Circular reasoning (Rolfe's solar energy system)

[Exdro]

@Rolfe Saw this video and remembered that you said you've got oil heating:

I had oil heating and experienced exactly what was stated in this video. No more large unsightly smelly oil tank. Space freed up in our small galley kitchen. When used properly, heat pumps compress very favourably with any other form of heating. While I don’t necessarily agree on compelling people to have them, they are worth considering, especially if you are not on the gas grid.
They are not noisy, the larger radiators do not take up any more wall space as they are only marginally thicker to allow for their double panel construction. Please have a survey done and make sure that your installers are accredited. Do not take out your existing boiler and replace it with a heat pump without addressing the infrastructure or you may be disappointed.

 

[johnb80]

I had oil heating and experienced exactly what was stated in this video. No more large unsightly smelly oil tank. Space freed up in our small galley kitchen.

Yep, all of that would be a real bonus.

When used properly, heat pumps compress very favourably with any other form of heating.

No it doesnt, not comparing with gas for example. Even factoring in boiler efficiency the heatpump doesnt quite make in the best of conditions:-
Gas average cost 4.43p/kWh, with an efficiency of say 90% using gas will average out at 4.92p per kWh of heat.
Electricity say an average of 20p/kWh and a COP of 3.5 would give an average energy cost of 5.71p per kWh of heat.
It's close but certainly not streets ahead. In cooler weather the COP gets significant worse and then gas wins easily.

While I don’t necessarily agree on compelling people to have them, they are worth considering, especially if you are not on the gas grid.

Absolutely 100%, no brainer comparing it to oil, wood pellets, solid fuel etc.

They are not noisy, the larger radiators do not take up any more wall space as they are only marginally thicker to allow for their double panel construction. Please have a survey done and make sure that your installers are accredited. Do not take out your existing boiler and replace it with a heat pump without addressing the infrastructure or you may be disappointed.

Several of our rads were already twin panel with the fins inside so larger rads wasnt really an option. What I did do was to run our gas boiler at low flow temperatures during a cold spell to see if it was sufficient to heat our home. I reduced it down to 33 deg C at a minimum and we were comfortably warm. Armed with that info I purchased a 14 kW Mitsubishi ECODAN and installed it myself, retaining the gas boiler too. Obviously no grant because I wanted to retain the boiler as a backup and for when it's really cold. I have programmed Home Assistant to monitor temperatures, performance and energy costs, it makes the decision to use Gas / Air to Water Heatpump or air to air heatpump based on time of day, energy costs and performance. Rarely do the figures force the air to water heatpump to be chosen, gas is the prime one and air to air in the evenings.

Air to water heatpump is not the real solution it's made out to be IF gas is available. Air to air is good and you can of course use it for cooling as well.

 

[Bam Bam]

Even factoring in boiler efficiency the heatpump doesnt quite make in the best of conditions:-
Gas average cost 4.43p kWh, with an efficiency of say 90% using gas will average out at 4.92p per kWh of heat.
Electricity say an average of 20p kWh and a COP of 3.5 would give an average energy cost of 5.71p per kWh of heat.
It's close but certainly not streets ahead. In cooler weather the COP gets significant worse and then gas wins easily.

You are right that gas is often cheaper unless you have a very efficient A2W heat pump set-up.

What if you add on a carbon price, though?

Domestic gas is severely undertaxed for its emissions in comparison to all other fuel sources.

Politicians don't want to touch that anomaly because it will result in tabloid headlines about elderly people dying of cold etc.

 

[johnb80]

You are right that gas is often cheaper unless you have a very efficient A2W heat pump set-up.

No A2W heatpumps get anywhere near COP 3.5 when the weather gets really cold outside (when you need the heat). I can see it on my system monitored live in Home Assistant that rarely is A2W chosen due to the price of Gas.

What if you add on a carbon price, though?

Of course if youre basing choice on pollution it's a no brainer, it beats all other forms of heating.

