In our series on the patent landscapes for alternative energy sources, we’ve previously covered solar, wind, carbon capture, nuclear fusion, and geothermal. Here, we’ll be turning our attention towards marine and hydrokinetic (MHK) energy.

Currently, MHK energy comprises about 60% of renewable electricity worldwide, making it the largest source of renewable energy. Furthermore, some experts believe as much as half of the economically viable potential has not yet been realized, meaning that there’s still lots of room for the technology to develop.

However, despite the promise of MHK energy, the field’s growth has been slowing down. According to data from the International Renewable Energy Agency, investments in new hydropower fell from $26 billion in 2017 to just $8 billion in 2022 — and the numbers are expected to continue declining over the next decade.

Investing in MHK technology is not without risk, but there’s certainly high potential for reward as well. In this post, we’ll be reviewing the current state of the industry to identify where the strongest research and development opportunities might lie, and how that may inform your business’s intellectual property strategy.

What is marine and hydrokinetic energy?

Broadly, MHK energy refers to power harnessed from the natural movement of water. The key difference between these two types of energy lies in which water source is used to generate power:

  • Hydrokinetic energy: Streams and rivers
  • Marine energy: Oceans

Let’s take a closer look at what each energy type entails.

Pros and cons of hydrokinetic energy (or hydropower)

Hydrokinetic energy, or hydropower, taps into kinetic energy from the elevation difference of flowing water such as streams or rivers.

Hydropower was the first renewable energy source to be used in the United States at a large scale; in the 1940s, it supplied a third of the country’s total electrical power. Today, that number has fallen to about 6% due to investments in other energy sources, environmental concerns, and siting challenges.

The benefits of using hydropower to generate power include:

  1. Clean: Doesn’t produce greenhouse gases
  2. Efficient: About 90% of captured energy can be converted into electrical energy.
  3. Cost-effective: The levelized cost of energy (lifetime cost in relation to energy production) for hydropower is competitive with that of coal and natural gas.

However, and as mentioned above, hydropower also comes with several drawbacks which have contributed to the decline in hydropower use today:

  1. Location: Hydropower plants require large amounts of land and a consistent water supply. Moreover, the volume of the water flow and the head (change in water elevation from one point to another) determines how much kinetic energy is available to be converted into electrical power. Many wealthy nations (like the U.S.) have already built out a lot of their viable sites.
  2. Environmental impact: Dams and reservoirs can heavily  impact an existing ecosystem by altering natural features, degrading river composition, and destroying wildlife populations.
    1. As an example, Europe’s river ecosystems are under threat today due to alterations from dams and diversions.
    2. As another example, Nepal’s plans to construct hydropower plants in protected areas would set back conservation efforts.
  3. Social impact: Dams and reservoirs can adversely affect human communities by causing flooding, population displacement, and food insecurity.
    1. For example, construction of the Jatigede Dam in Indonesia caused involuntary displacement, which has disrupted citizens’ lives in the long term.

Pros and cons of marine energy (or tidal wave energy)

Marine energy, or tidal wave energy, relies on several sources of energy from the ocean:

  • The kinetic energy from ocean waves, currents, and tides
  • Energy from the ocean’s thermal gradient
  • Energy from the ocean’s salinity gradient

Worldwide production and use of marine energy is very low, with the main obstacle being cost-effectiveness. Today, there are few commercial-level tidal power plants in the world, with the largest being the Sihwa Lake Tidal Power Station in South Korea. (The United States does not even have one.)

That said, renewable ocean energy holds massive untapped potential. If maximized, it could generate up to 800 terawatt hours of energy per year — a number that exceeds the energy production in all of Canada in 2019.

The benefits of using tidal power include:

  • Clean: Doesn’t produce greenhouse gases
  • Predictable: Marine resources go through daily and seasonal cycles, and so their output is relatively dependable.
  • Abundant: Especially applicable for countries with large coasts, like the United States.

On the flip side, tidal power faces several significant challenges that have impacted industry interest in the technology:

  • Location: Tidal power plants can only be built in locations that meet specific criteria, such as fast currents or a significant difference in sea levels between high tide and low tide. As such, tidal power plants are not viable everywhere.
  • Intermittent: Tidal power plants can only produce power during tidal surges.
  • Not yet commercially viable: Construction and maintenance of tidal power plants is presently too expensive and unprofitable relative to the potential energy produced over their lifetime.

The global patent and use landscape for renewable energy technologies

If you’re identifying business opportunities in the renewable energy space, specifically MHK energy, you’ll need to understand who the current industry leaders are, as well as where the technology might even be viable.

