"Looking for a PV and EV solution"

Coastalwatch

Coastalwatch wrote: »

A heartfelt thanks to you all for the advice so freely given(and mostly adherred too) without which I doubt we should have got this far.
Just home storage, V2H and ASHP to sort.
Patience, patience I hear you say.:beer::A

Nearly six months on and both PV and EV are performing as expected. Perhaps last summer guaranteeing that the PV array could hardly do anything less!
Since installation in late April it's generated nearly 8 MWh's of energy.
Interrogation of Zappi, our EV charger, showed it transferred 655.5 kWh's into our EV, of which 540 were solely from the PV array.

Towards the end of the year we've had two Air Source Heat Pumps installed which now supply the majority of our space heating requirements. During December they consumed 187 kWhs while consumption of gas reduced some 700 kWh's compared to the previous year. Admittedly daily temperatures have been a few degrees milder this year so not sure what can be concluded apart from an unknown reduced CO2 output.
Water heating is still supplied by the gas combi but we're planning to install a direct hot water tank to make better use of the summers excess PV. Consumption of gas for this purpose has been around 100 kWh's/month to date.
We shall still need gas to heat the areas not reached by the ASHP's, that is the kitchen and an ensuite, plus a gas hob. The latter being easily replaced should that ever become the sole requirement for gas.
I don't think we'll ever be able to store sufficient summer output for use in the winter although an 8 kWh battery would certainly assist with general overnight demand. I really can't see a 3MWh battery fitting in the garage let alone being affordable.

I understand that in some parts of the USA, excess PV is purchased by the grid and then supplied back at cost, plus a small handling charge.

I wonder if the new Smart Export Guarantee, announced today, might stretch to incorporate such a scheme here? Once the hiatus period is over that is!

rugbyleaguesmate

Can I resurrect this thread please? I have 6.72Kw South Facing PV and I want an Ev to stick my excess generation in and then drag it back into my house if I need it. Are we any closer to this being reality yet? I haven' checked for a year or so.....

mgbond

Coastalwatch wrote: »

Nearly six months on and both PV and EV are performing as expected. Perhaps last summer guaranteeing that the PV array could hardly do anything less!
Since installation in late April it's generated nearly 8 MWh's of energy.
Interrogation of Zappi, our EV charger, showed it transferred 655.5 kWh's into our EV, of which 540 were solely from the PV array.

Towards the end of the year we've had two Air Source Heat Pumps installed which now supply the majority of our space heating requirements. During December they consumed 187 kWhs while consumption of gas reduced some 700 kWh's compared to the previous year. Admittedly daily temperatures have been a few degrees milder this year so not sure what can be concluded apart from an unknown reduced CO2 output.
Water heating is still supplied by the gas combi but we're planning to install a direct hot water tank to make better use of the summers excess PV. Consumption of gas for this purpose has been around 100 kWh's/month to date.
We shall still need gas to heat the areas not reached by the ASHP's, that is the kitchen and an ensuite, plus a gas hob. The latter being easily replaced should that ever become the sole requirement for gas.
I don't think we'll ever be able to store sufficient summer output for use in the winter although an 8 kWh battery would certainly assist with general overnight demand. I really can't see a 3MWh battery fitting in the garage let alone being affordable.

I understand that in some parts of the USA, excess PV is purchased by the grid and then supplied back at cost, plus a small handling charge.

I wonder if the new Smart Export Guarantee, announced today, might stretch to incorporate such a scheme here? Once the hiatus period is over that is!

When you say ASHP is this Air to Air or Air to Water. I'm interested in the Air to Air solution so was trying to work out what Battery size I should eventually get that will cover peak winter usage and the ASHP's

pile-o-stone

Coastalwatch wrote: »

Towards the end of the year we've had two Air Source Heat Pumps installed which now supply the majority of our space heating requirements. During December they consumed 187 kWhs while consumption of gas reduced some 700 kWh's compared to the previous year. Admittedly daily temperatures have been a few degrees milder this year so not sure what can be concluded apart from an unknown reduced CO2 output.
Water heating is still supplied by the gas combi but we're planning to install a direct hot water tank to make better use of the summers excess PV. Consumption of gas for this purpose has been around 100 kWh's/month to date.
We shall still need gas to heat the areas not reached by the ASHP's, that is the kitchen and an ensuite, plus a gas hob. The latter being easily replaced should that ever become the sole requirement for gas.
I don't think we'll ever be able to store sufficient summer output for use in the winter although an 8 kWh battery would certainly assist with general overnight demand. I really can't see a 3MWh battery fitting in the garage let alone being affordable.

