Authors: Feiyang Weng, Karl Schünemann, Paula Vibeke Münnich, March, 2025
1 Description and History
Currently, the world is facing a series of severe energy challenges. From 1990 to 2017, the share of electricity in energy demand significantly increased, with electricity accounting for about 40% of total energy use in 1990, and this figure is expected to rise to 50% by 2030. However, the world’s energy demand mainly relies on fossil fuels to be met, such as oil, natural gas, and coal 1. With the growth of energy demand, the consumption of fossil fuels is also continuously increasing. As a result, issues such as climate change, air pollution, and energy security are becoming more and more prevalent 2. Therefore, the use of renewable energy is particularly important. These resources include thermal, solar photovoltaic, biomass, wind, ocean and tidal, hydro and geothermal. Among them, ocean and tidal energy can be considered very promising forms of energy 2. Therefore, this paper will explain the economic, ecological, social and legal aspects of tidal energy.
Definition of ocean and tidal power
Ocean energy is an emerging energy source that obtains energy from the ocean through various technological means and converts it into energy used by people in daily life 3. Ocean energy has a very high potential, and it is estimated that the amount of energy that could be realized through technology could reach at least 280 TWh per year in Europe4. It is not a single energy; it is a combination of four different types of power generation that make up ocean energy. They are tidal energy, wave energy, thermal gradient energy, and salinity gradient energy. These energy sources not only have cost advantages but also possess characteristics of reliability and sustainability 5.
Tidal energy is considered to be one of the most important renewable energy sources. In simple terms, it is the energy generated by the reciprocal movement of tides, and the formation of tidal currents is mainly influenced by the gravitational effects and centrifugal forces between the Earth, the Moon, and the Sun. The interactions between these celestial bodies cause periodic fluctuations in the sea, thus forming tides. In order to utilize tidal flows for power generation, it is necessary to achieve a certain tidal range, the difference in height between high and low tides and the minimum water level difference is 5 meters 6.
Advantages and disadvantages of tidal energy
Tidal energy, as a clean and sustainable energy source, produces far fewer greenhouse gases than fossil fuels such as coal and oil. In addition, it also has the advantages of high predictability and high-power output. Unlike wind and solar energy, which cannot be accurately predicted because of the variability and uncertainty of atmospheric pressure, while tidal energy is different, the cycles of ebb and flow are easy to predict and rarely experience unexpected changes 7. High power output is due to the fact that the density of seawater is about 800 times that of air, so even if the speed of ocean currents is lower than that of the wind, it can still generate a very large energy output 6. However, tidal energy also has disadvantages. Because a tidal power plant must be installed on the shoreline, it has a limited number of locations where it can be installed. In addition, the initial construction costs and subsequent maintenance expenses of tidal energy are very high, so more technical research is needed to address this issue 8.
Technical principles of tidal energy
The methods of converting tidal energy into electrical energy are mainly divided into four types, namely tidal barrage, tidal stream, dynamic tidal power and tidal lagoons. Tidal dam power generation is a traditional method that consists mainly of a dam, a barrage and a reservoir. The barrage is equipped with several gates on which the turbines are mounted. During tidal changes, seawater flows through the gates or sluices, between the ocean and the reservoir. The movement of the water drives the turbines to rotate, which generates electricity 9.
The second is a tidal stream generator. It generates electricity in a similar way to a wind turbine. By installing underwater tidal turbines, the kinetic energy of seawater flow is converted into electrical energy. Due to the high density of water, in some specific areas such as straits, estuaries, etc., the velocity of the water is higher and the rotational speed of the turbine blades increases, which results in higher power generation from tidal power 10. However, due to the long-term exposure of the turbine to seawater, corrosion and biofouling from seawater can lead to a decrease in the rotational speed of the turbine blades, which will also affect the power generation capacity 11.
Dynamic tidal power is an innovative way of generating electricity. Tidal energy is captured by using dykes perpendicular to the coast to create a head of water. Dynamic tidal power generation does not require a reservoir or a large tidal range, but it can utilize a significant amount of tidal potential energy 12. The application of DTP is mainly concentrated in areas with medium to strong oscillating tidal currents or parallel to tidal currents 13.