According to the U.S. Department of Energy, these 10 companies had the most MHK patents in their portfolios as of 2021:

  1. Ocean Power Technologies (United States)
  2. Voith (Germany)
  3. General Electric (United States)
  4. Bosch (Germany)
  5. Naval Group (France)
  6. AW Energy (Finland)
  7. Seabased (Ireland)
  8. Mitsubishi Heavy (Japan)
  9. Oscilla Power (United States)
  10. Boeing (United States)

As discussed in the previous section, location has a huge impact on the viability of MHK technology — which means that the location where the technology is used will also impact patent strategy. To maximize the value of your patent portfolio, you will want to pursue an international patent strategy that gives you coverage in the countries where the technology is most used.

According to statistics from the U.S. Energy Information Administration, these 10 countries generated the most hydroelectric power in 2021:

  1. China (1274.63 BkWh)
  2. Canada (377.16 BkWh)
  3. Brazil (362.82 BkWh)
  4. United States (260.22 BkWh)
  5. Russia (214.5 BkWh)
  6. India (165.37 BkWh)
  7. Norway (144 BkWh)
  8. Japan (79.14 BkWh)
  9. Vietnam (74 BkWh)
  10. Sweden (71.09 BkWh)

If you’re in the hydropower industry, you will definitely want to consider seeking patent protection in China and Canada.

Meanwhile, data from the Canada Energy Regulator shows that these countries had the greatest installed tidal energy capacity:

  1. South Korea (511 MW)
  2. France (246 MW)
  3. United Kingdom (139 MW)
  4. Canada (40 MW)
  5. Belgium (20 MW)
  6. China (12 MW)
  7. Sweden (almost 11 MW)

So if you’re in the tidal energy field, it’s worth keeping in mind that you can reach 4 of these top 7 countries through a single patent application filed at the European Patent Office.

Marine and hydrokinetic energy: Current and patentable technology areas

There are some broad similarities in the technology used to generate both hydropower and tidal power, particularly where the technology is converting kinetic energy from the water into electrical energy.

Accomplishing this conversion typically requires the installation of a dam or “barrage” across a tidal bay or estuary; then, at certain points along the dam, gates and turbines are installed. While the specific technology will differ according to the function performed, you can seek patent protection on any element of the dam, gates, or turbines that is new and non-obvious.

Beyond these basic similarities, there are some key differences in the way hydropower and tidal power facilities operate, which we’ll review below.

Facilities using hydropower technologies

Hydropower plants can span a diverse range of sizes — from being small enough to power a single home, to being large enough to power commercial utilities.

There are three main types of hydropower facilities: impoundment, diversion, and pumped storage.

  1. Impoundment, or storage systems

The most common type of hydropower facility, impoundment facilities use dams to store water in a reservoir. When the water is released from the reservoir, it passes through turbines; the spin of the turbines activates a generator, producing electricity.

The water release can be controlled such that power is generated only as needed — for example, to meet baseload demands, to meet changing electricity needs, or simply to adjust the water level in the reservoir.

Most hydropower facilities in the United States are impoundment systems with dams and reservoirs. Prominent examples include the Hoover Dam (Nevada) and the Grand Coulee Dam (Washington).

  1. Diversion, or run-of-the-river plants

A diversion facility uses the natural elevation gradient of a flowing water body to generate power. To do this, the facility redirects part of a river through a canal or penstock. After spinning the turbines in the power plant, the water is eventually returned to its source.

Unlike impoundment facilities, diversion facilities do not use water storage facilities, and also do not require large dams to be built. As a result, constructing and maintaining diversion facilities leaves a smaller environmental and social footprint. However, it is not possible to control when a diversion facility can produce power, as that is subject to water availability and flow.

While diversion facilities have the potential to power large urban communities, they are more commonly used to meet power needs on a smaller scale. One example of this is the Tazimina project on the Tazimina River, which supplies power to the Alaskan towns of Iliamna, Newhalen, and Nondalton.

  1. Pumped storage

Pumped storage has been gaining more industry attention of late, thanks to its potential to complement intermittent renewable energy sources like wind and solar. The New York Times has reported that pumped storage may grow much more quickly than conventional dams in the immediate future.

In a pump storage system, water is pumped from a water source at lower elevation up to a storage reservoir at a higher elevation. To generate electricity, the water in the upper reservoir can be released back to the lower reservoir, through turbines.

Currently, pumped storage technology is inefficient, as it uses more electricity to pump the water upstream than it generates from releasing the stored water.

The technology may not be commercially viable yet, but it’s still attracting investors because it’s potentially more environmentally sustainable than impoundment systems. In particular, a study published in Environmental Science and Technology found that closed-loop systems (where the lower reservoir is not connected to a natural water source) could offer the greatest climate benefits.

