Hacker News Reader

Comment by natmaka | Hacker News Reader

AFAIK this is good because some renewable energy sources cannot produce continuously (solar, wind), and therefore storing their production is a major challenge. As stated in this article generating hydrogen can be done with electricity. Moreover fuel cells may also power trucks and even cars.

View on HN

The main issue is the overall efficiency of the process. Creating hydrogen by electrolysis is about 80% and then a fuel cell electric efficiency is 60-70%. So overall the whole process is not very good.

How's the energy storage density on Hydrogen though? One of the main problems with Lithium is it's heavy and requires a lot of space to store energy.

I think that you can get good energy density with Hydrogen which will allow long train journey, but this will degrade further the overall efficiency as high compression of the gas is needed, and this energy is likely lost during usage.

Extremely good for weight and extremely poor for volume. To reduce the gasses volume storage is usually either highly compressed (200-700bar) or cryogenic (30K), like in the space shuttles tank.

In both cases the volumetric density is still quite poor, cryogenic is about 70g/l, which is actually less than the weight of hydrogen chemically bound in a liter of gasoline.

There exists some concepts of storing hydrogen chemically bound, e.g. to hydrocarbons or metal hydrites which release the gas on high temperatures (100-200°C).

Formic acid might be a possible solution for the volumetric capacity problem, although it is still very much in its infancy. See [1].

[1] https://news.ycombinator.com/item?id=22449894

How is better than methanol?

Other parameters: a renewable energy source produces without any combustible, risk, or pollution/waste.

Even 48% of a no-string-attached gift is a gift.

There are a lot of sectors looking at hydrogen from excess renewables, some of them will require huge quantities (e.g. low-carbon steel production). And to start, the very first thing to do with hydrogen produced from excess renewables is to replace the industry-used hydrogen that currently comes from natural gas.

I think hydrogen will play some role in the future, but it should really only be used where no other, more efficient technology is available. For trains a well established technology is available: Electric trains with overhead lines. Use that.

Efficiency is a parameter. There are other ones. An energy source able to continuously produce without any combustible, pollution, running cost, waste, risk... would indeed be adequate and supremely efficient.

Waiting for this miracle, we have to store energy.

Reply on news.ycombinator.com