Run house off batteries during the day, no solar.

[Roger440]

I'd love to kit out my future house with solar panels and a generator to charge batteries. Off grid potentially. Use solar as much as possible but run the generator as needed off recycled chip fat (probably twin tanked and water injected). Run a heat exchanger on the generators cooling system to heat the hot water too. Would cost so little to run and yield full use of mod cons.

Before i bought this house, we looked at an off grid house.

All do-able as you suggest, but even DIYing a lot of it, its still cheaper to be on the grid. I spent a lot of time doing the maths on that. Real maths, not man-maths!

Its an expensive way to live. More so if you use a fair bit of power as i do with compressors and machinery etc.

 

[Roger440]

Do you know of this? It looks similar to the scheme in Scotland. I don't know much about it but friends who had it done out here seem happy with it.

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Theres a fair few schemes. Because i have a job, im excluded. I have considdered not having an income so i could claim.

However, in the context of my issues, it doesnt actually help, as its my workshop where most of the electricity is being used. No grant covers that. And my house is heated with oil.

 

[Roger440]

Would an EV with a bidirectional charger on interest free finance be economically viable?

Bob

Had pondered this. Seems most newer stuff doesnt allow it.

Ive got myself to a position of not owing anyone anything. Keen to keep it that way.

But an old nissan leaf or such like makes some sense rather than a battery strapped to a wall. But its not much "cheaper" as an overall solution, but does get you a cheap runabout at the same time.

 

[8ob]

Had pondered this. Seems most newer stuff doesnt allow it.

Ive got myself to a position of not owing anyone anything. Keen to keep it that way.

But an old nissan leaf or such like makes some sense rather than a battery strapped to a wall. But its not much "cheaper" as an overall solution, but does get you a cheap runabout at the same time.

Curious to know whether there is enough capacity in an EV battery to power a house through the day, if it would then it kind of makes economical sense.

Bob

 

[Roger440]

Curious to know whether there is enough capacity in an EV battery to power a house through the day, if it would then it kind of makes economical sense.

Bob

Ev battery pack is usualy bigger than a house battery, so yes.

But the vehicle manufacturers actively prevent you from feeding the house. Understandable from a warranty perspective.

 

[gaz1]

@Roger440 personally id be looking at 2 sand stores you have the building for it

add that to the fact it can be solar charged and stored heat for winter extra solar panels can be used here

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it runs a town to give you an idea its also recharged up in winter by the grid though as it does run a town
8mw

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A new industrial-scale 'sand battery' has been announced for Finland, which packs 1 MW of power and a capacity of up to 100 MWh of thermal energy for use during those cold polar winters. The new battery will be about 10 times bigger than a pilot plant that’s been running since 2022.

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with a kitted out system 8k for price reference here can be used with the grid as well

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[jmp49]

Thanks for the detailed reply.

Im assuming from this, you self installed? I have no interest in paying for an "MCS certified" installation, mainly on cost grounds, and because ive no intention of lining the pockets of said organisation (probably for another thread!).

Ive done most of my own electrics over the years, indeed was qualified way back in the early 90's, but i really struggle to understand how to wire and connect it all up. It seems hard to get clarity on what exactly i would need to do. Invertors seems to be an unfathomable minefield.

My intention, like you was ground mount. Workshop roof, whilst large is shaded from early afternoon onwards. I do have a decent sized field with a clear view of the sky in the south, so intended to put it there.

Whilst id love not have batteries, the reality most of my annual usage takes place in the winter, inclusing use of the compressor etc. And batteries is where the big costs are.

