Natural gas is a fuel of the future, Austin Vernon explains:
Gas power plants are cheap.
Why are gas plants so cheap? They have less equipment. A gas turbine takes in compressed gas and air, burns it, spits out the exhaust, and turns a generator. Modern turbines are as efficient as coal or nuclear plants and a fraction of the size of hulking steam turbines. They are 3x as efficient as the average geothermal facility.
Coal, nuclear, and geothermal plants utilize more complex thermodynamic cycles. They have a boiler, a steam turbine, a generator, a condenser, a boiler feed water pump, more cooling towers, and a water purification system for boiler feed water. Coal plants contend with solids handling, and nuclear plants have complex reactors.
Combined cycle natural gas power plants use hot exhaust from the turbine to make steam like traditional thermal plants. About 2/3 of plant output comes from the gas turbine and 1/3 from the steam turbine. Total efficiency can be over 60% with less equipment and labor than boiler-style thermal plants.
Cheap Storage
Most natural gas storage is in depleted reservoirs. They fill up in the summer when gas demand is low and empty in the winter when gas demand is high.
Building a depleted reservoir gas storage facility costs about $6 million per billion cubic feet of gas. That equates to $0.02/kWh. A grid storage lithium-ion battery currently costs $250-$300/kWh.
The marginal cost of storing gas is determined by renting space in the storage facility and compressing it into the reservoir, usually ~$0.50/MCF for a season. Spot natural gas prices have been between $1.50 and $6 over the last decade. Efficiency determines the marginal cycle cost for a battery. Most lithium-ion battery systems are 90%+ efficient. Tesla’s Powerwall has a 92.5% round trip efficiency.
Reservoir permeability limits gas injection/discharge rates to emptying once per season. Salt dome storage facilities are an exception that can cycle faster but have higher construction costs. Batteries can cycle within a few hours.
Batteries have an advantage in short-term storage, while natural gas storage is much better for long-duration storage.
Hydrogen
Why not store hydrogen instead of natural gas?
Hydrogen embrittles metal that pipelines and storage facility wells are made of, limiting usage in existing infrastructure.
Methane (the primary molecule in natural gas) has three times the energy per volume as hydrogen. A switch to hydrogen would mean we’d need three times more pipeline, compressor, and gas storage capacity.
Hydrogen is more expensive to store because of poor volumetric energy density, and it needs all new infrastructure. If we see widespread hydrogen storage, it will likely be local and only for industrial and electricity use. Building new interstate pipelines is increasingly difficult. As we’ve seen with electricity transmission, critics do not make an exception for “green” projects. I will remain skeptical.
Better Than Air
Compressed air storage also uses caverns and reservoirs as cheap, long-term storage. Compressed methane is ~80x more energy-dense than compressed air. Facilities need new turbines and grid connections, unlike natural gas.
Ammonia
Ammonia is easy to liquefy, so it has good volumetric energy density. Proponents favor applications like marine fuel and gas turbines.
The downsides are that it is poisonous, burns slow, releases tons of NOx when burned, and is less dense than regular ship fuel. The toxic aspect eliminates its use in residential applications. The combustion characteristics mean turbines need larger combustion chambers and more emissions control than natural gas turbines. And the lower volumetric density means it is vulnerable to drop-in synthetic liquid fuels in maritime applications.
Pumped Hydro and Other Cats and Dogs
Pumped hydro costs a thousand times more per unit of energy than natural gas storage. All the other random pet technologies are expensive, too. Storing energy in hydrocarbons is laughably cheap. Competing technologies tend to be awkward tweeners. They can’t compete against batteries in short-term storage or against gas in longer-duration storage.
Terraform Industries (@Terraformindies) makes natural gas from CO2. It would be a lot more sensible to have their stuff attached to smokestacks on power plants and factories than just using scrubbers.
Burn natural gas — it releases energy and produces mainly water vapor and life-giving carbon dioxide.
Looks like Terraform Industries plan is to extract energy from sunlight using massive areas of expensive solar panels (imported from places where the authorities have no compunction about using slave labor and no concern about the environmental impacts of mining & manufacturing exotic materials) to generate electricity so they can reverse the oxidation process and make methane from low concentrations of CO2 and scarce water.
Technically, it can be done — has already been done. Environmentally, it is probably worse than drilling gas wells. Economically, it is a non-starter. But hey! “It’s Green”.
“Combined cycle natural gas power plants use hot exhaust from the turbine to make steam like traditional thermal plants. About 2/3 of plant output comes from the gas turbine and 1/3 from the steam turbine. Total efficiency can be over 60% with less equipment and labor than boiler-style thermal plants.”
This is obviously a lie. One cannot utilize mechanical processes A and B, and have the total be less complex than process B alone. If it has a boiler, then it has a boiler. It cannot also not have a boiler.
Gavin, I think we’d both rather @terraformindies used nuclear power, but there’s a lot to be said for just releasing water vapor from your smokestack like a nuclear plant’s towers. Heck, water is useful stuff too.