Hydrogen System Architecture and Software Demo

The variability of wind and solar energy sources presents a challenge for meeting electrical load requirements. Isotherm Energy has developed a system architecture for addressing this challenge that provides energy storage, potable water, and hydrogen fuel production. The architecture enables tailoring of system parameters to meet specific application requirements using current and emerging technologies.

Click here to view a demonstration of the software

Isotherm Energy is developing a suite of software tools to simulate, analyze and design systems based on our hydrogen storage system architecture. The software allows selection of various input energy sources, water sources, biomass and other inputs. Subsequent screens allow the selection of options for hydrogen production, storage, byproducts, power generation, heat recovery, power output, excess hydrogen, and water management.

Once the architecture options are selected, the software generates a system model that incorporates all the chosen parameters. The system model calculates all energy and mass flows between subsystems along with heat available for recovery and improved overall system performance. Note that all system flows are driven by the load following function of the power management and distribution (PMAD) subsystem and calculated accordingly.

 

The system model has an optional time stamp capability for the conditions being simulated. When the “Save Conditions” button is clicked, all of the parameters associated with the time stamped simulation are stored for subsequent transient analysis. In this manner, a sequence of simulated hours, days, weeks or a full year can be automatically generated and investigated. Every parameter of the system can then be adjusted using built-in optimization tools to meet the performance goals over any timeframe of interest.

The software also provides complete flexibility in the selection of system variables such as electrical load and energy inputs. These can be a constant number at a given timestamp, a historical profile, a statistical distribution over a time averaged period, a stochastic probabilistic algorithm (e.g. Monte Carlo), or some other user defined method.

New capabilities under development include:

• Detailed subsystem and component models
• Drop-in capability for existing and emerging technologies
• Comparison to other storage options (e.g. batteries, compressed air, pumped hydro, etc.)
• Capital/operating expenditures, payback period, levelized cost of energy and other financial

Matt Moran is the Managing Member at Moran Innovation, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems since 1982. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been involved in seven technology based start-ups; and provided R&D and engineering support to many industrial, government and research organizations.  More about Matt here…

NASA Johnson Space Center Hosts Engineering Course

Matt Moran taught his popular course on Excel VBA for engineers at the NASA Johnson Space Center on August 8-10. The course provides in-depth details on principles, practices, and implementation of Excel and its integrated programing language – Visual Basic for Applications (VBA) – for analysis and engineering model creation.

Techniques and methods taught in the course allow the creation of custom engineering models for: analyzing conceptual designs, creating system trades, simulating operation, optimizing performance, and more. Matt has taught this course to hundreds of participants since 2007, and hundreds more have purchased his published course notes in paperback and Kindle versions.

Newly remodeled training building at NASA Johnson Space Center where course was held.

Matt Moran is the Managing Member at Moran Innovation, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems since 1982. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been involved in seven technology based start-ups; and provided R&D and engineering support to many industrial, government and research organizations.  More about Matt here…

The Path to Greenhouse Gas Emission Reduction (Part 1)

Last week I participated in a business roundtable discussion in Toronto hosted by Canada’s Ontario Centres of Excellence (OCE).  The focus of the meeting was to bring together industry emitters and solution providers for a collective discussion about how to meet the province’s greenhouse gas emission reduction target of 37% below 1990 levels by the year 2030.

These types of conversations are occurring around the world in various forms as each nation participating in the 2015 United Nations Climate Change Conference in Paris formulate policies to meet the emission goals agreed upon.  Although the implementation details will undoubtedly vary within the global community, many of the key challenges and opportunities are common to all.

In preparation for the meeting, the OCE requested feedback from the invited participants regarding the appropriate path forward, the roles each of us can play, and the barriers to success.  I believe these questions form a useful framework for many governments that are grappling with the same issues.

Clean the Smokestack?

OCE welcomes industry stakeholder feedback on the following questions: Looking forward to 2030 and Ontario’s GHG emissions target of 37% below 1990 levels, what do you view as the path forward for the Province to meet this emission reduction target?

