Are iron-flow batteries the solution to variable renewables?

For the first time Australia’s main electricity grid reached a share of over 70% for renewable energy this week, an achievement that showcases the rapid rise of solar and wind generation, but also highlights several challenges.

Australia is a world leader in renewable electricity generation and has the world’s highest penetration of rooftop solar systems per capita.

At around 1.05pm Australian Eastern Daylight Time on Oct. 24 the grid that supplies the five of the nation’s six states was powered by 72.5% renewables, with solar and wind providing 70.9% and hydro the other 1.6%.

That may sound like a remarkable achievement in a country that until recently was largely powered by coal, but it could have been even higher, possibly above 90%.

The reason total generation from renewables didn’t reach over 90% on Oct. 24 was that some renewables were curtailed, largely due to negative wholesale electricity prices, according to the website Renew Economy.

The rising share of renewables illustrates a wider problem for Australia’s grid, and those in other countries that are also seeking to transition away from fossil fuels.

Australia generates excess solar during the middle of the day, which in turn forces the ageing fleet of coal-fired generators to ramp down, before they ramp up again as the sun sets and renewable generation slides.

There are solutions to this, and all of them are variations on the theme that as the grid is fed by more and more variable renewables, you need fast-acting and variable backups.

In Australia this role has fallen to natural gas-fired peaking plants, battery storage and hydropower.

Natural gas, while cleaner than coal, still emits carbon and ultimately isn’t a long-term solution if the goal is to reach net-zero electricity generation.

The good times are over – how Eskom managed to suspend load shedding for so long

Power utility Eskom announced on Sunday that load shedding is back in full swing, with outages returning at stage 2 and stage 3 until further notice.

On Sunday (29 October), the group said that stage 2 load shedding would be implemented from 16h00, lasting until 16h00 on Monday.

After this, stage 2 and stage 3 load shedding would be rotated in the familial pattern (stage 3 from 16h00 to 05h00 and stage 2 from 05h00 to 16h00) indefinitely.

This ends the longest streak of no load shedding since permanent outages started at the tail end of 2022.

According to independent energy analyst Pieter Jordaan, last week represented the best performance in over 400 days.

“The 7-day blackout trend touched the 0%-mark on Thursday, 26 October and remained there for three days. This is the metric’s first ‘landing’ after ‘taking off’ on 6 September 2022, some 416 days prior.”

However, Jordaan noted that this milestone wasn’t necessarily a result of any significant turnaround at Eskom (even though its performance has been improving) but was only made possible by exceptionally low demand and considerable peaking effort by the Systems Operator.

“For context: (the prior week) required 118 GWh of peaking energy but (last week) had already recorded 223 GWh of peaking by Friday.

Ultimately, Eskom employed double the annual average level of Open Cycle Gas Turbine peaking last week to make the extended suspension possible.

Eskom’s stronger performance over the past few weeks has largely been thanks to lower demand. However, with colder weather hitting the country this week, the demand profile is changing.

Demand during the weeks of suspension have tracked far lower than the typical profile, and also lower than the same periods in 2021 and 2022.

This lower demand has been attributed to both a more conscientious consumer and a major boost from rooftop solar installations, which have doubled this year so far.

Credit is also due to Eskom, which has been improving plant performance. The group’s Energy Availability Factor has improved to over 60% for the first time in 2023 and is currently better than comparable periods in 2021 and 2022.

However, the improved EAF is no panacea, as it is still far below the minimum set by energy regulator Nersa (65%) and the group is still not producing enough power to meet ‘typical’ demand – so it continues to operate on that knife’s edge.

Eskom unbundling ‘milestone’ announced

The National Energy Regulator of South Africa (NERSA) has finally approved the issuing of a licence to the National Transmission Company of South Africa (NTCSA) to operate a transmission system in South Africa.

Nersa’s announcement on Friday is a milestone in Eskom’s unbundling process, which will see the power utility restructured into three separate units: generation, transmission, and distribution of electricity.

Nersa made the announcement in a statement, following a meeting on Thursday, in which it also highlighted several important decisions including the approval of a renewable energy generation licence application to Ngonyama Solar (RF) (Pty) Ltd.

This was part of its rationale for agreeing with the draft ministerial determination for the procurement of 1 000 megawatts of new generation capacity from the Cross-Border Procurement Programme, and its agreement for the procurement of 2 000 megawatts of new generation capacity from the Load-Shedding Reduction Programme.

More: Mail & Guardian

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