DIY Solar PV?

[490808]

Anyone doing or done their own solar PV system?

I'm in the process of setting up a small system to power a shed. Now I have mains out there already but its a suitable spot to try out solar power as a test to see how much potential there is for a bigger system.

What I have so far are two 325 Watt panels, two 12V 100Ah deep discharge AGM batteries and a 100 Volt 50 Amp MPPT charge controller. I'm still looking around for an inverter.

The charge controller is overkill but still matches to the panels if they ever work on full output. I should have a lot more battery capacity but initially I'll just use the power for 12V LED lighting until I get an inverter.

I want to get this set up in the next couple of weeks just to keep the batteries charged so I can monitor how much power I can generate if any over the winter. If you don't try you don't know.

Ideally the system will run the lights, a small compressor (around 800 Watts starting voltage) and a computer (computer will be on a UPS).

Currently I'm doing some shed repairs before doing the instal so I don't have to take the solar panels down later to do the repairs.

[kadman]

Do you think you will get to tun the compressor from the solar panel system?

[CelticRambler]

I've got three PV projects on the drawing board - one (upgrade) for the camper, one revenue-generating mega-project for the house and one relatively modest "sustainable energy" arrangement for the chicken shed that's destined to become my retirement home.

The camper is already equipped with a small panel, a couple of batteries and a charge controller, and has served as my "learning experience" over nearly two decades. The upgrade was put on hold while I was trying to sort out the emissions, then whole-engine, problem but (as I've mentioned on other threads) I want to reduce my dependency on propane, especially in respect of the fridge, as the bottles and regulators are one aspect of EU life that still varies from country to country.

As things stand at the moment, the plan is to buy the new panels and an inverter and possibly a new charge controller too, along with the fridge-freezer, and set the system up as a free-standing test arrangement while I evaluate the generation and consumption data (pretty much the same as you're doing). Assuming it all works as expected, I'll then install it onto the camper, and assemble a similar system for the chicken shed, boosted where required to allow for a more static lifestyle.

If ever that Elon Musk fella actually starts to sell his solar tiles in France, my hope would be to cover the entire south-facing roof of my house in them - about 200m². The roof needs to be re-done anyway, and my thinking is that it'd be nice to have it subside its repair costs for a couple of decades after. I reckon that's still a long way off, though. None of the get-rich-quick PV companies want anything to do with me!

[490808]

Do you think you will get to tun the compressor from the solar panel system?

Tiny compressor for airbrushing its less than 200 Watts when running and needs about 800 Watts to start. Planning on putting in a good quality 1600W inverter.

Getting it running is a nice to have rather than a deal breaker.

[490808]

Lots of gotchas I've found for anyone else doing this.

12V charging means high current. The Solar Charge controller will take the same current if its charging a 24 V battery bank as a 12 V one but the charge controller will be pushing less current into the 24 V battery as the voltage is higher. With a 12 V system 600-700 Watts is my panel limit but with a 24 V battery system I could have 1400 Watts of panels. I had to up the controller size just in case as the panels were too much for 12 V charging. However I suspect the chances of getting anywhere near the full 650 Watts my panels are rated for is very slim.

There is a vague chance with a smaller (and cheaper) 40 Amp controller my modest setup could fry the controller on a cold sunny morning as it has the potential to pump at least 50 Amps into the batteries.

I'm staying with 12 V for the time being (charge controller allows for both 12V and 24V) because so many things can run straight off 12 V. May go to 24V later if I can find an easy not to lossy way to convert from 24 V to 12 V.

Another thing I need to decide on is how the panels (Max 40 Voc) are connected series or parallel again I can do both. Parallel should be good for getting the max out of the panels in low light but series (with diodes) might be better if one panel is shaded which is more than a possibility.

[490808]

Having fixed up the front of the shed, replaced all the dodgy looking shiplap, today I find its too windy to be working with a lightweight meter by meter and a half sail so expected work is on hold.