Yes, but note my location. But its the same sort of deal here, you have to have it installed by someone registered as a installer and qualified to get access to any grants or payment for the electricity if you feed it in. But its treble or more the price of the autoinstall kits which are limited to 3kw feed back and have to plug in to a normal 16a socket.
Installation of the system was easy, just assemble some brackets, screw them pallets with big lag bolts and lay some steel scrap (actually some sections from a jcb back digger) across the back of the triangle to give them a strong platform in the winds we see here now and secure the panels to the stands with the stainless nuts and bolts provided. Others we weighed down with blocks filled with sand and the inverters screwed the back of the frames behind their associated panels, each inverter serving 4 panels. Electricity-wise, the dc side leads came in the kit and just plugs into their micro inverter. Then on ac side, the micro inverter just plugs into a wall socket (this is a legal thing here for auto consumption panels and the only reason they're legal without a professional installer). I ran some feeds terminated in ip65 sockets out to each area dedicated for them. Nothing has got wet or moved even when the wind tore bits of the house roof off recently.
To get data and stats OUT the inverters so we knew what we were generating, I installed opendtu https://www.opendtu.solar/ onto two arduino's, and soldered up a lead for the recomended modem to match and ran some coax outside to near the inverters to connect to them, then I feed this data into a homeassistant instance although it has its own web interface to give realtime stats on each panel. We used this info over a few weeks to tweak the individual panels direction so they gave a good spread of power throughout the day, rather than having them all facing the same direction so they yield a high amount of generation but very peaky for a hour. Opendtu only covers hoymiles micro inverters, but possibly there's something similar for other brands.
For the mains 3phase side, the mains tails from the meter passes through a shelly pro 3em metering device that has 3 clamp ammeters so its not needed to break into the edf section of the wiring to measure, and that feeds into the homeassistant instance too. Then some scripts turn on loads based on figures supplied from the shelly on returned power to the provider in realtime.
I can get stats from edf's meter, but its not realtime so you cant load shed in real time on its readings, only know what you have consumed hence the shelly meter on our side of their meter.
The homeassistant side isnt strictly needed as you can see all the realtime data in the dtu's web interface, but it does log and make really nice graphs to give you a good insight, but its a bit of a techie toy. You have the power consumption to run the smart devices and the homeassistant server, be it a raspberry pi or what, currently I'm running it in a virtual machine actually installed on my fibre router that has to be on anyway.
I know a few here run it also, if you were interested that would be a topic on itself though.
Total price for the 3Kw kit with everything was 1200e delivered on a pallet to my address in a deal we found online, so a thousand quid. The second set, we just waited for another special deal to appear and did the same & used the same inverters/panels etc as we already knew all the components needed and how to configure them. We'll never feed back more than the 3Kw limit, because if that figure is approached even with loads by some miracle sun situation a automation turns down the max generation wattage down in the inverters themselves so theoretically we could add more without breaching the regs still.

 

[lazybones51]

Ev battery pack is usualy bigger than a house battery, so yes.

But the vehicle manufacturers actively prevent you from feeding the house. Understandable from a warranty perspective.

More manufacturers are coming on board with V2H. There are various different specifications cars and chargers can support. Well worth a read https://www.cleanenergyreviews.info/blog/bidirectional-ev-charging-v2g-v2h-v2l

 

[gaz1]

More manufacturers are coming on board with V2H. There are various different specifications cars and chargers can support. Well worth a read https://www.cleanenergyreviews.info/blog/bidirectional-ev-charging-v2g-v2h-v2l

with ev companys you cant tell me that they dont know that the ev battery has been used as a house charger as they can

as it would show the vehicle hasnt moved much
it would also show how many times its been charged and discharged

therefore they have plenty of wiggle room to get out of replacing that ev battery as its not being used for the purpose it was designed for

 

[Pete.]

with ev companys you cant tell me that they dont know that the ev battery has been used as a house charger as they can

as it would show the vehicle hasnt moved much
it would also show how many times its been charged and discharged

therefore they have plenty of wiggle room to get out of replacing that ev battery as its not being used for the purpose it was designed for

If you buy a V2H vehicle and use it to power your house it absolutely has been used for the purpose it's designed for.

 

[Gareth J]

Your last comment is my thoughts exactly. It seems like a big gamble based on the system not going wrong, and electricity prices staying where they are or higher. Niether are a certainty.

There are lots of other things that can help to prioritise energy savings and storage before adding batteries;
-Defer electrical usage to periods of high solar generation e.g. pump up compressors, run dehumidifiers, washing machine, dishwasher etc when it's sunny. All can be automated to an extent.
-Sell excess.
-Offset oil use to heat hot water. You will need a HW store, ideally a larger one 200l+ but that's way, way less expensive than battery storage. Well set up, should result in you boiler barely running outside of the heating season.
-You can use night storage heaters to dump excess generation into to help reduce space heating costs. However, it's barely worth mentioning as, unless you have a very large capacity system, it's unlikely there will be significant excess to use at times of year when you'd like most heating.

