Heat Pump vs Gas Boiler: Relative Climate Impact

[SimonD]

13 hours ago, ProDave said:

If I read it right, they updated all the insulation levels to meet current building regs requirements, then fitted a heat pump to achieve that 65% reduction?

 

I believe they looked at the retrofit upgrade measures required to reduce heating demand to below a certain figure, which in effect means the reductions were achieved through retrofit insulation alone, in order to make sure the heatpump would be as efficient as possible once installed. From the papere:

 

"Significant improvements are seen with the addition of SWI, with heating demand and system input power to 1 kW reduced by 50–54% and 60–66% respectively. "

 

"Adopting a higher specification U-value for all measures is shown to reduce energy demand by almost 80%. This highlights possible scope for improvement in current building regulations."

 

16 hours ago, Green Power said:

By my calculations the estimated reduction from putting a heat pump in is 77%.

 

Would you care to share your actual data and calculations?

[ProDave]

2 minutes ago, SimonD said:

I believe they looked at the retrofit upgrade measures required to reduce heating demand to below a certain figure, which in effect means the reductions were achieved through retrofit insulation alone, in order to make sure the heatpump would be as efficient as possible once installed. From the papere:

So at last someone is talking about the real problem.  How to deal with the lousy insulation and air tightness of the uk's old housing stock.  Properly upgrade the insulation and you can get a massive reduction in energy usage.  You still get that reduction in use if you kept the old heating system, changing it for a heat pump is almost incidental.  But anyone reading this and not fully understanding will think the heat pump is an essential part of this.

[JohnMo]

16 hours ago, Green Power said:

There is no way you can reduce your emissions by 77% with insulation.

There are windows, doors, ventilation heat losses also.

 

Interesting your house is 38% the size of mine, yet our heating consumption is 42% of yours.  So your heating demand could be 4000 x 38% = 1520kWh per year, so about 80+% better.

 

This also equates to about 1kW heating demand at -5 degC.  So would only need heating on the coldest days.

 

So not seeing why you can't make the savings, people convert existing housing stock to passivhaus standards, which is better again.  But it takes  work.  Instead you stand saying look at me, I have installed a heat pump, I saved the planet.

 

Insulation, airtightness and general energy reduction by decreased heat loss is the topic you should be pushing!  That is what we need, a real reduction in primary energy usage.

[SteamyTea]

44 minutes ago, JohnMo said:

That is what we need, a real reduction in primary energy usage.

Brings up an interesting point.

If we burn fossil fuels to heat buildings, we can relatively easily work out the efficiency of the delivered energy.

How should that be calculated with renewables.

Wind turbines have a theoretical limit, and an in situ capacity factor. Solar is similar.

Large scale hydro has a huge catchment area, as well as the reservoir area. How do we calculate the primary energy of that. Should we take in all the potential energies involved, or just the turbine efficiency, as the primary source.

Then what happens with by products. A dam may make for better agricultural irrigation, rather than pumping ground water.

Going to take a lot of thinking about.

Edited November 6, 2022 by SteamyTea

[JohnMo]

But should we concentrate on what is in our control the building we live in and potentially building other people are renovating or building from new.  By giving sound, well thought through alternatives, to standard building regs levels of insulation and airtightness etc.

 

Hydro have a number issues never really discussed, like anaerobic decomposition of everything the water has covered, emitting methane for example, which is way worse than CO2. 

[SteamyTea]

22 minutes ago, JohnMo said:

Hydro have a number issues never really discussed, like anaerobic decomposition of everything the water has covered

Discussed quite a lot in the more academic circles and policy making committees.

23 minutes ago, JohnMo said:

emitting methane for example, which is way worse than CO2. 

Only over the first decade or so. Can't remember the actual number if decades where it equalises with CO₂, but seem to remember it was between 2 and 4.

Worth remembering that a rise in temperature today is much more damaging than the same rise spread over a few decades. It is the rate of change that is important, rather than the absolute rise in temperature.

