In the video, Professor William Chueh summarizes the current state of energy storage technology, important information on the topic of energy storage, and future prospects.

My notes are included below the video.

Notes:

• The presenter, William Chueh, is Assistant Professor of Materials Science and Engineering at Stanford University. In 2012, he was named one of the top 35 innovators under the age of 35 by MIT’s Technology Review. He holds a B.S in applied physics and M.S and PhD material science. He received both from Cal Tech.

• The cost of lithium ion batteries declined nearly 80% from 2010 to 2018.

• The cost of generating electricity with wind turbines has fallen by 90% since the 80s.

• The cost of generating electricity with solar has fallen by 99% in the past two decades.

• In our transition to renewables, two questions are of great importance:

• • Can we power the transportation sector entirely with renewables?

• • Can we power the grid entirely with renewables?

• These questions must be addressed from both a business standpoint and a technological standpoint.

• The millionth ever electric vehicle was sold in 2015, the two millionth in 2016, and the four millionth by 2018.

• All together, there are about 1 billion vehicles on the road, the vast majority of which are gas powered.

• We are about to have over 1 terawatt of total installed wind and solar capacity.

• A key challenge for the grid will be coping with the generation of variable electricity (which fluctuates based on environmental conditions.)

• • The grid must be modified in order for it to run effectively on variably generated electricity.

• • One of the best ways of dealing with variably generated electricity is by having a large amount of storage capacity installed, so as to hold it (energy) for use during peak hours.

• Utility scale energy storage and distributed energy storage (such as home storage using a Tesla powerwall) have both been growing rapidly. Rapid growth in both sectors will continue.

• One of the key drivers of the growth of energy storage is favorable policy.

• Batteries are not the only type of technology we use for grid storage. However, batteries are an important aspect of this sector, and their prevalence is likely to increase in the future.

• There was almost zero installed battery storage capacity prior to 2010.

• • However, the amount of installed battery storage capacity has risen sharply since this time, driven largely by the decrease in the cost of lithium ion batteries.

• The utility of storage technology is largely a function of how much time energy must be stored for (this amount of time will vary from situation to situation.) Chueh goes more depth into this point at around 8:30 in the presentation.

• If electricity supply and electricity demand do not match one another perfectly, some buffering of the grid is required.

• Key term: Peak shaving – Accounting for excessive amounts of energy demand (when the grid requires more energy than power plants are producing).

• Key term: Curtailment – Accounting for excessive amounts of energy supply (when power plants are producing more energy than the grid can use).

• The extent to which renewables can power the grid is largely a function of how much energy storage capacity infrastructure has been installed.

• 11:00 Chueh discusses a graph showing the variability of wind-generated electricity and the variability of grid demand over the course of multi-day period.

• • In some instances, (such as when there is ample wind but little demand on the grid) electricity companies actually have to pay wind companies not to generate electricity.

• 13:40 – Key point: The ability to respond to fluctuations in demand on the grid is very important. Batteries are well suited to dealing with demand fluctuations.

• 14:00 – Chueh discusses the installation of Teslas 100MW lithium ion battery facility in Australia. This facility is primarily used to buffer the grid so that the frequency is held constant.

• Batteries can be very useful for peak shaving. When renewables are generating more electricity than the grid demands, the excess energy can be channeled into batteries. When renewables produce less than the grid demands, batteries can use stored energy to make up for the deficit.

• • In many instances, wind blows at night when there is low demand, and doesn’t blow much during the day. If the energy generated during the night is stored in batteries, it can be used to power the grid during the day.

• 17:00 Chueh covers the “Duck Curve”

• The large amounts of solar capacity in California force non-renewable power plants to shut down during the day, and then restart at night once the sun has set.

• In California, an amount of fossil-fuels generation capacity equivalent to roughly half the Australian grid must be turned off and on everyday due to the rapid advent of solar technology.

• 22:00 – Chueh discusses the potential of seasonal shifting – taking excess energy generated in the summer and storing it for use during the winter when renewable generation goes down.

