Energy Storage: McPhy’s Hope for Hydrogen

Venture capital firm Sofinnova Partners led a $17.1 million investment in France-based McPhy Energy, which is working to commercialize solid-state hydrogen storage technology.  Soffinova was joined by private equity firms Gimv and Amundi in the funding process.  This investment follows a $2 million round in 2009 from investors Emertec and Areva.

McPhy was founded in 2008 and is focused on developing and bringing to market technology for practical, reversible and low-pressure solid storage of hydrogen in the form of magnesium hydride.  Storage in the form of magnesium hydride has been investigated at length but has yet to reach commercial scale, performance and price.

Hydrogen has long been the subject of research as an energy feedstock to power fuel cells and vehicles.  The technology works, but storing and transporting the hydrogen has always been the bottleneck in mass commercialization.  Because it is such a light gas, practical storage requires intense compression and high-mass, high-strength storage vessels.  Storage of hydrogen in liquid form is even less practical because of extremely low temperatures and high cost. Still, hydrogen has the highest energy density per kilogram in comparison with other combustible fuels, hence the interest in the element (see chart).

Hydrogen has almost three times the energy content of gasoline (120MJ/kg vs. 44MJ/kg), but the low density of H2 gas means low volumetric energy content.  Hydrogen is abundant, but it exists only in the form of compounds.

Another firm that has been conducting research on hydrogen storage is engineered-carbon startup EnerG2, which raised $3.5M to develop nanoscale materials for ultracapacitors for EVs, PHEVs, and for hydrogen storage.  Here's a perspective piece on storage from the firm. 

McPhy envisions the use of its storage technology in tandem with a renewable energy source like solar to power an electrolyzer, which then produces hydrogen for fuel cell energy production or to spin a turbine.

Research in Metal Hydrides

Sandia is leading the Metal Hydride Center of Excellence in looking to reach the goals that the DOE has set for hydrogen storage through the development of reversible metal hydrides materials.

Although Steve Chu and the DOE have slowed down hydrogen research in favor of our current energy policy (that's a joke, by the way; we don't have an energy policy), hydrogen fuel and storage is alive and well in research labs.  There is still a community of scientists laboring to improve performance and discover materials to enable the hydrogen highway.

Metal hydrides represent a class of materials with volumetric densities higher than gaseous or liquid hydrogen that could enable effective solid state hydrogen storage.  There is a DOE hydrogen storage program with stated goals, but according to a presentation by Sunita Satyapal of the DOE, "No [hydrogen] technology meets targets."  Here's a link to a long list of DOE publications on hydrogen research.

This remains complex stuff and heady materials science.  Some of the more promising materials being investigated are complex metal hydrides, including metal alanates, amides, borohydrides and their derivatives.  The DOE wants a reversible 5.5% hydrogen storage system, and according to Stavila, "As of now, none of the materials investigated so far satisfy all of the DOE targets."

There is also a time factor involved in getting these materials to absorb and release hydrogen.  Despite significant improvements in the storage capacity, most of the hydride materials still require high temperatures to decompose and release their hydrogen.

Innovation in Hydrogen Sources

Michael Kanellos recently reported on a virus that makes hydrogen and I covered Sun Catalytix, a VC-funded company looking to inexpensively electrolyze water.

Early-stage startup Pilus Energy makes a microbial fuel cell which produces hydrogen gas and DC electricity from the metabolism of organic materials by genetically engineered bacteria.  Feedstocks for the Pilus bioreactor are organic compounds found in waterways, plant pulps, farm wastes and sewage.  A video illustrating this concept is here.

A Quick Review of Utility-Scale Energy Storage Technologies

Utility-scale energy storage in the field today is limited to pumped hydro, a few large deployments using compressed air energy storage (CAES), hundreds of megawatts of sodium sulphur (NaS) batteries, mostly in Japan, and some experiments with banks of lithium-ion batteries, nickel-cadmium batteries and regenerative fuel cells (flow batteries).

Improvements in batteries, fuel cells, hydrogen storage, ultracapacitors, molten salt, flywheels, phase-change materials, SMES, etc., will come from incremental advances in materials science.  Although a "black swan" breakthrough would be most welcome in this field, we are dealing with the limits of known elements, compounds and physics.  Maybe some revolutionary advance will rock our paradigms, but for now, improvements in energy storage will come from hard, slow work in the labs of materials scientists.

A few firms are looking into energy storage via ammonia synthesis.  The concept is to use energy generated by remote or offshore wind turbines to perform "solid-state ammonia synthesis" and transport that ammonia by land or sea to be used as a fuel.  This obviates the need for distant wind farms to be expensively connected to the grid. 

Doty Energy wants to use off-peak wind energy to efficiently synthesize fuels, like gasoline and diesel, from CO2 and water.  According to the company founder, David Doty, strong arguments for the concept include: (1) the energy storage density in stable liquid fuels is two orders of magnitude greater than the energy storage density in batteries, (2) the energy stored in liquid fuels can then be used seamlessly within our current transportation infrastructure, and (3) the chemical processes being developed promise the scalability needed to competitively replace petroleum-based fuels.  Doty's process electrolyzes water and combines the generated hydrogen with CO in a Fischer-Tropsch process to produce the liquid fuels.

Amongst the many energy storage technologies we've covered:

Kawasaki is looking to deploy nickel metal hydride (NiMH) technology for grid-scale energy storage applications. NiMH is good at fast-charge and fast-discharge applications versus, say, sodium sulfur NaS technology, which is good for projects that require massive capacity, but is limited by its six-hour charge cycles and high operating temperatures.

Gravel-based thermal storage from Isentropic Energy -- Thermal Energy Storage Breakthrough?

Compressed Air Energy Storage (CAES): part 1, part 2, part 3  

Ice -- Ice-based thermal storage, also from Cryogel

Ultracapacitors -- Maxwell and the Promise of Ultracapacitors 

New flywheel technology from Velkess.

If I've missed any storage technologies, or if you're an entreprenuer with a new idea -- please comment below or get in touch with me at wesoff@greentechmedia.com.