UK solar doldrums

[fourtytwo42]

Hi Paul it's really great to hear that your battery is ok after all, today was a day of surplus for me getting 1.5Kwh from my 1Kw array, I could have got more but I ran out of load, hot water full, de-humidifier on and freezers on but I still could not absorb it all so you see I am thinking BATTERY (one day)!

As for confusing technology tell me about it, I blew another IRS2110 half bridge driver today yet not the mosfets I hope all because I suspect a PIC is not terminating the current cycle on overcurrent, very hard to prove without further losses, so although your system and problems are at a very high level I can assure you even at the coalface life remains confusing!

I think you are from Ireland, I spent a lot of time there inside steam engine boilers at Whitehead, I hope the RPSI is still going strong and entertaining families with the Portrush flyer

[paulca]

Not sure about the RPSI but they have opened a train museum in Downpatrick where they collect old trains and have about half a mile of line to run them on.

I live just across from Whitehead in North Down.

[fourtytwo42]

Not sure about the RPSI but they have opened a train museum in Downpatrick where they collect old trains and have about half a mile of line to run them on.
I live just across from Whitehead in North Down.

I am sooo jealous many is the time I have been down there lighting up at 4am! You must be able to see, smell and hear them hahaha but I must admit most of the big trains for tours were stabled overnight in Belfast the night before the off.

Anyway an update covering the last three years up till the end of last month from my tiny 1Kw array here in the dull UK! 52deg North. This is predominantly a water heating system but during 2018 a GTI was added (export inhibited) to use some of the surplus in the house, this improved the utilization in summer 2018 compared with 2017. There are several outages due to experimentation and uhum magic smoke emissions

[paulca]

I have too much solar power.  My panel is sitting at 22V producing FA squared.

I have charged every battery I can find.  I have now:

100Ah marine primary fully charged.
26Ah old primary AGM charged.
12Ah Maplin salvage charged.
55Ah old car battery charged.
About a dozen LiPos charged.
My 22Ah USB powerbank charged.
Phone, all eCigs, anything I can find, fully charged.

It's painful watching the panel sit open circuit.  I need ideas.

12V 50W off grid hobby system.

EDIT:  I could use the laptop as the bedroom TV source again, rather than the media PC and run it off a Lead acid to use up some of the power.

[NiHaoMike]

I have too much solar power.  My panel is sitting at 22V producing FA squared.

I have charged every battery I can find.  I have now:

100Ah marine primary fully charged.
26Ah old primary AGM charged.
12Ah Maplin salvage charged.
55Ah old car battery charged.
About a dozen LiPos charged.
My 22Ah USB powerbank charged.
Phone, all eCigs, anything I can find, fully charged.

It's painful watching the panel sit open circuit.  I need ideas.

12V 50W off grid hobby system.

EDIT:  I could use the laptop as the bedroom TV source again, rather than the media PC and run it off a Lead acid to use up some of the power.

If you have unlimited Internet, run some old laptops/tablets/phones playing Youtube videos to help out makers who currently have lost their primary source of income (including temporarily) as a result of the current crisis? Not sure if that would make them enough to cover the usual cost of electricity but if it's going to waste otherwise...

I have since (back around early 2019) reclaimed most of my crypto mining setup to use for other purposes due to coins either crashing or going up in difficulty to the point where they're no longer worth mining. What's left is a tablet mining Swagbucks, now down to about $5/month. The 100W panel I have is now mostly being used to power my IT setup.

My latest project with solar is a system that can power the whole house, with no significant rewiring needed. More or less it makes use of a modified Prius inverter connected to a FPGA in order to source current in step to what the load is drawing, in order to not export any power and avoid the hassles associated with doing so.

[fourtytwo42]

I have too much solar power.  My panel is sitting at 22V producing FA squared.

How about water heating, do you have an immersion ? If so a small boost converter with MPPT would be an interesting project maybe. If not that then a desk fan to cool your sweaty brow whilst working from home 

Of course the weatherman is about to take the sun away again so nature may also have an answer to your problem 

[paulca]

I have too much solar power.  My panel is sitting at 22V producing FA squared.

How about water heating, do you have an immersion ? If so a small boost converter with MPPT would be an interesting project maybe. If not that then a desk fan to cool your sweaty brow whilst working from home 

Of course the weatherman is about to take the sun away again so nature may also have an answer to your problem 

I have a combi boiler now

I did wonder if I could make beer with solar power, but running a 3kw boiler for nearly 2 hours, 6 Kwh, is a bit beyond a 50W panel and a few lead acids. 

And yes, looks like it could rain for weeks now.  Probably my fault, I ordered a BBQ.

[Zero999]

So far this thread has just confirmed that solar power in northern Europe is only from April to September. For it to be any use, we need more energy storage, cables to get power from more sunny places and other energy sources such as wind.

We'll probably have another wet summer, especially has we've had a warm and dry April, which is often a prelude to a soggy summer.

