What is Tidal Power?
Tidal energy is one of the oldest forms of energy generation. It is a renewable form of energy that converts the natural rise and fall of the tides into electricity 1. Tides are caused by the combined effects of gravitational forces exerted by the Moon, the Sun, and the rotation of the Earth.
Tidal energy presents an evolving technology with tremendous potential2 However, it can only be installed along coastlines. Coastlines often experience two high tides and two low tides on a daily basis. The difference in water levels must be at least 5 meters high to produce electricity.
Tidal electricity can be created from several technologies, the main ones being tidal barrages, tidal fences and tidal turbines 3.
- Tidal barrages are the most efficient tidal energy sources. A tidal barrage is a dam that utilizes the potential energy generated by the change in height between high and low tides. This energy turns a turbine or compresses air, which generates electricity.
- Tidal fences are turbines that operate like giant turnstiles, while tidal turbines are similar to wind turbines only under water. In both cases, electricity is generated when the mechanical energy of tidal currents turns turbines connected to a generator. Ocean currents generate relatively more energy than air currents because ocean water is 832 times more dense than air and therefore applies greater force on the turbines.
Tidal power is an easy to install, renewable source of energy with no direct greenhouse gas emissions and a low environmental impact4. Because the ocean’s tidal patterns are well understood, tidal energy is a very predictable energy source making it a highly attractive for electrical grid management. This sets it apart from other renewables that can be more variable.
Adoption of tidal technologies has been slow and the amount of power generated from tidal power plants is very small. This is largely due to the very specific site requirements necessary to produce tidal electricity.
Additionally, tide cycles do not always match the daily consumption patterns of electricity and therefore do not provide sufficient capacity to satisfy demand.