04/09/2017
Renewable energy sources like wind and solar are intermittent power sources and often rely on the electricity grid, which includes coal and gas plants to provide power when the sun is not shining or the wind is not blowing. Batteries provide a solution to integrate renewables to the grid without compromising the quality of supply.
Batteries are also capable of providing ancillary services such as frequency regulation, i.e. they can settle the differences caused by fluctuations in generation and loads and maintain the system frequency at 50Hz. A battery system that is connected to the grid can increase or decrease its output when there is a momentary shortfall of generation or excess generation.
Different battery types
There are several types of battery technologies at different levels of maturity and technical features:
- Lithium-ion (Li-ion), which is often perceived to be the leading technology because it has benefited from a concerted research and development effort, mostly because the Li ion is commonly used in consumer electronics and is common in both hybrid and electric vehicles. These batteries have relatively high energy efficiencies and energy densities.
- Lead acid, which is a mature technology commonly used in vehicles and for substation supplies. They have a relatively short cycle life and are low energy density.
- Sodium sulphur, which are batteries consisting of molten sulphur at the cathode and sodium at the anode. These batteries have relatively high energy densities and low self-discharge.
- Flow battery technologies i.e. Vanadium Redox (VRB), Zinc Bromide. Flow battery technology typically uses two different tanks of reactants to store the electrical energy. VRB is considered a reasonably well developed flow type battery technology, which now has significant field experience. These batteries generally have a long calendar life with access to full battery capacity.
So, which technology is best to use? It depends on the application, location and the size (MW/MWh) of the energy storage device.
Benefits and challenges of large scale batteries vs home batteries
In addition to integration of renewables, batteries can provide energy arbitrage – charging the battery when the electricity price is low and discharging when the price is high.
Large scale batteries can also differ transmission upgrades and relieve congestion – for instance, installing a battery downstream of a transmission line, where the loading of the line is reaching its design capacity during peak demand periods.
In households, battery systems are usually installed together with rooftop solar PV. This allows the household to store the excess power during day time and use it during peak demand. This is particularly attractive to households, which are no longer eligible for premium feed in tariffs. A typical house in Victoria earns around 6c/kWh for solar power fed into the grid. But they pay a much higher price to purchase electricity from the grid at around 30c/kWh. A household with battery storage can utilise the stored energy during peak demand periods.
The challenge with both home and large scale battery is capital cost. However, as technology matures the costs of batteries are coming down, making them more attractive. Safety is another area of concern. In households it is important that installations are carried out by an accredited installer.
Early this year Standard Australia released a roadmap for energy storage standards to support standardisation efforts in electrical energy storage. Safety of installation, product standards, grid connection, recycling, handling and transport, training and international participations were identified as priorities.
One pertinent parting thought
In the middle of difficulty lies opportunity.
-Albert Einstein
Implementing battery storage especially at grid scale is challenging but it is an opportunity that we need to take advantage of and work out the best way of handling our market and system models for future security and operation of our electricity system.