Solar panel update.

[Bill]

For anyone that’s interested, here’s an update on my experiments with a small-scale solar setup that I bought in February for £212. The idea was to save some money without it taking years to pay for itself and so far, the results have been very good despite not having an ideal solar location.

Since I started, my bills have dropped approximately £20 a month, partly from the solar but also from turning off appliances when not needed so it looks like it’s on track to pay for itself in about a year.

 

Bill 😊

[Bill]

Here’s the latest electricity usage graphs now I have four panels in use. My house has no south facing roof so the best I could come up with was to put them on the garage roof. I have two panels facing south and one each east and west. It isn’t ideal, but it does at least they generate power from early in the morning to last thing in the day.

Lately, I have some problem with shading from a large oak tree in a neighbour’s garden and this will worsen as the sun drops lower during the winter months. The power drops by 50% for a couple of hours when the tree gets in the way, but it might get a bit better when the leaves fall off.

Most days, I generate most of the power than I need; some days a bit less but on a good day I can end up giving several Kilowatts back to the grid so I’m currently working to add some battery storage to even things out. This isn’t as easy as it sounds, and the electronics and software needed to do this efficiently is proving to be a real challenge for me but I’m getting there.

 

Bill

 

[Evil Sid]

have a word with warrington council they seem to have it all in hand as regards solar power......

just as a side thought how much power is generated by the moonlight on a clear night?

just curious if it is any at all.

 

 

 

[Bill]

The answer to that Sid is two tenths of nothing. The panels do generate a surprisingly high voltage from a full moon, but there’s absolutely no umph behind it and that voltage collapses to nothing the instant you connect anything.

Sitting here writing this, I’ve got hazy sunshine and I’m showing 661 watts being generated. 63 watts of that is charging my batteries, the house is taking 230 watts and what’s left over is helping to power your house. I’ll send you my bill in the post. 😊

 

Bill 😊

[Evil Sid]

as long as it make more sense than my last couple.

had a bill for £11. went to pay it and they said i was £54 in credit only to get an email this morning saying i now owed £197.

spent half an hour chatting with a nice lady on the phone and managed to sort out the confusion and got £20 knocked off the bill so only £170 to pay.

Apparently, my smart meter isn't as smart as it is supposed to be and has either not been sending readings or sending the wrong readings depending on what day of the week it is......

[Bill]

I don’t seem to have any issues with the smart meter’s billing, I pay a fixed amount each month by direct debit, so I know exactly what’s going to go out each month. Before all the problems, I was only paying £47 per month due to having accrued quite a bit of credit over previous years, but even if things had remained the same, I would have had to increase my payments as this credit was getting lower each month.

I’m currently paying the £125 they suggested a while back, so my credit is now going up and I’m going to leave it that way until I know how the winter pans out. My mate reckons I’m crazy and that I should keep the money in my own account rather than the suppliers. But I’d rather have the certainty of knowing what’s going out each month and the miniscule amount of interest I might loose these days is insignificant.

 

Bill 😊

[Evil Sid]

from what i gathered talking to them it was partly the meter and partly their system.

the first two bills i had were estimated for the gas based on a guess by them how much i would use. however since i had at least one radiator fitted i have been using a lot less gas to heat the house, gas fires were hammering the readings.

then the meter started sending readings to their system which, along with the "help" payments meant that i was well in front money wise. cue the next bill and for some reason they cancelled it and produced the one that read as £11.  this again was based on a guesstimate but two days later they got a reading from the meter hence the new bill for the £197.  why they had to mess about with several bills and not just tag it onto the next one i do not know,they do if you are in credit.

[Bill]

I’ve just measured my total power generation for the last month and it’s down to just 50Kw hours or £18 in money terms which is lower than expected and a bit disappointing. I expected the numbers to drop during the shorter winter months but not quite this early or by so much.  This seems to be a result of unforeseen shading, partly from the neighbour’s roof but mainly from a large oak tree that’s still in full leaf and which completely blocks the sun for a couple of hours at the peak of the midday sun.

Hopefully I can improve shadow problem from the neighbour’s roof by simply moving a couple of the panels slightly higher up on my roof but there’s nothing I can do about the tree other than wait for the leaves to drop.

Other than that, I still haven’t managed to sort out my battery charging system, so most days I end up sending power back to the grid. It’s not quite as easy as you’d think to do this, and I’ve already blown up a couple of modules while trying but fingers crossed my latest attempt looks more hopeful and should go a long way to extending generation after the sun sets.

 

Bill 😊

[Bill]

I've just finally managed to make myself a smart meter display that includes all the data from my solar stuff. It took me nearly two weeks to get it to this point. Its only cost £18 so far and  I'm just waiting for a small plastic box to build it into and the jobs a good-un. 

When this picture was taken, the house was using 192 Watts and the solar (with a cloudy sky) was making 137 which is a 71% saving. Ealier when the sun was better, it was saving 100%, while at the same time charging the batteries and even sending a couple of hundred watts  back to the grid.  

