Coupling floating wind turbines with large-scale air-conditioning systems through deep sea water pumping : case studies of system performance in European deep waters

Abstract

This chapter presents a novel concept for utilising offshore-floating wind turbines to concurrently exploit cold deep sea water (DSW) for large-scale cooling applications, as well as electricity production. This concept utilises wind turbinedriven pumps that extract cold DSW and pump it across a high-pressure pipeline to a land-based hydroelectric power station coupled to a centralised air-conditioning (AC) unit of a district cooling system. The wind-driven intermittent supply of cold water exiting the hydroelectric station is diverted to the condenser of the unit and mixed with sea surface water (SSW) to maintain a steady flow. The use of DSW lowers the condensation temperature of the refrigerant in the AC unit, resulting in an improved coefficient of performance for cooling conditions. This chapter investigates the potential application of the concept described above to four European deep offshore sites located in the Mediterranean Sea: the Greek Islands, Malta, the South of France and Spain. The numerical model used to compute the energy yield characteristics at these sites assumes a single offshore wind turbine system with modules for the wind turbine–pump assembly, the deep sea thermocline formations and the frictional/thermal losses across the pipeline and the hydroelectric turbine. Another module is dedicated to the thermodynamic refrigeration cycle for the AC unit. The study confirmed that although the losses incurred in transmitting energy from offshore wind turbines through the DSW pipeline are larger than those for conventional wind turbines relying on electrical cables, such losses may be partially or fully compensated for by the superior performance of the wind turbine-driven hydraulic pumps at high wind speeds and by the energy savings incurred in AC plants through DSW utilisation. The latter savings were found to be the highest for the Greek Islands due to favourable wind conditions also prevailing during the hot summer months.