3 ms·

This is a great example of economics at work. Large-scale electricity storage solutions reduce the need for generating capacity from peak load to average load -

by nippoo 3y ago

This is a great example of economics at work. Large-scale electricity storage solutions reduce the need for generating capacity from peak load to average load - reducing the demand by the crest factor of the grid. The majority of this extra generation capacity is currently filled by gas (that is incredibly easy to spool up and down in a matter of seconds). Reducing the demand for natural gas will also increase the cost of other fossil fuels (which are mined in the same place), and it's a virtuous loop...

foobarian 3y ago
And given the sodium chemistries slowly showing up in production this seems like it will only continue to escalate going forward. It's a hopeful achievement.
huijzer 3y ago
I know someone who worked in a gas plant and although it might take seconds once the plant is running (I don’t know), it takes multiple minutes to start it after being off. In comparison, scaling from 0% to 100% load on battery storage takes 0,1 seconds, according to Tesla.
- triplepoint217 3y ago
  Gas plants can't really change how much they are generating in seconds. What they actually do is use the inertia of the spinning machinery, when the grid frequency drops (which is usually one of the first symptoms of load exceeding demand) the big spinning generators don't change speed instantaneously, they instead come under higher load and and convert more of their kinetic energy into electrical energy and help prop up the grid frequency. This starts the generators slowing down which then causes the control software to do whatever it is they do to feed in more gas and generate more power to try to keep them running at the same speed (I don't know exactly, I worked in grid batteries not gas plants). But yes, the batteries can respond much faster and are way better at this kind of support. It does lead to some situations that felt slightly weird to me where a battery will be selling a "spinning" reserve product. Luckily the weird linguistic artifact did not require us to actually rotate multi-ton batteries ;).
  - skewbone 3y ago
    Gas plants can change load in seconds by increasing or decreasing fuel flow. You can consider the generators as operating at the local grid frequency, and power being the product of torque and frequency, so they just change torque to change load, which is done through fuel control. Aeroderivative gas turbines can go from near 0 to full load in less than 30 seconds, which is obviously an eternity compared to battery system inverters with sub 150ms settling times. You are right that load isn’t independent of frequency, though. For those who are interested, in a simplistic and hand-wavy explanation, the torque imbalance between generation and load causes a change to the frequency. The net torque = torque of generation - torque of load = I*alpha, where alpha is the derivative of omega, or the angular frequency of the grid, and I is analogous to the inertia of the grid. If there is more generation torque than load torque on a generator (and the grid), the frequency increases and vice versa. Keeping the net torque constant, increasing the inertia makes the grid frequency derivative smaller for the same imbalance between generation and load, which is why it was typically desirable to have higher inertia synchronous generators. What you were describing around changing fuel to maintain speed is typically frequency droop, which is where generators change their power as a function of the frequency, which is a distributed scheme for all generators to independently act to drive the torque imbalance to 0, with some insensitivity proportionality constant. For example, in California, gas turbines are assigned a droop value within the range of 3 to 5%, which means a 3 to 5 % reduction in frequency should result in a 100% increase in power, and vice versa. The total power should be provided in less than 30 sec typically. For those that are really motivated to understand the interplay between generation, load, and frequency, look up the swing equation in the context of power system stability. There is another aspect of synchronous generators that enable them to act to stabilize frequency independently, called the inertial response, which also has to do with their rotational energy. A generator at some frequency has KE = 0.5*J*omega^2 where J is rotational inertia and omega is angular frequency. If the frequency changes, it has a change in kinetic energy = 0.5*J*(omega1^2 - omega2^2) which is equal to some power for some period of time (= P*delta_t). This shows that as a generator sees a change in frequency, the shorter the duration, the larger the amount of energy is converted to power. Essentially, generators have an inertial response that act to inject power the faster frequency is falling, and vice versa, which is a self stabilizing function for grid frequency. This loss of synchronous inertia as generators are replaced by inverter based resources (IBRs) is why managing grid frequency stability becomes more difficult. Various techniques are used to abate the loss of inertia, including emulating the swing equation within inverters to make them behave as synchronous generators and provide that inertial response. This is typically called grid forming with virtual synchronous machine.
toomuchtodo 3y ago
Sort of. Thermal generation provides grid services that they get paid for. This revenue is substantial. This means when frequency sags, gas plants were traditionally called on to ramp quickly to maintain grid inertia. Battery storage can do this ("fast frequency response") in milliseconds (vs minutes or tens of minutes for thermal generation, where fuel must be added and momentum of spinning turbines added to), and is eating this valuable revenue distinct from energy arbitrage (charging when power is cheap, free, or negative priced, and discharging when energy prices are higher). This helps kill the economic case for thermal generators, accelerating their phase out. https://www.frontiersin.org/articles/10.3389/fenrg.2022.971704/full https://www.frontiersin.org/articles/10.3389/fenrg.2022.9717... https://www.sandia.gov/files/ess/EESAT/2002_papers/00015.pdf https://www.sandia.gov/files/ess/EESAT/2002_papers/00015.pdf https://www.pv-magazine.com/2022/07/27/tesla-big-battery-begins-providing-inertia-grid-services-at-scale-in-world-first-in-australia/ https://www.pv-magazine.com/2022/07/27/tesla-big-battery-beg... https://www.energy-storage.news/batteries-earn-big-in-european-ancillary-services-but-investors-warned-of-high-expectations/ https://www.energy-storage.news/batteries-earn-big-in-europe...
triplepoint217 3y ago
Glad to see this finally happening. This goal was definitely part of the appeal when I was working on the Autobidder team at Tesla! The regulations have some work to do catch up to allowing batteries to operate in a straightforward manner. For example, the big battery we launched in Texas had to be registered as both a generator and a controllable load with all sorts of weird issues around switching from discharging (being a generator) to charging (being a load) that a battery wants to do all the time. We found engineering solutions to them, but it's even better that the market operators are working on properly recognizing batteries as their own unique asset with their own advantages and challenges.

