Smart Renovation Strategies for Sustainable Electrification
This project aims to deliver a smart, holistic renovation strategy for existing buildings with ground source heat pumps considering a range of prosumer technologies. We take a user-centric approach by considering the diverse needs and preferences of decision-makers and qualify potential solutions through the lens of tradeoffs between technical, economic, environmental, and social factors.
Funded by: Energimyndigheten in the ReBygg Program
Time period: March 2024 – February 2027
Project partners:
- KTH Energy Technology
- Samster AB
- Bengt Dahlgren Stockholm Geo AB
- Beteendelabet AB
- DualSun Nordic AB
Background
Sweden is at the forefront of heat pump technology, particularly ground source heat pumps (GSHPs). Utilizing the ground as a heat source presents several challenges, including thermal degradation due time, design flaws, limited drilling space, or the increasing density of boreholes in urban areas. Furthermore, as buildings and heat pump technology evolve, there's a need to address changing heat demands and efficiency levels. Upgrading to more efficient heat pumps often strains existing boreholes and raises electricity demand, leading to higher costs.
To counter borehole temperature degradation, additional boreholes or ground loops may be necessary, adding to renovation expenses. While improving building efficiency can reduce heat demand, it may also inconvenience occupants. Alternatives such as air source heat pumps (ASHPs) or solar energy regeneration could provide cost-effective and less-invasive solutions. Additionally, battery storage and smart controls offer ways to manage peak power demands.
The energy landscape in Sweden is rapidly changing, with consumers seeking cost-effective solutions, leading to a surge in heat pump replacements. Similar trends are observed in prosumer technologies like solar PV and batteries, adding complexity to building energy system renovations. As the electricity system and market evolve, there's a growing need for clear objectives, comprehensive analysis, and easily adoptable solutions to address these challenges effectively.
Aim and Objectives
The first goal of the project is to advance knowledge in the renovation of GSHP through expanded ground energy extraction, regeneration, and storage. The integration of new heat sources with old boreholes creates a complex challenge around systems design and operation, such as thermal load imbalances within the borehole field, independent hydraulic control, and regeneration via active heat injection. A novel phase-change, thermal storage technology which is installed underground will also be modeled dynamically for the first time within this project. Empirical data from field tests will inform the geoenergy model development to ensure accurate quantitative results in the systems modeling.
The second goal is to quantify technically, economically, and environmentally the performance of a diverse range of system solutions for GSHP renovation. No one optimal solution is expected, but rather several solutions each prioritizing a particular performance aspect. To capture all the technological solutions, we aim to develop new, more flexible building energy models that build on existing technical capacities with integrated price signals.
Our final goal is to identify the preferences and adoption potential of the identified solutions by the end-users, e.g. homeowners in Sweden. Using the quantified systems results, we aim to present decision makers with as realistic a proposition as possible, and identify the tradeoffs used in the decision process. These tradeoffs expand on the quantitative results since they are largely subjective in their nature and relate to convenience of adoption or ownership.
Outcomes
2026/10 Update: The foundational modeling work to support the project’s outcomes has been completed. A novel borehole model which allows adding new holes during the system lifetime was integrated to existing TRNSYS models (Rodas et al., 2026) and validated in a new commercial simulation tool, OptCore, which dramatically speeds simulation time (Sommerfeldt et al., 2026). PVT collector performance and integration is well covered by numerous studies. Initial studies on each renovation technology’s life cycle impact (Dahiwale, M.S., 2026) and control strategies considering solar PV, vehicle charging, and battery management (Tavakoli, 2026) are also complete.
Looking ahead the focus is on integrating the existing results towards a singular project conclusion. Interviews collecting end-user journeys and preferences are ongoing. The new systems models with flexible borehole design are being used to run numerous simulations to describe peak load impact and identify when smart renovations are necessary, and when they are not.
Publications
Scientific Articles
International Conference Articles
Sommerfeldt, N., Ruggerini, M., Jamot, J., Beltrán, F. (2026) Comparative validation of a novel commercial simulation tool for retrofit analysis of a GSHP system with solar PVT collectors. EuroSun 2026: 16th ISES and IEA STSHC International Conference on Sustainable and Solar Energy for Buildings and Industry. Freiburg, Germany, Sept. 14-18, 2026.
Rodas, M.C., Beltrán, F., Fasci, M.L., Sommerfeldt, N. (2026) Solar PVT-assisted regeneration of boreholes with thermal imbalance in GSHP systems: a techno-economic analysis. 15th IEA Heat Pump Conference; Vienna, Austria, May 26-29, 2026.
Doctoral Theses
Master’s Theses
Tavakoli, A. (2026) Battery and Electric Vehicle Integration for Peak Power Reduction In Ageing Ground Source Heat Pump Systems. MSc Thesis, KTH Royal Institute of Technology. TRITA-ITM-EX 2026:597
Dahiwale, M.S. (2026) Life cycle carbon assessment of renovation strategies for aged ground source heat pumps. MSc Thesis, KTH Royal Institute of Technology. TRITA-ITM-EX 2026:377
Popular Science
Solhybrider ska ”värma” kalla borrhål. Energi & Miljö, nr 6-7, 4 July 2026.
Smarta renoveringsstrategier för hållbar elektrifiering - Smart Reno SE. Kyla och Värme, nr. 5/2024.
Project contact persons
