Power shares

[Snoopy]

The puff that is supplying that 30-40% load factor sounds more like my 'locomotive breath' scenario. It strikes me that if a warm or cold front takes 2-3 days to pass over then those windmills will not be running 'flat chat' for 2-3 days. It seems to me as though this 30-40 percent 'average' is more likely made up of a few hours at 100% but most of the spinning time spent at maybe 10 or 20% energy generating capacity (remember when the wind speed halves from peak, then the energy generating capacity if a windmill falls to just one quarter of peak). Thus modelling wind energy based on 30-40% capacity does not mean the wind farm is producing maximum energy 30 to 40 percent of the time. Maximum energy production might only occur just 10% of the time and with a wind energy generation model that applies a random walk around that peak, you could still get to that 30-40% load factor. If the true peak is relatively short in duration, it should be possible to accommodate that with a hydro-reservoir with a storage capacity of just a few hours.

After doing some more reading, it strikes me that I am looking at integrating wind farms into the wider power grid the wrong way. I had assumed that when a front passes through, all the wind turbines in a particular location will behave in roughly the same way. Hence my concentration on what is happening to individual turbines. However, on reading page 160 of the reference below a different picture emerges.

https://www.wind-energy-the-facts.or...s/chapter2.pdf

Variations within the Minute

"The fast variations (seconds to minute) of aggregated wind power output (as a consequence of turbulence or transient events) are quite small, due to the aggregation of wind turbines and wind farms, and hardly impact the system."

This is telling me that those fast acting 'gust spikes' I was concerned with are not an issue, because the same 'gust spikes' are not acting on every windmill in a windfarm at the same time.

Variations within the Hour

"The most significant variations arise from the passage of storm fronts, when wind turbines reach their storm limit (cut-out wind speed) and shut down rapidly from full to zero power. However, due to the averaging effect across a wind farm, the overall power output takes several minutes to reduce to zero. And in general, this is only significant in relatively small geographical areas, since in larger areas it takes hours for the wind power capacity to cease during a storm. For example, in Denmark – a small geographical area – on 8 January 2005, during one of the biggest storms for decades, it took six hours for the installed wind power in the West Denmark area to drop from 2000 to 200 MW (5 MW/minute)."

'The passage of a storm front can be predicted and technical solutions are available to reduce the steep gradient, such as the provision of wind turbines with storm control."

From what I can figure out from this power station map:

https://ens.dk/sites/ens.dk/files/An...201907_eng.pdf

the wind power in 'West Denmark' gets around 50% of their wind power from the offshore 'Horns Rev I II and III' wind power stations. These three are all located over a 50km stretch of ocean. So even in a severe storm, these windmills took several hours to shut down. The New Zealand wind farms are generally not as far spread out as this. But this is telling me that in the New Zealand situation, we might expect the full ramp up or ramp down of a distributed windfarm system will take a matter of hours, not minutes, even in the most severe weather situations. In this context, matching a southern windfarm portfolio, spread out more than 100Km across the lower South Island :

1/ Mahinerangi Wind farm (Mercury Energy 36MW)
2/ Mt Stewart Wind farm (Pioneer Energy 7.65MW)
3/ Flat Hill Wind farm at Bluff (Pioneer Energy 6.8MW)
4/ White Hill Wind farm (Meridain owned) 58MW

with a storage lake system of modest capacity, like Contact's Roxburgh and Clyde dams, looks do-able.

SNOOPY