Tasmanian Electricity System Status Report #01

Date: 8th June 2016

Purpose: This post provides a status report on the electricity system of Tasmania, mainly from a systems engineering point of view.

Summary

• Basslink is still down
• The Gordon and Esk hydro basins have at last begun the long process of reservoir recovery, after the reckless and unnecessary over-consumption of water of recent years
• The Derwent basin is still generating large amounts of electrical energy, whilst gas and diesel generators are idle, slowing the recovery in its lake levels
• Peak demands of almost 1600 MW have been seen in recent days as the weather has turned cold and frosty, and the AEMO had to issue a formal notice of low reserve capacity on 1st June

Recent Generator Output

The following series of figures shows daily average MW outputs of each hydro basin and of wind, gas and diesel generators from 1st March 2016, together with (for the hydro basins) the same data for 2015 (from 2nd May only). The fourth figure in the series shows the daily average, minimum and maximum demands, deduced from 5-minute generator data.

Figure above: The Gordon and Esk reservoir generators have at last been able to go to almost zero output, which they should do during every rainy season; the 2015 data (dots) shows how badly this “rule” was violated last year. In contrast, the Derwent basin is generating around 350 MW, preventing any strong recovery in its highly depleted reservoirs (see later for hydro storage data).

Figure above: The three small hydro basins are generating substantial amounts of electricity, probably reflecting high water inflow in recent weeks.

Figure above: Gas and diesel generators played a substantial role during March and April, but have been largely idle in recent weeks. Why have they not been used more in May to allow the Derwent hydro basin storage to recover more quickly?

Figure above: Demand rose as expected as the weather cooled, with peak demands of nearly 1600 MW in recent days. The AEMO issued a low reserve notice on 1st June (a low wind day): http://www.aemo.com.au/AEMO%20Home/Market%20Notices/0053574

Hydro Basin Storage

The following figure shows the data from Hydro Tasmania on the lake water storage levels, summed over the lakes in each basin. The figure also shows how dangerously low the hydro storage levels have become, by projecting them forward in time with no water inflow (as happens during droughts) and 40% capacity factor generation of electricity, giving around 1GW of electricity, but only until spring of this year, after which only the Esk reservoir would remain:

Conclusions

High water inflow, and new gas and diesel generation have allowed the Tasmanian electricity system to continue to operate without Basslink, with some recovery in reservoir storage levels, but why install gas and diesel generators and then not use them fully to give more reservoir recovery, in the Derwent system in particular?