written 16 March, 2025
published 23 March, 2025
Let's pretend. Assume most people want a habitable planet for their grandchildren. Imagine the partisan fever dream of climate denial has broken, and we realize only coordinated action will preserve our technological society. Rather than burning through our energy inheritance, consider living within our energy income, collecting heat from the Earth, and solar, wind and rain energy from the Sun.
Even if that all happened, we still need to be able to store this collected energy for months or years, using energetically efficient, economically affordable, existing technologies, which are scalable to the quantities needed. Several candidates exist.
Pumped hydro is currently installed at grid scale. Electric pumps push water to higher elevations, which then runs downhill, using the pumps as generators to produce electricity at a later time. This is expensive to install, not easily expanded, limited to sites with adequate access to water and elevation, and rarely stores energy for more than a few days due to capacity constraints.
The other possible candidate is using electricity to produce hydrogen by electrolysis of water, which can later be run through a fuel cell to produce more electricity. The problem is storing the hydrogen gas, the smallest molecule of matter. Hydrogen can be compressed as gas, cooled to a liquid, or converted to another chemical.
Hydrogen must be compressed to 250 atmospheres to increase the density enough to be stored and transported economically. To make hydrogen liquid, it must be cooled below -421°F. Both these storage forms take energy and expensive, specialized containers, limiting their economically viability. For long term storage of grid scale quantities, conversion to a "liquid organic carrier" produces the easiest storage form. Two options are commercially available: ammonia and methanol.
Ammonia (NH3) can be produced using hydrogen and nitrogen gathered from the air. It must be cooled to below -30°F to be kept liquid at atmospheric pressure. Even though ammonia is toxic, it is one of the most widely use industrial liquids. Ammonia is used as fertilizer, and can be burned in internal combustion engines. Alternately, the hydrogen can be regenerated and used in fuel cells. Ships that run on ammonia are now operating.
Methanol (CH3OH) can be produced from hydrogen and CO2 pulled out of the air. It is a liquid at room temperature and pressure, making it the cheapest of all forms to store. Methanol can be shipped by pipelines, rail cars, or tanker trucks, with no special storage requirements. It can be burned in an internal combustion engine, or regenerated back into hydrogen to run a fuel cell. Ships that run on methanol are now operating.
The full spectrum from power to liquid back to power requires four different stages of hardware: electricity to hydrogen, hydrogen to methanol, methanol back to hydrogen, and hydrogen back to electricity. Each stage takes some amount of energy. These needn't be large single plants, but collections of smaller identical units, mass production to reduce cost. The modularity of the hardware allows for phased development of the industry and creative distribution of the stored energy.
Methanol is perfect for backup power at critical facilities, such as municipal sewer and water plants, supermarkets, emergency shelters and communication systems. It could be burned as methanol, but that is energetically inefficient. Changing it back to electricity would be more efficient.
Taking Ukiah as an example, the City electric company could build all four functions in a central location and be able to store excess summer solar energy to provide electricity during the winter. With the addition of a large battery, power could be shipped over the grid at night, when grid capacity is available, and produce methanol all through the day. Ukiah could store some of this locally produced methanol at the sewer and water plants for backup power. Stored methanol at the MTA could power long distance fuel cell busses. Locally produced methanol would support the shift to long distance trucking using fuel cells. In addition, NCPA, Ukiah's power provider, could produce methanol at central valley arrays, and truck it to Ukiah without stressing grid capacity.
Grid scale power storage is a new addition to the electrical system, and planning and construction needs to begin now.
In light of current politics, this may sound like planning a picnic while ignoring the hurricane destroying the area. But holding an image of where we want to go helps us on the journey.