Isotherm Energy: There are two general approaches to lowering emissions:

1. Reduction of emissions between the combustion source and the smokestack. This is a near term solution that reduces atmospheric emissions, but must still address the captured carbon. Enable greater adoption of renewable sources to accelerate transition away from fossil fuels. This is a mid-term solution that addresses the problem at the source by reducing carbon based fuels. A balance of these two approaches is ideal.
2. The “clean the smokestack” approach is by far the historically favored solution to reducing airborne emissions of all kinds.  My experience with this approach started with my first engineering job in 1982 at a 2200 MW coal-fired power plant.  The plant was finishing a nearly half-billion dollar installation of precipitators to remove particulates from the smokestacks to meet regulations.  At the time, the industry was denying any connection between the sulfur contained in the coal being burned and acid rain miles away in the direction of the prevailing winds aloft.  Many years later, the same plant finally made a capital investment of nearly two billion dollars to install flue gas scrubbers that remove most of the sulfur dioxide and nitrous oxide emissions, again to meet regulatory requirements.  No doubt, they are now looking at an even larger price tag for reducing carbon emissions.

Of course, this smokestack approach is not unique to the stationary power generation industry.  In 1985, I was recruited by NASA to develop space experiments for the space shuttle to study the effects of low gravity on combustion phenomena.  During our early development testing in drop towers on earth that provide a few seconds of weightlessness, we filmed the formation of soot emanating from liquid hydrocarbon fuel droplets that had never been previously observed nor predicted.

Hydrocarbon droplet combustion soot formed during a drop tower test at NASA

In a subsequent discussion about soot formation with one of our principal investigators, he commented that soot is a big health problem, and used diesel fuel as an example.  He explained that there is an upper limit on size above which the lungs can expel an inhaled particle, and a lower limit below which a particle is absorbed into the body via the alveoli in the lungs.  But for sizes between those upper and lower limits, the lungs can neither expel nor absorb a particle.  And diesel soot particles are in that size range that can become permanently entrapped in the lungs.  That’s why diesel trucks have their tail pipe exit so high above the ground, he concluded.

Observing this smokestack approach to airborne emissions reveals some inherent recurring patterns.  These include very long cycles of:

• Growing evidence regarding the detrimental impacts of a particular emission
• Public denials of the data by entrenched interests
• Eventual policies and regulations to address the issue
• Costly implementation of commercially available systems targeting the emission

These cycles often take decades to culminate in the reduction of the target emission, while it’s detrimental health and environmental impacts continue to grow in the interim.  And in the end, another symptom of the core problem is addressed without addressing the root cause: the combustion of hydrocarbon fuels.

In my next post, I’ll touch on the second part of the answer we gave the OCE for the path forward.  Accelerating the adoption of renewable energy sources requires systems integration, application optimization, and sustainable energy storage.

Matt Moran is the Managing Member at Moran Innovation, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems since 1982. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been involved in seven technology based start-ups; and provided R&D and engineering support to many industrial, government and research organizations.  More about Matt here…

Carbon Neutral Liquid Fuels

The U.S. Department of Energy’s ARPA-E recently announced funding for a new program to support technology development proposals that use renewable energy to convert air and water into “carbon neutral liquid fuels (CNLF)”.  These cost-competitive, energy dense fuels must be storable, transportable and convertible to hydrogen or electricity.

Examples of CNLFs include: ammonia, hydrazine hydrate, carbohydrazide, and synthetic hydrocarbons that extract carbon from air or water thus meeting the carbon neutral criteria.  The overarching goal is to find suitable substitutes for carbon dioxide emitting transportation fuels like gasoline and diesel while retaining their advantageous energy density, storability and compatibility with the existing distribution infrastructure.

Perhaps paradoxically, “carbon zero” liquid hydrogen is specifically excluded from consideration.  No doubt, there are programmatic reasons for this exclusion based on other efforts in the DOE portfolio and investments previously made in hydrogen technologies and systems development.  But there are also technical reasons to look beyond liquid hydrogen.

The Challenges with Liquid Hydrogen

Hydrogen’s low volumetric density and cryogenic normal boiling point of -253 C poses unique challenges.  ARPA-E’s funding announcement document  succinctly describes how this impacts storage and distribution:

“Hydrogen compression and, especially, liquefaction incur additional energy losses (up to 10 and 35%, respectively). In contrast to liquid H2, which boils-off with a rate of 1 – 4% per day depending on the tank, hydrogen storage and transportation as a compressed gas has very low losses. Therefore, the latter is a more attractive option for long-term storage (from days to seasonal).” — Source: “Renewable Energy To Fuels Through Utilization Of Energy-Dense Liquids (REFUEL)”, Funding Opportunity No. DE-FOA-0001563, April 26, 2016.