I thought I'd reached a eureka moment over the 12 or 24 Volt battery configuration after looking at buck convertors which would do the 24 to 12 Volt conversion without massive power loss. A second eureka moment was when I realised that for "12V" lighting I could obviously use two 12 Volt leds lights in series for 24 Volts even found some leds rated for 12-30V. The trouble is if I go 24 Volt I'm thinking I'll get worse performance in low light conditions. The whole point of setting this up at this time of year is to test when the conditions are at their worst.

Here's my thinking. 12 Volt system means the panels (40Voc) should provide enough Volts even in less than ideal light conditions to get the charge controller working. With a 24 Volt system the voltage difference isn't so much so parallel panels would be less effective and because the controller can take up to 100 Volts input series would be more appropriate (up to 80 Volt input).

The reason I prefer not to use panels in series and up the input voltage is that the bottom corner of one panel will be in shade for the first hour in the morning. How much difference that will make I can only judge by wiring it all up. So think I'll start with 12 V and parallel panels then try 12 V with series panels and then the same with the batteries in series at 24 Volts. I've got some 20 Amp diodes to use to help with the shading issue. Its not a huge issue just a small corner of one panel that won't get full sun first thing in the morning.

Now my other issue is working out if I need a standard load for testing? Fully charged batteries probably won't be much of a load when getting a float charge from the charge controller? So looking on Amazon now for something like 2 strings of cheap LED lights something to use something like 50 Watts total. I'm holding off and buying an inverter for the time being.

[Osciiboscii]

Anyone do a solar powered gate? Something I saw in a farm magazine years ago, and wouldn't mind applying to our gate, especially now that a greenway is being developed just outside. The downside, from my pov, is that incomers i.e. postie..would need a zapper (for this particular set up).

[490808]

Assume your postman is in a van? In which case all you need is an inductive loop in the road outside the gate. Normally it the inductive loop won't trigger the gate but you set it on a timer so it does when the postman arrives.

[490808]

Finally got it all up and connected. Its a little temporary but wanted to make a start collecting some data to see how much use it could be and if its worth expanding (well actually I'd do another complete bigger system). Spent last night making up leads with crimped terminals.

No sun yet on the panels and my 650 Watt array is producing a massive 3-7 Watts

At least that proves I've wired it up correctly.

Have a Victron 100/50 "Smart" controller (bluetooth) and not that impressed, took ages to connect and seems I need to reboot my phone if I can't connect Also bought a USB cable and that won't work at all although its detected and installs under Windows (also no support for bluetooth with Windows double ).

Off out now but as soon as I'm at home with the sun out I'll be checking what the output is

[SouthWesterly]

Does anyone know anything about the use of micro inverters instead of the standard one.
They seem to be perfect for a ground mounted system

[490808]

My guess is that you aren't allowed to use them on a system that is grid tied. How do they know the powers off if someone is working on the line?

[490808]

OOOOOOPS

Had been wondering why after the massive peak of 7 Watts produced per hour I was only seeing 5 Watts being produced

Turns out because I'd previously charged both batteries so they started life off equal 5 Watts was all that was needed to maintain the batteries on float charge.

Today I added a small 12V load, a cheap desktop fridge that has a fan in it. Now I can see 65 Watts total which is perfect. Now I can ramp up the load until I reach the max when I start using charge stored in the batteries.

[SouthWesterly]

My guess is that you aren't allowed to use them on a system that is grid tied. How do they know the powers off if someone is working on the line?

Surely they are no different to the standard inverter in it being the inverter is connected to the fuse board.

[490808]

My understanding is that the connection to the grid has to have a disconnect that engages if the power goes off.

So if there is a power cut your grid feeding solar doesn't work.

[CelticRambler]

Does anyone know anything about the use of micro inverters instead of the standard one.
They seem to be perfect for a ground mounted system

Only what I've read here.

I've known for a long time that shade on a few cells can affect the overall performance of a single panel, but this article suggests that shade on one panel will reduce the output from the whole array if you're using a standard ("string") inverter. Is that right?

[SouthWesterly]

Only what I've read here.

I've known for a long time that shade on a few cells can affect the overall performance of a single panel, but this article suggests that shade on one panel will reduce the output from the whole array if you're using a standard ("string") inverter. Is that right?

