title: Performance and environmental sustainability assessment of an integrated solar water heater designed for disassembly
Creators: name: Saint, Ruth M.
Publisher: name: Edinburgh Napier University
Year: 2022

description: Recent amendments to the Climate Change (Scotland) Bill set an ambitious target of net-zero by 2045 and the Scottish Government has highlighted the need for policy reform to decarbonise heat. Minimum requirement for hot water provision through renewable technologies are already included in Section 7 (Sustainability) of the Scottish Building Regulations. However, with growing demand for affordable housing in Scotland, and modular construction becoming increasingly popular due to its affordability, energy performance and sustainability, there is an urgent need to identify solutions for a renewable provision of heat that aligns with construction trends and societal requirements.

This research aims to optimise a unique integrated collector-storage solar water heater (ICSSWH) design for integration into buildings under Scottish weather conditions, underpinned by a lifecycle perspective and incorporating circular economy principles. The ICSSWH evaluated was specifically engineered for integration into modern roof structures, to be compatible with offsite modular construction as a plug-and-play, fit-and-forget system, and designed for disassembly to improve reuse potential at the end of its useful life. Two design configurations were evaluated, baffled and finned, alongside two heat retention methods, additional insulation and a night cover.

Extensive field tests were conducted, with the designs embedded into a structural insulated panel, under a realistic draw-off profile to mimic practical application and quantitively assess real-life, seasonal performance. The baffled system outperforms the finned in every scenario and the night cover offers the greatest improvement in heat retention. Life cycle assessment (LCA) complemented field tests to establish whether operational savings achieved by the system would outweigh the embodied impacts. LCA showed that the ICSSWH can recoup both its embodied energy (3.7-5.5 years) and carbon (4.9-13 years) within its useful life. Additionally, the cost analysis demonstrated the economic viability with payback times of 5.8–7.7 years when replacing an electric system.

These analyses demonstrates the environmental sustainability of the system, and the element of integration into the roof structure, as part of a pre-built package, illustrates the benefits of its practical application. With extensive uptake of this technology, significant carbon savings could be achieved. If ICSSWHs were integrated into 10,000 new builds, the potential carbon savings would be approximately 13,200 tonnes of CO2e, bringing the operational carbon emissions associated with the hot water demand of the new homes down by 42%. This work advances existing knowledge through: innovative design for disassembly and integration into the roof structure; a circular approach, considering sustainability at the design stage and promoting reuse over disposal; a feasible prototype evaluating real-life performance using a seasonal testing method and realistic draw-off profile.