Coal, natural gas, and CO2

It has been argued that natural gas can be a “bridge” towards a carbon neutral energy strategy. With regards to coal fired power plants, how practical is it to convert them to natural gas which would cut CO2 emissions by roughly half, mostly eliminate sulfate and particulate emissions and have other benefits for the environment, health, and possibly other costs associated with coal related activity.

First of all, natural gas must be available @ the powerhouse.

The other retrofit considerations are many and varied, there isn’t one simple answer to your question.

Generally speaking, natural gas retrofitting is a viable alternative, depending on supply availability, and overall age of the powerplant. Some coal plants are simply too old and decrepit to justify retrofitting with a new fuel. In other words, there a lot of old coal powerhouses that are on the verge of shutdown due to general wear… new fuel retros are beyond financial feasibility.

It’s being and been done at some plants, so obviously in those cases it was practical. What percentage of the total that is, though, I don’t know.

I don’t know how many coal plants have been converted, either, but coal use has been declining while gas-fired plants have been on the rise, and gas was projected to overtake coal as the predominant fuel for power generation in either 2015 or 2016, depending on your source.

It’s a reasonable interim strategy because from an overall environmental standpoint it’s hard to imagine a worse source of energy than coal. Ontario has converted or demolished all of its coal-fired plants, sometimes in spectacular fashion.

Nzatural gas power plants, like coal, have the advantage that they can be quickly turned on or off, as the electricity demand changes. Renewable energy sources, like hydro power, solar, or windmills, all run mostly continuously, on the schedule of their source (the water, sunlight, or wind) and so are independent of the demand for electricity. So when that goes up, additional power from coal or natural gas plants can quickly be fired up to meet the demand. A big value to a power system.

At this time, and for the foreseeable future, natural gas is the most economic fuel from a btu to k-watt conversion factor, not to mention the advantage from an EPA emission regulation viewpoint.
New powerhouses tend to be constructed for natural gas as the primary fuel… Notwithstanding local political interventions.:smack:
In my part of the world, “Coal is King”, and won’t go down without a fight.

Actually, hydro-electric plants can be designed to increase capacity very quickly:
Because hydropower is a constant, permanently available energy source, it guarantees reliable supply. Thanks to its storage capacities, a reservoir generating station can provide an instant response to changes in demand. At peak periods, hydropower generation can be adjusted almost in real time. In comparison, it can take 12 hours or so to start up a coal-fired power plant.

And wind power variations can be partially mitigated through geographically dispersed wind farms. But yes, given some of the response limitations of some power sources, including nuclear, there’s been a growing trend toward smaller regional gas-fired peak power generators to deal with peak demand issues.

Sure… As long there is enough available head to drive the turbine, all things considered such as: minimal Corps of Engineers channel depth, irrigation demands, etc. It’s not as simple as it sounds.

Actually, it takes much longer to start up a large coal (or other) fired boiler/turbine powerhouse from cold, unless you want to “slam” the equipment (power generation corporations are loathe to do this).

Yes, but most of the good sites have already been dammed, and climate change could threaten the output of some, especially on the Colorado River. Some experts fear that Lake Powell could be at dead pool in a few years, and Lake Mead has been dropping for years, though it got a brief reprieve in 2017

Climate change threatens all kinds of things that are precipitation dependent because it can change precipitation patterns, but on average it will likely increase overall precipitation because the atmosphere will be carrying more moisture, so in general it should be good for hydro power. And indeed, this has been happening.

Problem solved.

I’m not sure what all the snark is about. With regard to #8, I didn’t claim that anything was “simple”. I was quoting one of the world’s largest hydroelectric producers saying that they routinely respond very rapidly to changes in demand, contradicting the claim that hydroelectric power can’t do this. With regard to the snark in #11, the factually correct statement is that climate change will generally be producing more precipitation overall, on average likely creating more energy potential in many, though not all, hydroelectric reservoirs.

I simply stated hydro response to instantaneous load change is not a panacea for this problem, and their response could be problematic depending on circumstances.

This is your assumption… I’m sorry if my comments cast doubt upon the wide spread efficacy of your notions. However, I do apologize if my comments appear as snarky. It was not meant as such, I assure you.

I simply don’t take what you state as an indisputable fact; as the end all, be all, FINAL WORD… OK?

