2 May 2012 – Townsville, Adelaide, Sydney and Melbourne all now have emerging examples of low carbon district energy systems, argues Kriston Symons ahead of his presentation on this subject at next week’s ARBS (Airconditioning, Refrigeration and Building Services) exhibition and conference in Melbourne.
The current market situation with the introduction of carbon pricing and a commitment to renewable energy targets is driving decarbonisation of our energy grids. This is definitely a good thing especially in Victoria, which largely uses brown coal to produce electricity.
At the residential level, we tend to think of solar power when we think of cleaner power, and at the commercial building level most of us now have some level of knowledge about cogeneration and trigeneration.
Building wind, solar and other renewable energy generators removes some of the pressure on our coal-fired power stations, and using gas as the fuel from which to generate power – as in cogeneration systems – also decreases the reliance on coal.
Australia and European countries are taking a broader look at ways to implement green energy, and technologies that support a district level approach are surging ahead.
District level energy production is based on a cogeneration, or trigeneration system with absorption chillers to use waste heat and generate cooling – supplemented with additional systems such as thermal storage to meet the electricity, cooling and heating. requirements of the district.
Managing energy at the district level offers a number of benefits. Decarbonising the grid is an obvious one, but less obvious are the benefits it allows in terms of harnessing diversity and demand management.
In a precinct a mix of commercial, industrial and residential buildings have different peak electricity, cooling and heating demands. Commercial buildings draw more during the day and, typically, residential buildings draw more overnight. This means the peak demands occur at different times and reduce the overall size of peak demand from that precinct.
The amount by which peak demand reduces depends on the mix of buildings and their uses, but a typical peak in a district using centralised energy sources is likely to be around 70 per cent of a similar area drawing all power off the grid.
This enables small overall plant to be installed, along with safety factors and margins, which results in less required capacity on the electricity grid.
The concentration of plant and equipment capital and maintenance cost in one location, coupled with the diversity savings of installing overall smaller plant, means that alternative technologies, such as thermal storage and trigeneration are more attractive.
We currently build our power stations to support our peak energy demands – typically those few hot hours of a few hot summer days. In Victoria, nearly 20 per cent of the installed electrical generation capacity is reserved for less than 1 per cent of the time. With our typically increasing demand for power this will require more peaking power stations, unless we can better manage demand closer to the source.
District energy facilitates demand management by offering alternative power sources, switching from electricity to gas network.
District energy systems typically have a large central cogeneration or trigeneration system, but there is also the capacity to implement thermal storage systems to produce heating and cooling from stored heat, reducing the peak electricity requirement of the precinct.
(Although interestingly the March 2012 AEMO electricity statement of opportunities revised electricity demand downward, largely due to a drop in manufacturing production but also due to consumers changing habits in response to high electricity rises and associated energy efficiency programs.)
If we reduce energy demand – through reduced industrial demand, or perhaps through behaviours, energy efficiency and reduced demand in commercial and residential buildings, using smarter systems and better user education – we can defer the need for new power stations.
The longer we can defer the need for new power stations, the longer we have to implement renewable energy systems such as large scale wind and solar installations, and the more likely it is that further advances in energy generation or energy saving technologies will remove the need for new coal-fired power stations at all.
Another key efficiency
Another key efficiency of district level cogeneration and trigeneration systems is the capacity to capture waste heat and use it for heating and cooling.
While difficult to capture at power station level hundreds of kilometres out of the city and piped back to the city, at a district level, this becomes possible. This waste heat can be used for heating applications such as swimming pools or building domestic water and space heating, or cooling applications where the waste heat is processed through absorption chillers.
What’s holding us up?
District energy solutions are proven overseas, with various Scandinavian countries having significant installations. Many are making the next step with supplementing gas fired plant with waste heat from a variety of sources and installing electric heat pumps to match heating and cooling supply with the grid renewable energy conditions.
One difference between many of these European installations and the possibilities in Australia is urban footprint. In Europe there are many district energy projects serving areas populated by about 100,000 people in a compact area, whereas the footprint for 100,000 people in Australia is typically larger, making district energy solutions a little more complex.
Brownfields projects are, obviously, a difficult proposition, and so our first forays into district energy are likely to be for new developments or large urban revitalisation projects.
A range of other issues affect our take up of district energy solutions. One is that there are difficulties in financing large-scale projects, as there are currently no returns on energy fed into the grid.
But with an increasing demand for green buildings, fuelled by rating systems such as NABERS and Green Star, perhaps the demand for energy efficiency will drive energy market changes – making it easier to fund cogeneration and trigeneration systems at the building and district levels, and perhaps offering feed-in tarifs and support mechanisms to change the financial equation.
A current Victorian Economic and Efficiency Commission inquiry is looking into these aspects of distributed energy. The financial equation will also have to change for customers.
Within a district that generates its own power and transmits it through the distribution network, exporters of electricity should be rewarded for avoiding the need to use the transmission network, and customers should not, for example, have to pay transmission charges for their power in this instance.
District energy projects in Australia
While it’s early days, we do have a range of district energy projects underway in Australia:
Townsville CBD’s airconditioning may soon be driven by centralised chilled water storage, under a project implemented under Ergon Energy’s energy conservation and demand management program with funding from government and other sources. Ergon Energy has completed a feasibility study which indicates potential annual savings of 20 per cent in chilling costs and 47 per cent in energy savings, with greenhouse gas reduction of 7000 tonnes. The state government has committed $1.7 million to continue the project.
Ergon Energy has previously implemented large scale chilled water storage projects at James Cook University’s Townsville campus, the town’s Good Shepherd Nursing Home and Queensland Health’s distribution centre at Bohle. The university’s chilled water generation and storage system has been running above expectations for more than two years. It’s currently the largest centralised chiller water generation and storage system in Australia.
In Melbourne, 2011 saw the announcement of a district level cogeneration system as part of a major urban revitalisation initiative in Dandenong in Melbourne’s east.
The project, which will save about 9900 tonnes of carbon emissions a year, starts operating this year. It will reduce the Dandenong CBD’s reliance on the grid, and surplus hot water will be sold to local commercial buildings to provide cooling (using building owner-supplied absorption chillers).
In 2011 the City of Manningham put out a tender to complete a feasibility study on district energy solutions for the local council in Melbourne’s east.
Another high profile Australian project is the City of Sydney, aiming to produce 100 per cent of its energy needs locally by 2030. Seventy per cent will come from trigeneration, with the remainder from renewable energy.
The City of Adelaide is also picking up the pace (unsurprisingly, given that South Australia leads the way in Australia’s renewable energy production), having recently investigated a couple of precincts for their suitability for district energy.
Making energy production more visual in our precincts will also create an awareness that leads to greater energy efficiency. With a commitment to renewable energy targets and the resultant decarbonising of the electricity grid is this the end of the start of district energy in Australia? I’d like to think not.
With the technologies now available, successful overseas projects leading the way, local expertise in design, implementation and operation, renewable energy and district energy, with all its benefits, have a future together.
Kriston Symons is technical director of AECOM and has worked on several overseas district cooling plants and on central energy systems in Australia.
He will co-present a seminar with colleague Jack Kerlin, “Decarbonising the Grid – The End of the Start of District Energy” at ARBS. The exhibition and conference is at Melbourne’s Convention Centre from 7-9 May. Details