Marine energy is a renewable energy resource that produces usable energy from water such as waves, tides, thermal, pressure, and salinity gradients, as well as river and ocean currents. The ocean’s resources are vast and untapped, and harnessing even a fraction of the potential marine energy available to the United States could provide millions of Americans with locally sourced, clean, and reliable energy. Additionally, marine energy provides an opportunity to transition to clean and reliable energy for remote and island communities and at-sea markets. 

To harness the ocean’s energy resources, we need novel technologies that are designed to withstand the challenges of the marine environment without causing harm to surrounding ecosystems. Engineering renewable energy systems for the ocean requires certain considerations to design devices that can hold up to constant motion in an alkaline, liquid environment filled with living organisms that colonize every available surface. Here are some frequently asked questions and resources for innovators seeking to design ocean energy technologies that can withstand operation at sea. 

Ocean Engineering Basics Video Series 

Don't Run Afoul of Biofouling

Under Pressure: Marine Energy Devices

Aversion to Corrosion

The Short Scoop on Electrical Shorts

Frequently Asked Questions (FAQs): Technical and Design 

• Q: How do I achieve waterproof electronics housings?

  A: Use appropriate O-rings and sub-sea connectors with your pressure vessel, housing, or buoy. Connectors should form a tight seal with the surface they pass through, and end caps should form a tight seal between housing bodies. Use silicone grease to lubricate all O-rings before sealing a housing, and check housing surfaces for scratches that could cause leaks.  Consider wall thickness, material strength, and shape in the design process, and always include a factor of safety by designing a system and components stronger than their maximum load. 

• Q: What types of connectors can I use? 

  A: Sub-sea connectors come in a variety of types, including bulkhead connectors and pass-through connectors. They may be dry-mate, which must be connected above water, or wet-mate, which may be connected underwater. We advise using high-quality connectors to minimize your risk of water intrusion. 

• Q: How do I prevent corrosion? 

  A: Use corrosion-resistant metals in your design, such as stainless or galvanized steel, anodized aluminum, or titanium. Additionally, use only similar metals (i.e., use a device made only of steel, rather than steel and aluminum), or isolate dissimilar metals with a non-conductive material such as plastic if they must be used. A sacrificial anode such as those made from zinc may be used, which will corrode before other metals on a device. Corrosion-resistant films and paints may also be applied, although any chemical used must be evaluated for potentially detrimental impacts to the environment.

• Q: How do I prevent biofouling? 

  A: Biofouling occurs when objects in the ocean accumulate algae, barnacles, and other organisms and organic material. Certain materials, anti-biofouling coatings, and intense UV light exposure can help prevent or slow the biological growth, but regular maintenance intervals are often required to maintain at-sea deployments. Any anti-biofouling material or coating effects on the surrounding ecosystem must be considered, and impact to the environment must be minimized. Ideal anti-biofouling measures will protect the device or system from unwanted growth without having any impact on nearby habitats.

FAQs: Marine Energy 

• Q: What is marine energy? 

  A: Marine energy is a renewable energy resource that produces usable energy from water such as waves, tides, thermal, pressure, and salinity gradients, as well as river and ocean currents. 

• Q: What do marine energy devices look like?

  A: Ocean energy devices are varied and may appear on the ocean surface, on the sea floor, or in the water column. Some tidal devices may appear similar to underwater wind turbines, and some wave energy converters may appear similar to buoys. The shape and size of the device will depend on many variables such as which resource is being harvested and which scale of power is being collected (e.g., W, kW, MW), among others.

• Q: What benefits does marine energy offer? 

  A: Marine energy has a large potential to contribute to the continental grid, with the United States’ estimated marine energy resource equivalent to 57% of all U.S. power generation in 2019. It also has the ability to power microgrids for smaller coastal communities and power non-grid activities, like desalination, ocean observing, or aquaculture. Tidal energy is more predictable than wind or solar power. Wave power tends to be strongest in the winter months, which is when solar power is lowest, making marine energy a good choice to complement existing renewable resources. 

• Q: How much electricity does a marine energy device produce? 

  A: Tidal turbines and wave energy converters can be designed to provide power over multiple orders of magnitude. The most important factors are the intensity of the resource (e.g., speed of the current or size of the waves) and size of device. Very small devices, such as those harvesting power from vortex induced vibrations, may provide milliwatts of power, and larger devices intended to power the grid can produce kilowatts to megawatts.

• Q: What environmental considerations should I know about marine energy? 

  A: When deploying marine energy technology, researchers and technology developers must be aware of ways in which marine energy devices may affect their environments. These risks, known as stressors, include potential impacts due to underwater noise, electromagnetic fields, changes in habitat and oceanographic processes, collision, entanglement, and displacement of marine mammals from their normal movements or migratory patterns. These risks are characterized in Ocean Energy System – Environmental’s (OES-Environmental’s) 2024 State of the Science Report. 

Textbooks and Handbooks

Springer Handbook of Ocean Engineering: The handbook provides a comprehensive, well-written account of research and development in ocean/maritime engineering, naval architecture, and related disciplines by leading experts in the field. It discusses the latest in ocean engineering research, including harnessing the ocean as an energy resource, coastal protection techniques, and offshore and subsea engineering automation. 

Machinery's Handbook: The Machinery's Handbook is a compiled reference work used in metalworking, design, engineering, manufacturing, and technical schools and colleges. It contains fundamentals and essentials for machining, as well as topics such as surface treatments for metals, manufacturing, symbols for drafting, and gears and gearing, among others.

Parker O-ring Handbook: O-rings are a critical part of waterproof (and air-tight) vessels because they provide a tight seal between two surfaces. This book contains extensive information about the properties of basic sealing elastomers, as well as examples of typical o-ring applications, fundamentals of static and dynamic seal design, and o-ring failure modes. 

Standards 

IEC TC 114: Marine Energy – Wave, tidal, and other water current converters. The International Electrotechnical Commission (IEC) is an international organization that publishes international standards for all electrical, electronic, and related technologies, including marine energy devices. IEC TC 114 was established in 2007 to develop international, consensus-based standards for the marine energy industry. Standards include design requirements, measurements of mechanical loads, and assessment of mooring systems, among others. 

ISO 47.020.01: General standards relating to shipbuilding and marine structures. International Organization for Standardization (ISO) standards are internationally recognized guidelines that help companies establish consistent benchmarks for products, processes, services, and systems. This webpage details many standards associated with marine structures. 

The Department of Energy’s Water Power Technologies Office supports marine energy research and development in a variety of funding and technical assistance opportunities. These include funding opportunity announcements, the Small Business Innovation Research and Small Business Technology Transfer Programs (SBIR / STTR), and via the TEAMER program (Testing Expertise and Access for Marine Energy Research), prizes, and others. A detailed list of these opportunities can be found on the Water Power Technologies Office website.