• 24:00 – Key point: The more energy storage infrastructure you have, the less renewable generation infrastructure you will require to properly power the grid.

• • If you do not have adequate storage, you will need an excessive amount of installed wind and solar, to account for those days when there is not much sun or wind.

• 25:00: “If you want 50% penetration of solar in the U.S, you need storage.”

• If there is a mixture of wind and solar, less solar is required, due to the fact that the two sources of energy often generate at different times of the day, thereby canceling out each others’ generation gaps.

• Storage is required for a high degree of renewable penetration.

• Energy storage is not the only option. An alternative is natural gas peaker plants. There plants can generate energy to compensate for the instances in which renewables are not generating enough to adequately supply the grid.

• At the moment, it’s generally more economical to use peaker plants than energy storage to compensate during the periods in which renewables don’t generate enough to meet grid demand. By 2030, the opposite is expected to be true.

• There are many different metrics by which energy storage technologies can be quantified and compared

• • Calendar life: How long the technology lasts before it must be replaced.

• • Cycles life: How many cycles can be put through the storage technology before it must be replaced (e.g. how many times a battery can be charged and discharged before wearing out).

• • Energy cost: How much money it takes to store a certain amount of energy.

• • Gravimetric energy density: How heavy the storage technology must be to store a certain number of kilowatts. For example, diesel fuel can store many times more kilowatts of energy per pound than today’s batteries.

• • Power cost: The cost of delivering energy at a certain rate. It costs more to deliver large amounts of energy per unit of time than it does to deliver smaller amounts of energy per unit of time.

• • Ramp rate: How fast a particular energy storage technology can be changed and discharged.

• • Round trip efficiency: How much of the energy put into the storage technology can be discharged.

• • Safety: Energy storage technologies must but safe over the entire course of their lifecycles.

• • Temperature range: Which temperatures the technology can perform at.

• • Volumetric energy density: How much energy the technology can store per unit of volume.

• The relative importance of these metrics will vary depending on the intended application of the energy storage technology. For example, gravimetric energy density is far more important for energy storage technologies intended for use in electric cars than it is for those intended for use in stationary energy storage facilities.

• 32:30 – Chueh lists what he feels to be a few of the most important storage technologies currently in use.

• • Electromagnetic

• • Thermal storage (such as molten salt used in concentrated solar power plants)

• • Electrochemical (such as lithium ion batteries, lead acid batteries, and flow batteries)

• • Mechanical (such as pumped hydro systems. Air can also be used as a storage medium. Pumped hydro is currently the dominant form of energy storage in the world)

• • Chemical (using electricity to create chemicals, such as hydrogen)

• Pumped hydro dominates the energy storage space today. The distant runner up is molten salt thermal storage, followed by lithium ion batteries.

• There is currently a tremendous amount of interest in lithium ion batteries; This type of storage technology has been growing rapidly recent years.

• 36:00 – Chueh explains how lithium batteries store energy.

• The price of lithium batteries has fallen sharply in recent years.

• Characteristics of lithium ion batteries:

• • High round trip efficiency: Approximately 90%

• • Cycles life: Several thousand recharge cycles

• • Calendar life: Approximately ten years

• • Cost per kilowatt: Attractive for transportation, but quite high for grid storage

• •  

• 38:00 – Chueh covers lithium ion cost trends ($1000 per kilowatt hour in 2013, anticipated to below $100 by 2025)

• • As the cost goes down, new applications will emerge.

• Installed capacity has been increasing massively. The market for lithium ion batteries is projected to reach over 1 trillion dollars in the next ten years.

• A majority of lithium ion manufacturers are based in Asia.

• Cobalt, nickel, and lithium are three of the most expensive common components in batteries.

• For grid applications, energy density of storage technologies can actually be quite low.

• Batteries from electric vehicles can be repurposed for grid storage after they have degraded to the point that they can no longer be used for powering vehicles.

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