Hi Coastal Watch, I missed this post when you first posted it on your thread. I'm struggling with the logic of fitting heat pumps when you already have a mains gas supply to your property? I was looking at going fully electric in my home (we also have mains gas) and everything I read said that heat pumps were more expensive to install and run than a gas condensing boiler, even when you include economy 7 type tariffs and subtract the standing charge for the removed gas supply.

I even tried factoring in the contribution from our solar PV, but as the highest heat demand is in winter, there would be very few occasions when there is an excess of generation when you want to run your heating. The sums wouldn't add up, so I gave up and stuck with our gas boiler (albeit with a thermal store to make it more efficient by running it in condensing mode for longer).

With your set up you still have a gas boiler, so you don't benefit from the loss of the standing charge, plus your EV will soak up most of your Spring/Autumn PV excess with the glut of summer PV not being used by your heat pumps and winter generation probably being too low to run the pumps. Batteries, as many of us have found to our annoyance, are still more expensive than just using mains electricity, so this would further increase rather than reduce your costs.

I'm therefore at a loss as to your heating strategy as you seem to have chosen the most expensive option possible? What am I missing?

All I can think is that your property is split over three separate building (hence the three heating sources), though you could still use heavily insulated underground district heating pipes between the buildings to move hot water from a centralised gas boiler to heat all of the buildings.

Coastalwatch

rugbyleaguesmate wrote: »

Can I resurrect this thread please? I have 6.72Kw South Facing PV and I want an Ev to stick my excess generation in and then drag it back into my house if I need it. Are we any closer to this being reality yet? I haven' checked for a year or so.....

Hi, as far as I'm aware then other than the OVO trial taking place there has been little change with either progress or the limited options available to us. Leaving it too expensive for me to consider although I'd be delighted to learn if anyone knows differently. I'd love a battery and be able to back it up with the EV as well, but until then I guess we just have to be patient until a suitable solution arrives in the market place.
I console myself with the knowledge that the whole renewable scene is gaining momentum in many directions with the focus of many businesses now embracing it rather than resisting it at all costs as has perhaps been the case in the past. With the whole car industry now throwing the kitchen sink towards new EV models then maybe pressure for such a system as would suit our needs will arrive eventually as a result.

Coastalwatch

mgbond wrote: »

When you say ASHP is this Air to Air or Air to Water. I'm interested in the Air to Air solution so was trying to work out what Battery size I should eventually get that will cover peak winter usage and the ASHP's

Hi mg, the first question is easy to answer in that our units are Air to Air.

Your second question not so, but hopefully the figures below from the previous three winter months may assist. From the thread

https://forums.moneysavingexpert.com/discussion/comment/75614082#Comment_75614082

Our two 2 kW units consumed on average 530 W/h with the highest days consumption being 12kWh's. That was a one off while there were two other days around 10kWh's. The average being 5.75 kWh's/day. This ignoring the 14 days run at low temps while on holiday.
Of course your system will be different in that it is probably supplying more heat than ours and with a different COP ratio too but hopefully the figures supplied will at least give you an indication.

Coastalwatch

pile-o-stone wrote: »

Hi Coastal Watch, I missed this post when you first posted it on your thread. I'm struggling with the logic of fitting heat pumps when you already have a mains gas supply to your property? I was looking at going fully electric in my home (we also have mains gas) and everything I read said that heat pumps were more expensive to install and run than a gas condensing boiler, even when you include economy 7 type tariffs and subtract the standing charge for the removed gas supply.

I even tried factoring in the contribution from our solar PV, but as the highest heat demand is in winter, there would be very few occasions when there is an excess of generation when you want to run your heating. The sums wouldn't add up, so I gave up and stuck with our gas boiler (albeit with a thermal store to make it more efficient by running it in condensing mode for longer).

With your set up you still have a gas boiler, so you don't benefit from the loss of the standing charge, plus your EV will soak up most of your Spring/Autumn PV excess with the glut of summer PV not being used by your heat pumps and winter generation probably being too low to run the pumps. Batteries, as many of us have found to our annoyance, are still more expensive than just using mains electricity, so this would further increase rather than reduce your costs.

I'm therefore at a loss as to your heating strategy as you seem to have chosen the most expensive option possible? What am I missing?

All I can think is that your property is split over three separate building (hence the three heating sources), though you could still use heavily insulated underground district heating pipes between the buildings to move hot water from a centralised gas boiler to heat all of the buildings.

