11 April 2012 – In 1973 Denmark’s dependence on imported energy hit an energy shortage crisis and among the responses was a driving ban on Sundays.

The experience galvanised determination to be more self sufficient and energy efficient. Today the town of Aalborg (pictured)  is one of many municipalities connected to a zero carbon heating grid that works like a dream, and is an example as to what can be achieved in Australia.

Aalborg is a town of 110,000 population in the north east of Denmark. Forty years ago, Aalborg commenced the refurbishment of its district heating network. Today, 98.2 per cent of the community is  connected to and daily use the municipality owned system.

Heating is supplied to properties via a closed loop of flow and return pipes of 80-90 degree hot water. The water comes in hot, heats the property, and leaves 10-20 degrees cooler, back to heating sources where it is brought back up to 80-90 degrees. A continuous cycle transfers heating from heating sources to properties.

Heat is drawn from a variety of sources into the district heating system. Waste heat from local gas fired electricity generation provides over 65 per cent of the heat needed. A municipal waste to energy plant and two cement factories provides another 15 per cent each using their waste heat. The rest is provided from a variety of smaller sources, remarkably, including the local crematorium.

All of these sources are utilising heat that would otherwise be wasted into the air via exhausts and flues. So they do not require any fuel (such as gas or coal) and do not expect to see any more greenhouse gas emissions being produced.  It also reduces the urban heat island effect caused (partly) by heat being pumped into the air.

Jonathan Prendergast

Three gas fired heating plants are included around the network to provide heat when the above sources do not meet demand, but the district heating system has become so efficient at balancing loads, that the gas fired boilers are only needed for 1 per cent of the heating supply each year.

The 1416 kilometres of insulated underground pipework is owned by the Aalborg District Heating Company. This company is 100 per cent  owned by the local municipality, but is not for profit, and no money is transacted between the district heating company and the municipality. All savings achieved through the system are returned to the community by reduced energy bills. Expansion of the network is decided by a business case each time.

Heating is supplied to hotels, commercial offices, apartments, detached dwellings and other premises. For a local resident, there is a connection charge of approximately $600. A connecting resident can expect a payback period of two years, based on reduced heating bills, compared to gas heating.

District energy in Denmark

District energy includes district heating, district cooling, precinct trigeneration, distributed generation and embedded generation. It generally involves:

  • Distribution of thermal energy by insulated pipework from sources to properties.
  • Local electricity generation, and capturing of waste heat
  • Input of thermal (heating and cooling) from more than 1 source, like the Aalborg example above.

District energy is a holistic city-wide energy efficiency measure.

Energy efficiency in Denmark was primarily driven by lack of energy security, with, at one stage, more than  90 per cent of energy imported from its neighbours. This led to an energy crisis in 1973, to the extent that driving was banned on Sundays to preserve energy.

Today, there are over 400 municipality–owned district energy networks in Denmark. Rethinking its  energy sources has led Denmark to become a world leader in energy efficiency and also, now, renewable energy. Even in a short time spent travelling in Denmark, one will see wind turbine propellers being transported on highways to be installed around the country.

The expansion of the district energy industry in Denmark has seen significant innovation in technologies. This includes simplified housing connection systems, and pre-insulated underground pipe systems that allow straight runs of pipework, despite expansion stresses, and simplified installation, saving time and money on site during installation.

What does this mean for Australia?

Energy efficiency, district energy and precinct trigeneration have the potential to stimulate job creation and business investment while also reducing greenhouse gas emissions and energy costs to the community. A win-win-win-win. It’s hard to think of any other technology or industry that can provide such broad benefits to our economy and community.

Australia has a more temperate climate and doesn’t have such a high need for heating as Denmark. Australia has a large cooling demand, and the current major challenge in Australia is providing infrastructure efficiently to meet peak loads during hot summer days when everyone turns their airconditioners on at once. Upgrading infrastructure to meet this peak demand is currently seeing electricity prices drastically increase.

This is where trigeneration comes into its own in Australia. Not only is it a highly efficient method to provide electricity, heating and cooling, but it may well be a key part of the solution for peak demand management in our power hungry cities.

If the Stockholm district cooling system now includes over 150 kilometres of pipework, then one can only imagine the potential in Australia’s cities.

There is currently a wave of interest in (cogeneration and) trigeneration for the low GHG emission supply of electricity, heating and cooling for buildings in Australia. If all value is captured in the project, trigeneration is proving to be a cost competitive way of managing building energy needs.

Places Victoria’s (formerly VicUrban) Dandenong project and the City of Sydney’s trigeneration project, amongst others, are two of the most high profile that are leading the way, particularly in terms of considering a precinct or district approach. Many more projects around Australia are at various stages of planning and commercialisation.

When one can see what has been achieved in a small town like Aalborg and the advances being made across Europe, Asia and America, it is clear that district energy is not just about immediate GHG emissions due to the use of less carbon intensive gas rather than coal.

The establishment of heating and cooling networks, and capturing of a wide variety of waste thermal energy can lead to further long term GHG emissions reductions, energy efficiency and economic growth.

District energy and precinct trigeneration has a large medium to long term potential in Australia in providing many economic and community benefits and moving towards a low carbon economy.

Jonathan Prendergast is the director of Prendergast Projects, which provides technical and commercial advisory services on precinct trigeneration and energy efficiency projects. See website