4 ms·

What's the actual GHG impact of this, given that it seems to involve moving over to natural gas, which is ~80x the impact in a 20 year span, and seems to leak

by Syonyk 5y ago

What's the actual GHG impact of this, given that it seems to involve moving over to natural gas, which is ~80x the impact in a 20 year span, and seems to leak from just about everything if you look at the methane levels downstream of anything that extracts or consumes large amounts of it? "Not using coal" is great, but if it's replaced with "We leak enough methane to have 10x the impact in the next 25 years," it's not a particularly useful direction.

Retric 5y ago
Natural gas isn’t replacing coal 1:1 or releasing nearly that much methane. Natural gas is actually quite expensive per kWh and ramps down in favor of every other energy source most notably Wind and Solar. However, it’s in effect the cheapest grid storage option as standby gas turbines are extremely cheap, and unburied methane doesn’t degrade. The only way to dislodge Natural Gas long term is to come up cheap grid storage options.
- jfengel 5y ago
  I'd be interested in seeing somebody work the math, but it doesn't seem unreasonable to keep natural gas on standby for the foreseeable future. If it's the sort of thing that has to run 10% of the year on nights of still wind, it's still a 90% reduction in fossil fuel consumption. That's not zero, but close enough that we'd start looking at the many, many other sources of CO2 and take the focus off of electricity generation. I am, of course, spitballing that number. I have no idea of it's 10%, or 25%, or 1%. Whatever it is, grid storage will be able to gradually phase out natural gas, without requiring any especially technological or legal breakthroughs. Save those for the other sources of CO2 -- farm animals, concrete, eternalized CO2 production due to globalized manufacturing, etc.
- tialaramex 5y ago
  However, the UK has a lot of Combined Cycle gas turbines. Almost all of them in fact. CCGT is more efficient but not so much in the spin-up/ spin-down phase. I suspect that it's much cheaper to spin a CCGT down to idle power output for a while than switch it off and soon after back on again. Which is fine so long as the difference between idle power and peak power needed in the UK matches the range of our CCGTs. A ramp of 5GW output, over two hours is something they're doing every day. But what if it was 10GW in thirty minutes? 15GW in twenty minutes? Something has to give. You can definitely see in the data on a night with strong winds, it isn't the CCGTs that stop first. As winds pick up, the CCGTs reduce power output, but at a low point they continue where they are and the UK stops importing power instead. To a considerable extent that's cheap French nuclear power, which means low carbon. There is no way gas is cheaper than that. I'd guess the CCGTs would rather lose money for an hour (or two?) selling electricity for less than the gas cost to make it, than switch off and start again cold in a few hours.
  - liketochill 5y ago
    There can be other system operation concerns such as stability and spinning reserve. If the intertie to France is lost and 3GW of nuclear power disappears and you are left with 100% wind then the severed system probably will be out of balance without something ready to go that can quickly. Also yes stopping and starting the machines are often when things go wrong. Things that are stopped tend to stay stopped and things that are running tend to stay running. Keeping a machine hot and spinning avoids thermal cycles and issues with stopping and starting oil pumps, brakes, bearings, etc that can occur.
  - Retric 5y ago
    That’s a very good point. Modern CCGT’s can ramp down to 20% without causing thermal cycling issues. As you point out that’s not zero, but you can very accurately forecast wind over the next 12 hours to only turn on an appropriate number of CCGT’s. Traditional gas’s turbines cost less and turn on and off in minutes and are therefore ideal in more supplemental role. Some designs can actually operate aim either mode, which seems to cover the downsides of each system though of course at higher costs and slightly lower efficiency. The market isn’t infinitely adaptable, especially in low population areas, but margins end up surprisingly consistent.
marcosdumay 5y ago
The main impact should be quite obvious, as CO2 is the one that accumulates. But even if you decide to ignore it, it's not clear if natural gas extraction leaks more or less methane than coal, but whatever way the scales goes, the difference isn't very large.

by Syonyk 5y ago

Retric 5y ago

Natural gas isn’t replacing coal 1:1 or releasing nearly that much methane. Natural gas is actually quite expensive per kWh and ramps down in favor of every other energy source most notably Wind and Solar. However, it’s in effect the cheapest grid storage option as standby gas turbines are extremely cheap, and unburied methane doesn’t degrade. The only way to dislodge Natural Gas long term is to come up cheap grid storage options.

jfengel 5y ago
I'd be interested in seeing somebody work the math, but it doesn't seem unreasonable to keep natural gas on standby for the foreseeable future. If it's the sort of thing that has to run 10% of the year on nights of still wind, it's still a 90% reduction in fossil fuel consumption. That's not zero, but close enough that we'd start looking at the many, many other sources of CO2 and take the focus off of electricity generation. I am, of course, spitballing that number. I have no idea of it's 10%, or 25%, or 1%. Whatever it is, grid storage will be able to gradually phase out natural gas, without requiring any especially technological or legal breakthroughs. Save those for the other sources of CO2 -- farm animals, concrete, eternalized CO2 production due to globalized manufacturing, etc.
tialaramex 5y ago
However, the UK has a lot of Combined Cycle gas turbines. Almost all of them in fact. CCGT is more efficient but not so much in the spin-up/ spin-down phase. I suspect that it's much cheaper to spin a CCGT down to idle power output for a while than switch it off and soon after back on again. Which is fine so long as the difference between idle power and peak power needed in the UK matches the range of our CCGTs. A ramp of 5GW output, over two hours is something they're doing every day. But what if it was 10GW in thirty minutes? 15GW in twenty minutes? Something has to give. You can definitely see in the data on a night with strong winds, it isn't the CCGTs that stop first. As winds pick up, the CCGTs reduce power output, but at a low point they continue where they are and the UK stops importing power instead. To a considerable extent that's cheap French nuclear power, which means low carbon. There is no way gas is cheaper than that. I'd guess the CCGTs would rather lose money for an hour (or two?) selling electricity for less than the gas cost to make it, than switch off and start again cold in a few hours.
- liketochill 5y ago
  There can be other system operation concerns such as stability and spinning reserve. If the intertie to France is lost and 3GW of nuclear power disappears and you are left with 100% wind then the severed system probably will be out of balance without something ready to go that can quickly. Also yes stopping and starting the machines are often when things go wrong. Things that are stopped tend to stay stopped and things that are running tend to stay running. Keeping a machine hot and spinning avoids thermal cycles and issues with stopping and starting oil pumps, brakes, bearings, etc that can occur.
- Retric 5y ago
  That’s a very good point. Modern CCGT’s can ramp down to 20% without causing thermal cycling issues. As you point out that’s not zero, but you can very accurately forecast wind over the next 12 hours to only turn on an appropriate number of CCGT’s. Traditional gas’s turbines cost less and turn on and off in minutes and are therefore ideal in more supplemental role. Some designs can actually operate aim either mode, which seems to cover the downsides of each system though of course at higher costs and slightly lower efficiency. The market isn’t infinitely adaptable, especially in low population areas, but margins end up surprisingly consistent.

marcosdumay 5y ago

The main impact should be quite obvious, as CO2 is the one that accumulates. But even if you decide to ignore it, it's not clear if natural gas extraction leaks more or less methane than coal, but whatever way the scales goes, the difference isn't very large.