Electricity is not only created when it’s needed but also stored on a large scale for easier distribution in response to its demands and supply, which is what necessitates grid energy storage. And with the advancement of renewable energy production around the world, the future of grid energy storage is slowly shifting from complete dependency on fossil fuels to throwing renewable energy sources (RES) into the mix, and ultimately only utilising RES in the production and distribution of energy for a cleaner environment.
According to Science Direct, “Energy storage is defined as the conversion of electrical energy from a power network into a form in which it can be stored until converted back to electrical energy”.
In essence, methods of energy storage work the same as the battery of your mobile phone. If you have to constantly keep your phone plugged in to use it, it will tend to put some restraints on its most basic uses, like being an actual “mobile phone” instead of becoming a “dormant phone”. That wasn’t the idea at first, was it?
Creating a battery pack that can be recharged at your convenience with the ability to hold the “electrical energy” needed to keep your mobile phone running while you go about your daily activities was a better answer to the dormant phone debacle, and now this idea is being innovatively recreated on a larger scale. Think, massive energy storage plants like silo farms, except for energy.
Importance of Grid Energy Storage
Yale Environment says that “experts believe widespread energy storage is key to expanding the reach of renewables and speeding the transition to a carbon-free power grid”. Over time batteries have been observed to be capable of storing and discharging energy exceeding periods that consistently become longer, making power capacity expand exponentially.
There is always a need to store excess energy for increased demand, and with renewable energy sources, the need is mostly tied to the uncontrollable variations in weather patterns.
For example, you can get solar energy during the day when the sun is out, but what happens at night when electrical energy is needed?
Or, in the situation where we can get the bulk of hydroelectric power from large water sources, but these sources are disturbed especially in rainy seasons?
The answer will turn out to be that energy that has already been produced will have to be pooled from elsewhere. Like mobile phone batteries just lying in wait for when needed, a wider variety of grid energy storage options are essential, so that there will be less dependency on the fluctuations or variations in weather or energy sources.
What are the Grid Energy Storage Options?
The electrical grids need a stable system that provides a balance between supply and distribution, many methods have been applied since the discovery of electricity to keep up with these demands so here are a few energy storage options that can be integrated into the grid systems that are worthy of note:
1. Tesla Powerwall/Powerpacks
These are lithium-ion batteries for home and grid use. According to Tesla “Powerpacks house, the world’s most sophisticated batteries with AC-connected energy storage system and everything needed to connect to a building or utility network. It dramatically simplifies installation, integration and future support, offering system-wide benefits that far outweigh those of standalone batteries.” It focuses on peak shaving, load shifting, emergency backup and demand response. A persuasive example is Hornsdale Power Reserve in Australia, where it was commissioned in 2017.
2. Redox flow batteries
These are a special kind of electrochemical battery cells that allow chemical energy provided by to chemical components that are dissolved in liquids that are pushed through the system on separate sides of a membrane to create stored energy. Essentially chemical energy is turned into electrical energy through reversible oxidation and reduction.
3. Flywheel energy storage
These can be found on wind farms such as that owned by the KEA electric cooperative in Alaska. This ETS harnesses the power of the wind to create and store energy. It works by accelerating a flywheel rotor to immense speeds of about 20,000 to 50,000 RPMs and keeping the energy in the system as rotational energy that can be extracted when needed.
4. Thermal energy storage
These are mainly used for heating and cooling applications. The idea behind this EST is to heat or cool a storage medium so that the energy stored within can be utilised when needed. The most popular of which is sensible heat storage which concentrates on storing thermal heat by raising the temperature of a solid or liquid, examples are gravel, ground or soil, pebbles and bricks. The Crescent Dunes solar energy project in Nevada is an example of this ETS that can store up to 1.1 GWh of energy which is equal to 10 hours of full power energy setting it apart from most of its predecessors.
5. Pumped-storage hydroelectric stations
These follow the process of electrically pumping water from a lower reservoir to an upper one where the hydroelectric station will then contain the water to create and store more energy. They are used during off-peak seasons to store water that can be used to generate energy when needed at peak seasons. An example is the Grand Maison Dam can power up within three minutes to feed up to 1.8GW of electricity into the French national electrical grid during peak demand.