While the above may be true for currently available commercial systems, liquefaction energy and boil-off losses can be significantly reduced with proven technologies developed in the aerospace industry.  In fact, zero boil-off liquid hydrogen systems have been developed by NASA and other aerospace organizations with combinations of advanced insulation, optimized structural/penetration design, Joule–Thomson cooling, para-to-ortho conversion cooling, crycoolers, and other technologies and innovative design features.  An example test article is shown below.

Source: Hastings, et al., “Large-Scale Demonstration of Liquid Hydrogen Storage With Zero Boiloff for In-Space Applications”, NASA TP-2010-216453.

Keep It Local?

The table below shows parameters for evaluating the full costs of delivery transportation power using carbon-free energy sources from the subject ARPA-E funding announcement .  Note that there’s an inherent assumption in this table that’s an artifact of our current transportation fuels paradigm that’s not in the footnotes.

Source: REFUEL announcement, April 26, 2016.

By necessity, the evolution of our fossil fuel industries and infrastructure has been largely predicated on geographic separation of extraction, refining/processing and point of use.  Oil or coal or natural gas doesn’t exist in every location where their derivative products are used.  In addition to the far reaching geopolitical ramifications, this reality has resulted in the need for a vast distribution system to service every link in the fossil fuel supply chain.

But is this a mandatory constraint in a carbon-less energy ecosystem based on renewable energy sources and hydrogen?  Renewable energy sources can be found anywhere, along with local sources for hydrogen production.  It’s interesting to consider the case where transportation costs of hydrogen are not applicable due to production and point of use occurring in the same location.  In that scenario, the total source-to-energy cost for hydrogen in the previous table becomes lower than the other carbon-free energy sources shown.

Many Paths Forward

Some combination of CNLFs, along with carbon-free hydrogen, will provide a transition path away from fossil fuels in transportation and stationary energy systems.  Isotherm Energy is positioned for whatever that combination may turn out to be with our hydrogen energy architecture.  Any of the CNLF options are compatible since they can be readily integrated into our architecture and processed into hydrogen at the point of use for the target application.  The destination of a more sustainable energy future is worth the journey.

Matt Moran is the Managing Member at Moran Innovation, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems since 1982. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been involved in seven technology based start-ups; and provided R&D and engineering support to many industrial, government and research organizations.  More about Matt here…

Power and Water the NASA Way

We’re sometimes met with a puzzled look at Isotherm Energy when we describe our hydrogen energy system architecture and its ability to store energy, generate power, recover heat, and produce potable water.  It seems the combination of functions – particularly energy and water together - is unfamiliar to many.  After three decades of working at NASA where these types of systems have been routine since the mid-1960s, I hadn’t considered that it might sound odd to those outside the aerospace industry.

A recent article about the famously jinxed Apollo 13 mission describes an early example:

“Apollo 13 lost its electricity, light, and water supply… The loss of an oxygen tank was crippling to an Apollo spacecraft because the oxygen tanks powered the fuel cells that powered the spacecraft… The electrochemical reaction of combining cryogenic hydrogen and oxygen produced electricity, heat, and potable water as byproducts.” [Popular Science, Apr 15, 2016]

Part of an unflown Apollo fuel cell [National Air and Space Museum]

The Space Shuttle also used fuel cells in a similar manner:

“Fuel cells are used in the space shuttle as one component of the electrical power system. Three fuel cell power plants, through a chemical reaction, generate all of the electrical power for the vehicle from launch through landing rollout… are individually coupled to the reactant (hydrogen and oxygen) distribution subsystem, the heat rejection subsystem, the potable water storage subsystem, and the electrical power distribution and control subsystem. The fuel cell power plants generate heat and water as by-products of electrical power generation.” [NASA]

One of the three fuel cells that provides electrical power to the space shuttle orbiter [NASA]

As another more personal example, I was asked in 1991 by NASA Headquarters to conduct a study on launching water to low earth orbit for processing into hydrogen and oxygen propellants to support missions to the moon and Mars.  The published system concept I designed used an electrolyzer to produce the propellants, and then liquefy them for storage until a spacecraft docked for refueling (see schematic below).  We would revisit aspects of this configuration later at NASA when I worked on designs to provide power, propulsion, water and environmental control for lunar surface systems.

