Batteries as an energy source

Summary: With global moves to decarbonize energy supplies, battery technologies are likely to play an increasing role by providing portable power, even without discrepancies in supply and demand of utility power, enabling new technologies.

A battery refers to an array of electrochemical cells. Cells in turn are comprised of a pair of half cells. Each half cell must have an electrode and an electrolyte. Half cells can share a common electrolyte. Cells are connected in various configurations to form batteries, which can produce more power than individual cells. Cells are an electrochemical energy source; that is, they produce electrical energy from a chemical reaction. This chemical reaction involves the electrodes and the electrolyte—or in the case of fuel cells, a special kind of battery, an external fuel source.

Batteries can be classified into two kinds: primary batteries, or nonrechargeable batteries; and secondary batteries, or rechargeable batteries. In primary batteries, a nonreversible chemical reaction occurs, which converts the chemical reactants into electricity; however, this reaction cannot easily be reversed. Conversely, secondary batteries use a reversible chemical reaction. This allows the battery to be charged and discharged, allowing the battery to be used as a temporary store for electricity. Usually, batteries are supplied in their discharged state and must be charged before use. Primary batteries result in an environmental burden, so there are moves in portable electronics to encourage the use of rechargeable batteries.

What makes secondary batteries particularly relevant in the present energy context is their ability to store energy produced by renewable sources. Fossil fuels and nuclear power are both finite energy sources. For this reason, in the medium to long term there is a need to move toward renewable forms of energy that will offer sustainable energy supplies in perpetuity. However, there are some challenges with renewable energy technologies that produce power from natural energy flows: Solar power, wind power, some implementations of hydropower technology, and wave power are all intermittent energy sources. To some degree, this problem of intermittency can be addressed by using battery technologies—storing energy in chemical form when it is abundant for later use. This is particularly relevant for rural communities without grid infrastructure. Furthermore, battery technologies may also be used as a substitute for hydrocarbon fuels in mobile applications, particularly in vehicles and transportation.

Batteries for Low-Carbon Vehicles

One of the particular areas where batteries can play a significant role in helping address energy challenges is in storing energy for mobility applications. Many vehicle technologies rely on a combination of the internal combustion engine and hydrocarbon fuels to provide motive power for movement. This presents challenges, because in burning hydrocarbon fuels, carbon emissions are produced as a by-product; furthermore, hydrocarbon fuels are in finite supply. Battery technologies can help to address this energy challenge. By storing electricity produced from clean, renewable sources, batteries can act as a vector for using electricity in mobile applications. Batteries enable the production of vehicles that have no emissions at the point of use; however, there may be emissions produced at the point of electricity generation.

In a conventional vehicle, a battery is used to: start the vehicle, provide lighting, and power ancillary convenience features. This requires a much smaller battery than the type of battery required for an all-electric vehicle; these are also known as cyclical batteries, because the alternator continuously helps to charge conventional vehicle batteries. An electric vehicle (EV) battery is what is known as a deep-cycle battery. It is designed to go from being fully charged to fully discharged. There are a range of battery chemistries that can be used in EV applications. Early electric vehicles used lead-acid batteries, a simple battery technology. While cheap to produce, the low power density of these batteries meant that early EV vehicle performance was poor by the standard of modern electric vehicles. Nevertheless, lead-acid battery powered vehicles found favor in some applications. Later electric vehicles employed nickel metal hydride batteries, a battery technology also used in home rechargeable batteries.

There have also been some technologies developed that offer the promise of greater power density and improved EV performance. The Zebra battery uses molten chloroaluminate sodium as the electrolyte. This requires the battery to be constantly heated for use, which presents some challenges for vehicle design and operation.

One technology increasingly used is lithium ion and lithium polymer battery technology. These types of batteries have been deployed in consumer electronics because of their high power density, which in mobile applications allows for small, light devices. These characteristics (the batteries’ energy density, power density, and charge/discharge efficiency) also lend themselves to electric vehicle applications. Researchers are also working to develop other technology, such as improving sodium-ion batteries, which hold tremendous potential for EVs. Batteries remain the most expensive component of battery electric vehicles, so significant effort is being invested into reducing the cost to produce EV batteries.

Bibliography

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"Types of Batteries." Pacific Northwest National Laboratory, www.pnnl.gov/explainer-articles/types-batteries. Accessed 2 Aug. 2024.