Roadmap for a 100% Green Hydrogen US Energy Economy

The solution to global warming is fundamentally a technical problem, and according to the Intergovernmental Panel on Climate Change (IPCC), delay of solutions carries extra cost to human life, property, and ecosystems. An important question is whether existing technologies are adequate and whether they can be implemented in time to meet the most recent goal of the IPCC for the world to achieve net zero carbon emissions by 2050, which requires the so-called green energy transition.

As with most technical problems, engineers can take a systems-wide approach to arrive at the most preferred solution and apply it to the green energy transition. In this article we present a roadmap for one such solution for the USA, a green hydrogen energy economy in which solar photovoltaic (PV) and wind turbine (WT) farms provide all the required energy in the form of electricity, using hydrogen as a transmission and storage medium, and using only current technologies. The roadmap here provides a path with timing to get us to net zero by 2050, a process we call, The Build.  Since the technologies are current, we can start The Build right now, without any need for extensive research and development. All the essential technical details of this hydrogen economy are presented in the reference at the end of this article.  

The default scenario in that reference assumes an equal mix of end use energy demand for PV and WT, where WT demand is further split 50/50 between onshore WTon and offshore WToff farms. Although numerous other apportionments of demand among PV, WTon, and WToff are considered in the reference and can be incorporated into the roadmap, we use the results of that default scenario only to illustrate the approach. The minute details of the roadmap are to be decided by the central planning authority suggested below.

Additional technologies in the default scenario are utility grade stationary alkaline liquid electrolyte electrolyzers and alkaline liquid electrolyte fuel cells (UFC). The UFC are powered by electrolytic hydrogen and oxygen. Transportation is powered by electric motors and hydrogen fuel cells (FCEV) with polymer exchange membrane (PEM) technology, but the roadmap here can be easily adjusted for Li-ion vehicle batteries (BEV), and calculated examples for this are provided in the reference.

Green energy storage is an essential feature of the roadmap, for both electric and thermal energy needs. This storage incorporates high pressure vessels for hydrogen gas at 700 bar and oxygen at 340 bar, though other pressures are possible. In the default scenario, the stored oxygen is required only for the UFC, not for hydrogen thermal demands. However, additional oxygen can also be stored, if decided. The pressure vessels chosen are 20-inch outside diameter and 12 feet long and are stored upright in 8-foot-deep ground pits in open air, 1,000 by 1,000 ft² footprint, with about 350 such sites required for the nation in the default case. As explained in the reference, other pit sizes and numbers can be accommodated, depending on the best strategic deployment in relation to green energy farms and usage. These pits provide both daily storage to accommodate the day/night cycle for PV and the long duration storage (LDS) that provides for stochastic weather variability, with the latter storage amount equal to the average national energy generation for one-fourth the nation over four days, or the entire nation for one day.

As explained in the reference, seasonal energy storage is not necessary because the green energy farms are 20% oversized, so that on average, sufficient generation is accomplished for the low season. Stochastic deviations from this arrangement are accommodated by LDS. The 20% increase should be sufficient when PV and WT farms are balanced ~50/50 to accommodate demand, as in the default scenario, relying on the complementary nature of PV and WT. For other scenarios, either larger amounts of LDS or more than 20% extra generation may be required for certain regions. The excess generation during the high season will ensure that all storage is topped off, and it also enables revenue from the sales of hydrogen and other energy products produced by US renewable energy.

An enhanced electric grid provides for the increased capacity necessary because of electrification, and a hydrogen pipeline with associated compressors provides transmission and distribution of compressed hydrogen gas. Details are given in the reference.

For the default scenario, the total installation costs are $27.8 trillion, and we have 26 years for The Build, to 2050. This is an approximate mid-range estimate, and in the reference, lesser and greater amounts are calculated for other scenarios, as decided by a central authority, as suggested below.

The price tag may appear large to some, but there are no cheaper alternatives. The total energy generation considered in the reference is 96% of all current US energy supply, totaling all current all sources: fossil fuels, nuclear, hydro, and sustainable. What current technology other than PV and Wind can we use for this need? The only alternative is current nuclear fission. Proponents of nuclear fission energy point out its high capacity factors and the fact that it is constant, not intermittent, and that it has no requirements for energy storage. However, if we assume nuclear to be, for instance, the sole energy generator, it must also satisfy both electric and thermal energy needs. For the latter, the best way to do that is by converting its excess electric energy to hydrogen, which would be consumed for thermal purposes in steady state fashion via pipeline, with minor amounts stored for industrial use. This would be the ideal and least expensive use of current nuclear technology.