Source: “Conceptual Study of on Orbit Production of Cryogenic Propellants by Water Electrolysis”, Moran, 1991.

So the integration of proven aerospace technologies into a combined energy-water-heat recovery architecture was a natural extension of my personal experiences and background.  And I’m convinced it will serve us well as we begin to view our energy, water and food systems here on earth from a more integrated sustainable perspective.

Matt Moran is the Managing Member at Moran Innovation, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems since 1982. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been involved in seven technology based start-ups; and provided R&D and engineering support to many industrial, government and research organizations.  More about Matt here…

System Modeling Software for Isotherm's Hydrogen Energy Storage Architecture

Isotherm Energy is developing a suite of software tools to simulate, analyze and design systems based on its hydrogen energy storage architecture.  The software allows selection of various input energy sources, water sources, biomass and other inputs as shown in the screen shot below.

Subsequent screens allow the selection of options for hydrogen production, storage, byproducts, power generation, heat recovery, power output, excess hydrogen, and water management.  Once the architecture options are selected, the software generates a system model that incorporates all the chosen parameters.

Below is an example of one of these system models that incorporates wind, photovoltaics, saltwater, electrolytic hydrogen production, compressed gas storage, fuel cells, and potable water production.  Oxygen is also stored as a cryogenic liquid in this model permitting passive cooling of the compressed hydrogen for greater density storage and higher fuel cell efficiency.

The system model calculates all energy and mass flows between subsystems along with heat available for recovery and improved overall system performance.  Note that all system flows are driven by the load following function of the power management and distribution (PMAD) subsystem and calculated accordingly.

The above screenshot represents a daylight scenario where the combined wind and solar energy input is sufficient to meet the electrical load, so the excess energy is directed by the PMAD subsystem to the saltwater electrolyzer.  Hydrogen and oxygen are thereby produced to be stored for later use in the fuel cell when needed.  Commercially saleable chlorine and sodium hydroxide byproducts are also produced during the saltwater electrolysis process.

When solar energy is unavailable, the system must augment the wind power by consuming stored hydrogen along with ambient air (or oxygen in this case) in the fuel cell to meet the electrical load demand.  The screenshot below shows the system model in this night time scenario.  With appropriate material selection and design, potable water is produced when the fuel cell is operating (for drinking water, irrigation, humidity control, etc.).

The system model has an optional time stamp capability for the conditions being simulated.  When the “Save Conditions” button is clicked, all of the parameters associated with the time stamped simulation are stored for subsequent transient analysis.  In this manner, a sequence of simulated hours, days, weeks or a full year can be automatically generated and investigated.  Every parameter of the system can then be adjusted using built-in optimization tools to meet the performance goals over any timeframe of interest.

The software also provides complete flexibility in the selection of system variables such as electrical load and energy inputs.  These can be a constant number at a given timestamp, a statistical distribution over a time averaged period, a stochastic probabilistic algorithm (e.g. Monte Carlo), or some other user defined method.

New capabilities under development include: 

• Detailed subsystem and component model
• Drop-in capability for existing and emerging technologies
• Comparison to other storage options (e.g. batteries, compressed air, pumped hydro, etc.)
• Capital/operating expenditures, payback period, levelized cost of energy and other financials
• Detailed design data, product selections, bill of materials, and more...

Isotherm Energy is developing this software to customize its hydrogen energy storage architecture for a wide range of applications in collaboration with its partners and clients.  Planned case studies will begin to explore grid connected and off-grid scenarios, particularly in markets where the benefits of the architecture uniquely address inherent key requirements and constraints (e.g. controlled environment agriculture).  Please contact us if your organization has interest in participating in these early stage studies.


Matt Moran is the Managing Member at Moran Innovation, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems since 1982. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been involved in seven technology based start-ups; and provided R&D and engineering support to many industrial, government and research organizations.  More about Matt here…

Cities of the Sea: Energy, Water and Food

Last week I taught an engineering systems modeling course at the Navy’s SPAWAR installation in San Diego, California.  In the evenings, we enjoyed the scenic vistas, great restaurants, and a little sightseeing.  One unexpected highlight on the last day of our trip was a visit to the USS Midway aircraft carrier that is permanently docked in San Diego bay, and is one of the most visited ship museums in the world.