Facilities using hydropower technologies

While the technology for tapping into tidal power is still relatively nascent, the resource itself is considered to hold incredible potential — as evidenced by a US$14.5 million funding opportunity from the U.S. Department of Energy, announced on January 16, 2024 that aims to encourage innovation in the field.

There are four main ways to harness marine energy: through currents, waves, thermal energy conversion, and the salinity gradient.

  1. Wave energy

Waves are generated by wind passing over the ocean’s surface. There are six broad technologies for tapping into the kinetic energy from wave movement:

  • Attenuators: Use the rise and fall of wave swells to create a flexing motion, which can then be converted into energy.
  • Point absorbers: Extract energy from the relative motion between a fixed structure and an object moving in response to waves.
  • Pressure differentials: Generate energy from the pressure difference between the crest and troughs of waves.
  • Oscillating water columns: Use wave movements to pressurize air in a chamber, which then powers turbines to generate electricity.
  • Overtopping: Use waves to fill a reservoir to a higher water level than the surrounding ocean; the pressure difference then powers turbines to generate electricity.
  • Oscillating wave surge converters: Devices with one end fixed to the seabed; the relative motion of the device to the fixed point (driven by waves) generates energy.

As wave energy is most concentrated at the surface (and quickly dissipates with depth), these six technologies either seek to capture energy on the surface, or use pressure differences just below the surface.

  1. Ocean current energy

Ocean currents have a relatively constant flow and this kinetic energy can be used to generate power, typically by using turbines anchored to the ocean floor or suspended from a buoy in the path of an ocean current.

The broad technologies for harnessing current energy, which operate using similar principles to wind turbines, are:

  • Axial flow turbine: Most similar to conventional wind turbines, as kinetic energy is captured by spinning blades facing the direction of flow.
  • Cross flow turbine: Kinetic energy is captured by spinning blades perpendicular to the direction of flow.
  • Oscillating hydrofoil: Use hydrofoils that translate perpendicular to the flow direction.
  • Tidal kite: A hydrodynamic wing, with a turbine attached, that “flies” in a loop in the water by leveraging flow. The movement causes the turbine to spin, generating power.
  • Archimedes screw: Generates electricity when water moves up the screw shaft, causing the device to rotate.
  • Vortex-induced vibration: When a constant flow of water meets a rounded object, an oscillating motion results; this vibration can be captured as energy.

Many of these technologies are still prototypal, but have advanced further than wave technologies.

  1. Ocean thermal energy conversion

Ocean thermal energy conversion (OTEC) uses the temperature difference between the deep cold and warmer surface of ocean waters to generate power.

OTEC has the potential to be a continuously available energy source that could supply baseload power. However, it is mainly viable in equatorial areas where the temperature difference exceeds 20°C (68°F).

OTEC systems can be:

  • Closed-cycle: Uses a working fluid with a low boiling point, like ammonia
  • Open-cycle: Uses seawater, rather than a working fluid
  • Hybrid-cycle: Flash evaporates seawater into steam, which is then used to vaporize a working fluid with a low boiling point
  1. Salinity gradient

Salinity gradient power is generated from the difference in salt concentration between saltwater and freshwater.

Currently, there are two primary methods to convert this pressure differential into energy:

  • Pressure retarded osmosis: Converts osmotic pressure to hydraulic pressure, which can then drive a turbine to produce power.
  • Reverse electrodialysis: Generates power from the controlled mixing of two water bodies with different salinities, which essentially creates a “salt battery.”

It’s possible that more techniques could be developed to harness salinity gradient power.

The importance of partnering with a qualified patent attorney for renewable energy technologies

There are certainly many untapped opportunities for innovation in the MHK energy space, particularly if we lean into MHK energy as a complement to other sources of renewable energy rather than having it serve as the baseload.

As mentioned earlier, the U.S. DoE is providing funding opportunities for projects that can increase the flexibility of MHK energy. It’s very possible that MHK energy will play a critical role in diversifying our evolving electric grid.

In addition, research and development could help encourage greater commercial uptake for MHK technologies by reducing the financial and environmental risks involved.

If you’re innovating in the complex MHK field, partnering with an industry expert is critical to ensure you have the right IP strategy to meet your business needs. The team at Henry Patent Law Firm is eager to discuss how we can help — contact us today.

Michael K. Henry, Ph.D.

Michael K. Henry, Ph.D., is a principal and the firm’s founding member. He specializes in creating comprehensive, growth-oriented IP strategies for early-stage tech companies.