That seems to be right. That's why they use optimisers on panels that will be shaded.

[490808]

That seems to be right. That's why they use optimisers on panels that will be shaded.

Any panels in a series string will be affected by shade the voltage reduction on one will be replicated in the other. Panels in parallel then you can use diodes so only the panels that are shaded are affected. However that only seems to be a useful solution on small setups like mine. On large installs you are likely to have strings of panels in series and afaik all the panels in a series string will be affected by shade on one panel.

[SouthWesterly]

Any panels in a series string will be affected by shade the voltage reduction on one will be replicated in the other. Panels in parallel then you can use diodes so only the panels that are shaded are affected. However that only seems to be a useful solution on small setups like mine. On large installs you are likely to have strings of panels in series and afaik all the panels in a series string will be affected by shade on one panel.

From my reading they only become uneconomical due to increasing costs. Doesnt mean they can't be used.
A, user on boards got them on an 8 panel system from the SAAS provider. He posted a link to an article on them

[490808]

Another small update. Finally got around to buying an inverter, which of course means all change again for the way I'm thinking about the system.

What I bought was a Victron Energy Phoenix Inverter 12/1200 230V VE.Direct UK if anyone is ever buying one they do versions for all the main plug systems, the UK at the end means you get a UK 13Amp socket built in. Of course buying this means I need to spend more money. I'll probably get the bluetooth adapter for it and have already bought more (thicker) cables.

First thoughts are its a beast of a thing. I know the dimensions and weight are no secret being on the specs but I was surprised by its size and how heavy it is. Comforting almost that is bigger and heavier than a cheap chinese inverter that is rated for twice the power. I suspect I could have bought a less powerful inverter for this project but at least I shouldn't be burning it out.

I had hoped to get away with 18mm2 cable for the 12V input cables but I've just had to go and buy 25mm2 so everything has the potential to run at full power. I'm also going to double up on the batteries (4x 12v 100Amp total) which should give me the potential for running a 1200W device for 2 hours.

The reason for the project is related to the issue that I'm finding that there is little sensible information on sizing relative components. While some areas are very specific and well documented like cable sizing the relationship between panels/battery/charge converter/inverter are much less so. The info for the cheap chinese stuff would have you believe that you can run massive power tools off a car battery. The reality is far from that. As I've mentioned I'm using 25mm2 cables because thats the size needed to supply 100 Amps at 12 Volts for max output. Some simple figures are a 3000W 12V inverter would need to draw at least 250 Amps from a battery which would require 70mm2 copper cables on the 12V side and run for no more than a few minutes if at all from an average car battery. I was just looking at one cheap chinese inverter that is rated at 1500W and it comes with a cigarette lighter adapter - which will blow the fuse anytime it produces more than about 240 Watts if it didn't cause a fire first.

Anyway here's how I will have everything sized at the moment. I've another project in mind so little here except cable will be wasted if I need to rip the whole thing apart and start again. Next time might be a 24V system to reduce those cable sizes a bit.

Panels: 650 Watts total 2in series providing a max of 80 Volts at 10 Amps to ....
Charge controller: 100V max in, 40 Amp at 12V out, charging ....
Batteries: 400 Amp hour made up of 4x 12V Gel batteries in parallel (have 2 getting another 2), max usable current 200 Amp powering ....
Inverter: 1200W (will run at 2000W for starting loads)

The estimated load is currently only around 150W (computer router, wifi etc) which the system should keep running for at least 12 hours. How that works out and how the panels will keep up with recharging is yet to be seen. I've only connected everything up for a trial run so far. The wiring needs some work as I've switches, fuses, an RCD and an earth rod to incorporate before its fully functional.

[CelticRambler]

I had hoped to get away with 18mm2 cable for the 12V input cables but I've just had to go and buy 25mm2 so everything has the potential to run at full power. I'm also going to double up on the batteries (4x 12v 100Amp total) which should give me the potential for running a 1200W device for 2 hours.

