What I call the “energy storage conundrum” is the obvious but largely unrecognized problem that electricity generated by intermittent renewables like wind and sun can’t keep an electrical grid operating without some method of storing energy to meet customer demand in times of low production. These times of low production from wind and sun occur regularly — for example, calm nights — and can persist for as long as a week or more in the case of heavily overcast and calm periods in the winter.
If the plan is to power the entire United States by wind and solar facilities, and if we assume that wind and solar facilities will be built sufficient to generate energy equal to usage over the course of a year, we then need to do a calculation of how much storage would be required to balance the times of excess production against those of insufficient production in order to get through the year without blackouts. The challenge of getting through an entire year could require far more storage than merely getting through a week-long wind/sun drought, because both wind and sun are seasonal, producing much more in some seasons than others.
Previous posts on this blog have cited to several competent calculations of the amount of storage needed for different jurisdictions to get through a full year with only wind and sun to generate the electricity. For the case of the entire United States, this post from January 2022 describes work of Ken Gregory, who calculates a storage requirement, based on the current level of electricity consumption, of approximately 250,000 GWH to get through a year. If you then assume as part of the decarbonization project the electrification of all currently non-electrified sectors of the economy (transportation, home heat, industry, agriculture, etc.), the storage requirement would approximately triple, to 750,000 GWH. If that storage requirement is to be met by batteries, and we price the amount of storage needed at the price of the best currently-available batteries (Tesla-type lithium ion batteries), we get an upfront capital cost in the range of hundreds of trillions of dollars. That cost alone would be a large multiple of the entire U.S. GDP, and obviously would render the entire decarbonization project impossible. In addition, lithium-ion type batteries (and all other currently-available batteries) do not have the ability to store power for months on end, as from the summer to the winter, without dissipation, and then discharge over the course of additional months. In other words, the fantasy of a fully wind/solar energy economy backed up only by batteries is doomed to quickly run into an impenetrable wall.
So is there another approach to decarbonization that could work? With nuclear blocked by the same environmentalists who oppose all use of fossil fuels, the options are few. The most plausible would be to use hydrogen as the means of storage to balance the random swings of wind and solar electricity generation.
It’s not like nobody has thought of this up to now. Indeed, to politicians and activists who can freely pontificate about theoretical solutions without having to worry about practical obstacles or costs, hydrogen seems like it couldn’t be easier. With hydrogen, you can just completely cut carbon out of the energy cycle: make the hydrogen from water, store it until you need it, and then when the need arises burn it to produce energy with only water as the by-product.
In his 2003 State of the Union Address, President Bush launched his Hydrogen Fuel Initiative. The goal of this initiative is to work in partnership with the private sector to accelerate the research and development required for a hydrogen economy. The President’s Hydrogen Fuel Initiative and the FreedomCAR Partnership are providing nearly $1.72 billion to develop hydrogen-powered fuel cells, hydrogen infrastructure technologies, and advanced automobile technologies. The President’s Initiative will enable the commercialization of fuel cell vehicles in the 2020 timeframe.
Fuel cell (that is, hydrogen-fueled) cars by 2020. Nothing to it!
Perhaps you haven’t noticed any large number of hydrogen-fueled cars on the roads here in 2022. How’s it going with the project to produce the hydrogen by a carbon-free process of electrolysis from water (sometimes known as “green hydrogen”)? This is from the JP Morgan Wealth Management 2022 Annual Energy Paper (page 39):
Current green hydrogen production is negligible. . . .
The solution seems so terribly obvious, and yet nobody is doing it. What is wrong with everybody?
The summary of the answer is that hydrogen in the form of a free gas is much more expensive to produce than good old natural gas (aka methane or CH4), and once you have it, it is inferior in every respect to natural gas as a fuel for running the energy system (other than the issue of carbon emissions, if you think those are a problem). Hydrogen is far more difficult and costly than natural gas to transport, to store and to handle. It is much more dangerous and subject to exploding. It is much less dense by volume, which makes it particularly less useful for transportation applications like cars and airplanes.
And of course there is no demonstration project at large scale to show how a hydrogen-based power system would work or how much it would cost after including all of the extras and current unknowns not just for producing it but also for transporting it and handling it safely.
