The basic principle of batteries is simple: they store electricity in chemical form, and then provide it back through an opposite chemical reaction. The process can be repeated many times if the battery is rechargeable, and the number of cycles that a battery can tolerate changes depending on its composition. For example, while lead-acid batteries tend to last from 500 to 1,000 cycles, lithium-ion batteries last between 2,000 and 5,000 cycles.
The applications of batteries in the energy industry are more complex than just storing and supplying energy. There are many innovative ways in which they can be deployed, which will be described in this article.
It is important to note that these applications require operating flexibility, such as that offered by lithium-ion and redox flow batteries. Lead-acid batteries suffer a drastic service life reduction when they are charged and discharged too aggressively and frequently, especially if they are not allowed to charge fully between discharge periods.
Australia and many other countries have a wholesale electricity market where the price of each megawatt-hour (MWh) changes in real time. Energy arbitrage consists on purchasing electricity when its price is low, and selling it back to the power network when it is expensive. In this case, the profit is equivalent to the difference between the sale price and purchase price of each MWh. Batteries provide a convenient technology for energy arbitrage, since they can adapt to almost any project site. The concept is also possible with pumped-storage hydroelectricity, but the technology is much more demanding in terms of site conditions.
A resilient power network is one that can continue to operate when faced with extreme conditions, with the capacity to tolerate damage to some of its elements without interrupting the power supply. Batteries can make power networks more resilient because they can act like backup generators in an emergency, and they allow isolated portions of a network to remain operational while the damage is repaired.
For example, if a region only has wind turbines and solar photovoltaic systems, it cannot be isolated due to the variable nature of these energy sources. However, if batteries are added to the mix it, can operate independently like a micro-grid.
Power network operators are faced with an ongoing challenge: demand for electricity cannot be predicted with 100% certainty, and it grows along with population. Therefore, power networks must always keep enough generation, transmission and distribution capacity to handle the highest possible demand that can be expected. However, batteries can also operate as power plants if needed by the network, while being able to accomplish other useful functions. In other words, batteries increase a power network’s ability to meet growing and unpredictable demand.
Assume a city relies on a single transmission line for its entire electricity supply. If the transmission line is taken to its limit during peak demand hours, further growth can lead to overheated lines and faults, which forces the network operator to carry out expensive reparations and upgrades. However, if a large battery array is installed to deliver part of the city’s power during peak demand hours, the transmission line is de-congested. The battery array can simply be recharged with the same transmission line during hours when power demand is low.
The example above describes how a large battery array can decongest a transmission line. The same concept can be applied to decongest distribution networks, through the use of smaller battery systems distributed throughout many homes and businesses. If both concepts are combined, both transmission lines and distribution networks can experience a load reduction, which reduces the need for expensive network upgrades.
These network upgrades are the main reason why electricity is so expensive in Australia, so preventing them can mitigate future power bill increases.
The traditional approach when managing the electric supply has been to adjust generation according to demand. However, this approach is not cost-effective, due to the existence of demand peaks. Network operators must keep peaking power plants on standby, only to be used for a few hours each day while the demand peak lasts. In addition, the network must be able to deliver all the power required during the demand peak.
A promising alternative is using energy storage to shape demand, shifting consumption to hours when the power grid is under a lighter load. This reduces dependence on peaking power plants, which have the highest operating cost.