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The vertical temperature distribution in the open ocean can be simplistically described as consisting of two layers separated by an interface. The upper layer is warmed by the sun and mixed to depths of about 100 m by wave motion. The bottom layer consists of colder water formed at high latitudes. The interface or thermocline is sometimes marked by an abrupt change in temperature but more often the change is gradual. The temperature difference between the upper (warm) and bottom (cold) layers ranges from 10°C to 25°C, with the higher values found in equatorial waters. This implies that there are two enormous reservoirs providing the heat source and the heat sink required for a heat engine. A practical application is found in a system (heat engine) designed to transform the thermal energy into electricity. This is referred to as OTEC for Ocean Thermal Energy Conversion. Several techniques have been proposed to use this ocean thermal resource; however, at present it appears that only the closed cycle (CC-OTEC) and the open cycle (OC-OTEC) schemes have a solid foundation of theoretical as well as experimental work. In the CC-OTEC system, warm surface seawater and cold seawater are used to vaporize and condense a working fluid, such as anhydrous ammonia, which drives a turbine-generator in a closed loop producing electricity. In the OC-OTEC system, seawater is flash-evaporated in a vacuum chamber. The resulting low-pressure steam is used to drive a turbine-generator. Gold seawater is used to condense the steam after it has passed through the turbine. The open-cycle can, therefore, be configured to produce desalinated water as well as electricity.

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10The complex wave climate of Hawaii includes a mix of seasonal swells and wind waves from all 11 directions across the Pacific. Numerical hindcasting from surface winds provides essential space-12 time information to complement buoy and satellite observations for studies of the marine 13 environment. We utilize WAVEWATCH III and SWAN (Simulating WAves Nearshore) in a 14 nested grid system to model basin-wide processes as well as high-resolution wave conditions 15 around the Hawaiian Islands from 1979 to 2013. The wind forcing includes the Climate Forecast 16 System Reanalysis (CFSR) for the globe and downscaled regional winds from the Weather 17 Research and Forecasting (WRF) model. Long-term in-situ buoy measurements and remotely-18 sensed wind speeds and wave heights allow thorough assessment of the modeling approach and 19 the data products for practical application. The high-resolution WRF winds, which include 20 orographic and land-surface effects, are validated with QuickSCAT observations from 2000 to 21 2009. The wave hindcast reproduces the spatial patterns of swell and wind wave events detected 22 by altimeters on multiple platforms between 1991 and 2009 as well as the seasonal variations 23 * Corresponding Aurthor: 2 recorded at 16 offshore and nearshore buoys around the Hawaiian Islands from 1979 to 2013. 24 The hindcast captures heightened seas in interisland channels and around prominent headlands, 25 but tends to overestimate the heights of approaching northwest swells and give lower estimations 26 in sheltered areas. The validated high-resolution hindcast sets a baseline for future improvement 27 of spectral wave models. 28 Research and Forecasting model 30 1. Introduction 31 Hawaii has unique wave climate associated with its North Central Pacific location and 32 massive archipelago. Figure 1 provides a location map to illustrate the prominent wave regimes 33 and geographical features. Extratropical storms near the Kuril and Aleutian Islands generate 34 swells toward Hawaii from the northwest to north during the boreal winter. The south facing 35 shores experience moderate swells from the year-round Southern Hemisphere Westerlies that are 36 augmented by mid-latitude cyclones in the boreal summer. The persistent trade winds generate 37 waves from the northeast to east throughout the year, while subtropical storms during the winter 38 and passing cold fronts can generate waves from all directions. The steep volcanic mountains 39 speed up the wind flows in the channels and create prominent wakes leeward of the Hawaiian 40Islands (Yang et al., 2005; Nguyen et al., 2010; Hitzl et al, 2014). These localized wind flows 41 together with island sheltering create regional wave patterns with large spatial and temporal 42 variations (Aucan, 2006; Caldwell et al., 2009; Stopa et al., 2011). 43There are increasing demands for long-term wave data in support of ocean renewable energy 44 planning, marine ecosystem assessment, shoreline management, and infrastructure development 45 in Hawaii. Altimeters aboa...

Purpose Sustainable mobility urban policies intend reducing car use and increasing walking, cycling and public transport. However, this transfer from private car to these more sustainable modes is only a real alternative where distances are small and the public transport supply competitive enough. This paper proposes a methodology to calculate the number of trips that can be transferred from private car to other modes in city centres. Method The method starts analyzing which kind of trips cannot change its mode (purposes, conditions, safety , etc.), and then setting a process to determine under which conditions trips made by car between given O-D pairs can be transferable. Then, the application of demand models allow to determine which trips fulfil the transferability conditions. The process test the possibility of transfer in a sequential way: firs to walking, then cycling and finally to public transport. Results The methodology is tested through its application to the city of Madrid (Spain), with the result of only some 18% of the trips currently made by car could be made by other modes, under the same conditions of trip time, and without affecting their characteristics. Out of these trips, 75% could be made by public transport, 15% cycling and 10% on foot. The possible mode to be transferred depends on the location: city centre areas are more favourable for walking and cycling while city skirts could attract more PT trips. ConclusionsThe proposed method has demonstrated its validity to determine the potential of transferring trips out of cars to more sustainable modes. Al the same time it is clear that, even in areas with favourable conditions for walking, cycling and PT trips, the potential of transfer is limited because cars fulfil more properly special requirements of some trips and tours.