The Return of Basslink

The Basslink interconnector between Tasmania and the mainland was restored to service at 12 noon EST on 13th June 2016, and immediately started exporting electricity to the mainland. Is Hydro Tasmania repeating the mistakes of recent years, making money by running down hydro storage reserves? This post says no, at least not yet.

Monday 13th June 2016 was a public holiday, so I present here the data for 14th June, a working day with a relatively normal demand cycle. The following figure shows 5-minute demand and supply data for the 14th June 2016. The demand was obtained by summing electricity supply over all Tasmanian generators, and subtracting the metered MW flow of Basslink. For comparison, the same data are also shown for roughly the same day in 2015.

14th June 2016:

Bass_return_01

Tasmanian total supply (in blue) exceeded demand (in red), so Tasmania was an energy exporter, especially at night. The figure above also shows the outputs of key hydro basins, each of which has large but currently highly depleted water storage reservoirs. The Derwent basin appears to be operated in a “baseload” mode, probably with most water coming from its small storage reservoirs, many of which are spilling at this rainy time of the year. The Gordan and Esk generators were mostly OFF, as they should be at this time of year, in order to allow their storage lakes to replenish, in preparation for the forthcoming “dry” season (spring/summer).

18th June 2015:

Bass_return_02

The data shown above are typical of working days in May and June 2015, showing the daily roller-coaster ride that the Tasmanian electricity generators were subjected to in those (and other) months. The Derwent generators operated in what appears to be their normal “baseload” mode, but the Gordon and Esk generators were turned on to a high output at around 6 am, as must have been several others, as Tasmania switched from being an importer at night to a major exporter for the rest of the day. On that day (and many others) Tasmania unnecessarily traded its water storage in the Esk and Gordon reservoirs for income.

Some commentators have tried to defend Hydro Tasmania, pointing out that Tasmania switched to being a net electricity importer later in 2015, but importing electricity in the “dry” season does not replenish water storage reservoirs. The problem does not lie with the net import/export of electricity, it lies with the net gain/loss of water. Water management should be the boss of money management for the hydro-dominated electricity system of Tasmania.

Conclusions

So far, Tasmania has used the re-connection of Basslink to export a modest surplus of electricity, probably due to a combination of relatively mild (lowish demand), recently wet (spilling small hydro storages) and currently windy weather, and is acting prudently to replenish its highly depleted large water storage reservoirs.

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