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Home batteries could play key role in grid management - Transpower

Wednesday 10th July 2019

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Household battery electricity storage could play an important role in managing the pressures increased solar and electric vehicle use may put on the country’s power system, Transpower says.

While the combination of solar and batteries would offer “little benefit” managing dry-year risk, the national grid operator says they could play a valuable role in smoothing loads on the network during the day, as well as improving the way the power system responds to emergencies.

Large-scale take up of solar has the potential to create issues with system frequency and voltage during the middle of the day when solar generation would be highest and power demand relatively low. Coupling that solar with battery energy storage systems – BESS – could reduce much of that risk by allowing consumers to store energy for later use, Transpower says.

“The self-consumption of excess daytime solar PV generation by consumers that BESS enables can play a significant role in mitigating the impact of large-scale uptake of solar PV in isolation,” the state-owned firm said in a 72-page report.

“If the appropriate market signals and coordination arrangements are in place, the greater the storage capacity of the BESS compared to the solar PV capacity, the greater the potential benefit to us, in terms of managing the impacts on power flow across the grid and avoiding the need for network investment.”

The battery study is the latest in a series Transpower has undertaken to help understand the role electrification – particularly of transport and industry – can play in helping meet the country’s goal of having a net-zero  carbon economy by 2050.

Work Transpower completed in 2017 suggested the existing grid could accommodate about 2 gigawatts of solar capacity with minimal impact, but 4 GW would displace a lot of existing generation and make grid management more difficult.

The country has only about 97 MW of solar currently. Total generation capacity stands at more than 9.2 GW.

Transpower’s study found, in all cases, the large midday demand trough created by widespread solar could be reduced by charging battery systems or electric vehicles. In some cases they could also contribute to reduce morning and evening peak loads as well.

Grid voltage in the upper North Island and upper South Island was most affected and Transpower expected local distribution networks in those areas would face the same issue.

John Clarke, Transpower’s operations general manager, said the findings highlight the importance of developing proper standards, codes and market arrangements for battery systems to ensure their potential benefits are realised.

“Hypothetically, the charging of 2 million EVs in New Zealand at the end of the working day, without any incentive to defer charging to later in the evening, would add 25 percent to today’s winter evening peak demand,” he said.

“The potential addition to the mix of significant EV charging requirements reinforces the need for market signals that enable coordination including from BESS installed in homes. This will manage the impacts of power flow across the grid and avoiding the need for costly network investment.”

Clarke said battery systems also have an “impressive” potential to improve the way the grid responds three to five times each year when frequency on the system drops due to the sudden loss of a large generator or the high-voltage link across Cook Strait.

“Our studies of frequency performance with BESS enabled to respond to these events demonstrated likely superior performance compared to the reserves we rely on today in such events, reducing the impacts on consumers.”


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