“Carbon capture and storage: Fundamental thermodynamics and current technology”, Shannon Page, et al, Energy Policy, 37 (2009), pp 3314-3324
New Zealand’s energy system is pretty unique. We’re isolated and can’t trade electricity with anyone else, we’ve got more hydro than nearly anyone else, geothermal’s big here, and we’ve vast amounts of coal that we’ve yet to dig up. Oh, and governments that have varied between big state projects and market fundamentalism.
So it’s no surprise that there’s lots of research on our energy system. In fact, there’s a special issue of a journal called Energy Policy devoted to NZ (September 2009 issue). I’m reading through this, as the work tails off from my current project (Project “Jump into the Firing Line”). I’ll be looking at a couple of the articles in detail, as they’re fairly key to where NZ can go with energy (and they’re not online for free, so it’s not like many people can just go and read them).
First, carbon capture and storage.
We burn five billion tonnes of coal each year, making for more than a third of our carbon dioxide emissions. Given that we need to cut our greenhouse gas emissions by at least 20% by 2020, in ELEVEN YEARS TIME, we can’t keep burning coal like this.
Then again, coal is the world’s number one source of electricity. More than a quarter of the world’s electricity comes from coal. We can’t just switch that off without the lights going out, and we’ve made major investments in coal-fired power stations. NZ’s only coal-fired station, Huntly, makes 17% of our electricity, and gives us a gigaWatt whether it’s raining, windy, or not. And even if we could replace those with renewables overnight, those power stations cost maybe trillions of dollars, we don’t want to just throw them away. So what’s to be done?
The solution put forward is carbon capture and storage. You just pluck the carbon dioxide out of the burnt gases and bury it forever. After all, we can pull the sulphur out and stop acid rain, right? So it all seems pretty simple, put a capture unit on the tailpipe of your coal-fired power station, bingo, we can keep using coal, not throw away all those old power stations, and all will be shiny bunnies.
(Storage – burying it forever – is easy. It’s the capture that’s hard. Relatively.)
If it works, we can also apply it to gas stations, and to coal-to-petrol plants. Hell yeah! Fossil fuels forever, without screwing the climate. So as you can imagine, there’s a huge amount of research going into this right now. It’s eminently feasible, with a bunch of different methods. They all work, they’re all too expensive, but hey, scale them up, mass-produce them and the cost comes down, just like with wind turbines.
So, what’s the limiting cost? It turns out to be the amount of energy that you need to run them. That energy comes from the coal-fired station itself. Obviously, if it takes 100% of the energy from burning the coal to clean the exhaust, then you’re not onto a winner. If it takes 1%, you’re laughing. Industry predictions are that it will take 25%, pushing prices up by a third.
Unfortunately, a bunch of Uni of Canterbury engineers have had a dig through the thermodynamics. Surprise, surprise, the industry figures are not just optimistic, but based on underlying data and assumptions that haven’t been published, can’t be checked, and frankly, aren’t worth the paper that they’re written on. They think a limit on the efficiency of CCS is more like 37%, pushing up prices by 60%. And that’s for the idealised case, in reality it will be more.
That starts to make carbon capture and storage look seriously dubious. If coal power costs two-thirds more, then the future for coal is pretty bleak. And you can’t fight thermodynamics.