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