by Lynne Blundell

Cogeneration has the potential to reduce the use of power from coal-fired power stations and thus significantly reduce emissions

Cogeneration plants can generate their own power, they have lower carbon emissions and property developers and building owners want them.

But tell that to the energy agencies who are doing everything they can to hold them back.

A key problem is feeding the energy into the grid.

With cogeneration, and trigeneration, buildings can generate their own power from gas-fired generators, reduce their reliance on the electricity grid and use waste heat tohelp cool and heat a building. Selling power back to the grid makes the whole thing more efficient and viable.

With cogeneration two types of energy, such as electricity and heat, are generated using the same fuel. Trigeneration, or trigen, is where electricity, heating and cooling are generated from a single heat source such as fuel or solar energy.

According to Alan Pears, energy efficiency expert, the current obstacles to integrating with the grid is a major disincentive for building owners.

“If buildings generate more power than they need it is particularly important that they are able to dispose of it. They need to be able to sell it back to the grid or to use it somehow. The current system puts up obstacles to doing this,” says Pears.

Much of this is to do with the way the energy industry is structured and this needs to change, says Pears.

Adrian Michaels, sustainability manager for Mirvac Asset Management, says there are still a number of  issues associated with integrating cogeneration plants.

When upgrading its building at 101 Miller Street North Sydney Mirvac installed a trigeneration plant.

Considerable time and consultation was undertaken with Energy Australia (EA), the grid operator, to agree and finalise the way in which the trigeneration system would interface with the grid.

The option to export power to the grid was considered but was abandoned due to concerns expressed by Energy Australia at the time about potential supply issues.

Instead, Mirvac ended up running its generator separately to the grid and can import power from the network if its generator fails. The project resulted in a reduction in North Sydney peak demand, reducing stress on power supplies in the area.

According to Michaels, the use of trigeneration allows fast greenhouse gas emission reduction using proven technologies. Mirvac is looking at a 10 to 15 year lifespan for its generation plant and sees it as an interim solution to achieve large emissions reductions in a short timeframe.

His advice to companies considering putting in a trigeneration plant is to do detailed modeling of the building load so that the plant can be sized accordingly.

Although unable to sell power back to the grid, Mirvac was able to use excess power from its generator for the Greenway Plaza shopping centre located in the building, but for other building owners this may not be an option.

“Integration issues regarding linking with the power grid are very much still there – hopefully as trigeneration becomes more common this will change,” says Michaels.

Energy regulators make integration impossible

Bruce Precious, GPT’s sustainability manager- office and business parks, says installing cogeneration plants can be a daunting business for building owners as it is relatively new in Australia and there is not a great body of knowledge to draw on.

According to Precious, energy suppliers currently make it virtually impossible to integrate cogeneration plants with the grid.

“It seems unclear what standards have to be actually met by building owners before distribution companies will allow integration. We haven’t been able to get a definitive answer on this,” says Precious.

When GPT tried to integrate a cogeneration plant at 530 Collins Street Melbourne with the energy grid the company found energy authorities less than helpful.

In addition GPT was given poor advice early on in the project about the size of the cogen plant, with recommendations for a far larger plant than was needed.

The recommendations regarding size were too large and it potentially wouldn’t have worked for the project. It is very important to get this right as it is very expensive technology,” says Precious.

Getting the right system required many design combinations and detailed modelling from Dr Paul Bannister from Exergy.

GPT overcame the issues of excess power generation by downsizing its generator plant. Precious believes building owners need to be careful about making buildings into power stations.

“There’s a significant question mark over that strategy,” he says.

Bruce Taper of Kinesis – “It’s important to get the power from cogeneration out of the trophy buildings and onto the streets.”

A better solution may lie in strategies such as the City of Sydney’s Green Transformers strategy which doesn’t rely on buildings operating as mini power stations.

The Green Transformers strategy, put together by energy consultants Kinesis, involves using central plants around the city to convert waste to energy, produce low–carbon energy and recycled water. Through cogeneration, heat is captured as the by-product of energy generation.  This heat is then used for heating, hot water and can even be used to chill water that is then used to cool buildings.

The plan is to install these systems in urban renewal areas as well as being retrofitted in key locations.

The strategy is part of the City of Sydney’s plans to remove its dependence on coal-fired electricity and increase its self sufficiency through low carbon energy and sustainable water supplies.

But, as Bruce Precious points out, the long term drawback of cogeneration is that it still relies on fossil fuels. The building sector and society as a whole should be looking towards drawing 100 per cent of its power from renewable energy.

Because of this, cogeneration is an interim solution – but it is a solution that does allow significant reductions in greenhouse gas emissions right now. And in countries such as the UK, the Netherlands and Denmark it is being used much more extensively than it is in Australia (see our separate story on this)

Precious says the inertia stems from a lack of determination to change things amongst major stakeholders in the current energy system.

“It will take some real political gumption to bring about the change that’s needed,” he says.

And as Bruce Taper, principal of Kinesis, pointed out in a presentation on the Green Transformers strategy, it is important to get the power from cogeneration plants “away from the trophy buildings and get it out to the streets” – in other words to distribute this type of power widely, including to private homes.

Taper cites development sites such as East Darling Harbour, Barangaroo and Green Square as being able to generate 10 to 15 Megwatts of power each.

He also emphasises the need to look further forward, beyond 2030, when it will be necessary to generate a greater percentage of power from renewables.

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