Project investigating and evaluating the use of solar reflective materials on rolling stock

Overview

An increase in the frequency and intensity of heatwaves across the UK is raising internal saloon temperatures on rolling stock beyond acceptable limits. The thermal insulation systems within current passenger rolling stock in the UK therefore need to be improved to enable better climate change resilience on the railway.

The RSSB previously examined whether additional solar reflective materials could be available for rail applications. There is now a need for the industry to review the suitability of such materials for GB rolling stock, focusing on the roof of passenger vehicles and considering the rigourious requirements such materials must comply with.

Working collaboratively with the RSSB, industry supporters, the railway supply chain and other stakeholders, DB ESG was contracted to provide guidance for the UK rail industry. They were asked to identify and evaluate the solar reflectiveness of exterior coatings, establish possible routes to adopt more solar reflective materials, and provide a high level cost-benefit assessment on their use. DB ESG was also asked to propose a suitable test procedure for trialling the most promising materials on the roof of an in-service passenger train.

Work Undertaken by DB ESG

• DB ESG conducted extensive research to characterise the properties of an ideal solar reflective material from first principles. This provided a more detailed understanding concerning the factors influencing solar reflectivity.
• Standard frameworks were identified that have the potential to be adopted by the UK rail industry to measure and quantify solar reflectivity of existing exterior coating systems. DB ESG recommended a route for the introduction of highly solar reflective materials with regards to compliance with all necessary regulations and standards.
• A representative list of the coating materials used on GB passenger rolling stock was compiled and their solar reflective performace levels estimated based on a set of similar coating systems with known parameters. This was then used to establish a baseline performance on two fleets.
• The most suitable commercially available solar reflective coatings were shortlisted using input from the project steering group and other stakeholders.
• A detailed assessment was then carried out against the baseline, to quantify the potential benefits of the shortlisted options, taking into account operational and technical feasibility, and comparative costs and benefits. This assessment was shared with the project steering group for their input.
• DB ESG developed a set of test procedures to support the business case for introducing highly solar reflective materials, featuring several go/no-go gates, including a test plan for an in-service trial using more solar reflective materials on the roof of a passenger train.
• A final report, together with the test strategy and procedure was submitted to the steering group and the RSSB.

The findings from this report are being used by the RSSB to support manufacturers, rolling stock leasers and train operators in making informed and proactive decisions with regard to the use of more solar reflective materials.