Are floating platforms the future of marine renewable energy?

It’s hard to tell just yet. Floating platforms have been bulwarks of the oil and gas industries for decades. If we can use a floating platform to drill from the ocean surface down through kilometers of bedrock, how hard could it be to mount a wind turbine or other marine energy converter on a floating platform and transmit electricity back to the mainland on cables?

The engineers tackling this question have a lot to think about. Most of their debates will shape up along the pros and cons of floating platforms for marine renewable energy. Here’s a quick look at them:

Advantages of Floating Platforms

Invisible to landlubbers. Folks on land don’t have to look at floating platforms, which can be deployed beyond the horizon and protect precious ocean views. This makes offshore wind more politically palatable.

Simplified, flexible deployment. A floating wind turbine platform can be towed out to sea fully constructed. This could potentially be much simpler and less costly than the specialized ships required to deploy embedded wind farms. Note, however, that a special port facility would still be required for the construction phase, so it’s unclear how much savings this produces in the short run.

Greater water depths. Fixed offshore renewable energy projects work best in shallow water — typically less than 200 feet (61 meters). Floating platforms, by contrast, can be deployed in waters up to a half-mile deep (800 meters) or even more.

Stronger, more reliable winds. Near shore, moving air becomes much more turbulent and dispersed. A few miles out to sea, the winds are more powerful and reliable, generating much more potential electricity. At the same time, manufacturers are building ever larger wind turbines to catch more air — so it only makes sense that these be used on floating platforms.

Turbines can be swapped out. If a fixed wind turbine goes bad and has to be replaced, it’s an incredibly complex project. Floating platforms, by contrast, can be quickly and easily towed into place or removed.

Easier inspections and maintenance. This is most true with wave- and tidal-power systems that are deployed underwater. Fixed systems are much harder to inspect and repair than floating systems.

Disadvantages of Floating Platforms

Cost comparisons. Fixed offshore wind technology gets more mature every year, lowering total costs with each new innovation. As long as these costs keep falling, floating platforms will face daunting challenges in attracting investors. ­

Unsettled engineering. A few floating-platform systems are in the water, but not enough to provide a clear picture of the optimum platform. A standard platform that can be manufactured at scale will be required to produce the economies that make offshore platforms viable. 

Environmental questions. Floating platforms require anchors on the seabed and connecting cables or chains that can disrupt offshore ecosystems. Though most biomes can adapt to the temporary construction disruption, there’s always the potential of creating artificial reefs that invite invasive species. The effects on migratory animals like whales and birds also are unknown.

Cable complexities. Extra-heavy-duty cables are required to fix floating platforms in place and endure the ravages of waves and saltwater. Suppliers in this space will need extensive experience in both deep-sea mooring lines and electricity transmission cables.

Don’t Discount the Potential of Floating Platforms

At PMI, we’re excited about the idea of adapting our decades of deep-sea cable experience to the needs of the marine renewables sector. It might not be happening as soon as we would prefer, but as long as nations around the globe establish benchmarks for tapping into the potential of renewable power, they’re going to keep looking to their shorelines — and beyond.

Related articles:
·      Market Opportunities for Offshore Wind: What Does the Future Hold?
·      Challenges in the Installation and Repair of Offshore Wind Turbines
·      Subsea Cable Trade Group Widens Focus to All of Europe

Generating electricity from waves or tides requires placing large mechanical devices in the middle of complex, fragile ecosystems. How will life respond to these intrusions?

Because we’re so early in the evolution of marine energy, environmental concerns post a host of serious questions, such as:

What have we learned from the development of artificial reefs?

Fixed structures in the ocean naturally invite the arrival of reef species, creating artificial reefs. If the introduction of reef species boosts the biodiversity of a marine energy project area, the development could be a net benefit.

However, if reef species include predators that wipe out local species that have no natural defenses, then the effect could be negative. Early projects will have to be studied intensely to see how this works out.

How will migratory species respond?

A large network of marine energy devices could force migrating mammals, fish and birds to change their travel paths. Even subtle changes can throw off reproductive rhythms that evolved over millions of years. If these changes make it harder for migrating species to reproduce, or weaken them so they are more vulnerable to predators, the cost could be substantial.

