LARGE SCALE WAVE ENERGY CONVERSION

LARGE SCALE WAVE ENERGY CONVERSION

It is time for Wave Energy Conversion (WEC) to be part of the sustainable energy toolbox at a utility level. Solar and wind renewable power systems are now sustainable technologies which are economically competitive with existing fossil fuel and nuclear options. Even though there have been WEC development efforts as long as there have been industrial solar and wind efforts, WEC systems simply have never made it out of the experimental starting blocks. This paper examines prior efforts and examines why they have failed at a utility level and describes the design and engineering of emerging technologies that could make large scale wave energy conversion competitive with present state of the art large scale wind and solar projects. The SurfWEC concept is introduced as a game changing approach to achieve much lower Levelized Cost of Electricity (LCOE) rates than are achievable with existing WEC approaches by enabling significant increases in kinetic energy input to various WEC designs.

KEY WORDS: Renewable Energy; Marine Renewable Energy; Wave Energy Converter; WEC; Marine Hydrokinetic; MHK; SurfWEC; Future Energy; Sustainable Energ

Energy is the central driver of human development. Human progress is directly related to the way that humans harvest, store, and use energy. In human terms, access to energy is power (Ref. 1,2). Initially humans only harvested energy through hunting and gathering. In primitive societies, humans learned to preserve and store some foods to use when there was limited fresh food available. The food preservation and storage technologies allowed humans to migrate from equatorial climates, where food is continuously available, to parts of the world where most of the food supply is dependent upon the weather in various seasons. With the discovery of fire, humans were able to extend the productive part of their day with light and heat they could control and improve their productivity by building tools from metals. Harnessing of wind allowed humans to increase their transport efficiency through sails, and the invention of steam-powered machines allowed the creation of more productive factories. At that stage, humanity began to transition from a wood to a coal-powered society. In the early 1900’s, humans started transitioning from coal to more efficient oil and gas-powered machines, and in rough terms, it can be noted that in the late 1900’s humanity started taking an interest in more sustainable energy sources for society. The demarcation lines are not all that sharp; in the mid 1900’s nuclear power arrived as a sustainable energy source and other forms of sustainable energy have existed for thousands of years in the form of sail transportation, hydro and windmill power. Wood and other biomass energy, in their purest forms, are also
ustainable power sources with recorded uses dating back tens of thousands of years. Today, in the twenty first century, there is a definitive trend to dominance of sustainable power over hydrocarbon power. It is actually quite difficult to define sustainable power, but there are two approaches to defining it. The first approach is to define sustainable power as power options and innovations that continually reduce humanity’s overall carbon dioxide and other greenhouse gas emissions. The other approach is to list technologies that are somehow recognized as sustainable power regardless of emissions or biproducts. The latter option is much more open for debate, but, for the sake of discussion, we provide a list of sustainable power technologies in Table 1. Table 1: Sustainable Power Technology Comparison This paper does not delve deeply into the comparisons of the various sustainable technologies. The references used to populate this table are provided after the text references at the end of this document. It can be claimed that everybody may have their favorites for various reasons. However, the table does provide an interesting illustration. While wind and solar are now established players in the sustainable energy basket, wave energy has not found a commercial footing. This is a shame since wave energy is available at greater magnitude than wind and solar combined (Ref. 3,4). Wind and solar both require more space to harvest energy than waves, as the average wave energy resource is capable of producing over three times more power per unit surface area of Earth than wind or solar devices, and solar has very little generation capacity during cloudy days and no generation capacity at night. The annual average availability of wind power is approximately half the availability of wave power globally (Ref. 5,6,7,8,9,10). This paper will provide some guidance as to why WEC has not yet become economically viable and will provide some suggestions to make WEC commercially viable (based on both lessons learned in the past and emerging technologies) (Ref. 11,12) based on cumulative lessons learned during WEC research and development over decades (Ref. 13,14,15,16,17,18,19,20,21) and become a component in a wind, wave, and solar sustainable energy triad. Developing a sustainable power society (reduced carbon emissions to zero carbon emissions) is more complicated than simply converting different forms of energy to power to do useful amounts of work. The large inertial force, metaphorically speaking, against the switch from a hydrocarbon-based (more accurately; fossil fuel-based) energy system to a sustainable energy system is related to the remarkable versatility of hydrocarbons as a fuel1. Hydrocarbons are inherently a form of predictably available stored energy that can be readily transported prior to use. Meanwhile, sustainable energy struggles with predictability, harvesting, storage and transport. Instead of living within a society where one energy type size fits all, to achieve sustainability, we now have to switch to a society where we have to build systems and infrastructures where energy gets delivered through a wide variety of approaches with generation, storage, and transportation of hydrogen fuels from various sustainable power sources as an emerging option. While this process will require a great deal of political will, public support, and innovation, there is a bright side to the switch to sustainable energy. At first glance, the bright side might be seen as the opportunity to save our viable climate from the ill effects of global warming, but there is actually a much brighter side to this societal change. The switch to sustainable energy is a very significant opportunity to increase the world’s standard of living and to fight the tyranny of monopolies. Control of stored energy is a form of financial power, but if energy can be harvested and stored from many sources, energy becomes social power. A well designed and versatile sustainable energy society will reduce the blackmail effect of oil rich countries and will even allow energy generation down to the individual level, thereby providing greater opportunities for freedom and energy fairness. To some extent, this is occurring today where small communities like the Orkney Islands, small villages in Africa, or even individual home owners in New Jersey are starting to set their own energy destinies. The most effective way to achieve this is to ensure that there are as many sustainable energy approaches as possible and to let them compete on a technological level. This is an entirely new approach. Today’s sustainable technologies harvest a “free” resource (sun, waves, and wind) and feed it into a community network (the electric grid) for distribution to consumers. In a system such as this, the most innovative technologies will win until another innovator shows up with a better idea. This is in sharp contrast to the last century that focused entirely on ensuring access to fossil fuels (oil and gas) by hook or by crook