Thus, the only alternative to the roadmap here is one that uses nuclear energy for generation and also incorporates hydrogen for thermal loads. A question then is, how much would a hydrogen energy economy cost to build if all the energy were supplied by nuclear fission energy? Using the model for thermal energy use in the reference, with a nuclear capacity factor of 0.93 and with no expense/construction due to hydrogen storage, the total cost would be about the same $28 trillion if installation cost for new nuclear plants is 7.8 $/W. The latter figure is about the minimum current cost estimate for new nuclear plants in the USA. A maximum estimate is given by the newly completed Vogtl Units #3 and #4 by Georgia Electric, amounting upwards to 16 $/W.

In other words, solar and wind energies offer the minimum installation costs for an energy infrastructure that will get us to net zero by 2050.  Concerning operational costs, nature doesn’t charge us for solar and wind energy. Thus, operational costs for nuclear would be many times larger than that for the scenario here, for which there is no rational alternative.

The simplest way to illustrate The Build is with an approximate linear path of monetary expenditure, guided by the average annual allocations given in the Table shown. Complete calculations for these sums are provided in the reference. The costs for the first three items in that table are CapEx costs, and for the remainder, direct cost estimates (materials plus labor) for installation.

Table. Major components of a US green hydrogen energy economy and their Installation costs.
Component	Total, trillion $	Annual, billion $
PV + WT Farms	14.6	563
Electrolyzer	4.50	173
Utility Fuel Cell	0.81	31
New Gridline	3.13	120
Pit Storage of H2	3.10	119
H2 Pipeline	1.03	39
Pit Storage of O2	0.62	24
Total	27.8	1,070

Some secondary costs are not included in the table, such as fixed costs for operation and maintenance expenses (FOME). Since solar and wind energies are free, the levelized cost of energy (LCOE) is primarily due to installation costs plus investment costs (discount rate). Other costs not in this road map are the costs to consumers for electrification and for sustainable transportation vehicles.

In the initial years, all but about 4% of the nation’s annual energy needs, both electric and thermal, is targeted in the roadmap, using mature technologies. There aren’t mature technologies yet for that 4%, and the Table does not contain costs for these technologies. Such technologies include aviation, which is most of that 4% energy need, and when the aviation industry in future decades achieves sustainable operation with hydrogen and sustainable liquid hydrocarbon fuels made from hydrogen, about 99% of the entire energy requirements will be included. Finally, as the production of asphalt, plastics, and chemicals adapt to the use of hydrogen and electricity through to 2050, 100% of all the nation’s energy requirement will be accounted for.

The roadmap’s annual expenditures in the Table are thus approximate and additional roadmap costs due to such refinements will become obvious as we walk the path to 2050.

The major steps in the roadmap are three:

1) Phase out subsidies to fossil fuels.

2) Phase in carbon taxes to align the price of fossil fuels with their true societal cost, with provisions to relieve lower income people of the resulting higher energy costs.

3) Phase in increasing levels of energy conservation and improved process efficiencies.

4) Build the major components of the hydrogen infrastructure in a balanced and roughly linear way through to 2050. The major components are given in the Table, along with the approximate yearly expenditures for each component. The linear path is only a suggestion, with deviations as The Build progresses, as the 4% of energy not initially included becomes incorporated, as technologies are improved, and as the value of the dollar and other economic/financing aspects adjust to the passing years. The dollar amounts in the Table do not account for energy conservation and enhanced energy efficiency, which the nation will increasingly undertake, and which will significantly help reduce costs.

Steps 1 and 2 are mandatory, to provide the most favorable investment atmosphere that will accelerate the speed of The Build. Step 3 will result in an appreciable reduction in the annual cost of The Build.

In Step 4, “balanced” means that all components are utilized immediately after their build, having the rest of the system built up to their approximate level, without many newly constructed components being idle after commissioning. We must accept the fact that much of the energy required to build the infrastructure will come from fossil fuels, especially in the initial years. We assume that there will be gradual transfer of such energies from conventional to green as The Build unfolds, according to decisions made by competent governing agencies, as suggested below.