The largest ship ever built at the time with a crew complement of over 4100, the USS Midway was also one of the longest serving aircraft carriers in the U.S. Navy (1945-1992).  Consider the tremendous operational challenges of providing energy, water and food for this floating “city on the sea”, and the continuing requirements for other large ships (both military and commercial) currently in service.

An Opportunity for Hydrogen Energy Storage?

Imagine the logistical benefits of a system that could store energy and simultaneously processes seawater to potable water for large ships.  Such a system might support onboard controlled environment agriculture using grow lights and mist irrigation to provide food and drinking water for the crew and passengers.  In addition, other onboard energy requirements could be met by the system thereby freeing up more primary power for propulsion and other critical functions.

Could Isotherm Energy’s hydrogen energy storage architecture be the basis for such a system?  In an upcoming post, I’ll explore that question along with other applications that are uniquely well matched for the advantages of hydrogen energy storage.

Matt Moran is the Managing Member at Moran Innovation, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems since 1982. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been involved in seven technology based start-ups; and provided R&D and engineering support to many industrial, government and research organizations.  More about Matt here…

Navy Hosts Engineering Course

Matt Moran of Isotherm Energy will be teaching his popular engineering analysis and modeling course to the Navy Space and Naval Warfare Systems Command (SPAWAR) on April 4-6 in San Diego, CA.  The Applied Technology Institute (ATI), a provider of short course technical training to aerospace and defense organizations, is coordinating the logistics.

The "Engineering Analysis and Modeling" course provides in-depth details on principles, practices, and implementation of Excel and its integrated programing language – Visual Basic for Applications (VBA) – for analysis and engineering model creation.  Matt has taught this course to hundreds of participants since 2007, and hundreds more have purchased his published course notes in paperback and Kindle versions.

Techniques and methods taught in the course allow the creation of custom engineering models for: analyzing conceptual designs, creating system trades, simulating operation, optimizing performance, and more.  An example of such a model created by Matt Moran for the power system of an underwater autonomous vehicle is shown below.

Matt Moran is the Managing Member at Moran Innovation, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems since 1982. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been involved in seven technology based start-ups; and provided R&D and engineering support to many industrial, government and research organizations.  More about Matt here…

Power Generation and Outputs from Hydrogen

This final post in the series introducing Isotherm Energy’s hydrogen energy storage architecture focuses on power generation and other output options from the system.  When needed, stored hydrogen is used to produce application-specific combinations of: electricity, kinetic power, heating, cooling, and potable water.

Power Generation

Hydrogen can be fed to fuel cells to produce electrical output when needed.  Ambient air is typically the other input to fuel cells, although pure oxygen is an option if water electrolysis is used and higher performance is desired.

The hydrogen can also be used in a variety of combustion processes including: turbines, internal combustion engines, burners, etc.  Depending on the application, the heat of combustion from hydrogen can generate kinetic energy (e.g. propulsion), or be converted from heat to electricity (e.g. Stirling engines).

For example, various scenarios for producing renewable hydrogen and electricity - that also incorporate natural gas - have been identified by NREL as shown below.  All of these hydrogen end uses have been demonstrated at commercial scale, and are continuing to expand in stationary and mobile markets.

Heat Recovery

Heat is generated by various processes of the system and can be recovered for combined heat and power (CHP), bottoming cycles, thermal energy harvesting, and other uses.  This increases the overall performance of the system while also meeting application-specific requirements.

The primary sources of heat generation in the system are fuel cells and combustion processes that operate during hydrogen usage.  Other components such as electrolyzers also produce heat during the production of hydrogen.  Optimizing the recovery of heat from these sources during various operations is key to designing a high performance system.

In applications where cooling is needed, “waste” heat can also be used to drive absorption cooling and other thermally-driven refrigeration cycles.  This allows the system architecture to accommodate both heating and cooling requirements along with energy storage.  Additionally, if the hydrogen is stored in liquid form, there is substantial thermal energy storage available to meet large cooling requirements if needed.

Water Production

Whether the hydrogen is used in fuel cells or combustion process, the primary byproduct is water.  With proper design and material selection, significant amounts of potable water can be harvested during operation to meet a variety of needs.

