|Fig. 1: Installation process of an underwater communications cable in Chile. These cables are much smaller than power cables. (Source: Wikimedia Commons)|
Underwater power cables are becoming an increasingly more demanded form of energy generation. However are the benefits enough to provide more research and resources into this source of energy. Through this I will go through an example of these cables, list how much energy these cables can transfer, and come to a conclusion on the need for these cables.
The cables work by getting energy from a source out over water, usually by wind turbines, and using massive cables that lie on or under the seabed to transfer that energy to the land. In the figure we see an installation of a communications cable, which would connect to a land base station such as would a power cable. These cables can range from under 20 miles to over 350 miles in length depending on where the energy needs to be transferred. A particular cable in the German North Sea will span nearly 100 miles and cost $340 million to build. It will connect to a wind farm that will use 80 wind turbines to provide enough energy to power 400,000 homes.  The same Italian-based cable- making group, Prysmian Group, is also looking to link the Scottish and English power grids through these cables with a $1.1 billion, 239-mile cable project under the Irish Sea.  These cables can also generate up to 300 kV and 1000 MW. 
The NorNed submarine cable will allow the Dutch to draw on the hydropower generated in Norway during their daytime peak demand period, while the Norwegians can draw on the power from Dutch coal-burning power plants when they need it. This project will increase efficiency so much throughout the linkage of both power grid systems that carbon dioxide emissions is estimated to be reduced by nearly 1.7 million tons per year.  The cable will span 360 miles long and will have a transmission capacity of 700 MW at 450 kV.  This cable link will be among the longest cable links in the world so the question of efficiency and electrical losses are important over a distance like this. The cable uses a 12-pulse converter for ±450 kV DC transmissions. This transmission has been proven and is used in many other cables, but not in one of this distance before. Despite the distance of this cable however, electrical losses are shown to be only 3.7% at 600 MW of transmitted power.
There are actually many advantages to using these types of cables. I will provide four major advantages, but there are more. The first advantage is that it is a source of renewable energy. With these cables using energy from wind turbines or ocean power, they are reducing human dependency on fossil fuels and helping us to move towards a much cleaner energy using society. The second advantage is that these cables don't interfere with human matters. Because the wind farms are located way offshore and the cables bring back the energy, they don't interfere with the people on land in ways that a giant power plant, factory, nuclear reactor, or solar/wind farm on land might. For this same reason they also allow for more of the land to be used for other purposes. The third advantage is that sea animals actually use the cables as a place to live near. Studies show that the cables have little to no interference with the marine animal life and that some types of algae and marine life actually grow near or on the cables providing a healthy reef and area to thrive.  The fourth advantage is that the cables allow for power to be transferred to area, which could not get that power without them. Areas like New Zealand, small islands off Japan, the Northern European Area, and areas in Africa and South America all benefit from these cables. These cables allow for a way to get power to all of these areas without much intrusion to the land area and as a safe and secure way to get this power around the globe.
Underwater power cables are a great way to transfer energy to areas that need it and are efficient and safe enough to do so. They come with many advantages and they allow for energy to be created and distributed in a clean way. I believe that this source of energy is great and needs to be used more.
© Colin McCall. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 P. J. Kiger, "New Energy Projects Boost the Use of Undersea Power Cables," National Geographic, 18 Aug 14.
 "Submarine Power Cables," Asea Brown Boveri, 2006.
 L. Carter et al., "Submarine Cables and the Oceans - Connecting the World," United Nations Environment Programme, 2009.