Mary Mulvihill

We can’t all install a wind turbine at the bottom of the garden, yet simply changing when we use electricity can make our power consumption greener.

Some years ago, making a science programme for RTE radio, I was let into the inner sanctum where skilled engineers control the Ireland’s electrcity supply to meet the constant rise and fall in demand across the national grid.

There, in a darkened room (the better to see all the computer displays), the Eirgrid engineers work not unlike air traffic controllers.  They have their fingers on the pulse of the nation, and their hands (literally) on the levers of power.

Electricity consumption in Ireland rose steadily over recent years. All those new homes, all those new appliances, all those switched-on lives. So much so that demand was almost outstripping supply, and new power plants were planned.  (It will be interesting to see if peak demand falls over coming months as the recession bites.)

Demand is highest in winter, as you might expect, but not on Christmas day as I had thought.  (Surely, with all those turkeys in all those ovens, all those lights on all those trees? But no: lots of households get together, and more importantly, most industry has shut down.)

No, the worst time — when supply from power plants has trouble meeting demand — is 5-7pm on cold winter week nights. That’s the electric rush hour, when the heating is on and everyone is cooking dinner in homes across the country, and all the power stations have to be brought on stream, including older and more polluting and inefficient ones.

In other words, it’s the dirtiest time for electricity generation.

(And the most expensive: commercial customers may be charged more for rush hour electricity. This is why CERN’s LHC experiment on the Swiss-French border will shut down for three months every winter: particle accelerators are heavy power users, and winter electricity is just too expensive, even for the world’s biggest experiment.)

Power production is cleanest and greenest, on the other hand, when demand is lowest – usually late at night.

So, if you want greener electricity, and can’t install a wind turbine, here’s a simple tip: spread your electricity consumption more evenly across the day, and try to reduce consumption during the peak hours of 5-7pm.

Leave the dishwasher and clothes wash till later, maybe use a microwave instead of a conventional oven, listen to the radio news instead of the TV.

By reducing peak demand, you’re helping to reduce the number of new power plants needed!

You can monitor Irish electricity demand and supply in real time on the Eirgrid website. Here’s a recent snapshot of the system (left), taken on the evening of March 10th 2009.

And at 8.30pm on Saturday March 28th, why not turn off all your lights? And join millions of others around the world in marking Earth Hour.

If enough city dwellers do it, you might even get to see the stars again. And if you can survive an hour in the dark, then you don’t have to turn all the lights back on at 9.30pm!  Fewer lights burning? Think of it as ambience.

And remember: night-time electricity is cleaner and greener.  So, spread the workload, and spread the word.