If the world is going to ditch the use of non-renewable sources of energy, then a range of green energy options from the oceans will have to be explored.
According to the World Offshore Renewable Energy Report 2002-2007 published by UK Renewables, wave energy alone has an estimated global potential of around 1,000 to 10,000 Gigawatts.
But global cumulative capacity from ocean energy only reached about 65 megawatts as at the end of 2020, according to the latest report from Ocean Energy Systems.
As non-renewable energy sources keep threatening the existence of humanity in future, technologies to tap tidal and wave power from the movements of oceans have become more critical.
To boost the production of wave electricity, companies around the world are now in a race, deploying various technologies to improve turbine performance and accelerate the commercialisation of wave power.
Scotland-based Nova Innovation, for instance, is slashing the lifetime cost of energy by 17 percent using Artificial Intelligence practices already in use in tapping wind energy, delivering an adaptive control system that improves the performance of ocean tidal turbines.
Energy generation
“Reliable tidal energy generation is now a reality. By capturing this knowledge, we can reduce the costs of tidal energy more quickly by piggybacking on their technological advances,” says Simon Forrest, chief executive at Nova Innovation.
Another promising ocean energy technology is the use of wave energy converters (WECs) devices that use the motion of ocean waves to generate electricity.
Various types of WECs have been developed, and many of these concepts work in a similar way to hydroelectric turbines — a column-, blade- or buoy-shaped device sits on top of or under the water, where they capture the energy generated by ocean waves acting on the device. That energy is then transferred to a generator that converts it to electricity.
Swedish company CorPower Ocean has been leading the way in this front, announcing that it will install a nine-metre-diameter spherical buoy WEC for its first ocean trial by the end of this year.
“Our ultimate goal is that our technology would complement wind and solar, providing the lowest cost and most reliable path for the world to achieve 100 percent renewable energy systems,” says Javier Verdeguer, senior composite design engineer at CorPower Ocean.
Finnish company AW-Energy has developed what it calls a wave roller that converts ocean waves into energy and electricity. The wave roller can be fully submerged and anchored and operates in near-shore areas at depths of between eight and 20 metres.
Power storage
The bottom fixed panel of the device, which acts as an oscillating wave surge converter captures the ocean wave energy and converts the movement to electricity using the power storage and hydraulic system.
The electrical output generated from this renewable wave energy power plant is connected to the electric grid via a subsea cable.
Wello, another Finland based company, is a manufacturer of wave energy converters that produce electricity using a rotating mass encased in an asymmetrically designed hull, which rolls with the pitch and heave of the waves.
The rotation of the mass drives an electric motor, which in turn produces electricity. Its patented key invention is to convert wave movement to gyration, which is then amplified. It uses similar technology components used for offshore wind energy.
In the United States, Resolute Marine Energy is focused on developing a near-shore, bottom-mounted hinged flap design.
As a near-shore, shallow water wave energy converter technology, a much lower proportion of total project costs need to be spent on the transmission system that carries energy from the device to the shore.
Columbia Power Technologies, a wave energy developer in the US has designed a wave power system to capture energy from passing waves and produce electricity onboard the device.
Its StingRAY wave power system uses the floats and spar that independently react to the shape of the passing ocean wave.
Each float is directly coupled by a drive shaft to its rotary generator. As each float rotates, so does its generator, which creates electricity.
Israel-based Eco Wave Power is manufacturing wave energy devices that have an in-built automatic control system that is responsive to floats rise and submersion process, installed over existing stable breakwaters, peers, and floating or fixed platforms.
The product assembly consists of shaped buoys to capture and convert wave energy into electricity. The wave clapper and the power wing that rise and fall with the up and down motion, lifting force, change of water level, hydraulic air lock, and incident flux of waves.
Onshore generators rely on waves rolling across shallow continental shelves close to land. As such, they see less extreme conditions than those in deeper, offshore waters.
Eco Wave Power’s technology uses land-based generators with floating arms deployed over the side of a pier. This rise and fall with waves, generating energy via hydraulic compression.
This hardware will test the real-time data monitoring software, but Eco Wave plans to make it usable for offshore installations using hydraulic compression.
“Even though our operations and maintenance procedures are easier, there is still a significant value in having an efficient control system with real-time data.
“The control system will basically collect info from a wave buoy — which is external to the power station — and show how much energy should be generated from data collected about wave height,” says Eco Wave CEO Inna Braverman.
If the software, which can accurately predict the wave energy generated, becomes widely accepted, it could be a significant step forward in the sector.
“This shall lower the risks of wrongly forecasting energy generation amounts in a certain site in question, which will in turn minimise the financial risk for the debt givers,” notes Mr Braverman.
Since its inception in the 19th century, wave power has watched a green tide roll in. But this rising tide has not lifted all boats equally, and all forms of ocean-based energy remain underdeveloped.
Most ocean-based energy generation and development comes from tidal power, stemming from the gradual swell of changing tides caused by the moon. Wave power takes its energy from waves, in turn whipped up by the wind.
But the last decade has seen technology unlock the opportunities in wave energy, overcoming the challenges posed in previous decades and opening the doors to the adoption of clean energy.
According to a report by the International Renewable Energy Agency (IRENA) released in December 2020, installed wave power capacity reached 2.31 megawatts last year.
However, the report states that wave energy devices are rapidly increasing in size and power output, and “around 100 megawatts of new instalments can be expected in the coming years.” BY DAILY NATION