Wednesday, March 16, 2016

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