System and Actor Level Analysis of Potentially Disruptive Wastewater Heat Recovery Technologies in Buildings : A Stockholm Case Study

Abstract: This thesis presents a system and actor level analysis of wastewater heat recovery in buildings, using two case studies in Stockholm, Sweden. The choice of these case studies was to cover the installation of WWHR in both commercial and residential buildings. The first case study is from the residential district of Töfsingdalen, and the second case study is the commercial building Pennfäktaren 11. The aim of the study is to understand why actors, as identified through these case studies, have adopted wastewater heat recovery. Taking into consideration, motives, strategies, conflicts, technologies, and future perspectives. The case study analysis is further supported by a literature review, analyzing the installed systems from a technical point of view. Using semi-structured interviews and literature review as the source of data collection. Theories utilized were the multilevel perspective and the critical interface. Used for explaining how technological transitions occurs and how they are best adopted by existing actors. Conclusions drawn from the study is that Swedish buildings over the last decades have improved in energy efficiency predominantly within heating, ventilation, and lightning, while energy consumption for warm water has been relatively untouched. The identified actors frame wastewater heat recovery in a widely positive environment, having input on what to improve for its diffusion in the building sector. It is a technology they regard as new and experimental but see potential with further improvements, mostly technical and economical. The actors having adopted wastewater heat recovery have incorporated ambitious climate policies in their business models while simultaneously wanting to reduce energy costs. The motive used in the first case study, Töfsingdalen, was to design an energy-efficient building, while the second case study, Pennfäktaren 11, the motives were different and centered around enthusiasm in the technology and economic benefits (energy savings). The shared motive is the liking towards the technology being environmentally friendly. Wastewater energy recovered in the first and second case study is equivalent to the total energy consumption of 1.3 and 8.5 Swedish apartments per year. For these reasons, energy recovery from wastewater can contribute towards urban sustainable development, but it can also have disruptive potential that is necessary to investigate and mitigate. Findings suggest a critical interface between the existing regime and the early innovation adopters which could lead to both conflict and cooperation. Future research to further confirm these findings are necessary analyses aimed at investigating where in the sewer system the greatest benefit for wastewater heat recovery is located. Finally, continuous innovative development of the technology is advantageous.