One obvious potential use is for drinking water, enabling both energy storage and water processing capabilities in one system.  The water could also be used in food growing systems, or as an additive in various processing operations that have compatible water quality requirements.

Another potential use in closed or semi-closed environments is humidity control and temperature reduction via evaporative cooling.  Adding this function in combination with previously described capabilities results in one integrated system for energy storage, environmental control, and water production.

Matt Moran is the Managing Member at Moran Innovation, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems since 1982. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been involved in seven technology based start-ups; and provided R&D and engineering support to many industrial, government and research organizations.  More about Matt here…

Storing Energy in the Form of Hydrogen

The core of Isotherm’s energy system architecture is hydrogen production and storage resulting from the inputs to the system.  There are multiple options to consider in order to select the optimal system design for a given application.

Hydrogen Production

When coupled with renewable energy sources, water electrolysis produces hydrogen gas without carbon emissions or the need to process feedstocks containing carbon.  Electrolyzers can be designed to operate with a variety water inputs (e.g. freshwater, saltwater, wastewater, etc.), or in a closed system mode with water recirculation from fuel cells or combustion processes.  The electrolysis and power generation functions can also be combined within a single unit known as a regenerative (hydrogen) fuel cell.

Conversely, hydrogen can be produced from biomass and other feedstocks containing hydrocarbons.  Biomass sources ideally provide a sustainable cycle when customized for the application, geographic location, and available resources.  Steam methane reformation, coal gasification and other fossil fuel based processes can also be used to generate hydrogen, although the associated carbon byproducts must be dealt with.

Other advanced techniques for hydrogen production have been demonstrated including: radiolysis (from nuclear radiation), photobiological (from algae), photocatalytic (from solar), among others.  Most of these technologies are early stage with limited commercial systems in place.  However, they have the potential for improving efficiency, flexibility and sustainability in future systems.

Oxygen and Other Beneficial Byproducts

Electrolysis and related processes produce oxygen as a byproduct that can be used within the system application, or sold as a commodity output.  Other beneficial byproducts are also produced depending on the water input.  Saltwater electrolysis, for example, produces sodium hydroxide and chlorine that have variety of commercial uses.  Urine electrolysis produces nitrogen that can be used or sold for plant fertilization.

Byproducts from hydrocarbons depends on the composition of the feedstocks and the processing methods used.  In general, these byproducts may be less desirable from a sustainability standpoint due to the remaining carbon content.  However, if properly sequestered and rendered into an economically viable form, these methods of hydrogen production can provide a transitional step toward the reduction of undesirable hydrocarbon combustion emissions.

Hydrogen Storage

Once the hydrogen is produced, it must be stored until needed.  The U.S. Department of Energy uses the taxonomy shown below to categorize hydrogen storage methods as either physical-based or material-based.

Comparison of the density as a function of temperature and pressure for physical-based methods is shown below, and falls into one of three categories:

• Compressed gas is a high pressure, ambient temperature, and moderate density condition that is currently the most common hydrogen energy storage method.  Typical storage pressures are 300 to 700 bar; requiring compressors, heat of compression cooling, and high strength storage tanks (e.g. composite overwrap stainless steel at the highest pressures).
• Cryo-compressed is high pressure, high density storage near the normal boiling point temperature of hydrogen (-253 C).  Additional capabilities beyond compressed gas systems are required to establish and maintain the low temperature conditions (e.g. a method of cryocooling and high performance insulation).
• Liquid hydrogen is a low pressure, low temperature (-253 C) storage method that eliminates the need for compression, but adds liquefaction.  Maintaining the desired thermodynamic conditions requires careful design of tankage and associated components to minimize environmental heat leak through piping and structural penetrations, and high performance insulation.

Material-based hydrogen storage systems, by contrast, use a variety of structural (e.g. nanopores) and chemical (e.g. hydrides) technologies to “trap” hydrogen.  Techniques for later recovery of the hydrogen depends on the technology used - adding heat to metal hydrides, for example.  Research focused on maximizing the storage capacity of material-based hydrogen storage is extensive and ongoing.

Matt Moran is the Managing Member at Moran Innovation, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems since 1982. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been involved in seven technology based start-ups; and provided R&D and engineering support to many industrial, government and research organizations.  More about Matt here…

Flexible Inputs to Hydrogen Energy Storage

Previous posts introduced Isotherm’s energy storage system architecture and the reasons why hydrogen is a compelling solution for consideration.  To get a better understanding of where and how the architecture can be applied, let’s take a look at the major subsystems and functions starting with the system inputs.