6. Compressed air energy storage
This sees air becoming pressurised and stored underground until it’s needed, similarly to the process of hydroelectric energy conversion and storage. Excess electrical energy is stored as high-pressure air in large tanks or salt caverns and spaces. To revert it to electrical energy, the compressed air is pushed through a turbine. The Pacific Northwest National Laboratory and Bonneville Power Administration have undertaken a project to “evaluate the technical and economic feasibility of developing compressed air energy storage in the unique geologic setting of inland Washington”.
At Hive Power, we strongly believe that the future relies on the cohesive synergy of all these elements, technologies and innovations. Power generation, infrastructure, energy sources, and storage grids need to be designed to feed off each other producing stable and reliable energy sources for day to day use while also helping to reduce fossil fuel emissions. The future of Grid energy storage is smart, renewable and sustainable.
As an energy consumer, your general expectation is for the lights to go on whenever you flip a switch. When you plug a device into any socket in your home, you expect the power to flow immediately. That’s if you have paid your bills on time of course.
You may base your expectations on your trust of the regional electricity grid, which works on the premise that the grid has an endless supply of power. Yet, the truth is far more intricate. This article focuses on how your electric grid works and the role played by lithium-ion batteries.
The Grid: What is it, and how does it work?
The electricity you use in your home or workplace is delivered to you through a complex network of power transmission lines. These power transmission lines and their electrical components collectively make up the electrical grid network.
The grid is designed to deliver power seamlessly whenever you need it. However, the distribution of electricity is a lot more complicated than flipping a switch. The grid connects you to a wide variety of electric power producers from various locations. These power plants also generate electricity from a wide range of sources, including fossil fuels, solar, wind, and hydropower, among others. The grid relies on several tech solutions to do its job effectively.
The Grid: Managing Electricity Demand and Supply
Electricity presents a façade that it is always available in your power outlets waiting to be used, because, when you flip your switch, the grid delivers your power immediately. Yet, the production and consumption of electricity vary throughout a 24-hour cycle.
Your grid operators are continually adjusting power systems to balance the different supply and demand of electricity. During the day, most of the power in urban centres are consumed in offices and factories when people go to work. Yet at night, the bulk of electricity demand is in residential areas to power and light up homes.
The growing popularity of renewable energy has added to the dynamics that grid operators face. The power output of most renewable energy plants varies according to the availability of the resource, which is evident in the cases of wind and solar energy. Wind power is only available when it is windy and solar energy when it is sunny. As such, the grid operators need to manage their electricity supply as well to enhance reliability.
Various countries in Europe and other parts of the world have prioritized renewable energy supply. In these cases, electricity generated from renewable resources must be purchased immediately. Yet, renewable energy plants often produce more power than the grid requires. The grid operators can shut down fossil fuels and thermal power plant to preserve fuel when the electricity demand is low. Yet, you cannot switch off the sun or wind. This excess supply of electricity is the reason for the development of Grid Energy Storage systems.
Understanding Grid Energy Storage
Grid energy storage is also known as large-scale energy storage. By definition, the reference to the storage of excess electricity is a paradox because electricity itself cannot be stored1. However, you can convert it to other forms of energy that can be stored and turned back to electricity on demand. This conversion of electricity into storable energy forms is the technology behind Grid Energy Storage.
The most common type of grid energy storage is used in hydroelectric power systems. When electricity is cheap, or demand is low, the plant operators pump water to a high dam or reservoir. This water is then released during peak demand through pipes to drive power turbines1. Several other types of grid energy storage include batteries, rail energy, flywheels, supercapacitors, and others.
Lithium-Ion Battery Storage Power Stations
Batteries work by converting electricity into chemical energy which can easily generate electricity on demand. The power stored in batteries can only be produced as a direct current (DC). Yet, the grid typically operates with alternating current (AC). As such, battery storage power stations need additional electronic components such as inverters to convert the DC power to AC.
The use of batteries to support the grid began in the 1980s with lead-acid batteries. As different minerals and technologies reduced in price, Nickel-Cadmium and Sodium-Sulphur batteries became popular. Since 2010, Lithium-Ion batteries (LIB) became the technology of choice for small and large scale storage applications.
