Near Perth in Western Australia, a major new suburban area called Alkimos is being planned. The area is to house around 50,000 people over the next 20-30 years and the aim of the developer is to make the new community carbon neutral.
Green Rock Energy Ltd. is the owner of the geothermal rights in the area. The availability of a geothermal heat source has led Green Rock Energy to propose the use of geothermal energy in a district heating network for cooling and heating purposes in the new suburb. Ramboll was commissioned by Green Rock Energy to explore the possibilities of a district heating and cooling network in the new suburb.
As an initial screening, Ramboll developed a concept for this district heating and cooling network and made a first price estimate for establishing the network. Furthermore, Ramboll provided Green Rock Energy with an understanding of the capital costs as well as the operational costs involved in a district heating and cooling network and the installations required in the connected buildings.
Main results of the screening
Ramboll outlined how cooling could be supplied through the network by means of local absorption chillers. It was proposed that each housing cell include a number of decentralised energy centres with absorption chillers converting the provided heat to cooling. From the local energy centres, a local distribution network of heat and cooling should provide heating and cooling to the dwellings.
As district heating and cooling are still relatively new concepts in Australia, Ramboll could benefit from our wide experience within this area in other parts of the world. The specific climatic conditions were analysed, and it was assumed that the demand could be divided equally between space heating demand and cooling demand.
To determine the annual demand, the peak load was diversified to account for the level of simultaneous use. The total annual demand for space heating, cooling and DHW was therefore estimated to around 100,000 MWh and the total peak load estimated to around 30 MW.
New-built homes in Western Australia must at least meet the energy requirements for a 5-star energy rating according to the Nationwide House Energy Rating Scheme. However, as the new buildings of the Alkimos Community are going to be built over a 30-year period from 2011 to 2041 it was assumed buildings are built according to a 6-star rating.
The pipe network
The main distribution network was proposed to consist of two pipes – a supply and return pipe with heat. The local distribution network should comprise four pipes: Two pipes providing heat (supply and return) and two pipes providing cooling (supply and return).
The necessary pipe dimensions were estimated and the optimum diameters of the pipes were calculated based on knowledge about temperature differences between flow and return, pressure levels, costs for piping and the maximum velocity in the pipes.
The report also outlined some key general considerations to be made when considering DHC based on Ramboll’s experience of best practise.