Energy Shapeshifting with Hydrogen

Day operation HyERA™ example system model: renewable power is greater than demand yielding hydrogen production and storage

A recurring question when it comes to hydrogen is whether it is an energy carrier, an energy storage method, or a fuel. The answer is yes. This versatility is why hydrogen represents a key solution to mitigating climate change across virtually all industry sectors.

No carbon emissions. No harmful environmental impacts. No strategic materials supply chain issues. No disposal or recycling challenges. And with a system lifetime measured in many decades with routine maintenance and no significant replacement costs.

There is another truly unique capability of hydrogen systems that is often overlooked: the capability to produce large quantities of potable water. But first, let's start with its role as an energy carrier.

Energy Carrier

An energy carrier is a fuel or system that enables the conversion of potential energy to other forms of energy (e.g. mechanical, thermal, chemical, or electrical). The conversion process can be shifted in time, location, or both relative to when and where the potential energy was originally created.

A common and currently ubiquitous example is natural gas. Produced by decaying organic material, it has intrinsic potential energy in the form of its heat value (a measure of energy density). It can be delivered as a gas in pipelines, or liquefied for transport. Unfortunately, natural gas is a significant source of greenhouse gas emissions via leaks and combustion emissions.

Hydrogen has all the energy carrier characteristics of natural gas without the greenhouse gas or other environmental impacts. It can be similarly delivered as gas, or liquefied for transport. Its heat value is more than double that of natural gas or any other fossil fuel. Further, the energy conversion efficiency when hydrogen is consumed in a fuel cell is much higher than any combustion process.

Energy Storage

Energy storage methods retain energy from a power source and store it for later use. This capability is particularly critical for balancing electrical demand in grids or microgrids that rely wholly or in part on intermittent renewable power sources (e.g. solar or wind).

Commonly used forms of energy storage include hydroelectric (i.e. "hydro") for large scale storage, and lithium-ion batteries for small to moderate energy storage. For grid-scale energy storage where the local terrain doesn't support hydro - which is most locations - there are few feasible options and even fewer proven systems. Lifecycle battery costs at this scale become untenable.

Overgeneration from renewables that is currently curtailed when insufficient demand exists can be used to electrolyze water into hydrogen and oxygen. The hydrogen is then stored until demand exceeds renewables capacity, at which point it is fed to fuel cells to generate the additional electricity needed.

Hydrogen energy storage is rapidly being recognized as a frontrunner solution for large scale applications where it has already been deployed in many locations. And more capacity is coming online at an accelerated rate. 

Universal Fuel

As previously mentioned, hydrogen has more than double the energy density of any fossil fuel option. It has been successfully demonstrated in nearly every combustion process imaginable, from internal combustion engines to turbines. Adjustment of the oxygen-fuel ratio is the primary modification required.

Ground, sea, and air demonstration vehicles using hydrogen have already been fielded with many more under development. These applications particularly benefit from the increased energy density of hydrogen relative to legacy fuels. And of course, carbon emissions are eliminated.

Over the last few years, introduction of a low percentage of hydrogen into natural gas pipeline networks has been tested in several global regions with promising results. Modification to residential and industrial burners will be required to increase the hydrogen percentage to more than 10%.

In short, there are no current fossil fuel applications that cannot be transitioned to hydrogen. Additionally, the higher flame temperatures that can be achieved with hydrogen will enable new applications and potentially enhance the efficiency of existing combustion-based systems.

Potable Water

The fact that hydrogen can be produced from water using renewable energy sources, and then returned to water form during usage, is generally well known. But many other feedstocks can be used to produce hydrogen. And when the hydrogen is used, potable water can be extracted in significant quantities.

Two of the more intriguing feedstock options are seawater and biomass waste. A hydrogen electrolysis plant located near a coast or on an island could desalinate seawater and produce hydrogen for energy storage, fueling, and/or export.