Domestic gas is severely undertaxed for its emissions in comparison to all other fuel sources.

I think it would be better to work at this from the other end, make electricity cheaper by zero VAT and/or no standing charge to make the heatpumps more competitive,

Politicians don't want to touch that anomaly because it will result in tabloid headlines about elderly people dying of cold etc.

Well potentially that would be reality not just tabloid sensation. The issue can be addressed though by other means as mentioned above.

 

[Exdro]

Yep, all of that would be a real bonus.


No it doesnt, not comparing with gas for example. Even factoring in boiler efficiency the heatpump doesnt quite make in the best of conditions:-
Gas average cost 4.43p/kWh, with an efficiency of say 90% using gas will average out at 4.92p per kWh of heat.
Electricity say an average of 20p/kWh and a COP of 3.5 would give an average energy cost of 5.71p per kWh of heat.
It's close but certainly not streets ahead. In cooler weather the COP gets significant worse and then gas wins easily.


Absolutely 100%, no brainer comparing it to oil, wood pellets, solid fuel etc.


Several of our rads were already twin panel with the fins inside so larger rads wasnt really an option. What I did do was to run our gas boiler at low flow temperatures during a cold spell to see if it was sufficient to heat our home. I reduced it down to 33 deg C at a minimum and we were comfortably warm. Armed with that info I purchased a 14 kW Mitsubishi ECODAN and installed it myself, retaining the gas boiler too. Obviously no grant because I wanted to retain the boiler as a backup and for when it's really cold. I have programmed Home Assistant to monitor temperatures, performance and energy costs, it makes the decision to use Gas / Air to Water Heatpump or air to air heatpump based on time of day, energy costs and performance. Rarely do the figures force the air to water heatpump to be chosen, gas is the prime one and air to air in the evenings.

Air to water heatpump is not the real solution it's made out to be IF gas is available. Air to air is good and you can of course use it for cooling as well.

There are no real solutions, only better options for your individual circumstances. In my case, with no mains gas and the need to replace my 40 yr old oil boiler, leaking oil tank and weeping hot water tank, it was a no brainer. This, combined with the RHI grant of £350.00 per quarter index linked for 7 yrs means that it will eventually pay for itself. I’ve subsequently fitted solar panels and a battery pack which pays for 70% of all electricity in summer (including EV charging). In winter, I charge the battery at the cheap overnight rate which keeps the ASHP at the cheap rate during the darkest hours. You are absolutely correct that they are not a universal panacea, but are worthy of consideration.

 

[johnb80]

There are no real solutions, only better options for your individual circumstances. In my case, with no mains gas and the need to replace my 40 yr old oil boiler, leaking oil tank and weeping hot water tank, it was a no brainer. This, combined with the RHI grant of £350.00 per quarter index linked for 7 yrs means that it will eventually pay for itself. I’ve subsequently fitted solar panels and a battery pack which pays for 70% of all electricity in summer (including EV charging). In winter, I charge the battery at the cheap overnight rate which keeps the ASHP at the cheap rate during the darkest hours. You are absolutely correct that they are not a universal panacea, but are worthy of consideration.

Absolutely agree with you on this, it was your earlier statement "When used properly, heat pumps compress (compares?) very favourably with any other form of heating" that I was taking slight issue with

 

[Bam Bam]

Well potentially that would be reality not just tabloid sensation. The issue can be addressed though by other means as mentioned above.

Absolutely, the issues should be dealt with otherwise! Subsidising heat pump purchases is the current method but given the cheapness of gas it is going to have minimal impact.

People on the gas grid are mostly installing them for moral reasons and not economic ones (unless they offset their carbon emissions, which is also simply a moral choice).

It might also be a sensible investment to the extent that gas will get more expensive as more people come off the grid and the more the North Sea fields get depleted (unless Russia has a change of heart in Ukraine which doesn't seem likely).