The picture's not that clear because it's still got the plastic film on. BTW the little white pointy thing top center is a spinny round thing that I put on for Mrs Green to mimic the old spinning disc on the old meters. She dosn't get the numbers but understands when that's wizzing round, it's using a lot!

 

Bill

[Evil Sid]

carry on like this and Warrington council might be calling you to make an investment.........😎

[Bill]

If I could make something for just £18 Sid, you could bet Warrington Council would rather put it out to tender and end up paying a few hundred thousand pounds for something that ends up like the bus displays.

It's not what you know but rather who you know when it comes to the council.

 

Bill

[Evil Sid]

I know that mentality well Bill, having worked at the lab for twenty odd years.

best example was when they shipped a dozen super conducting magnets to Australia or at least that area of the world.

Bid for crating up went to a guy who promised a top of the range purpose built summer house to the bloke who made the decisions.

Trouble was they were just crated up as normal rather than weather proofed and got sent as deck cargo.

By the time they got to their destination they were just rusted lumps of scrap metal........🤦‍♀️

The decision maker got a nice summer house though.

[Bill]

Finally got my little display all boxed up and working. I gave up with the MEMS temperature sensor as I just couldn’t get the processor to talk to it so ended up using a standard thermocouple which isn’t that accurate but still good enough.

 

 I’ve taken some pictures but for some reason, Samsung phones seem to completely filter out certain shades of green, so all the pictures look a bit washed out. What shows as green on this image is really dull green but where it’s white (100% solar) is actually bright green. How and why phone cameras do this is beyond me

 

I managed to angle the phone at just the right angle to make the green show but even then, it’s still a bit washed out in places. Interestingly (or not) this one shows the low levels of solar starting from the winter solstice (21^st Dec) through to yesterday. The suns that low in the sky at this time of year that for most of the time my panels are in the shade of nearby buildings and trees.

 

This is the default live screen that at 2.30 yesterday showed that up to then we’d used 78p of electric and saved just 18p. The batteries are fully charged but I’m not using them at the moment as there’s so little sun that I can’t guarantee that they won’t end up flat for a prolonged period which doesn’t do them any good.

The good thing about making my own smart meter is I was able to make it show both solar and mains. Just need a couple of sticky pads now to mount the thing and the jobs a good un.

 

Bill 😊

[Confused52]

Nice looking piece of kit Bill. As a matter of interest where and how are you measuring the current/volts in the mains part of it?

[Bill]

It’s just a simple current transformer that clips around the main feed to the distribution unit. It’s a 30 Amp device, but the performance wasn’t that good at low levels because of inverter noise, so I added a simple op amp filter with a bit of gain. The voltage part comes from a small 9-volt transformer and resistive divider, adjusted to give about 3 volts peak to peak at 240V. Both outputs are then fed into the a/d inputs of the processor.

Originally, I coded the entire thing then incorporated a fudge factor to make it match the readings on an external power meter. It worked ok but then I found a readymade bit of code See this that did all the complex stuff like power factor correction and didn’t need any fudging. So now, there’s very little code to see however it’s still not super accurate at the bottom end between 0 and 30 watts but that’s no big deal.

There's nothing connected directly to the mains and the whole mains thing is just on a bit of Veroboard tucked away out of sight. The readings are sent via a pseudo WiFi link to my garage where a second processor does most of the work before sending it on again to the new display unit in the kitchen.

 

Bill 😊

[Confused52]

Excellent, thanks. Useful reference too. 

[Bill]

If anyone’s ever contemplating doing something similar to what I’ve been doing, here’s a top tip!

Disconnect the solar panels before soldering any new parts into the circuity. 🧐😕😟☹️

I thought I’d done that but unfortunately, I’d disconnected the wrong wire (same colour) which immediately zapped the main microprocessor. While I was puzzling why everything seemed to have stopped, I noticed smoke coming from the battery charging module. Then by the time I realized where the power was comming from, capacitors on the charger began to explode, leaving a bloomin awful smell in the garage that lasted for days.

It's basically back up and running again now, but no battery power or further development work until the replacement parts arrive from China.

I thought I’d post this just in case anyone was loosing sleep wondering why I’m posting so much lately. 😊

 

Bill 😊

[Evil Sid]

approximate electrician rule one. with enough insulation tape round it nobody will notice.

and some wise words from my electrical teacher. red to red, black to black. if in doubt short it out.

makes you wonder though how the inventors of electrical bits in the early days managed......⚡....🔥....."oh well back to the drawing board, BUT i know where i went wrong this time"

[Bill]

Time for another update.

Still not 100% finished, the battery plan ended up being a lot trickier than I thought plus I’ve lost count of how many times I’ve blown various bit up. Anyway, its working reasonably well now and most days at this time of year it’s generating a couple of pounds worth of electricity even without the batteries.

