Abstract
The multi-purpose nature of Sustainable Drainage Systems (SuDS) or Green Infrastructure (GI) presents a significant opportunity to store or recover heat for low carbon urban heating/cooling systems. The capacity of such systems for energy storage is strongly dependent on the thermal and hydrological boundary conditions, estimation of their feasibility requires a deep understanding of how atmospheric conditions and the near-surface hydrological regime affect heat transfer. A large-scale, outdoor lysimeter has been set up at the (UK) National Green Infrastructure Facility in order to monitor the influence of atmospheric conditions on hydrological and thermal properties of SuDS. Volumetric water content, matric suction and temperature were monitored at various depths and locations within the sand and topsoil layer. Additionally, thermal conductivity at multiple depths, and heat flux at the surface and bottom boundary were measured. Results of the initial monitoring phase, as well as, preliminary laboratory tests are presented herein and demonstrate the complex interaction between partial saturation and heat transfer. Further work investigates the effects of rainfall and heat injection using rainfall simulation and a variable-power heating cable, respectively.
Highlights
Exploitation of the ground as a sustainable heat resource continues to gain momentum due to increasing energy demand, environmental impact reduction and urban resilience to climate change and increased population density
The work presented here investigates the potential use of a pilot-scale Sustainable Drainage Systems (SuDS) as a heat exchange site via a heavily-instrumented, vegetated lysimeter setup exposed to naturally occuring atmospheric conditions
There is a substantial difference in terms of magnitude of volumetric water content in topsoil at 100 mm and in sand at 250 mm depth throughout the period of monitoring, which is due to differences in hydraulic conductivity and water retention characteristics of the two soil types used in this study
Summary
Exploitation of the ground as a sustainable heat resource continues to gain momentum due to increasing energy demand, environmental impact reduction and urban resilience to climate change and increased population density. Ground heat exchangers (GHE) are long-term, durable and highly efficient alternatives to conventional building heating and cooling systems [2]. A novel way to increase efficiency, reduce initial capital cost and reduce valuable land uptake to provide affordable GHE systems is to utilise existing or to-bebuilt green infrastructure. Sustainable Drainage Systems (SuDS), are multi-beneficial, durable and sustainable alternative to conventional, buried infrastructure solutions to urban flood problems. The efficiency of GHE is strongly governed by the thermal conductivity of the medium in which they are installed. An investigation into the feasibility of utilising SuDS for heat source/sinks requires an understanding of their thermal and hydrological behaviour and boundary conditions. The work presented here investigates the potential use of a pilot-scale SuDS as a heat exchange site via a heavily-instrumented, vegetated lysimeter setup exposed to naturally occuring atmospheric conditions. The objectives are to monitor the hydrological changes in the soil and the response of soil to these changes in terms of thermal properties
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