Techno-Economic and Environmental Feasibility Study of Wastewater Energy Transfer (WET) Systems for Urban Campus in Cold Climates

Wastewater is an abundant yet underutilized source of thermal energy. The integration of low-grade thermal energy from wastewater via a heat exchanger and a heat pump into buildings not only enhances energy efficiency but also promotes sustainability. This study explores the techno-economic and environmental potential of such a system, known as a Wastewater Energy Transfer (WET) system. The energy and financial models were developed to simulate and compare the performance of a WET system with a conventional heating/cooling system. Toronto Metropolitan University (TMU) campus buildings were utilized for a case study and implementation of a WET system. The TMU campus buildings are ideal for evaluating WET systems due to their district energy systems that integrate various energy sources while meeting heating and cooling needs. Using local greenhouse gas (GHG) emissions factors, utility rates, and weather data, the model calculated both systems comparative energy consumption, operating costs, and GHG emissions. The modelling and sensitivity analysis of WET systems were extended to the major Canadian cities (Halifax, Montreal, Winnipeg, Calgary, Vancouver, and Toronto) to evaluate comparative impacts. Montreal showed the highest operating cost savings at $2,057,855, while Calgary had the lowest at $128,544. Winnipeg led in GHG reductions, offsetting 5,464 tonnes annually, whereas Montreal had the smallest reduction at 21 tonnes. The study shows variability in WET system performance across Canadian cities, influenced by local factors such as weather and utility rates. Given the significant thermal energy waste in urban wastewater, the study suggests a strong potential for the wider adoption of WET systems as sustainable energy solutions in urban buildings.