Texas’ Big Freeze: The 2021 Power Crisis and the Lessons Learned One Year Later 34

[bimr]

Link

 

[Guest102023]

TX leadership objectives.

At the risk of going off topic, TX leadership has some pretty dark objectives. End of comment.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[JohnRBaker]

If temps rise as predicted tomorrow across Texas (they're saying that it'll be 102˚ where our son lives), it could test the state's power grid as demand is estimated to reach 80 gigawatts, which would be the highest level that it has ever been. The state's power authority, ERCOT, says that renewables, such as wind and solar, should provide sufficient reserve capacity that there shouldn't be a risk of any serious interruptions in service.

Note that here in California, the state's power authority, California ISO, is predicting that tomorrow's peak demand will be just short of 42 gigawatts. Our expected capacity is estimated to be just over 48 gigawatts.

John R. Baker, P.E. (ret)
Irvine, CA
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[cranky108]

Lets see, if your capacity is 48, and your load is 42, what are you doing with that 6 GW?

 

[JohnRBaker]

Perhaps I should have said that it's the 'potential capacity', but since we still generate a fair amount of our power using natural gas, we can simply throttle-back the turbines when we need less than the 'potential' ;-)

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
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[IRstuff]

It's still capacity; ISO has the ability to allow some of the generators to spin down/up to maintain operation by essentially throttling the fuel supplies. You just can't do that with the major renewables, hence the abundance of snake-oil in the energy storage arena

TTFN (ta ta for now)
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[JohnRBaker]

Technically you can 'feather' a wind turbine so that it stops turning even if the wind is blowing. This feature is also used when the wind speed exceeds the design limitation for the generator to protect it. Also, when the wind speed is very low, even if the blades could turn, often they're feathered so as to stop the blades to save wear and tear on the generator and gearbox during periods when the power generated would be so low as to be uneconomical.

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[cranky108]

The problem is when you throttle (if that is the right term) renewable generation, the owner want to be paid for not generating. We don't see that with traditional generation.
Besides that the traditional generation, the first units to be idled is the most expensive. Can we do that with wind and solar?

 

[JohnRBaker]

I suspect that it'll be a long time before the grid has insufficient levels of "traditional generation" capacity that they would be forced to "throttle" renewable sources to any significant degree. And when we do reach that point, I suspect that the use of batteries will have advanced to the point where there will be enough capacity available to handle the everyday need to 'level' the load, both in terms of providing additional power when needed as well as providing storage capacity for excess production so that things like renewables will not need to be "throttled".

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[Guest102023]

Grid stability in hot weather is as important as outright capacity.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[TugboatEng]

In urban areas stability is very important due to climate control needs. Those of us in suburbs and rural can tolerate outages here and there. California has proven that with the public safety power shutoffs.

 

[Fischstabchen]

JohnBaker,

Feather is also used regularly to reduce ramp rates. The Texas grid almost collapsed in 2009 with plus and minus GW per an hour ramp rate.

 

[JohnRBaker]

I'm not familiar with what 'ramp rates' are. Could you provide a link that you think best describes the significance of this? Thank you.

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[davidbeach]

Ramp rate is how fast the resource can change output. IBRs (Inverter Based Resources) can ramp extremely rapidly. Conventional generation may not be able to ramp as quickly. California is just one corner of a huge electrical interconnection. When they have too much IBR output power flows north and conventional generation backs off. When IBR output ramps down at the end of the day the flow reverses and the conventional generation ramps up.

Two years ago there was a significant bottle neck in that north-south path and the conventional generation couldn’t flow south in sufficient quantity to make up for the rapid ramp down of solar at the end of the day.

If California would just limit their air conditioning load to match their PV output all would be a piece of cake.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[JohnRBaker]

If California would just limit their air conditioning load to match their PV output all would be a piece of cake.

Perhaps that's why Edison raise the power rates from 5:00PM to 8:00PM each day to encourage people to use less electricity during those hours. I've set my programmable thermostat to turn the temp UP a few degrees for the A/C covering those three hours.

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[TugboatEng]

Just for consideration, AC systems use bang-bang control schemes for the most part so raising your thermostat setting doesn't reduce the power draw. The idea of lowering thermostats to lower load relies heavily on the assumption the assumption that AC cycles will randomly offset themselves.

 

[JohnRBaker]

And what pray-tell is a "bang-bang control scheme"? How are we NOT using less power when I raise the temperature setting on our thermostat?

As for "randomly offsetting themselves", the power company, at least in our situation, can shut-off our A/C anytime they want. Note that this A/C cycling program is totally voluntary and we've signed up for the 'Maximum Savings' option, which allows SCE (Southern California Edison) to shut-off our A/C for up to six hours a day during power emergencies (so far this year we've not noticed any interruptions in service). We are compensated with a credit on our monthly bill from June through September, which is currently running about $32/month (it's based on the maximum size of your A/C unit). We also get a once-a-year credit in the amount of $50 posted during our last billing cycle of the year, as an incentive to sign-up for the program. We've been part of the program since it's inception, which was at least 15 years ago.

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[Alistair_Heaton]

I was reading that 2024 that all inverters need to go smart ie the german ripple receivers will come in so the grid can change the inverter settings and heating/cooling targets.

 

[TugboatEng]

Air conditionong systems mostly run on a thermostat. The compressor turns on when the temp exceeds setpoint and stops when hysteresis is exceeded. The power is the same regardless of the thermostat setting. Average power will be lower but instantaneous is unchanged.

Grid capacity is an instantaneous number, not an average number.

Allistair, what you mention would allow a level of synchronization to offset the time units spend online but I doubt anybody is going to go through the effort to make such an intelligent program. They'll just turn units off as capacity is reached.

 

[Alistair_Heaton]

yep but if everyone increases it at the same time all the compressors will go off at the same time and there is a drop in demand for a period until they can get the spinners up and producing.

Most aircon units in europe new now are variable output electronic expansion valve which varies with the delta T of actual V set point. And the latest gen are all inverter drive and as such don't stop if the outside temp is different to internal. The rest of the time it just changes the feed temp supplied.

 

[cranky108]

Very correct, the most AC units are either on or off, and I don't know of many that just have high and low levels.
The funny/strange thing about cycling devices is they tend to develop a group cycle that can be very hard to follow.
I have seen this with unbalanced pump jacks, and would expect that from cycling AC units.
I think people would complain if there power (visuably) flickered like that.

I was in a discussion with our planning group recently (I am sort of mandated to talk to them), we were dissing the distribution interconnect requirements, and ride through. And YES the requirements will be changing.