The problem with the battery is that I’m using lead acid rather than the vastly more expensive lithium ion. Their capacities are identical, but the lead acid ones can’t be safely recharged anywhere near as fast as lithium ion. As a result, I rarely get a fully charged battery by the end of the day and typically 75% of the charging power is still being lost to the grid.

The original plan was for the batteries to take over at the end of the day, but to do this I had to have a fully charged battery. With the charging coming in fits and starts depending on the sun, I decided to change it such that the batteries now assist the solar during the day, attempting to maintain zero current to or from the mains.

This means I need two inverters, but the advantage of this method is that because the battery gets partially discharged every time the sun dips, it allows me to use a far higher boost charge when the sun re-appears. As a result, I now get the most out of the battery during the day with a lot less power being sent back to the grid.

Happy days!

 

Bill 😊

[Evil Sid]

all you need to do now is convert some old electric fans to wind turbines and you could have it well sorted.

they might not generate much but they would work at night as well as during the day.

[Bill]

Yet another boring report on my obsession with solar power as the battery saga continues.

I finally managed to get all the control circuity working perfectly once I realized that the problems were being caused not by my software but by one of the inverters I was using. The one causing the problem was a bigger high-power unit, but it was just too brutal and clunky. Changing it for a smaller device gave me the precise control I needed so with everything working perfectly I sat back and waited to see how much extra power I could harvest.

I have two 12V 100A/hr lead acid leisure batteries connected in series to give 24V. Discharging them slowly to 50% should give me about 1Kwhr which works out at about 36p. So you can imagine my surprise when after a few days, the results showed the most I was able to get from them equated to 4p each night. 🧐 Something was definitely very wrong.

I charged both batteries to full charge then discharged them individually using a 55watt car headlight bulb while recording the voltage. The first battery behaved normally but became fully discharged after just 2 hours which was only a tenth of what I’d have expected. Battery number 2 imediately collapsed like a pack of cards, dropping down to below 10V.

Despite all the issues I’ve had with the charging circuitry, I don’t think I could have done anything to cause the batteries any damage, so I’ve returned them to the supplier for them to investigate. Maybe I did break them but at least I didn’t pay a fortune and if I do have to replace them it’s not the end of the world provided they work.

 

Bill 😊

[Confused52]

That sounds very familiar to be honest. In my line of business they are used as voltage smoothers and when called upon to supply full load they usually pack up quickly, measured in minutes. I used to have a room full of them and they were mainly acting as a gigantic smoothing capacitor! (With the added capability of melting screwdrivers in the hands of the unwary.)

[Bill]

The leisure batteries I’m using are a slightly different version of a standard car battery. They’re designed for lower currents but for longer periods of time rather than the short bursts of high current needed when starting a car. The problem with all batteries though is that they gradually loose their capacity to hold a charge and that gets accelerated the harder you work them, and their life expectancy can be as little as a couple of years.

In theory, I could charge mine at 20 amps maximum, but I’m being very conservative by limiting the maximum current to just 6 amps. In practice this doesn’t occur that often as charging only occurs when current begins flowing backwards into the grid and even then it’s proportional.

The life expectancy of this type of battery with careful use is claimed to be up to 10 years. My guestimate is that mine need to survive for three years to cover their cost. What I have at the moment have only lasted about two months so something is very wrong and that’s why I’m asking for a proper load test to be carried out.  

 

Bill 😊

[Bill]

It turned out as I suspected that the batteries had failed. When I initially received the two batteries, one of them didn’t show green in the charge indicator however, my meter showed it to be fully charged so I foolishly ignored it. It turned out that that was the battery that didn’t perform but as both batteries were connected together in series, overall, they appeared to be correct but nowhere near how they should have.

The supplier said that the batteries appeared to have suffered deep and prolonged discharging which caused permanent damage however I know that not to be the case. They have very kindly replaced both batteries at no cost so now it’s time to give them a try out. Oddly, the replacement batteries although marked up as being the same, they have no charge indicators and unlike the originals, they’re not maintenance free and have the ability for the fluid to be topped up.  

A load test with the car headlight bulb showed a completely different picture with the voltage holding up well over four hours. Unfortunately, I only got to test one as the bulb I was using decided it’d had enough and ended the test prematurely. They’re cheap bottom of the line batteries but I think the test was enough for me to see that these should now good enough to work with.

 

Bill 😊

[Bill]

Follow on from this morning’s post!

Having sorted out the battery problem they ran through a quick top-up charge and then I sat waiting for the sun to dip down so I could see them feeding the power back.

Everything now working 100% except the inverter that converts the battery power back to the mains. It was working fine when sent the batteries away for testing but now it’s a dead as a dodo. Doesn’t even light up when connected to the mains. It’s only been used for about a week if that so it’s going back to Amazon for a replacement.

Seems I just can’t win. Every time I roll a six, I end up going down a bloomin snake. ☹

 

Bill 😊