent Sunday dinner.
Like most engineering projects, it's good to check if someone has had this problem before, and how it was solved. Luckily, yes, there are solutions, and plenty of them.
After months and months of research I contemplated on building my own 48v battery from cells, even thought about purchasing a Nissan Leaf to extract the batteries but, this project cannot go on for ever. It needed to be built, but then it's seamlessly integrated into life.
The Australians are in another league when it comes to solar. They also have some of the safest yet strictest laws around their solar systems which us in Europe, or UK at least haven't really got onto or seen it's a problem (yet). What I did learn from the Australians is, it's best to have a lithium iron power source, protected and well away from your house just in case things don’t go to plan. Safety was my first concern.
The basics for solar are
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Solar Panels
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Somewhere to store the power
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Something to convert the stored DC power to AC to power the house
Somewhere to store the power
Looking through my usage was a little difficult since the Covid19 pandemic, a lot of work was done from home, therefore more power usage so previous bills were sort of skewed. After considering a number of other factors, averages etc, I determined that I needed approximately 15Kw/h a day to comfortably run the house. So that means just off the battery I should be able to roughly run the house for a day. Doesn’t sound much but it's a start. I nervously purchased a 30kw/h battery and put it together.
Something to convert the power
After months and months of study, Victron was the one. First, I am not affiliated with them at all, but I will sing their phrases, their equipment is amazing. I purchased a Victron MultiPlus-II 48|10000|140 which means 48 volt, 10kw at 140amps. I can honestly say that I love it. She hangs on the wall, with huge cables as legs, humming away doing her thing. She looks after the house, monitoring battery power, feeding data to the Victron App (VRM) and you can see / second what is going on. I don’t think I’ve walked past it yet without giving it a smile.
So what did I want to achieve here?
I calculated that this setup would pay for itself within 8 years, but should last at least 20 (Batteries don’t last forever), therefore I should see a return on investment half way through the project however, there was something else to my surprise I didn’t really consider during my calculations. Enter the world of dynamic electricity prices.
This is the UK. The sun isn’t great, it's ok, but it's not Spain, you can make it on solar but you need to be in for the long game to get your returns as I mentioned. We do however have the option to go onto dynamic electric tariffs. So when the electricity is cheap, we can top up the battery (Energy Storage System or ESS mode) and when its expensive, go off the battery. There are even times the electricity is negatively priced, so they pay you to take it. Yes, I’ve even contemplated purchasing a second washing machine / tumble dryer just to take more advantage of the cheap power available throughout the year. I don’t bother feeding in, the export prices are crap.
My house has an 80A fuse from the grid (dated 1985), so I can safely pull roughly 16kw (approx 70A through it) without taking the pi$$. I have it set to 70A as voltage (and you’ll see this with your own Victron setup) in your area can fluctuate between 230-250v. My average is about 235v here, it seems to depend on the local load your sub station is handling.
I could go on about this subject for ages, but it bores most people, I am fascinated with it.