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SUSTAINABLE ENERGY


of water are stored on site to feed hydrants and sprinklers. This is mandatory as water supply can be scarce throughout the year. We undertook to insulate the tank and to provide additional connections to allow the water to be pumped through our water circuits. The design had to ensure that no water was lost from the tanks. Of course this meant that we had to store chilled water since using hot water to fight a fire would have unfortunate consequences.


Chilled water storage tanks.


that the solar conditions on the site were such that the annual equivalent of 1,400 tonnes of CO2


were saved. The original concept for this field had


recommended the use of micro-concentrator type (MCT) panels as these had a greater efficiency. However at the time such panels were not eligible for funding. Fortunately, a number of events aligned


perfectly. Firstly, the redevelopment project was funded, the Australian Solar Institute announced funding for solar-cooling schemes and Echuca Regional Health was given the opportunity to work with Chromasun to develop the first micro-concentrator tube panel installation in Australia. It was clear, however, that we could not


simply add this requirement as solar chilled water. While it is true that profiles of the building cooling load and the availability of solar energy are similar, there is a time shift arising from the efficiency of the façade. It was also apparent that the number of panels required to meet the peak cooling demand would not meet the economic parameters of the funding, neither could they be accommodated on the building. In order to maximise the running hours of each panel complex environmental modelling was undertaken and from that it was determined that we would install sufficient panels to generate 75% of the peak chilled water demand and for thermal storage to cover the load peak. Micro-concentrators work by tracking the path of the sun throughout the day and reflecting the energy, via mirrors, onto a copper tube. Each panel contains multiple mirrors and a copper u-tube through which water is run. These panels generate hot water at much higher temperatures than an evacuated tube, selected for this project at 170˚C, so it is possible to use double-effect absorption chillers with an increase in coefficient of performance (COP) to about 1.2. With each panel producing 2.1 KW hot water of energy. The Echuca hospital development required 300 panels, arranged in blocks of five, for ease of control, located across the northern roof-scape. The hospital is fortunate that it


experiences many clear sky days throughout IFHE DIGEST 2014


the year. The MCT solar installation does not meet the peak cooling demand and there will be days where it does not produce enough hot water. Again, it was necessary to support the requirement for no increases to the electrical infrastructure and to avoid the cost increases associated with exceeding the maximum demand for the site. The response was made in two parts:


• Design the chiller to be dual fuel with the heat exchanges arranged in series.


• Provide thermal storage to meet the peak demand. This was an interesting


Thus, the first exchange utilises the solar field hot water while the second uses natural gas. The charge for natural gas is much lower than the daytime tariff of electricity and does not give rise to maximum demand penalties. The absorption chiller was placed as a side stream unit within a network of high efficiency electric chillers. This approach maximises the potential of the solar field to contribute to the chilled water requirement and for the user to choose how to generate the remaining requirement.


proposition as funding for the hospital did not include for such an approach and any monies spent in this direction would require savings to be made elsewhere. Such is the cost of providing storage that it was not immediately clear how this could be achieved. However, what was funded was the provision of water storage for fire fighting purposes. 340,000 litres


‘A number of key systems emerged that would draw together clinical, management and built environment systems to provide an integrated experience.’


The tanks have been arranged to act as a hot tank and a cold tank, with water drawn from the cold tank, being replaced with, initially cold, water from the hot tank and then returned from the circuit to the hot tank. This approach alleviates the problems of mixing and ensures that the maximum cooling capacity of the storage is obtained. Each tank is charged by an electric chiller utilising lower night time tariffs or from the absorption chiller when the solar heat source is greater than the building chilled water demand. There were two design challenges which


needed to be overcome. The first was chemical treatment. Given that the stored water would in the event of a fire be hosed onto fires any chemical added to the water had to be shown to have no effects detrimental to the health of the public or of the fire-fighters. This was resolved in consultation with the Victoria Country Fire Authority and has been carefully recorded so that no other chemical is substituted for that approved.


The second was the structural integrity of


tank. Fire tanks are constructed of sheet steel with a liner. The introduction of insulation was readily achieved except for the roof. Fire tanks roofs have no structural component, they are simply a lid. Adding insulation would have required an extensive support structure. This resulted in the problem of insulating the top of the tank. There was one other matter to resolve – mixing. Clearly it is not advantageous for warmed water returning to the tank to mix with the stored water. Ideally the warmer water should stratify on top of the cold water. It occurred to me that if spheres are


floated on the surface of the chilled water they would pack together. A model was constructed, floating polystyrene spheres and interlocking the rows, forming two layers. The models showed that this approach provided sufficient insulation and acted as a diffusion plate. In total 12,000 Ø150 mm polystyrene spheres have been joined together to form ‘lily pads’ across the surface of the tanks.


Flexible ventilation systems Variable air volume (VAV) is a common approach within Australian healthcare facilities. Generally, a VAV box will supply conditioned air to two or three bedrooms. Air from the room is exhausted via the corridor and collected at a convenient point, generally above the staff base. Up to 50% of


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