If possible, you should definitely move away from space heating with direct electric heaters though, unless it's a small space that is only warmed up for short/sporadic periods. The obvious is to connyt existing central heating network. But if that's not practical, might be worth considering an air to air heat pump. Or a Chinese diesel heater.

Why not install the system now as standard but put in a hybrid inverter (unless you already have a standard one) that way you can easily add batteries easily on future if you're generating loads more than you use. I did this a few years ago but, while getting ~12p per kWh to sell back to the grid, there hasn't yet been enough incentive to install batteries.

 

[jmp49]

Don't buy any wind turbine that doesn't provide an output chart of annual average windspeed Vs kWh production ideally produced or verified with real world data.

Spoiler alert, vertical axis wind turbines are generally pretty poor performers and these charts are, unsurprisingly, rarely provided

Thats really sound advice thanks, but at the budget I'm talking about, they're all going to be poor performance compared to their claims.
I was looking at these, 10Kw output claimed, but probably nearer 5KW peak in reality a bit like chinese diesel heater sizing, and people are already asking for a chart with no response from the seller.

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If it delivers 2.5Kw that'll be useful. I'll do some more research to see if any of the chinese units are better than others.

 

[Roger440]

There are lots of other things that can help to prioritise energy savings and storage before adding batteries;
-Defer electrical usage to periods of high solar generation e.g. pump up compressors, run dehumidifiers, washing machine, dishwasher etc when it's sunny. All can be automated to an extent.
-Sell excess.
-Offset oil use to heat hot water. You will need a HW store, ideally a larger one 200l+ but that's way, way less expensive than battery storage. Well set up, should result in you boiler barely running outside of the heating season.
-You can use night storage heaters to dump excess generation into to help reduce space heating costs. However, it's barely worth mentioning as, unless you have a very large capacity system, it's unlikely there will be significant excess to use at times of year when you'd like most heating.

If possible, you should definitely move away from space heating with direct electric heaters though, unless it's a small space that is only warmed up for short/sporadic periods. The obvious is to connyt existing central heating network. But if that's not practical, might be worth considering an air to air heat pump. Or a Chinese diesel heater.

Why not install the system now as standard but put in a hybrid inverter (unless you already have a standard one) that way you can easily add batteries easily on future if you're generating loads more than you use. I did this a few years ago but, while getting ~12p per kWh to sell back to the grid, there hasn't yet been enough incentive to install batteries.

The house and workshop are seperate buildings. The house isnt really much of an issue. Heating and hot water are oil. So electrical consumption is pretty low. Theres a washing machine, a cooker, and a shower. They are the only high load items. Theres only two of us.

The workshop, as i posted, 3 de-humidifiers runnning most of the winter 24/7. A heater in the office, average 3 days a week during the day. Then the compressor and other workshop stuff. My workshop activities are mainly when the weather is poor, so all winter primarily. For clarity, the workshop activities are hobbies, not work. But ive reduced my work hours, so my workshop time has increased considerably.

As you can see, the scope for deffering use to summer or nightime isnt really there. I did consider 6 de-humidifiers and run overnight only, on a time of use tarrif, but not convinced it would work in terms of keeping humidity stable. However, the biggest load, the compressor, is always going to be a day time activity. With a time of use tarrif, basic calcs say id be worse off, not better.

This is why my focus is on reducing the cost per kWh, rather than trying to use less or move it to the night.

But yes, i need to get the solar installed regardless, but to sell to the grid it needs to be MCS installed, which will mean the full system i have needs to go in the bin and be replaced with a new one supplid by them. (i hate MCS, how can a monopoly be allowed, indeed set up by the government)

My plan was to self install, but not sell to the grid. Maybe thats not bright from a financial view point? Not worked it out.

From the various responses, it does seem that batteries are probably part of the solution, but upfront costs are high, and payback uncertain. Although i think its fair to say, theres close to zero possibility of prices coming down while we have the current crowd, but they will likely be gone in 2029 so who knows after that. But that just suggests do it sooner rather than later.

I need to look at the EV idea a bit more i think.

