Project Description

The new cooling system includes a Broad 500kW cool absorption chiller that is supplied with hot water (95°C) to produce chilled water at 6°C. An absorption chiller uses an evaporation cycle to cool water that is then circulated though an air conditioning system to cool the ducted air supply. The heat used to drive the evaporation process comes from the water heated by solar collector tubes and natural gas. There is a large array of over 1600 evacuated tubes mounted on the roof of the hospital’s engineering and maintenance building.

The installation includes extensive monitoring and control technology to optimise the use of solar energy and maximize cost savings.

Background

Echuca is situated on the Murray River in northern Victoria – an excellent location to capture solar radiation. Echuca Regional Health manages the Echuca Hospital and in 2010 decided to look at a range of options to replace existing electric air conditioning chillers that had reached the end of their useful service life.

The hospital looked at technologies that would both reduce energy costs and save greenhouse gas emissions and chose a heat driven absorption chiller utilising hot water heated by natural gas and solar energy.

Project Development

The feasibility stage was carried out in several main steps:\r\n

• Thermal load profiles of buildings were logged and analysed.

• Load profiles were compared to the heat output of different solar collector models including at flat plate and evacuated tube collectors of different brands.

• Heat table energy outputs were used to predict the energy delivery of the range of solar collector models.

• Transient Energy System Simulation (TRNSYS) software was used to simulate the solar collector field performance.

The feasibility study showed that evacuated tube collectors were most appropriate for this project.

Detailed design was conducted by engineering company WSP Lincolne Scott. The design was based on a closed loop system that uses a variable speed drive pump control to maintain the 95°C hot water temperature required by the chiller. The design enables hot water to be used for domestic hot water/space heating or stored in two 5,000 litre tanks when demand for hospital cooling is low.

Greenland Systems was awarded the contract to supply the solar collector tubes and the installation was completed by Echuca Hospital’s engineering team. The project was commissioned into service in March 2011.

Project Outcomes

After the first 3 months of operation, the net annual savings are estimated to be $60,000 allowing for reduced electricity costs, and increased gas consumption. The total greenhouse gas savings approximate 1,400 tonnes of carbon dioxide equivalent (tCO2-e) per year. This installation has also reduced electricity demand by about 14 per cent and has allowed Echuca Hospital to avoid costly upgrades to its electricity supply.