Ringside: Green Hydrogen in California

Last week I received an email from a representative of a company planning to build a large scale green hydrogen production facility in California. In reviewing the details announced in this email, which was almost certainly sent to other analysts and journalists, I saw an opportunity to take another look at the challenges facing any serious attempt to replace conventional energy with hydrogen.

For a detailed description of the various ways hydrogen is produced and what each type of hydrogen is called, read “The Many Colors of Hydrogen.” In brief, how hydrogen is produced is categorized using colors which include green, pink, purple, red, yellow, grey, brown, black, turquoise, gold, orange, clear, and white. Believe it or not, with only slight overlap, there is general agreement as to what each of these terms means, and each refers to a distinct process.

Green hydrogen refers to hydrogen produced using electrolysis, a process where an electric current is passed through water, causing it to separate into hydrogen and oxygen atoms. But to be “green” hydrogen, that electricity has to come from renewable sources such as solar or wind.

With that in mind, here is what the email claimed this company plans to do:

• Produce 22,000 tons per year, or 60,000 kg per day, of green hydrogen fuel.
• Transport fuel via fuel cell electric trucks, themselves powered by green hydrogen.
• Supply the First Public Hydrogen Authority for uses in city buses, port vehicles, and more.
• Run fully on on-site solar energy, using groundwater under the 2,100 acre property.

To begin with, this is definitely an ambitious production goal. 22,000 tons of hydrogen would have the potential to power 31 billion vehicle miles, nearly 10 percent of the roughly 340 billion vehicle miles driven in California each year. That estimate assumes a currently best case 60 percent efficiency converting hydrogen into electricity using an on-board fuel cell, and it assumes average EV mileage to be a very generous 3.5 miles per kilowatt-hour.

Compare that to the output of the soon to be shuttered Phillips 66 refinery in Long Beach that processes 50.7 million barrels of crude oil per year. Based on 20 gallons of gasoline per gallon of crude (50 percent of the crude oil is used for other petroleum products), and average 34 MPG in California, that refinery fuels 34 billion vehicle miles per year.

A new H2 plant — gain energy for 31 billion vehicle miles. An oil refinery going offline — lose energy for 34 billion vehicle miles. But behind our glib dreams of carbon neutrality, there are devilish details.

Transporting meaningful quantities of H2 “via fuel cell electric trucks, themselves powered by green hydrogen,” requires liquefaction, where the gaseous hydrogen is cooled to -425 degrees fahrenheit. According to the US Dept. of Energy, “liquefaction consumes more than 30% of the energy content of the hydrogen and is expensive.”

Details multiply, and invite an obvious question: Is powering vehicles a good use of green hydrogen? We aren’t even considering the minor details of manufacturing and selling millions of fuel cell vehicles, or building thousands of H2 refueling stations. Let’s just stick with the fuel itself. Producing 22,000 tons per year of green H2 requires electrolysis, using electricity coming from photovoltaic cells. Assume this company installs 2,100 acres of solar panels. That would be a stretch, since solar panels themselves cannot possibly occupy 100 percent of the area where they’re deployed. Open lanes for maintenance are required between the rows of panels, and the property would need to have areas allocated for electrolysis, storage, and transportation. But here goes:

For 2,100 acres of photovoltaic panels, an optimistic power generation assumption would be 20 watts per square foot in full sun, and a 25 percent yield (i.e., a yearly average of six “full sun equivalent” hours per day). That would generate just over 4,000 gigawatt-hours per year. In reality, about half that might be more likely on the site as described, but let’s continue.

Current electrolysis technology can only turn 40-60 percent of the input electricity into hydrogen. Emerging technologies claim potential to achieve efficiencies of over 90 percent. But even assuming a commercially feasible efficiency of 80 percent, at 3.4 billion BTUs per gigawatt-hour, and 2.4 billion BTUs per ton of hydrogen, 4,000 gigawatt-hours would only generate 4,549 tons of H2. A 2,100 acre facility cannot possibly use on-site photovoltaics to produce 22,000 tons of H2 per year.

Moving on, according to Sandia National Labs, “the roundtrip efficiency of hydrogen storage based on electrolysis and fuel cell systems is generally around 40%, meaning that approximately 40% of the energy used to produce hydrogen with electricity can be turned back into electricity.” That’s taking into account the efficiency of electrolysis, plus the loss required to store the hydrogen, plus the efficiency of an onboard fuel cell to turn that H2 back into electricity to power a vehicle’s electric motor. We could argue it’s much worse. Current electrolysis at 50 percent, times retaining 70 percent of that after using energy to freeze and transport liquified hydrogen, times an onboard fuel cell converting 50 percent of H2 back into electricity, equals a mere 18 percent of the electricity from photovoltaics being eventually realized as actual horsepower on the road.

These numbers only scratch the surface of what technical and financial hurdles confront anyone serious about commercializing green hydrogen to fuel vehicles. Investors and policymakers still have to consider the alternative of sending photovoltaic electricity directly into transmission lines to be stored and traded using private and decentralized vehicle-to-grid and stationary battery technology.

The roundtrip efficiency of battery-electric vehicle solutions is currently around 80 percent. While not yet enough to silence the skeptics, photovoltaic and battery technologies continue to drop in price and total resources required, and they continue to improve in practicality.

Hydrogen may find its niche. But to ever become an economically competitive technology for transportation, it still has a long, long, long, long, long way to go.