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Melbourne Water finds an energy-saving solution

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04 Jun, 2024

This post was originally published on Sustainability Matters

Sewage and wastewater treatment is a highly energy-intensive process, presenting a challenge for water utilities seeking to meet net zero goals.

Melbourne Water’s Eastern Treatment Plant (ETP) treats almost half of all Melbourne’s sewage, an average of 330 million litres a day. Located in the Melbourne suburb of Bangholme, approximately 19 miles south-east of the city centre, the 1000 ha site was upgraded in 2012 to treat sewage to an advanced tertiary standard, producing Class A recycled water.

Shooting for net zero

Since opening in 1975, the ETP has always generated energy from sewage gas, and the site houses seven power generators that are capable of running solely on biogas — produced through the anaerobic digestion of sludge during the first and second phases of water treatment.

In 2020, Melbourne Water began a project with John Holland-KBR Joint Venture to upgrade the biogas handling system at the Eastern Treatment Plant to make it more efficient, resilient and futureproof. The project aimed to expand capacity, prevent corrosion and sedimentation, and extend the working life of equipment — with specific requirements to remove liquid droplets and moisture and to minimise the size and cost of any necessary cooling system.

Sewage transfer and treatment are responsible for about 85% of Melbourne Water’s total greenhouse gas (GHG) emissions, so contributing to the company’s net zero commitment was a main target for the project. “However, with existing assets nearing the end of their service life, ensuring that the new asset can service future production growth and plant upgrades was also essential,” said Nick Fung, Senior Project Manager at Melbourne Water.

Increasing reliability for the operations team onsite and improving safety across both operation and maintenance were further aims.

Selecting an energy-saving solution

The HRS BDS formed part of a wider upgrade to the biogas handling equipment at Melbourne Water’s Eastern Treatment Plant.

Biogas contains hydrogen sulfide (H2S) gas, which condensates out to form a highly corrosive liquid. Including a system to remove most of the moisture from the gas was therefore essential to minimise the amount of corrosion and degradation of the power station generators, while also limiting operational downtime and reducing the need to import electricity from the grid.

HRS Heat Exchangers was one of five companies invited to tender for the moisture removal equipment in the project. The HRS Biogas Dehumidification System (BDS) removes water from biogas, protecting combined heat and power (CHP) engines and generator sets from corrosion and cavitation. According to HRS, it condenses more than 90% of the water present in biogas by reducing the temperature to leave a clean gas. The addition of heat regeneration technology means the cold biogas produced can be used to pre-cool the incoming warmer biogas. This reduces the load on the final cooling heat exchanger and saves valuable energy.

The BDS supplied for the project has a maximum capacity of 4161 m3/h (4710 kg/h), while the inclusion of an energy recovery section subsequently reduces the eventual chiller load by 30%. This BDS consists of two heat exchangers, a regeneration unit and a final cooler, supplied on two skids. One skid — located in a hazardous area zone — contains the heat exchangers, a condensate knockout pot, a condensate drain line and all the relevant IECEx-rated instrumentation. The second skid contains a buffer tank, standby and duty glycol pumps, and all the relevant glycol line process control valves and instruments.

HRS also supplied an additional chiller and detailed process control descriptions, enabling the joint venture engineers to provide overall control and automation systems for the client.

Overcoming complex design parameters

The HRS BDS at Melbourne Water’s Eastern Treatment Plant incorporated some complex design elements.

The BDS needed to meet the requirements of two different operational stages, each of which contains four duty requirements. This meant a complex thermal design process was necessary to make sure that the supplied unit could meet all eight of the potential design scenarios.

Ella Taghavi, Project Manager and Technical Lead at HRS Heat Exchangers, explained: “Designing the BDS for the Melbourne Water project posed a significant challenge as it needed to cater to both current and future demands, with two very different conditions in each phase.

“The current first phase uses biogas supplied by the compressors and aftercoolers at an average pressure of 66 kPa. In the second (future) scenario, the gas is supplied following a number of additional treatments at an average pressure of 5 kPa and then supplied to the compressors. We therefore had to deal with two very different inlet conditions.

“The addition of heat regeneration added further complexity in terms of design. However, thanks to our cutting-edge technology, not only were capital costs reduced as a smaller chiller could be specified, but regeneration is also helping to lower ongoing operational costs.”

An efficient result

From being awarded the contract in July 2021, it took less than 12 months for HRS to install the bespoke BDS onsite, with commissioning completed in June 2022.

The John Holland-KBR team noted that of the five tendered solutions, the technology of the HRS BDS stood out, including the excellent technical support it provided to help develop the project further with Melbourne Water.

“Our experience in project management, construction and logistics enabled us to overcome early design challenges and respond to necessary changes during the design and construction process. As a result, we were able to deliver a high-quality product that has performed to specification since its installation,” Taghavi said.

