Wednesday, 3 March 2010

Miracle Energy

More than one "alternative energy" subsidy scam, I mean electricity generation project has emerged from the cracks in the floorboards in Ireland in the last year. The most prominent of these has surely been Spirit of Ireland (sounds inspiring doesn't it), but there is at least one other I have seen.

What are they about? I'm glad you asked. You see they make FREE ELECTRICITY, by "harnessing the natural wind resources of Ireland" or somesuch nonsense. In the world of sensiblespeak they use wind turbines to pump water into reservoirs which then generate hydroelectricity. OK, it is a batch of windmills connected to a big battery.

Sounds great. If you don't dig too deeply. Let's do that.

Our starting point is that wind generation of electricity is a complete waste of time. No matter how many windmills you have, you can never have the type of certainty of generation that a modern society requires. Today, we will never accept "sorry you need to be cut off for a while because there is no wind". Nor should we.

Simply put, windmills provide electricity when the wind blows, not when people need it. It is only by random chance that those two conditions occur at the same time. And even a 90% concurrence is 10% too low.

So we need an alternative for when the wind isn't blowing, noting that sometimes there is next to no wind across the entire island of Ireland. In which case we need alternative methods of generation available at all times for immediate supply of electricity. Of course, that begs the question; why have the windmills at all then?


So windmill buffs come up with a weeze. Why not store the electricity generated when the wind blows so it can then be provided only when people need it. A big battery, like a hydroelectric reservoir where we pump the water uphill to be released downhill when electricity is needed.

Sounds lovely, until you try to mount this baby and ride it full tilt down the wrong side of the motorway of the real world.

It turns out that the reliability of wind in Ireland (the windiest place in Europe supposedly) is such that even with massive storage capacity such a combined generation and storage system is still likely to run short of electricity. Don't believe me? I got into a discussion about this hair brained scheme some time ago. I like to check things out for myself so I modelled such a system using data for actual electricity generation yields from the Irish wind network combined with different theoretical stored capacity. This is what I found using data at the time (note, this is from last year, but I didn't cherrypick the time period, I simply took the current month).

The chart below shows how much potential electricity would be stored in such a system with different level of storage capacity; from a pretty hefty 100 Gigawatthours up to a massive 500 Gigawatthours. Just note that 500 Gigawatthours is about enough electricity to keep all of Ireland running for about 10 days. It is alot.

Next I assumed that the reservoirs were full to the brim at the start.

Next I simply calculate how much electricity would remain available to meet demand from households and industry if it was attached to a flock of windfarms with a theoretical 5 Gigawatt output (i.e. if running at optimal generating speed they would generate 5*24=120 Gigawatthours of electricity in one day, at 50% they would generate 60 Gigawatt hours)

We then compare how much such electricity was being generated and how much electricity was being demand across Ireland over the period and can track how much storage would remain over time (it being used to meet demand when the wind wasn't blowing sufficiently strongly).

This was the result:

Even ,with a massive 500 Gigawatthours of storage at the start of June last year, Ireland would have been blacked out by the middle of the month. We would have needed an alternative backup generation system available to meet 100% of the country's needs on top of this very expensive hair brained scheme. So, why bother with the hair brained scheme?

Some people might try and quibble by pointing out that I have simulated how this system would operate meeting the electricity needs of the entire country, when the proposal is only ever to meet a proportion of it.

Well, leave aside the fact that some of these proposals claim we could use this for all our electricity needs, all you need to realise is that this analysis shows that the system could not be relied upon to meet any arbitrary amount of electricity demand on its own. It would need 100% backup.

So again. Why bother with this, when the backup works on its own?

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