Will wave-energy devices change the dynamics of shallow shorefront ecosystems?

Dozens or hundreds of marine-energy devices in a well-defined region can affect the velocity of waves striking the shore. Small changes in the depths of tidal pools or the thickness of sand layers could influence species’ ability to feed and reproduce. How will we determine an acceptable level of risk or damage in these scenarios?

Can wave energy devices pollute local waters?

Marine energy devices require lubricants that could potentially leak and cause pollution. Furthermore, the substantial corrosive nature of seawater will wear these machines down quickly, expanding the risk of pollution. Granted, most devices would not carry enough lubricants to create a substantial oil spill. But persistent small leaks spreading over months and years could still have a profound impact.

Can devices survive exposure to pollutants?

The concerns over potential pollution by marine energy devices shouldn’t obscure the possibility that offshore sites might already be polluted with chemicals that could damage these devices. Even undisturbed sites pose a challenge: Could large chemical or oil spills disable devices installed in them?

What happens to fisheries?

The livelihoods of people in the fishing industry depend on healthy ecosystems that support fisheries. Any project will have to weigh the economic, social and environmental impact on coastal industries like seafood.

How will environmental regulations affect marine energy projects?

Regulators and rule compliance will be a fact of life for the marine energy sector. Developers will need to court the regulators to figure out exactly what it takes to stay compliant. Regulators may also conduct impact assessments that discover rare endangered species, which could grind everything to a halt.

Finding the right ways to draw energy from our precious oceans

The rise of marine energy is a natural progression for PMI, which has been providing rugged, durable cable accessories to the energy-exploration industry for decades.

Though we are enthused about the possibilities of marine energy, we respect the need to tap this energy source without damaging delicate marine ecosystems. Sure, that adds extra layers of time, expense and complexity. But it’ll be worth it to keep our oceans as healthy as possible.

Companies that feel like they’ve missed the boom in offshore wind power technology may have the chance to ride a new wave of innovation with the rise of marine energy technology.

Converting the solar and kinetic power of our oceans into cheap, practical electricity seems like a far-off hope right now, but at some point the temptation to dive deep into marine energy methods and devices will prove too irresistible to pass up.

That’s something we’re watching closely here at PMI. Supplying equipment to companies that work in the oceans is what we do. Estimates suggesting the earth’s oceans could theoretically supply up to four times the world’s total electricity demand have definitely grabbed our attention.

Admittedly, it’s unlikely the oceans will ever supply all of humanity’s energy needs. But marine energy can become part of a diverse portfolio of renewables technologies like solar, wind and geothermal that serve the world’s energy needs while reducing carbon output and limiting global warming.

Looking Back on the Rise of Offshore Wind

It’s helpful to step back and look at how quickly offshore wind power became a mature technology in Europe. In 1990, there were no offshore wind farms in European waters. At the end of 2015, more than 3,000 offshore wind turbines were up and running, according to the European Wind Energy Association.

How many people could have projected that kind of growth in, say, 1980?

Obviously, nobody knows what the future holds. Marine energy is extremely expensive to develop and difficult to deploy right now. But it might not always be.

Potential Products and Devices in the Marine Energy Sector

European companies are already developing turbines and other devices to generate power from ocean tides and waves. These are big, expensive technologies that require substantial investments of time, energy and expertise. The companies working on them hope to exploit first-mover advantage and export their technologies worldwide.

As a supplier of subsea cable management systems, we see some interesting possibilities as these technologies emerge:

• Attachment points: One of the big challenges with marine energy is fixing devices to the ocean floor. Connections must be strong enough to hold energy devices in place and built to fend off the corrosion of saltwater. And they must be unobtrusive enough to have low impact on the undersea environment.
• Underwater vehicles: In an age when self-driving cars are already on the roads of Silicon Valley, it’s easy to envision rising demand for small submarines that can be put to work monitoring, repairing and maintaining marine energy devices.
• Pipe joints: One intriguing technology combines cold water from deep in the ocean and warm tropical water at the surface and creates electricity by exploiting the temperature differential. Called ocean thermal energy conversion, or OTEC, this technology requires pipes as long as several kilometers. Flexible pipe joints can help these pipes survive in ocean currents.

This list barely skims the surface of the possibilities in this sector.

