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…