Hopkins Correctional Centre

GEOptimize Inc provided the GHX and district geothermal system design for the Hopkins Correctional Centre in Ararat, Victoria, Australia. The facility consists of a central administration building of approximately 30,000 ft² (2,800 m²) and three groups of inmate cottages totaling approximately 35,000 ft² (3,250 m²), distributed across a 3-acre site.

The administration building is fully heated and air conditioned, while the inmate cottages are served by space heating and domestic hot water only. To reduce CO₂ emissions and avoid fossil fuel use, the Victoria Government selected a GSHP system to provide space conditioning and domestic hot water for the entire facility.

The warm Australian climate and differing building load profiles created a significant thermal imbalance challenge for the vertical borehole GHX systems. The administration building exhibited a cooling-dominant load profile due to high internal gains and year-round cooling demand, resulting in a net annual heat rejection to the ground. Conversely, the cottages were heating-dominant, extracting more heat from the ground annually due to the absence of cooling loads.

If designed as independent GHX systems, the administration borefield would experience long-term temperature rise, reducing heat pump efficiency, while the cottage borefields would experience gradual temperature decline due to sustained heat extraction. Oversizing the borefields would have increased capital cost and only delayed long-term thermal degradation.

To address this, an integrated “energy transfer pipe” system was developed to hydraulically connect the individual GHX modules across the site. This configuration allows thermal energy exchange between the administration building and cottage borefields. Warm fluid from the cooling-dominant administration GHX can be transferred to the heating-dominant cottage GHXs, while cooler fluid from the cottage GHXs can be circulated to the administration building GHX. This district geothermal energy transfer approach moderates loop temperatures across the facility, maintains long-term thermal balance, and preserves heat pump performance without excessive borefield oversizing.