Given enough time humans, and a lot of wildlife/plant life can adapt.

[Green Power]

7 hours ago, SimonD said:

 

Would you care to share your actual data and calculations?

The 77% is calculated in the original post in this thread. Keep in mind that the heat pump was only installed a few weeks ago and so this is based on an untested rough prediction of a COP of 3.4.

[Green Power]

7 hours ago, JohnMo said:

There are windows, doors, ventilation heat losses also.

 

Interesting your house is 38% the size of mine, yet our heating consumption is 42% of yours.  So your heating demand could be 4000 x 38% = 1520kWh per year, so about 80+% better.

 

This also equates to about 1kW heating demand at -5 degC.  So would only need heating on the coldest days.

 

So not seeing why you can't make the savings, people convert existing housing stock to passivhaus standards, which is better again.  But it takes  work.  Instead you stand saying look at me, I have installed a heat pump, I saved the planet.

 

Insulation, airtightness and general energy reduction by decreased heat loss is the topic you should be pushing!  That is what we need, a real reduction in primary energy usage.

 

My kWh for gas includes hot water, but most of it is heating. That may slightly affect your calculation above, but not much.

 

What could be helpful to people following this topic  is if you explain what year your house was built in, how well insulated was it from the start. If most of the heat demand reduction was done well after the original build, that might be an interesting case.

 

I think I did say earlier that insulation can only save 5%-30%, depending on the type of insulation (or something along those lines). That wasn´t a very clear statement (sorry) but I meant that each type of insulation can save this amount. Say it´s 30% for cavity wall insulation in every wall. 10% or 20% for loft insulation. 5% for sealing paces with drafts. These are rough guesses. I just read these numbers in some articles.

 

In theory sure you can get a big overall saving  if you spend thousands and thousands on a massive retrofit. I´m not sure how many of the people that just respond to "heat pump" with "insulation" are actually doing that though. It only cost me about £1000 extra to put in a heat pump (when you factor in that the gas boiler was dying and I would in any case have had to get a new one). It would have cost way more to do a deep retrofit, I think. I do think that the kind of deep retrofit needed to achieve 60%-90% reductions in heating demand on old houses is likely going to be impractical, expensive, or difficult, but I could be wrong, I don´t have a great knowledge on this, and I don´t feel that strongly about it, and it will vary by case.

 

For my house, the side wall already has cavity wall insulation and has had for years. The other two walls are difficult/expensive impossible to do (I´ve been told) because of the type of wall with cladding on it. I did increase the loft insulation a few months prior to installing the heat pump. I have also had someone look at the window seals and a few are not working properly, so I plan to replace those next summer. I´m not sure what else I can really do.

 

There is also the fact that replacing a gas boiler with a heat pump reduces the emissions impact of hot water, whereas insulation changes don´t have (much) effect on that.

 

Maybe we are arguing too much about heat pump or insulation, though. If anyone has achieved a deep retrofit with similar levels of emissions reduction or better than what I did with a heat pump, then good for you.

[PhilT]

For me the overriding objective of having a heat pump is to reduce our dependence on fossil fuels generally but especially from Russia and the middle east, mainly for reasons of energy security. The intention is for gas heating to be phased out. Whether that happens or not remains to be seen but gas supply will reduce and gas prices increase. Yes obviously insulation, air tightness are important but you still need a heat source. A heat pump is the logical choice as it uses a fraction of the energy of even the most efficient gas boiler. Costs are a major stumbling block but should come down over time with economies of scale - it's a very basic form of technology.

[Kevm]

@Green Power Thank you for this.  Some of your assumptions may be open to debate but your analysis is very useful.  

 

I think it stands up well to the attempts to discredit it by disputing minor points and indulging in a bit of 'whataboutery'. 

     

Edited November 7, 2022 by Kevm

[joe90]

On Laura keunsberg programme on Sunday a chap (can’t remember who he was) was spouting the argument there was not a problem with burning gas etc as it was standard technology to capture the Co2 and dispose (bury?) it. I would have thought that was expensive to do?, not possible on everybody’s gas boiler!!!