Tidal lagoons are a new concept based on the relatively mature technology of tidal barrages. Through artificial dams, when tide changes occur, the head difference is used to generate electricity. At high tide, seawater flows through the turbines into the tidal lagoon, where it is partially stored. At low tide, the water in the tidal lagoon is released and flows through the turbines to the sea and generates electricity 14.
History
The history of tidal energy can be traced back as far as the Middle Ages. However, it was not used for power generation at that time, but for agriculture, using the difference in water levels between high tide and low tide to drive the mill’s wheel. Therefore, it is called a tidal mill 15. Over time, tidal power technology reached its first milestone. In 1966, the world’s first large-scale tidal power station was built in France on the River Rance, in the Brittany region 14. It can reach a peak output of 240 MW, which can meet the electricity demand of about 225,000 residents 16. Until today, the tidal power station is still in operation. After this, regions such as China, South Korea, and Canada have invested in tidal power generation. For example, the Annapolis Tidal Power Station in Canada, completed in 1984, the Jiangxia Tidal Power Station in China, started in 1985, and the Lake Sihwa Tidal Power Station in South Korea, built in 1994 14. Into the 21st century, due to the high construction cost and ecological impact of tidal dams, researchers have begun to focus on tidal stream technology, which utilizes underwater turbines to extract kinetic energy directly from tidal currents. Strangford Lough in Northern Ireland, UK, is the world’s first power station to use tidal stream technology, providing up to 10% of the UK’s energy over a period of 10 years 17. Then tidal stream energy started to become the dominant technology in the tidal field. In addition, people are still conducting research on tidal energy, exploring new tidal energy technologies, such as Dynamic tidal power and Tidal lagoons 14.
2 Economic Performance
Cost composition of tidal energy
The overall cost of tidal energy is mainly divided into two categories: capital expenditure and operational expenditure. Capital expenditure mainly refers to the costs incurred during the initial construction of tidal power stations, which include infrastructure construction, equipment purchase, and installation costs 18. In addition, there may also be costs associated with environmental assessments, as tidal energy projects may impact marine ecology. Therefore, a detailed environmental impact assessment of the project is required at the initial construction stage to obtain government approval 19. Operational expenditure usually includes daily maintenance, equipment repair and personnel management 18. The lifecycle of a tidal power station is relatively long, but there will always be an end day. So, when tidal power stations are no longer in use, they need to be scrapped and dismantled. This is also one of the costs, but the time required will be very late. It mainly includes the cost of dismantling and disposal of equipment, as well as the cost of recycling and disposal of garbage that avoids pollution to the marine environment during the demolition process 20.
Levelized cost of electricity from tidal energy
LCOE is a key indicator for measuring the economic viability of different power generation technologies. Generally speaking, the lower the LCOE, the more economically feasible the power generation method. The method to calculate LCOE is to divide the net present value of the total costs of building and operating power generation assets by the total electricity generation over the entire lifecycle 21.
Currently, tidal energy is still in the development stage, and the LCOE value is relatively high. For example, the anticipated average lifetime costs for tidal stream projects in the UK are estimated at €3.7 million for capital expenditure and €0.04 million per megawatt annually for operational expenditure 22. It is because of such huge costs that the LCOE for tidal energy is high. It is estimated that the early tidal energy LCOE range can reach $400 to $800/MWh. In contrast, in California, solar power plants cost $49/MWh, wind power plants cost $57/MWh, and combined cycle natural gas power plants cost $119/MWh 23.
