Dual Fuel Boilers (Electric + NG) to solve heating and curtailment

GreatApe

markin wrote: »

I don't think more than 20% would be able to use the elec at once if 12kw, I don't think 3kw would instantaneously heat water to run a tap unless its a separate water heating supply and that may as well be under the sink.

Now Co-firing 50% of the time at 3kw would save some gas but is it worth it?

3KW would be fine to run the radiators and most gas heating is for the rads not for hot water
A typical house might be ~70% heating ~30% hot water

If the boiler has only 3KW electric and a shower is on it can be 8KW gas 3KW electric and yes its worthwhile it saves 3KW of gas (more like 4KW gas saved as gas is not 100% efficient) than to curtail the excess wind.

I don't think more than 20% would be able to use the elec at once if 12kw

I would agree but your assumption is wrong, way too high

Even if you assume ALL electric shower users have a shower in the morning between 6-9am and an average shower lasts 6 mins that means only 3.33% of the showers are on at the same time. And of course not EVERYONE has a shower in the morning at those times plenty of people have showers before or after then so the real figure is probably less than 2% of showers are on at the very peak usage times

This should be obvious by the fact millions of electric showers already exist and there is no stress on the grid and electric showers are legal to sell and buy suggesting there is no real problem in integrating a lot more

GreatApe

markin wrote: »

I don't think more than 20% would be able to use the elec at once if 12kw, I don't think 3kw would instantaneously heat water to run a tap unless its a separate water heating supply and that may as well be under the sink.

Now Co-firing 50% of the time at 3kw would save some gas but is it worth it?

To Add, 3KW hybrid boiler can switch a significant portion of heating to electric if surplus electric was available

Combi hybrid boiler circa ~80% (all of heating, some of hot water)
System or regular hybrid boiler circa ~100% since they have tanks (all of heating virtually all of hot water)

It is this to use the excess wind, a cost of £20
Or ideas costing hundreds of billions and taking years/decades to build hydrogen chemical industry to use the excess wind

Reed_Richards

GreatApe wrote: »

You need a simple cheap plug and play system.

Only if fuel costs don't change with time. That's never really been the case with electricity.

GreatApe wrote: »

IF someone has a combi as many homes and businesses do then you dont want to make it so they have to get rid of that and buy a huge tank find somewhere for it pay for additional plumbing etc

I have a combi and it's dreadful, mainly because it is a retrofit into a house that used to have a tank and the retrofit made long pipe runs even longer.

GreatApe wrote: »

Adds cost and complexity and many people dont really have the space for a large tank. A tank also loses energy for standing losses my tank close to 2KWh a day in lost heat just sitting there. And water tanks dont really offer a huge scope to store a lot of energy. A 200 litre tank allowed to cycle from 50-70 is only 4-5 KWh of storage

Many older houses were built around the need for a storage tank. Hopefully if well-insulated they won't lose as much as 2 kWh per day. 4-5 kWh of storage is good in battery terms and you can charge up the tank during peak hours of solar PV output when electricity ought to be very cheap.

GreatApe wrote: »

Instead you can have the smart boiler allow thermal storage via the house itself. So if the temp is set to 20 centigrade allow it to cycle between 19-22 this three degree of heat might have storage in excess of what the tank does and would cost nothing

My central heating is set to run at 18.5 C from 7:30 until 9;00, 19 C from 9;00 until 17:00, then 20 C from 17:00 until 22:30. In the evening when you are more sedentary then even 19.5 C feels cold. If you really think that you can have the house temperature vary by 3 degrees without feeling freezing at some times and boiling at others then you can't have tried it yourself

GreatApe

Reed_Richards wrote: »

My central heating is set to run at 18.5 C from 7:30 until 9;00, 19 C from 9;00 until 17:00, then 20 C from 17:00 until 22:30. In the evening when you are more sedentary then even 19.5 C feels cold. If you really think that you can have the house temperature vary by 3 degrees without feeling freezing at some times and boiling at others then you can't have tried it yourself

I take that back

There is really no need to do storage for some time and with these hybrid boilers probably no need for 20+ years. Somewhere around 2025 we may get towards excess wind power during some of the day. During that time you divert power into these hybrid boilers.

