AWARDS FINALIST: solarZero – power system stability

SolarZero achieved a world first in late 2022 when it provided frequency response from 3200 household battery systems.

Each micro-computer in the firm’s household solar and battery system observes frequency and instructs the battery to respond to any dip in frequency within milliseconds. Using machine learning, solarZero estimates the amount of reserve available from each battery for each half-hour trading period and combines those to provide an overall reserve offer to grid operator Transpower.

The company says it worked closely with Transpower to set up the initiative. Transpower created two new virtual power stations – one in the North Island and one in the South Island – representing the aggregation of solarZero’s battery systems across the two islands.

World first

Using distributed residential battery systems to provide frequency response was a world first. Both the computer hardware and software were developed in Hamilton. Testing of the system was carried out on the grid simulator at Auckland University.

In parallel to the testing on the grid simulator, beta versions of the software were installed on a small subset of about 200 household systems around the country. Data from these systems provided information on real-world frequency variations.

The project involved multiple agencies and companies, with Transpower, the Electricity Authority, Auckland University, NZX, Panasonic New Zealand, and Torutek all playing significant roles.

The ICON

The key to the system is a computer – the ICON – developed and manufactured in New Zealand as part of solarZero’s partnership with Panasonic. The software was also developed by local firm Torutek.

The ICON has sufficient computing power for it to sense and be able to respond to a dip in frequency. It also collates the milli-second data that Transpower requires to be collected during a frequency event. The data is sent to the cloud and is stored for analysis and to provide evidence to Transpower of the company’s response to a frequency event.

Delivery

Between September 2022 and February 2023 solarZero’s systems experienced two frequency events.

The firm discovered that during a frequency event voltage at the household level dips and then rapidly rises, in some cases pushing above levels specified in the relevant standards.

Additionally, hot water ripple control relays are sometimes tripped during a frequency event. Particular types of ripple control systems create harmonics that interfere with inverters causing them to trip off in accordance with relevant NZ standards.

These were just two of the kinds of delivery performance issues solarZero engineers had to work through.

The company’s review of the industry literature suggests no one has recorded and reported frequency and voltage variations at the household level at thousands of sites at a time step of 100 milliseconds.

Stability services

As variable renewable energy resources increase on the power system, better power system stability services will be needed.

The type of initiative developed by solarZero is an important step towards providing these improved stability services and enabling the decarbonisation of the power system while maintaining power system stability.

By mid-2024 solarZero expects 15,000 of its systems to be enrolled for reserves, providing up to 80 megawatts of capacity into the reserves market.

The Innovation in Energy Award category is sponsored by Ara Ake