Where the Marine Energy Sector is Going

Wave and tidal energy are getting the most attention right now. Costs for commercial development are still too high for this technology to become mainstream right away, but an encouraging collection of pilot projects in Canada, Europe and Australia — combined with the work of companies developing marine power devices — could lead to discoveries that can bring these costs down and encourage further development.

At PMI, we build accessories that make it easier to use cables in the ocean. Given that all marine energy devices have to transmit electricity over cables, we’re excited about the potential of marine energy.

But we also think that companies in a broad range of industries should be exploring these technologies and looking for ways to bring new products to market. If history is any guide, the people who invent the technologies that move marine energy into the mainstream stand to be forerunners of the industry.

Four intriguing technologies hold the potential to tap into the vast renewable energy of our oceans.
Nobody expects these marine energy technologies to replace coal, petroleum or natural gas in the near future. Instead, they could become assets in a diverse portfolio of technologies that can reduce our dependence on fossil fuels and temper the effects of climate change.

Let’s take a quick look at these marine energy conversion technologies.

Wave Energy

The natural up-and-down motion of ocean waves generates large volumes of kinetic energy. Wave energy devices capture this motion and convert it into electricity.

Some wave energy devices look like ocean buoys that bob up and down. Others string together a long, snake-lake chain of floating tubes. They can work close to land or farther out in the open ocean.

Wave energy is plentiful, but it’s also problematic. Waves rise and fall in multiple directions, and their velocity changes with the weather. That can make it difficult to get a reliable constant stream of energy. Also, only a few coastlines are optimal locations for wave-energy devices.

The upside is that several prototype wave energy devices are already in the water, and they’re yielding clues on how to make wave energy more practical.

Tidal Energy

Rising and falling tides generate substantial kinetic energy. The bigger the tide, the bigger the power potential. Tides rise and fall like clockwork, so tidal energy can provide a reliable stream of energy at specific times of day.

Some tidal devices look like underwater wind turbines. Because water is so much denser than air, the turbines can turn relatively slowly and still produce a worthwhile stream of electricity. Another tidal technology creates dams that capture tidal waters and uses turbines to tap the flow, much like hydroelectric plants.

Tidal energy’s impact on the subsea environment is a big unknown. Marine species may attach themselves to the devices, causing extra maintenance costs. Building tidal basins is expensive and disruptive as well. And large numbers of subsea turbines can affect the velocity of tides, which could shake up delicate undersea ecosystems.

Salinity Gradient Energy (SGE)

Salinity gradient power exploits the energy produced when saltwater comes in contact with freshwater.
The technology uses a membrane to separate saltwater from freshwater. One kind of SGE membrane generates an electrical current on its own, while another kind of SGE membrane produces pressure that can turn a turbine and generate electricity.

These membranes anchor the technology. They must be extremely large to produce abundant volumes of energy. Right now they are very expensive and prone to fouling by algae and other aquatic life, but new companies are already trying out new membrane technologies. Innovations in nanotechnology could potentially make SGE economically viable.

SGE could also work in wastewater plants to separate saline water and create electricity to help power the plant. That small-scale function could open the door to more substantial innovations that make the technology much more practical.

Ocean thermal energy conversion (OTEC)

Water at the ocean’s surface is much warmer than water in the murky depths. OTEC uses this temperature gap to produce electricity.

A complex system pumps water from up to a mile deep in the ocean. At the surface, a power station exploits the differences between hot and cold water to produce electric current. This requires no fossil fuel, and it can generate more energy than the pumping and production costs create.

This technology works best in the tropics in areas where there is at least a 36-degree F (20 degrees C) difference between surface water and deep water. It also requires massive pipes to pump the cold water up. But the energy is extremely cheap once the power plant has been built, so it’s an intriguing option in a few specific areas of the globe.

Why We Like the Potential of Marine Energy

At PMI, we have no illusions about the challenges of marine energy conversion. But we still think companies everywhere should be paying more attention to these technologies. In Europe, there’s a strong push to get 20 percent of the continent’s energy from renewable sources by 2020. That creates an incentive for a few bold pioneers to get more prototypes into the water and see how they perform.