Here are just a few of the issues that arise in consideration of hydrogen as the way to decarbonize:
- Cost of “green” hydrogen versus natural gas. In recent years, prior to the last few months, natural gas prices have ranged between about $2 and $6 per million BTUs in the U.S. The price spike of the past few months has taken the price of natural gas to about $9/MMBTUs. Meanwhile, according to this December 2020 piece at Seeking Alpha, the price for “green” hydrogen produced by electrolysis of water is in the range of $4 to $6 per kg, which translates, according to Seeking Alpha, to $32 to $48 per MMBTU. In other words, even with the very dramatic recent rise in the price of natural gas, it is still 3 to 5 times cheaper to obtain than “green” hydrogen. There are some who predict dramatic future price declines for “green” hydrogen, and also continued price increases for natural gas. Maybe. But with prices where they are now, or anywhere close, nobody is going to make major purchases of “green” hydrogen as the backup fuel for intermittent renewables; and without buyers, nobody will produce large amounts of the stuff.
- How much overbuild of sun/wind generation capacity would be required to produce the “green” hydrogen? Truly breathtaking amounts of incremental solar panels and/or wind turbines would be required to make enough “green” hydrogen to become a meaningful factor in backing up a grid mainly powered by the sun and wind. The Seeking Alpha piece has calculations of how much nameplate solar panel capacity it would take to produce enough “green” hydrogen to power just one small size (288 MW) GE turbine generator. The answer is, the solar nameplate capacity to do the job would be close to ten times the capacity of the plant that would use the hydrogen: “Consider the widely deployed GE 9F.04 gas turbine, which produces 288 MW of power. With 100% hydrogen fuel, GE states that this turbine would use about 9.3 million CF or 22,400 kg of hydrogen per hour. With an 80% efficient electrolysis energy cost of 49.3 kWh/kg, producing that one hour supply of hydrogen would require 1,104 MWh of power for electrolysis. To generate the hydrogen to run the turbine for 12 hours (~ dusk to dawn) would require 12 x 1,104 MWh, or 13.2 GWh. Given a typical 20% solar capacity factor, that would require about 2.6 GW of solar nameplate capacity dedicated to generating the hydrogen to fuel this 288 MW generator overnight.” Given the tremendous losses in the process of making the hydrogen and then converting it back into electricity, it is almost impossible to conceive that this process could ever be cost competitive with just burning natural gas.
- Making enough “green” hydrogen to power the country means electrolyzing the ocean. The ocean is effectively infinite as a source of water, but fresh water supplies are limited. If you electrolyze salt water, you get large amounts of highly toxic chlorine. There are people working on solutions to this gigantic problem, but as of now it is all in the laboratory stage. Incremental costs of getting your “green” hydrogen from the ocean are a complete wild card.
- Hydrogen is much less energy dense than gasoline by volume. For many purposes, and particularly for the purpose of transportation fuel, it is highly relevant that hydrogen is much less dense than gasoline by volume. Even liquid hydrogen has an energy density by volume that is only one-quarter that of gasoline (8 MJ/L versus 32 MJ/L), meaning that much larger a fuel tank; and liquid hydrogen needs to be kept at the ridiculously cold temperature of -253 deg C. Alternatively, you can compress the gas, but then you are talking more like a 10 times energy density disadvantage. Either compressing the gas or converting to liquid will require large amounts of additional energy, which is an additional cost not yet figured into the calculations.
- Hydrogen makes steel pipelines more brittle. Hydrogen is much more difficult than natural gas to transport and handle. Most existing gas pipelines are made of steel, and hydrogen has an effect on steel known as “embrittlement,” that makes the pipes develop cracks and leaks over time. Cracks and leaks can lead to explosions. Also, because of the volumetric energy density issue, existing natural gas pipelines can carry far less energy if used to carry hydrogen.
I don’t know how much extra our energy would cost if we forcibly got rid of all hydrocarbons and shifted to wind and solar backed up by “green” hydrogen — and neither does anybody else. An educated guess would be that the all-in cost of energy would get multiplied by something in the range of five to ten.