Work is under way to expand a novel renewable energy-plus-battery energy storage plant in South Australia.
The facility already ranks as one of the world’s largest such installations. With the expansion, the battery system will be able to provide inertia to the local grid, a critical service that enables battery energy storage to act like a traditional power plant.
All of this is taking place at South Australia’s Hornsdale Power Reserve, which is located next to a 315 megawatt (MW) wind farm. At 100MW/129MWh, the Hornsdale BESS plays host to one of the world’s largest arrays of lithium-ion batteries.
The batteries are supplied by Tesla and are similar to what the company uses in its electric vehicles. The wind farm and storage facility were developed and are operated by Neoen, a France-based company.
Last November Neoen, the South Australian Government, the Australian Renewable Energy Agency and the Clean Energy Finance Corp., announced plans to expand the Hornsdale facility. The 50MW/ 64.5MWh expansion is intended to demonstrate the potential for battery storage to provide inertia services that are critical to integrating still more renewable energy onto the grid.
For those of us who have forgotten our high school physics, the U.S. National Renewable Energy Laboratory explains inertia this way.
Inertia in power systems refers to the energy that is stored in large rotating generators and some industrial motors. This stored energy gives the equipment the tendency to remain rotating which itself is critical to maintain a constant frequency on the grid. The U.S. grid operates at a frequency of 60 Hertz (Hz) and Australia (along with much of the rest of the world) operates at 50Hz.
Conventional fossil, nuclear and hydropower generators have plenty of inertia in them because their main feature is a spinning generator. But renewable energy sources are different. Wind, solar photovoltaics and battery storage are known as inverter-based systems that do not inherently provide inertia.
NREL explains that by using power electronics, inverter-based resources can detect frequency deviations and respond to system imbalances. These electronic-based resources can enable frequency response rates that are many times faster than traditional mechanical responses available from conventional generators.
What’s interesting is that such “ancillary services” are worth money to grid operators. The idea is for BESS to be used for an ever expanding range of services, improving the technology’s investment outlook.
(Read “BESS, you is my storage now.”)
Texas offers worthwhile experience in managing lots of renewable energy alongside the need for inertia. The Lone Start State operates its own electric grid that is largely independent of the rest of the North American grid. It’s also the smallest of the three main grids. (The other two are know as the Eastern Interconnection and the Western Interconnection.)
NREL says that Texas’s separate grid, along with its nation-leading deployment of wind energy resources, has led it to make up for declining inertia by adopting solutions such as allowing fast-responding noncritical loads (like some industrial customers) to respond to changes in frequency.
Approaches like these have enabled the Texas grid to achieve increasingly high wind penetration, reaching nearly 60% at one point last year, while also maintaining reliability.
In South Australia, the expanded Hornsdale Power Reserve will use what Tesla calls its Virtual Machine Mode. This allows power inverters to emulate inertia services that traditionally were supplied by fossil fuel power plants. As planned, the inertia provided by the Hornsdale expansion could match half of the region’s total inertia requirements.
Keep all this in mind as we shift focus to the UK where, earlier this month, the energy regulator Ofgem approved Tesla’s request to become an energy producer. Tesla plans to use a system similar to what is deployed at Hornsdale Power Reserve to create a virtual power plant.
As I’ve discussed in earlier blogs, one beauty of BESS is its scalability. You can have a “world’s largest” installation as in South Australia or–and this is one scenario being tossed around in the UK–a more distributed approach based on electric vehicle batteries.
In such a scenario, hundreds of electric vehicle batteries could be bundled together and used to simulate a utility-scale power plant. Imagine parking your electric vehicle and plugging it into the available charging system. While you work or run errands, the charging system uses a portion of your battery’s stored energy to make up an energy resource that could help maintain grid reliability. As the battery’s owner, you get paid for allowing your EV to be used this way.
The Hornsdale Power Reserve project is one example of how conventional power plant services can be replicated by systems that are based on renewable energy and storage. Going a step further, the approval of Tesla’s UK bid to become a power producer shows how non-utility firms are not only exploring novel ways to produce and use renewable energy but also schemes that redefine what a vehicle can do.
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The Hornsdale Power Reserve in South Australia. The photo comes from the Hornsdale web site.