Mapping the value of green roofs in Swedish cities

Background

The original function of a roof is to provide shelter, however they can do so much more to contribute to sustainability. They can generate electricity with solar photovoltaics (PV); installing soil, grass and flowers can reduce heat island effect, slow down storm water runoff, reduce energy losses, and increase biodiversity; flat roofs can host planter boxes for local food production or social spaces.

One challenge to green roofs is quantifying the value they provide. Economic value is relatively easy, especially with solar energy, but the non-economic value provided to humans and nature is much more difficult to capture. In the ongoing project IoT Smart Roofs , efforts are underway to help quantify those values using novel sensors and AI techniques. The project is led by Järfalla Kommun  in partnership with Barkarby Science  and Savantic , with KTH Energy Technology playing an advisory role.

Objective

The primary objective of this thesis is to identify the installation potential of green roof types in the Stockholm suburb of Järfalla. A key subgoal is to quantify the energy generation potential from solar PV and energy savings due to biomass roofs. These energetic values can then be converted into economic value and used as a benchmark opportunity cost for other non-economic values. Another subgoal is to develop models capable of capturing green roof combinations, for example the hosting biomass and solar energy, which can result in combined benefits. The results of this thesis will directly contribute to the IoT Smart Roofs project and help guide the development of Järfalla Kommun.

Methods

Achieving the objective will require the use of urban-scale energy analysis tools. 3D city geometry will be provided by Järfalla Kommun which can be used in existing models (such as ArcGIS  or Ladybug Tools ) to quantify solar energy generation potential. Roof geometry and obstructions will inform the suitability for any given roof surface, which will require a combination of automated and manual methods. It may be necessary to write custom scripts to capture the co-placement effect of a biomass roof with solar energy, which creates a unique microclimate for calculating thermal losses in PV generation. It is possible that early sensor results from green roof testing within the project could inform model development, otherwise values taken from literature can be used. Ideally the entire municipality will be simulated, but it is possible that a subset (or multiple representative subsets) will be used for some analyses.

Learning objectives

After the thesis has been performed, the student(s) should be able to:

- Identify and describe a gap in scientific knowledge

- Develop models for rooftop analysis at an urban scale

- Perform complex techno-economic analysis with recommended actions

- Make informed conclusions supported by documented observations

Proposed time schedule, including milestones and intermediate reports

The thesis is expected to start January 2024 (wk.3/4) and be completed by June 2024 (wk.23). Intermediate reports will be due at 1/3 and 2/3 intervals, or as needed.

Workplace

Students will be offered a desk in the student thesis office at KTH Energy Technology. They are also welcomed to sit at the Savantic offices on Södermalm, particularly during periods of high collaboration with the team there. This thesis is possible due to partnerships with industrial stakeholders, however it is formally hosted by KTH and therefore cannot include renumeration.

How to apply

Interested students should email their CV and transcripts to Nelson Sommerfeldt (contact below). The scale of the project is most suited for two students working together, however solo applicants are welcome. The position will be closed as soon as matching candidates are found.

Supervisors

Claes Orsholm, CEO, Savantic AB claes.orsholm@savantic.se

Examiner