Thanks to those who read and commented on my recent post titled “Where were the renewables when we needed them”. The notes below refer to total wind only. Solar is minimal and useless.
The main criterion for electricity security is the ability for generators to meet demand at any time. When renewables boosters talk of the percentage of electricity that renewables provide they invariably use averages over a year. This is misleading because there are times when the renewables contribute virtually zero.
In the recent post I used January 18 2018 as an example because it demonstrates how low renewables output coupled with high demand puts the “fossil fuel” and hydro plants at the forefront of generation. The two days 18 and 19 January 2018 were the days of highest demand for the entire year and in both instances renewables failed to contribute much to the peak demand – see charts in previous post.
At the point of maximum demand for 18 January, (30,899 MW at 17.45), the contribution from wind was 578 MW or 1.87%. The maximum demand for 2018 was 31,844 MW on the next day, January 19 and wind supplied 6.2% at the time of maximum demand.
If the planet savers wanted renewables to supply 50% of the electricity then to meet maximum demand on the worst day the wind capacity needs to be increased by a factor of 26. For 100% the factor is 53 times. It will still be “intermittent” and on days of lesser demand the system will be hugely over capacity and output would need to be curtailed.
If the solution was to use batteries to “store excess renewable power” then 50% renewables would need 2,697 100 MWh batteries to fill the gap. At around $100 million each the cost is $269 billion. For 100% they would need 5,676 of the same for a cost off $567 billion. Batteries might last for around 10 years before needing replacement. The tricky bit would be getting them recharged in time for the next day.
The table below compares 18 Jan and 19 Jan 2018. The first column shows the maximum demand and the second the corresponding contribution by wind. The third expresses this as a percentage. The next two columns give the daily total MWh for the total system and for wind. Next shows the MWh deficit that needs to be made up if the system was “all renewables” and finally the number of 100 MWh batteries needed to store that deficit and the cost using $100 million each as a “budget” cost. Recently there have been a number of proposals put up for 100 MWh batteries in SA and the cost is given as $100 million each so I have used that number.
In terms of deficit 18 Jan is the worst day so there needs to be “storage” for 567,618 MWh and this would need to be “re-charged” to 100% to cope for the next day. “Snowy 2.0” is supposed to have a capacity to store 350,000 MWh and release it over a week – say 50,000 MWh per day – which is about 8% of the daily deficit so we would need 12 “Snowy 2.0’s” worth of storage for each day. The reasonable question to ask the renewables spruikers is “where is the “excess renewable energy” going to come from?”
Note that in terms of MWh the contribution from wind on 18 Jan was 4.74% but in terms of meeting maximum MW demand it was 1.87%. For 19 Jan the corresponding percentages were 10.53 and 6.19.
The table below shows the time that wind is less than a certain percentage of demand over the whole of 2018. The intervals in the data are every 5 minutes and although the sum of these is expressed as hours or days it does not mean the time intervals are consecutive. The maximum percentage ever reached is 19.3% and the minimum is 0.0%.
It also shows the minimum and maximum for both % demand met and capacity factor. The average % demand met over the whole year is 7.2%.