Home micro power station.

Hi @Rocksteady , nice info piece. 
I'm sure you will have a few interested readers .. can I ask how you manage the battery performance given NiCad’s and the presumed charge and discharge cycles?

Ahh, battery performance, to be fair I don’t concern myself too much with eeking out every scravelin of efficiency from any of this, as I know that burying your head too deep into the facts and figures can be quite disuasive in doing the job. As you can see from the drawing, I had it initially set up to to charge the battery at 15.8v but I have since increased that to 16.8v as in reality they could go to something like 17.4v but my Victron inverter will only go to 17v so I go as close as I can. The solar will get them up there very easily in good sun, and what I do is occasionally let the sun give them a substantial run of charging, then another time we give them a good draining down to their low end. I know that what I’m doing is not by the manufacturers book, but in reality, who can achieve that anyway. Cell manufacturers have to offer their recommended charge/discharge rates and times, but from my experience, it’s all very flexible. What I have found though is that these cells are far more durable in service than lead acid, and require less maintenance.

Very good - another point on the wind vs solar feeds .. can you determine how much is being generated from each individually (I can see an ammeter but presume that is for instantaneous readings) ?

I have an off grid system on our summerhouse but rarely get much more than 10’s of watts from the turbine compared to 100’s from the (small) solar pv.

Hi Yes, I don’t monitor the PVs and the windy separately, I just monitor the 230v output from the inverter through a small din rail KWH meter. As a rough guide, when we go away on caring duties for my daughter a few times a year, we regularly check our daily OVO consumption readings online. We always leave just the freezer on, there may have been the odd tv or amp been left on as well, but they take next to nothing less a bit. When we have been away, we have noticed that the freezer and other bits left on by mistake will only need about 0.8 - 0.9 units a day. When we’ve been home and had a few days of wind and no sun, the turbine has managed to put in enough to give us a similar output. While this is not an exact science, it has inspired me to build a new, more efficient turbine that hopefully will be more effective. I have trolled youtube, and there are all manner of very interesting home made device clips on there. I decided for my next one to use a modern direct drive permenant magnet washing machine motor. It is a 3 phase motor driven from an inverter, the same sort of thing as for model aircraft and now some full size ones. Anyhow, being permenant magnet, it will work as a generator. I have to re-configure the coil connections to reduce its voltage output to what I need, but in a strong enough wind it might well achieve 200+ watts. It keeps me out of mischief in my workshop, but I have to confess that without the kind of general workshop equipment that I have collected over the years, it would be very difficult to just do the things I am doing. The maximum I am having from the current turbine is about 100w.

Just an update. Being that I was installing this system during the first few months of last year, I was unable to really see any form of accuracy of readings in order to gain a reasonable understanding of what this system is giving us. I have looked at the calculations from 1st of Jan to now (27th June) and it has produced just over 1/3rd of our total consumption for this first 6 months. Obviously the most accurate figure will be on 1st July, but I is very encouraging for a first real effort.

Well, we have now completed a full year from midnight 31st December 2023 to midnight 31st December 2024 and here is what our figures show.

Elec units from grid, 831.38, 

Elec units from solar/wind, 358.

This equates to our system supplying 30% of our annual usage.

When we totalled up what we paid the grid for, our unit usage came to £197.21 the standing charges for the supply were £212.98 (more than the electricity used) Its worth noting that standing charges have increased by 450% over the last 10 years. Standing charge in 2014 was 18p per day, it is now 63p per day, while the unit charge has risen more realistically by something like 26% which is much easier to swallow. 

While we all know that the infrastructure needs maintaining, this extortionate increase on standing charge over that 10 year period is wholly disproportionate and looks more like a stealth levvy that the suppliers hope no one notices.

Apologies, the standing charge 10 years ago was 14p not 18p. The 18p was the unit rate.

As a note of encouragement, the Met office report that 2024 was more dull and overcast than usual (which is something I concur with). However, given that fact, and that there were a lot of days when our solar/wind system didn't kick in as a result, it is still quite encouraging that our little system gave us 30% of our total usage. 

We quietly hoped for 33.3% over the year, so given that the weather was as it was, 30% is not bad. We will see what this year produces.

It certainly felt more overcast to me! 

That is really encouraging 😊 30% is significant especially when energy prices are so high at the moment. 

What an interesting topic I’ve shared with my team for further reading ​@Rocksteady! Thank you 

Hi Emmanuelle, Maybe we're being a bit greedy, we had hoped for closer to 40% but settled at a sensible 33.3% based on early performance. At least by not being grid tied, we can monitor exactly what is going on. My brother in law has PVs, but has no idea what he's gaining or saving as no metering was installed with it (I think he was sold s bit of a cowboy job by having no meter for it).

I would imagine there are a few out there in the same situation, his PV installation was done on some kind of disability grant as far as I know.

Do you know of such non metered installations, and what is their true purpose?