Spacey73

Run a large Solar Farm as a business. House power is separate and off grid DIY without export. A mere daisy in a large field of daisies

The thing is…is that prices are changing as fast as our prime ministers. I can’t base a long term purchase on prices that might stay or might be taken away. Off grid is aim but with grid as backup should anything break. Battery essential for this 2hrs of breakthrough sunshine powers house for day.

It’s the big green one that I overpaid for as I’ll never use battery backup…doh could have saved £300. It’s on the Voltacon website hybrid 48v inverters for about £1,600. Using the 8kw one from there as well for way cheaper when it’s finally got the new board fitted.

I might have to do a sneaky economy 7 charge from 01:00 to 06:00 at £0.14 (compared to day rate of £0.46 now) for Nov Dec jan, but maybe not. 34kwh of battery and 14kwh of Sunamp hw storage, 34 x PV panels at circa 380w all facing perfect south and I can adjust Deg of panels really easily as ground mounted single rail design. Car has its own 9 x 540w supply on car port. Will be interesting to see how this goes.

I can not justify the cost of ‘installed’ batteries. I bought 16 x 320ah Eve automotive lifepo4 cells, a really good 200a BMS fully programmable in a solid steel case with display. 17kwh for £3,400. So good I bought 2. Cells will die from age before they run out of cycles. Now it’s getting harder on a cloudy day for solar I’m just charging on cheap £0.14 kWh to 30% and then use battery at 7am at £0.42 and wait for solar to catch up depending on weather. battery is called Seplos.

My neighbours spent or were conned into buying £52k worth of heat pump ground source for underfloor heating and radiators in a very leaky old cob farmhouse. It’s so expensive that they have only turned it on twice allegedly. They poo poo’d my idea of putting in the 2 x heat pumps which run 5 x air conditioners in an 80’s built bungalow. Its been a month since they were installed and I’ve set the 1,900 square foot building to 20 deg C. It is so damn energy efficient and we have no radiators at all or awful copper piping running all over the place. Oncr the bungalow got up to temperature the power used settled down and is powered by the one set of solar panels dedicated to the hot water and heating….not even connected to the grid. 12 x 390w ground mount panels seems to be holding up nicely so far. So I think air conditioning is the way for leaky buildings (I have. Positive air pressure system as well to sort out damp and have constant fresh air coming in). I’m not convinced on Heat Pumps when you use radiators unless in very midterm houses.

The higher the PV voltage the less strain on the wiring. I’m also in a similar situation where I have a 50m run from PV to Workshop then 15M to Garage where inverters and battery are. I have 3 sets of ground mounted panels (Waiting for the ‘do you have planning permission’ nimby remarks….) that are running at around 430v DC each. Downside is that I have to run 3 sets of 2 cables as I have 3 x mppt inputs on inverters that are maxed out with 12 panels (1 string) so can’t parallel them up. Inverter and batteries are very close to main house distribution box and do a zero export similar to the ct clamp method. It really is best to go DC from PV to house then convert to AC at that point. Modern inverters will take up to 500v to 600v on mppt inputs. 6mm PV cable at 10amps max should give good voltage loss results.

I was thinking originally of getting Tesla powerwall but after looking at the specs and cost kit didn’t look as awesome as the unit does in person. I’ve grabbed 2 x 17kwh lifepo4 batteries each in a very sturdy case with a decent 200Amp BMS that’s fully programmable. Each battery can pump out 10Kw if needed and be charged each at 5Kw. Price was £3,400 inc all import duties and shipping. Legit Eve 320ah cells and works like a champ. New tumble dryer Miele heat pump trickles electric so we use it without thinking about it. 34Kwh of useable battery for £6,800 seems like a no brainier and should pay back relatively quicker now with silly high electric rates. But you do forego any export.

If I only had a terraced roof as an option for PV or a small garden then yes, heat pump for HW supply would make sense efficiency and all that (high upfront cost espy with installation). But I’m in a unique situation where I can add more solar than I could possibly use all year round. I’m not needing to worry about electricity availability, panels are cheap as are 48v mppt inverters to charge battery. Roughly 12kw solar at the moment, easy to add more and about £2k per 4kw module (including fixings). I’m sure a mini nuclear realtor would be even more efficient energy transfer for HW but at some point cost, servicing and complexity (moving parts mostly) are just not worth the efficiency gains. Plopping in a dedicated south facing 4Kw array (already have 2 x 500v open voltage mppt spare) just for HW does make sense to me. so many out buildings facing the right way at a good angle seems a waste not to use it, ground mount ‘fence’ system doing really well performance wise. I already have 2 heatpumps, really don’t want a 3rd

