For almost a century, electricity generation and distribution were treated as a tightly integrated system: it was designed and built as one, and is meant to operate as designed.

However, the chaotic delivery of wind and solar have all but trashed the electricity generation and delivery system, as we know it. Germany, California and South Australia are only the most obvious examples.

Unable to fend off their critics, the narrative among renewable energy rent-seekers quickly shifted their narrative to “grid-scale storage”, like they’d forgotten the bread and milk on their way home from work.

For wind and solar acolytes, physics and economics are boring impediments. However, the colossal cost of giant lithium batteries means that – between now and kingdom come – their contribution to our electrical supply will remain laughably trivial. Rafe Champion provides a helpful description and analysis of why battery storage will never save wind and solar from their inherent and hopeless intermittency.

The Capacity of Big Batteries
Catallaxy Files
Rafe Champion
3 July 2021

You have probably heard about “big batteries” that are expected to keep the lights on as we negotiate the green energy transition from conventional power to renewable energy. For example a 600MW battery has been suggested to partially replace the Liddell coal-fired power station when it is phased out in 2023.

As the green energy transition proceeds the intermittent input from wind and solar will have to be “firmed” (backed up) by “dispatchable” power – that is power that is available on demand – from some combination of gas turbines, battery storage and pumped hydro reservoirs.

Batteries are prominent in planning at present and this calls for close attention to the feasibility and the cost of battery storage. A previous note estimated the cost of battery storage for a single wind farm.

The critical issue is the capacity of batteries.  As explained in the note, the capacity of batteries is so small compared with the demand of the grid that it is not helpful to think of “big” batteries as grid-scale storage to provide dispatchable power.

The Hornsdale battery holds 194MWh, that is one fifth of a GigawattHour (GWh). Compare with the amount of power that flows through the NEM in the course of the day. The “depth” of the stream of power varies from 18GW (18,000MW) to 37GW (37,000MW) at the peak of demand during summer heatwaves. The figure below shows how the demand rises from the low point in the small hours of the morning to meet the demand at breakfast time, then settles during the day to rise again to the daily peak at dinnertime. The peak of demand lately did not exceed 30GW and so the calculations underestimate the amount required at the peak of demand near 37GW.  It is not necessary to be more precise to make the point about the relative amount of power in “big” batteries compared with the grid.

Allowing an average flow of 25000MW for the 24 hour daythe total amount of power required is 600,000MWh, that is 3000 Hornsdale units.

The Capacity of Big Batteries

We are informed by AEMO that the energy transition is inevitable. “This system is now experiencing the biggest and fastest transformational change in the world.”

At least 15GW of coal power is expected to close by 2040, to be replaced by some 36GW of wind and solar power.

The intermittent input from wind and solar will have to be “firmed” (backed up) by “dispatchable” power from some combination of gas generation, storage in batteries and storage in pumped hydro reservoirs.

A Wood Mackenzie survey found that Australian companies have plans to build 9.2GWh (gigawatt-hours) of battery storage but only 4% of these projects have started construction. In other words hardly any battery storage is operating or under construction at present.

Critical issue. The capacity and the cost of “big” batteries. A previous note estimated the cost of battery storage for a single wind farm.
https://www.riteon.org.au/netzero-casualties/#214

The dual function of big batteries
One of the planned functions of big batteries is to provide almost instantaneous inputs to counter sudden falls in the supply of wind or solar power that were signalled in this note on fluctuations in the wind supply.

https://www.riteon.org.au/netzero-casualties/#216

The other function that is (hopefully) planned is to provide substantial amounts of power to cover periods of high demand (dinnertime) and periods when there is little or no wind and solar power (windless nights.)  This proposal is not realistic due to the limited capacity of “big batteries’ compared with the amount of power required in the grid.

The limited capacity of “big batteries”
Consider the amount of power stored in the Hornsdale Power Reserve, the official name of the Elon Musk Big Battery installed at the Hornsdale wind farm in 2017. It was billed as the biggest battery storage unit in the world at the time and it occupied a hectare with a cost of $90 million for 129 MWh of power. In 2020 the second phase added 65MWh at a cost of $71 million. That is $1.1 million per MWh compared with $700,000 per MWh for the first phase. This is surprising, assuming that most of the infrastructure supporting the battery (land, cabling etc) that was purchased and constructed during Phase 1 is common to Phase 2. That should reduce the cost especially as we are assured that the price of storage is “plummeting.”

Big battery capacities are often reported in MW and not MWh. The difference is critical because the MW figure indicates the depth of the flow  or the size of the pipe if you want to think about it like that and the figure for MWh indicates the quantity or the amount of power that flows through the “pipe.”

There are reports of two-hour, four-hour and even eight-hour batteries and we need to know the depth of flow in MW in addition to the period of the flow in hours to know precisely how much storage capacity can be delivered.

To be clear about the limited capacity of big batteries, compare the 194MWh of power stored in the Hornsdale Power Reserve with the amount of power consumed in the state of South Australia. The depth of the stream of power in the grid varies over the range of 1000MW to 2,500MW depending on the time of day and the season. Allowing 1,500MW for the purpose of estimation, that translates into a daily flow of 36,000MWh. That is equivalent to the capacity of 185 Hornsdale batteries.

With the cost in the vicinity of $200 million per unit, that amount of battery storage is clearly out of the question even when the number of units is reduced to take account of solar power during the day. Many more would be required to allow for wind droughts that exceed 24 hours, as occurred in June 2020.

https://www.riteon.org.au/netzero-casualties/#202

In the whole of the National Energy Market covering all the states in SE Australia the “depth” of the stream of power in the grid varies from 18GW (18,000MW) to 37GW (37,000MW) at the peak of demand during summer heatwaves. The figure below shows how the demand rises from the low point in the small hours of the morning to meet the demand at breakfast time, then settles during the day to rise again to the daily peak at dinnertime. The peak of demand lately did not exceed 30GW and so the calculations underestimate the amount of required at the peak of demand near 37GW.  It is not necessary to be more precise to make the point about the relative amount of power in “big” batteries compared with the grid.

Allowing an average flow of 25000MW for the 24 hour day, the total amount of power required is 600,000MWh, that is 3000 Hornsdale units.

Catallaxy Files

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July 28, 2021