The point of coupling of energy storage to marine/offshore electrical networks

Abstract

The current usage of the term “hybrid electric power”, when referring to electrical networks installed on offshore and marine assets refers to the coupling of energy transformation systems (ETS) that utilize different technologies to exchange energy with the electrical network. An ETS is composed of an energy transformation device (ETD) and if necessary an energy converter that is utilized to match the electrical characteristics of the ETD to those of the electrical network; the converter facilitates the exchange of energy between the ETD and the electrical network at the required rate. An ETS may also be known as a source if it capable of supplying net positive energy to the electrical network for consumption by the loads. Energy exchange between the electrical network and the ETD may be unidirectional or bi-directional. Bi-directional energy exchange implies that the ETD has energy absorption capability. Energy absorption can manifest itself most economically with energy storage capability, alternately it may manifest itself as the ability to dissipate energy. Not all ETS that have energy storage capability may operate bi-directionally. Unidirectional ETS's include the “traditional generators” utilizing combustion based diesel engine, gas turbine or boiler + steam turbine prime movers as well as “alternate ETS” such as fuel cells and primary batteries that also have energy storage capability. Unidirectional ETS such as wind turbine generators and solar energy do not have energy storage capability as we commonly understand it. Bi-directional ETD's include secondary batteries, capacitors and flywheels. Hybrid electric power systems offer the opportunity to improve safety, reliability, operational efficiency and reduce fuel rate, environmental footprint and maintenance costs when compared to traditional electrical power systems.