Your Numbers, Please

We now live in a time of high quality electricity mix visualisations, such as electricity map. For Australia, OpenNEM has rapidly become the best, not least because it makes up to a week worth of 5-minute generation data available for free.

In this spirit, please feel free to download and play with the spreadsheet calculator I’ve designed.

1. Download today’s national CSV file from OpenNEM.
2. Select and copy the entire sheet.
3. Paste it into the calculator in full.

The calculator comes with a recent, interesting week’s worth of data included. This is the chart.

By adjusting the multipliers for solar and wind capacity (this is a simplified simulation and assumes current geographical distribution across the NEM) an illustration of very high solar and wind penetration (on top of existing hydro) can be visualised. Times of high solar and/or wind result in substantial over-production. The first solution that comes to mind is to store this energy, and indeed, purely as an example, the glut of wind in the middle of the week would be shifted over to replace the coal and gas required the next day when wind is practically absent – even at eight times the NEM’s current nameplate capacity. This is 533,000 megawatt hours (MWh) stored and then discharged to meet 477,000 MWh, accounting for the roundtrip efficiency of batteries.

All fossil fuel sources are depressed proportionally as a product of the solar and wind mutlipliers. Real world considerations such as merit order are neglected.

It is fascinating that this is

1. the same magnitude of storage required in this WattClarity analysis of a longer still interval from several years back;
2. nearly 1.5 times the capacity suggested by AGL in this presentation.

If the US$50million 129 MWh Hornsdale Energy Reserve were operated like this bulk storage (which it isn’t), over 4,100 installations would be required.

If pumped hydro such as the AU$330million 2,000 MWh Kidston Stage 2 project were used instead, more than 300 such reservoir systems would be needed. These would operate many decades longer than Li-ion batteries, but have lower roundtrip efficiency. Consider how many technically and commercially viable sites are being seriously investigated today (spoiler: it’s 20).

Based only on reported project costs, this would require from $100 billion to $272 billion just in energy storage investment.

Yeah, the need for storage is higher than people realize. For systems that are only wind/solar+storage , you must have enough storage for your longest low-RE period. No way around it. In our off-grid home work, we found you needed more than 1 week of storage in most of US.

— Eric Hittinger (@ElephantEating) June 8, 2018

This many MWh of storage could be covered by less than four Snowy 2.0 projects (no more than $29 billion) but apparently this form of storage just ain’t as good, depending on who you ask.

The cost decline of Li-ion battery storage was investigated by the Finkel review, and the $520/kWh cost estimated here was not expected to plummet close to that for Kidston ($165/kWh) before 2050.

The obvious alternative, natural gas, would cost about $32 billion for enough flexible capacity to completely fill in the gaps in question, based on the reported cost of Reeves Plains power station approved for construction in rural South Australia this year. This presents greenhouse gas emmissions issues, explored here and here, especially as any short-comings in storage output must be made up by such flexible generation.

The costs estimated above still don’t include what must be spent on expanded solar and wind capacity. According to ACOLA (page 66), to 2016 $40 billion was spend building most of what we now have. Dollars-per-kilowatt-installed costs have dropped for solar and wind to a greater or lesser extent, and I invite readers to suggest sets of cost figures in the comments below which we might use to estimate the total investment required to generate what we see in the simulation.

Furthermore, assuming realistic average annual capacity factors for the operation of the expanded renewable energy capacity, an annual total around 252 terawatt hours would be generated on the NEM, which is 28% in excess of the 196.5 TWh for 2016-2017 reported by the AER.

All of these results are predicated on the simplifications and assumptions underlying the calculator. The way it functions has been kept as straightforward as possible so as to let the raw data do the talking, but all output, such as the featured chart, is hypothetical. The actual electrical network is complex, evolving, and nobody can say for certain what we’ll “end up with”; will we see more, or less, than another 20,000 megawatts of renewable energy added to the market? What about demand destruction destruction due to electrification of transport, or even electronic currencies? The advantages of greater geographical dispersal of solar and wind power plants, as well as the drawbacks (costs of expanded transmission), are neglected, along with technical considerations of storage options such as lifecycle emissions and Energy Returned on Invested, and of system intertia and FCAS. And last but not least, grid-scale storage has not been operated like this, at such scale, anywhere ever; it’s way too easy to forget that the whole idea is still notional right now.

So, download the calculator, have a play, and look closer at headlines and claims which limit the set of energy sources to meet our many and varied challenges. Optimism is one thing, but ask yourself what the numbers might really be saying.

 

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