More Dams: Why Not?

Hydro power has been used as a stick to beat the left for years, fairly ignorantly it turns out. As recently as last week, luminaries such as Piers Akerman, renowned hydrogeologist and power-systems engineer have been hoping to wedge the left by pointing out their perceived hypocrisy. The old adage goes: If the left were really serious about addressing climate change, they would dam the country to capacity, and power our economy to hydroelectric, zero emissions victory!

There are three major errors bundled into this statement, all easily disproved. I’m surprised Piers’ engineering training hadn’t led him to these conclusions himself, given how confidently hydro is supported, calling it “the only real alternate source of renewable energy”.

For starters, the renewable and sustainable credentials of large-scale hydro-electric power are very much in dispute. From a sustainability point of view, the problem is methane. Dams require large areas of land to be flooded, usually containing plant material. The water excludes oxygen, and causes the plant material to anaerobically decompose. Anaerobic digestion leads to methane emissions and methane is a powerful greenhouse gas. The maths of the comparison are complicated, but lowering CO2 emissions by emitting more methane, which is 20 times more potent as a greenhouse gas, is a pretty risky strategy.

The argument over whether damming a river is a renewable energy source is debatable too. I assume in this case Piers is referring to how wonderfully dispatchable hydro power is. One literally just turns on the tap and electricity comes out. But, obviously, rain is required for there to be any water to let out. Even really wet places run out of water and therefore run out of electricity. The Basslink DC cable from Tasmania to the mainland was built to transfer the abundant hydro power they had and make some money in the NEM. However, it stopped raining, and rather than exporting, Tasmania imported 70% of their electricity in 2007. For the same reasons that “more dams” is not a suitable potable water supply policy option, more dams will not guarantee our electricity supply.

How much capacity are we talking about anyway? If we built every single dam available to us in Australia, how much electricity could we produce? The current best estimate for “technically feasible” (at any cost) hydroelectric power in Australia is 60TWh annually. In 2009-10, we used closer to 240TWh, about four times the total hydro power available.

So can hydro-electricity power Australia? Not really. Is it renewable anyway? Almost certainly not. Are there actually low carbon alternatives? Absolutely. And I’ll get to them in future posts.


About evcricket

Extreme gardener, engineer and bird nerd. View all posts by evcricket

4 responses to “More Dams: Why Not?

  • Mark Duffett

    This leaves aside that hydro is arguably still the best way of *storing* intermittent renewable energy, though. And presumably the ‘complicated’ maths of the comparison incorporates the fact that methane is much less long-lived in the atmosphere than CO2. As I’ve only half-jokingly noted previously, a solution to the latter issue would be to completely raze and feed all the vegetation into biomass generators before filling the impoundment.

    • evcricket

      Sure Mark, pumped hydro is a still a good way of storing power and you are no doubt aware that there is already about 8GW of pumped hydro in the NEM, at Bendeela, in the Snowies and Tassie. However, the requirements for pumped hydro are tighter than regular hydro, and papers I have seen estimate that there are *three* sites remaining that are suitable for pumped storage, two of which are in the middle of World Heritage Listed national park in Tasmania. Also, all the normal stuff about it raining still holds.
      You are also probably aware that the “20 times stronger” figure for methane is the IPCC figure for 100 year effect. Over 20 years, which is about how long methane lives, it is more like 150 times more effective than CO2. See? The maths is complex.
      Your solution of removing the biomass is not novel, and has been applied in parts of South-East Asia. I visited a site in 1998 which was “earmarked” for a dam; so in came the loggers. Yet, after that the planning committee changed their mind and all they were left with was an utterly denuded valley. While obviously not a reason not to pursue hydro, it is an interesting if somewhat perverse outcome.

      • Mark Duffett

        Thanks Ev, hadn’t been aware of that particular subtlety about methane, nor the aborted impoundment in SE Asia.

        Only three remaining sites suitable for pumped storage in Australia? Better tell PV guru Andrew Blakers, he seems to think it’s a non-issue:

      • evcricket

        “Thousands of suitable sites”. Hmmm. That is “surprising”. Maybe Professor Blakers has seen some research I am not privy to? Or perhaps he is being a little, dismissive.

        In either case, I don’t really think pumped hydro is the linchpin for renewables. There are plenty of other ways to skin that particular cat. Which, I’ll get to.

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