Storage Heaters as PV battery dump

[Esalglop1945]

I have bought a bungalow with 4 large DIMPLEX XL brown Storage Heaters. I have aquote from local firm to install 60 panels on roof. I also have a woodburner and woodland to supplement if required in winter. Is it really economic to physically dump the old XL storage heaters and replace with Quantum.?

 

[Geoff1946]

I'm not sure what you are suggesting. Are you thinking of directing your solar generated power into the boost circuit of the Quantum heater?

 

[ProDave]

The old style, nice and simple storage heaters could be used as a dump for excess PV, not sure if the Quantum with it's complicated controls would do that.

BUT you do realise the vast majority of your surplus will be in summer when you don't need heat in the house, and in winter when you need heat in the house, the PV output will be low and little if any surplus.

Dumping excess to DHW makes more sense, you always need hot water all year.

60 panels is a big array. do you have permission from the DNO? it will be near impossible to use all they generate in the summer and the smart export payment is a pittance so are you sure it is really worth having that much?

 

[binky]

You can buy gadgets designed to dump surplus electric into an immersion heater. These would probably work with the old style storage heaters, but trash modern digital controls. I'm not sure what the power limit is for one of these but I think it's around 3 kw, so you would need multiple units.

 

[Esalglop1945]

Thanks for replies. I am 76 and planning a passivhaus standard conversion. Change my car, used mainly in summer, to electric. Great to learn that old Night Stores are worth retaining. The bungalow has large SW unobstructed roof. I had not thought of DNO imposing a restriction? Would I be able to have 2x30 panels with only 1x30 connected to grid?

 

[ProDave]

The basic rule is you can fit a 4kWp pv system with an inverter limited to 3.68kW output and notify it under G98 after install and the DNO have to accept it. Anything larger, and you have to notify it to the DNO under G99 prior to install, the DNO may make a charge just to evaluate the application and then may make a charge to perform network upgrades to allow a larger system to be connected. There is likely a cost and time penalty to fit anything larger than 4Kwp.

Unless you look at an off grid system, not something I am familiar with, But perhaps an inverter / battery system dedicated to car charging would work without a grid connection?

P,S if you are building a passive house, you might want to take a look at the BuildHub forum.

 

[BorisJ]

Using solar PV to heat water is madness. There is so much loss in converting sunlight to electricity. Much better to heat water directly using solar hot water panels.

 

[ProDave]

Using solar PV to heat water is madness. There is so much loss in converting sunlight to electricity. Much better to heat water directly using solar hot water panels.

That is a debatable subject.

Solar thermal is a one trick pony, Once our water tank is up to temperature any more heat it could produce is wasted. On the other hand in winter it may never heat the water at all.

Solar PV will power anything in use in your house at the time and most people only send excess power to water heating rather than exporting it to the grid. Even in winter, if there is some generation and nothing else is using it, it will heat your water a little bit.

 

[binky]

solar thermal is very effective, but then you have more maintenance costs. Of the various customers I've fitted only 4kW systems for, and an immersion controller, they all report that they get almost all their hot water from the panels for about 3/4 of the year.

 

[binky]

I had not thought of DNO imposing a restriction? Would I be able to have 2x30 panels with only 1x30 connected to grid?

They will not approve backfeeding their grid with more than 16A unless agreed with an application made prior to installation. What you will need is an inverter designed to limit the export to whatever they agree - this doesn't stop energy being pumped into the house, what happens if you aren't using the energy is that it cuts output from the system. With panels at 300W and more these days, 30 panels is going to give you 9kWp. You will struggle to find a single phase inverter that does more than 6kW, although you can attach 9kW of panels to that. It maybe worth getting a 3 phase supply from the DNO, which means you can have 3x16A or 12kW to which you can attach around 15kW of panels.

One other point, passivhaus standards probably mean you need very little heating - a friend of mine built his house to those standards, he has single 1kW electric heater to cover the worst of winter and hardly ever uses it.

You can get solar canopies for car charging and inverters designed to do that from your regular solar system. If you have the space and suitable location, it may also be worth looking at a smallish wind turbine. As much as I like the simplicity of solar PV, it doesn't do much in winter, and the recent warm but heavily overcast weather, which I suspect might become the 'norm' due to climate change, is really knocking winter output down.

 

[Murdoch]

Using solar PV to heat water is madness. There is so much loss in converting sunlight to electricity. Much better to heat water directly using solar hot water panels.

not sure I agree with this statement.

if you have PV and you have an immersion tank, then the small cost of the diverted to give you free hot water makes perfect sense.

I have this at home and rarely use the boiler to heat water in the summer

 

[roys]

Using solar PV to heat water is madness. There is so much loss in converting sunlight to electricity. Much better to heat water directly using solar hot water panels.

Don’t agree with this either, having ran / run both systems the solar pv is definitely the way to go. For sure solar thermal panels are more efficient but there is a lot more maintenance issues with them. I only have one out of my two solar thermal panels working now and the next time I get pump or panel issues with it I will be binning the solar thermal system totally and fit a four panel solar pv stand alone system as a water heater.

 

[Esalglop1945]

The old style, nice and simple storage heaters could be used as a dump for excess PV, not sure if the Quantum with it's complicated controls would do that.

BUT you do realise the vast majority of your surplus will be in summer when you don't need heat in the house, and in winter when you need heat in the house, the PV output will be low and little if any surplus.

