We need lots of the gas, and cheaply, if it is to help replace liquid carbon fuels
Jonathan Ford
Workers at a Toyota factory in Japan prepare hydrogen tanks to be placed in the company's Mirai fuel-cell car © AP
Interest in hydrogen as a clean substitute for carbon fuels is surging. Shares in the producers of fuel cells, which convert the gas into electric power, have appreciated mightily over the past year.
Sweden’s PowerCell is up nearly eight-fold, while Canada’s Ballard Power and Plug Power of the US have more than doubled.
Investors are betting on the perfection of processes that turn hydrogen into usable energy. That may be necessary to spur their take-up, but the real challenge lies further up the production chain. It is how to make hydrogen a sufficiently plentiful and cheap resource that it can contribute meaningfully to decarbonisation. Only then will these bets really pay off.
Hydrogen isn’t widely used at present. In Britain, current annual production is about 700,000 tonnes or 27 terawatt hours (TWh) of energy equivalent, according to the Committee on Climate Change. That’s just 1.5 per cent of total UK energy consumption.
High production costs are one reason. Made by consuming hydrocarbon fuels, hydrogen can’t really compete for any application where these are an alternative.
Decarbonisation could change the picture — out of necessity if nothing else. Electricity at present accounts for just 20 per cent of final energy consumption, and not all that other 80 per cent is easily electrifiable. With events such as last week’s judicial ruling against the expansion of London’s Heathrow airport, it is dawning that without a zero-carbon liquid fuel substitute, eliminating emissions may involve potentially unpopular behavioural change.
Hydrogen is certainly an option to power such areas as heating and transportation. But to help materially in getting to net zero emissions by 2050, the CCC estimates that it will need to supplant a big chunk of the 80 per cent of Britain’s energy that comes from gas or liquid fuel.
In the body’s so-called “full hydrogen” scenario, demand balloons from today’s 27TWh to 700TWh.
Where is that hydrogen to come from? It won’t be from hydrocarbon feedstock without carbon capture and storage — technologies that have yet to be deployed economically at scale. Many are therefore pinning hopes on renewable energy making so-called “green hydrogen” using electrolysis. But how realistic is that, given the engineering properties of solar and wind farms?
A major determinant of hydrogen cost is the so-called capacity factor of the generating source.
That’s the power generated as a proportion of the facility’s rated peak power. The problem with renewables is that capacity factors are relatively low, although they have been rising. With solar, for instance, they are about 10 per cent in the UK, and 25-27 per cent in the sunniest places in the world.
To see the cost impact, take two hydrogen production sources. Plant A has a capacity factor of 25 per cent, while for Plant B, it is 100 per cent. That means for each unit of capacity, Plant A is producing only a quarter of the output of the second. Even if Plant B costs, say, three times as much per unit of capacity to build, Plant A’s output remains 30 per cent more expensive, all other things being equal.
Low capacity factors are one reason most current renewables have theoretical production costs for hydrogen in the $4-$6 per kilogramme range, according to research from Eric Ingersoll of the consultancy, LucidCatalyst. That’s well above the $1-$2/kg cost from existing hydrocarbon sources. Unlike capital costs, which can be chiselled down, nature limits the amount that capacity factors can be increased.
Then there is another problem with low capacity factors: the sheer amount of space that plant would take up. Assume you used offshore wind to supply 700TWh of hydrogen. That would require 238 gigawatts (GW) of capacity, assuming a 50 per cent capacity factor. On the basis that you can fit roughly 2.3MW of capacity into a square kilometre, that would require you to fill 104,000 km2. That is 40 per cent of the whole UK land mass.
Of course, technological development will yield further advances in renewables. Remember that costs for offshore wind have fallen 75 per cent over the past seven years.
But alternative sources shouldn’t be ignored. The main one is nuclear. It typically operates at a 90 per cent capacity factor, and is scalable without massive land use. The key is capital costs, which have historically been too high.
How far these can be shaved by advanced reactors and manufacturing processes is open to question. But China has driven capex down to about $3,000/KW at which level it could be feasible to produce hydrogen at about $2/kg. So far, however, nuclear has been largely overlooked.
Decarbonising liquid fuels is an enormous challenge; too big to place all our chips on one technology. We must explore all the available options, or learn to live with fewer substitutes for ubiquitous liquid fuels.
0 comments:
Publicar un comentario