You send the electricity to the hybrid boilers and 1 unit of electricity will save ~1.25 units of natural gas

The countries boilers use some ~500TWh of NG each year

That is a massive pool of fossil fuels that can be chipped away at with hybrid boilers when there is excess wind power

markin

GreatApe wrote: »

..... ... ...

I would agree but your assumption is wrong, way too high

Even if you assume ALL electric shower users have a shower in the morning between 6-9am and an average shower lasts 6 mins that means only 3.33% of the showers are on at the same time. And of course not EVERYONE has a shower in the morning at those times plenty of people have showers before or after then so the real figure is probably less than 2% of showers are on at the very peak usage times

This should be obvious by the fact millions of electric showers already exist and there is no stress on the grid and electric showers are legal to sell and buy suggesting there is no real problem in integrating a lot more

I would guess at least 50% but more like 60-70% of showers are currently Gas powered, the same with ovens for Christmas day, its the local sub station i would worry about and may need upgrading, Tower blocks that are all electric have their own subs in the basement do they not?


Anyway by the time this idea is sorted out and started to roll out, gas boilers may be outlawed completely!

Martyn1981

markin wrote: »

Anyway by the time this idea is sorted out and started to roll out, gas boilers may be outlawed completely!

That's a good point. With new builds prevented from using FF's by 2025, I am kinda expecting some sort of retro-fit ban for GCH to be announced, perhaps from 2030/35 or so.

But, and here's the interesting part, if new builds avoid gas, and older properties get better insulated, then the total demand for gas will drop.

For longer storage of excess RE generation (beyond intra-day battery storage) we are probably looking at hydrogen or bio-methane. Add on bio-gas production from current schemes and Ecotricity's hope to produce almost all future (meaning lower) domestic gas demand from grass mills, and we may not see a ban on GCH for existing systems.

Basically, bio-gas for gas boilers, or RE leccy for heat pumps, makes far more sense than trying to cobble together a dual system.

Disclaimer - I have a cobbled together system already, in that I've added a small 3.5kW ASHP (also known as an air conditioner) to heat my living room when whole house heating isn't needed, and even to heat the whole house when temps are marginal simply by 'leaving the living room door wide open'.

GreatApe

markin wrote: »

I would guess at least 50% but more like 60-70% of showers are currently Gas powered, the same with ovens for Christmas day, its the local sub station i would worry about and may need upgrading

Well you can upgrade the substation (aka transformer) or you can just not let the hybrid boilers exceed the local limit and the amount of spare capacity changes with hour to hour

Tower blocks that are all electric have their own subs in the basement do they not?

Maybe but what is the argument you are trying to make here?

If you size a transformer for a tower block you would size it to meet peak demand of the homes in that tower block. For instance if there are 100 flats you may size it so each flat can draw 3KW at peak so a 300KW transformer. But the average flat uses 300 watts on average so the transformer has 90% spare capacity on average.

Anyway by the time this idea is sorted out and started to roll out, gas boilers may be outlawed completely!

This idea would take no more than a year or two to implement

Gas boilers can not be outlawed there is no realistic alternative
But non hybrid boilers can be outlawed

GreatApe

Martyn1981 wrote: »

Basically, bio-gas for gas boilers, or RE leccy for heat pumps, makes far more sense than trying to cobble together a dual system.

What is the downside? The only downside is you add perhaps £20 cost to the boiler in adding a 3KW electrical element to a gas boiler. You could regulate these into existence in just 1-2 years and start having ~2 million installed each year as old boilers break and are replaced by these hybrid boilers. You dont even need to turn on the electric side for years until wind power starts to become excessive during some periods of time

£20 cost. how much does it cost to get rid of the gas combi boiler and install a heat pump for water and space heating? £5k £10k £15k? How much additional work is needed to the house beyond the higher cost? Space for a tank? Ripping out the old rads for bigger new rads?

