A report on 8 February told of a plan to build a 44 MW solar system “to deliver more reliable power to the grid”. The cost would be $90 million.
I have done some research into solar systems, so thought I would look at this proposal from a state wide power consumption viewpoint.
Using AEMO numbers the daily average power consumption in SA for 2017 was 31,600 MWh.
Using a solar calculator that takes information from stations that record Typical Meteorological Year (TMY) data on solar insolation, cloudiness, temperature and whatever, the 44 MW solar system might generate 69,800 MWh in a year.
Averages are misleading and do not reflect the reality that solar system output declines significantly throughout the year as the sun angle changes in the sky. When the output is shown as monthly figures the picture becomes a bit clearer.
In summer, (December, January and February) average daily output is 252 MWh. In autumn, (March, April, and May) it is 168. In winter, (June, July and August) it is 123 MWh and in spring, (September, October and November) it is 224 MWh.
The table below shows the comparison between daily average consumption and the contribution from the solar farm.
|Season||State average daily consumption MWh||Solar contribution MWh||Solar contribution as % of daily consumption|
The output never gets to 1% of the daily consumption and when we consider the times that output is delivered it gets worse.
In January the system operates for about 11 hours but output does not become significant until around 9 a.m. and declines after 3 p.m. 90% of the daily output is between those hours but is not a constant amount ramping up from 10% at 9 a.m., reaching 13% at 12 noon and declining to 9% at 3 p.m.
In June nothing happens until 8 a.m. when output is 8%. It ramps up to 20% at noon and then falls off the cliff at 2 p.m.
How this contribution gives “more reliable power to the grid” is beyond me. The proponents also promise a “21 MW battery” which is a nonsense statement – how long will that battery be able to supply energy (MWh)? Probably 5 minutes.
People often confuse power and energy and think that “adding 44 MW” to the system means something rather than looking at things in the context of the contribution to consumption, (MWh). In this case, that contribution is negligible, variable, and intermittent and of no real use except for the proponents to garner renewable energy subsidies, without which there would be no business case.