My point was that when tragedies happen the taxing of fossil fuels would get blamed, rather than the other policy failures.

 

[Exdro]

Absolutely agree with you on this, it was your earlier statement "When used properly, heat pumps compress (compares?) very favourably with any other form of heating" that I was taking slight issue with

Yes, compares not compress. However, using 20p per kWh is taking a higher cost than can be achieved using cheaper rate tariffs with solar and battery storage for the cheaper night rate. I am fortunate (or prescient) enough to have been able to invest in an EV, ASHP and solar panels, thus benefitting from a less expensive average rate than if on a fixed tariff.
It surely should not take too much foresight from whichever shade of Government is elected after 4th July to mandate that all new buildings or large extensions should have solar panels or even better, tiles, built in battery storage and possibly even a small wind turbine to provide some background power. These methods coupled with harvesting of “grey” water for flushing or gardening with a built in heat pump to reclaim heat from washing machines etc could solve the energy crisis in less than 20 years. However, no government seems to be able to plan for anything that will be longer than a 5 year electoral span or commit to spending to future proof the country.
Haven’t even mentioned pot holes?

 

[Bam Bam]

Yes, compares not compress. However, using 20p per kWh is taking a higher cost than can be achieved using cheaper rate tariffs with solar and battery storage for the cheaper night rate. I am fortunate (or prescient) enough to have been able to invest in an EV, ASHP and solar panels, thus benefitting from a less expensive average rate than if on a fixed tariff.
It surely should not take too much foresight from whichever shade of Government is elected after 4th July to mandate that all new buildings or large extensions should have solar panels or even better, tiles, built in battery storage and possibly even a small wind turbine to provide some background power. These methods coupled with harvesting of “grey” water for flushing or gardening with a built in heat pump to reclaim heat from washing machines etc could solve the energy crisis in less than 20 years. However, no government seems to be able to plan for anything that will be longer than a 5 year electoral span or commit to spending to future proof the country.
Haven’t even mentioned pot holes?

See also district heating.

Notably absent from the UK because it would require joined up thinking and planning, rather than letting developers do whatever suits them best.

 

[johnb80]

Yes, compares not compress. However, using 20p per kWh is taking a higher cost than can be achieved using cheaper rate tariffs with solar and battery storage for the cheaper night rate.

Agreed, conversely I also used a COP of 3.5 which is relatively high for winter time when you need the heat.

I am fortunate (or prescient) enough to have been able to invest in an EV, ASHP and solar panels, thus benefitting from a less expensive average rate than if on a fixed tariff.

Yep me too, 7kW Solar PV, 9kW Inverter power and 32 kWh of storage. My average energy price is 7.73p/kWh. I also export all of my solar and battery storage during the evening, recharging them on Intelligent GO at night.

It surely should not take too much foresight from whichever shade of Government is elected after 4th July to mandate that all new buildings or large extensions should have solar panels or even better, tiles, built in battery storage and possibly even a small wind turbine to provide some background power.

Tiles is not such a good idea, more connections = greater risk of failure. Wind turbines, small ones are very noisy and therefore not suitable. I have in my past used about 4 different styles of 5 kW turbines and all of them were unacceptably loud.

These methods coupled with harvesting of “grey” water for flushing or gardening with a built in heat pump to reclaim heat from washing machines etc could solve the energy crisis in less than 20 years.

Certainly ground source heatpump is way better than air source and it could be made to incorporate heat from waste water.

However, no government seems to be able to plan for anything that will be longer than a 5 year electoral span or commit to spending to future proof the country.

Aye, tricky situation

Haven’t even mentioned pot holes?

Yep we have a good crop of them, handy water storage LOL

 

[Exdro]

Forgot to mention V2H or V2G using EV batteries to support Home or Grid during peak periods when vehicle not in use and recharging when electricity is almost free.
No foresight.

 

[johnb80]

Forgot to mention V2H or V2G using EV batteries to support Home or Grid during peak periods when vehicle not in use and recharging when electricity is almost free.
No foresight.

