I just read a news release on SMUD’s PV installation providing hydrogen (H2) via electrolysis for a fleet of fuel-cell vehicles. I made a feeble attempt, using Wikipedia, to figure out how much solar energy was captured, how much H2 was produced and how far the cars would travel after a typical day’s charge. I failed. My question: What is the overall efficiency (in a well-to-wheels format) of this PV/FC configuration. –Bryan B, Wylie, TX
Bryan, you ask a good question and I had to turn to hydrogen expert and CEO of H2Gen Innovations, Sandy Thomas, Ph.D. to answer your question. Here’s what he said:
“The efficiency of hydrogen production is relatively low: 75% electrolysis efficiency x 90% hydrogen compression efficiency x 50% PEM fuel cell efficiency X 92% electric motor efficiency = 31% system efficiency. Only 31% of the solar or wind electricity makes it to the wheels of such a car. (Still a heck of a lot better than the 12% to 15% of crude oil energy that makes it to the wheels of a conventional car!) But if the grid cannot absorb wind or solar electricity at any moment, it is better to capture 31% of this zero fuel cost, zero emission energy as a fuel for a zero emission FCV than to waste it.”
And hydrogen fits in neatly when the generation of renewables does not match the need of the electric grid and cannot be dispersed economically elsewhere. For instance, many wind regimes are at night when the electric utilities least need the power, so the excess electricity that the electric grid cannot absorb could be directed to electrolyze water (break it apart to isolate the hydrogen) to power vehicles or for stationary electric generation.
I have been considering using solar and wind myself to provide the hydrogen for my PEM fuel cell that augments power for my VA office — looking at these calculations makes me more interested.