A Case For a Floating Solar Farm on Townsville’s Ross River Dam

This study on the viability of a Floating Solar Farm on the Ross Dam is a guest post by Elly Hanrahan, an intern for the North Queensland Conservation Council. All views expressed are the author's and not necessarily those of the NQCC.

A Floating Solar Farm In Japan – Photo by Charles Goodell

Townsville is currently experiencing its driest 11-month period since records began in 1841. With no action on water security from any level of government, desperate residents have formed the newly created Facebook group called ‘Water For Townsville Action Group’ in order to come up with a plan to secure Townsville’s water supply into the future.

At the moment, Townsville City Council is pumping 130 mega litres (ML) of water a day from the Burdekin and at a cost of roughly $27,000 per day. Even whilst pumping at full capacity, the dam level continues to drop with Townsville residents using roughly 1,700L per day- more than eight times the average usage of Brisbane residents. Evaporation also plays a large part in the shortage; given the extraordinary size of the shallow dam, Councillor Paul Jacob confirmed to the Townsville Bulletin that we lose between ‘20 and 40 mega litres per day due to evaporation alone’.

It is obvious that prolonged pumping is not a sustainable solution as it is both expensive and inefficient. Many solutions have been proposed such as duplicating the Haughton pipeline from the Burdekin, desalination systems, recycling plants and the proposed construction of the Hell’s Gate dam. One of the more creative solutions put forward on the Water Action Facebook group was a floating solar panel array on the Ross River Dam itself.

Floating Solar Hits Two Birds With One Stone

Floating solar has become popular globally, with several advantages:

  • Reduces water evaporation
  • Doesn’t use land which could otherwise be used for agriculture/development/conservation
  • Can be up to 157% more efficient than land-based solar arrays due to the cooling effect of the water underneath
  • Another source of revenue; simultaneously diversifying the energy mix and localising energy sources.

A floating solar array on the dam would effectively address two key problems faced in Townsville: Water evaporation and the exorbitant cost of pumping from the Burdekin.

As a viability study, I’ve used the figures from the UK’s planned floating solar farm, which will be built on the Queen Elizabeth II reservoir in London in early 2017. I figured if this project is viable in London, which gets 1,460 hours of bright sunshine a year, it would prove even more effective in Townsville, which receives 3,139 hours of bright sunshine per year.

About the UK Floating Solar Farm

Cost: $8.5 million Australian dollars
Size: 57, 960 Square Metres (8 Wembley Stadiums)
No. Of Panels: 23,000
Capacity: 6.3 Megawatts

The cost of pumping water from the Burdekin using fossil fuels is around $27,000 per day ($9.8 million per year), meaning the installation of a floating solar array could pay for itself in a single year. This figure excludes the revenue, which could be made from selling excess energy into the grid when the dam is at a fuller capacity and pumping is not necessary.

According to the Townsville Bulletin, the dam sees 20-40 mega litres of water from the dam evaporate each day. If we use an average of 30 mega litres of evaporation per day and measure the main body of the dam at roughly 25 square km, around 800,000 litres are being evaporated per day, per square kilometre. If the exact same solar farm as the UK Reservoir array were to be built on the Ross Lake, 57, 960 square metres of water would be covered reducing evaporation by close to 100%. This would save an estimated 46,368 thousand litres of water from being evaporated on a hot day.

This is the equivalent of 27 Townsville residents’ daily usage of 1,700L.

Of course, the main benefit of the solar array is the energy that it will generate. The modelling of the UK array estimates an annual energy generation of 5.8 million kWh. This is a figure based on the amount of sunlight hours in London and a similar structure would produce much more renewable energy in Townsville. However the 5.8 million kWh was used as a baseline figure in order to estimate minimum annual revenue.

There is a solar farm starting construction at Clare in Queensland next year. The Power Purchase Agreement (PPA) between Origin Energy and the energy producers, FRV, is $80 per megawatt hour. This includes the price of the electricity as well as the renewable energy certificates.

The expected output of the UK array is estimated at 5800 megawatts. Assuming a similar PPA could be negotiated at $80 per megawatt hour, the annual revenue of the solar farm would be $464,000 per year based on annual levels of sunshine in London.

Finally, jobs

Townsville’s identity has been linked so closely to mining that it seems almost impossible to think of another industry replacing it. However, the price of coal is low, climate change is beginning to have a devastating effect on the reef and our heritage protected areas are under threat from pollution and development. Additionally, our biggest coal importers, India and China, have both began to invest heavily in renewables with the overall goal of substantially reducing independence on fossil fuels.

Townsville has the potential to become a leader in renewable energy technology, employing hundreds of full-time staff whilst resolving its water security issues. Queensland currently employs 4,000 full-time workers in renewable energy and this has the potential to grow with continued investment and strong community support.

The construction of a floating solar farm on the dam would help begin to address many of Townsville’s challenges including water loss, energy security and economic growth. It is recommended that a more in depth viability study be implemented in order to investigate the proposal further.

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  • Elly Hanrahan