Daily reality for us motorhomers - even without inverters If you can bear to trudge through the archives on the Other Forum, you'll find a huge amount of technical info posted by SirLiamalot about this topic. Too late for you now if you've already bought the 25mm² cable, but he's a great fan of Aldidldi's booster cables as a source of really thick copper cable at a ridiculously low price.

[490808]

Local electrical supplier has what they call Panel Flex. Does what I want 25mm² €4.30 a meter including VAT, plus I can pick up the crimps I need at the same time.

I read most if not all of SirLiamalots stuff and I'm already going against him by using a Victron MPPT charge controller.

Found this little tool very useful btw



I could borrow a much bigger tool but find that one much handier. Don't use a claw hammer on it like the pictures show it needs at least a 1 kilo lump hammer to do the job in one without messing.

[CelticRambler]

Well, sometimes Google is a force for good! A news article yesterday made reference to the "dragon scale" PV roof on one of their new buildings in the states, which a bit of ... well, googling, obviously ... led me to discovering that the manufacturer is almost local to me, a Swiss-French company SunStyle.

For my mega-project (mentioned above) their diamond tiles are very similar to a type of slate that's already fitted to the habitable part of my building, but unlike Elon Musk's product, they are actually in a position to deliver them! RRP 250€/m² exVAT and they've answered my enquiry with an invitation to discuss the project in more detail.

A very quick back-of-envelope calculation suggests that such a roof should be well within the "self-financing" bracket, and make a significant contribution to my retirement income once the installation costs were paid off. Will set up a meeting with them for a couple of weeks' time when I'm off work. Maybe see if they can be persuaded to consider a "poster boy" discount for a landmark property.

[CelticRambler]

Well, that was interesting. The man says (having studied my roof from afar) that I should be able to generate approximately 40MW on a good day with his tiles, which roughly matches my own calculations. He upped the installation price, though, to take account of the multitude of accessories and labour, bringing it to around 400€/m².

I need to look further into the grants and incentives side of things, but it looks like there's a new incentive available for installations that are "suitably integrated into the rural landscape" which is nice, as that's been my over-riding criterion. On account of my professional laziness, I might also conveniently fall into the category of "household of modest means" and get something in that regard. On the other hand, there may be some advantages in creating a new fiscal identity ...

All things considered, the project looks "viable" in the short term and "profitable" in the medium/long term ... but it'll stay on the long finger for now. An appointment with a suitably well-informed and creative accountant will be my next step. I also need to first strip and repair the roof structure - a project that's already two years behind schedule. And then there's the wait time - currently around six months from when the planning application gets the green light.

In the meantime, I've blown half a month's wages on a massive load of insulation for the chicken shed!

[490808]

40MW? Thats as much as a small power station (well a very small power station). 40KW perhaps?

At approx 200 Watt per square meter output with modern panels for a 10 meter x 4 meter roof you could have 8KW worth of panels and for an 8 hour sunny day generate 64KW of power.

If you take a standardish 400 Watt panel you'll find its about 2 square meters in area and costs about €200 (or much less)

So actual panel cost without any fancy roof tile innovation or mounting system is less than 100€/m². If I go by the cheapest Irish prices I can find and picked up the panels myself I could probably get that down to 75€/m².

Whichever way you look at it you need to get a lot of extras for your 400€/m².

I assume this is grid tie only with no battery backup?

[CelticRambler]

It's meant to be a mini power-station. The southern half of my roof (so about one fifth of the total roof) is about 240m²

For various future-project reasons, I'd be opting for the "sell-the-surplus" model. I can't/won't use standard panels - my house is too much of a landmark property, and it would seriously devalue the "look" of the front, which is something that I want to capitalise on in respect of at least a few of those future projects. Also, as I'll be going for maximum output, the (much) smaller tiles can be configured so as reduce the surface area affected by shadows cast by dormer windows planned for the upper floor.

I didn't push for any concessions at this stage because I'm not ready to move forward with it. I did establish, however, that they have no installations in this region for me to look at - so if that's still the case in a couple of years, I'd be suggesting that my house (so traditional and visible as it is) would make for a good reference property ... and justify a bit of a reduction. They do have one of their roofs on a church not far from where I work, so I'll have a look at that on my way over at the end of the month.