Heat recovery, heat pumps, thermal storage and 390 kW of solar PV is keeping energy use and costs down.
The Doone Kennedy Hobart Aquatic Centre (DKHAC) uses different energy sources to maintain a consistent and stable temperature for the pool, heating and domestic hot water systems.
Current heating system
A unique feature of the DKHAC is the heat source for the heating system that provides heating for the pool systems, space heating and domestic hot water. The existing heating system utilises treated effluent water transferred from the Selfs Point Sewage Treatment Plant to the Blinking Billy Point outfall as the energy source for the water sourced heat pumps. This arrangement allows thermal heat transfer from the treated effluent water to the heating source water.
The heated water is then transferred to a 300,000 litre thermal storage tank. This thermal storage tank acts like a water battery in times of peak water demand, storing heated water for use by the water circuits contributing heat to the pools, space heating and domestic hot water system.
An electric boiler is provided as a backup to the treated effluent/heat pump heating system.
Current DKHAC Photovoltaic (PV) Solar System
The first stage of the photovoltaic (PV) solar cell panel system was completed in December 2015, totalling 400 panels producing 100 kW. The second stage was completed in June 2017, totalling 1,041 panels producing 290 kW. The predicted annual solar power generation of this system is 370,000 kWh.
As of February 2018, this system has produced approximately 100,000 kWh of solar power.
The solar power is distributed throughout the centre via the electrical distribution boards and is 100% used onsite. This results in an annual cost saving of approximately $130,000 (or 12.5% or our energy use), with the ‘payback’ expected to be less than six years.
At the time of completion, it was the largest roof mounted solar panel installation in Tasmania.
New supplementary heating system
In practical terms, if the existing heat pumps fail for any reason, the useful 'battery life' of the thermal storage tanks is only a few hours (depending on heat loads at that time). The thermal storage tanks are also highly inefficient and lose heat through the concrete walls and floor and also through atmospheric vents.
Eight gas boilers have been installed at DKHAC in two modules to supplement the three heat pumps that comprise the heated water generation loop within the plant room. This has resulted in the decommissioning of the thermal storage tanks and provided a more stable heating system for the Aquatic Centre. In line with this upgrade the City of Hobart has replaced 18 motors and variable speed drives in the facility during 2021 and 2022 resulting in an energy saving of 292 MWh and 87 tonne reduction in carbon emissions per annum through reduced electricity consumption. The gas system is called on to supplement the heat pumps on a very infrequent basis in full system operation.
Future energy mix
Having the option to use any combination of effluent, solar, electric and gas energy, the DKHAC can ensure a stable and reliable energy source to maintain the plant room heating systems, using two sources of renewable energy 24 hours a day, 7 days a week, 365 days a year. This also means the centre can implement demand management to make the best use of the energy sources available to reduce energy cost and lessen the demand on critical infrastructure during peak demand periods.
Through the City's design and engineering, energy use at the centre has been reduced by approximately 20% since 2010. The improvements discussed above will result in further energy savings in the future.
View the original case study from the City of Hobart.
View a video tour of the facility and its energy systems: