We have discussed green hydrogen as a clean fuel several times. July 3 issue of C&EN has a detailed article on the technology to split water into hydrogen and oxygen by electrolysis–the choices of equipment designs and their pluses and minuses.
C&EN editorial spells it out in some detail–
US DOE has a goal of 50 million metric tons of clean hydrogen by 2050.
To reduce the cost of clean hydrogen to $1/kg in the next decade
Current cost is $5-7/kg made by electrolysis or abt $2/kg ofblue hydrogen (made from natural gas but with collection and sequestration of carbon dioxide produced as a by product).
Electricity required for 50 mt hydrogen by electrolysis estimated at 2300 twh.
Utility scale solar plant generates 450 mwh per acre. 2300 twt requires 5.1MM acres of solar panels. Somewhere between the size of Connecticut and Massachusetts. But less than the size of Sweetwater Co, WY.
I think this reminds us that green hydrogen is feasible but massive investment is required. And likely to take a while. We have only scratched the surface compared to what is required.
Article notes that research goes on toward the goal of $1/kg but some major breakthroughs are needed to get there.
That may not be enough.
The process of manufacturing green hydrogen — known as electrolysis — converts water into hydrogen using renewable power, and the hydrogen it generates is nearly 14 times as expensive as natural gas to generate the same amount of power, Isaac Orr, a policy fellow at the Center of the American Experiment told the DCNF.
This is technically true, but misleading. If you read the DOE proposal, you’ll see it is mostly focused on the current industrial uses of hydrogen–most of which can’t be substituted for natural gas.
There needs to be a time component to that description. 450 MWh over how long of time? After doing some checking on real-world solar farms, it appears to be based on a yearly time scale. To be honest, looking at actual performance, 450 MWh/yr per acre seems a little high. It is more like 250 to 350 MWh/yr-acre. But let’s continue with the 450 number.
Using Google maps and its distance measuring tool, the two new nuclear plants at Vogtle in Georgia are built inside a rectangle about 0.5 mile by 0.75 mile in size. This includes the power plants themselves, plus the cooling towers, electrical switchyard, and most of the administrative buildings. 0.5 x 0.75 = 0.375 square mile, but let’s be generous and say everything is in 1.0 square mile. One square mile is 640 acres.
Assuming a 90% capacity factor, the new Vogtle plants will generate:
2234 MW x 24 hr/d x 365 d x 0.9 = 17.6 million MWh per year
17.6 million MWh/yr / 640 acres = 27,500 MWh/yr per acre
Solar : 450 MWh/yr per acre
Nuclear: 27,500 MWh/yr per acre
If you want to maximize electricity production while minimizing land area use, then nuclear is the way to go.
Getting the cost of hydrogen from water electrolysis down to the cost of producing hydrogen from natural gas is going to be difficult. It is always going to take more energy to split water than the amount of energy you can get from burning the hydrogen gas. That pesky 2nd law of thermodynamics cannot be ignored.
Yep. That’s why I believe we’ll never seen hydrogen powered personal vehicles. The fuel cost of electricity will always be cheaper. There is no way around it. There are possibly applications in long distance trucking/shipping.
There are also some niche applications like perhaps generating dispatchable electricity (which is expensive) by hydrogen made from curtailed renewable sources.
There are also lots of industrial non-fuel applications for hydrogen, like ammonia manufacturing. Currently, most or all of the hydrogen is generated from natural gas. So there is possibility of eliminating that carbon use. Price still needs to come down though.
C&EN is a great publication, I miss it.
We still have the problem that battery weight limits EV power. Battery powered locomotives and heavy trucks are not likely. Hydrogen or derivatives like ammonia or methanol are possible (but expensive).
Do we want green energy or not? If yes, what is the alternative?