Competent governing agencies must manage the roadmap, to mastermind the projects and their legal aspects, interface with citizens and public opinion, allocate funds for construction and labor, make purchases, operate some of the facilities, provide seed money, devise tax incentives, and invite industry and private investors. Incentive for the latter are the profits and financial gains to be made by getting in on the ground floor of building/investing in the new energy infrastructure. The endeavor is a united effort by the whole of American society.

The required agencies can be modelled after those who took charge during the build of the war effort in WWII, in which then-existing technologies were incorporated at an astonishing rate into a formidable war machine. In the entire war period of just a few years, the government spent about twice the then-average annual gross domestic product, and they spent all that money in less than a quarter of the time we have now. By today’s standards, that’s about $50 trillion, approaching twice what we are required to spend now on the utility infrastructure.

A current agency that might serve as a model for the top mastermind of all agencies is the US Defense Advanced Research Agency, or DARPA. In fact, judging by DARPA’s self-image as a national security provider, this agency might be a prime candidate to manage The Build: https://www.youtube.com/watch?v=IcV4pgB5QY0&t=37s.

For The Build, the annual disbursement shown in the Table amounts to only about two-thirds of the true, complete current annual cost to taxpayers for all US government agencies devoted to national security. The current budgeted amount of $840 billion for the military is only part of the cost for national security. There is additional military-related cost that is outside this budgeted amount, including that for veteran’s affairs, pension payments to military retirees and widows and their families, interest on debt incurred in past wars, State Department financing of foreign arms sales, military-related development assistance, and nuclear weapons research, maintenance, cleanup, and production. Additional also is defense spending that is domestic rather than international in nature, such as the Department of Homeland Security, counter-terrorism spending by the Federal Bureau of Investigation, and intelligence gathering by the National Security Agency and the Central Intelligence Agency, although these programs contain certain weapons, military, and security components. An investigation by the author on most of these costs in many references suggest that the total annual bill for all national security activity is close to twice the so-called military budget just mentioned, say $1.6 trillion per year.

Except for a shrinking minority, US citizens would agree that we are now in a crisis of national security.

Before this build, current technologies such as automobiles, computers, etc. have evolved through the decades, filtered by performance in the marketplace. This marketplace approach played a small role during the war years, and it should not determine our pace now because those developments took decades. We are already out of time, considering that human death and loss of irreplaceable ecosystems are now occurring. With an independent agency such as DARPA deciding the details of The Build, we are not delayed by efforts to find the least expensive, most efficient, best, and most competitive technical solutions for every necessary item of technology that would win out in a marketplace after some time. As we get to 2050 and years beyond, better suited technologies will displace some of the ones incorporated at the early stages of The Build, and we can gradually get back to business as usual.

During WWII, the nation experienced the so-called “war time economy,” then settled back to normal, and perhaps this period of a “build time economy” will be memorable to future generations.

Noting the dollar amounts of the annual expenditures in the Table, there may be enough private funds available for the less costly of the infrastructure components, and it may be possible for government to provide only seed monies and tax incentives for some of the other more costly components. However, a question of ownership arises if government funds large amounts for PV and WT farms and electrolyzer plants that private industry cannot finance. Here, the government should form an entity akin to the US Army Corps of Engineers, – or DARPA itself – that owns and operates such facilities, at least for a time, after which assets can be sold at favorable prices to private interests.

Determining such financing strategies are of the highest priority today, during the early years of The Build. So too are the legal processes necessary to obtain rights of way, land procurement, and other activities involving private property. Existing rights of ways of fossil fuel supply lines will be a valuable component of The Build.

With such a clear plan and with such a centralized organizer, private companies will have more incentive to invest in The Build. The confidence derived from being part of a major and focused push is invaluable.

Also important is the expected opposition many citizens will present to such an enormous undertaking. As the damage encountered by climate change mount, such opposition will lessen, and it’s unknown how the necessary rate of The Build and the changing rate of citizen approval will interact. We can only hope that the additional damage resulting from the delays caused by such opposition can be minimized.

