There are several Department of Energy Marine Renewable Energy Centers, one in Hawaii involved with wave energy, primarily, and also in the development of ocean thermal energy conversion (OTEC). We have several test sites.
While sizable, the following table indicates that, realistically, marine energy sources can only be an important contributor to world power needs:
|Tidal energy||>300 TWh|
|Marine current power||>800 TWh|
|Osmotic power Salinity gradient||2,000 TWh|
|Ocean thermal energy Thermal gradient||10,000 TWh|
|Wave energy||8,000–80,000 TWh|
|Source: IEA-OES, Annual Report 2007|
The problem with ocean energy is the ocean. It gets violent and uncontrollable. The salinity screws up everything. It is expensive and challenging to operate in that environment.
Take wind power, for example. Wind turbines on solid land can produce electricity for a third the cost of generation offshore. Here is a calculation indicating the 6 cents/kWh and 18 cents/kWh difference. Sure, this was done by a student, but this was at Stanford. However, if you want something recent from the American Wind Energy Association, check out this comparison:
2 feet is typical, but up to 38 feet can be found in special locations), do it. Similarly, if the wavepower system can naturally be protected, without building expensive reinforcements, that would be attractive. But there are only a few sites where this can be possible. Most wave power experiments occur on the open ocean and storms have a tendency of wiping out those facilities. This one in Norway was well-protected, but still destroyed. While the Swedish Sotenas 10 megawatt wave power project (left) shows potential, all other efforts have either been decommissioned or remain as proposals.
Back to tidal power, here are two examples of success:
- Rance Tidal Power Station, along the Rance River in Brittany, France, has a 28 ft tidal range, operating since 1966, enjoying more than half a century of producing electricity for around 15 cents/kWh. How long ago was that? Charles de Gaulle inaugurated the plant. The capacity factor is only 28%. Yet, the question is, why did it take so long to get #2?
- Sihwa Lake Tidal Power Station, South Korea, the world's largest at 254 MW, has been operating since 2012. The tidal range here is 18 feet. If you have landed at Incheon International Airport, you have seen these enormous tidal fluctuations.
- Scotland has entered the scene with the launching of the first turbine for the MeyGen Tidal Stream Project in the Pentland Firth outside of Inverness in the Scottish Highlands. The turbine, which measures 49 feet across, will be the first of four to generate a total of four MW, and will of course be placed underwater. The hope someday is an ocean farm of 269 turbines for a capacity of 400 MW.
- Want more? Read TidalEnergyToday.
Tropical Cyclone Gita fooled me. Started as a standard weak cyclonic storm heading east, then began making a U-turn, strengthened and devastated Tonga with winds up to 145 MPH:
Gita is now at 140 MPH, but should weaken and move mostly just south of Fiji:
However, just a slight movement north, and Fiji could also be in big trouble.