The upgrade project has improved the quality of the biogas supply to the power station at ETP, providing more confidence in its ability to deliver more than 36,000 MWh (approximately 130 TJ) of thermal energy for process heating. This means a reduced reliance on natural gas, cutting down on emissions and making the operation more self-sufficient.

Top image caption: The HRS Biogas Dehumidification System (BDS) is specifically designed to improve the operating life and energy efficiency of biogas engines. Images courtesy of HRS Heat Exchangers.

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Energy Efficiency as an Imperative Climate Strategy

Energy Efficiency as an Imperative Climate Strategy

02 Feb, 2025

With mandatory climate statement disclosure rolling out in Australia, businesses need to start reporting on their emissions and sustainability plans for the future. As companies begin assessing the relevant risks and opportunities related to various climate scenarios, energy efficiency presents itself as an immediate climate-strategy with long-term benefits.

Commencing 1 January 2025, businesses that meet two of the three conditions — more than 500 employees, gross assets above $1 billion or $500 million or more in consolidated gross revenue — are required to lodge a climate statement, which discloses their climate-related plans, financial risks and obligations. As part of the gradual roll-out, by 1 July 2027, businesses that meet two of these conditions — more than 100 employees, gross assets above $25 million or exceeding $50 million in consolidated gross revenue — will also be required to report.

This climate statement will need to include the company’s sustainability governance, climate risks and opportunities, including those physical and transition related. They will also need to disclose their Scope 1 and 2 emissions, strategy to decarbonise, and conduct scenario analysis on the short, medium and long term impacts on the business. By the second year of reporting, businesses will also be expected to report on Scope 3 emissions.

Scenario analysis will be based on various assumptions of the state of the climate, one of which includes a possible future where global temperature has increased 2.5°C or more. They will be required to share their climate strategy and steps they are taking long-term in preparation for this scenario.

Common themes within climate strategies will include switching to renewable energy sources, electrifying fleet vehicles, purchasing carbon credits, and carbon capture and storage. Many of these methods look at reducing emissions through the energy source, or targeting the carbon aspect directly; however, climate strategies can also include reducing the amount of energy used. By investing in more energy efficient equipment, sites can maintain production whilst using less energy and producing less emissions.

When increasing energy efficiency and reducing energy consumption first, businesses will see short-term impacts; however, in the long term, they are also improving their foundation for an energy transition. Assuming no other changes, higher energy efficiency can lead to decreased energy demand, allowing for reduced system requirements when specifying and planning for self-generation or energy costs.

To understand what opportunities are available for upgrading to more energy efficient equipment, businesses can start with an energy audit to understand how energy is being consumed across site. Energy audits, like the ABB Energy Appraisal, can provide a roadmap for where and how equipment can be upgraded for the best energy saving potential. An energy audit identifies areas that can be immediately improved with existing equipment on the market, so there is no need to wait for the commercialization or development of more sustainable technology. Going beyond just changing all lights to LEDs, efficiency recommendations may include areas where variable speed drives can be added to control motor speed or upgrading from an IE3 motor to an IE5 ultra-premium efficiency or IE6 hyper-premium efficiency motor to reduce energy losses by 40% or more. This area can often be overlooked on sites as the Minimum Energy Performance Standard (MEPS) in Australia for motors is just IE2.

Mostly used in pumps, compressors, conveyors and fans, motors may seem like a minor part of a site; however, with 45% of the world’s electricity converted into motion by industrial electric motors, there are many opportunities for energy savings. In fact, a recent survey commissioned by ABB IEC Low voltage motors, showed that 92% of surveyed businesses in Australia recognize the important role of electric motors in achieving sustainability targets. In this same survey, participants ranked a reduction in operating cost as a more important driver for investing in energy efficiency than lowering their organization’s emissions. This is because upgrading to newer, more efficient equipment provides benefits beyond just emission reduction. For example, ABB’s Synchronous Reluctance (SynRM) Motors, available in IE5 ultra-premium efficiency or IE6 hyper-premium efficiency, use no rare earth metals or magnets. Running quieter and with bearing temperatures reduced by up to 15°C and winding temperatures by up to 30°, SynRM motors have longer maintenance periods, superior reliability, and contribute to a better operational environment.

Looking ahead, upgrading to an IE5 SynRM motor also provides more visibility into Scope 3 emissions, as SynRM motors meet ABB’s circularity criteria and transparency on environmental impact is provided through Environmental Product Declarations (EPDs).

By requiring companies to disclose their climate information, these new legal requirements are opening the door and facilitating more internal discussions on environmental impact and emission reduction. Whilst mandatory climate reporting is only required of large business entities this year, the progressive roll-out and Scope 3 emission reporting requirements mean that businesses of all sizes in Australia will be impacted by these new requirements. As businesses become more conscious of how sustainability should be integrated into their operations and finances, there is no better time to start investing in energy efficient solutions.

For more information, click here.

Image credit: iStock.com/denizunlusu

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