[markc]

8 minutes ago, joe90 said:

On Laura keunsberg programme on Sunday a chap (can’t remember who he was) was spouting the argument there was not a problem with burning gas etc as it was standard technology to capture the Co2 and dispose (bury?) it. I would have thought that was expensive to do?, not possible on everybody’s gas boiler!!!

I saw that, I think or took it that he was on about power stations, but he did say all the co2 

[Nick Thomas]

On 05/11/2022 at 21:01, ProDave said:

If I read it right, they updated all the insulation levels to meet current building regs requirements, then fitted a heat pump to achieve that 65% reduction?

 

No. Table 5 shows what the insulation measures achieve by themselves; the final column tells us what percentage of houses still need a heat pump with > 1kW input to meet space heating needs after the measure is applied (DHW is excluded throughout).

 

The UK's existing housing stock is *so bad* that a ~60-80% reduction through adding insulation really isn't all that incredible.

 

No particular reason not to do both the refit *and* the heat pump, of course. They compose very nicely.

Edited November 7, 2022 by Nick Thomas
(clarify final column in table 5)

[SimonD]

45 minutes ago, joe90 said:

On Laura keunsberg programme on Sunday a chap (can’t remember who he was) was spouting the argument there was not a problem with burning gas etc as it was standard technology to capture the Co2 and dispose (bury?) it. I would have thought that was expensive to do?, not possible on everybody’s gas boiler!!!

 

I'm afraid the guy must be deluded and it's a shame if the programme could not challenge this. I've noticed it happenng quite a lot in the media where people, some of them claiming to be experts, are making false claims about techologies and unfortunately the interviewers simply don't have the technical understanding to question or challenge it.

 

But yes, also pretty impossible to do with a gas boiler, unless you use the green gas model being proposed by Ecotricity which involve growing and using local grass in otherwise useless farmers fields, then the growth at least sinks some of the carbon. 

[SimonD]

28 minutes ago, Nick Thomas said:

The UK's existing housing stock is *so bad* that a ~60-80% reduction through adding insulation really isn't all that incredible.

 

Indeed, it's all relative, isn't it. A little bit of insulation can go a long way, but we mustn't forget that this is a once in a lifetime purchase that also insulates you from the energy market. There's a big difference between passive and active energy saving measures.

[SteamyTea]

1 hour ago, joe90 said:

capture the Co2 and dispose

 

1 hour ago, markc said:

power stations, but he did say all the co2 

 

21 minutes ago, SimonD said:

I've noticed it happenng quite a lot in the media where people, some of them claiming to be experts, are making false claims about techologies and unfortunately the interviewers simply don't have the technical understanding to question or challenge it.

https://ieefa.org/resources/carbon-capture-has-long-history-failure

 

Seems great to help recover more oil from semi-depleted wells.

 

22 minutes ago, SimonD said:

unless you use the green gas model being proposed by Ecotricity which involve growing and using local grass in otherwise useless farmers fields, then the growth at least sinks some of the carbon.

Even that is is not as good as just leaving a field to grow whatever happens there naturally, usually trees.

 

There is so much bollocks spoken about carbon capture and how just capturing from the exhausts and pumping it underground solves the problem.  Just another layer of technical complexity and expense.

Seems mad when we already have the technology we need.

[Ferdinand]

1 hour ago, Nick Thomas said:

 

No. Table 5 shows what the insulation measures achieve by themselves; the final column tells us what percentage of houses still need a heat pump with > 1kW input to meet space heating needs after the measure is applied (DHW is excluded throughout).

 

The UK's existing housing stock is *so bad* that a ~60-80% reduction through adding insulation really isn't all that incredible.

 

No particular reason not to do both the refit *and* the heat pump, of course. They compose very nicely.

 

I think those claims are somewhat overegging it, and perhaps overstating the potential.

 

But I think it depends what you are talking about reducing - presumably the heating cost on a totally uninsulated house?

