The (un)reliability of wind power

People who oppose wind power point out that it is unreliable. The wind is unpredictable; there is power available on averagely-windy days, but on calm days and very windy days (when the turbines have to furl for their own protection) there isn’t. We, on the other hand, are used to being able to plug something in and find the power available.

The village of Fladbury, near Evesham in Worcestershire was one of the first in the country to have domestic electric lighting. Power was generated from the River Avon, by turbines fitted into Fladbury Mill.  But as the denizens of Fladbury turned in at night, they turned off their lights and the current drawn fell.  What was supposed to happen was that the turbine operator would see the voltage rise on the voltmeter by the generating shed, and accordingly close the turbine sluices. This wasn’t reliable enough, so instead they put in a bank of electric fires in the turbine shed which were switched on to absorb the current no longer being drawn by the lights in the villagers’ homes.

These days, that complex operation is handled by the National Grid who switch in generators as required, just so as we always have 240 volts at the socket. They do this in response to fluctuating demand; and they will be able to do it with the fluctuating supply from wind power too, but it isn’t very efficient. If there’s a flat calm at half-time on Cup Final day (when there’s always a surge in demand as people put the kettle on), they’ll have to fire up a bank of inefficient generators; but, instead, if everyone switched off their fridge and freezer for the time it takes the nation to brew a half-time cuppa, there would be enough power without firing up the backup.

Smart Meters and Smart Tariffs

Oh, and the laptop could switch to battery, too – just a few watts, but it helps. What we need are smart meters and smart plugs, which tell our devices when to switch off; and the effective way to get us to switch off is to make high-demand electricity much more expensive. After all, it is much more expensive to generate.  The network knows when the demand is going up: not only does the voltage start to drop, but the frequency changes: as the generators have to work harder, they slow down, and the current alternates at slightly less than fifty cycles a second. Modern electronics can easily detect this, so smart meters (and smart tariffs) should charge more when the frequency starts to fall – and less when it’s running free.

Smart Plugs and Smart Devices

So a smart plug, or a smart device, will know from the frequency of its electricity supply the price of the power it is using.  Freezers, say, could be programmed to draw current if either the price of juice is below a certain point, or the temperature inside the cabinet is getting too high; and laptops would charge up when the juice is cheap or the battery is really flat and needed urgently.

Electric Cars

There’s a good chance that when we replace our current car in a few years’ time we’ll buy an electric one rather than a diesel one. Most cars spend most of their lives parked up, and if they were electric they could be plugged in. Cars, unlike laptops, have big batteries.

Let’s say an average electric car has a battery capacity of 25kWh. There are about 25 million cars on the UK roads, so were they all to be electric (in few decades’ time), there would be 625 GWh of storage capacity available to the network. OK, so not while they are actually driving, but let’s assume that half of them are driving while the other half are parked up and charging (it’s probably much less than that). So that gives the network, say, 300 GWh of storage capacity.  Current peak demand for electricity is about 65GW, but widespread use of electric cars will increase this – by how much will depend on lots of factors, including how much we use cars rather than public transport or bicycles and the efficiency of new cars; but assuming that there isn’t much further increase in car use, and that  the average efficiency of future electric cars is about the same as the new Nissan Leaf, 15% is a reasonable guess.  Even so, a plugged-in fleet of electric battery cars could provide as much 6 hrs backup capacity for the whole grid: but frequent charge-discharge cycles reduce the life of present-day lithium-ion batteries. Nevertheless, advances in battery technology are now proceeding apace, driven as much by the demands of portable electronics as by electric transport.

All of these technologies reduce the need for instant power now, which makes wind power’s unpredictable variability much less of a problem.


About ejoftheweb

I'm a freelance intellectual property consultant and a self-taught Java programmer with a bee in his bonnet about trust, transparency, liberty-and-liberalism and all things free, fair and open-source. I am at my happiest when I am dancing.
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