HEAT RECOVERY FROM WASTE WATER IN TOMTEBOSTRAND : Technical, Economical and environmental Perspective

This project examined the feasibility of implementing a centralized wastewater heat recovery system in Tomtebo Strand, a planned residential district in Umeå, Sweden. The main objective was to find the optimal year for implantation, based on technical, economical, and environmental factors, in relation to the district’s planned development timeline over the next 15 to 20-years period. The analysis was based on measured wastewater temperatures, expected district growth, and scenario-based calculations of heat recovery at different temperature drops (ΔT = 6–12 °C) and potential installation years between 2028 and 2040. These data formed the basis for a life cycle cost analysis (LCC), which included key indicators such as net present value (NPV), levelized cost of energy (LCOE), and potential reductions in CO2-equivalent emissions. Depending on the scenario, 56–120 GWh of heat could be recovered over a 25-year period, requiring an electricity input of 13–31 GWh. The estimated LCOE ranged from 0.48 to 2.31 SEK/kWh, while the NPV varied from –30 to +89 million SEK. Environmentally, the system could reduce annual CO2-equivalent emissions by up to 97 tonnes. The results indicated that earlier installation provides greater climate benefit, while a later start yields improved economic performance due to higher wastewater volumes and greater energy recovery. Overall, the study showed the period between 2034 and 2036 as the most suitable implementation window, balancing technical performance, cost-efficiency, and environmental impact.