Steady-state analysis of a conceptual offshore wind turbine driven electricity and thermocline energy extraction plant

Abstract

A system for using offshore wind energy to generate electricity and simultaneously extract thermal

energy is proposed. This concept is based on an offshore wind turbine driven hydraulic pump supplying

deep seawater under high pressure to a land based plant consisting of a hydroelectric power generation

unit and heat exchanger. A steady-state system model is developed using empirical formulae. The

mathematical model comprises the fundamental system sub-models that are categorised as the rotor,

hydraulic pump, pipeline, hydroelectric turbine and heat exchanger. A means for modelling the seawater

temperature field across a two-dimensional bathymetry is also discussed. These mathematical models

are integrated into a computational tool and a brief parametric static analysis is undertaken. The results

illustrate the effect of pipeline diameter, rotational speed of the grid connected hydroelectric turbine, and

the turbine distance from shore on the overall performance of the system. Through adequate parameter

selection, the total rate of energy output for such a system, consisting of both electricity and thermal

energy, is shown to increase by as much as 84%, when compared to a conventional wind turbine having

an identical rotor diameter but which supplies only electrical energy.