Prospects for Hydrogen

What are the prospects for hydrogen as part of a sustainable, green economy?

Hydrogen is perennially spoken of as a fuel of the future- clean, renewable, light. It is particularly appealing in an environment (like that of California) where solar energy is having a huge impact on the grid and causing rising portions of solar production to be "curtailed". That is, turned off. But even in California, solar power has hardly scratched the surface. Only few roofs have solar and the potential for more power production is prodigious. Over time, as more renewable sources of energy come on line, the availability of excess power at peak times will rise dramatically, prompting a huge need for storage, or other ancillary uses for excess power. Many storage schemes exist or are under development, from traditional water pumping to batteries, flywheels, gravitational weights, etc. Hydrogen is one of them, spoken of as a versatile storage and fuel medium, which can be burned, or even more efficiently put through fuel cells, to return electrical power.

A typical day on California's electrical grid. The top teal line is total demand, and the purple zone is power not supplied by renewables like wind, hydropower, and solar. During the mid-day, most power now comes from solar, an amazing accomplishment. Roughly 2 GW are even turned off at the highest peak time, due to oversupply, either locally or regionally. How could that energy be put to use?

Unfortunately, as a fuel, hydrogen leaves much to be desired. We have flirted with hydrogen-powered cars over the last couple of decades, and they have been a disaster. Hydrogen is such an awkward fuel to store that battery-powered electric vehicles have completely taken over the green vehicle market, despite their slowness in refueling. The difficulties begin with hydrogen's ultra-low density. The Sun has the gravitational wherewithal to compress hydrogen to useful proportions, at the equivalent of 100,000 earth atmospheres and up. But we on Earth do not, and struggle with getting hydrogen in small enough packages to be useful for applications such as transport. The prospect of Hinden-cars is also unappealing. Lastly, hydrogen is corrosive, working its way into metals and weakening them. Transforming our natural gas system to use green hydrogen would require replacing it, essentially.

The awkwardness, yet usefulness, of (reduced) hydrogen as an energy currency in an oxygenated atmosphere is incidentally what led life during its early evolution to devise more compact storage forms, i.e. hydro-carbons like fats, starches and sugars. And these are what we dug up again from the earth to fuel our industrial, technological, and population revolutions.

But how useful is hydrogen for strictly in-place storage applications, like load balancing and temporary grid storage? Unfortunately, the news there is not good either. Physical storage remains an enormous problem, so unless you have a handy sealed underground cavern, storage at large scales is impractical. Second, the round-trip efficiency of making hydrogen from water by electrolysis and then getting electricity back by fuel cell (both rather expensive technologies) is roughly 35 to 40%. This compares unfavorably to the ~95% efficiency of electrical batteries like Li ion, and the 80% efficiency of pumped water/gravity systems. Hydrogen here is simply not a leading option.

Does that mean we are out of luck? Not quite. It turns out that there already is a hydrogen economy, as feedstock for key chemical processes, especially ammonia and fertilizer production, and fossil fuel cracking, among much else. Global demand is 80 million tons per year, which in electrical terms is 3-4 tera watt hours. That is a lot of energy, on the order of total demand on the US electric grid, and could easily keep excess power generator's hands full for the foreseeable future. Virtually all current hydrogen is made from natural gas or coal, so the green implications of reforming this sector are obvious. It already has storage and pipeline systems in place, though not necessarily at locations where green energy is available. So that seems to be the true future of hydrogen, not as a practical fuel for the economy in general, but as a central green commodity for a more sustainable chemical industry.

• Unions
• Afghanistan, inexorably going back to the Taliban.