Enough power for 146,000 homes, for less than the price of a Timbit

A big fat zero. That was the price of power in Alberta Wednesday afternoon. AESO

When your neighbour is kind enough to offer you large amounts of free power, what do you do?

Take it, of course. And that’s what SaskPower did on Wednesday.

You’re not really “buying it” if the price is zero dollars. But that indeed was the pool price from the Alberta Electric System Operator, again, for several hours the afternoon of Sept. 25.

And so SaskPower “bought” 146 megawatts, of essentially free power, for several hours. All for less than a Timbit, because you pay at least something for a Timbit. The listed price was $0.

SaskPower was nearly maxed out on its power imports from Alberta Wednesday afternoon. This was at 4:43 p.m. AESO

 

(On Sept. 22 Pipeline Online published an in-depth story on zero-dollar hours on the Alberta grid here: Alberta had free power for more than a day in August, and seven hours last weekend – how does that happen?)

Significantly, Alberta’s interties to both British Columbia and Montana were down on Sept. 25. As a result, they had nowhere else to dump surplus power except for what was sold to Saskatchewan.

So what else was happening on the Alberta grid at the time? First of all, demand was at the higher end, at 10,752 megawatts at 4:43 p.m., according to the Alberta Electric System Operator’s (AESO) minute-by-minute data, published here. But natural gas generation was way down with seven of the largest natural gas-fired generating units producing zero power.

What was producing power was wind and solar – a lot of it. Wind was at 2,806 out of 5,340 megawatts. That’s 52.5 per cent of nameplate capacity. Solar was at 971 out of 1,663 nameplate megawatts, starting its evening decline as the sun goes down. That’s 58.3 per cent of nameplate for solar capacity.

MC is maximum capacity, in megawatts. TNG is total net to grid. DCR is dispatched, and accepted, contingency reserve. This was at 4:43 p.m. on Wednesday, Sept. 25. AESO

 

For eight hours of the day, seven of which were from 11 a.m. to 5 p.m., the pool price was zero dollars per megawatt-hour across Alberta. And then for the eight hours leading up to 7 a.m. on Sept 26, the price was again zero.

In the previous six days, from Sept. 19 to Sept 25, the AESO declared “supply surplus in effect” five times. And curiously, the day before, at 4:25 p.m. on Sept. 24, AESO said there was a “Frequency deviation to 59.88Hz due to sudden loss of generation while islanded.” If the frequency drops too low for too long, it can lead to cascading failures across an electrical grid as key elements separate themselves from the grid to protect themselves from the variation.

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Pattern observed

But back to the zero dollar power – Pipeline Online has observed a pattern in recent weeks when this occurs. Typically wind and solar, or just wind, production is relatively high. It’s not high as in 80 per cent capacity, but often around 40 to 50 per cent. On other occasions when the pool price drops to zero, multiple wind farms cut their output to zero. This happened both Aug. 24 and Sept 21-22.

But on Sept. 25, instead, seven major gas units, six of which are 300 megawatts+ were not producing power to the grid. According to Dispatcho.app, while Sheerness 1, Genesee Repower 1, Nexen 1 and Battle River 6 hadn’t produced power for several days, Sheerness 2 and Sundance 6, HR Milner, and Cavalier 1 spun down around midnight, that morning.

These are the nearly all of the largest gas-fired generators on the Alberta grid. “Steam” refers to former coal plants converted to natural gas-fired. AESO

 

The zero dollar hours tend to occur when there is particularly ample wind on the grid, and and usually, but not always, when demand is low. Solar routinely goes over 80 per cent output. But when wind output is over 39 per cent capacity, there appears to be a correlation. This has even happened at night, when there was no solar, but ample wind and low demand. Another supply surplus was declared at 2:13 a.m.

For instance, from 11 p.m. on Sept. 25 to 7 a.m. on Sept. 26, there was zero solar power, reduced demand, but wind producing in excess of 50 per cent capacity. According to X account @ReliableAB, at 6:38 a.m., wind was at 3,126 megawatts, or 58.5 per cent capacity. At that moment, SaskPower was taking 99 megawatts, although throughout most of the night it was taking 146 megawatts of free power.

And by this point, nine of the wind facilities in Alberta were showing zero output, despite their neighbours running full bore. For instance, Summerview 1 is within spitting distance of Summerview 2, near Pincher Creek. Summerview 1 was showing zeros at 7:17 a.m., having dropped its output to zero at around 2:20 a.m. Summerview 2 was generating 47 out of 66 megawatts capacity at 7:17 a.m. Windy.com showed ample wind across the southern area of the province where wind generation is located. While several facilities were clearly down for an extended time (Cowley Ridge has been down since March) or in commissioning (Forty Mile Bow Island, Halkirk 2), clearly several of these wind facilities had shut off their output around the same time zero dollar hours occurred (Ghost Pine, Summerview 1, Blue Trail Wind, Kettles Hill). If they had remained online, it likely would have further exacerbated the surplus conditions.

The AESO event log provides some explanation. When supply surplus was announced, it also included, “Restatements to reduce zero dollar block volume are now permitted within the T-2 timeframe.” In other words, if you’re offering your power at zero dollars, you’re allowed to pull it off the grid for a certain period of time. More succinctly, there’s too much power on the grid.

Kettles Hill Wind output, according to Dispatcho.app. Its output dropped to zero, despite its neighbour, Summerview 2, running at three-quarters capacity.

 

This begs the question, if there’s commonly surplus power when wind is around 40+ per cent output, what happens when the output is closer to 80 per cent, or higher? Do wind farms drop offline, as clearly took place the morning of Sept. 26?

Or what happens when even more wind farms are added to the grid? Halkirk 2 wind farm, with 126 megawatts, was just added to the grid listing on Sept. 19, but is still in commissioning stages and registering zero. Lethbridge Solar’s new nine megawatt facility was added to the grid effective Sept. 17. Thus, the total count of grid-scale wind facilities is now 48, while there are 43 grid-scale solar facilities. This is roughly double the amount of wind and solar on the grid three years ago.

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Alberta had free power for more than a day in August, and seven hours last weekend – how does that happen?