Hi pile-o-stone, not sure quite where to begin but we are in a two bed bungalow only. The two ASHP's are Air to Air units fitted in separate rooms, one in the lounge the other in the lobby supplying heat to bathroom and bedrooms as required by opening or closing doors accordingly.
The COP ratio of the units being approx 4:1, a similar ratio to that of cost between gas and electric thus approx levelling out the two forms of energy in cost terms.

It could be argued that losses in the gas system give the heat pumps the edge. In addition the gas system consumes circa 250W of electricity to run the circulating pump and extractor fan in the vent the costs of which I'd ignored until pointed out to me.

I have to confess the strategy may not stack up entirely purely based on cost, but given that we all need to reduce our FF emissions then it is the latter which has driven the route taken with a limited budget all the same.
I'm rather envious of your heat stores as I'd like to install a system to heat our water from solar as well, but looking at costs I would struggle to justify installing something similar. From initial searching each unit is around £1500 plus installation? That was about the cost of each heat pump in our case.
I had thought to go for a direct unvented system until I discovered it required an annual service and a drain to the outside.

Any advice on these or alternate heating systems welcomed.:)

EricMears

rugbyleaguesmate wrote: »

Can I resurrect this thread please? I have 6.72Kw South Facing PV and I want an Ev to stick my excess generation in and then drag it back into my house if I need it. Are we any closer to this being reality yet? I haven' checked for a year or so.....

Apart from the fact that the equipment is still a bit hard to get hold of, there's a basic flaw in the project as described. You'd only have enough 'spare' power to charge the EV for a couple of hours either side of Noon and you'd need to start discharging it for most of the evening. That doesn't leave a lot of time available for driving around in the EV which is certainly what most people choose them for.

I have an EV and solar panels but there have been very few occasions over the last four years when the car has been standing idle at exactly the right time for charging it. On the whole, I prefer to budget for buying (E7) power to charge the car and use the excess PV for other uses.

1961Nick

Coastalwatch wrote: »

Hi pile-o-stone, not sure quite where to begin but we are in a two bed bungalow only. The two ASHP's are Air to Air units fitted in separate rooms, one in the lounge the other in the lobby supplying heat to bathroom and bedrooms as required by opening or closing doors accordingly.
The COP ratio of the units being approx 4:1, a similar ratio to that of cost between gas and electric thus approx levelling out the two forms of energy in cost terms.

It could be argued that losses in the gas system give the heat pumps the edge. In addition the gas system consumes circa 250W of electricity to run the circulating pump and extractor fan in the vent the costs of which I'd ignored until pointed out to me.

I have to confess the strategy may not stack up entirely purely based on cost, but given that we all need to reduce our FF emissions then it is the latter which has driven the route taken with a limited budget all the same.
I'm rather envious of your heat stores as I'd like to install a system to heat our water from solar as well, but looking at costs I would struggle to justify installing something similar. From initial searching each unit is around £1500 plus installation? That was about the cost of each heat pump in our case.
I had thought to go for a direct unvented system until I discovered it required an annual service and a drain to the outside.

Any advice on these or alternate heating systems welcomed.:)

The ASHP split system is the most cost effective route & if you can mount the indoor unit on an exterior wall, it's a tidy job. Cooling should cost you nothing & most of the heating will be from surplus solar output. Even if you use it at night, the cost will be comparable to gas.

At some point storage batteries will become viable & you will be able to use your solar surplus well into the evening.

Coastalwatch

1961Nick wrote: »

The ASHP split system is the most cost effective route & if you can mount the indoor unit on an exterior wall, it's a tidy job. Cooling should cost you nothing & most of the heating will be from surplus solar output. Even if you use it at night, the cost will be comparable to gas.

At some point storage batteries will become viable & you will be able to use your solar surplus well into the evening.

Hi Nick and thanks for your thoughts on ASHP already installed.
It is a hot water system I need to install next and I'm struggling to decide which might be the most appropriate option. From my limited understanding this appears to be between three. An indirect immersion tank requiring a pumped hot and cold supply to the shower in order to supply equal pressure to each. A direct unvented immersion tank requiring an expansion tank, drain to outside plus annual service and the third, a heat store.The latter appearing to be a costly alternative commencing around £1500 plus installation, unless I can be advised otherwise! Not that I've any knowledge of how one might perform or whether it might adequately fill a bath with some to spare!
Any thoughts on the above will be most appreciated.