Likewise, dual production of potable water and hydrogen can be realized with agricultural waste and other recycled biomass as feedstock. In this case, potable water and hydrogen can be generated where little or no water is available.

The implications for drought stricken regions is immense, particularly where renewable resources such as solar are available in abundance. Secure and reliable energy, water, and food becomes possible in regions that are vulnerable to weather or other threats to these vital necessities.

Hydrogen has the potential to address all of the above. And in the process, restore the health and stability of our global environment for future generations.

Night operation HyERA™ example system model: renewable power is less than demand requiring hydrogen usage and producing potable water

Matt Moran is the Managing Member at Moran Innovation LLC, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems for more than 40 years; and first-of-a-kind liquid, slush and gaseous hydrogen systems since the mid-1980s. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been a cofounder in seven technology based start-ups; and provided R&D and engineering support to hundreds of organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management report series. More about him can be found here.

The Nuclear Option for Hydrogen

Illustration of a conceptual spacecraft enabled by nuclear thermal propulsion (Credits: NASA)

This week I attended the Nuclear and Emerging Technologies for Space (NETS) conference. It was a bit of nostalgia for me since I worked briefly on the NASA-led SP-100 program in the mid-1980s. The SP-100 was meant to demonstrate a nuclear fission reactor that could provide 100 kW of electrical power to a spacecraft. It was cancelled before flight hardware was built, in part due to public resistance about launching a nuclear reactor.

Later on at NASA I also worked on the solar dynamic Brayton power system originally planned for the space station; and Stirling microsystems development for multiple applications. Both technologies convert heat to electricity and can use radioisotope or fusion reactor heat sources. Later still, I briefly supported the Jupiter Icy Moon Orbiter program that was slated to use a small nuclear fission reactor for propulsion and power. 

None of these systems have flown on any spacecraft. But there is reinvigorated interest in nuclear fission based power and propulsion to expand the capabilities and performance of scientific and human exploration space missions. 

So why write about all this in a blog devoted to hydrogen? Because nuclear fission reactors have significant potential implications for hydrogen systems in space as well as on the ground in the energy sector. First, a very quick summary of the primary types of space-based nuclear power and propulsion technologies. 

RTGs, NTPs, NEPs, and Fission Surface Power for Space Missions

Radioisotope thermoelectric generators (RTGs) convert the thermal energy from a decaying radioisotope source to electrical energy using an array of thermocouple junctions. There is no nuclear fission involved. RTGs have been used on more than two dozen spacecraft over the past 60 years and enable very long mission durations far from the sun.

The thermocouple junctions in an RTG can be replaced by a Stirling engine for much higher efficiency and higher associated electrical power output. Heat drives the Stirling cycle via a working gas (e.g. helium) resulting in pressure-volume mechanical power that is converted to electricity. Stirling technology is at a high readiness level and will likely start replacing RTGs on some future missions.

Nuclear thermal propulsion (NTP) uses the fission process to heat up a propellant - generally hydrogen - to a very high temperature and then accelerate it through a nozzle to create thrust. Nuclear fission replaces the heat of combustion in traditional chemical propulsion such as rocket stages using hydrogen and oxygen. For missions beyond earth orbit, NTP enables much faster transit times. 

Nuclear electric propulsion (NEP) utilizes the fission process to generate electrical energy which then drives an electric propulsion system (e.g. arcjet or ion thruster). Depending on the propulsion system used, the thrust is produced by accelerating hydrogen, xenon, argon, or another fluid. Some of the electrical energy generated also provides primary power to the spacecraft. NEP provides much greater power capacity and higher propulsion efficiency for spacecraft.

Finally, small modular nuclear fission reactors on the moon, Mars, or other celestial bodies can enable extended power intensive surface operations. In addition to mobility and life support functions, these reactors would enable full scale in situ resource utilization such as the production of hydrogen and oxygen from harvested ice.

