Sustainable Energy NZ #2 – How much dam energy is there anyway?!

Welcome to the second post in the Sustainable Energy without the Hot Air – A New Zealand Perspective series. Today we’ll be crunching the numbers on hydroelectricity potential in New Zealand. For the background to the work and an explanation of the methodology, please visit our last post here. Remember that we are looking for around 55 kWh/d/p from renewable sources to replace what we currently use today. So, with that, today’s post!:

At the moment, ~15kWh/d/p of New Zealand’s energy comes from hydroelectric generation. How much more is feasible? For the United Kingdom, MacKay simply does back-of-the-envelope calculations, but because of widespread hydro-electrical use in New Zealand, there are reports that allow us to make a more complete assessment of hydroelectric potential. [8k8vf25] and [9nvw27h]. Firstly, I discount any scheme that would be in a National park, or protected by a strong Water Conservation Order (e.g. Motu), or extremely remote. Some 34 schemes of >20MW capacity have already been identified as economically and technically feasible (e.g. Mokihinui River). These deliver a potential of 10kWh/d/p. on top of the 15.4kWh/d/p already commissioned. 26% of that is from North Bank Tunnel project in the Lower Waitaki and a further 22% comes from four possible schemes on the Clutha River.

A further 289 sites have been investigated for schemes of >0.5MW and <20MW. Together these smaller schemes have a potential for 10.5kWh/d/p, though only 3kWh/d/p is estimated for schemes that are economic at today’s prices.

What about micro-hydro? The potential for such schemes isn’t easy to estimate but an EECA report1 estimated this at about 600-700MW which would provide about 3kWh/d/p, at an assumed average of 50% peak flow. With an electricity cost of $0.15–0.30/kWh, these are attractive options for off-grid users.

In summary, a maximum realistic potential for a range of hydro options is around 23kWh/d/p beyond existing capacity. However, we must recognise that there are significant economic, environmental and social costs to realising hydro potential.

MacKay also makes a good case for using hydro schemes to balance variability in the wind and in demand.

Conclusion: To achieve energy goals based on renewables we cannot ignore hydro-potential, especially on rivers already committed to hydro-energy production.

Further Reading:

UCSD Professor Tom Murphy from Do The Math does a similar set of calculations for the hydroelectric potential at a global scale.

  1. no longer available, but authored by Ralph Sims in 2006 for EECA, and entitled: “Fact sheet 6: Small hydro. Energy Efficiency and Conservation Authority Renewable Energy Fact Sheet” []

24 thoughts on “Sustainable Energy NZ #2 – How much dam energy is there anyway?!”

  1. Hi Oliver and Phil,

    One general remark / request, if I may: I find the red and green bars MacKay uses in the side bar, very helpful. The ones he extends chapter by chapter. Do you think you could add these as well?

    Re. Hydro
    Is it realistic to assume all 34 schemes could be implemented, given in particular the “huge social and environmental costs”?

    As you point out, the micro hydro schemes will likely be used mostly by off-grid users. That makes it hard to calculate their per capita contribution and I would consider leaving them out.


    1. While using MacKay’s approach, we were interested in a slightly different question/angle. If you look at the earlier doc (or later posts) you will see the equivalents (what we can generate and what we use).

      From debate in tearoom, I believe that 2 of the Clutha schemes may be mutually exclusive. Someone more knowledgeable on the river needs to check that report (2nd link). Mokihinui has failed to get consents but future generations may prefer the power (personally I hope not). Having already excluded national parks, protected rivers etc, I do believe the others could be implemented if there was the will to do so. However, our example “plan” (coming later) only includes the top 8 schemes.

      I dont see any reason to exclude micro-hydro. Someone who builds one is likely to be currently on-grid at the moment. There are numerous situations where their cost might well be justified.

    2. Hi D.,

      Thanks for your suggestions. I thought about this as well as I found it useful. Unfortunately when I tried to do this using my (limited) excel skills, I found it exceptionally time consuming and gave up after doing it for a few. If you want to give it a go, check out the spreadsheet here ( copy paste the numbers into a spreadsheet and have a crack at it (or let me know your email – I’ll send you a copy of the spreadsheet).

      Also, if you happen to have a graphic designer/infographic ubermaster on hand, this is the sort of work that would really benefit from some graphical representation. Unfortunately I (/we) don’t have the skills or funds to get something done, so we’re working with this.


  2. The “run of river” scheme I was referring to earlier was the Stockton Hydro scheme

    This on the face of it appears to be a worthwhile project as it can produce 176 GWh of renewable electricity a year

    I am not sure if this is technically “run of river” as it does require reservoirs to be built on the Stockton plateau. however, the environmental impact is minimised as there are not large valleys being flooded, and furthermore it will improve the water quality by removing some of the tailings from the mining processes affecting the Ngakawau River.