In short, The Build is an unprecedented peace time event in our modern society, and for it we need alter our current priorities within our energy economy and of the energy economy itself. At the same time, however, we have met such challenges before.

In reference to the electric portion of total energy burden of the nation, Step 4 requires that consumers implement heat pumps and electric resistance heaters for space heating/cooling/cooking and electric cars for transportation. This is what is meant by “Electrification.” The cars will be initially mostly battery vehicles (BEV), but a national hydrogen filling-station network must be built early to accommodate hydrogen fuel cell vehicles (FCV) so they can compete fairly in the marketplace with BEV. The transition to electric vehicles must conform to the “balance” described in Step 4. Regulation of the rate of construction of electric and hydrogen filling stations is one way to ensure that balance.

In reference to the thermal portion of total energy needs, Step 4 involves primarily the industrial sector, because the thermal energy required by the residential and commercial sectors is mainly for space heating and cooking, which have been electrified.

Industrial thermal consists of fuel use and non-fuel use. By far, the larger portion is for fuel use (called combustion, or “high temperature processes”). Industrial fuel use will gradually transform to hydrogen combustion, either directly or indirectly, with sometimes the help of electricity. We assume at the outset that this can be done for virtually all fuel-use processes, but there will be adjustments that require innovation through the decades. Valuable here is government support for short term and well-defined R&D projects and seed money. DARPA has a good track record in such activities.

The non-fuel processes in making liquid steel and ammonia are the largest energy demands for the non-fuel category.  Liquid steel production is readily adaptable to hydrogen in a process called direct reduction, and there are plants that have achieved this goal, even in the current, unfairly competitive fossil fuel environment (e.g., the SSAB, LKAB and Vattenfall Hybrit project in Sweden). The making of ammonia from hydrogen and electricity is already an established technology, and the electricity is mostly for the liquefaction of air to generate nitrogen, a necessary ingredient of ammonia (NH3). Much of the ammonia is used to make fertilizers, and it’s useful in many other processes, including energy transport in pipelines. Costs of steel and ammonia production are included in the Table. So too are costs including all current production of hydrogen from fossil fuels.

Cement production requires minuscule energy compared to the nation’s total requirement, but generates disproportionate amounts of CO2, and this technology is not currently adaptable to hydrogen. Through the decades, innovation will provide increasingly effective ways to render cement production sustainable, producing negligible CO2 emissions. We need also consider that the resulting CO2 can be captured and combined with hydrogen to make methane, a useful carbon source.

The only significant energy demand left is for aviation, and virtually all that is for jet fuel – about 3% the total national energy burden – and industrial nonfuel processes for the making of asphalt, plastics, and chemicals – about another 1%. Before 2050, aviation will most likely convert to either hydrogen directly or to sustainable liquid hydrocarbon fuels made from hydrogen and methane. Methane can be made from hydrogen and CO2, with the latter obtained from direct air capture (DAC) and cement making, as mentioned previously. The DAC process is powered by green electricity. There may be contributions here from biofuels if they are competitive. The fate of asphalt, plastics, and chemicals production should eventually be like that for jet fuel.

The above is a complete roadmap to net zero by 2050, when combined with the infrastructure described in the reference. The author is aware that there are many other roadmap suggestions for the green energy transition. The author, however, is not aware of any other that is described in less than hundreds of pages, that explicitly lists all the separate and necessary infrastructure components – including 100% hydrogen storage – and that provides clarity on how to pace The Build. An agency such as DARPA can assemble the required team of scientists, engineers, economists, accountants, financiers, sociologists, psychologists, etc. That capability inherently depends on the simple, straightforward picture of what the green hydrogen energy economy could look like. The reference provides such a picture. Missing only is the funding and the command to build, and more important than anything else is the will to make it happen.

There are still many unknowns, for instance the effects of climate change on the PV and WT potentials for the nation, and no doubt DARPA engineers will fill in the blanks and find many ways to improve on this roadmap, which is a proposal to serve only as a guide to help government make the decisions most of us want it to make, are waiting for it to make, are hoping it will make, and will soon perhaps demand that it make. 

Reference: Thomas Tonon, “What would a US green hydrogen energy economy look like?”, Clean Energy, Volume 7, Issue 5, October 2023, Pages 1148–1172, https://doi.org/10.1093/ce/zkad047