NIMBY Everywhere

A nontechnical barrier that all nuclear fission systems face, whether in-space or on the ground, is sometimes termed "not in my backyard" (NIMBY). NIMBY comes into play on many topics that impact the public, from landfills to prisons. In the case of nuclear reactors, the relevant "backyard" can be a very large area indeed based on air or sea circulation patterns.

The general public wariness of anything related to nuclear power is not unwarranted. For every well known nuclear related disaster - Three Mile Island, Chernobyl, Fukushima - there are many more "near misses". These almost accidents are caused by operator error, various system failures, fraudulent inspection or maintenance records, and many other factors.

In addition to the public risk perception related to operating nuclear systems, there is also the issue of nuclear waste disposal. NIMBY comes into play even more strongly on this issue. As a result, public acceptance of nuclear fission for any application - space, power plants, or otherwise - is a challenging consideration.

Nuclear Power for Hydrogen Production

Existing nuclear power plants, and the utilities that own them, have a rather intractable economic problem. These plants are no longer cost competitive compared to other power generation options. And in the U.S., for example, many state and regional public utility commissions are balking at passing these higher costs on to the consumer.

But nuclear reactor cores cannot simply be shut down like a fossil fuel power plant. The half-life of the radioactive fuel used in them is unaffected by the whims of political policy or utility economics. Decommissioning a nuclear power plant is a complex and expensive undertaking that requires ongoing site control and monitoring for a very long time.

One potential option is to repurpose some of the existing global nuclear power plant capacity to produce hydrogen via water electrolysis. This approach would contribute to the reduction of greenhouse gases as the generated hydrogen displaces legacy fossil fuels. It also redeploys nuclear power assets that are no longer economically competitive for grid power generation.

Whether these advantages offset the previously mentioned public safety and nuclear waste disposal concerns is a matter of considerable debate. It will require circumspect policy formulation that ideally engages the public at large. And the path forward will undoubtedly vary among nations based on regional energy policy, resources, existing infrastructure, and many other parameters.

Matt Moran is the Managing Member at Moran Innovation LLC, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems for more than 40 years; and first-of-a-kind liquid, slush and gaseous hydrogen systems since the mid-1980s. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been a cofounder in seven technology based start-ups; and provided R&D and engineering support to hundreds of organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management report series. More about him can be found here.

Hydrogen is Best Served Cold

Storage and Delivery Options

One of the key decisions in developing a hydrogen system is deciding how - and in what form - to store and deliver it. The most common approaches are ambient temperature compressed gas up to 700 bar, or low pressure cryogenic liquid near 20 K.

Other methods have been tried and are the subject of ongoing research and development. These include: materials that trap hydrogen by molecular or chemical means; cryo-compressed (transcritical); and hydrogen "carriers" that are converted prior to use (e.g. ammonia).

Any application should be evaluated to determine the best approach given the system objectives, requirements, constraints, and concept of operations. For large scale applications, and vehicles with onboard hydrogen storage (land, sea, air, or space), liquid hydrogen is often the best solution.

Liquefied Hydrogen

Liquid hydrogen has several critical advantages compared to other forms of hydrogen storage:

• Relatively high volumetric density at low operating pressures
• Long history of production, storage, transport, and usage
• Off-the-shelf subsystems and components available
• Many legacy stationary, over-the-road, train, barge, and launch systems
• Zero boil-off possible with proven cryo-refrigeration technology
• Low temperature provides ancillary system capabilities

The above advantages are partially offset by the unique design and operational considerations associated with liquid hydrogen. Some key considerations include: liquefaction (and re-liquefaction), material properties, fluid thermodynamics, phase change, and thermal management.

Although there are well established and validated methods to fully address these considerations, the requisite knowledge base is not widely disseminated yet. The primary motivation for this blog is to share that knowledge base with a wider audience to accelerate the safe and effective adoption of liquid hydrogen in new areas of application.

Below is a presentation I gave a few months ago at the Center for Hydrogen Safety Asia-Pacific Conference that addresses zero boil-off and densified liquid hydrogen systems. Future posts will provide more details on these and other related topics.

