OTEC or ‘Ocean Thermal Energy Conversion’ is a unique method of producing electrical energy from the temperature differentials found naturally in our oceans. OTEC works by joining warm water and cold water together to turn a turbine, generating electricity, and unlike most power sources out there, since our oceans have been slightly warming over the past few decades, the potential power that OTEC can tap into has been growing.
OTEC turns the entire ocean into one giant solar panel, where the energy that the salt water collects from the sun is stored until it can be harvested by an OTEC generator. As long as the sun keeps the warm water near the surface of the ocean warm, and the cold water below stays colder, this temperature differential can be used to absorb energy.
There are two types of OTEC generators; Closed Loop and Open Loop.
A Closed Loop generator has a loop of pipes filled with pressurized ammonia. The boiling point of ammonia is normally 28 degrees fahrenheit, but this can be raised to just above freezing if put under pressure. Next, warm water from the surface is put into a heat exchanger with the ammonia to boil it, while on the other side of the loop, cold water being brought up from the deep ocean is put into a heat exchanger to cool it down and turn it back into a liquid. This causes the boiling ammonia to rise and spin a turbine, while the ammonia on the other side of the loop condenses into a liquid and sinks, thus causing the ammonia to cycle through the system, continuously spinning the turbine and generating electricity. Some of this electricity is used to power the pump which pulls water up from the deep, while the rest of it can be used to power our homes, businesses, and other buildings in the city
An Open Loop generator is even more useful to a floating city. In an open loop cycle, warm surface water is put into a pipe and pressure is decreased until the boiling point of water goes below the temperature the warm water is at, then the water boils and turns a turbine generating electricity. On the other side of the turbine, cold water is brought up from the deep and goes into a heat exchanger with this evaporated water, which brings it down to just below the boiling point so it turns back into a liquid. This liquid water can now be taken out of the generator and is pure fresh water containing no harmful bacteria or chemicals. In this way, OTEC can be used to provide both power and fresh water to a Seastead.
Besides producing freshwater, OTEC can also provide us with two other byproducts. One of which I mentioned last week, is cooler ocean surface temperatures. As we talked about when discussing hurricanes, water temperatures fuel hurricanes in their formative stages, and cooling of those water temperatures can reduce the size and strength of hurricanes, or even prevent them from forming entirely.
The other byproduct is nutrients. When plankton and other organisms die, their bodies and nutrients usually sink into the ocean’s deeper layers. Some of these nutrients fall onto the abyssal plain where they are eaten by crabs or small scavenging isopods and fish, while some of the nutrients drift around in the deep ocean currents. When deep water is pulled up to the surface, then released out into the shallow water near the OTEC plant, it has brought up with it many of those nutrients. This can lead to increased growth of plankton, or seaweed, which in turn can increase the fish populations, dolphins, whales, and all other kinds of sea life.
OTEC is only one kind of technology in a large arsenal that Seasteads can be equipped with to bring new life to our planet.