I guess for me it comes down to: 1: Buying a Heat pump to charge up the Sunamp. Pro’s: Possibly 3 times less kWh of electricity needed to charge it. Cons: That would mean 3 Heat pumps on the side of a Bungalow instead of the 2 we have already. Very expensive to buy and have installed. To reach temps needed to charge up Sunamp I have a feeling efficiency goes down a bit. Something else to service. or……. Just adding some more Solar panels to the setup. Conclusion: My circumstance is probably very different to 90% of people installing Sunamp’s in that I have the space to install a lot of solar panels….and the spare inverter mppt inputs already installed to not add anymore cost other than buying say 12 x 390w panels at £160 each. I’m pretty sure a 5Kw solar setup dedicated solely for charging up the Sunamp would cover just about all it’s charging needs, and for those days it doesn’t there is always the house/grid (which is already alll powered by a large solar installation and 2 x 48v 320ah Lifepo4 batteries. Installation is free as I will do it, Solar panels are way cheaper than another heat pump plus no servicing. When you have enough space to add this solar array just for hot water then 1 to 1 efficiency still works out cheaper and less hassle. Just because someone has a different idea or way of doing things isn’t a reason for some to get all uppity and grumpy old man syndrome just because I’m not conforming to their ideas they put forward. Financially it makes sense for my situation and aesthetically (panels out of site on out building roofs and field) too. Currently have Air Conditioning on holding a 1,900 square foot Bungalow at 22 deg C 24/7, cooking on large electric aga, tumble drying with heat pump dryer, washing electric, dishwasher, charging Zero Electric ride on mower (1.5kwh battery) 4 charges to do field and lawn….. and lots of lights appliances etc ……… and still end day with over 60% battery and wake up to over 30% battery. This is with a family of 4. Sure it will get harder as Sun goes down, but my last house managed it and also running a bitcoin farm off Solar. I do not want Oil or gas on the property and I also do not want to be at the mercy of whichever idiots are in charge of the country deciding when I can use my appliances or and silly carbon credit restrictions that are very possibly coming down the line.

This is true, but mine has a switch over setting for this scenario and will power the house. It takes 10ms to switch over, as soon as it detects a grid signal again it goes back to islanding mode again.

Hardly compact solution that cylinder is it? Hot water heat pumps are also not that efficient for those high temps needed, very expensive also. Really don’t want a 3rd heat pump hanging off the house. 3kw is the charging rate of the Sunamp, with an already large solar array and 32kwh of house batteries (Tesla S already catered for with its own solar car port setup and buffer battery)….. I don’t see me having any issues putting a 10kwh charge into Sunamp. largest system was £3.8k I think, plus £1,200 for an extra set of solar panels. I have 2 spare mppt connections on the 8kw off grid inverter. I think the price is pretty reasonable, air to air system up and running and very efficient. Went to bed with 76% left in battery ….also 75 miles put into Tesla and only the standing charge to pay for electric. Not sure why my setup is so stupid?

That’s a really spiteful thing to say to someone you don’t know. Full of bile….cheers for that. why would I buy a high temperature heat pump (yet another large thing hanging off the house looking not so awesome) which costs a lot of money compared to normal temp heat pumps…just to heat up the water tank efficiently…only for said water tank to inefficiently lose heat/kWh as they do and also mix in colder water as you use the hot water. Really don’t get the snarky attitude, seems to be the way of things these days. I have 3 acres of area to ground mount Solar so I would rather add cheap £1,200 per 5Kw modules and haven’t overkill on Solar to cover winter (with grid back up for emergencies) to cover slack in winter output. I just don’t want another heat pump hanging off what is a really nice country bungalow which has 2 already

Simple really, Sunamp goes where the boiler was in garage and the large immersion tank goes to scrapyard and bathroom gets extended into a wet room. I can charge Sunamp at 7.5p a kWh for 5 hrs on Octopus if I have to, but will most probably be fine using solar power to heat it during day even in winter. I hate that heating the water tank gets scuppered as soon as you use some of it as cold water is put back in to the mix reducing its temp plus the 2kwh at least a day loss. I can always add more panels ground mounted (came up with a really good cheap fit mount that can be angled as well), for future proofing.

I never said it does do central heating? I said I don’t like radiators or oil …so when I get rid of the radiators and instal 2 x Heatpumps and 5 air conditioners….I’m going to need something heat the water. Maybe something half the size and doesn’t lose energy so quick. Hence Sunamp. you can actually use them for central heating but I don’t see many benefits for that. Didn’t cost £6k more like £4.5k all installed, plus I’ll be scrapping all that lovely copper piping.