Looking to the future: Geothermal Energy and Its Production Challenges

Many countries including Australia count on coal, oil, and natural gas to supply most of their energy needs.

Energy demands in Australia alone are expected to increase by 50 per cent by 2020 and a further estimate of at least $37 billion in energy investments will be required to meet the nation's energy needs.

Diversifying Australia’s energy sources to include low-carbon renewable electricity sources can help to supplement traditional sources in meeting these increasing demands.  

Renewable energy sources include biomass, geothermal and hydro, all of which occur naturally.

While solar and wind power are other renewal sources of energy available in Australia, they are intermittent and only provide energy based on climate conditions.

Geothermal energy on the other hand provides pollution-free electricity by drawing on heat from the depths of the earth.  

The Australian Geothermal Energy Association identifies three different types of geothermal activity which allow for the creation of steam through different methods.

The first are volcanic locations: These are typically volcanically and seismically active zones where water is harnessed from relatively shallow underground reservoirs, typically two kilometres deep and is heated directly from pockets of magma.

The second are Sedimentary Geothermal locations.

These are water reservoirs only a few kilometres deep heated by underground layers of hot rock deposits.

The third are hot rock locations.

Here, water is piped from above ground to dry underground hot rock deposits, perhaps five or more km deep, which are heated by the slow decay of natural radioactive granite – the rock which forms much of the core of the earth.

The process of feeding water underground to dry rock deposits in hot rock locations, referred to as Engineered Geothermal Systems (EGS), makes it possible to harness geothermal energy in previously unobtainable locations.

Once steam is generated, it is captured and channelled to drive turbines, condensed back into hot water and recycled through the system.   Australia hosts both sedimentary rock potential and huge hot rock reserves, but the technology to exploit both of these is not yet economical.

Despite the commercial challenges which exploitation of geothermal energy faces in Australia, around the world the harnessing of geothermal energy is already proving to be an efficient and sustainable supplement to other energy sources. 

National Geographic identifies that geothermal energy is now produced in over 20 countries, with the United States the world’s largest producer.

To put things into perspective, the Australian Government estimates “that one per cent of the geothermal energy shallower than five kilometres and hotter than 150°C could supply Australia’s total energy requirements for 26 000 years”.

In Australia, South Australia and Tasmania’s naturally occurring deeper granite basement rocks offer a viable environment for installing EGS.

Investigation and exploration into the validity of geothermal energy in Australia is well underway, aiming to identify areas of viable extraction and for development of a facility.

A particularly challenging aspect of designing geothermal power plants is securing a viable location for the production wells.

Once a location is chosen and a power plant built, exploration continues to determine geothermal potential in the surrounding areas.  

Narrowing in on Wayang Windu

Whilst the United States is the largest global producer of geothermal energy, Indonesia is following closely behind, and certainly holds the largest share of the world’s potential geothermal resources. Located on the Ring of Fire and home to over one hundred active volcanoes, Indonesia sits atop almost 40 per cent of global geothermal resources.

Forty one volcanoes are found on the island of Java alone, making it abundant with geothermal resources, and holding the highest potential for energy production.

This fittingly reflects the demand for energy: Java is listed as the most densely populated island in the world with 135 million inhabitants, making it home to 60 per cent of Indonesia’s population. To meet this demand, Indonesia has recently been expanding existing geothermal plants to increase output.

The island’s capabilities and demands make it the perfect home for one of Indonesia’s largest geothermal power plants, Wayang Windu.

A Star Energy site, Wayang Windu is a flash steam power plant listed as one of the largest plants in the world, with Units 1 and 2 currently operating at a capacity of 227 MW and plans to build Unit 3 underway.

While the plant continues to boom and the need of geothermal energy is abundantly clear, construction of plants in such a volatile and changing environment requires much planning, consideration and problem solving.

Located in a highly active seismic zone the plant experiences shifts in ground level, both subtle and extreme, on a regular basis.

While the power plant’s buildings and infrastructure are designed to absorb these movements, other necessary components of the plant don’t afford the same flexibility.

Piping systems, which are crucial, pose difficult design problems when taking into account seismic shifts and flexibility.

The challenge: choosing the right pipe joining method

A key component of optimising the efficiency and output of a geothermal power plant is to recycle water throughout the system.

This also reflects the need to avoid using local water supplies which, in the annual six month dry season, can be quite scarce and are vital to the local community. 

Once steam is captured at the production wells, piped to the power plant and harnessed to produce energy, it is cooled and piped back to the injection wells in the form of condensate and brine.

As the distance between the power plant and the injection wells could be several kilometres, it is crucial for the pipeline to meet the challenges associated with a long outdoor piping system.

Additionally, as exploration continues for further expansion into the area, the pipeline must be flexible enough to accommodate future re-routes or extensions.  

At Wayang Windu there are essentially three separate piping systems.

After steam leaves the production wells it is piped as steam or as a two-phase fluid (a mixture of steam and water) to separators which isolate the steam and harness it to generate power, while piping the leftover water, or brine, back to the injection wells.

