Alejandro Moreno, Director of Water Power Technologies Office of Energy Efficiency and Renewable Energy of the U.S. Department of Energy, recently led a seminar at MITEI on the economic advantages of using marine energy technologies. Here, he explains the unique methods that marine energy employs, the challenges it faces, and the importance of policy in shaping research and innovation.
What are some of the ways marine energy can be harvested using innovative technologies?
The ocean, long used as a source of food and water, is increasingly being viewed as a source of clean energy as well. Marine energy is a class of renewable energy technologies that extract and convert the energy contained in the marine environment into useful mechanical or electrical energy, to pump water or power a grid, for example. Energy can be harvested from waves, tides, ocean currents, or even from thermal and salinity gradients.
Collectively across all these different marine energy resources there exist hundreds of unique designs that seek to harness the energy contained therein. For wave energy, there are seven generic device types that use everything from reciprocating buoy pistons and flexing barges to oscillating underwater flaps or compressed air driven turbines. Similarly, tidal, ocean current, and river (collectively referred to as current) devices have a number of generic designs that are reminiscent of the wind industry: horizontal and vertical axis turbines, augers or Archimedes’ screws, and flapping hydrofoils as examples.
At present there is no one design for each resource type that has risen to the top of the pack in terms of cost, performance, and reliability, but as the industry matures, we expect to see convergence on a smaller number of technologies similar to what occurred in the wind industry with horizontal axis turbines.
What are some challenges in developing technology for ocean environments?
Working in the ocean is hard. Very hard. The technical and design challenges are numerous. For starters, engineers must devise ways to protect their systems from corrosion, foundation scouring, biological growth, and extreme events such as the hundred-year storm. Marine energy systems are constantly under attack from the environment as soon as they enter the water, but the expectation is for them to last years, or decades while providing reliable energy.
Simply getting devices into the water can take considerable effort. There are numerous permitting and regulatory bodies that need to review engineering designs, environmental impacts, and hazards to navigation before any device can go in state or federal waters. Extrapolate this process out over multiple iterations as designs are modified and improved and it results in long engineering design cycles which acts as a brake on technology development.
Just like in real estate, location matters greatly for marine energy developers. In the case of wave energy converters, systems need to be tuned to the waves (better known as achieving resonance) that are most common for the area to maximize energy capture. For tidal or ocean current systems, the current flows from which the energy will be extracted can vary considerably over distances as small as a couple meters in any direction. In both cases these site-specific characteristics influence the design and its power production.
There are always non-technical challenges as well. Before deploying any new technology, developers need to spend time understanding the needs and concerns of local communities and towns, and this is best done by building trusting relationships. Then there are always the traditional challenges that any new technologies face such as displacing incumbent technologies, competing on cost, and attracting investment.
Designing, building, and deploying devices to efficiently extract energy from ocean waves, tides, or currents is not easy, but the upside is huge if done right.
How can marine technology complement other low-carbon energy technologies?
Marine energy is a unique resource. In comparison to other renewable energy sources like solar photovoltaic and wind, waves and currents are much more energy dense. As an example, due to the density difference between seawater and air, a two-knot water current can pack as much energy as a 34-knot gale. In practical terms, this means that more energy can be extracted from a given footprint helping coastal areas with limited land area available for renewable energy development. Marine energy is both reliable and forecastable; in the case of tidal or ocean currents, they are predictable years in advance. This predictability lends itself to appropriately sized storage systems and researchers are currently investigating how tidal and storage could provide baseload power.
Marine energy can also pair with other renewables. Wave energy and tidal energy are uncorrelated to onshore wind energy generation profiles, and also less variable. The tides, currents, and waves are not constrained by the time of day, unlike solar photovoltaics whose generation is limited to daylight hours only. These features mean that marine energy can complement other renewable energy technologies to create a steady supply of clean energy on both a daily and seasonal timescale.
For some applications existing energy technologies are not sufficient. In fact, we’ve identified many such applications in the maritime industry, which has led us to consider the broader applications of marine energy outside of powering the grid. Many of these applications fall within the sectors of the rapidly growing “blue economy”—such as aquaculture, ocean observing, maritime defense, or even commercial shipping. In each case, the existing methods of power generation are limiting factors. For example, underwater vehicles used for subsea inspections are mission limited by the capacity of their batteries, requiring recovery and recharge before going back out on mission. A persistent underwater vehicle capability, without the need for frequent recovery, requires a consistent energy supply and marine energy is well suited to meet this need.
How can public policy support innovations in marine energy?
Many marine energy technologies, especially those pursuing non-grid applications, are still early-stage or pre-commercial with R&D needs that cut across the jurisdiction of multiple public sector agencies. Because of this, blue economy technology advancement presents opportunities for coordination and collaboration at multiple levels: within and between government agencies; among government agencies, research institutions, and the private sector; and between established companies and entrepreneurs developing integrated systems designed to function in the ocean environment. As an emerging technology, public policy can have a huge impact on its successful maturation into a flourishing industry. There are several ways through which to accomplish this.
The first is through funding of research. Through competitive grants and other funding mechanisms, our office invests in early-stage technologies to drive down costs, increase performance, and generally de-risk the technologies to attract investors. Second, is building relationships and partnerships. As mentioned above, by working not only across the federal government, but also with universities, research centers, industry, and governments both foreign and domestic we develop strong relationships through which we can coordinate research initiatives to solve common problems. The result is less duplication of effort and better sharing of data and information. Third, public policy can help streamline processes such as permitting or licensing. Often times permitting of new technologies is confusing for both regulators and developers, but by working with other agencies we can help educate both parties on the key issues and help devices get permitted faster.
Perhaps most importantly, policy creates a vision. For example, this past November a subcommittee of the National Science & Technology Council released the report, Science and Technology for America’s Oceans: A Decadal Vision. This vision helps agencies develop goals and strategies that, for example, will promote economic prosperity and better understand ocean systems. This has helped groups like the National Oceanic and Atmospheric Agency (NOAA) in shaping their new strategy for the blue economy as announced this past year by Rear Admiral Timothy Gallaudet, the Assistant Secretary of Commerce for Oceans and Atmosphere for the U.S. Department of Commerce. For our part, we’ll continue to work together with other agencies and organizations to not only spur energy innovation but also help grow a sustainable blue economy.
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