(Semi) off-grid solar thoughts

[m_c]

This is an idea I've had for a while, but given the cost of electricity, I'm wondering more about the feasibility.

I've now got a couple 3D printers that run for a good few hours a day, along with some other electronics that run 24/7, so I've been wondering about making more use of solar power.
For various reasons, a grid-tied system isn't feasible, so I've been thinking about the various standalone power banks you can get, such as https://bluettipower.co.uk/products/bluetti-ac200p-2000wh-2000w-portable-power-station

The basic power station is actually not that badly priced given the specs. A quick search puts 2000WH of LiFePo4 batteries around £1000, and a 2000W pure sine wave inverter are under £500, so for all the other bits included in the powerbank, it's not that badly priced. However the cost of the official solar panels are expensive (£900 for 350W - you can get 400W for £300..), and it's £1500 for each extra 2000Wh expansion battery pack.

So I'm thinking off a more modular DIY system, that can be added to.
LiFePo4 batteries (pretty stable, and should be far more reliable than Lead Acid, and with more useable capacity)
Sine Wave Inverter
Solar panels + charge controller
Mains charger.

My plan would be have some form of battery management system, that monitors battery state of charge, solar input, power output, and then if needed top-up via the mains charger.


So anybody got any thoughts/input on this idea?

 

[James1979]

Haulier I work for got an eco flow come through with no labels on it. Whoever sent it didn’t want it back. Result.

He uses it in his ‘bar’ in the shed. It powers the lights and a tv (but not sure what that is exactly) as well as other nonsense and he’s quite taken with it.

They are popular. Torbjon Ahmann reviewed one recently and it seemed good. I think the one that the guy I know has retails around the £800ish mark

 

[gaz1]

theres a few posts on this subject already

time to go solar i think

good day folks, i have at the bottom end of my property an old wooden hay barn that has not been used for years, as i have now retired i have plans to convert part of it to a log cabin as it faces out across a large pond with scenic views and miles from anyone, the building part and...

www.mig-welding.co.uk

Solar power on roofs - more viable with energy price hikes?

When the Feed In tariff dropped significantly a few years ago, the idea of filling my roof with solar panels was less appealing. However with the current energy situation (even though we got a 2 year fixed rate deal last August) I wonder are solar panels the way to go to reduce energy costs -...

www.mig-welding.co.uk

 

[julianf]

You can get second hand panels real cheap now. The last two sets I bought were £650 for 3.5kw and then a bargain £400 (iirc, it was less than £500 with certainty) for 4kw.

Viktron would have some offering to charge batteries off them, and would probably be quite flexible as to the battery type.

There are hybrid inverters comming out now that do batteries, grid, generator, ev etc all in one package. But they are more along the money you are on about (ie more than I like spending! : ) so I don't know much about them.

 

[Domdom]

You can get second hand panels real cheap now. The last two sets I bought were £650 for 3.5kw and then a bargain £400 (iirc, it was less than £500 with certainty) for 4kw.

May I ask where from? I’ve been looking for something around 2kw ish just to power the house during the day. Can’t find anything.
Thanks.

 

[julianf]

May I ask where from? I’ve been looking for something around 2kw ish just to power the house during the day. Can’t find anything.
Thanks.

The more expensive set was off Facebook, but a commercial (ish) seller. Ex solar farm stuff. Based in Cardiff. I saw them again the other day so they're still active if you have a bit of a look. I think I paid £65 each for 350w panels. I don't know if that makes sense with the numbers I quoted before?

Second lot, again, were off FB, but a private sale. Was an incredible bargain. Panels listed individually but the chap said that, if I bought the lot, I could have all the mounting hardware foc. And then a while later he called me up and asked me if I wanted the inverter also (again, without charge).


None of them are doing me any good though, as they're currently in a shaded position. In a barn.

 

[frank horton]

well we are making plans to go totally off grid over this winter for next year......luckily we have a lot of sunshine,,,,
trying to get prices now.....
our bill has gone from 100euro's per month up to 400 for the same usage.....all this in under 4 months......
so Fxxxx em.....
ps, here your house taxes / rates are based on ur electric consumption....
ie the richer u r the lecky u use.....