by nippoo 3y ago

foobarian 3y ago

And given the sodium chemistries slowly showing up in production this seems like it will only continue to escalate going forward. It's a hopeful achievement.

huijzer 3y ago

I know someone who worked in a gas plant and although it might take seconds once the plant is running (I don’t know), it takes multiple minutes to start it after being off. In comparison, scaling from 0% to 100% load on battery storage takes 0,1 seconds, according to Tesla.

triplepoint217 3y ago
Gas plants can't really change how much they are generating in seconds. What they actually do is use the inertia of the spinning machinery, when the grid frequency drops (which is usually one of the first symptoms of load exceeding demand) the big spinning generators don't change speed instantaneously, they instead come under higher load and and convert more of their kinetic energy into electrical energy and help prop up the grid frequency. This starts the generators slowing down which then causes the control software to do whatever it is they do to feed in more gas and generate more power to try to keep them running at the same speed (I don't know exactly, I worked in grid batteries not gas plants). But yes, the batteries can respond much faster and are way better at this kind of support. It does lead to some situations that felt slightly weird to me where a battery will be selling a "spinning" reserve product. Luckily the weird linguistic artifact did not require us to actually rotate multi-ton batteries ;).
- skewbone 3y ago
  Gas plants can change load in seconds by increasing or decreasing fuel flow. You can consider the generators as operating at the local grid frequency, and power being the product of torque and frequency, so they just change torque to change load, which is done through fuel control. Aeroderivative gas turbines can go from near 0 to full load in less than 30 seconds, which is obviously an eternity compared to battery system inverters with sub 150ms settling times. You are right that load isn’t independent of frequency, though. For those who are interested, in a simplistic and hand-wavy explanation, the torque imbalance between generation and load causes a change to the frequency. The net torque = torque of generation - torque of load = I*alpha, where alpha is the derivative of omega, or the angular frequency of the grid, and I is analogous to the inertia of the grid. If there is more generation torque than load torque on a generator (and the grid), the frequency increases and vice versa. Keeping the net torque constant, increasing the inertia makes the grid frequency derivative smaller for the same imbalance between generation and load, which is why it was typically desirable to have higher inertia synchronous generators. What you were describing around changing fuel to maintain speed is typically frequency droop, which is where generators change their power as a function of the frequency, which is a distributed scheme for all generators to independently act to drive the torque imbalance to 0, with some insensitivity proportionality constant. For example, in California, gas turbines are assigned a droop value within the range of 3 to 5%, which means a 3 to 5 % reduction in frequency should result in a 100% increase in power, and vice versa. The total power should be provided in less than 30 sec typically. For those that are really motivated to understand the interplay between generation, load, and frequency, look up the swing equation in the context of power system stability. There is another aspect of synchronous generators that enable them to act to stabilize frequency independently, called the inertial response, which also has to do with their rotational energy. A generator at some frequency has KE = 0.5*J*omega^2 where J is rotational inertia and omega is angular frequency. If the frequency changes, it has a change in kinetic energy = 0.5*J*(omega1^2 - omega2^2) which is equal to some power for some period of time (= P*delta_t). This shows that as a generator sees a change in frequency, the shorter the duration, the larger the amount of energy is converted to power. Essentially, generators have an inertial response that act to inject power the faster frequency is falling, and vice versa, which is a self stabilizing function for grid frequency. This loss of synchronous inertia as generators are replaced by inverter based resources (IBRs) is why managing grid frequency stability becomes more difficult. Various techniques are used to abate the loss of inertia, including emulating the swing equation within inverters to make them behave as synchronous generators and provide that inertial response. This is typically called grid forming with virtual synchronous machine.

toomuchtodo 3y ago

Sort of. Thermal generation provides grid services that they get paid for. This revenue is substantial. This means when frequency sags, gas plants were traditionally called on to ramp quickly to maintain grid inertia. Battery storage can do this ("fast frequency response") in milliseconds (vs minutes or tens of minutes for thermal generation, where fuel must be added and momentum of spinning turbines added to), and is eating this valuable revenue distinct from energy arbitrage (charging when power is cheap, free, or negative priced, and discharging when energy prices are higher). This helps kill the economic case for thermal generators, accelerating their phase out. https://www.frontiersin.org/articles/10.3389/fenrg.2022.971704/full https://www.frontiersin.org/articles/10.3389/fenrg.2022.9717... https://www.sandia.gov/files/ess/EESAT/2002_papers/00015.pdf https://www.sandia.gov/files/ess/EESAT/2002_papers/00015.pdf https://www.pv-magazine.com/2022/07/27/tesla-big-battery-begins-providing-inertia-grid-services-at-scale-in-world-first-in-australia/ https://www.pv-magazine.com/2022/07/27/tesla-big-battery-beg... https://www.energy-storage.news/batteries-earn-big-in-european-ancillary-services-but-investors-warned-of-high-expectations/ https://www.energy-storage.news/batteries-earn-big-in-europe...

triplepoint217 3y ago

Glad to see this finally happening. This goal was definitely part of the appeal when I was working on the Autobidder team at Tesla! The regulations have some work to do catch up to allowing batteries to operate in a straightforward manner. For example, the big battery we launched in Texas had to be registered as both a generator and a controllable load with all sorts of weird issues around switching from discharging (being a generator) to charging (being a load) that a battery wants to do all the time. We found engineering solutions to them, but it's even better that the market operators are working on properly recognizing batteries as their own unique asset with their own advantages and challenges.