by Steve Hodgson
Imagine a major global city planning to cut its (mainly coal-fired) carbon emissions by 70% by 2030, through the development of a co-ordinated, decentralized network of gas and refuse-fuelled trigeneration schemes. That city is Sydney, Australia, which has just adopted a Trigeneration Master Plan to add flesh to the bones of its 2008 Sustainable Sydney 2030 – the Vision report.
The original vision set out a path for reaching the carbon reduction target through the use of a wide range of measures – improving energy efficiency, encouraging people to cycle and walk, utilizing waste as a resource, converting non-recyclable waste to energy, recycling water, renewable energy and – crucially – a decentralized energy network, powered by a series of trigeneration schemes.
Central to Sydney’s vision are what it calls ‘green transformers’ – the co-location of trigeneration plants with waste collection/treatment and recycled water treatment plants to make low-carbon precincts. These transformers expected to deliver the greatest reduction in greenhouse gas emissions.
So far, so ambitious. The city aims to replace electricity supplied to city buildings from remote, coal-fired, electricity-only power stations; with power from local, smaller-scale, gas engine-based trigeneration plants that will also feed hot and, using absorption chilling equipment, chilled water around local thermal energy networks. Buildings in Sydney need cooling as well as heating – hence trigeneration as opposed to cogeneration. Aside from system efficiency gains, the new infrastructure will also eliminate the losses caused by transmitting coal-fired electricity into the city from remote generating plants.
Some 350 MWe of new trigen schemes will eventually be needed to deliver the planned carbon reductions. Individual schemes are likely to be based on gas engines, will each be less than 30 MWe in size, and will be developed by a variety of energy services agreements. The first of these low-carbon precinct agreements was signed in March this year for plant to serve buildings being developed in the Broadway area of the city. Sydney acknowledges that four-fifths of the buildings to be present in the City in 2030 are already built, so the local energy schemes will have to connect existing, as well as new buildings.
There’s still a long way to go in Sydney, but the city is benefitting from experience gained in London by its Chief Development Officer for Energy & Climate Change, Allan Jones, who previously did this type of work for the London Climate Change Agency, in pre-recession days. The UK capital continues to work towards a target of a quarter of its energy to be supplied from decentralized sources by 2025. A London Heat Map has been drawn-up to highlight the best opportunities for new cogeneration (less need for cooling in London) schemes.
In both cities, the involvement of private sector funding is, of course, crucial. Costs for establishing new district energy infrastructure – mainly underground hot and chilled water pipelines – can be very high indeed. The standard practice is for local government to commit its own buildings to provide baseloads for new district energy schemes; simultaneously persuading private sector operators to do the same.
So will Sydney realise its ambitions for new decentralized energy schemes? There’s no doubting the scale of the ambition shown in the plans. The city seems to have many of the ingredients for success – a bold, ambitious plan, solid support from local government, and the interest of the private sector.
The case for cogeneration and trigeneration is, of course, well-understood by readers of COSPP. In many cases, the efficiency gains from replacing old, inefficient, remote and electricity-only power generation with modern, highly efficient, modular and local technology are high indeed. Whether high enough to attract sufficient investment to fund initial capital costs – the City of Sydney is currently finding out.