 

[dyno-tron]

Have a look at voltaconsolar.com, they have some well priced gear - batteries - panels etc, I got a ground frame for 8 panels from them, excellent quality. And also solarsparky.

 

[julianf]

We have enough roof space Vs usage to go off grid for electricity IF storage was more feasible.

For a while I considered trying to harvest hundreds of 18650 cells, but never got over the initial bump on the acquisition curve.

 

[minimutly]

This is an idea I've had for a while, but given the cost of electricity, I'm wondering more about the feasibility.

I've now got a couple 3D printers that run for a good few hours a day, along with some other electronics that run 24/7, so I've been wondering about making more use of solar power.
For various reasons, a grid-tied system isn't feasible, so I've been thinking about the various standalone power banks you can get, such as https://bluettipower.co.uk/products/bluetti-ac200p-2000wh-2000w-portable-power-station

The basic power station is actually not that badly priced given the specs. A quick search puts 2000WH of LiFePo4 batteries around £1000, and a 2000W pure sine wave inverter are under £500, so for all the other bits included in the powerbank, it's not that badly priced. However the cost of the official solar panels are expensive (£900 for 350W - you can get 400W for £300..), and it's £1500 for each extra 2000Wh expansion battery pack.

So I'm thinking off a more modular DIY system, that can be added to.
LiFePo4 batteries (pretty stable, and should be far more reliable than Lead Acid, and with more useable capacity)
Sine Wave Inverter
Solar panels + charge controller
Mains charger.

My plan would be have some form of battery management system, that monitors battery state of charge, solar input, power output, and then if needed top-up via the mains charger.


So anybody got any thoughts/input on this idea?

A few years ago I put together a system using a415V ups battery pack - individual 12V yuasa lead acid bats in two series strings in parallel, something like 500V from memory. The issue I had was ensuring that any battery that was weak would have an increased internal resistance, thereby reducing the charge current for that string.
The answer, which I never got to implement was to use a Rasberry pi to read individual battery voltages, and at least give an indication of any duff bats. Depending on charging voltage you could potentially use relays to charge individual batteries, but I confess this didn't go anywhere.
What happened was that in trying to increase the inverter output I overdid the number of batteries and fried the inverter...
Edit to add what I've said before, going off grid in the UK needs a backup for the winter months - either a generator or wind turbine. If you had 12kW of solar it still won't be enough, perhaps 40kW might do it, on the basis that our 4kW gives us 150W during daylight on some winter days. I dunno though, this is just my best guess.

 

[Gareth J]

What are the various reasons a grid tied isn't feasible? You can have both grid tie and batteries.

 

[m_c]

What are the various reasons a grid tied isn't feasible? You can have both grid tie and batteries.

The ideal location for solar panels is on the workshop roof.

However the workshop is fed via overhead lines. Ye older exposed conductor type, as originally the workshop had it's own meter, with the wiring being an extension of the overhead lines to the house. When the house was extended many years ago, the main supply was buried, and now essentially comes up under the extension to the meter. At the same time, the workshop meter was removed, and power connected to it's own standalone RCBO, but still fed via the exposed wires.
So there's no easy way to add a connection before the consumer unit/RCBO. Even when the phone line which is next to the consumer unit had to be renewed, it had to be drilled through an exterior wall in a bedroom, run ~2 ft along a skirting, through the door standard and up to a new master socket. Any electric cable would also have to routed in a similar way.

To further complicate things, there are other sheds taking a feed from the overhead wires at the house end, so it's not like they only power the workshop.

As much as I'd like to do a grid-tie system, the practicalities make it problematic. It wouldn't be impossible, but it would involve quite a bit of expense, time, and effort.

 

[Gareth J]

The ideal location for solar panels is on the workshop roof.

