California is burning. Indonesia is sinking. Greenland is melting.
Climate change is here. We’ve only just begun to feel its impact, and it’s sure to get worse from here if we don’t act now.
We’ve passed the time for denial. It’s time for solutions.
Like many of you, I always saw renewable energy generation as the most promising solution to climate change. I hadn’t considered the importance of energy storage until recently, but it turns out there’s a lot riding on the innovations in this industry.
In this article, I’ll cover four topics:
- Renewable energy’s greatest challenge
- Problems with the power grid
- Current methods of energy storage
- New innovations in energy storage
By the end, you’ll understand why I care about energy storage—and hopefully I’ll have convinced you too.
Renewable energies have been in the spotlight for years now — and for good reason. After all, traditional coal and natural gas power plants produce about 25% of the world’s GHG emissions through electricity generation. Researchers have been trying replace these polluters for years, and they’re making progress. Since 2019, solar and wind power have become the cheapest sources of energy, beating both coal and nuclear. Renewable energies are attracting innovators and investors alike. So why haven’t they been fully adopted?
It’s time to explain the Duck Curve.
The first thing we need to understand is that the demand for electricity varies over the course of a day. It looks something like this:
Let’s dig into this. We see the demand rising between 6 and 8 am and fluctuating around 2200 MW before dropping back down around midnight. Makes sense, right? Most of us wake up in the morning, work or study during the day, and sleep at night.
What about that high evening peak? Well, turns out that all those household activities — cleaning, cooking, washing, watching TV — combined with nightlife require a lot of energy. Plus, we have to turn on extra household and public lights to compensate for lost daylight.
There you go, that’s the problem. Did you miss it?
I’ll reiterate: we turned on those lights because the sun set. But if the sun has set, how can it produce the energy we need?
Just like energy demand, solar power production changes throughout the day relative to the amount of solar radiation emitted from the sun. Basically, more sunlight corresponds with more energy production.
So how much daylight do we get in a day? Of course, this is specific to your geographic location. In a regular Toronto March, the sun usually rises at 7:30 and sets twelve hours later. Solar electricity generation falls significantly during the other half of the day’s hours. Let’s see what the net load (energy demand minus solar energy supply) looks like in a graph:
It’s easy to see where the problem lies. Right around sunset, there’s a huge decrease in solar energy production while the electricity demand skyrockets. In fact, the net load more than doubles in just two hours, shifting an enormous energy burden onto other generators.
We can’t just rely on alternative energies to pick up that slack. Nuclear energy, one of the most reliable alternative energies commonly used today, is typically generated in a base-load power plant, which must run continuously to be cost-efficient. As a result, the energy output is constant regardless of temporal circumstances. These plants can’t suddenly begin generating more energy at sunset, nor can they produce excess amounts of energy during off-peak hours without sustaining serious damage. Instead, this extra demand is usually satisfied with peaker plants, which are both highly pollutant and wasteful.
This is why intermittency is solar energy’s biggest challenge.
Sure, solar power works great during the day, but what happens after the sun sets? This isn’t just a solar issue either; energies like wind and hydro would also benefit from solving the intermittency problem.
Innovations in clean energy production are amazing, but they alone are not enough. We need to look farther than energy generation if we want to hit our climate goals: it’s time to focus on energy storage.
When you trudge downstairs in the morning, what’s the first thing you do? You might turn on the kettle to boil water and place a slice of bread in your toaster. If you’re like me, you won’t turn on the lights until you get back upstairs, but when you do, it only requires the flip of a switch.
All the electricity needed to make these things happen is so readily available. That’s all thanks to the power grid, which transports electricity from faraway power plants to your home’s convenient electrical outlets.
Surprisingly, though, our electricity rarely comes from an inventory of energy just sitting around. The power grid actually generates electricity in response to the current demand, constantly balancing supply and demand in a precarious equilibrium.
This system has barely changed since its invention more than a century ago. The electric grid’s outdated design is in desperate need of innovation as we shift away from traditional generators to a diverse assembly of alternative energy sources. In particular, grids need to upgrade their flexibility — and the best way to do that is by increasing their capacity to store energy.