Matt Moran is the Managing Member at Moran Innovation LLC, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems for more than 40 years; and first-of-a-kind liquid, slush and gaseous hydrogen systems since the mid-1980s. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been a cofounder in seven technology based start-ups; and provided R&D and engineering support to hundreds of organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management report series. More about him can be found here.

Hydrogen Myth Busting (Episode 2)

Global temperature anomalies (Source: NASA GISS)

In my previous post, I started to address some common and recurring myths about hydrogen. This post will continue along the same theme, but with myths that have more nuances to unpack.

Myth #5: Making Hydrogen From Renewables Isn't Practical

There are multiple variations on this myth. Some of the most persistent of them include:

• There aren't enough renewable resources to support all the carbon-free hydrogen production needed
• Renewables should only be used to directly meet the electrical demand; producing hydrogen with them is wasteful
• Conclusions regarding hydrogen production from renewables specific to a particular region are globally true everywhere

    Not enough renewables

Let's start with the first variation. A typical set up for this argument is that if all fossil fuel applications were immediately switched to hydrogen there wouldn't be enough renewable energy capacity to support its production. 

The fundamental flaw with this argument is that every energy transition occurs over decades; there has never been and will never be an immediate transition to any new energy paradigm. If this argument had carried the day prior to the industrial revolution, our energy and transportation systems would still be based on horses.

Hydrogen production using renewables is growing via the deployment of new solar, wind and other generating capacity. These renewable resources can be used during periods of over-generation (more on this below), or supplied from dedicated new microgrids.

 

    Renewables should only be used for electrical demands 

In a fantasy computer simulation, it may be possible to make the sun shine and the wind blow whenever needed to perfectly match the electrical demand at all times. Unfortunately, electrical demand never matches available renewable energy in the real world.

The historical solution to this problem has been to use base load generating sources such as coal-fired or nuclear power plants plus peaking capacity (e.g. natural gas or diesel) to balance power vs load. However, as more renewables come on line, this balancing act becomes untenable when renewables reach about 30% or more of the generating mix.

As fossil fuel generating capacity continues being replaced by cheaper renewables, energy storage will become increasingly necessary to maintain the balancing act. If the local geographical features support pumped hydro (water) storage, that may be the cheapest and simplest solution for that locale. If the scale is not too large, batteries may also provide a reasonable solution.

But for large grids, or microgrids that also incorporate fueling functions, hydrogen is the solution that can be implemented anywhere at any scale. And the lifecycle costs and supply chain risks are lower than batteries under these conditions for an equivalent storage capacity.

    The same hydrogen solution applies everywhere

Consider a densely populated small region in the upper northern hemisphere with limited solar irradiation and no real estate for wind power. Large scale production of hydrogen from renewables in this region may not make much sense.

Now consider a sparsely populated larger region near the equator or in the southern hemisphere where there is an abundance of solar and wind resources and vast real estate available at a low price. Hydrogen production from renewables in this region is not only feasible but may represent a lucrative export opportunity. It can be transported to that densely populated region similar to oil or liquified natural gas.

Between these two extremes are a plethora of regions with varying natural, economic, and geopolitical conditions that dictate what type of hydrogen infrastructure makes sense for that location. And yet it is not uncommon to see articles and policymakers who declare a recent study for a specific region to be "the answer" on how hydrogen should be implemented globally.

Myth #6: Hydrogen Isn't Green

As with the previous myth, there are variations on this one:

• Since most hydrogen has historically been produced with steam methane reforming (SMR), it isn't a solution to climate change
• Hydrogen may contribute to global warming

    Hydrogen production

Hydrogen and lithium ion batteries can be used to store energy. When that energy is used, no carbon byproducts are emitted. These are simple irrefutable facts based on the associated chemical processes.

If the feedstock for producing hydrogen is water that is electrolyzed using solar or wind, then it is a "green" method of production. If batteries are charged using the same renewables, then the charging process is green.

