Energy & Storage

Electricity starts our mornings and charges our devices. It powers industries and lights our nights. It is even set to increasingly run our cars. It is self-evident, yet the system has been changing at a rapid pace if we look back at the past few decades.

Since the discovery of electricity, we have sought effective methods to store that energy for use on demand. Over the last century, the energy storage industry has continued to evolve and adapt to changing energy requirements and advances in technology.

The electricity grid is a complex system in which power supply and demand must be equal at any given moment. Constant adjustments to the supply are needed for predictable changes in demand, such as the daily patterns of human activity, as well as unexpected changes from equipment overloads and storms. Energy storage plays an important role in this balancing act and helps to create a more flexible and reliable grid system.

More Americans work in the booming solar or windpower industries than in the coal industry, yet renewables are often claimed to be unreliable, needing vast and costly energy storage. Amory Lovins explains why that’s a myth.

 


Balancing a fragile energy system
Many people see affordable storage as the missing link between intermittent renewable power, such as solar and wind, and 24/7 reliability. Utilities are intrigued by the potential for storage to meet other needs such as relieving congestion and smoothing out the variations in power that occur independent of renewable-energy generation. Major industrial companies consider storage a technology that could transform cars, turbines, and consumer electronics.

Since renewable energies have grown and conventional sources of power keep phasing out, we are faced with a constant problem: The sun does not always shine, and the wind does not always blow – but the electricity grid is a fragile system in which supply and demand must be equal at all times.

Flexibility is needed to adjust to the variations in energy demand, such as people’s daily patterns, as well as the fluctuation in supply coming from renewable energies. When there is more supply than demand, such as at night when cheap power plants continue to operate, or during periods when the wind produces more power than can be consumed, the surplus electricity can be stored in order to achieve greater efficiency. And as soon as the demand exceeds the supply again, the storage facilities can feed the stored energy back into the grid.

Energy storage plays an important role in this balancing act and makes the grid system more stable and reliable.

Under your bed, in the attic even on your mobile phone, it seems there's never enough storage. It turns out it's also true of energy, particularly on sustainable energy.

 

Benefits of Energy Storage

Energy storage is key to achieving overarching low carbon and electrical network efficiency targets by:

  • Deferring or avoiding investment in network reinforcement

  • Reducing the need for conventional generation, including peaking power plants

  • Meeting binding targets with lower renewable capacity

  • Maximising the use of low carbon, inflexible generation

  • Optimising balancing of the system on a minute by minute basis

At grid level, energy storage reduces stress on the electrical network infrastructure, increases the proportion of renewables on the grid and increases reliability of renewable generation. It also provides efficient demand balancing options for the grid and reduces the need for backup demand generation.

 


Energy storage technologies

Different energy storage technologies contribute to electricity stability by working at various stages of the grid, from generation to consumer end-use.


Thermal Storage
Thermal storage is used for electricity generation by using power from the sun, even when the sun is not shining. Concentrating solar plants can capture heat from the sun and store the energy in water, molten salts, or other fluids. This stored energy is later used to generate electricity, enabling the use of solar energy even after sunset.

Thermal storage technologies also exist for end-use energy storage. One method is freezing water at night using off-peak electricity, then releasing the stored cold energy from the ice to help with air conditioning during the day.


Compressed Air
Compressed Air Energy Storage (CAES) also works as a generation storage technology by using the elastic potential energy of compressed air to improve the efficiencies of conventional gas turbines.

CAES systems compress air using electricity during off-peak times, and then store the air in underground caverns. During times of peak demand, the air is drawn from storage and fired with natural gas in a combustion turbine to generate electricity. This method uses only a third of the natural gas used in conventional methods. Because CAES plants require some sort of underground reservoir, they are limited by their locations. Two commercial CAES plants currently operate in Huntorf, Germany and MacIntosh, Alabama, though plants have been proposed in other parts of the United States.


Hydrogen
Hydrogen can be used as a zero-carbon fuel for generation. Excess electricity can be used to create hydrogen, which can be stored and used later in fuel cells, engines, or gas turbines to generate electricity without producing harmful emissions. The potential for creating hydrogen from wind power and storing it in the wind turbine towers for electricity generation when the wind isn’t blowing.


Pumped Hydroelectric Storage
Pumped hydroelectric storage offers a way to store energy at the grid’s transmission stage, by storing excess generation for later use.

Many hydroelectric power plants include two reservoirs at different elevations. These plants store energy by pumping water into the upper reservoir when supply exceeds demand. When demand exceeds supply, the water is released into the lower reservoir by running downhill through turbines to generate electricity.

With more than 22 GW of installed capacity in the United States, pumped hydro storage is the largest storage system operating today. However, the long permitting process and high cost of pumped storage makes further projects unlikely.

Flywheels
Flywheels can provide a variety of benefits to the grid at either the transmission or distribution level, by storing electricity in the form of a spinning mass.