I have trouble linking to search results that are direct-to-pdf, but in Google the first result for this search:
coal to natural gas conversion
may be of interest to the OP.

Coal to natural gas (and other components), while technically feasible is at this time, is a net energy loser…


My post was simply in response to the implication that hydroelectric sources may be drying up. That may well be in some areas, because some areas are indeed experiencing sustained drought. I simply stated that theory suggests increasing precipitation as climate change progresses due to increasing atmospheric moisture capacity, which is a fact. I then showed that increasing precipitation is actually occurring in one of the world’s prime hydroelectric generating areas.

That’s it. No more, no less. Not sure what offended you or gave the impression of some kind of “final word” being proclaimed. There is no “final word” on extremely complex issues. It just seems likely that as climate change intensifies, on balance there will be increased mass of moisture transport to upstream reservoirs in the global hydrological system, though it certainly won’t be the same everywhere.

Coal power stations, are notoriously slow to ramp up or down in power production. The power input to the system has to be changed - which means changing the rate of burning coal of gas, and this change has to propagate right through the furnaces and boilers. Nuclear is if anything worse.

I suspect there is a misunderstanding about the different roles required on a power grid are. Big traditional power stations provide stabilisation of the grid as they have large massive rotating components that can ride out sudden changes in demand in power on the grid. For obvious reasons this capability is usually called “inertia” in power supply. Your grid needs a certain amount of inertia to stay stable. Such inertia only rides out short transients (seconds) in power demand, but is critical.

Once you have ridden out the transient spikes, you do need generator capacity that can roll up and down with demand over the short term. Although some reserve is probably available in in the boilers, it isn’t going to be much use beyond a short change in demand. Changes in demand must be managed in both directions, it is just as bad to have overproduction as underproduction of power.

Hydro provides inertia, and can react quite quickly to demand changes. Much faster than coal.

Beyond this you need may need to bring new power generation on stream. Spinning up a steam turbine can’t be done instantly. A common fast reaction generator is a gas turbine - basically a jet engine connected to a generator. This can come on stream quite quickly. A combined cycle gas turbine (where you recover heat from the jet engine’s exhaust to power another turbine) can be as efficient as you anything you can build. They can run on most things, but running them on natural gas is a big thing.

The new big thing is synthetic inertia - where you directly control the frequency of inverters rather than slave yourself to the grid. This requires a much more complex control system, but means you can get the effect of large rotating masses (ie generators) with a battery or other power source (including solar and wind.)

Here in south Oz our shiny new Tesla 100MWh battery stepped in to control the frequency of the national grid when a coal fired generator tripped out a week ago.

This new world of synthetic inertia and frequency stabilisation is almost certainly going to undercut the traditional power generators market for stability. Indeed one of the most vocal complaints about renewables has been its lack of ability to provide “base load” (which is exactly the wrong term, but is the one that has stuck. Base load is actually the need to provide a minimum load on the grid to soak up the power generated by coal and nuclear because it is so hard to vary the power output of these systems - so you end up with cheap overnight power - because it is easier to sell the power cheap than to wind down the coal fired power stations.)

Another interesting technology that was being field trialled in California is adding controlled frequency inverters to every wind* power generator and having them all coordinated to provide frequency stability. Which is a direct switch from when they slaved to the grid and provided zero stability.

*I think wind, might be solar.

In the end power generation from hydrocarbons like coal and natural gas is just different ways to boil water. For a power plant you can leave the generators and turbines and boilers in place. Whether swapping the coal furnace for a gas furnace makes sense or is even feasible is something for the bean counters to figure out. Doubtless there are many factors impacting the decision.

The implication is that generally speaking, some hydro sources are drying up, yes? (And hard to control, hydrologically speaking).

Which “one” area are you referring to?

No offence taken here. Just confused as to your notions as to where these changes will take place.

While the total energy available to a hydro plant over the course of a year is slave to the vagaries of climate, and cannot be sustainably increased beyond the yearly rainfall level, they have a tremendous degree of control over when that energy is released. Hydro really is the best power source in nearly every figure of merit imaginable: It’s also very cheap, and one of the most environmentally friendly. Its only major downside is that it’s very close to saturated already: Every place where it makes sense to build a dam already has one.