Power to the People

On March 28th, the Greenies were encouraging everyone to switch off their lights for an hour at 8:30pm local time. There was much press headline tokenism like the Piccadilly Circus Coca-Cola sign being switched off, but when it came down to it, I suspect not too many people were bothered.

Tom Paine of Last Ditch put up some figures for American electricity demand which didn’t seem to show much impact on electricity (lack of) consumption. He asked if there were figures available for the UK and as I have looked into that sort of info before, I decided to see if there was.

Unfortunately, the National Grid website had a problem and whilst it normally shows real time and recent historic data, it was unable to provide anything useful at the time (and is still broken for anything other than 60 minute figures). They do publish historic demand data however, and today I was able to download half hourly figures for January to March 2009 in the form of a Microsoft Excel spreadsheet. (Last time I had checked it was only up to February).

It took me some time to get my head round what the information was telling me as there are four sets of figures showing the total added up in different ways. There are also related figures for storage and import/export of power between us and the Republic of Ireland and France. (It is mostly imported from France, as they have extensive nuclear capacity). Also of interest in another sheet of the document is a list of the various types of generating capacity, rather a lot of it gas &/or oil. In the end, I worked out that three of the four sets were essentially the same characteristics, the fourth also showing the early morning pumping storage going on.

Now storage is a misnomer, as it actually means consumption of power in order to pump water up a hill so that the kinetic energy gained can be reclaimed at short notice by using hydro-electric power (at significant efficiency losses). Indeed, it takes a Megawatt of power just to keep one of the six large 290 Megawatt Dinorwig turbines spinning using compressed air so that it is ready to go to full output in seconds. The pumped storage stations are like the large weights on the bellows of a church Organ, there to keep the wind at a constant pressure regardless of how softly or loudly the Organ is being played.

The National Grid needs to match the available power exactly to demand, which means that some power stations are up and running offline (known as spinning reserve) but not actually generating some of the time (but they could be called upon to synchronise with the grid and start providing power at short notice). Now I imagine that they have a substantial team of forecasters who factor in weather forecasts, Christmas dinner turkey roasting, national events and the like. (The peak maximum demand was reputedly straight after Coronation Street one year, when ten million households put the kettle on during the adverts). BT certainly do similar planning in order to protect their network as otherwise the likes of X Factor voting would result in a severe shortage of successful regular call connections. (BT activate something called “Gapping” for predicted high volume TV or Press advertised phone numbers where the majority of the calls are given busy tone from the local exchange without actually attempting to make the call across the network.)

So, having the peak load figures available in thirty minute increments, are we able to see the impact of Earth Day? Well the graph below shows the the power demand for three successive Saturdays in April for the full twenty-four hours. Power demand rises steadily from 6am -8am and remains reasonably flat during the day until teatime, peaking at 6pm then slowly falling off back down to base load as the evening goes on. The three curves are a very similar shape although it is noticable that the first date is higher than the second which is higher than the third. (I imagine this is down to weather as the seasons progress).

demandI make no apologies for the lack of polish in this graph, it is pretty much a raw Excel graph knocked up quickly whilst I was eating my lunch.

I have highlighted earth hour, 8:30pm – 9:30pm. I have to say that I cannot see any discernable obvious dip for the figures then at all. In some ways, this is to be expected, the sort of people who would have taken part would probably have energy saving lamps anyway and they were only encouraged to switch off lighting, not the main switch in the fuse box. Conversely, there were probably a number of curmudgeons who went through their houses turning all of their lights on just for the hell of it.

The Grey family were driving along the M3 heading back to Ealing for earth hour. I can’t say I noticed any vehicles driving without lights, fortunately!

The published data is quite interesting to analyse and has a wealth of data there, although the explanations are somewhat arcane to the point of being almost incomprehensible to an industry outsider. The graph is based on the IO14_DEM column (which excludes storage pumping and exports) and subsequent Saturdays were chosen because Sundays have a slightly different load peak pattern.