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

GreatApe

zeupater wrote: »

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 ...

https://www.screwfix.com/p/redring-ms6-undersink-stored-water-heater-1-5kw-6ltr/5314p

What I am referring to is pretty much this £68 retail and incorporating one inside a boiler will be even cheaper because some/many parts will be shared. Remember that is retail which means to add it on is going to be perhaps only 1/3rd that cost

https://www.screwfix.com/p/ariston-aures-electric-instant-water-heater-9-5kw/305fj
Or something like this if the standing heat losses of the above are too high

Here is an electric instant water heater £98 retail. again that is retail prices so the manufactured price is likely less than 1/3rd that figure

The cost of incorporating one of the other of those is going to small most likely in the £10-£40 range above a standard offering. To make the boiler smart is also not going to be expensive think of the very cheapest smartphone and that is even overkill for the smarts needed

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 ...

As noted previously where the electrical supply is only 3KW you can set it to 3KW and that figure is still very large and can meet most household needs.

15KW boiler is more than sufficient for even the largest homes central heating heating needs. My home is large 6 bedroom old and inefficient solid brick design and I use ~150KWh in a cold winter day which is ~6.25 KW heat constantly on

A more typical house probably uses no more than 3KW for their central heating needs. Also remember 3KW electricity is closer to 3.5-4KW natural gas due to the difference in efficiency

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! ....

You are trying your best to nit pick

As noted already, it would be a HYBRID system so can use one or the other or both fuels

Depending on the setup the 3KW electrical element can provide most the needs.
There are three main types of heating system in the uk. Combi with no tank and two types of systems with tanks one pressurized one pressurized. If you are not a combi, ie you have a tank, said boiler can provide all your heating needs with the 3KW electric side feeding the tank as a buffer. IF you are on a combi your hybrid combi can provide more or less all your central heating needs and a fraction of your hot water needs

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 ....

As noted, you do not need any more than a 3KW electrical side to achieve what is aimed for
You are nit picking and trying to size a 30KW electrical heater. Which would be costly but no one needs that. BTW there already exists instantaneous electrical heaters which is what you are trying to describe for instance this

https://www.screwfix.com/p/ariston-aures-electric-instant-water-heater-9-5kw/305fj

Costs £98

And of course all electric showers are instantaneous electric heaters

Earlier in the thread you mentioned ...
... 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 ....

You can have a small water buffer as per

£68 with 6 liters tank for buffering
https://www.screwfix.com/p/redring-ms6-undersink-stored-water-heater-1-5kw-6ltr/5314p
or £140 with 15 litre tank for buffering

Imagine the latter unit inside a gas fired boiler
It has a 3KW element and 15 liter storage.
Sufficient to provide for all water heating needs (except shower/bath) and 3KW enough to provide for the bulk, and probably 100%, of central heating needs

When a shower is turned on you have the 3KW element on, plus however much heat is from natural gas to allow a suitable flow rate. So it might be 3KW eletrical 12KW natural gas to combine to give 15KW for the shower

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

There exists two countries which are more or less 100% electrically heated, Norway and Sweden

If heat pumps are such an obvious answer, why do they not use heat pumps?

Plus as I have shown in this post, the cost of a hybrid electric/gas boiler will be insignificant and probably close to the £20 mark on top of a normal gas only boiler. The cost of converting to a heat pump system is much more

Also heat pumps add to demand during winter peaks
Hybrid boilers do not
This means if you build out heat pumps you have to build out more thermal capacity (CCGTs) to guarantee supply.

GreatApe

Some people seem to be finding this difficult to grasp
Imagine a normal boiler, it costs what a normal boiler costs

Now imagine an instant water heater, it costs £77 retail for a 9.5KW model
https://www.plumbnation.co.uk/site/ariston-aures-9-5kw-electric-instantaneous-water-heater/

Lets say you install both into a home and a smart controller either picks the boiler or the instant water heater to be used to heat your home/hot-water. When you turn your central heating on or turn your hot water tap on, the smart controller goes onto the internet and asks the grid 'Should I use electric or Gas' and the grid replies in 0.1 seconds to use electric if there is spare wind capacity in that moment but if there is no spare wind it says use gas

This electric heater can be set to 3KW where the limit is 3KW

Now instead of buying the two separately, you buy a hybrid electric boiler with the two combined inside the one housing. This means you do not have to pay £77 retail but can get it at manufactured prices of much less than £77 retail. (If it costs £77 retail for arguments sake you can probably but it for half of that wholesale. And half of wholesale prices if you build it into your own products yourself. Hence why I said probably close to £20 to integrate this into gas boilers making them hybrid boilers.

