http://hdl.handle.net/10468/1980 2017-10-30T17:30:54Z http://hdl.handle.net/10468/4702 The effect of model inaccuracy and move-blocking on the performance of a wave-to-wire wave energy converter , under economic predictive control O'Sullivan, Adrian C. M.; Lightbody, Gordon In this paper, an economic Model Predictive Control (MPC) is used to investigate the effects that arise from the model mismatch between the control and the system. It is shown that the average electrical power is affected by the modelling discrepancies, but that the performance is still acceptable. A move-blocking technique is incorporated into the structure of the control horizon of the MPC, where the move-blocking decreases the computational burden whilst maintaining system performance, hence drastically reducing the optimisation solving time. The MPC with the move-blocking incorporated is then tested on the most significant mismatch, where it is shown that the control horizon of the MPC can be drastically reduced while maintaining system performance. 2017-08-30T00:00:00Z http://hdl.handle.net/10468/3352 Energy harvesting for monitoring bridges over their operational life Cahill, Paul A.; Hanley, Ciaran; Jaksic, Vesna; Mathewson, Alan; Pakrashi, Vikram The use of energy harvesting materials for large infrastructure is a promising and growing field. In this regard, the use of such harvesters for the purpose of structural health monitoring of bridges has been proposed in recent times as one of the feasible options since the deployment of them can remove the necessity of an external power source. This paper addresses the performance issue of such monitors over the life-cycle of a bridge as it deteriorates and the live load on the structure increases. In this regard, a Lead Zirconate Titanate (PZT) material is considered as the energy harvesting material and a comparison is carried out over the operational life of a reinforced concrete bridge. The evolution of annual average daily traffic (AADT) is taken into consideration, as is the degradation of the structure over time, due to the effects of corrosion. Evolution of such harvested energy is estimated over the life-cycle of the bridge and the sensitivity of harvested energy is investigated for varying rates of degradation and changes in AADT. The study allows for designing and understanding the potential of energy harvesters as a health monitor for bridges. This paper also illustrates how the natural growth of traffic on a bridge over time can accentuate the identification of damage, which is desirable for an ageing structure. The paper also assesses the impact and effects of deployment of harvesters in a bridge as a part of its design process, considering performance over the entire life-cycle versus a deployment at a certain age of the structure. 2016-07-01T00:00:00Z http://hdl.handle.net/10468/4701 Wave to wire power maximisation from a wave energy converter O'Sullivan, Adrian C. M.; Lightbody, Gordon In this paper a back-to-back voltage source converter controlled linear permanent magnet generator (LPMG) is utilised as the power take off (PTO) for a point absorber wave energy converter system (WEC). It is shown that reactive control which seems promising when an ideal PTO is assumed, is actually infeasible with a real PTO as the electrical losses of the LPMG are excessive when the wave frequency is lower than the natural frequency. A Zero Order Hold (ZOH) and First Order Hold (FOH) Model Predictive Control (MPC) which maximises the mechanical power is first utilised. The two MPC systems show that more electrical power is extracted for a lower horizon when the MPC is optimised for mechanical power. The electrical losses from the LPMG and voltage source converter (VSC) are then incorporated in the cost function of the MPC systems and demonstrates significant improvements in the electrical power extracted when compared to the electrical power extracted via mechanical power optimisation. PTO force and heave displacement constraints are then incorporated into the optimisation, to further demonstrate the limitations of performance when a realistic PTO is utilised. It is shown here that the electrical power can be maximised, whilst the PTO force and heave displacement are shown to be within limits. The power quality from the ZOH MPC is then compared to the power quality from the FOH MPC. 2015-09-07T00:00:00Z http://hdl.handle.net/10468/2805 Effects of tidal range on mooring systems of wave energy converters Murphy, Stephen; Bhinder, Majid A.; Casaubieilh, Pierre; Sheng, Wanan Wave energy converters are currently proposed to be deployed near coastal area for the closeness to the infrastructure and for ease of maintenance in order to reduce operational costs. The motivation behind this work is the fact that the deployment depths during the highest and lowest tides will have a significant effect on the mooring system of WECs. In this paper, the issue will be investigated by numerical modelling (using ANSYS AQWA) for both catenary and taut moorings to examine the performance of the mooring system in varying tides. The case study being considered is the ¼- scale wave energy test site in Galway Bay off the west coast of Ireland where some marine renewable energy devices can be tested. In this test site, the tidal range is macro-tidal with a range of approximately 6 m which is a large value relative to the water depth. In the numerical analysis, ANSYS AQWA suite has been used to simulate moored devices under wave excitation at varying tidal ranges. Results show that the highest tide will give rise to larger forces. While at lower depths, slackening of the mooring occurs. Therefore, the mooring lines must be designed to accommodate both situations. 2015-09-01T00:00:00Z