Neither hydrogen nor batteries are inherently green or not... it is the lifecycle ("cradle to grave") processes associated with them that determine the impact on the environment. In the case of hydrogen, the number and capacity of electrolyzer installations powered by renewable energy are growing rapidly and represent a truly green source of energy storage and fuel.

    Hydrogen leaks and global warming

This relatively new myth is based on a recent study that has been warped beyond recognition to produce tabloid worthy - and grossly inaccurate - headlines. The study in question poses the following (paraphrased) scenario:

If hydrogen were to be produced in the quantities required to replace fossil fuels; and large aggregate leaks of hydrogen were permitted to occur throughout this new global hydrogen infrastructure; and furthermore, these leaked quantities of hydrogen managed to reach the upper atmosphere without already combining with oxygen in the lower atmosphere or water; it may combine with hydroxides in the upper atmosphere to form water vapor.

 So what's the issue? Keep reading...

This process may inhibit the amount of upper atmosphere hydroxides available to react with the large amounts of leaked methane; thereby inhibiting the ability to mitigate the impact of methane sources and leaks.

While methane is a very potent and prevalent greenhouse gas, it's rather difficult to overlook the circular argument of this scenario. Namely, that transitioning to hydrogen might inhibit the upper atmosphere mechanism that helps to mitigate the greenhouse gas effects of one of the fossil fuels that hydrogen will replace.

The study goes on to recommend that implementation of global hydrogen infrastructures should address leakage to ensure very little reaches the upper atmosphere. The methods and technologies for minimizing hydrogen leaks are well known within the hydrogen community and are already used in any appropriately designed system.

This is a key takeaway and valid consideration as we transition to hydrogen. Unfortunately, that valuable nugget rarely seems to make its way into the subsequent articles that misrepresent the findings. Instead, a more sensationalized tale is spun about the effects of large scale hydrogen usage and greenhouse gases. While that may draw a lot of readers, click-throughs, and online traffic, it is clearly misleading.

Myth #7: Any Particular Technology is the Only Solution

Lithium-ion batteries have evolved to become a truly amazing energy storage technology. High round trip efficiencies during charge and discharge cycles. Portability ideal for very small scales up to automobile applications. Continuing improvements that extend useful life before replacement is necessary.

Li-ion batteries also have their weaknesses. Charging time and heating; temperature effects on performance; thermal runaway if punctured or crushed; strategic materials issues; recyclability; limited practical scalability; weighs the same fully charged as fully discharged.

Hydrogen has its own strengths and weaknesses. Its much higher energy density relative to batteries extends the range and capacity of land, air, and marine electric vehicles. And the vehicle becomes lighter as the hydrogen is consumed, unlike batteries. There are no strategic material nor recycling issues. The operational lifetime of hydrogen systems are measured in decades. Hydrogen systems are scalable to meet very large energy storage requirements, and any application that currently uses fossil fuels.

On the downside, hydrogen has lower round trip efficiency when used in a fuel cell compared to Li-ion batteries (although much higher than any combustion process). High compression as a gas or liquefaction at cryogenic temperatures is required to overcome its otherwise low volumetric density. And workforce training is needed to ensure the required skillsets are sufficiently available for properly designing, commissioning, and operating new hydrogen infrastructures.

Other solutions that reduce or eliminate greenhouse gas emissions have their own unique pros and cons. No single technology or solution is universally optimal for every application. The path to a more secure energy and environmental future requires careful consideration of all feasible options that get us closer to that goal. An important step forward is dispelling myths promulgated by vested interests or the misinformed.

Matt Moran is the Managing Member at Moran Innovation LLC, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems for more than 40 years; and first-of-a-kind liquid, slush and gaseous hydrogen systems since the mid-1980s. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been a cofounder in seven technology based start-ups; and provided R&D and engineering support to hundreds of organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management report series. More about him can be found here.