The only downside is this additional £20 cost which is nothing and probably worth having as it gives you backup for when the gas is down your home still has central heating powered by the electric side and some level of warm/hot water depending on 3KW/9.5KW setting


Really what is the downside? £20 increased cost

And the upside is you can just keep on building wind farms and the more you build the more your stock of hybrid boilers uses wind power and the less natural gas they use.

You have effectively built a 125% efficient distributed electricity to methane conversion plant

GreatApe

You have 50 GWh of excess wind on a winters day what do you do?

Currently the only option is to curtail it (we are assuming all other measures are saturated eg export via inter-connectors, the existing pumped hydro etc)

The hydrogen idea is to convert this 50GWh of excess electric to much less than 50GWh of hydrogen in an expensive process that requires buildings and people and machines and land and...

The hybrid boiler idea takes this 50GWh of excess wind electrical energy and offsets 60GWh of natural gas use that day

GreatApe

More or less what people do on a domestic level with iboost and solar
They heat their tanks with excess PV.
When there is no excess PV in say most winter months they use NG in their boilers

But on a national level it would be with wind power and hybrid boilers
At a national level excess wind would be diverted into the nations hybrid boilers

BTW similar can be achieved with one or multiple electric freestanding or wall mounted resistant heater connected to the internet. When there is excess wind power the grid tells those heaters to turn on and heat the home upto the thermostat temp. (which indirectly results in the boiler using less gas). Those would only save gas on central heating not on hot water though

zeupater

Reed_Richards wrote: »

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.

Hi

I effectively agree with your position and my post was addressing your content, the quoted text & the thread title as the OP (posting as 'GreatApe' & a number of other profiles he's used over the years) is on my ignore list specifically because of suggesting ridiculous ideas like this, along with a history of unsupported & heavily spun deceptive posts, particularly when solar or other forms of distributed generation or demand side microgeneration is involved ...

No doubt the latest bout of posts reference the points I raised and attempt to address them with dubious 'finger-in-the-air' science and pure guesswork because that's the usual approach employed to spark argument, but just think - if bivalent (gas + electricity) boilers were a good or economical idea to make use of off-peak excess generation then they'd already be around in numbers .... as they're not then there's either a market being missed by loads of companies, or no market exists for this technology combination at a scale that makes sense to manufacturers, but as mentioned, if there was then they'd be expensive pieces of kit as opposed to a standard gas boiler with an integrated immersion element, which should be supported by searching the web and analysing the cost differential between a couple of replacement electric immersion elements & either electric central heating boilers or electric combi-boilers ...

Regarding DHW & undersink heaters, as long as the flow at the tap isn't an issue (or it's restricted) then a 2-3kW unit is okay(ish) ... I have a good friend that has had a number fitted for years to address long pipe runs as you describe (big old listed farmhouse), but had awful issues with scaling so ended up paying around £1k for a whole house water softening system and something like £100/year to run it if I remember correctly .... amazing how it all adds up!! ...

We'll just continue to use our solar thermal, PV, heat-pump & biomass combination and retain the GCH boiler as a fallback for now & when battery prices become more realistic, add more PV, a decent energy storage capacity & lift the pumped heat capacity ...

HTH
Z

michaels

I don't think people who are talking about local distribution issues understand the idea.

If local demand is high then (winter evening etc) then it unlikely that there will be a curtailment situation from excess wind until we have a much larger wind build out. Thus curtailment will arise when demand is low and thus switching on electric heaters at this time will not put pressure on the grid.

WE have an iboost solar diverter, in the summer it sends excess solar generation to the hot water tank. We set the tank temperature on the gas boiler down to 50 and the electric thermostat to 70 thus we always have hot water but there is 'room' in the tank for solar storage. If the iboost was controlled via a remote signal so that it switched on to avoid wind generation curtailment then it would be win-win, the energy gets used and the curtailment fees are saved, I am sure that the energy could be sold to us for a price that was cost competitive with gas.

[note the iboost on a standard immersion is able to 'modulate' to match the amount of solar that would otherwise be exported so not even just an on/off solution.]

We could do the same with our EV, if it was cheaper per unit we would be happy to opt for charging when it suits the grid (obviously subject to a minimum amount of charge every morning and an override)

Our house is 170m2 and our boiler modulates between 5kw and 18kw and is plenty enough to heat and hot water.