 

You won't achieve that when the traditional model for a trad house (eg as used by Energy Saving Trust) has 25% of heat losses via air leakage, and some more (10%?) via doors and windows which can't be insulated.

 

If working on overall society-wide numbers we also need to remember that the average EPC number is already up at around 68, so we already have a big chunk of the low hanging fruit.

 

This is the shift from 2010 to 2020. It becomes more difficult and far less cost-effective once your trad house gets to a C, and we will need to rely more on decarbonised energy supplies there.

 

F

[Ferdinand]

On insulation, these are levels by house type etc from the 2022 English Housing Survey.

 

Again there is still much opportunity, but we have a lot of the low hanging fruit already. This table really rewards detailed study - for houses with trad lofts we are down to 10-15% only having less than 100mm .

 

The tough ones are the hard-to-insulates. Solid walls, no loft, flats etc.

 

[ProDave]

21 hours ago, PhilT said:

For me the overriding objective of having a heat pump is to reduce our dependence on fossil fuels generally but especially from Russia and the middle east, mainly for reasons of energy security. The intention is for gas heating to be phased out.

That deserves some scrutiny.

 

You replace your gas boiler with an air source heat pump.  You don't burn any gas any more?  WRONG.

 

At the moment, we do not have anything like 100% non carbon electricity production, a scarily high percentage of electricity is generated in a gas fired power station.  So you add a new ASHP to the electricity grid and it is an indisputable fact that will increase the load on a gas fired power station.

 

So now the question becomes does that burn more or less gas than a gas boiler heating the same house?  One would hope less but does anyone have any figures?   

[markc]

A company we know has been asked to supply a further 1000 (over next 2 years) 0.5MW diesel and gas generators to ease demand on the grid.

[PhilT]

10 minutes ago, ProDave said:

You replace your gas boiler with an air source heat pump.  You don't burn any gas any more?  WRONG.

 

At the moment, we do not have anything like 100% non carbon electricity production, a scarily high percentage of electricity is generated in a gas fired power station.  So you add a new ASHP to the electricity grid and it is an indisputable fact that will increase the load on a gas fired power station.

 

So now the question becomes does that burn more or less gas than a gas boiler heating the same house?  One would hope less but does anyone have any figures?   

Yes say the average UK boiler is 75% efficient, using 16k kWh pa  gas to supply 12k kWh pa heat. A modern ASHP will use 3k kWh pa, which takes around 4kWh pa of gas at the generating station. Currently the UK grid is using less than 50% gas so only 2k kWh pa on average. I grant you the overall grid demand will increase massively but there are plans (haha!) to increase that through installation of renewables and nuclear, and reduce fossil fuel still further.

Edited November 8, 2022 by PhilT

[joe90]

10 hours ago, SimonD said:

useless farmers fields,

? Grass land is used for grazing animals or mowing fir silage etc. I think there is more to be done with gas collection from slurry pits etc on farms .

[SteamyTea]

4 minutes ago, joe90 said:

I think there is more to be done with gas collection from slurry pits etc on farms

Isn't that perpetuating the problem as converting the slurry to methane does not allow the land to become a natural carbon store.

Better to get rid of the slurry source, or just spread it on fields (adhering to all the other environmental laws).

[joe90]

4 minutes ago, SteamyTea said:

Better to get rid of the slurry source,

All become vegan..? Slurry is collected when cows are indoors, milking etc.

4 minutes ago, SteamyTea said:

or just spread it on fields

Still produces methane in the atmosphere 🤷‍♂️, as been said before we will not stop burning gas overnight so if we burn the methane it helps power security (🖕to Putin) and possibly not rely on world gas prices.

[Jilly]

What is your view on this, an off grid family who produce their own methane from waste food etc, just sufficient for their own use:

 

 

 

https://www.facebook.com/246638455855096/posts/as-well-as-biogas-for-the-kitchen-biff-the-biodigester-also-produces-mineral-ric/929685204217081/