Golden opportunity for Qld pumped hydro project

Posted 4 October 2016

Solar farm

An old Queensland gold mine is set to turn over a new leaf as a first-of-its-kind pumped hydro station.

The Genex project will exploit existing Kidston mine infrastructure and the vertical drop between two old mine pits to establish a pumped hydroelectric energy storage system (PHES), which will work in tandem with a solar farm, said Genex executive director Simon Kidston.

“What makes this site so great is there's two very, very deep reservoirs that are adjacent to each other. The site is also connected to the grid by an existing transmission line so that allows us to tap into the national electricity market (NEM),” he said.

“There's also a lot of other redundant mining infrastructure that we can utilise to lower the capital costs. For example we've got an airstrip onsite ... there are roads to site and a mine accommodation camp.”

By coincidence, Kidston is the great-great grandson of former Queensland premier, William Kidston, after whom the mine was named. 

“That mine was always owned by other people and ultimately we came along 100 years later and bought this mine from a Canadian company,” he said. 

The project comes as water professionals around the country ponder what will become of hundreds of abandoned mine pits

In the case of the old Kidston gold mine, northwest of Townsville, a 300m height differential between the deep pits will support between 1500 MWh to 2250 MWh of continuous power generation in a single generation cycle (250MW to 450MW of peaking power generation over a five to nine hour period). 

This is feasible not only due to the site's natural attributes, but also the $41 million former owners spent on rehabilitation after the mine's closure in 2001, Kidston said.

“Not every mine site would be suitable for what we're doing,” he said.

“One of the key learnings we've made is that rock integrity is critical because as you have water levels that fluctuate you've obviously got different pressures against the pit wall. We're fortunate that we've got very, very hard rock that has very good integrity.

“Since the mine closed, there's been a lot of data collected so we know what the levels of seepage, rainfall and evaporation are and it's basically very, very constant. 

“As part of the feasibility studies we've done a lot of drilling to analyse all of those issues and have concluded the pits it act as a sink so there is no real water loss into the environment or through the aquifers.”

Genex has an annual water entitlement of 4.6GL from Copperfield Dam, which is connected to the site via an 18km pipeline.

Powering the pumped storage hydro plant will be two adjacent solar farms producing a combined 300MW. 

Old gold mine

“We can use stored solar power overnight to pump water from the lower reservoir to the upper reservoir. We can then generate [hydro power] in the morning peak between 6am and 9am,” Kidston explained. 

“Then we use the power from the adjacent solar farm to recharge the upper reservoir so we can do five hours of continuous [hydro power] generation from 4.30pm to 10.30pm.”

In this way, the project has been designed to capture high price events when selling into the NEM.

It's thought to be the world's first stored hydro plant using two old mine pits, Kidston said. 

“There is an example in the UK where they're using the upper reservoir of an old slate mine and in Canada they're using an old gold mine as one of the dams but they're building another dam near it,” he said. 

The project feasibility study, completed with assistance from Hydro Tasmania's engineering arm Entura, will be released to the stock exchange in coming weeks. 

Genex hopes to begin construction around this time next year.