so the goal is to transport renewable energy from the point of production (e.g. coastline for offshore wind) to the point of consumption (e.g. big factory 300 miles from the coast).
what is the cost of doing this? when comparing different technologies. i.e. you can just build a cable and transport the electricity through that, or you convert the energy into hydrogen at the point of production, then pipe that hydrogen gas through a pipeline to the point of consumption. many big consumers can naturally consume hydrogen instead of electric power anyways, for example large steel mills. they require power for heating and reduction, but in both cases, both power sources can be used (for reduction, electrolysis vs. chemical reduction).
it's well-known that the LCOE (levelized cost of electricity) for solar and wind is around 6 ct/kWh (citation needed, i'm citing from memory). so what is the cost of transporting that electric power over 300 miles? according to the diagram, it's 4 ct/kWh over 1000 miles, so probably 1.33 ct/kWh over 300 miles using wires. so it makes a small part of the cost.
meanwhile if you use hydrogen, you have around a 70% conversion+storage efficiency (electric power -> hydrogen, plus storing it in an underground cavern) (source: this paper and german wikipedia about hydrogen storage). so to produce 1 kWh hydrogen, you need 1.4 kWh electricity at the cost of 1.4 * 6 ct/kWh = 8.4 ct/kWh. transmitting it over the pipeline, meanwhile, costs almost nothing, as seen in the diagram.
so in summary, producing+storing+transmitting hydrogen is slightly more expensive than just producing+transmitting electric power, but that already includes the storage cost. for electric power, you need additional batteries which i'm too lazy to write about now. just to give you an idea.
it's mostly material cost, it's described in more detail in the paper. it has nothing to do with economies of scale because we're already installing massive amounts of cables today. there is a connection to the grid level (high-power lines are cheaper than low-powered ones) though.
nah electrical lines have significant losses. iirc from memory, 500 miles transmission over cables, you lose like 30% of your energy. gas leaks but not that much.
Those transmission losses don't have immediate health and environmental costs, though, and even discounting those there'll be conversion losses on both ends (e: for chemical energy carriers) if what we want to get out of it is usable electricity from renewables. Dont take my skepticism for poohpoohing btw, this kind of counterintuitive thinking is one of the more fascinating things about economics. Or maybe I just like to argue :P
I'll look up the paper, this is an interesting topic.
Where did you get the 30%-Figure from?! HVAC-transmission at "only" 380 KV is at about 1% loss, HVDC is even lower than that.
H2 needs to be produced with electrolyses, you lose 30% of your energy with that alone.
it's 12.9% (i think over 1000 miles)
source is the paper linked above