Energy Storage: An Introduction
Featuring a recap of 2020.
Electricity generation from most renewable energy sources is intermittent, meaning, they do not always produce electricity when we need it. For example, solar power generation is dependent on the number of daylight hours. Because of this, energy storage is crucial to the development of renewables. Energy storage works by caching or collecting excess energy produced during peak generation times for future use. Selecting what storage technology to use is dependent on different factors such as cost, efficiency, and discharge time.
Energy storage is also very important to ensure electricity grid stability. Fluctuations in energy generation as a result of the intermittency of supply and change in energy demand, can have adverse effects on the national grid resulting in blackouts and damage to equipment. Using a storage solution smoothens the demand and supply curve. With that being said, here are 5 energy storage solutions currently being implemented at the utility scale:
Pumped Hydroelectric
Pumped hydroelectric storage is the most prevalent form of grid-scale electrical storage accounting for up to 95% of the global electricity storage capacity.
It works by using excess energy generated during peak times to pump water from a low reservoir to a high reservoir. When electrical power is needed, the stored water is released through turbines to produce electricity. An example is the Guangdong Pumped Storage Power Station in China.
The pumped hydroelectric has a considerably long discharge time meaning it can supply electricity for long periods dependent on certain factors. Its efficiency depends on the difference in height between the two reservoirs.
Compressed Air Energy Storage (CAES)
For the CAES, air is the energy carrier and it is compressed and stored in salt caverns. When electrical energy is required, the compressed air drives gas turbines to produce electricity.
The real challenge about using the CAES is finding a suitable cave for storage; one that would be impermeable to air and strong enough to withstand the risk of weakening surrounding rocks. The CAES is a utility-scale storage solution although competition for space with other resources, like hydrogen constitutes a challenge.
Hydrogen
Hydrogen storage has to be my 'favourite' energy storage solution because unlike the aforementioned, hydrogen is multi-purposed. Beyond storage, it can be used in a range of different other ways like for transport as in the fuel-cell electric vehicles. Being a low-carbon energy source that can easily be produced from the electrolysis of water, hydrogen is one of the most important energy carriers.
How does it work? Off-peak power is used to make hydrogen that is then stored. When electrical power is required, the stored hydrogen is used as fuel. Hydrogen can be stored physically or chemically through reactions to form compounds.
Flow Battery
The flow battery works like a car battery except that those metal rods (electrodes) are replaced with chemical (electrolytic) compounds that produce electricity by flowing from one end of the battery to the other through a membrane.
Flow batteries have a long life span of up to 30 years depending on the electrolyte and can be used to produce power in MW for long durations.
Flywheels
As the name implies, the flywheel is a 'wheel that spins' - a mechanical device that stores energy in form of kinetic energy. The faster it spins, the more energy it stores. It is usually used for grid support and backup operations during power outages because it can store an enormous amount of energy and discharge in a short time.
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I wrote this article to give a brief introduction into the major energy storage options available. Of course, there is more to know. Stay tuned for more.
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2020: A Recap
It is now undeniable that the oil and gas industry is changing.
The industry has suffered from the double economic impacts of the pandemic and crashes in oil prices. As a result, E & P companies are beginning to make huge investments in renewable energy to add to their portfolio. For instance, Total acquired a 51% stake in the 1,140 MW SSE Renewables' Seagreen offshore wind farm project.
Looking beyond 2020, it is imminent that pressures from environmental stakeholders will continue cause oil and gas companies to focus on clean energy technologies. What would this mean for Africa and her heavy reliance on oil and gas? It is time to double our efforts and pressure our leaders into delivering on promises and joining the global effort for carbon neutrality.