Geothermal (17 per cent of New Zealand's electricity) is a renewable system not reliant on the weather. Hydro (59 per cent), whilst dependent on rainfall, has storage in the form of dams. In this country, hydro provides the vast majority of the daily, weekly and monthly peaking requirements for Kiwi consumers.
There is one feature in New Zealand's energy mix that requires persistent management: Seasonal energy storage. It's when you need back-up energy for several months to manage a South Island drought which reduces hydro generation.
This is currently managed by water storage behind the dams in the first instance, then flexible natural gas production, followed, if required, by very limited coal use (on average only 3 per cent of the country's generation mix).
However, like batteries, hydrogen will not viably solve the seasonal energy storage requirement because it cannot be stored in any serious quantities.
To remain in liquid form at 200C below freezing, large volumes of hydrogen require one seriously large thermos flask. Think of more than two thousand Olympic swimming pool-size thermos flasks to store energy equivalent to New Zealand's hydro energy storage.
Hydrogen can be compressed but that still requires a large thermos flask with the addition of very, very thick walls. And yes, hydrogen can be stored as ammonia, but the round-trip efficiency on that chemical journey requires more equipment and is way more expensive. So hydrogen cannot claim to solve the need for back-up seasonal energy storage in New Zealand.
Hydrogen is not needed to solve regional differences for power either. Nothing beats transmission via New Zealand's efficient, already established, national grid overseen by Transpower. There are less electrical losses from a hydro station in the South Island to an Auckland three-pin power socket than from a solar panel on the same roof.
To summarise: New Zealand has very limited intermittent renewables risk, effective regional coverage and much cheaper forms of seasonal storage.
Domestically, hydrogen will have limited commercially viable applications. It is suggested for transport, but here's the science.
If you start with 100 units of electricity at a generation site, about 80 per cent of that energy will move the rubber on the road using an electric vehicle.
If you take the same electricity and turn it into hydrogen, compress it, distribute it and use a fuel cell vehicle, less than 25 per cent of the original energy is left by the time it hits the road. This is less efficient than a petrol engine.
This means that to use renewable hydrogen to "turn the tyres", the electricity sector will need to build more than three times as much new generation than if the electricity was simply used directly through electric vehicles.
That unnecessary expansion could be great for power companies and equipment suppliers, but it's not in the interests of New Zealand and its citizens.
Stated in another way, renewable electricity costs the equivalent of 30 cents a litre for transport, but going from electricity to hydrogen and then back to electricity again will be at least three times more expensive.
Hydrogen could have a place in our economy. The place for it is in a way that leverages our renewable energy advantage to the world: Where we look at hydrogen as a way to transport energy created here to a country with a significant energy deficit, such as Japan.
This hydrogen opportunity, in effect, becomes an "electricity cable to Japan" through which we can obtain export revenues based on our largely renewable energy resources with a key trading partner.
Interesting as all of that is, there is a much larger principle signalled in Cam Hosie's article that is getting in the way of the big challenge of reducing emissions to address the human contribution to climate change. He concludes that, "We need to use every tool at our disposal". This is precisely what will prevent us from solving global emissions reduction.
We have limited time, limited people and limited money to address the challenge in front of us. If we spray and pray at everything, humanity will almost certainly fail at this challenging task.
Rather than use every tool at our disposal, what should be demanded by Kiwis is that decent scientific and commercial rigour is applied by Governments, businesses and NGOs to genuinely do things that will make a difference. Not to be "seen to be doing something" that might appeal to voters, consumers or members respectively.
A signal without substance is greenwashing, and the fastest and most expensive way to a hot planet.
Fraser Whineray is chief executive of Mercury.
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