However the workshop is fed via overhead lines. Ye older exposed conductor type, as originally the workshop had it's own meter, with the wiring being an extension of the overhead lines to the house. When the house was extended many years ago, the main supply was buried, and now essentially comes up under the extension to the meter. At the same time, the workshop meter was removed, and power connected to it's own standalone RCBO, but still fed via the exposed wires.
So there's no easy way to add a connection before the consumer unit/RCBO. Even when the phone line which is next to the consumer unit had to be renewed, it had to be drilled through an exterior wall in a bedroom, run ~2 ft along a skirting, through the door standard and up to a new master socket. Any electric cable would also have to routed in a similar way.

To further complicate things, there are other sheds taking a feed from the overhead wires at the house end, so it's not like they only power the workshop.

As much as I'd like to do a grid-tie system, the practicalities make it problematic. It wouldn't be impossible, but it would involve quite a bit of expense, time, and effort.

So long as the overhead lines are up to it (big enough) what's stopping you connecting into the consumer unit in the workshop. I've got two PV setups here that are grid tied but don't go all the way back to a Henley or, one, even the main distribution board.

 

[m_c]

So long as the overhead lines are up to it (big enough) what's stopping you connecting into the consumer unit in the workshop. I've got two PV setups here that are grid tied but don't go all the way back to a Henley or, one, even the main distribution board.

My understanding was any grid-tie had to be done before any consumer unit, so you didn't end up feeding in after RCD/MCB protection (and hence reducing/bypassing the circuit protection).

Which if I was to do before the consumer unit in the workshop, would mean the other sheds which rely on the RCBO for the overheads for protection, would lose that protection :/
Everything really needs a big re-wire, but I'm trying to ignore that for now.

 

[dyno-tron]

My understanding was any grid-tie had to be done before any consumer unit, so you didn't end up feeding in after RCD/MCB protection (and hence reducing/bypassing the circuit protection).

Which if I was to do before the consumer unit in the workshop, would mean the other sheds which rely on the RCBO for the overheads for protection, would lose that protection :/
Everything really needs a big re-wire, but I'm trying to ignore that for now.

Don’t know if this helps but our PV is fully mcs certified & grid tied. PV is on the garage roof, inverter in the garage feeds into garage CU via a 32A mcb. Garage is connected to the main house CU via a 32A mcb. Energy gadget monitors flow via clamp on main incoming feed cable and reports back to inverter via dedicated data cable. Professionally created diagram attached.

 

[Gareth J]

Don’t know if this helps but our PV is fully mcs certified & grid tied. PV is on the garage roof, inverter in the garage feeds into garage CU via a 32A mcb. Garage is connected to the main house CU via a 32A mcb. Energy gadget monitors flow via clamp on main incoming feed cable and reports back to inverter via dedicated data cable. Professionally created diagram attached.

View attachment 359375

I've a very similar setup, minus the battery. Mines not certified though.

 

[Chris Snow]

If you're willing to go completely DIY I imported 30kWh of LFP prismatic cells from China for about 4 grand, Victron quattro running as ESS. Not bothered with solar just using 7.5p off peak EV tariff and discharging in the day.

 

[8ob]

Batteries seem to be the biggest expense/financial stumbling block, I am surprised more folk haven't tried making their own, lead acid batteries would or could be made relatively easily.

Bob

 

[Chris Snow]

lead acid batteries would or could be made relatively easily

Lead acid isn't really suitable for cycled energy storage. Poor depth of discharge and round trip efficiency.

 

[m_c]

Don’t know if this helps but our PV is fully mcs certified & grid tied. PV is on the garage roof, inverter in the garage feeds into garage CU via a 32A mcb. Garage is connected to the main house CU via a 32A mcb. Energy gadget monitors flow via clamp on main incoming feed cable and reports back to inverter via dedicated data cable. Professionally created diagram attached.

View attachment 359375

I'm guessing both your consumer units contain RCD/RCBO protection, so any connected/powered devices are still protected.

This is the setup I've got to work with -

Red is the exposed overhead.
Green SWA
Blue a mix of insulated overheads

The problem I'd have, is if I connect into the exposed overheads, it then means the three sheds with just old fuse boxes potentially don't have any RCD protection. Biggest load in those three sheds other than lighting, are some woodworking tools (2kw load at most).

As you can see, going grid-tie could open a big can of worms, and need quite a bit of work, which is why I was thinking more about off-grid :/