Reed_Richards

zeupater wrote: »

Regarding DHW & undersink heaters, as long as the flow at the tap isn't an issue (or it's restricted) then a 2-3kW unit is okay(ish) ... I have a good friend that has had a number fitted for years to address long pipe runs as you describe (big old listed farmhouse), but had awful issues with scaling so ended up paying around £1k for a whole house water softening system and something like £100/year to run it if I remember correctly .... amazing how it all adds up!! ...

HTH
Z

Yes, that's useful to know. But a lot of under-sink heaters cannot cope with a hot water input whereas i want something that will heat water briefly but cut-out when the water from the boiler comes through. Is that what your friend had?

The water in my old house was very hard and I ended-up fitting a water softener because my wife decided she wanted to replace the bathroom because of the limescale left by years of hard water. Then we moved house instead. £100 a year for salt seems about right.

Hexane

michaels wrote: »

If the iboost was controlled via a remote signal so that it switched on to avoid wind generation curtailment then it would be win-win, the energy gets used and the curtailment fees are saved,

This is approximately what I'm involved in a trial of. Actually, the inverse too. The grid asks for my immersion heater to be turned on (or up) when there is surplus power that needs using up to avoid curtailment, and the grid asks for my immersion heater to be turned down (or off) when there is a shortage of power such that fossil fuel power stations might have to be used instead of my solar panels.

Fortunately, I live in an area with extremely soft water.

GreatApe

zeupater wrote: »

if bivalent (gas + electricity) boilers were a good or economical idea to make use of off-peak excess generation then they'd already be around in numbers .... as they're not then there's either a market being missed by loads of companies

There is no need for such dual fuel boilers today (or historically) because we do not have a situation yet where there are any significant times when the grid is overloaded with excess wind or solar power

We might get towards a situation around 2025-2030 when there will be times when wind will have to be curtailed. For instance one of the lowest demand days of the year is Christmas night. If demand is for instance say 19 GW and wind power output is 30 GW and we have say 5GW of nuclear and no export capacity on the interconnectors (as they too are on a low demand period)

You can either curtail 16 GW of wind and nuclear or you can send 16 GW into the nations hybrid electric boilers and in the process save 20 GWt of Natural gas

GreatApe

michaels wrote: »

I don't think people who are talking about local distribution issues understand the idea.

If local demand is high then (winter evening etc) then it unlikely that there will be a curtailment situation from excess wind until we have a much larger wind build out. Thus curtailment will arise when demand is low and thus switching on electric heaters at this time will not put pressure on the grid.

WE have an iboost solar diverter, in the summer it sends excess solar generation to the hot water tank. We set the tank temperature on the gas boiler down to 50 and the electric thermostat to 70 thus we always have hot water but there is 'room' in the tank for solar storage. If the iboost was controlled via a remote signal so that it switched on to avoid wind generation curtailment then it would be win-win, the energy gets used and the curtailment fees are saved, I am sure that the energy could be sold to us for a price that was cost competitive with gas.

[note the iboost on a standard immersion is able to 'modulate' to match the amount of solar that would otherwise be exported so not even just an on/off solution.]

We could do the same with our EV, if it was cheaper per unit we would be happy to opt for charging when it suits the grid (obviously subject to a minimum amount of charge every morning and an override)

Our house is 170m2 and our boiler modulates between 5kw and 18kw and is plenty enough to heat and hot water.

Another alternative is to fit smart convection heaters perhaps 1KW per room or a 3KW in a hallway or main room (or perhaps fan heaters). These are compact small powerful cheap heaters

When the home needs heating the boiler asks the grid is there excess wind available. If the answer is yes then the electrical convention heaters heat the home. If the answer is no then the gas fired boiler heats the home

Cost of such convection heaters are as low as £20 and the cost of a wifi socket is £10
So you could add 1 such heater to a house for £30 and it would allow 3KW of excess wind to be dumped into that house offsetting 3.5 - 4 KW of NG

Basically a smart way for buildings to choose between NG and Electrical heating depending on if there is spare wind capacity on the grid and sold to the customer at a rate no more than the equivalent heat from the gas boiler

This is a much better idea than trying to use surplus wind power for hydrogen or syn fuels obviously because it is ~125% efficient (1KWh of electricity converting into a saving of about 1.25 KWh of NG) vs much less than 100% for excess wind into hydrogen at much less than 100% efficiency. Not to mention one costs virtually nothing and the other is trying to set up a syn fuel industry to rival the petrochemical industry is size and scope