Monash University’s large-scale solar thermal district heating system has hit its target, writes Simon Witts.
Monash University in Clayton, Melbourne, is one of the largest campuses in Australia, with about 100 buildings over a 60-hectare site. With tens of thousands of students, staff and researchers on site each day, the university consumes huge quantities of energy for heating, cooling, lighting and technical equipment.
In line with the 2030 Paris climate commitments, the sustainability team at Monash is moving towards 100% renewable-powered campuses. Renewable electricity is already being sourced from solar PV and from the grid, but about 50% of the campus energy requirement is met with natural gas, and there are few convenient renewable energy alternatives to replace that gas.
The university uses gas to generate high temperature hot water (HTHW) via two 8MW central boilers. The hot water loop is a pressurised ring mains operating at 12 atmosphere of pressure, carrying water heated to about 150°C to service the campus buildings. Any renewable energy system needed to deliver elevated temperatures in a safe, reliable and cost-effective manner.
LCI Consulting Engineers was commissioned to investigate solutions for the site and after studying the campus heat load profile decided a “low load” boiler configuration was the best option. LCI incorporated a 1MW solar thermal field from Greenland Systems to cover the summer base heating load, with the result that the university can operate entirely off gas for most of the summer.
Greenland Systems Orange Series advanced evacuated tube modules were selected due to high efficiency at temperatures up to 200°C, well above the capability of most rooftop-compatible solar thermal technologies. Given Melbourne’s often cloudy weather, this was an important consideration in order to optimise the system output.
A key requirement was little to no maintenance or manual intervention once setup. To achieve this considerable data logging, control and automation were integrated into the new solar thermal solution. The campus building automation software (BAS) was extended to manage the solar field operation, ensuring the hydraulic pumps begin operating when the solar field temperature exceeds the HTHW loop set points. The heat from the solar field is then added into the HTHW loop via a heat exchanger in the central boiler house.
Safety was also a key consideration for the university, so a low-pressure hydraulic setup was preferred. While still operating at high temperatures, a synthetic thermal fluid was selected as the heat carrying medium in the solar field. This avoided the possibility of steam release and other potential OH&S issues.
Equipment procurement and project construction began in the second half of 2016 and the system went live in July. After the second phase is completed next year, the total project is expected to reduce gas usage at Monash by up to 20% a year.
The project had to not only make environmental sense, it also needed to make financial sense. With the university expecting to make substantial energy cost savings over the project’s expected life of more than 40 years, it certainly met these criteria. What’s more, the university is utilising cutting-edge Australian technology that has the potential to be rolled out worldwide.