Update: Edited to correct the cost per mile of a gasoline-powered vehicle.
Last week I wrote an article — Water Is Not A Fuel — discussing a press release I had received from Australian-Israeli startup Electriq~Global. As I noted in that article, it wasn’t my intent to criticize the company’s technology, but rather to explain how a person should approach these sorts of press releases.
In general, one should apply a healthy dose of skepticism, and then ask a number of critical questions. This press release didn’t go into enough details to ascertain the credibility of the technology, but I was subsequently contacted by the company to clear up my questions.
I spoke with Electriq~Global CEO Guy N. Michrowski. Much of what I suspected is true. The “fuel” in this case is a hydride, specifically potassium borohydride (KBH4). This compound stores hydrogen, but it also reacts with water to release hydrogen. Consistent with the laws of thermodynamics that I touched upon last week, the energy content of the hydrogen that is ultimately released had to be first put into the potassium borohydride.
What I did not know is that unlike some hydrides, potassium borohydride can be stored in water without a reaction. There is, indeed, a catalyst that is separate from the potassium borohydride that causes the reaction with water.
I had assumed a two-part system: Water and a hydride, in which water comes in contact with the hydride and reacts to release hydrogen. Theirs is a three-part system: Hydride is dissolved in water, and then there is a separate catalyst that causes the hydride to react with water, releasing some hydrogen from the hydride and some from the water.
The catalyst remains on board, and some of the water/hydride solution is brought into contact with the catalyst to produce hydrogen on demand. After all of the solution has been processed, it is returned for replacement and regeneration (which involves dehydrating the fuel). They expect the catalyst to need to be replaced every year, but still need to do more catalyst lifetime studies.
I asked about costs and range, and Guy emphasized that they are still at an early stage, but he could make some projections. He said that the goal from the Department of Energy for competitive hydrogen is $6 per kilogram at the pump. He believes they will be able to produce hydrogen for $4 per kilogram on board the vehicle.
Regarding the range, he said that it takes 25 liters (6.6 gallons) of solution to carry 1 kilogram (2.2 pounds) of hydrogen, which has a range of 100 kilometers (62 miles) in a light vehicle. If they are able to produce that for $4 per kilogram, then the fuel cost per mile is ($4/62 miles) = $0.065/mile.
For comparison sake, 6.6 gallons of gasoline in a light vehicle that gets 35 miles per gallon would have a range of 231 miles. At the current national average retail gasoline price of $2.42/gallon, the fuel cost per mile is ($2.42/35 miles) = $0.069/mile.
Of course the attraction of a vehicle powered by hydrogen is that there are no carbon emissions from the tailpipe. And, depending on the energy source used to produce the potassium borohydride, it has the potential to be an overall (nearly) zero carbon transportation option.
There are multiple classes of hydrogen storage options that can store more hydrogen than potassium borohydride. Just among the borohydrides, potassium borohydride can store 7.4 weight percent hydrogen, while lithium borohydride can store 18.3 weight percent. But lithium borohydride would not work in their system, as it reacts immediately on contact with water.
In conclusion, there are no huge technical problems that would prevent such a system from working as advertised. Range may be a bigger concern, but the upside is another potential transportation option that doesn’t require fossil fuels.