Turning an abandoned gold mine into a renewable energy hub

  • By Simon Kidston, Executive Director, Genex Power

A unique project in northern Queensland will use former mine infrastructure to deliver new stakeholder benefits

Kidston, a small township in northern Queensland, will soon experience a world-first, with the refurbishment of an abandoned gold mine into a renewable energy hub. The hub, which will be constructed by Genex Power, is located 270 km north-west of Townsville in northern Queensland. The hub will comprise three renewable energy projects: a 50 MW solar project (Kidston Solar Project Phase One 50 MW, or KSP1); a 250 MW pumped-storage hydro project (Kidston Pumped Storage Hydro Project, or KPSHP) and an additional 270 MW solar project (Kidston Solar Project Phase Two 270 MW, or KSP2). The hub will use the infrastructure remaining from one of Australia’s largest open-cut gold mines.

Background

Queensland has significantly higher peak prices and more volatility compared with other states in the National Electricity Market (NEM). Queensland’s wholesale electricity prices are expected to increase considerably over the next decade, driven by increasing peak prices, increasing electricity demand and changing generation mix.

The expected growth of large-scale renewable projects will create further volatility in electricity prices in Queensland and the NEM as a whole. More large-scale renewable projects, particularly solar projects, will reduce the electricity price during the day when solar radiation is prominent with lower consumer demand, but will be ineffective during high evening demand periods when solar radiation is reduced or absent. This will create further fluctuations in daily electricity prices due to the greater discrepancy between peak and off-peak pricing.

As large-scale solar projects are unable to produce enough electricity during times of peak evening demand, energy storage is a necessity. The KPSHP will provide the means for energy storage, and be able to produce electricity on demand during peak periods. Pumped storage hydro is the most efficient and productive method of large-scale electrical energy storage in the world, against a background of high-cost battery storage. However, pumped storage hydro requires large amounts of energy to be used during the ‘pumping cycle’ (when water is transported back from the lower to the upper reservoir). By integrating the KPSHP with the KSP2, intra-day pumping will be powered by the renewable solar project, preventing a reliance on regular grid power that is supplied by non-renewable sources.

The Kidston renewable energy hub – overview

The renewable hub will be developed using the former Kidston gold mine, which was once the largest open-cut gold mine in Australia (Centre for the Government of Queensland, 2015). Closed in 2001, the Kidston mine has a number of key remaining infrastructure pieces that Genex Power will utilise as part of the renewable energy hub, including two large mining voids now filled with significant volumes of water, a tailings storage facility, a waste rock dump, an existing transmission line and substation, an airport strip and existing road access to the site. Given this existing infrastructure, project development and construction costs will be greatly reduced in comparison to similar energy projects in Australia. State development Minister Dr Anthony Lynham has noted Kidston will be the first instance in Australia whereby a former mine has been converted into a renewable energy generator (Sourceable, 2016).

Figure 1. Kidston Solar Project Phase One 50 MW (left) and the Kidston Pumped Storage Hydro Project 250 MW (right). Click for larger image.

Kidston Solar Project Phase One 50 MW

Construction of KSP1 began in January 2017, with first generation expected in Q4 2017. The 50 MW solar project is anticipated to produce approximately 145 000 MWh of renewable energy per year, which is the equivalent of powering 26 484 homes entirely with renewable energy, and offsetting 120 000 t of CO2 per year, equivalent to removing approximately 33 000 cars from Australian roads. Energy produced from KSP1 will be supplied directly into the NEM, which covers 40 000 km of transmission lines to nine million Australian customers (AEMO, 2016). KSP1 is the only project in Australia that is located within the highest solar resource region (ie > 24 MJ per day; Figure 2) and has a pre-existing connection to the NEM.

Figure 2. Average annual solar radiation in Australia.

The tailings storage facility of the Kidston mine provides ideal terrain for a solar farm, with 310 ha of flat topography, consistent ground conditions and limited vegetation. KSP1 will be situated on this tailings storage facility, utilising these ideal conditions left from past mining practices.

Kidston Pumped Storage Hydro Project 250 MW

Pumped storage hydro is a form of energy storage whereby water is held at elevation and released down into a lower reservoir, passing through turbines and generators that produce electricity. Once the water has filled the lower reservoir, it is pumped back via reversible pump/generators to the upper reservoir. Essentially, the project is a very large battery, since water can be stored indefinitely and released immediately upon demand. Although it has similar mechanics to a standard hydroelectric scheme, pumped storage hydro differs in that it can be operated as a closed-loop design involving the movement of water between two reservoirs with virtually no external input or output (besides evaporation and precipitation). Pumped storage hydro has been around for over 100 years and is the most efficient and productive method of large-scale energy storage in the world. It currently makes up more than 99 per cent of electrical energy storage worldwide (Blakers, 2016). There are currently more than 40 pumped hydro storage schemes installed in the US, with only three in Australia.

As with the KSP1, the KPSHP will utilise the existing infrastructure left from the abandoned Kidston mine, with the two mining voids acting as integral features of the closed-loop design. The Eldridge pit will act as the lower reservoir, while the Wises pit will act as a balancing storage, capable of remediating any unexpected water gains or losses in the closed-loop system. As for the upper reservoir, this will be constructed on the top of the waste rock dump of the closed gold mine. Known as a ‘Turkey’s nest’, this design results in a greater height differential between the upper and the lower reservoir, a major factor determining the amount of generation produced. This design is illustrated in Figure 3.

