• Energy Research

Abstract Growing urban populations, changes in rainfall patterns and ageing infrastructure represent significant challenges for urban water management (UWM). There is a critical need for research into how cities should adapt to become resilient to these impacts under uncertain futures. UWM challenges in the Ebbsfleet Garden City (UK) were investigated via a participatory process and potential sustainable solutions were explored using a System Dynamics Model (SDM). Collaborative development of the SDM by the Ebbsfleet Learning and Action Alliance developed stakeholders’ understanding of future UWM options and enabled a structured exploration of interdependencies within the current UWM system. Discussion by stakeholders resulted in a focus on potable water use and the development of the SDM to investigate how residential potable water consumption in the Ebbsfleet Garden City might be reduced through a range of interventions, e.g., socio-environmental and economic policy incentives. The SDM approach supports decision-making at a strategic, system-wide level, and facilitates exploration of the long-term consequences of alternative strategies, particularly those that are difficult to include in quantitative models. While an SDM can be developed by experts alone, building it collaboratively allows the process to benefit from local knowledge, resulting in a collective learning process and increased potential for adoption.

Abstract Growing urban populations, changes in rainfall patterns and ageing infrastructure represent significant challenges for urban water management (UWM). There is a critical need for research into how cities should adapt to become resilient to these impacts under uncertain futures. UWM challenges in the Ebbsfleet Garden City (UK) were investigated via a participatory process and potential sustainable solutions were explored using a System Dynamics Model (SDM). Collaborative development of the SDM by the Ebbsfleet Learning and Action Alliance developed stakeholders’ understanding of future UWM options and enabled a structured exploration of interdependencies within the current UWM system. Discussion by stakeholders resulted in a focus on potable water use and the development of the SDM to investigate how residential potable water consumption in the Ebbsfleet Garden City might be reduced through a range of interventions, e.g., socio-environmental and economic policy incentives. The SDM approach supports decision-making at a strategic, system-wide level, and facilitates exploration of the long-term consequences of alternative strategies, particularly those that are difficult to include in quantitative models. While an SDM can be developed by experts alone, building it collaboratively allows the process to benefit from local knowledge, resulting in a collective learning process and increased potential for adoption.

Abstract This paper presents the research carried out in the marine renewables group of Heriot-Watt University, where the physical models of wave energy converters are first tested in the wave basin, and the results of their behaviour are then compared to the simulations performed using mathematical modelling. An OrcaFlex model is used to assess the scouring effect on bottom sediments and consequent disruption of benthic habitats, and open water tests are being conducted to compare the model performance with the actual observations. The output from OrcaFlex is then imported to Matlab, where the affected area is calculated using the time series of coordinates of touch down points of the mooring lines. The results show that the area of benthic habitats adversely affected by the leading mooring line on a typical wave energy converter (WEC) monotonically increases with the increase in wave height. In regular waves of 6 m height and 8 s period, the area of benthic habitats adversely affected by the mooring lines may exceed 60 m2. In addition to the direct effect on benthic habitats, sediment erosion by mooring lines will effect a whole range of ecosystem processes, e.g. due to changes in biogeochemical cycling and light penetration. These issues should be given a due consideration in calculations of ecological risks and EIA of any moored objects.

Abstract This paper presents the research carried out in the marine renewables group of Heriot-Watt University, where the physical models of wave energy converters are first tested in the wave basin, and the results of their behaviour are then compared to the simulations performed using mathematical modelling. An OrcaFlex model is used to assess the scouring effect on bottom sediments and consequent disruption of benthic habitats, and open water tests are being conducted to compare the model performance with the actual observations. The output from OrcaFlex is then imported to Matlab, where the affected area is calculated using the time series of coordinates of touch down points of the mooring lines. The results show that the area of benthic habitats adversely affected by the leading mooring line on a typical wave energy converter (WEC) monotonically increases with the increase in wave height. In regular waves of 6 m height and 8 s period, the area of benthic habitats adversely affected by the mooring lines may exceed 60 m2. In addition to the direct effect on benthic habitats, sediment erosion by mooring lines will effect a whole range of ecosystem processes, e.g. due to changes in biogeochemical cycling and light penetration. These issues should be given a due consideration in calculations of ecological risks and EIA of any moored objects.

This paper describes the physical model testing of an array of wave energy devices undertaken in the NTNU (Norwegian University of Science and Technology) Trondheim basin between 8 and 20 October 2008 funded under the EU Hydralabs III initiative, and provides an analysis of the extreme mooring loads. Tests were completed at 1/20 scale on a single oscillating water column device and on close-packed arrays of three and five devices following calibration of instrumentation and the wave and current test environment. One wave energy converter (WEC) was fully instrumented with mooring line load cells, optical motion tracker and accelerometers and tested in regular waves, short- and long-crested irregular waves and current. The wave and current test regimes were measured by six wave probes and a current meter. Arrays of three and five similar WECs, with identical mooring systems, were tested under similar environmental loading with partial monitoring of mooring forces and motions. The majority of loads on the mooring lines appeared to be broadly consistent with both logistic and normal distribution; whilst the right tail appeared to conform to the extreme value distribution. Comparison of the loads at different configurations of WEC arrays suggests that the results are broadly consistent with the hypothesis that the mooring loads should differ. In particular; the results from the tests in short crested seas conditions give an indication that peak loads in a multi WEC array may be considerably higher than in 1-WEC configuration. The test campaign has contributed essential data to the development of Simulink™ and Orcaflex™ models of devices, which include mooring system interactions, and data have also been obtained for inter-tank comparisons, studies of scale effects and validation of mooring system numerical models. It is hoped that this paper will help to draw the attention of a wider scientific community to the dataset freely available from the Marintek website.

This paper describes the physical model testing of an array of wave energy devices undertaken in the NTNU (Norwegian University of Science and Technology) Trondheim basin between 8 and 20 October 2008 funded under the EU Hydralabs III initiative, and provides an analysis of the extreme mooring loads. Tests were completed at 1/20 scale on a single oscillating water column device and on close-packed arrays of three and five devices following calibration of instrumentation and the wave and current test environment. One wave energy converter (WEC) was fully instrumented with mooring line load cells, optical motion tracker and accelerometers and tested in regular waves, short- and long-crested irregular waves and current. The wave and current test regimes were measured by six wave probes and a current meter. Arrays of three and five similar WECs, with identical mooring systems, were tested under similar environmental loading with partial monitoring of mooring forces and motions. The majority of loads on the mooring lines appeared to be broadly consistent with both logistic and normal distribution; whilst the right tail appeared to conform to the extreme value distribution. Comparison of the loads at different configurations of WEC arrays suggests that the results are broadly consistent with the hypothesis that the mooring loads should differ. In particular; the results from the tests in short crested seas conditions give an indication that peak loads in a multi WEC array may be considerably higher than in 1-WEC configuration. The test campaign has contributed essential data to the development of Simulink™ and Orcaflex™ models of devices, which include mooring system interactions, and data have also been obtained for inter-tank comparisons, studies of scale effects and validation of mooring system numerical models. It is hoped that this paper will help to draw the attention of a wider scientific community to the dataset freely available from the Marintek website.