[fourtytwo42]

So far this thread has just confirmed that solar power in northern Europe is only from April to September. For it to be any use, we need more energy storage, cables to get power from more sunny places and other energy sources such as wind.

I would say it shows solar solutions are perfectly feasible at the DIY level with an economic return on investment without spending large amounts of money on so called turnkey solutions. Wind is not practicable in an ordinary UK household as the land area is not available. Energy storage (as in batteries) at a household level is unlikely to ever pay for itself and cables to carry power from north Africa to the uk beggars the imagination. This thread is about SMALL SCALE DIY PV, nothing else.

[fourtytwo42]

I did wonder if I could make beer with solar power, but running a 3kw boiler for nearly 2 hours, 6 Kwh, is a bit beyond a 50W panel and a few lead acids. 

I have often thought the same as I make lots of wine & beer, sometimes I plan it so my small 1Kw array is generating when I do the boil for a brew but as often as not I don't have the patience! I have also thought of increasing PV capacity for such occasions (and cooking) but it would be hard to justify it as on average in my case 1Kw is enough for both water heating and the standing loads (like fridge, freezer & PC etc).

Actually with a dry garden I am looking forwards to the rain 

[Zero999]

So far this thread has just confirmed that solar power in northern Europe is only from April to September. For it to be any use, we need more energy storage, cables to get power from more sunny places and other energy sources such as wind.

I would say it shows solar solutions are perfectly feasible at the DIY level with an economic return on investment without spending large amounts of money on so called turnkey solutions. Wind is not practicable in an ordinary UK household as the land area is not available. Energy storage (as in batteries) at a household level is unlikely to ever pay for itself and cables to carry power from north Africa to the uk beggars the imagination. This thread is about SMALL SCALE DIY PV, nothing else.

Yes, that's true. Small, domestic solar panels are practical, whilst wind is not and batteries don't pay off. The problem is, what happens if everyone does it? There will be surplus energy in the daytime, especially during spring and summer. There could be some energy storage, like the hydroelectric one in Wales, but we need much more of it. Otherwise energy will end up being wasted during the day, only for oil and gas generators to start up overnight. I can foresee more wastage in areas where there's already a large power station, such as nuclear, which can't be shutdown.

[Marco]

The problem is, what happens if everyone does it?

Grid connection costs will have to go way up, too much of the grid costs are put into kWh pricing.

PV costs are going to keep plummeting though, assuming civilization doesn't collapse, so I doubt they will stop making sense. It might stop making sense as retrofit, but I wouldn't be surprised if things like roofing rubber for flat roofs will start becoming PV ... it's not going to add enough cost relative to the bulk cost of the rubber and labour to matter much. Same with siding.

Otherwise energy will end up being wasted during the day, only for oil and gas generators to start up overnight. I can foresee more wastage in areas where there's already a large power station, such as nuclear, which can't be shutdown.

If you give it out for free, people are going to use it. Hydrogen generation might be energy inefficient, but if the energy is free who cares?

[paulca]

I think it's time to shut the micro-solar down for the winter.  Either that or put the battery charger on it for a few days   It can't even power the charge controller with the daylight it's getting.

[f4eru]

your charge controller probably consume quite a lot. What model i it and how much power does it draw ?

[coppice]

I think it's time to shut the micro-solar down for the winter.  Either that or put the battery charger on it for a few days   It can't even power the charge controller with the daylight it's getting.

But surely we just need some battery storage to ride over the lulls in output, and existing renewable solutions are going to be fantastic.

[fourtytwo42]

Good to see the good ole thread still ticking away! daily average this week down to 0.4Kwh/day from a 1Kwe array but last few days steadily worsening due to rain & cloud/fog/clag!

I always find this time of year good for maintenance & testing new generations of equipment etc as there's no serious production going on. I am now on my 3rd generation of pcb's (means a big hardware architecture change) and similar in software for the converter having finally integrated the hot water and GTI functions into a single converter.

Most recently been tuning the PD loop to get the best transient performance, I tried so hard to model the thing but as I suspect many have found with servo systems the only real method is empirical on the actual machine. Sitting outside with the laptop with the temperature below freezing is a particular kind of torture especially when the sun wont play ball!

For those of you using off the shelf equipment I can only feel sorry that you are missing all the pain/fun 

P.S. I seem to get down to about 2W before the system gives up in the evening and start-up at about 4W in the mornings so I am quite pleased with that.

Pictures are always fun so here are some scope shots I hope.....

[paulca]

your charge controller probably consume quite a lot. What model i it and how much power does it draw ?

It's an EPever 10A MPPT.  Last time I checked it and the monitor it powers consumed something like 60mA.  Half of that is the Wifi monitor.

It works out something like, the 100Ah battery can run the system for 70 days.  Although that's probably 40 days as it's a lead acid.  It's just that right now progressively more is going than coming in.