However, in recent years, with technological advancements and scaled development, although the LCOE of tidal energy is still very high, there is a gradual downward trend. According to a report from the UK Offshore Renewable Energy Catapult, the LCOE of tidal energy has decreased from £300/MWh in 2018 to £178/MWh in 2022, a reduction of about 40%. It is projected that the LCOE for tidal energy could be reduced to £116/MWh and £78/MWh by 2030 and 2035 respectively. Therefore, although the LCOE of tidal energy is still not comparable to that of other renewable energy sources, it is expected that with future technology optimization and adjustment of measures, the LCOE of tidal energy will be reduced to a level similar to that of other sustainable energy sources, making it a competitive form of energy 24.
DPBT and NPV
DPBT (Discounted Payback Time) is an economic evaluation indicator used to measure the time required for a business or investment project to recover the initial invested capital through cash flows in the future. Compared to the traditional payback time (PBT), DPBT incorporates the concept of the time value of money in its calculation process, meaning that future cash flows are adjusted at a certain discount rate to reflect the change in the value of money over time 25. NPV is used here as an assessment of the profitability of a tidal energy project; generally a positive NPV indicates that the project is profitable, while a negative NPV indicates that the initial investment may not be recovered 26. According to the research by Catalano et al., the profitability of a one-megawatt tidal power plant in Italy was assessed. The results show that in the vast majority of cases, the power plant is economically viable, with a net present value of approximately €570,000. It would take about 21 years to recover the entire initial investment. If there are relevant policy supports, such as project subsidies and funding donations, the time required by DPBT will be less, taking about 11 to 15 years, and the net present value will be around €340,000 to €1,290,000. The biggest impact on the economic benefits generated is mainly due to the sales price of tidal energy and the size of the power plant. Therefore, tidal energy can generate profits, but because the current development level of technical means is not high enough, it takes a long time to recover costs. However, with government support and financial assistance, the payback period can be drastically shortened and profits can start to be earned as early as possible. In the future, the economic performance of tidal energy is full of potential 27.
Tidal energy market
The global tidal energy market is valued at around USD 1.2 billion as of 2023 and is expected to grow to USD 8.6 billion by 2033, growing at a projected Compound Annual Growth Rate (CAGR) of 21.9% over the period 2024 to 2033 28. The tidal energy market is witnessing an upward trend in terms of revenue in various regions around the world. The European market is dominant, with the tidal energy market valued at approximately $450 million in 2023, expected to grow to $1.8 billion in 10 years 29. Although there are other technological methods available, the cost of building tidal power stations is enormous and the emergence of new technologies is relatively late, tidal barrage power generation remains the main model in the market. It is economically viable as it not only has high energy density but also generates large amounts of electricity in a small area. In the future, through technological progress and policy support, the market share of tidal energy will be further expanded, which has great potential 28.
Revenues from tidal energy projects
As tidal energy technology continues to advance and commercialization accelerates, several tidal energy projects have been put into operation globally and have begun to generate considerable economic returns. A number of representative power stations have demonstrated stable generation capacity and market returns. For example, the La Rance Tidal Power Station in France, as the oldest tidal power generation facility in the world, can generate approximately 600 million kilowatt-hours of electricity each year. Since its construction, it has produced about 27.6 billion kilowatt-hours of electricity, generating revenues of up to about $4.2 billion 30. The long-term returns it brought have already recovered all the initial costs. In addition, the UK’s MeyGen tidal energy project has also achieved significant achievements. The first phase of the project generated a record 6 MW of electricity, as well as £3.2 million in revenue. The second phase increased the existing power generation capacity to 86 MW, and the company successfully reduced its annual loss to £19.4 million from £35.4 million in 2019 31. In 2022, the project reached almost £4 million in electricity sales 32. It can be seen that tidal energy has demonstrated stable power generation capacity and market returns, and with the expansion of the industry scale and the reduction of costs, the future commercialization of the application may be more extensive and generate higher income.
Future development trends of tidal energy
The future development trend of tidal energy is mainly reflected in technological breakthroughs and the continuous expansion of market scale. In the area of research, the future focus will be on tidal energy collection and power generation technologies, and research on new types of turbines and generators that can improve power generation efficiency. Although there are currently few tidal power stations and they are small in scale, they will become more widespread globally in the future, and the market share of tidal energy will continue to grow 33. In addition, there will be more relevant policies and investments to help the development of tidal energy and reduce costs 34.
