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Author Topic: How much energy does it take to deliver gas to UK homes and businesses?  (Read 2361 times)
GarethC
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« on: July 15, 2019, 09:06:55 PM »

I've always assumed it's pretty negligible, but, especially given much of our gas is now imported LNG, which takes energy to liquefy, it occurs to me that perhaps it's not. Does anyone know the energy required per kWh delivered? Matters, I think, if I'm trying to compare accurately the emissions from gas boilers compared to heat pumps.
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splyn
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« Reply #1 on: July 15, 2019, 11:29:11 PM »

I've always assumed it's pretty negligible, but, especially given much of our gas is now imported LNG, which takes energy to liquefy, it occurs to me that perhaps it's not. Does anyone know the energy required per kWh delivered? Matters, I think, if I'm trying to compare accurately the emissions from gas boilers compared to heat pumps.

I don't have a direct answer, but the government publishes data showing the emissions factors for natural gas here:

https://www.gov.uk/government/publications/greenhouse-gas-reporting-conversion-factors-2019

The 4th worksheet tab, 'fuels', gives the direct emissions for burning natural gas as obtained from the gas mains labelled 'natural gas' as distinct from 'Natural gas (100% mineral blend)'. The former accounts for imported LNG and biogas injected into the grid. The figure given in 0.20428 kg CO2(equivalent) /kWh (net CV) which includes the CO2, methane and N2O emissions.

Now to address your question, the worksheet labelled WTT- fuels gives the total upstream emissions (well to tank) which include gas production, refining, transport and methane leakage (fugitive emissions) in the supply chain (approx 1% in the transmission network). The figure accounts for the amount of imported LNG (which has been decreasing in recent years) which, as you state, suffers increased emissions due to the extra liquifaction and transport energy costs, .

The figure given is 0.02657 kg CO2eq/kWh, or 13% which actually is pretty good compared to 27% for petrol and 23.7% for diesel.

If you want the gritty detail, the methodology paper specifies the way the emissions factor are derived; the 2019 is, I believe, due out very soon, but the 2018 paper references this paper as the source of the numbers for natural gas:

https://ec.europa.eu/energy/sites/ener/files/documents/Study%20on%20Actual%20GHG%20Data%20Oil%20Gas%20Final%20Report.pdf

Note that the 1% leakage rate for natural gas comes from BG but others claim it is much higher so beware emission factors with 3 or more significant digits of precision.

Also don't forget to do the same calculations when estimating emissions from heat pumps which include leakage of the refrigerant - the spreadsheet gives the emissions factors in the 'Refrigerant and other ' worksheet but I'm not sure where you'd find the leakage rates or the rest of the WTT emissions for heat pumps.

[EDIT] The relevant section of that last link is '3.7.4 UK Natural Gas Supply'  starting on page 183. Table 3-53, page 186 answers part of your question.

Table 3-52 shows UK methane emissions at 0.622% by volume, from 2012 data, but it does state this is increasing as gas production declines.
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The  own  use  of  natural  gas  energy  in  the  national  transmission  system  is  0.00492 joules/joules  delivered,  however  this  includes  the  regasification  energy  which  is  entered separately  in the  model.
« Last Edit: July 16, 2019, 01:52:14 AM by splyn » Logged
pantsmachine
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« Reply #2 on: July 16, 2019, 07:36:02 AM »

You can also if you like take into account all the energy to survey the fields, test drill wells, complete wells then install the subsea control structure and pipelines to bring the gas to shore, process, store, meter and trade  then pipe or transport it to its required boiler or gas ring.

 Truly mindblowing and a massive human endeavour. Not sure it can be done to a final decimal point? I was involved in the race to bring Egypt Zohr field & many other over the decades online. At one point we had 9 ships with around 5,000 men bring flown into Egypt and that manpower was working 12hr shifts 24/7 for two years. That was epic!
« Last Edit: July 16, 2019, 09:51:04 AM by pantsmachine » Logged

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GarethC
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« Reply #3 on: July 16, 2019, 10:02:36 AM »

Thanks both, that's -extremely- helpful and much appreciated. On reflection, though, if I'm comparing the emissions of a gas boiler to those of a heat pump using gas-derived electricity (the appropriate assumption for marginal grid load I think), I suppose the delivery emissions cancel out largely.

In which case, I'm back to my current estimate of ASHPs needing to manage an SPF of 2.2 to emit less than a gas boiler, but I'm going to dig into the figures provided some more to finesse.

Pantsmachine's (!) point is an interesting one too. I wonder how the infrastructure and other development and production costs of gas compare to that of, say, offshore wind?
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pantsmachine
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« Reply #4 on: July 16, 2019, 01:11:24 PM »

Offshore winds a doddle in comparison. Hardest thing there is shallow water tidal currents. Smiley Start up costs are miniscule in comparison.
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HUGE insulation depth.
5.12 kw PV system with Solar edge.
4.8 kw Pylon tech battery storage.
All Low energy bulbs.
Solar I boost charging 210 ltr OSO system tank.
Balanced & zoned CH wet system & Hive 2
Wood fired thermosiphon cedar hot tub.
Masanobu Fukuoka inspired veg garden & fruit trees
M
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« Reply #5 on: July 16, 2019, 01:17:47 PM »

I've always assumed it's pretty negligible, but, especially given much of our gas is now imported LNG, which takes energy to liquefy, it occurs to me that perhaps it's not. Does anyone know the energy required per kWh delivered? Matters, I think, if I'm trying to compare accurately the emissions from gas boilers compared to heat pumps.

