A Blue Barrier combines the technology of a storm surge barrier with that of a tidal array. Energy-wise, the civil structure of a Blue Barrier channels the water to the turbines and ensures the full use of the available tidal flows. Alongside conventional, river-based hydropower and free-stream offshore tidal energy, the Blue Barrier is a third type of hydrokinetic energy system.
The characteristics of Blue Barrier energy are comparable with hydropower because of the forced nature of the flow, the decay of water and the onshore location. At the same time, it is tidal energy, with a very limited decay (up to 15 metres – and in the Netherlands limited to approximately only 4 metres) and the high impact of salt water.
These divergent characteristics mean that Blue Barrier turbines must differ from their free-flow tidal offshore cousins. The greater available space and lower water speeds in open sea allows tidal turbines to be much larger at the same power setting.
Despite this, Blue Barriers in the Netherlands, and in delta areas worldwide, can be profitable even when the available head is very low – up to 4 metres in the case of the Netherlands. Additionally, Blue Barriers have little impact on the environment. They are generally fish friendly and don’t require dams and reservoirs upstream or create dry areas downstream.