Energy Inputs

Electrical power system scenarios where energy storage is needed include: over-generation, variable generation, off-grid/microgrid, and other applications where power generation and electrical demand are out of phase in time.  Any source of electrical energy can be stored for later use subject to the inefficiency losses of the system.  In cases where these losses are economically preferable to shutting down a generating unit due to insufficient demand, for example, energy storage improves overall power generation performance.

Energy storage is particularly suited to renewable energy to offset the inherent fluctuations in generation from solar, wind and other variable sources.  Storage capability is necessary for most off-grid renewable power systems, and critically enabling to the trend of increasing renewable sources on the grid.  Using hydrogen storage technology for solar and wind energy sources also provides an end-to-end power system that produces no carbon emissions.

Transportation and other mobile applications can make use of hydrogen for fueling capability or onboard energy storage.  Vehicle systems face challenges with the need for a hydrogen fueling infrastructure, and the competitive advantages of battery technologies for onboard energy storage.  At larger scales and more limited route options (e.g. trains, ships, airplanes, etc.), these challenges begin to wane.  For these larger scale mobile applications, energy input can come from a variety of sources and can be set up at key refueling locations.  Alternatively, a hydrogen storage system can be integrated onboard and driven by the propulsion system to provide auxiliary power when needed.

Water Sources

Water in a hydrogen energy storage system can be recirculated from electrical generation output (e.g. fuel cell) to hydrogen generation input (e.g. electrolyzer) requiring limited water input.  However, if potable water production is a needed function, various water inputs can be provided in an open loop configuration.  Electrolyzers using saltwater have been demonstrated, and other water sources are possible (e.g. urine, wastewater, etc.).

This unique capability of potable water production in parallel with energy storage opens up many intriguing possibilities along the water-energy spectrum.  For example, the system could operate from solar and/or wind power to provide desalination in coastal regions and also provide electricity at night or when the wind dies down.  This system would also produce oxygen, sodium hydroxide and chlorine as byproducts of the saltwater electrolysis process that can be used locally or sold. 

For a remote location in a developing region, a microgrid could incorporate urine as the water input to the system.  In addition to potable water, oxygen and energy storage; the system would also produce nitrogen for crop fertilization.  In any of these configurations, the system design, operation and maintenance could be optimized for the application.

Other Inputs

An optional input to the system is the use of other potential sources of hydrogen such as biomass.  Various feedstocks can be used, and could replace the need for water inputs if desired.  In this case, potable water production and energy storage would be provided without any access to a water source.

Another possible input to the system is natural gas that can be converted to hydrogen via steam-methane reforming.  This is a mature process that has been used for decades for most of the hydrogen commercially produced.  However, it results in carbon monoxide and carbon dioxide that would need to be sequestered to maintain a zero carbon emission system.  This may be a viable transition option for using natural gas without the release of carbon by combustion.

Matt Moran is the Managing Member at Moran Innovation, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems since 1982. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been involved in seven technology based start-ups; and provided R&D and engineering support to many industrial, government and research organizations.  More about Matt here…

Why Hydrogen Energy Storage?

In my last post, I introduced the hydrogen energy storage system architecture being developed by Isotherm Energy.  But why choose a hydrogen-based approach?  What are the compelling reasons to consider such a system?  Let's start with some of the key advantages:

Energy Density and System Life - The amount of energy per unit mass for hydrogen storage technology is much higher than batteries or ultracapacitors.  It also has long storage times and equipment life, resulting in a high energy density system with low lifecycle replacement and disposal requirements.

Ratio of Energy Stored to Energy Invested - A net energy analysis of grid storage options conducted by authors from Stanford University,  Imperial College of London, and Western Washington University* found that a regenerative hydrogen fuel cell (RHFC) configuration provides higher lifetime energy returned, relative to the energy inputs required to build it, than the best battery technology available (lithium-ion).  The analysis study also reported that the reference RHFC could provide the same overall energy benefit as batteries for over-generation from wind farms, even at a round trip efficiency of 30% for the RHFC. 