I thought only a small percentage of our gas was LNG, possibly single digits?

Our gas consumption has fallen steadily, and LNG is expensive, so it's brought in when our (too small) reserves run down. So as we use less, I assume we 'run low' less often, but perhaps a sustained cold spell might change this.
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GarethC
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« Reply #6 on: July 16, 2019, 01:28:32 PM »

https://www.britishgas.co.uk/the-source/our-world-of-energy/energys-grand-journey/where-does-uk-gas-come-from

9% LNG in 2017, but 47% imported by pipeline. Only 44% domestically produced.
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Philip R
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« Reply #7 on: July 16, 2019, 06:41:54 PM »

Gas is transmitted through the UK using gas turbine powerred compressors, such a legacy plant exists in Leicestershire at Hinckley.

(Remember the dispute a few years ago between Russsia and Ukraine over the use (supposed theft) of "technical gas". This is the gas used to power the gas turbines to push the gas through the pipeline.)

LNG from Qatar should require more energy to liquify it than say the recent LNG shipments brought in from Yamal in Northern Russia. Northern Russia should be a good place to run a gas liquifaction plant because it is so cold. snow

GarethC As you are comparing the numbers for a gas boiler and electric heat pump, part powerred by gas. Have you considerred a gas absortion heat pump. The figures and performance of the Robur K18 are interesting. Mentioned on the foum before. BTW, I do not have one or have any connections with the company or UK importer.
If a smaller output device was availible and a bit cheaper, I would consider one for a heat only gas boiler replacement.

Philip R
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M
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« Reply #8 on: July 17, 2019, 07:04:25 AM »

https://www.britishgas.co.uk/the-source/our-world-of-energy/energys-grand-journey/where-does-uk-gas-come-from

9% LNG in 2017, but 47% imported by pipeline. Only 44% domestically produced.

Thanks, I thought it was pretty small.

Seems to me that if the UK had a sensible amount of gas storage, then we would avoid LNG and peak prices too hopefully. With the add on benefit of avoiding the additional energy consumption from liquefying and transporting LNG.
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Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
GarethC
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« Reply #9 on: July 17, 2019, 11:40:45 AM »

GarethC As you are comparing the numbers for a gas boiler and electric heat pump, part powerred by gas. Have you considerred a gas absortion heat pump. The figures and performance of the Robur K18 are interesting. Mentioned on the foum before. BTW, I do not have one or have any connections with the company or UK importer.
If a smaller output device was availible and a bit cheaper, I would consider one for a heat only gas boiler replacement.
Philip R

My main issues other than cost with the Robur, which looks a very interesting option in many ways, are that it claims only -up to- a 35% reduction in space heating "power demand" compared to a high efficiency gas boiler, which I could achieve with a well specced conventional ASHP (space heating SPF of 3.3 needed).

I also suspect that 35% equates to an -emissions- reduction of less than that, as the Robur needs more leccy to run than a gas boiler. So I think I'd reduce emissions more with an ASHP already (if you take my argument that marginal leccy is gas generated).

Also, the Robur still runs on gas, so it locks you into using fossil fuels, with limited further gains unless gas supplies become greener due to biogas, green hydrogen etc, and there's not a strong clear plan for that to happen. Whereas ASHP associated emissions will reduce as grid intensity continues to fall, in a fairly predictable fashion.

Now, new conventional ASHPs still run on FGases with high, albeit greatly reduced, global warming potential. People still talk about this as a major problem, but if I understand it correctly, that's only if the refrigant leaks. What I can't understand is how great the risk of leakage is. If it's high, I've got a problem, but I can't see why it should be?
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Philip R
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« Reply #10 on: July 17, 2019, 04:23:29 PM »

Thanks for your thoughts on the Robur and not wanting to tie into fossil fuels.

The EU Commission report looks interesting , I will have a look at it.

I found some data on petrowiki.org regarding LNG production and transport.

Gas liquifaction 8 - 10 %  fuel loss as percentage of feed gas. (That will warm up the Arabian and Red seas,)

Shipping. 0.15 to 0.2% of LNG cargo per day ( 480 nautical miles). If boil off gas used for propulsion and no reliquification plant fitted ( I.e Not using distillate diesel or residual heavy fuel oil for propulsion)

Regasification 2 - 2.5 %

It should be said that The isle of Grain LNG plant was retrofitted with condenser water recovery from the neighbouring power plant, thus utilising waste heat to vapourise the LNG back to its gaseous state.

Similarly the plant in Dunkirk in France utilises some of the seawater discharge from Gravelines NPP.

Philip R
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