Technology Engineers are trying different systems that take advantage of being thrown up and down with the ocean currents and release that kinetic energy and turn it into electricity. Some use systems where the waves spill over an artificial reef and then slowly the water as it sinks down generates energy. Other systems use mechanical elements that they get pumped up and down to produce energy that way. Those stations are not very big right now. They have maybe 75 or 100 kilowatts which are a kind of small production. It’s quite challenging because the device is in the middle of the ocean where the waves are sloshing back and forth. Maintenance is not so easy as well. But it’s it is estimated that this will become an increasing possibility to generate energy in those places of the world where waves are abundant. The problem with waves also is they’re not always there. In some seasons the waves are abundant, in other seasons the ocean is calmer. Therefore, waves are not able to produce a sustainable energy source compared to the tides.
The third way you can do energy from the ocean is you can harness the power of the great ocean currents, and there are different systems designed that look like giant kites with propellers underneath them that will then sail in the Gulf Stream and sail in the major ocean currents, have rotors that spin around and generate currents. These currents would then be transmitted through the kites. But you can also see you have the energy in the middle of the ocean, transporting on land is a bit of a challenge because you need to have plugs where you plug these turbines in and then you have to have the cables that bring the energy back to shore. Strong currents we find on the western side of ocean basins. So for example, in front of major cities like New York or Washington D.C., this would be an option. But on the eastern ocean basins, the currents are usually rather weak so cities (places) like Cape Town or Morocco couldn’t benefit from that.
Some more exotic areas to produce energy come from ocean thermal energy. The another idea is to use the difference between the warm surface and the cold deep waters. Set up like a heating system where you pump up some of that cold water and bring it together with the warmer water from the surface, and from that temperature gradient you use special substances that evaporate at low temperatures, that drives then generators and then they get evaporated and cooled down with the ocean cold temperatures. But because the temperature difference between the warm and the cold is not very big, let say between 10-15 or maximum of 20 degrees Celsius, these systems are not very efficient, so you need a lot of water to pump that. On the other hand, not everywhere on the planet, we have access to cold ocean waters. Therefore, if there is no deep ocean around the country you lived in, but other islands like Hawaii, they are located in the warm tropics and have cold waters in deep places. So they are very well suited. You can calculate that this thermal energy can produce about two times or even three times the energy needed to provide the whole world with electricity.
As Douglas Healy said, "Energy demand is very high and energy sources from wind and solar are unable to produce steady, on-demand power". Not so different with the Ocean, Ocean can produce a sustainable energy but cannot supply the demand alone.