Carbon-Free Energy Carrier - In addition to storing energy for reuse in electrical systems, hydrogen is an energy carrier that produces no carbon emissions when used as a fuel.  It can be transported and used for a variety of purposes that are currently the domain of fossil fuels.  This permits a multitude of options for stored hydrogen beyond the energy storage needs of a system.  Hybridized hydrogen systems of this type can be optimized to meet combined requirements of energy storage and fuel production. 

Water Production - A potentially valuable byproduct of a hydrogen energy storage system is the production of water when it is used in a fuel cell or combustion process.  With appropriate material selection and design, potable water can be extracted in significant quantities from the system.  Furthermore, use of a variety of water sources (e.g. saltwater, wastewater), biomass, and other hydrogen feedstocks can produce a water processing function that operates in parallel with energy storage. 

However, there are some inherent considerations to take into account for a hydrogen energy storage system: 

Roundtrip efficiency - The primary drawback of hydrogen energy storage systems is the relatively low roundtrip efficiency of the "charge-discharge" cycle.  For example, an electrolyzer can split water to produce hydrogen with an efficiency in the range of 70%.  When the hydrogen is used to produce electrical energy in a fuel cell or by heat of combustion, additional energy is lost in the conversion process.  For a fuel cell operating at 50% efficiency, the resulting roundtrip efficiency is roughly 35%. 

Safe handling - Despite some misperceptions, hydrogen systems are routinely used in a variety of industries(e.g. aerospace,  processing, and manufacturing).  These systems require certain precautions, material selection, design features and operational practices to insure safe operation.  Hydrogen has a wide flammability range in the presence of oxygen, and a relatively low ignition energy.  However, it's lighter than air and dissipates much more readily than gasoline and other fuels in an open environment.  It also has no lasting environmental impact once dissipated.  When properly designed and operated, a hydrogen system poses no more risk than many commonly used fuel and gas systems. 

Looking forward, Isotherm Energy is focused on several trends and opportunities that will drive the wider adoption of hydrogen energy storage systems: 

1. Technology advances in electrolyzer and fuel cell performance that continue to improve the round trip efficiency.
2. Hybrid systems that produce potable water and/or hydrogen fuel thereby increasing the overall performance by adding functionality that would normally require separate systems and processes.
3. Recovery of waste heat produced by system inefficiences to increase the overall performance.
4. Creation of system analysis and modeling tools that allow optimization of hydrogen energy storage systems tailored to specific application requirements. 

*Pellow, M.A., et al., "Hydrogen or Batteries for Grid Storage?", Energy Environ. Sci., 2015

Matt Moran is the Managing Member at Moran Innovation, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems since 1982. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been involved in seven technology based start-ups; and provided R&D and engineering support to many industrial, government and research organizations.  More about Matt here…

A Hydrogen System Architecture for Energy Storage and Water Production

The global community faces complex, highly interrelated challenges that cannot be addressed with legacy energy systems.  Carbon and methane emissions...aquifer and surface water depletion...population growth and economic development.  Our planet is becoming warmer, thirstier, and in ever greater need of systems that support sustainability.

Isotherm Energy is developing a system architecture for addressing these challenges that provides energy storage and potable water production.  The architecture enables tailoring of system parameters to meet specific application requirements using current and emerging technologies.

Isotherm's hydrogen-based system accepts inputs from a variety of energy (solar, wind, etc), non-potable water (saltwater, wastewater, etc.), biomass and other sources.  The selected inputs are used to produce hydrogen to be stored for later use.  Oxygen and other beneficial byproducts are also produced depending on the water and/or hydrogen feedstocks used.  Power is generated when needed from the stored hydrogen via fuel cells, turbines, internal combustion engines or other combustion processes.  The resulting outputs are electrical or kinetic energy and potable water.

Roundtrip efficiency of the system is optimized by incorporating heat recovery in the form of waste heat harvesting, combined heat and power (CHP), bottoming cycles and other combined cycles depending on the application.  The production of potable water from non-potable sources also increases the effective performance of the system relative to separate energy storage and water processing systems.  The architecture is scalable to a wide range of applications including:

• Microgrids and onsite water processing
• Desalination and energy storage
• Transportation systems

Matt Moran is the Managing Member at Moran Innovation, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems since 1982. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been involved in seven technology based start-ups; and provided R&D and engineering support to many industrial, government and research organizations.  More about Matt here…