Sustainability-in-Tech : Tidal Energy ‘Kite’ That Can Power A Town

Swedish startup Minesto has developed a subsea ‘kite’ style mini power plant that generates renewable energy from tidal streams and ocean currents.

How It Works 

The ‘wing’ technology, described by Minesto as a kind of “subsea kite” and a “powerful, lightweight, and modular power plant” which can be made with a wingspan ranging from 4.9 – 12m and weighing from 2.7 – 28 tonnes. Anchored to the seabed by a long cable tether, it sits in the sea and ‘flies’ across the main flow direction of the tidal streams and currents just like a kite flies in the air.

The wing technology uses the hydrodynamic lift force created by the underwater currents to move the kite around and its onboard control system autonomously steers the kite (using rudders and elevators) in a predetermined figure-of-eight trajectory. This has the effect of pulling kite and its turbine through the water at a flow that’s several times higher than the actual stream speed. This maximises the power it can generate and reduces the size of the kite and rotor required to collect the energy compared with a fixed turbine.

The turbine shaft inside the kite turns the generator which outputs the electricity to the grid via a power cable in the tether and a seabed umbilical to the shore.

Harnessing A Reliable And Inexhaustible Resource 

As highlighted by Minesto on its website, a balanced renewable energy mix is needed for the world to move towards a sustainable future energy system. Tidal streams and ocean currents are reliable and inexhaustible, available all over the globe, and are a rich source of energy that can be converted to a reliable and local source of renewable energy. This is why an easy to deploy and effective technology that can harness and use this endless resource (such as a simple kite system technology) could be a low cost and effective way to produce renewable (green) energy anywhere around the world (the ocean covers 71 per cent of the earth’s surface).

Predictable 

Also, unlike wind and solar, tidal streams and ocean currents are predictable, i.e. they’re caused by the gravitational forces exerted on the earth by the moon and are continuous and directional. This reduces risk and makes it easier in terms of control for the deployment of tidal power technology, such as Minesto’s wing/kite design.

Scalable 

The fact that the kites are a modular design which can be easily latched and unlatched (via the tether) to the seabed anywhere means that the system is easily scalable, simply by using hundreds of them across an area.

Real World Applications 

So far, Minesto reports that its wing subsea power generators have been delivering electricity to the Faroe Islands’ power grid since 2020 and, in 2022, Minesto commissioned the first power plant in Vetmannasund, Faroe Islands.

What Does This Mean For Your Organisation?

As Minesto rightly says, the world’s very necessary shift away from fossil fuels for power will involve developing and scaling a mix of innovative renewable energy solutions that make the most of existing natural resources such as wind, water, and sun. Also, with the UK being an island nation subject to tidal activity, in world where more roughly 71 per cent of the surface of the planet is covered by ocean, with its strong, constant, predictable tides, it does seem to be an area with the ability to supply vast amount of naturally generated energy if the right technology is deployed.

The advantages of the wing idea are that it can be easily and relatively cheaply deployed around the world, is scalable simply by multiplying the number used, can be placed far enough below the surface so as not to become a hazard or eyesore, and the technology is ready to go now. That said, these are relatively small turbines and even with many of them, there’ll still be a need for a mix of other ideas and solutions to harness the power of the waves.

These ideas will need to be part of wider mix of sustainable and renewable energy generating schemes that between them can offer enough power to seriously cut carbon emissions. Furthermore, they’ll need to supply the considerable energy needs of homes and businesses, provide power that’s affordable, have a low environmental impact, and thereby help the world to meet its climate targets as quickly as possible while still supporting the growth of the world’s economies.

As Minesto says, its wing solution ads a “step of energy conversion” that “expands the global tidal and ocean currents’ extractable potential.” 

Sustainability-in-Tech : Offshore Wind Makes Green Renewable Hydrogen

German company Lhyfe is showing how the challenges of producing green hydrogen can be met by using offshore floating wind-to-hydrogen turbines and electrolysers.

The Advantages of Hydrogen 

The great advantages of hydrogen as a fuel include dramatically reduced greenhouse gas emissions, it only produces water vapour as a by-product when burned, it has a high energy density, and it can be produced from renewable sources, thereby making it a cleaner and more efficient fuel option for various applications.

