The popular belief is that renewable energy can be made to “work” by using storage whereby excess capacity is used to charge something up, be it a battery, pumped hydro, compressed air storage or even the lifting and lowering of weights from storage “towers” and then releasing the “stored energy” when it is needed.As all politicians’ promise that they will rid us of the nasty fossil fuels and give us all clean green wind and solar I thought I would see what was involved in getting to this utopian place.
The process is a bit convoluted but bear with me.
The first step is to look at some actual data gleaned from AEMO records and find out the demand and the contribution to meeting that demand from nasty fossil fuels and lovely renewables. The only actual records I have are for 2018, (thanks to Andrew Miskelly), so they will have to do for this illustrative example. The records give the output of every generator in the system every five minutes so the files are large, (105,000 lines for one year), and take a bit of wrangling.
The studies below are based on full renewables to provide the electricity. The demand curve is just the total of all output for the various time periods as electricity is generated to meet demand. There is no “excess electricity” sloshing around waiting for something to use it.
After finding the combined output for wind and solar for the periods under investigation the next step is to scale them up to a point where there are periods of excess capacity to “charge something up” and periods where the stored power is used and hopefully balancing them up. The first example uses January 18 and 19 2018, days where the temperatures were high and demand also. In the chart below the black line is the total demand in MW and the shaded blue area is the output of combined wind and solar scaled up by a factor of 19. Any blue shaded area above the demand line represents MWh that can be “stored” as supply exceeds demand. Note that there are 288 time intervals for one day, (24X12). The clear areas below the demand curve are the times when “stored energy” needs to be released as supply is less than demand.
See here to get the picture.
The wind and solar outputs are as they were on the actual days, but scaled up to find the level necessary to be able to “store” enough to cover the periods where demand exceeded output. In the example above the “stored energy” is about 207,000 MWh and the requirement to top up is about 195,000 MWh, so in the paddock. Note the amount to be stored, it is around 2,070 100 MWh batteries which cost about $100 million each. We also need 19 times as much wind and solar generating capacity as we had in 2018.
I then looked at some days in winter, 30 June and 1 and 2 July to see if the scale up was any different.
Here the “storage” was 496,000 MWh and the deficit was 345,000 MWh, so there needs to be 3,450 100 MWh batteries available to be “charged up”.
This analysis is illustrative only and uses data that is 3 years old but it shows the issues that we face if the future is hung on renewables and storage. The “supply” curves shown are actual data scaled up so the “intermittency/unreliability” of wind and solar is evident.
The management of a system that had to constantly balance storage and deficits on a daily basis would be fraught with complexity and it would not take much for the system to fall over completely, something like a week of wind drought for example.
I am sure that there are people who are smarter than me and who could wrangle the data better to get more definitive results but the issue of “storage” and the quantification of it is something I never hear about when the fanatics promise us the world for nothing.
This is not part of David’s post but I just found it in a recent search for Ruth Park books on Abe and it is quite appropriate to indicate the mindset of the RE groupies and their inventions.