The device is shaped liked a cylinder and contains a large rotor inside a vacuum. When the flywheel draws power from the grid, the rotor accelerates to very high speeds, storing the electricity as rotational energy. To discharge the stored energy, the rotor switches to generation mode, slows down, and runs on inertial energy, thus returning electricity to the grid.

Flywheels typically have long lifetimes and require little maintenance. The devices also have high efficiencies and rapid response times. Because they can be placed almost anywhere, flywheels can be located close to the consumers and store electricity for distribution.

 


Batteries
Batteries, like those in a flashlight or cell phone, can also be used to store energy on a large scale.

Like flywheels, batteries can be located anywhere so they are often seen as storage for distribution, when a battery facility is located near consumers to provide power stability; or end-use, like batteries in electric vehicles.

There are many different types of batteries that have large-scale energy storage potential, including sodium-sulfur, metal air, lithium ion, and lead-acid batteries. There are several battery installations at wind farms; including the Notrees Wind Storage Demonstration Project in Texas, which uses a 36 MW battery facility to help ensure stability of the power supply even when the wind isn’t blowing.

Advancements in battery technologies have been made largely due to the expanding electric vehicle (EV) industry. As more developments are made with EVs, battery cost should continue to decline. Electric vehicles could also have an impact on energy storage through vehicle-to-grid technologies, in which their batteries can be connected to the grid and discharge power for others to use.


Future

One of the most exciting innovations in energy over the past decade has been the development of energy storage technology. Batteries have become viable for almost every size project, from homes to the largest utilities.

In 2018, 311 megawatts (MW) and 777 megawatt-hours (MW-hr) of energy storage were installed in the U.S.. The cumulative installations could power 75,000 homes for an entire year, and they're just the start of the industry's growth

Energy storage is still a small market, but it's growing quickly and costs are coming down just as fast.

Analysts are expecting installations to surpass 4,500 MW in capacity by 2024.

The market isn't growing by accident, either. The arbitrage between when wind and solar power is provided and demand is highest is growing, creating an economic opportunity for energy storage. Regulators have also opened storage up to competitive markets, allowing them to bid into the market just like any other power plant.

Global energy storage on the grid is expected to double what it is today by 2021. Countries such as Japan, India, Germany, the United Kingdom and the United States are preparing to take advantage of this shift through research, policy and integration. This webinar will discuss the rapid growth in interest, current trends in energy storage (particularly electrochemical), as well as markets involving the electricity grid.

 

As the cost of batteries and other energy storage mediums fall and the energy markets open up to storage, investors should expect the industry to grow. That's welcome news for everyone from solar developers who are adding storage to projects to utilities who are using storage as a new regulated asset on the grid. And it's an asset class energy investors shouldn't ignore.


Solutions - New Projects

With renewable energy production on the up, the need for dependable energy storage solutions has never been greater. Recently, new technologies have driven that storage to new levels of efficiency but the future of renewable energy depends on whether or not they take off.

 

Flow Batteries
Fuel cells power space capsules and aircraft, capitalizing on reactions that convert the chemical energy in small organic molecules like methanol into electricity. It was figured that if you could craft a fuel cell that also runs in reverse—essentially converting energy back into chemical reactants—the resulting flow battery could store solar power using inexpensive, organic fuel.

Inorganic, metal ion-based flow batteries have been in use since the 1980s. These older models were constructed as tanks filled with vanadium ions, and could be customized to deliver more hours of energy by simply increasing the amount of vanadium in a storage tank. Unfortunately, vanadium isn't cheap.

Renewables are growing, but even if they could some day replace fossil fuels, there's a problem: that energy needs to be stored. Currently battery tech isn't up to the task, but the solution to one of the world's most pressing problems might just be sitting in Marlborough Massachusetts.

 

Hydrogen
New strategy—converting solar energy to hydrogen, instead of electricity. The key is water: "You start out with water and just break it into its elemental form, then collect that hydrogen in a tank and then burn it at night."

Although the team is currently working with water, they hope to extend the project to power homes while reducing our carbon footprint. Their ambitious plan involves using solar energy to convert carbon dioxide into methanol, its combustive cousin. At night, a power plant would burn that methanol as fuel, converting it back into carbon dioxide, which it would capture and store for later. The next time the sun came out, the process would begin again, effectively recycling carbon—and potentially reducing harmful emissions.

Salt
Other methods of storing solar power involves converting the sun's energy into heat, which is then captured in thermal storage tanks. Abengoa, a renewable energy firm based in Spain, has already built several solar plants that store excess energy in molten salt, which can absorb extremely high temperatures without changing state. Abengoa recently secured yet another contract to build a salt-based 110 mega-watt solar storage plant in Chile, which should be able to store 17 hours of energy in reserve.

Between these novel technologies for storing sunlight, will solar power eventually negate the need for fossil fuels?

Wind and solar powered generation is expanding, but one challenge we face is how to store that energy when the sun isn't shining or the wind isn't blowing. Here are three innovative companies searching for breakthroughs to solve this challenge.

 
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