Also more importantly, on a cold winters day a heat pump adds to the grid which means peak thermal capacity has to be higher. While the hybrid boiler does not add to winter demand or the need for more thermal capacity

Plus these do not displace heat pumps or crazy ideas like hydrogen if they turn out to be not so crazy
You could spend £20 on a hybrid boiler today
Then if a heat pump makes sense for you you can install a heat pump down the line
The loss is your £20 .... hardly anything

zeupater

Reed_Richards wrote: »

Only if fuel costs don't change with time. That's never really been the case with electricity.

I have a combi and it's dreadful, mainly because it is a retrofit into a house that used to have a tank and the retrofit made long pipe runs even longer.

Many older houses were built around the need for a storage tank. Hopefully if well-insulated they won't lose as much as 2 kWh per day. 4-5 kWh of storage is good in battery terms and you can charge up the tank during peak hours of solar PV output when electricity ought to be very cheap.


My central heating is set to run at 18.5 C from 7:30 until 9;00, 19 C from 9;00 until 17:00, then 20 C from 17:00 until 22:30. In the evening when you are more sedentary then even 19.5 C feels cold. If you really think that you can have the house temperature vary by 3 degrees without feeling freezing at some times and boiling at others then you can't have tried it yourself

Hi

Electric boilers are already available & aren't by any means cheap (~£1000-£4000) so combining electricity & gas within a single unit is definitely going to considered to be a 'premium' product on price lists, probably between a £few-hundred to ~£1000 above a standard offering ...

As you start to move above around a 3kW load you're moving into an area where a dedicated & uprated circuit is required with likely loads of 40-60Amps (~10kW-15kW), so allow for adding costly rewiring from the distribution board to wherever the boiler is installed (ie close to the current boiler/gas supply!) ... by the way, a gas boiler rated at ~15kW would be considered to be undersized to meet the heat-loss requirements of most homes ...

The place to start then is property heat-loss, calculate that first and simply work from there .... our gas boiler is pretty typical for a medium sized property & capable of heat output of ~30kW, so moving away from gas to electricity whilst not impacting on the users' normal usage pattern would require a three phase supply to be installed (~120A before any other load!!), so allow £quite-a-few-thousand for an upgrade ... possibly £5-£15k on average, moving well past £25k for quite a few! ....

So, the ability to automatically/seamlessly switch between electric resistance heating and gas has a few more issues & costs than simplistic thoughts would first suggest ... with rewiring, 3 phase supply installation, supplier premium unit pricing & still needing connection by suitably registered installers as well as servicing requirements in line with standard gas boilers, you're talking about a solution which is likely far more expensive than a GHSP setup, so well above that of a wet ASHP system and many times that of an air-to-air ASHP system, which would be cheaper than a gas boiler in the first place .... then again, there's the running & maintenance cost ....

Earlier in the thread you mentioned ...

... I think you probably need a thermal store to be used in conjunction with the boiler so you can run the boiler when it is cheap to do so and extract the heat when you actually need it. ...

... which is far more sensible as it uncouples demand from source of supply as well as smoothing out the initial heat demand peak ... in many cases a small resistance element could raise the heat-bank temperature over many hours, similar to charging a battery, before allowing the energy to be released over a shorter time (evening heating requirement etc) ... but that creates a further problem for the grid ... the low load (3kW?) likely means that it's required for far more hours than the number of available off-peak hours ....

No, it makes very little sense to spend/divert money on reinforcing supply infrastructure and wasting resources on interim home heating measures when the alternative solution would be energy inefficient, less costly and cause significantly less disruption to the electrification of transport (ie - not competing as hard for excess generation!) ....

... hello heat-pumps, looks like you're the logical answer! ... :cool:

HTH
Z

Reed_Richards

Zeupater, I enjoyed reading your response to my post but I wonder if you have me confused with the OP, GreatApe? I was responding to his/her post, #4 of this topic, pushing back against some of the assertions made.

One of the options I was considering to get myself hot water promptly was an instantaneous electric water heater that could cope with a hot feed and so would cut-out when the water from the combi boiler eventually made it through my long pipe run. But the power requirements for this were such that I would have had to uprate my mains fuse to make it feasible and this put me off that idea. This chimes in with your comments about the heavy demand that would be placed on the mains supply.