I’ve been reading in theUK’s Daily Telegraph newspaper in the last couple of days about the troublesome position the UK’s wind turbines are in. As well as being noisy and (according to some) ugly, there are big problems with managing their power output. Apparently, the average wind turbine is shut down for about 25 days each year because it is too windy. The problem is not that the turbines are in danger of damage – it’s because supply of electricity outstrips demand. On a windy summer night the generating capacity of the turbines can exceed the consumption of power.
Ideally, this extra energy would be stored and then released when it was required, but there is very limited potential for doing this. This is one of the major issues holding back some of the greener forms of power generation. For example, with solar power, there is great generation potential during the middle of a sunny summer day, but, in many countries, the power consumption is going to peak on a cold winter evening. How do we keep hold of that energy in the meantime? On a small-scale it can be done with batteries, fuel cells,supercapacitors, etc., on a larger scale withpump-storage hydro-electric schemes, but on the kind of scale needed to exploit renewable energy fully, we are lacking cost-effective options. In the meantime, the turbines need to be turned off so they don’t overload the grid on windy summer nights.
Then there’s also the issue of justhow much greenhouse gas is produced during the construction of a wind turbine, but that’s another story.
You’ve missed one significant alternative to energy storage and that is the idea of a supergrid to distribute energy across long distances. Weather patterns across the European continent vary hugely at any given moment and several studies have demonstrated the feasibility of transmitting power from areas where the wind is blowing / sun shining to areas where it isn’t. There are more radical proposals as well which require renewable energy to be generated in “hotspots” such as the coast of Europe, for wind (http://www.independent.co.uk/environment/climate-change/windfuelled-supergrid-offers-clean-power-to-europe-760431.html), or North Africa, for solar (http://www.desertec.org/), where supply is consistent and reliable. This can then be distributed across Europe. The supergrid concept is gaining rapid support across Europe and the UK is now considering laying a cable across the North sea to carry excess output from UK turbines or to supply excess capacity from the continent when appropriate.
http://www.guardian.co.uk/environment/2010/jan/03/european-unites-renewable-energy-supergrid
Obviously, the potential for supergrids to mitigate the intermittency of renewable energy supply in NZ is limited due to the size of the country and the distance to its neighbours. Despite this, surely NZ’s abundance of geothermal hotspots and epic geography present massive opportunities for energy independence that countries like the UK can only dream of.