I do also have a forklift, electric, which barely ever gets used, so ive thought about that, but intergrating it seems to be another unfathomable mystery with a million opinions, but not clear practical solutions.

Actually coming up with a "system", in detail, i think is my biggest stumbling block. I just cant my head around it. The principles are fine, its just coming up with what components and how to tie them together. Im also not keen on lots of complicated electronics. I understand simple domestic electrics. I dont understand electronics. These will only go wrong at some point, so need to be kept to a minimum. Jmp49, comments were extremely useful, but when it got to the monitoring side, that lost me completely. Absolutely no idea what most of that meant. Im sure its very clever, but unless i understand it, i wont install it. Whatever gets done, i need to be able to understand it and fix it when it fails. Getting anyone specialist & competent to come out here is borderline impossible. Ive been trying to get someone to come and quote for some roof repairs for over a year with no success!

 

[charlysays]

Before i bought this house, we looked at an off grid house.

All do-able as you suggest, but even DIYing a lot of it, its still cheaper to be on the grid. I spent a lot of time doing the maths on that. Real maths, not man-maths!

Its an expensive way to live. More so if you use a fair bit of power as i do with compressors and machinery etc.

It's a lot less beneficial than it used to be, the powers that be have possibly rigged it to make it potentially cheaper to be on grid.
I guess there is some benefit to the security that you're not at the total mercy of a few large corporations though in terms of energy cost and a centralised power grid.
Feed in tariffs seem a prime example. A mate of mine has had two hydro setups running for the last 20-30 years. He built them himself and bought really old turbines and refurbished them himself, does any maintenance work himself. He runs his house, an annexe and EV off the electricity and gets paid quite a considerable sum for the excess electricity (or did, not sure what happened to tariffs which were agreed a long time ago?).

 

[gaz1]

if you want to say 1.5k for the house yearly then the workshop is using the same amount

its not the currant crowd thats an issue its the energy system that is the issue whilst i do agree smaller solar installs should be able to fit and use more solar panels to resupply the network the energy system is geared for low small regeneration and high generation of industrial units

whilst i also do expect your bills to go up with the new tarrifs coming into force soon and that may include data collection payment as well

whilst i actually dont mind the new smart meter i will be damned if im going to pay for the data collection of it as thats just another charge wacked onto the bill

its the energy supplier thats the main issue here

 

[GRW]

The house and workshop are seperate buildings. The house isnt really much of an issue. Heating and hot water are oil. So electrical consumption is pretty low. Theres a washing machine, a cooker, and a shower. They are the only high load items. Theres only two of us.

The workshop, as i posted, 3 de-humidifiers runnning most of the winter 24/7. A heater in the office, average 3 days a week during the day. Then the compressor and other workshop stuff. My workshop activities are mainly when the weather is poor, so all winter primarily. For clarity, the workshop activities are hobbies, not work. But ive reduced my work hours, so my workshop time has increased considerably.

As you can see, the scope for deffering use to summer or nightime isnt really there. I did consider 6 de-humidifiers and run overnight only, on a time of use tarrif, but not convinced it would work in terms of keeping humidity stable. However, the biggest load, the compressor, is always going to be a day time activity. With a time of use tarrif, basic calcs say id be worse off, not better.

This is why my focus is on reducing the cost per kWh, rather than trying to use less or move it to the night.

But yes, i need to get the solar installed regardless, but to sell to the grid it needs to be MCS installed, which will mean the full system i have needs to go in the bin and be replaced with a new one supplid by them. (i hate MCS, how can a monopoly be allowed, indeed set up by the government)

My plan was to self install, but not sell to the grid. Maybe thats not bright from a financial view point? Not worked it out.

From the various responses, it does seem that batteries are probably part of the solution, but upfront costs are high, and payback uncertain. Although i think its fair to say, theres close to zero possibility of prices coming down while we have the current crowd, but they will likely be gone in 2029 so who knows after that. But that just suggests do it sooner rather than later.

I need to look at the EV idea a bit more i think.

I do also have a forklift, electric, which barely ever gets used, so ive thought about that, but intergrating it seems to be another unfathomable mystery with a million opinions, but not clear practical solutions.