The popularity of Lithium-ion Battery for Grid Storage
Lithium-ion batteries currently represent more than 90% of the grid battery storage systems in the world. The cost of lithium batteries has been consistency going down over the past ten years. Like solar energy, the reduced prices have made the lithium-ion technology significantly profitable.
As such, more grid utilities are moving away from conventional batteries and investing in lithium-ion batteries for power storage. In the US, utility providers have moved from using about 80.6 MWh in storage in 2013 to almost 650 MWh in 20172. Apart from affordability, here are a few reasons why Lithium-Ion batteries are becoming increasingly popular.
Lithium’s High Energy Density
Energy density is the amount of energy a battery contains per unit of mass or capacity. Defining the density of a battery by its weight is termed as Gravimetric Energy Density. It is measured in Watt-hours per kilogram (W-hr/Kg).
If you define the energy density by the capacity of the battery, it is called volumetric energy density. Lithium-ion batteries are so popular because lithium contains the highest energy densities in the world.
Applications of Lithium-ion Batteries
If you are familiar with stand-alone solar home systems, you know they use battery banks to provide power at night. However, batteries for grid storage have a more extensive range of applications. You can design these systems to fill the gaps created by inadequacies in the grid. These include
- Short-term Peak Power
- Shaving Power peaks
- Ancillary Services
- Frequency Response Reserve
- Power Outage
Short-term Peak Power Supply
Power supply systems have two types of power regimes. These are the Continuous Power and Peak Power. The Continuous Power is the amount of power that can be supplied sustainably without interruption.
Alternatively, Peak Power is the maximum amount of power that a power supply can sustain. It can only be sustained for short periods ranging from milliseconds to seconds. If it is supplied for more than a few seconds, it can damage the power supply or appliances.
Several motorized electromechanical appliances draw higher amounts of power when starting up than during regular operation. These appliances may require up to three times more power to start. Examples of such devices are fans, actuators, pumps, and others.
Lithium-ion battery storage can provide the additional instantaneous power needed during peak surge power. This setup can save the grid operator from using expensive electricity sources and peaking power plants to meet the gap in the power supply.
Peak Shaving Applications
Electricity markets are not only driven by power supply but also electricity demand trends. Commercial power consumers understand that the grid electricity rates vary throughout the day. In moments when demand is low, the system charges you on off-peak rates. Yet when the demand is high, energy is supplied at premium prices.
Peak shaving refers to the use of alternative power sources to meet the electricity demand during peak hours keeping your utility costs low without changing your schedules or outputs.
Lithium-ion grid storage systems are excellent for peak shaving applications. During off-peak hours, battery storage power stations can use cheap electricity to charge the lithium-ion battery banks. They can then sell it at a profit during peak hours.
Peak shaving is also gaining popularity with domestic users in demand-side management applications. Home owners charge their lithium-ion batteries using free solar energy during the day. They then consume it at night when utility rates are high.
Smart technologies come in handy when setting up peak shaving applications. You can configure your system to automatically switch between grid power and battery power during peak hours to save money.
Lithium-ion batteries for Ancillary Services
Like any complex system, the electric grid often experiences inadequacies or delivery gaps. These are circumstances that result in an interruption in power supply to its customers.
The regular generation and transmission of electricity play a key role in maintaining grid stability and security. Yet there are still various cases when it is inefficient. Ancillary services maintain the stability and security of the grid when regular generation and transmission operations are inadequate.
Ancillary services were conventionally performed using power generators. However, advances in energy storage technology have increased the grid operators’ options. Ancillary services are now powered by Lithium-ion battery storage power plants, electric vehicles, and renewable energy plants. The list below is some of the most common ancillary services provided by the electrical grid.
- Operating and Spinning Reserves
- Voltage Control
- Scheduling and dispatch of electricity
- Loss compensation
Grid energy storage is an ever-growing market with immense potential. The perpetual evolution of the power supply industry demands consistent innovation and reinvention of technology. Lithium-ion batteries provide a competitive, reliable and cost-effective solution in the energy storage space.