Electricity generated by ocean currents hold promise for hydrogen cars & EVs

Hydrogen is the most common element in the universe and is often hailed as the automotive fuel of the future, due to its environmentally friendly emissions: a dribble of water and a little heat.

However, the pure hydrogen needed to power fuel-cell vehicles doesn't occur naturally. It has to be manufactured using a process that requires an extraordinary amount of electricity.

Scientists at the University of Michigan say they have invented a device that can harness enough energy from slow-moving rivers and ocean currents to power for the entire world.

The technology can generate electricity in water flowing at a rate of less than one knot (about one mile an hour), meaning it could operate on most waterways and sea beds around the globe.

Existing technologies that use water power--relying on the action of waves, tides or faster currents created by dams--are far more limited in where they can be used, and also cause greater obstructions when they are built in rivers or the sea.

Turbines and water mills need an average current of five or six knots to operate efficiently, while most of Earth's currents are slower than three knots. The new device, which has been inspired by the way fish swim, consists of a system of cylinders positioned horizontal to the water flow and attached to springs.

As water flows past, the cylinder creates vortices, which push and pull the cylinder up and down. The mechanical energy in the vibrations is then converted into electricity.

Cylinders arranged over a cubic meter of the sea or river bed in a flow of three knots can produce 51 watts, the scientists say. This is more efficient than similar-sized turbines or wave generators, and the amount of power produced can increase sharply if the flow is faster or if more cylinders are added.

To give you an idea of the invention's potential, consider this: A "field" of cylinders two stories high and built on the sea bed over an area 1 kilometer wide and 1.5 kilometers deep, with a flow of just three knots, could generate enough power for around 100,000 homes and would cost very little.

The system is called vortex-induced vibrations for aquatic clean energy, or VIVACE.

Michael Bernitsas, a professor of naval architecture at the University of Michigan, says that if man could harness 0.1 percent of the energy in the ocean, "we could support the energy needs of 15 billion people."

Because the parts only oscillate slowly, the technology is likely to be less harmful to aquatic wildlife than dams or water turbines. And as the installations can be positioned far below the surface of the sea, there would be less interference with shipping, recreational boat users, fishing and tourism.

The engineers are now deploying a prototype device in the Detroit River, which has a flow of less than two knots.

Source: Green Car Advisor