    I know the area fairly well and the Charming Creek walkway is a favorite of mine. I’d hate to see this destroyed or damaged and I don’t think this scheme would do that

    This kind of hydro scheme seems to have a lot less impact than the proposed Mokihinui scheme, for example, which would have flooded a wide area of bush.

    1. Andy, I dont want to knock schemes – I just want to put in perspective. 176GWh per year is around 0.1kWh/d/p by my quick calculation (176×1000000/4000000/365) Just not on the same scale as the big hydros.

      1. No of course it’s not “big hydro” but it would supply a good part of the local west coast community with reliable power, which it is missing right now

        1. That’s is all well and good but part of the energy equation is the proximity of the energy source to the consumer. In the case of Stockton, we are talking about a local power source to a fairly remote west coast community.

          If they don’t have their own local energy source then they need to ship it in via pylons, which have transmission losses and have their own environmental and social costs attached

          1. Hi Andy,

            Fair point about proximity to energy sources. Stockton may make sense because as you say it’s a tiny sliver of the population in a remote area.

            What we’re looking at is the scale of the national issue. We didn’t consider the proximity of population centres relative to generation in this paper. You’re welcome to map it out if you want – I’d be keen to see how it looks.


            1. Average line losses in NZ are around 7% and in remote areas can rise to the order of 20%. Local and distributed generation makes a lot of sense in a long and stringy network like NZ.

              To get this into perspective, NZ’s line losses equal about half the output of Huntly power station annually (in my head calculation…). Not all these losses are avoidable but some certainly would be with a more distributed generation.

          2. As I said Andy, I am not bagging good schemes. Stockton sounds valuable, but your original question was why are we preferring wind to run-of-river hydro. And the answer is that we have more generation potential in wind than in small scale hydro. If NZ went significantly down the route of electrification of transport, then we need a hell of lot more electricity generated.

            1. Phil when we talk about the electrification of transport we are probably focusing on light duty passenger vehicles (LPVs), some public passenger transport and hopefully rail. By far the biggest of these are the LPVs. Modelling by Duncan, J., Halliburton, et al (2010) and others indicate that even with very high take up of LPV EVs we are only talking about an additional 7% of demand from EVs at the end of a 20 year period. Which if assuming some kind of normal electricity demand growth is quite small and can easily be accommodated by renewables.

              The critical issue is timing of the EV charging. Left unconstrained most charging will occur during the evening peak (7pm to 8pm) when people get home from work and plug-in. if this occurred it would mean building a lot of expensive peaking generation.

              The answer is to put in place measures that dis-incentivise charging during this period e.g. differential prices (reward charging off peak and punish charging during the peak), remote control via smart meters, smart grids etc.

  3. Any major expansion of South Island hydro will likely need further expansion of the HVDC connection. When Pole 3 is fully operational, the maximum transfer capacity will be 1200MW.

    Having over-capacity in SI hyrdo is not necessarily a bad thing, though. If all of these schemes were developed, you wouldn’t be able to have all of them running at the same time (unless HVDC is expanded), but this does mean that you should have plenty of reserves in case of extended periods where the more variable renewables were below capacity.

  4. Doug, replacing fossil fueled transport entirely by electric does present some challenges (and not just the current state of technology). Our energy use on land transport is about the same as our total renewable generation at the moment. However, the electric motor efficiency would allow us to go the same distance on less energy – but that is still more than the say the remaining hydro potential. There is a whole article on transport use and options coming up. I can see this is going to be popular.

  5. I am not an analyst but have some direct experience with energy issues beginning with Manapouri(and still involved with the ongoing environmental fallout from that scheme).
    Before you start agitating for more hydro please explore the potential of energy efficiency and conservation.
    By my rough calculations replacing five of the most used incandescent light bulbs in every home would save the output from Clyde…imagine what could be saved if we were really serious about following the suggestions of the nice young man on the EECA ads!
    There is little point in more capacity until energy waste is addressed, which will only happen on a useful scale when it is easy to do so, and will only be successful if progressive pricing is introduced to lock in the savings and reward those who made the effort to go easy on the Earth.
    Check out potential energy savings from adopting ‘Dark Sky’ lighting, which also make for safer streets , ecosystem protection and the restoration of our starry skies .
    I would like the goal to be …no new hydro, large-scale wind or fossil-based energy sources, while looking seriously at solar for every building -to begin future -proofing our homes and communities.

    1. pithy, we explore that later in the series. Lighting amounts to about 2kWh/d/p so not a big dent on the 83 we use. All our energy use is about 11kWh/d/p so even 100% efficiency at home alone isnt going to be enough to get us onto sustainable energy alone. However, it would be best to leave this discussion to later in the series when you can see all the numbers.

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