Last year, Tesla, with the cooperation of the South Australian government, installed rooftop solar systems coupled with Powerwall residential storage batteries on over 1,000 low-income homes. The Powerwalls are linked together into what is known as a virtual power plant. It’s just like a grid-scale storage battery except instead of being all at one location, it consists of many small energy storage nodes spread over most of South Australia. See the video below for more details.
The Australia Energy Market Operator (AEMO) has just released its first review of the VPP installation and given it excellent marks. Although the system did not respond as expected to every grid disruption event, the reasons for any failures were quickly determined and corrective action taken almost immediately. Here are three significant cases covered by the AEMO report:
9 October 2019, response to Kogan Creek trip
During this event, the largest generating unit (at Kogan Creek in Queensland) in the National Electricity Market (NEM) tripped off unexpectedly from 748 MW and power system frequency immediately dropped to 49.61 Hz, which is below the normal operating range. The SA VPP detected this frequency excursion and responded immediately to inject power into the system and aid frequency recovery.
16 November 2019, response to Victoria and South Australia regional separation
At just after 6 pm, a non-credible contingency event resulted in the electrical disconnection of the South Australian region from the rest of the NEM power system for nearly five hours. The initial separation resulted in the power system’s frequency reaching 50.85 Hz3, which meant the SA VPP was required to deliver its full amount enabled, 1 MW lower contingency FCAS. In this example, the SA VPP under-delivered FCAS.
Energy Locals and Tesla realized that fewer systems than expected had the appropriate frequency support settings enabled. This led to fewer individual units responding as part of the VPP to deliver a reduced fast lower FCAS aggregate response; this equated to 83% of the expected response, or 828 kilowatts (kW) rather than 1 MW bid.
The correct frequency settings were configured and activated upon enrolling additional systems into the SA VPP. These settings were later modified for some systems when a test was manually scheduled for the purpose of gathering data for the VPP-wide test, as described in the VPP Demonstration FCAS Specification.
A benefit of VPPs is that once identified, this issue was fixed immediately by remotely reconfiguring the non-compliant systems. Since this event, Tesla informs AEMO that it has introduced daily checks on all systems to ensure they are responding according to the expected configuration requirements. It is expected that this approach will mitigate the risk of any future under-delivery.
10 December 2019, response to frequency events
During this event, the NEM experienced both high (>50.15Hz) and then low (<49.85Hz) frequency events within 45 minutes of each other. The SA VPP responded immediately in both cases to first charge the batteries to lower system frequency, and then discharge the batteries to raise system frequency. (Shown in graph above.)
In a statement, Violette Mouchaileh, AEMO’s Executive General Manager, said: “Our report highlights how our first VPP participant, the SA VPP, performed during several events in the National Electricity Market (NEM).
“This included immediately charging and discharging batteries in response to frequency deviations following a contingency event to maintain stable NEM frequency levels, and responding to energy market signals by batteries pre-charging in anticipation of elevated prices and discharging during the elevated price event.
“As a result of accessing aggregated and controllable DER [distributed energy resources] through VPPs, the power system is supported by the provision of additional power when needed.”
Tesla plans to install a total of 50,000 rooftop solar systems and Powerwall batteries in South Australia, and this initial report will help speed that process along. In addition to helping stabilize the grid, individual homeowners are seeing a drop in utility bills of up to 20%, a welcome relief for those on limited incomes.
Tesla is also partnering with Green Mountain Power in Vermont to help it reach its goal of 100% renewable energy by 2030 with help from another virtual power plant using Tesla Powerwall batteries. So far, that program has been very successful and saved GMP customers over $1 million during one high-demand event last summer.
AEMO’s Draft 2020 Integrated System Plan forecasts that 63% of coal-fired generation in Australia will retire, the equivalent annual electricity needs of all Australian homes and a proportion of businesses. Meanwhile, DER generation capacity is expected to double or even triple, with rooftop solar to provide 22% of total energy, between 32 gigawatts (GW) and 50 GW.
Further, AEMO estimates that embedded battery storage capacity, including VPPs, will total between 17 GW and 30 GW. What this shows is that Australia is a world leader in distributed energy resources, paving the way for VPPs to significantly contribute to Australia’s future energy system. If the Tesla VPP in South Australia is working this well with only 2% of the planned systems installed, imagine the benefits that will flow to the region once all 50,000 systems are completed.
Once again, local initiatives are giving the lie to the pig-headed energy policies of Prime Minister Scott Morrison and his band of fossil fuel stooges. If the people will lead, their leaders will follow — eventually.