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Christ Church Grammar School
Rockwater was principal hydrogeological consultant to the Christ Church Grammar School geothermal heating project: an innovative project utilising geothermal bore water in a heat exchange unit to heat the school swimming pool. Economic feasibility studies showed that despite higher initial capital costs, the use of geothermal groundwater has lower annual energy and maintenance costs, and over a life cycle of 25 years is about 15% cheaper than conventional (fossil-fuel) heating options. It has the environmental advantages of causing no net loss of groundwater, since the water is reinjected into the aquifer once the heat has been extracted, and saving about 5,000 tonnes of greenhouse gas emission over a 25 year life. Following a feasibility study to determine whether geothermal groundwater was accessible at the site, bore construction designs were compiled and tendered to appropriate drilling contractors. Rockwater supervised all drilling and construction for the deep production and injection bores and provided the down-hole geophysical and temperature logging services which identified the appropriate aquifer intervals for extraction and reinjection. The system has now been operating successfully for two years, with geothermal groundwater (41.6oC) from the Yarragadee aquifer pumped from a 738 m deep production bore, and returned into a higher level of the Yarragadee aquifer, hydraulically separated from the lower level, via a 609 m deep injection bore. The project has won both government and industry recognition for its environmental sustainability and engineering excellence.
Edith Cowan University - Hydrothermal Air Conditioning Project
Edith Cowan University pumps groundwater from two production bores which feed heat exchangers used to provide thermal energy for an air-conditioning system at its Joondalup Campus. After the water has passed through the heat exchangers, it is pumped back into the aquifer via two injected bores.
Rockwater conducted a review of the injection system, including sampling of the injection water for chemical analysis and an assessment of the options that could be used prevent subsequent clogging of the screens. A sealed system, minimising the possibility for air-entrainment and the oxidation of dissolved iron, and new pipes able to withstand the attendant high collapse pressures, were proposed. An improved design for the replacement injection bores, including the use of longer screens with a larger diameter and aperture size than previously used, was also recommended.
Prior to drilling of the new injection bores, one of the existing production bores was test-pumped in order to determine its sustainable yield, provide aquifer parameters for groundwater modelling, and assess the radius of influence of pumping and therefore assist in siting of the new injection bores.
Two new injection bores was constructed and equipped. Thereafter, a number of pumping tests were performed to assess the capacity of the new injection bores operating individually and then together as an operational configuration.
St. Hilda’s Anglican School for Girls - Geothermal Water Supply Project
St. Hilda’s existing 25 m swimming pool is to be decommissioned and a new 50 m pool constructed on the property. As part of the re-development plan the School is investigating the feasibility of obtaining a suitable geothermal water supply to provide pool heating and possibly heating for a 150-bed boarding house.
If a geothermal water supply can be obtained, the intention is to pump warm groundwater from a deep production bore in the Yarragadee aquifer, pass the water through heat exchange units to warm the pool and accommodation unit, and then to inject the cooled water back into a shallower section of the aquifer. This would result in no net loss of water from the aquifer and provide a source of heating with negligible carbon-dioxide emissions.
Rockwater was retained to provide background hydrogeological data on the hydrogeology, and the feasibility and means to obtain the required geothermal water supply.
Town of Claremont Aquatic Centre
Following the success of the Christchurch geothermal heating project, other swimming centres have been keen to implement similar systems. The Town of Claremont Aquatic centre was one of the first to engage Rockwater to conduct a feasibility study to determine site suitability. The feasibility study showed geothermal water should be available in the Yarragadee aquifer and the council resolved to install a geothermal-based heating system as part of its upgrade. Rockwater was subsequently awarded the contract for hydrogeological services including bore design, preparation of tenders, management of the production and injection bore construction, and reporting to the Department of Environment. A production bore was successfully installed to 845 m depth and yields water supplies of 43.2oC to the heat exchanger. The cooled water is then returned to the aquifer via a 605 m deep injection bore resulting in no net loss of groundwater from the system; recirculation is of cool water to the deep bore is prevented by separation from the lower aquifer by impermeable shale layers. The Sustainable Energy Development Office, of the Government of Western Australia reported "The local council have been more than pleased with their choice, with operating costs totalling just $2,500 for the first half of 2004. Being more energy efficient, the geothermal system also results in lower greenhouse gas emissions. It is estimated that the system will save 8,300 tonnes of greenhouse gas emissions over a 25-year period." |
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