The Duck Curve Part 2: Smoothing Out the Curve

 As mentioned in our previous post The Duck Curve Part 1: The Challenges of Demand Flexibility,” the Duck Curve is a result of when large amounts of renewables, particularly solar, are added to a power system. Now, let’s build on what we learned in Part 1 and discuss ways in which we can possibly “smooth” out the Duck Curve.

1. Improving Power System Flexibility

When a Duck Curve begins to take shape its important to start looking at the overall “flexibility” of the power system that is responsible for generating electricity. We define power system flexibility as the ability of a generating or storage technology in a power system to ramp up and down to meet demand.

If a technology is flexible (think batteries or some advanced thermal technologies) then that equipment could turn on and off and cycle power outputs up and down extremely fast.

If a technology is inflexible (think coal, nuclear or large gas plants) then there is no magic “on/off switch.” With inflexible technologies you have to literally wait for the science of physics & thermodynamics to do their work first to get your plant to a point where you can control your power output.

Turning off and on quickly and fluctuating generating output up and down is operationally and economically unviable. Inflexible or traditional power plant technologies attempting to operate this way will cause equipment to be damaged and emissions to increase. The excerpt below from Part 1 emphasize the challenge that system inflexibility creates;

“Plant operators are forced to keep inflexible plants that run on coal, oil, and gas operating all day, still burning fuels and producing emissions even though there is no demand need because they have to be ready to ramp up their generation when the sun goes down and the demand goes up”

So, if a system is made up of enough flexible technologies then plant operators can properly utilize the renewable energy .Which means no wasting (often called “curtailing”) of energy that was generated from renewables. This is because flexible technologies are able to turn completely off and then quickly turned back on to meet the evening ramp caused by our Duck Curve. If the goal is enabling renewables while flattening the curve, a power system could add advanced storage systems and modern cleaner thermal technologies.

2. Storing as Much Excess Energy as Possible

Though the deployment of an adequate amount of large storage assets isn’t economically viable today, it has a vital role to play in smoothing out the Duck Curve.

Even states leading the charge in energy storage – like California – are struggling with the economies scale in addressing the challenges the duck curve is causing. According The University of Michigan 2018 U.S Grid Energy Facts Sheet “California leads the U.S. in energy storage with 220 operational projects (4.2 GW), followed by Virginia and South Carolina”. This is not to say that California must stop investing in storage, in fact as storage assets become more cost effective over time, California should add more to reap the benefits of the energy produced in the day. Then, as the sun goes down discharge that stored energy to offset the afternoon ramp.

benchmarks of battery storage for power system flexibility

As you can see from the above graph from GTM, storage will continue to become more and more cost competitive and will play a vital role in high renewable power systems of the future.

3. Improving Energy Efficiency

Everyone should play a part in helping to achieve 100% renewables while flattening the Duck Curve. That means re-thinking the old ways of how we handled the idea of energy efficiency.

One example of how an entity can play their part comes from the Alabama Smart website. Author Daniel Tate writes that one of the more viable methods for smoothing out the duck curve is for utilities to commit “to the storage of energy generated by solar and wind, instead of immediately sending that energy directly to the grid.” He goes on to explain, “The energy can then be ‘dispatched’ when it’s needed and would almost definitely flatten the curve.” (Energy Alabama, May 2017)

Another solution targets energy efficiency in the building sector. University of Berkeley Lab physicist Dr. Mary Ann Piette notes that buildings use more energy than any other sector and so they produce more greenhouse gases. The solution she and her colleagues are developing technology to see energy use at the equipment or appliance level—rather than at the household level as we do today. With this innovative technology, we enable “smart buildings” – meaning that the entire building would communicate with the power grid and respond to generation and price signals automatically. Systems could self-regulate: lower air conditioning use after sunset, recharge electric vehicles during peak wind generation, and so on.

Dr. Pette notes, “The belly of the duck means that there is a lot of electricity available, and it’s becoming cheaper in the middle of the day. For decades we’ve been concerned about time of use, and we tried to use less in the middle of the day and more at night. But we’re actually now very interested in using more during certain times of the day.” (Berkeley News, January 2018)

The Duck Waddles On…

The challenges of the Duck Curve will have to be addressed over time – and we will find that facing these challenges gets easier as both generating and storage technologies continue develop and improve. In the here and now, however, we can make incremental steps such as adding flexible technologies or by avoiding the building of traditional inflexible power plants. Such steps should all be made in parallel with finding ways to reduce curtailing (wasting) of plentiful energy during key hours – by focus on technologies at the building level, for example.

We must then take all of these incremental steps and execute them in combination with increased deployment of energy storage and new energy efficiency programs.

Only then can we smooth out the Duck Curve.