A transition to new energy systems is required at global level to cope with the challenges of climate change. It is widely accepted that new technologies will play an important role in achieving this transition. Yet, the promises and threats of new technologies are prevalent issues in politics and social debates. For example, the choice of energy conversion technologies will have direct impact on greenhouse emissions or the number of jobs that may be created in a given context, and thus be subject of political discussions and preferences.
Policymakers often look for guidance to identify and characterize the risks associated with new and emerging technologies. However, while concerns often focus direct negative impacts of specific technologies, some impacts may rather be at system level, leading to disruptive societal effects. At city level, disruptions could affect critical functions such as energy provision, water supply or transport. Such disruptions are more difficult to analyze and communicate, but improved understanding of the implications of system transformation is required to make sure policies are designed to forward optimal solutions and sustainable development. We explore a case in which technological innovation at local level may have implications at system level, leaving the overall societal and environmental benefits unclear.
This paper explores the changing context of technological systems options for heat and water recovery in the city of Stockholm, Sweden. We aim at (i) casting light on the overall implications that system reconfiguration may have for resource efficiency, and (ii) guiding policy makers towards next steps in legislation for promoting energy efficiency in buildings.
An assessment is carried out on the potential disruptive effects of new technological solutions for heat recovery. We use the system of wastewater heat recovery in Stockholm as a case study. Wastewater heat recovery can be performed locally or at system level. In the former, the heat is recovered where the wastewater is generated, or before the waste water is dispatched from the building. In the latter, the heat is transported with the wastewater, and recovered at the water treatment plant. Although local heat recovery could be beneficial, a broad use of new technologies to recover wastewater heat at the building site might result in disruptive impacts on prevailing centralized systems for water treatment and heat distribution at city level. Potential disruptions include technical adjustments requiring compensation for the reduced heat recovered, change in cost structure of service providers, and security of service supply, among others.
Currently, a wastewater treatment plant (WWTP) in the Stockholm region receives wastewater and treats it with combined mechanical, biological and chemical processes. Biogas is produced from digested sludge. The biogas is upgraded for use as bus fuel. The heat content of treated water is recovered by a heat pump (660 MW) and delivered to the district heating company. The district heating company uses various heat sources, including the recovered heat from WWTP, while the water utility company treats the sewage, and provides clean water for buildings.
Stricter building regulations together with emerging technological solutions may result in property owners choosing to recover heat locally before discharging the wastewater to the municipal wastewater treatment facilities. At system level, this may reduce energy losses in the sewage network. However, from the point of view of the water treatment utility, the reduced input temperature will lead to higher heat demand for digesters. It means more costs for WWTP and higher prices for the drinking water. As a result, although property owners would pay less for heat due to local heat recovery, they would probably need to pay more for drinking water. There are also consequences for the district heating company, since less heat will be obtained from wastewater, while the heat demand of WWTP is increased. Therefore, the district heating company may need to look for new sources of heat. At present, incineration provides a significant part of the heat used in Stockholm, but development is going in the direction of more recycling and less incineration.
In addition to heat recovery from wastewater, also water could be locally recovered. Again, property owners may be tempted to adopt combined systems for water and heat recovery on site, if they have space for it, and if cost-efficient technology options are commercially available. This would result in lower demand for treated water, with direct impact for the water utility. In this case, there are disruptions for both district heating companies and water utilities, reducing their interest to invest in new facilities. Stockholm is a rapidly growing city and this could have impact on energy and water supply security over time.
Thus, if local recovery of energy and water is up-scaled, centralized service provision as organized today is likely to be affected in the long run, changing the configuration of water and energy provision in buildings. Since market driven competition is allowed in Sweden when it comes to technological solutions, there is a clear opportunity for new players when it comes to guaranteeing the delivery of energy and clean water in buildings. In this context, there is need for insights into the potential disruptive consequences that decentralized solutions for heat and water recovery may have on established centralized urban energy and water systems. What consequences could present policies for improved energy efficiency in buildings have on energy and water security at city level? Our analysis aims at contributing science-based information that can guide and support policies for improved resource efficiency and reduced climate impact.