Dumping excess to DHW makes more sense, you always need hot water all year.

60 panels is a big array. do you have permission from the DNO? it will be near impossible to use all they generate in the summer and the smart export payment is a pittance so are you sure it is really worth having that much?

The old style, nice and simple storage heaters could be used as a dump for excess PV, not sure if the Quantum with it's complicated controls would do that.

BUT you do realise the vast majority of your surplus will be in summer when you don't need heat in the house, and in winter when you need heat in the house, the PV output will be low and little if any surplus.

Dumping excess to DHW makes more sense, you always need hot water all year.

60 panels is a big array. do you have permission from the DNO? it will be near impossible to use all they generate in the summer and the smart export payment is a pittance so are you sure it is really worth having that much?

 

[Esalglop1945]

The old style, nice and simple storage heaters could be used as a dump for excess PV, not sure if the Quantum with it's complicated controls would do that.

BUT you do realise the vast majority of your surplus will be in summer when you don't need heat in the house, and in winter when you need heat in the house, the PV output will be low and little if any surplus.

Dumping excess to DHW makes more sense, you always need hot water all year.

60 panels is a big array. do you have permission from the DNO? it will be near impossible to use all they generate in the summer and the smart export payment is a pittance so are you sure it is really worth having that much?

I will def go with DHW

 

[Esalglop1945]

You can buy gadgets designed to dump surplus electric into an immersion heater. These would probably work with the old style storage heaters, but trash modern digital controls. I'm not sure what the power limit is for one of these but I think it's around 3 kw, so you would need multiple units.

Thanks for that. I won’t be dumping the Old NSs if there is enough KW to heat them.

 

[Esalglop1945]

The basic rule is you can fit a 4kWp pv system with an inverter limited to 3.68kW output and notify it under G98 after install and the DNO have to accept it. Anything larger, and you have to notify it to the DNO under G99 prior to install, the DNO may make a charge just to evaluate the application and then may make a charge to perform network upgrades to allow a larger system to be connected. There is likely a cost and time penalty to fit anything larger than 4Kwp.

Unless you look at an off grid system, not something I am familiar with, But perhaps an inverter / battery system dedicated to car charging would work without a grid connection?

P,S if you are building a passive house, you might want to take a look at the BuildHub forum.

Thanks for your your contribution. I will go for separate Car Charger.

 

[Andy™]

Using solar PV to heat water is madness. There is so much loss in converting sunlight to electricity. Much better to heat water directly using solar hot water panels.

if youre using solar primarily to heat the water then possibly. if youre using it simply to heat the water to use up spare capacity then not really an issue

 

[Esalglop1945]

I had not thought of DNO imposing a restriction? Would I be able to have 2x30 panels with only 1x30 connected to grid?

They will not approve backfeeding their grid with more than 16A unless agreed with an application made prior to installation. What you will need is an inverter designed to limit the export to whatever they agree - this doesn't stop energy being pumped into the house, what happens if you aren't using the energy is that it cuts output from the system. With panels at 300W and more these days, 30 panels is going to give you 9kWp. You will struggle to find a single phase inverter that does more than 6kW, although you can attach 9kW of panels to that. It maybe worth getting a 3 phase supply from the DNO, which means you can have 3x16A or 12kW to which you can attach around 15kW of panels.

One other point, passivhaus standards probably mean you need very little heating - a friend of mine built his house to those standards, he has single 1kW electric heater to cover the worst of winter and hardly ever uses it.

You can get solar canopies for car charging and inverters designed to do that from your regular solar system. If you have the space and suitable location, it may also be worth looking at a smallish wind turbine. As much as I like the simplicity of solar PV, it doesn't do much in winter, and the recent warm but heavily overcast weather, which I suspect might become the 'norm' due to climate change, is really knocking winter output down.

Thank you so much. Your advice is brilliant.

 

[NozSpark]

Thanks for your your contribution. I will go for separate Car Charger.

If you’re having PV then it would be well worth getting a MyEnergi Zappi 2 charge point (with hub) and a MyEnergi Eddi to control the feed to immersion

 

[Esalglop1945]

I had not thought of DNO imposing a restriction? Would I be able to have 2x30 panels with only 1x30 connected to grid?

They will not approve backfeeding their grid with more than 16A unless agreed with an application made prior to installation. What you will need is an inverter designed to limit the export to whatever they agree - this doesn't stop energy being pumped into the house, what happens if you aren't using the energy is that it cuts output from the system. With panels at 300W and more these days, 30 panels is going to give you 9kWp. You will struggle to find a single phase inverter that does more than 6kW, although you can attach 9kW of panels to that. It maybe worth getting a 3 phase supply from the DNO, which means you can have 3x16A or 12kW to which you can attach around 15kW of panels.

One other point, passivhaus standards probably mean you need very little heating - a friend of mine built his house to those standards, he has single 1kW electric heater to cover the worst of winter and hardly ever uses it.

You can get solar canopies for car charging and inverters designed to do that from your regular solar system. If you have the space and suitable location, it may also be worth looking at a smallish wind turbine. As much as I like the simplicity of solar PV, it doesn't do much in winter, and the recent warm but heavily overcast weather, which I suspect might become the 'norm' due to climate change, is really knocking winter output down.

Thank you