Figure 3. The Kidston Pumped Storage Hydro Project.

In terms of specifications, the KPSHP will have a generation capacity of 250 MW, with the potential to operate over a continuous six-hour generation cycle, resulting in 1500 MWh of renewable energy. The purpose of pumped storage hydro is to target periods of high energy demand where prices of electricity are at a peak. Usually there are two peak periods within a day: a morning period and a longer evening period. The KPSHP will run in ‘generation mode’ during these times. Once these periods have passed, the system will start the ‘pumping mode’, where water will be transported back to the upper reservoir ready for the next energy peak period. The difference in the price of electricity between the high and low consumer demand periods is what drives the economics of pumped storage schemes. However, building on the innovation of this renewable energy hub will be the integration of the KPSHP with a co-located 270 MW solar farm (see below).

In terms of development timelines, feasibility studies were completed Q4 2016 for the KPSHP, with the studies concluding that there were no significant risks posing a threat for the design that could not be mitigated. Construction is expected to commence in Q1 2018, with first generation occurring in Q1 2021.

The Kidston Solar Project Phase Two 270 MW

KSP2 will consist of a 270 MW solar farm co-located with the KSP1 and the KPSHP. This 270 MW project will be the largest solar farm in Australia. Rather than replicating the same schematics as the KSP1, this solar farm will be used to power the pumped storage hydro project during the ‘pumping mode’ (where water is transported back up to the upper reservoir). Integrating these two projects in a ‘hybrid’ scheme will mitigate significant risk in terms of reliance on grid power and volatility associated with energy prices. The integrated scheme will use the energy generated by the 270 MW solar project during the day, when solar generation is at its highest and consumer demand for electricity is at its daytime lowest, to pump the water back up to the upper reservoir. This will result in minimal reliance on regular grid power, increasing the economic viability of the project.

Feasibility studies for this integrated project will be completed during Q1 2017, with construction anticipated to commence Q1 2018 and production to occur Q1 2021.

Opportunities

There is currently a strong movement in Australia towards clean renewable energy production and away from coal and gas generation. This has resulted in a mix of government targets and policies, and the shutting down of numerous coal-fired and gas-fired power stations. The Australian NEM is becoming increasingly unstable, partly due to the intermittent nature of renewable energy production (ie energy can only be produced when the sun is shining and the wind is blowing). This instability is more visibly apparent in South Australia, which has experienced wide scale blackouts as a result of a supply imbalances and network capability. Without immediate remedial action, this pattern will only worsen, with the closing of more baseload power stations across the country and the offshore selling of LNG resulting in a surge in gas prices.

Genex views this as a perfect opportunity for its Queensland renewable energy hub. The construction of the pumped storage hydro project will significantly mitigate volatility in northern and central Queensland, producing energy immediately on demand during those peak periods when the grid is at risk. The Genex project will benefit significantly from increasing price volatility, providing maximum economic return for its shareholders as a result of these recurring patterns.

Challenges

When it comes to energy production, political transitions and changes in policy are a key challenge. However, at present, political views and intentions are in alignment with the intentions of the Kidston projects.

The Queensland State Government has set a strong target of 50 per cent renewable energy production by 2030. As such, they have initiated various policies and funding regimes, including the Solar 150 large-scale solar investment program. Genex was awarded a 20-year revenue contract, ensuring that energy sold is guaranteed above a set floor price for the KSP1. This investment program coincides with the Australian Renewable Energy Agency (ARENA) awarding Genex $8.85 M for the KSP1 as part of its large-scale solar competitive round.

Benefits

The Kidston renewable energy hub is able to benefit significantly from existing onsite infrastructure at the historical Kidston mine site. This has resulted in reduced construction and environmental impact that would otherwise have been associated with this development. The renewable hub is the optimal sustainable and renewable design, with minimal environmental modifications during construction, having insignificant ecological influences during actual energy production and resulting in clean, renewable energy for a significant proportion of the Australian population.

Local community benefits

Through the construction and long-term operation of the solar and hydro projects, the Kidston projects will bring large economic stimulation to the local community, providing opportunity for employment and increasing sales of local goods and service providers. The renewable projects will operate indefinitely, enhancing the community on a permanent basis.

Local environmental benefits

The abandoned gold mine resulted in environmental degradation in the form of harmful waste runoff and chemical leeching from the tailings storage facility. The construction of the KSP1 on the tailings storage facility will mitigate this chemical leeching process, reducing toxic runoff into the surrounding environment.

References

Australian Energy Market Operator (AEMO), 2016. National Electricity Market [online]. Available from: www.aemo.com.au/Electricity/National-Electricity-Market-NEM

Blakers A, 2016. Pumped hydro, solar and wind can deliver a 100% renewable NEM [online].Available from: www.genexpower.com.au/uploads/6/6/1/2/6612684/andrew_blakers_-_anu.pdf

Centre for the Government of Queensland, 2015. Queensland Places: Etheridge Shire [online]. Available from: www.queenslandplaces.com.au/etheridge-shire

Sourceable, 2016. Ex-gold mine to become energy hub [online]. Available from: www.sourceable.net/ex-gold-mine-become-energy-hub

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