Low-temperature heating systems for sustainable retrofitting

What is the topic of your Doctoral Thesis?

What will our existing buildings look like in the future? How can we promote the development of our future buildings to be more sustainable and energy efficient, at the same time, without compromising thermal comfort and indoor air quality? In my doctoral thesis, I investigated the technical solutions of sustainable retrofitting in Swedish residential buildings, with a focus on implementing low-temperature heating systems.

Why did you choose this topic?

With a background in energy and environmental engineering, I have always been aware of the importance of building performance. Existing residential building and service sectors account for a major part of the final energy usage in cities. Both the EU energy roadmap 2050 and Swedish national energy strategy have pointed out that: higher energy efficiency in existing buildings is one of the most significant keys to transforming the current energy system. Retrofitting has been considered one of the most efficient ways to attain the sustainability energy and climate targets for decades. Based on the long-term experiences of our group in the field of low-temperature heating (LTH) systems, we have found that LTH shows promising advantages in providing occupant satisfactions from a thermal comfort perspective. As a result, I am very interested in further investigating how much energy efficiency can be improved, and how we can further develop and integrate this technology from engineering and scientific perspectives in retrofitting practice. I found this topic very challenging and attractive.

What are the most important results?

The main contribution of this thesis was developing methodologies furthering the development of modeling tools. The method was a combination of three integrated modeling techniques during different steps and phases of retrofitting modeling. Three types of LTH systems in retrofitting practice were analyzed in detail, such as ventilation-radiator systems, baseboard-radiator systems as well as different designs of conventional radiator systems. The principle of the methods developed was a top-down approach that underpinned the general definition of LTH and sustainability criteria, such as final and primary energy modeling, thermal comfort evaluation and sustainability quantifications in terms of life-cycle cost/assessment. Results were aimed at a target group consisting of decision makers such as building owners, property managers, developers, architects, consultants as well as engineers all of whom may be in need of retrofitting guidelines.

Did you come across something unexpected during your thesis research?

One of the most important unexpected experiences was the lack of communication between academia, industries and public authorities. We have extensive working experiences in modeling and simulations. However, as engineering majors, good validations and on-site measurements are always important to validate our modeling results. However, during the implementation of our measurements, we found that the real-life performance could have large deviations. This was due to the weak communication between industries, researchers and occupants. As researchers, there is a risk that we are not familiar with how technicians work with practical engineering cases. At the same time, occupants and industries may need clearer guidance and indications from academia how the new system/technology should be operated and systematically designed for the suitable conditions/environment.

Who will benefit from your results?

I think the major groups that will benefit from my results are industries and engineers who are working in the relevant field of retrofitting and LTH. I think the studied solutions and engineering recommendations can potentially provide technical guidance for HVAC technicians, decision-making supports for building owners/politicians, and guidelines for occupants to accelerate the sustainable transformation of existing Swedish residential buildings. Additionally, for young researchers who are interested in the relevant area to know about the current development and new progress/techniques in modeling and designing LTH systems.

What will you do next?

Now we have a promising new project, which is a continuation of my PhD research work. I will keep working on our new project and further develop some of my thoughts and limitations that I experienced during my PhD study. More importantly, as I pointed out earlier that lacking of communication between academia and industries are important. As a result, I am also willing to partly work in industry to obtain more practical knowledge and putting more efforts into connecting academic research with the R&D products for our industry partners.

Qian Wang presented his doctoral thesis Low-temperature Heating in Existing Swedish Residential Buildings- Toward Sustainable Retrofitting in October 2016.