Figure 1 shows that, today, land-based wind and solar harvesting approaches are starting to beat the fossil fuel energy (oil and gas) approach, but where is the wave harvesting approach? WAVE HARVESTING HISTORY Wave energy conversion research and development has been documented since the first patent filed in Paris, France in 1799 by Pierre-Simon Girard. A Martin & Ottaway survey has identified at least 28 wave energy conversion efforts where substantial expenditures have been made and numerous sea trials performed to harvest ocean waves. Table 2 provides a list of efforts. It can be argued that none of those efforts have been successful, but, in the arc of technology, that would be an incorrect statement. Flight did not happen in one try, steamship propulsion took decades to become commercially viable, and submarines were first tested in the Revolutionary War, but did not become viable until World War I. Occasionally a new technology exists for many years, but will not catch on until there is a specific use for it in warfare or commercial application. To date, it can be stated that there have been a substantial number of efforts at developing wave energy conversion, but they have not shown an ability to be commercially viable. van Hemmen AN UPDATE ON LARGE SCALE WAVE ENERGY CONVERSION 4 SMC 2019 Table 2: Historical Wave Energy Conversion projects2 For wave energy conversion, commercial viability depends on the cost to produce and install the system, maintenance costs, and on the ability to earn back the cost to produce and maintain the system by selling sufficient amounts of energy to provide a return on investment. This is basic economics, and low cost to produce the system and high sales prices for energy are a ticket to great wealth, but as long as the cost to produce is more than the ability to earn back the investment, a technology is not viable. This is the central consideration, but it assumes that the technology can actually reliably produce significant amounts of power or stored energy. Wave energy conversion has not had a successful track record of producing enough useful power or energy (i.e., in the form of electricity or pressurized fluids) to pay back the return on investment. This is fundamentally due to the slow motion of WEC devices in sea or swell wave conditions. As Table 2 shows, some efforts have simply failed to produce any energy. Indeed, some of the efforts sunk before they even 2 The authors have made a best effort to evaluate these projects based on available information. Many of these projects are poorly documented or data remains confidential. The authors would welcome technical references, corrections, and additions to improve this table. An updated “living” list of WEC projects is available by hyperlink at: https://martinottaway.com/mraftery/approaches-to-replacing-fossil-fuels-with- ocean-wave-power/. Some other related WEC projects are listed at: https://en.wikipedia.org/wiki/List_of_wave_power_projects had a chance to produce energy. This is frustrating, but is far from atypical for any new technology, especially in the challenging marine environment. In engineering development, the flip side to failure is the window to new insights. Failures like this should really be regarded as normal. Engineers deal with such failures by stating: “if it were easy, everybody would do it”. At the same time, it should also be noted that a significant portion of these efforts simply were not engineered by teams with hardcore maritime experience3 and, as such, should barely be counted as engineering development efforts. Unfortunately, another portion of WEC efforts can only be described as snake oil on the level of cold fusion or commercial ocean plastic recovery. However, there have been a number of efforts that have produced energy and show promise to reliably produce energy. In particular, Ocean Power Technologies in NJ and Bolt Sea Power show promise for small scale wave energy production. At the engineering level, it is noted that these efforts have made excellent progress in engineering sufficiently rugged components to withstand the rigors of ocean deployment. Also, the Resolute Marine Energy group has chosen to use their WEC power for desalination of seawater in areas with scarce water resources which is a value-added approach which may make their systems commercially viable in certain regions of the world. Unfortunately, while they are achieving engineering successes, the ability to be commercially viable is less attractive and this is related to a physics barrier that exists in conventional ocean wave energy conversion. These systems may be able to reliably harvest small amounts of energy, but they cannot be economically scaled to utility level power production. THE WAVE HARVESTING PHYSICAL BARRIER Wave harvesting is simply more difficult from a physics point of view than other free energy harvesting systems. This physical barrier does not exist in wind or solar where a larger windmill or more solar acreage will simply produce more energy and where stronger winds (up to a limit) and more sun will also generate more energy. Wave energy conversion is trickier because it has to deal with waves, which tend to be irregular, arrive at various frequencies from multiple directions, and the precise wave forms incident at a specific location are difficult to predict. Instead of simply capturing wind or solar energy like butterflies 3 For example, the Wavesub design, consists of a float that is moved by waves beneath the surface. Any naval architect who has designed for waves knows that wave energy below the surface results in changes in drag, while wave energy at the surface results in changes in buoyancy. Buoyancy forces are an order of magnitude more effective than drag forces, which is why maritime trade is so efficient on the surface. A surfaced Wavesub point absorber would be much more effective than a submerged Wavesub point absorber, and one is left to wonder why a massive investment is being made in a device that is inherently inefficient.

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