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…
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…
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…
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…
