Ocean Thermal Energy Conversion (OTEC) is a process able to produce base electricity through the temperature differences existing between warm seawater at the surface and cold depth seawater. Up to now, very few experiments have been conducted and oil prices fluctuations have often prevented results exploitation. Recently, two factors have re-launched researches: a need for the production of a renewable energy ensuring the stability of the electric grid and the increase in oil prices. The purpose of this experiment is to demonstrate the sustainability of an offshore 10 MW power plant. Some issues first need to be examined: heat exchanges, control strategies, cycle risks, working fluids, and thermodynamic cycles. This paper presents an experimental prototype as a first steppingstone of an “Eliminating Risks Program” and as a preliminary installation to the setting up of the first full scale OTEC power plant. The prototype is a reproduction on a reduced scale of a demonstration plant producing an electric power of 10 MW. To reduce costs and hazards of offshore installations (waves, cyclones, maintenance, etc.), decision has been made to build an onshore plant (settled on the Réunion island), creating artificial heat sources with a heat pump. In the first part of the paper, the principle of OTEC will be explained. Then, the prototype detailed: cycle, main components (the electricity production is directly related to the quality of the heat exchanges, so some different heat exchanger technologies are developed), working fluids, heat sources, and control strategies. Finally, results of an experimental parametric analysis will be presented, highlighting the major importance of heat exchanges, within the evaporator. Results show, for instance, that a vertical plate-type evaporator show better capacities than a shell and tube one.