After the steam passes through the turbines and generates power, it is cooled and piped back to the injection wells in the form of condensate. Separately a pipeline system extends throughout the field to allow the circulation of fluids to lubricate the well drilling activities. 

Primarily condensate, the liquid is pumped around the system where drilling or well repair work is ongoing; hence design flexibility is vital. 

 Altogether almost 30km of outdoor piping was installed.

Outdoor piping of this length in this location poses several risks and challenges during system design and installation. 

Due to rough terrain and an altitude ranging from 1700 to 2200 metres above sea level, the piping systems at Wayang Windu needed to be flexible enough to accommodate the inevitable joint misalignment during assembly, while withstanding any seismic movements once installed.  

As an outdoor piping system, it was also exposed to temperature changes and inclement weather. 

While several options were considered, a galvanised mechanical piping system was chosen to handle the different weather conditions.

Welding, the default pipe joining method, which requires the melting and fusing of pipe ends with a molten filler metal was not appropriate for use in this case. While the process of welding produces a strong and permanent joint, particularly in extreme or critical applications, its limitations include safety concerns, time constraints, increased costs, weather susceptibility during installation, and shortage of skilled and experienced welders, and reduced access to equipment for maintenance.

Welding also produces rigid joints that will not be able to provide the necessary flexibility to accommodate uneven terrain and seismic shifts.

Moreover, welding does not allow for easy maintenance. As exploration continues, the injection wells may have to relocate, so caution is taken to ensure the piping system could account for extensive rerouting. If the injection well moves, the pipes that link the well to the plant must follow. The ability to reroute the piping was a demand that couldn’t be compromised. Welding these pipe sections would have resulted in the need to totally dismantle and re-construct the systems, dramatically increasing cost, time, and creating extensive waste in materials.

On the other hand, the mechanical pipe joining systems are an optimal way to effectively maintain piping systems.

The ease of installation, disassembly, and reinstallation make mechanical pipe joining systems a fast and simple way to frequently access piping systems to perform both routine and unscheduled maintenance.

Compared to alternative pipe joining methods, grooved-end pipe joining installation is simple, fast, and easy.

Consisting only of a housing, a gasket, and bolts and nuts, the installation of a grooved-end system is up to ten times faster than other pipe joining methods and can save up to 45 per cent of man hours.

Requiring only a hand wrench for installation and boltpad-to-boltpad verification for correct installation, machinery transportation, and lengthy joint inspections can be eliminated.

Pipes can also be grooved off-site and shipments can be co-ordinated to further improve jobsite efficiency, reduce downtime, and reduce overall costs

A mechanical pipe joining system has also allowed more flexibility in supply of new piping systems.

Production targets were achieved by simply repositioning some of the previously installed grooved pipes, eliminating unnecessary delays with new pipe deliveries.

This has “saved the day” on several occasions.

During dry season, surrounded by dense jungle, welding could have resulted in hazardous fumes and safety issues similar to those faced by operators in dry Australian conditions, where fire is a serious hazard.

The flame and sparks can create a fire hazard necessitating a fire watch during and following the work.

There is a real risk the fire could destroy property and expose workers to noxious fumes and result in potential burns and eye damages. Ventilation and fume mitigation equipment, personal protective gear and other safety measures are often required for worksites and can add to overall cost and installation time.

During the wet season however, installation schedules would be interrupted by weather. Inclement weather, including thunderstorms and rain, present a host of issues that can wreak havoc with welding projects. Worksites will need to be covered and protected during these weather conditions, and at the same time during cold temperatures, the pipe will often need to be preheated before used. As long as welding as a joining method is used in areas subject to weather change, project schedules will be subject to delays and overruns.

The extreme length of the pipeline and the remote location of the plant presented several challenges for installation.

Welders must cut, bevel and prepare the pipe lengths, align and clamp the joint then undertake two to three passes at each joint.

Furthermore, welding would also require welding machines and materials to be transported along the length of the pipeline as it was installed – an inefficient, expensive, labour-demanding and time-consuming endeavour

To alleviate these extensive and costly problems, the engineer and contractor found a fast, simple, method for pipe joining: Victaulic flexible couplings.

A flexible solution

Chosen to be installed on the condensate, brine and drilling water pipelines, Victaulic flexible couplings allow for deflection caused by seismic shifts and thermal expansion and contraction of the pipeline. 

Unlike welding which causes stress at the joint during these movements and can sometimes lead to leaks, flexible couplings are designed to absorb these stresses, creating a dynamic, self-adjusting pipeline.

Victaulic Style 77 flexible couplings are designed with cross-ribbed construction to provide a strong component for pressurised piping systems.

Independent testing conducted on the grooved system showed it provided exceptional functionality during and after earthquakes, and effective stress relief. These characteristics make it perfect for such a changing environment, and provide superior performance when in close proximity to a source of movement – perfect for Wayang Windu.

The Victaulic solution has been so successful at Wayang Windu that, although initially installed as a short term means to circulate drilling fluids in the early stages in the early 90’s, 15 years on the original pipe and couplings installed 20 years ago are still in operation, and new pipe is being used for ongoing expansions.

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