The Challenges 

Extracting hydrogen at scale through the electrolysis of water using renewable energy is a little used (1 per cent of global production) but very promising way to produce green hydrogen. However, its production comes with some key challenges which are:

– The need for powerful wind turbines (and plenty of wind) to power the desalination plant.

– The need for abundant water resources from which to extract the hydrogen.

– The high costs of some current methods of converting energy at sea and bringing it in a cable to shore (the cable is the costly part).

The Answer? Offshore Wind Farms Connected to Electrolysers

German company Lhyfe believes the answer to these challenges is to use high capacity offshore floating wind farms with turbines connected to electrolysers that utilise seawater, using the green energy to power the separation process.

Using powerful wind turbines offshore harnesses abundant wind energy and by connecting them to electrolysers which utilise seawater, plus a hydrogen production plant, the process overcomes the previous challenges because:

– Seawater is an abundant source of hydrogen.

– Converting the electricity to hydrogen using the seawater and an offshore production plant beneath the turbines, means the hydrogen can be piped ashore (there are many existing North Sea pipelines). This is much less costly than using expensive electric substations and cables.

Two Plants Commissioned Following Successful Pilot 

With this in mind, in September 2022, Lhyfe installed the world’s first renewable green hydrogen pilot plant at sea, capable of producing up to 400 kilos of hydrogen a day off the Atlantic coast.

The success of Sealhyfe has led to the commissioning of the first floating platform for green hydrogen production off Le Croisic, directly connected to a floating wind turbine, with a second, much larger project planned called HOPE, this time off the coast of Belgium. Its 10 MW production unit, due for commissioning in 2026, will have the capacity to produce up to four tonnes of green hydrogen per day.

Is Hydrogen Dangerous As A Fuel Source? 

Anyone who’s watched the black and white film of the hydrogen-filled Hindenburg airship exploding will be aware of how flammable hydrogen is. It also has a low ignition point, and is odourless and colourless, making leaks difficult to detect. That said, other fossil fuels we use (e.g. petrol and gas) also come with similar risks but are generally used safely. Also, with hydrogen, dispersal in air can mitigate the risk of explosion, and various safety measures can be employed to handle and store it safely.

Oxygen 

One other beneficial aspect of extracting hydrogen from seawater is that oxygen is also produced as a byproduct. Lhyfe is developing ways to re-inject this oxygen by-product back into aquatic environments, which (due to global warming and polluting industrial activities) are increasingly depleted of oxygen, in order to re-oxygenate them. This is particularly important since 50 per cent of the oxygen on earth originates in the ocean and scientists have observed declining dissolved oxygen levels in the global ocean since the 1950’s, predicting a further decrease of up to 7 per cent by the year 2100 as a result of ocean warming and nutrient pollution.

What Does This Mean For Your Organisation? 

Not only is there a well-publicised need for urgent CO2 emission reduction and decarbonisation of our lifestyles and industries, but there’s also a need to find ways to stabilise and restore the functioning of ecosystems in order to limit global warming to 1.5°C.

Lhyfe’s idea for sustainable green hydrogen production appears to address both issues, i.e. by proving a sustainable green fuel (hydrogen) and by putting the oxygen by-product of the process back into the ocean.

The hydrogen from offshore farms produced at sea (using just seawater and wind energy) could count towards decarbonising known high emitters of CO2 on land, e.g. lorries, buses, and waste collection vehicles, and industry (e.g. in the production of chemicals, metals, glass, steel, and more). As such, green hydrogen could have a significant and positive impact on many industries and could create new opportunities as a new industry of its own. That said, extracting hydrogen at scale through the electrolysis of water using renewable energy is still relatively new and little used, making up only 1 per cent of global hydrogen production. Investment and some considerable scaling-up will be needed to help increase its impact and it may also take some time to deploy more of these green hydrogen windfarms in more places around the world.

However, the technology now exists, has proven successful in trials and looks set to be one of many ways that can be used to tackle the climate crisis and targets related to it. Offshore wind offers more additional scale than most other renewable power sources, meaning that that linking hydrogen-producing units to turbines does at least have the potential to be scaled-up and could prove to be a realistic way to help reduce our reliance on natural gas.