Those incentives could create opportunities for companies that have specific expertise. PMI is just one example: We already provide some of the world’s most advanced accessories for the subsea cables that all of these technologies will need to transmit electricity to land.

Marine energy technologies will require advanced engineering to make them cost-competitive with fossil fuels. They’ll also need advanced materials designed specifically for subsea environments.

That looks like a wealth of opportunity for innovative firms that can help bring these technologies into the mainstream.

Turning our oceans into a reliable power source means putting complex devices in treacherous, ever-changing environments. The sea is much friendlier to sharks than to subsea power turbines.

PMI has been providing cable hardware for oil exploration and other subsea projects for decades, so we know only too well the challenges of putting anything in the ocean and expecting it to keep working. Salt water is extremely corrosive. Many materials are extremely vulnerable to corrosion. Subsea organisms attach themselves to devices and reduce their effectiveness. Storms create chaos.

Marine energy devices can have lots of moving parts, take up lots of space and become part of the subsea biome. These are all things marine energy companies will have to confront as they build out the marine energy sector.

Here are some of the challenges we’ve noted in our research on installing and maintaining marine energy devices.

Physical Equipment Considerations

High-strength synthetic rope termination: Steel cables that fix marine energy devices in place are extremely heavy. An attractive alternative is high-strength synthetic rope, which often has the strength of steel but substantially less weight. You don’t tie knots in this kind of rope to attach it to devices. You use termination hardware, much like the hardware PMI builds for steel cables.

Mooring lines: Wave energy devices move with the motion of waves and use technology to convert the kinetic energy in moving waves into electricity. Typically, mooring lines are fixed in place. Allowing them to move with waves creates a host of challenges.

Large-diameter pipe bending: An intriguing marine energy technology called ocean thermal energy conversion, or OTEC, requires large-diameter pipes that could be up to several kilometers long. The trouble with these pipes is they are rigid and prone to bending because of relentless movements of ocean waters. The solution is to add flexible joints to these pipes that work much like the expansion joints in bridges — giving the pipes more flexibility and extending their life.

Logistical Challenges

Small installation windows: Just as there are monsoon seasons on land, there are hurricane and typhoon seasons to deal with at sea. And even after these seasons fade, rough weather limits the time window for installing marine energy devices and fixing problems that crop up afterward.

Emergency retrieval: If a marine energy device breaks down or malfunctions in a way that presents an environmental threat, it may have to be retrieved as quickly as possible. This could require commissioning a ship and crew to retrieve the device on short notice, which can be extremely expensive.

Cable-laying methods: Cable-laying technology is mature and efficient, but it’s also extremely complex, requiring people who know how to deploy cable in ways that reduce the threats from ship anchors and submarine landslides. And the more cables get installed underwater, the more complex cable laying and maintenance becomes. Damaging an existing cable while trying to install a new one will be a persistent risk.

The rough terrain of the seabed presents another challenge. These high-energy environments have long been avoided because of the challenges they present, but now we must overcome those challenges in order to harvest the energy.

Environmental Issues

Biofouling: Algae, protozoa, and many more aquatic species attach themselves to the exterior surfaces of everything that goes underwater — anchors, ropes, pipes and marine energy devices themselves. Biofouling has to figure in any maintenance plans marine energy developers devise.

Device anchoring: Devices like tidal turbines that are installed on the ocean floor have to be anchored. Some anchors require drilling into the seabed, which can threaten delicate undersea environments. The challenge is to design and install anchors that have the lowest environmental impact while still being rugged enough to survive for decades in the ocean.

Unique and demanding terrain: Coastal topography varies widely from one continent to the next, so technology that works fine off the coast of France might be useless off the coast of Japan. This challenge holds worldwide: Tidal energy requires large tidal movements. Wave energy requires consistent wave movements. All these variables make it difficult to create technologies that can be standardized and scaled to reduce installation and maintenance costs.

What We See on the Horizon

At PMI, we already supply some of the world’s most advanced subsea cabling hardware, so our technology is poised to help address some of these challenges. Things look good to us right now, and the future looks even more promising.

As Europe pushes to get 20 percent of its energy from renewable sources by 2020, there will be social and political pressure to develop technologies like marine energy. That should create ample opportunities for companies to dip their toes in the water of marine energy technology.