DR HUGH SPENCER, AUSTROP FOUNDATION
⟼ Hydrogen is an inefficient electricity system
⟼ The Daintree Coast climate is too cloudy to make electricity at scale
⟼ A grid system will be damaging and expensive
Hydrogen – the dream gas that’s going to power the Daintree – only it can’t. Why?
Hydrogen, the answer to all our energy issues, clean, produces only water when burned, and we can run our vehicles on it. We can make it simply by using electricity to break down water and store the hydrogen produced. We can use that to generate more electricity with a fuel cell. What’s not to like?
However, hydrogen for this purpose, faces two insurmountable obstacles that will never go away:
Firstly, the process of making, storing and converting hydrogen back to electricity is about a third of the efficiency of battery storage.
Second, if you want to make hydrogen from solar energy, do it in sunny Boulia, not in a wet cloudy place like the Daintree Coast.
The problem of energy efficiency
So, the first obstacle is the very low energy cycle efficiency. Gasoline or diesel-powered engines are at best 50% efficient, and when running as a generator, the conversion of the energy in the fuel to electricity is about 30% – something it seems we have to live with.
Let’s look at hydrogen, which is being touted as the answer to supplying a continuous electricity supply.
The mechanics of hydrogen power
Conversion of electricity to hydrogen has an efficiency of 70-80% with current technology.
That sounds fantastic, until you realise that to be useful it either has to be burned immediately to produce electricity (so then why bother?) or it has to be stored.
Storage of hydrogen is no simple matter.
Hydrogen is the lightest gas, and even a small amount (say 2 grams) would occupy 22.4 litres at atmospheric pressure and temperature, and would deliver a mere 80 watt-hours (an incandescent light bulb for an hour, assuming no efficiency losses).
If we want to run an upmarket resort that currently uses, say 2400 kilowatt hours per day and allowing for the 60% conversion of electricity to hydrogen, you’d need storage for approximately 1.1 million litres of hydrogen. Multiply this by the needs of the number of commercial establishments and the expected residential users and the amount of gas storage becomes overwhelming.
As an alternative, we can store hydrogen by compressing it. Small carbon fibre – polymer tanks have been developed which can store hydrogen at about 700 atmospheres pressure, so a 20-litre tank could store 14,000 litres of hydrogen. This sounds good-until you do the maths.
Just for our nominal 2,400 KWH resort (such as the now-defunct Coconut Beach) we’d need 78 of these tanks – and that’s for 24 hours of use.
The complexity becomes boggling.
Plus, lest we forget, compressing hydrogen (or any gas) isn’t free (think of your garage air compressor). It is estimated that at least 12-16% of the energy in the hydrogen supply will be used in compression – so that’s another loss.
Where are we up to with hydrogen efficiency?
60% efficiency converting the electricity to hydrogen, 85% efficiency (nominally) in compressing the hydrogen for storage – so we are left with 51% of the energy of our hydrogen still available.
So why don’t we liquefy the hydrogen?
That would drastically reduce the storage volume – but there is an even more ferocious energy costs for that – energy losses involved in liquefaction seem to vary from 40% to 15% (seems to depend on the scale of the operation). Other storage technologies are being investigated, but most are a long way off.
Storage of liquefied hydrogen requires costly insulated containers as hydrogen boils at minus 252C. Cold!
So assuming 70% liquefaction efficiency – we have 51% x 70% = 36% – not looking too good is it?
But wait, there’s more. We still haven’t used the hydrogen to produce electricity, the whole idea of the operation.
There are two ways to use the stored hydrogen:
- either feeding it into a gas turbine that runs a generator, or
- feed it into a fuel cell to produce electricity directly.
Efficiencies (or otherwise)
Again there are costs – fuel cell efficiencies vary widely 50 to 70% figures quoted. So say, 60% of 36% = 21.6% . Pretty poor (OK I’m sure if you were to find the optimum processes, this could be tweaked to 30% – no better than using fossil fuel to run a generator. Our first assessment of efficiency we put at 40% (quoted in the overview), which was rather a “back of the envelope” calculation. Even this assessment doesn’t factor in the considerable energy costs that will be involved in maintaining such a complex facility in this environment.
The second insurmountable obstacle is that the Daintree Coast only gets peak sunshine for a couple of hours a day, we have extended periods of cloudiness (when solar output drops to about 10% of maximum or almost to zero-and these periods seem to be increasing), so such a big power system will require back-up fossil fuel-derived power, or truck in hydrogen from somewhere else.
The Cost of infrastructure
Missing from all this is the complexity, and cost, of the infrastructure required (which will have a pretty big carbon footprint). We haven’t even mentioned the array of solar panels needed to power the whole shebang. I won’t bother to try to calculate the size of the array, as the expected energy requirements are very hard to determine. It will be huge.
Plus, it will need a trained staff (who will need housing etc), as this is a technologically very complex system. And, this is a very cruel environment for modern technology.
Hydrogen is certainly not looking like a “green winner” and a very costly and disruptive one at that.
Which is why the only logical, simpler and vastly cheaper option is to upgrade residents’ and business stand alone systems to use as much solar and battery storage as possible and to encourage efficient energy use. Stand alone systems means the solar panels are largely on user’s roofs, not sterilising landscapes.
This avoids a host of thorny issues which would be very detrimental to the area. It is far more energy-efficient, as batteries (storing solar energy directly) are about 90% efficient, are very reliable and there are no environmental disruptions involved.
Plus, for businesses using solar, this is a great selling point!
Estimating The Carbon Footprint Of Hydrogen Production by Robert Rapier, Senior Contributor, Energy. FORBES
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