I grew up on an island where you had to gather/generate/grow everything yourself, which has given me a bit of an interest in alternative methods of supplying electricity (amongst other things). After reading the thread “Is it time we went nuclear?” I’ve been having a bit of a think about the power generation shortage we currently have here in NZ, and might have an idea for part of the solution.
Despite the initial damage done to the environment for the reservoir, I’ve always been a bit of a fan of hydro. Thing is, it’s pretty hard these days to find a whole valley you can flood just to build a new dam. Hard work to convince a farmer to give up his land, or the greenies to let you flood a national park. And let’s not even start on the hassles of resource consent.
But what if the dam is already there? What if you have already flooded the valley/moved the farmer/appeased the greenies? As it happens, there are 10 dams around Auckland alone – 5 in the Waitak’s, and 5 in the Hunua’s.
These are the dams that supply most of the drinking water for Auckland – around 315,000 cubic meters a day, or an average of around 3.5 cubic meters a second. Why can we not put a turbine in each of the supply pipelines?
By way of comparison, the power station at Manapouri uses 80 cubic meters a second to produce 945MVA, so we aren’t talking the be all and end all solution here, probably only around 40MVA directly from the dams around Auckland by my rough (and amateurish) calculations. But, there are some quite nice benefits to it.
One is we are using a source that is already there, it’s not like we are taking water from another purpose – merely borrowing it for the length of time it takes to spin a turbine. There’s next to no environmental impact (compared to other methods of generating electricity), you won’t need to run power pylons the length of the country to transmit the power (as it’s generated right next to where the demand is), and the best bit is you can use the same water more than once.
According to the Metrowater website, there are 51 reservoirs around Auckland. Not all of these would be suitable for power generation, but there are quite a few “header tanks” on the tops of hills that you could plumb a turbine into. Mt Eden, St Johns, etc. And that’s just Auckland. Why not also put one on the reservoir on the hill above Tokoroa? Or any other town/city around the country?
I’m not talking a major hydro scheme here, just lots of little ones, so that shouldn’t reduce the pressure/flow in the pipes by too much. Just put them everywhere you can, some sort of standardised design, purchased in bulk, monitored centrally.
It wouldn’t replace our main stations, but it would provide small amounts of power all over the show, next to where it is actually needed. Plus, a lot of our power demand is tied in to water usage. For example, early mornings, when people are having showers for work, you’re generating power to compensate for all the hot water cylinders kicking in. Sunny weekends, when they’re doing the laundry. They’d be both drawing water and generating power.
So, why hasn’t Metrowater or Watercare clicked to this “untapped” source of water? What have I missed?
Note: all figures were obtained from the Watercare, Metrowater and Meridian Energy websites. My calculations as mentioned are rough and amateurish at best. But I do think the idea is sound.
Perhaps someone could offer input on how efficient lots of small turbines would be in comparison to one large one. Or how feasible it is to have lots of small generators adding power back into the national grid (I’ve heard of people producing power privately and selling it back to the grid, so it must be possible). The only hiccup I can see is efficiency – generally speaking, a turbine needs a high rate of flow rather than just sheer pressure or volume. But there are systems that would work on lower flow rates, they might just not be as efficient.
So, what do you all think? And who wants to go in to business with me manufacturing the turbines?
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Originally Posted by Jantar
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