On site power a winner

Weekend Australian
18 June 2011, Page: 8

AUSTRALIAN cities could save up to 540 million tonnes of greenhouse gas emissions in the next 20 years if they adopt a plan similar to the City of Sydney trigeneration plant rollout. In the European Union, cogeneration, which includes trigeneration (called polygeneration in the EU) is estimated to have delivered a 15% cut in greenhouse gas emissions between 1990 and 2005.

The Sydney City Council's trigeneration energy plan would create clusters of buildings with low carbon electricity, heating and cooling, slashing greenhouse gas emissions by 40% to 60% by 2030. The council's planned network of trigeneration plants could achieve savings by producing electricity locally, instead of importing it from the grid, of more than $200 million by 2020 and upwards of $1 billion by
2030.

"The City of Sydney is in negotiations with a number of companies to design, finance, build, operate and maintain trigeneration energy systems to supply council buildings, and the first phases of the city wide trigeneration network to supply non-council buildings", council chief development officer, energy and climate change, Allan Jones says. "The council will select a company in coming months and work could start on the project by the end of this year". Australia uses relatively few cogeneration or trigeneration technologies.

The plants accounted for 5% of Australia's total energy production in 2006 compared with 40% in The Netherlands and 55% in Denmark. Cogeneration and trigeneration technologies result in buildings functioning with more energy efficiency and lower tenant energy bills, attract higher quality tenants and ultimately add to the capital value of the property.

Mirvac, Investment Property Group and GPT Group are among the large office tower owners that are adopting the technologies. Investa's general manager for sustainability Craig Roussac says while trigeneration is efficient at generating the energy, there are challenges. "It is difficult to estimate the final energy demands as that largely depends upon your tenants", he says. "In some instances where a building isn't being used to full capacity it makes sense to partner up with someone". This is exactly what Investa did at 40 Mount St, North Sydney.

Investa installed a trigeneration plant at the Coca Cola Place building that supplies lower carbon electricity, hot water and chilled water to the building, and also exports surplus electricity via Ausgrid's electricity distribution network, so the benefits can be shared with another Investa building (Deutsche Bank Place, 126 Phillip St, Sydney). This is a first for a commercial building in Australia and paves the way for precinct based trigeneration systems that can serve multiple buildings.

"It has worked out to the benefit of both parties and it is something we will hopefully see more in the future", Roussac says. Mirvac installed a trigeneration plant in 101 Miller St, North Sydney, jointly owned by Eureka Funds Management, last year and received a five star energy rating.

"When compared [with] an average [25 star] building of the same size, the emissions savings of 101 Miller St is approximately 2300 tonnes CO₂ e per annum. This is the equivalent of removing 640 average cars from the roads for a year", Mirvac Asset Management's sustainable building operations manager Adrian Michaels says. "Trigeneration plants have many benefits, especially as the fuel source is natural gas, which is carbon efficient.

Hospital, hotels and buildings in constant use will benefit from trigeneration plants". Federal government reports have indicated that commercial buildings in Australia account for 19% of energy use and just under 10% of greenhouse gas emissions. Energy Action's head of energy efficiency and sustainability Edward Hanna says there are three key benefits to trigeneration: more energy is used on site, less is wasted, leading to lower CO₂ emissions, and there are long term operating cost savings. "More importantly, trigeneration utilises energy more efficiently than grid delivered electricity", he says.

Energy Action, an independent energy advisory company, says only 28% to 33% of electricity produced in Victoria or NSW from coal is used as energy on site. The rest is lost in generation and transmission. "If you produce energy on site using a gas engine, then straight away up to 44% of the energy utilised by the engine can be used as electricity", he says. "A lot of the energy losses from the gas engine are in the form of heat.

"If you capture the heat via a heat recovery process and use this heat, then up to 87% of the energy utilised by the engine can be used. "So electricity and heat are both utilised, hence cogeneration [or combined heat and power, CHP]. "Once you have recovered heat, then you can direct all or some of that heat through an absorption chiller and produce chilled water for cooling. "So electricity, heat, and now cooling are utilised, hence trigeneration".

Cogeneration and Trigeneration

• Cogeneration uses natural gas powered engines to generate on site electricity.
• The waste heat from the engine is captured to provide heating or for conversion to chilled water for cooling through an absorption chiller.
• When an absorption chiller is used the system is often referred to as trigeneration.
• Using gas as a fuel offers a significant reduction in CO₂ emissions compared with coal fired power generation.