Actually coming up with a "system", in detail, i think is my biggest stumbling block. I just cant my head around it. The principles are fine, its just coming up with what components and how to tie them together. Im also not keen on lots of complicated electronics. I understand simple domestic electrics. I dont understand electronics. These will only go wrong at some point, so need to be kept to a minimum. Jmp49, comments were extremely useful, but when it got to the monitoring side, that lost me completely. Absolutely no idea what most of that meant. Im sure its very clever, but unless i understand it, i wont install it. Whatever gets done, i need to be able to understand it and fix it when it fails. Getting anyone specialist & competent to come out here is borderline impossible. Ive been trying to get someone to come and quote for some roof repairs for over a year with no success!

You could use the forklift lead-acid cells as a pack for the workshop I'd think. Depending on cable size & rating you might be able to use the Anderson Connectors you'll have for the charger & plug in to the FLT and have a second set of cables with a connector to make it easy to connect/disconnect to your inverter unit. You could get a programmable inverter-charger as used for off-grid, which would let you select/set the peak load etc that you'll permit the pack to support (& for how long) as well as voltage thresholds to protect the pack.
Victron do good stuff I believe of this type nowadays (I was more used to Outback, Trace/Xantrex & SMA marques, but the kit moves on)

 

[Milkybars]

Lets just say the solar goes up and is not MCS (This will require the inverter to set to none export and wired as such)

And you have a battery somewhere (exterior wall near generation (i.e Panels)
The solar during the day (when generating can be set via inverter to feed the workshop) if there is no workshop draw of power then it will top the battery up.
So no solar generation and the battery is charged ..the system uses the battery (until there is none left) and you go back on to using the grid.

Now if your on certain tarrifs the electric is 'cheaper' at night..so you can charge the battery (if it needs it) and then use this during they day before reverting to grid

Given your usage ..id say it would pay for itself ..but its a fair outlay for a good battery and inverter (that are designed to work they way described above)
Most suppliers of the kit will know exactly what you need and be able to assist

 

[Gareth J]

Look into the requirements Octopus are currently saying they need to get non MCS installation allowed. They were advertising that they were going to/do accept but I don't know if it got off the ground or if it's realistically doable. But if you can get paid to export, it makes the investment to earn from every kWh you produce much easier.

3x dehumidifiers.... Really? Is your workshop a hanger? Maybe a few cans of expanding foam to seal some gaps could let you cut down on the dehumidifier habit...?

 

[gaz1]

to be fair this is rogers workshop

 

[colin247]

Get your units right first and that might help.

Energy is measured in Joules (becomes relevant later). One Watt (capital because it was named after someone) is defined as one Joule per second (again capital for the same reason). Kilowatt (kW) means 1000 Watts or 1000 Joules per second.

This only tells you the rate at which you are using energy not how much you have used. To know that you need a time frame. Hence kWh (kilo Watts per hour).

An example, it takes 330kJ of energy to boil one litre of water. Therefore if you had a 330kW kettle you could boil 1 litre in a second. Realistically you don't so a kettle is say 2kW. This would then take 330/2 or 165 seconds to boil the water, 2 minutes 45.

Now to work out how much electricity you've used in conventional units you need to convert them to the same units. We've used 2kW for 2m45 so that's 2x(2.75/60) = ~0.1kWh (note we have to divide runtime in minutes by 60 to get it to hours).

Battery capacity tends to be quoted in either kWh or Ah. So a 30kWh battery can supply 30kW for one hour or equivalent. So 15kW for 2 hours and so on. Note depending on the design of the battery it might not be able to deliver 30kW, it might be limited to a maximum output of say 2kW in which case you can max it out for 15h.

Using your example of a 30kWh battery over 24h then it would be capable of delivering a continuous 1.25kW for 24h. If you only had 100W load for part of the day then you can draw more at other periods.
If you think of it in terms of a graph with kW on the y axis and time on the x axis then the area under the graph can't exceed 30kWh.

If the battery capacity in Ah then you need to know the nominal voltage because Voltage x Current = Power (V x A = W) to get the capacity.

Bear in mind that an inverter won't be 100% efficient so you lose some power there.

When you get into the nitty gritty you need to start looking at graphs rather than "figures" as the capacity isn't linear with voltage etc., so to get a more accurate picture you have to start working it out for different profiles etc (adding areas under graphs or integrating).

Very interesting, thanks for posting.