Are you actually doing V2L ? It's not an easy path for an MG as far as I know.

 

[Exdro]

Are you actually doing V2L ? It's not an easy path for an MG as far as I know.

Yes. Works well.

Yes. Works well on MGZSEV LR TROPHY CONNECT and MG5.

 

[johnb80]

Yes. Works well on MGZSEV LR TROPHY CONNECT and MG5.

Supplying just a load though rather than the house?

My work around is to run a battery charger in my home built battery from the V2L, that in turn feeds the inverters and the house.

 

[Exdro]

As you say. MG does not support V2H. Not sure that I would risk trying your method but if it works for you and you feel it is safe then go for it. Only hope that MG and all other manufacturers and electricity suppliers make this and V2G in the next models produced.

 

[johnb80]

As you say. MG does not support V2H. Not sure that I would risk trying your method but if it works for you and you feel it is safe then go for it.

My way is perfectly safe from all aspects. I have a 3kW LifeP04 battery charger that simply sits on the + and - terminals of my 48v (16 cells) battery. If I run the system from the car or the generator it unit supplies 3 kW into the battery, the inverters taking power from the same battery. It's no different to charging up via solar PV or by mains overnight. The added bonus from the car perspective is it runs at a constant 3 kW, it's easy to predict duration etc of the car battery.

Only hope that MG and all other manufacturers and electricity suppliers make this and V2G in the next models produced.

Unlikely IMHO, the need to synchronise to the grid supply needs quite a bit of inverter work.

 

[Exdro]

Sounds great but unfortunately beyond my skills or knowledge base.

 

[Rolfe]

@Rolfe Saw this video and remembered that you said you've got oil heating:

Thanks, that's interesting. If my old oil system was still struggling on I might be thinking about doing something, but since I renewed the boiler in 2019 and then the tank in January last year, ripping out that virtually new install to put in something else isn't filling me with enthusiasm. My house is also a lot bigger than that one!

 

[Rolfe]

Dragging this back on topic, I have another query. How do I stop Octopus trying to charge my car overnight?

Octopus app, under "devices". The app seems to assume that you always want a smart charge if the car is plugged in. It is impossible to set the smart charge amount to zero - the lowest available is 10%. That would be about 5 kWh for my car, but for some reason Octopus thinks it means something over 8 kWh. In self-defence I set it to the minimum, as damage limitation should this actually happen, and just as well.

Monday evening I got back with the car on about 20%, jetlagged to hell and gone. My intention was to let it pick up whatever solar was available the next day, so I plugged in, checked the Zappi was on eco+, and went to bed. What then happened was that Octopus decided I wanted that 10%, which it thinks is over 8 kWh, and set a schedule to deliver it. I didn't want it to do that, but it did it anyway, and I can see no way to stop it doing it again.

Tuesday and Wednesday I unplugged the car in the late afternoon, then plugged in again in the morning. This is a pain. Now this is Thursday and I forgot. Looking at the app, I see the damn thing now has another schedule set to charge for a couple of half-hour periods overnight. I can see no way to tell it not to do this. I'm going to have to go out there and unplug again.

People say, just leave the car plugged in on eco+ and it will graze on the excess solar. Sure. That seems to be more or less what it's doing IF I plug it in some time in the morning. But if I leave it plugged in to repeat the exercise again tomorrow without me having to intervene, Octopus is going to shove 8 kWh in there whether I like it or not.

This can't be right. What am I missing?

 

[Bam Bam]

Dragging this back on topic, I have another query. How do I stop Octopus trying to charge my car overnight?

This can't be right. What am I missing?

Sorry I don't have experience with IOG or Zappi so can't say for sure.

I have been very frustrated with Givenergy today though because it kept on restarting car charging during the peak period. I should have been exporting that solar!

So just to say I share your frustration with chargers deciding to do things you don't want!