There are two major types of energy storage: pumped hydro and batteries.
At its core, pumped hydro is a hydroelectric dam. It relies on two large reservoirs of water in a hilly region to convert and store energy.
- Demand is lower than supply → Excess energy is used to pump water from the lower reservoir to the upper reservoir. The electric energy is stored as gravitational potential energy.
- Demand is higher than supply → Water flows downstream via the penstock and turns a turbine, converting the kinetic energy into electricity to be sent back to the grid.
Pumped hydro completely dominates the storage game, managing 99% of stored energy compared with less than 1% for batteries. That’s because pumped hydro can store energy for longer periods on a larger scale than batteries, allowing for easy integration into the energy grid. Unfortunately, this system is a net consumer of energy, losing about a quarter of the energy input from water evaporation and heat losses during conversion. It also can only exist in very specific geographic sites of temperate climate and appropriate topography. So, for the most part, electricity continues to be generated on demand.
Until recently, batteries haven’t been able to provide a better solution. The classic battery design is better suited for small bursts of energy rather than utility-scale energy storage. However, innovations in battery technologies have been gaining traction.
Today’s most exciting battery is the rechargeable lithium-ion battery, or Li-ion battery. First commercialized in 1991 for Sony, the demand for Li-ions has been growing exponentially as engineers recognize their potential for wide-scale applications outside of electronics.
Like all batteries, Li-ions consist of an anode, a cathode a separator, an electrolyte, and two current collectors.
- Battery is discharging → The anode releases lithium ions, which travel through the electrolyte to reach the cathode. Free electrons in the anode flow through the external circuit and create an electric current.
- Battery is charging → A charger sends electrons into the anode, drawing lithium ions in the cathode to return to the anode for a new cycle or discharge/charge to begin.
These batteries have high energy and power density, meaning they have high energy storage and generation capacity relative to their mass. Their design is constantly being refined as scientists continue to replace the metal compounds in the anodes and cathodes to optimize the Li-ion’s capabilities. For instance, researchers at the University of Texas recently have achieved improved battery performance by replacing cobalt cathodes with nickel.
As the demand for lithium swells, these concerns have prompted debate about the sustainability of batteries from a material standpoint. In particular, the two methods of lithium extraction, and , both negatively impact the environment. The most popular method is brine evaporation from salt flats, which requires immense amounts of water — approximately 500 000 gallons per tonne of lithium — from already water-scarce regions like Bolivia and Argentina. The alternative, ore mining, is less water-intensive, but uses various toxic chemicals that infiltrate surrounding farmland and freshwater sources. It’ll be an ongoing challenge to weigh the benefits of clean energy and reduced GHG emissions against the cost of land and water pollution.
Still, these batteries may be the key to realizing utility-scale energy storage, that is, batteries that can store enough energy to power cities. In fact, it’s already (kind of) happened. The Hornsdale Power Reserve in South Australia is the first of its kind to store excess energy in the power grid via Tesla’s lithium-ion batteries. It’s already saved Australians $150 million in energy costs in its first two years — nearly twice the amount it cost to build it. Similar projects are in the works (though LS Power’s Gateway Energy Storage has already dethroned Hornsdale as the biggest battery” in August).
Li-ions aren’t the only energy storage innovations coming our way. We might soon begin to hear about flow batteries (electrolytes separate from the battery), gravity-based energy storage (think pumped hydro, but with cranes and bricks), and pumped heat electrical storage (storing thermal energy) as additional grid supports — maybe even replacements.
One thing’s for sure: energy storage is an industry ripe for disruption.
Harnessing the energy of natural elements to create electricity instigated the Industrial Revolution and transformed the world into what is today. The modern world depends on electricity, but our future depends on our planet’s health. These goals aren’t inherently opposed, though; we only need to open our minds to alternatives.
If we want to adopt renewables into the energy system, we need to develop the infrastructure to handle them first. That’s why innovations in energy storage are crucial to unlocking the full potential of alternative energies. With the right technologies, we can completely revolutionize the power grid and pave the way for a clean energy future.