It hit 30W this morning, for about an hour.  So it might live another day or two without life support.

[Northy]

What are you guys doing to monitor what's going in/out?

I've got a couple of cheap 20W panels charging some gel cells.
It was great through the good weather months, I could charge every battery in sight! Phones, tablets etc.
It seems at the moment that I can't get any spare capacity, but I don't monitor what goes in/out.

Is it just time to turn it off for the winter?
Is there a way to cut connection in the dark so the controller doesn't flatten the battery?
Are/can home built charge controllers be more efficient?
Would adding more panels give me any spare capacity at this time of year?

Thanks,

G

[HB9EVI]

the Wifi dongle to the Epever sucks in indeed quite much; I left it out of the setup and read out the rs485 by a python script.

if the controller kills the battery you have either too little capacity on the battery side or too little input power by the panels.
like already said the EPever Tracert 10/20A sucks about 30mA what seems to me quite acceptable for its features.

around this time of the year I get my 120Ah battery about every 4/5th day to float charge. When the battery goes under 12,2V, I activate the charger which is integrated in my inverter; this I need to do about 2-3 times per winter; well I'm not consuming any power from the battery december/january, so it's idling. Solar power I have 200Wp, so it's a small island only

If you are a good EE, you can construct your own charger, otherwise you're maybe better off with a commercial product, since they are really cheap in the meantime. Imo it's questionable if you can construct one for the money the Epever costs - with the same set of features.

[paulca]

To collect EPEver stats I wrote this:
https://gitlab.com/paulcam/home_heating/-/blob/master/esp8266/epever_rs485_v3/epever_rs485_v3.ino

Which uses an ESP8266 to publish the RS485 epever controller stats.
Hardware required is:
ESP8266 devboard.
MAX485 breakout board.
BiDirectional logic level changer (5V / 3.3V)

There is a thread of mine about 2 or 3 years old with more details.

I then publish that along with all my other "home" stats.  Which ends up producing this:
Open in new tab and zoom in a lot.  I'm going to be porting most of it to MQTT to open it to others.

[paulca]

Is it just time to turn it off for the winter?
Is there a way to cut connection in the dark so the controller doesn't flatten the battery?
Are/can home built charge controllers be more efficient?
Would adding more panels give me any spare capacity at this time of year?

Even if you do turn it off for winter, if it's outside and a lead-acid, I would charge it fully first.  Most solar systems are protected enough for you to just stick a normal 2A car battery charger across the battery without disconnecting it.  That's what I do, when the voltage drops below about 11.8V I put the car battery charger on it overnight.  Repeat as needed.

The EPEver has a handful of low-cut off and low-restore voltage triggers, however I wouldn't trust them.  Mine is set to cut off at 10V, but last year the battery collapsed and the charge controller didn't connect it until it hit 8V.

The issue with making disconnect circuits is they have to take the full DC amps available at the battery fuse which leaves you with a large power mosfet or a relay.  You have to account for the voltage dropping under load and relaxing back up when you disconnect it.  You can also risk the charge controller remaining off due to disconnect but it's a rare bluesky winter day.

Home MPPT charge controllers are feasible.  It's just a buck converter and scanning algorythm.   Jullian Ilett on Youtube did a series where he built one.  The EPEvers were cheap and featured enough that I didn't bother.  Though I was going to revisit it just for fun.

Adding more panels would give you more capacity, but also more loss in summer when you can't quite use it all.

You'd be better off making sure the panel is mounted high as you can and angled up nearly straight for the winter sun.  Battery capacity is more practical. 

That said it really comes down to the amount of energy you can get in a solar day, what the weather is like and how long your system will run on it's battery with the limited top ups from the panel in winter.

[paulca]

Calculating my system drain...

60mA (30mA for the charge controller and 30 average for the Wifi monitor).
60mA * ~12V = 0.72W
0.72W * 24 hours = 17 Wh per day = 121 Wh per week. 

The 100Ah Marine Lead Acid has a theoretical 1200Wh, but a usable 600Wh - degradation having been flattened once, survived two winters and now being 1.5 years old daily cycled.  So probably about 400Wh

600Wh / 121Wh/w = 5 weeks.

The graph I posted shows it's daily decline, occasionally lifted by an hour or two of 25-35W, over 5 months.  I need a minimum of 17Wh per day.  In November/December/January/February I just don't average that.  Working out what I do average will just take a nicer DB query.

The only requirement of this solar system is that it runs my garage lights.  So I need it for the laundry weekly for 5 minutes.  In summer I charge all my battery powered stuff from it and am adding a large LED strip for a few hours after dust in summer.

[Northy]

My Solar controller is just one of the cheap blue generic ones from Ebay, initially it was just an experiment to see if I could get a useful amount of energy. In the Summer it seems I can.
I'm tempted to buy a 2nd hand big panel now and stick it on the gable-end of the garage to move things on a bit.
Maybe the smaller panels would run some garden lights even in winter? 

G