3 Ecological Performance
As described above, Tidal energy can be a contributor to the electricity production in coastal regions. But when it comes to the sustainability of tidal power generators, the environmental effects play a role. This includes the building of the plant as well as running and disassembling it. As tidal power is considered a renewable energy source, the climate effect of it has to be considered to understand the impact of it.
Physical effects
Tidal and wave power generators use the energy from the natural flow of ocean water either from waves or the tides. By taking the energy from the currents of the water, the flow is changed, which can have an effect on the physical characteristics of the shoreline. It has been proven in testing locations that, especially around the power generator, the velocity of the water is changed significantly. In the area of the tidal power farm, the flow is slower while in other areas it is faster to accommodate for that 35. When compared to baseline values, a study in the Spanish Ribadeo estuary showed a change between 10 and 15% in velocity of the water flow. In addition to that, the water flow is lower behind the turbines than in front of it. This has a significant impact on coastal erosion 36.
One of the major threats that come with global climate change is the rise of the sea levels. This threatens coastal regions all over the world due to increased risk of flooding. A part of the rising sea levels is also an increase in erosion of coastal areas. To mitigate that, especially hard coastal infrastructure is being built and reinforced. This type of coastal defence is often perceived as ugly and are also being eroded by the increased number and strength of storms that are hitting coastal regions as a result of climate change. Wave farms are an alternative to that as they are mostly submerged have the ability to weaken the impact of storms and currents on coastal erosion. In a testing location in England, it has been discovered that wave farms are able to lower the erosion of beaches. Short term erosion, which occurs mostly due to storm events has been lowered by up to 30% depending on the location on the beach. In addition to that, medium-term erosion was mitigated significantly as well by the wave farms 37. The effect a wave farm has on beach erosion is dependent on the type of farm, the arrangement of it, as well as the distance to the shore. Therefore, a universal statement on the effect of tidal energy production on coastal erosion cannot be given at the moment, but it is clear that wave and tidal energy can have a positive impact on coastal erosion 38.
Effects on the marine environment
The introduction of a tidal generator not only influences the physical environment. Marine ecosystems are complex and easily influenced by a number of stressors that are connected to wave and tidal farms.
The most present effect is the physical disturbance a waver or tidal generator creates. During the installation of the generator and its infrastructure, devices have to be placed in the water or seabed. In addition to that, more ships are present during the construction than usual, disturbing the natural environment further. A similar effort has to be made when decommissioning the farm, leading to more obstruction. The physical disturbance is a problem for ecosystems especially considering the flora and fauna at the sea floor, the benthic communities, as especially when the farm is being built and dismantled the quality of the sediment is changed and benthic species are removed or disturbed. Habitats can be lost due to the construction phase, as well as during the operation, as the generator may change the flow of the currents 39. In addition to that, the construction of a farm poses risks for pelagic species such as fish and marine mammals as there is a risk of them getting hurt by swimming into either the device itself or boats used for construction, maintenance and decommissioning. Depending on the type of farm, marine animals can also get hurt by the blades of the turbine, but as most types of turbines do not rotate at high speeds this does not pose a major problem 40.
When the farm is being built in soft-bottom areas, the physical elements can have a beneficial effect as this type of environment often does not allow for a lot of immobile species that normally attach to hard substrate. The structure then offers an alternative to attach to for a number of benthic species which can benefit the whole ecosystem 41. The power plant can act similar to an artificial reef which allows a better recycling of nutrients, offers protection for juvenile species and increases the available biomass. It is unclear whether the farm increases the total biomass present or just attracts species that thereby concentrate on the surrounding area of the structure. Also, the shade from the construction can lower the growth of algae and phytoplankton, negatively affecting the ecosystem 42. The existence of a tidal or wave farm also removes energy from the currents, leading to the water being mixed less and lower turbulence. In addition to that, the transportation of species across the coast is changed when the currents are affected by the generator 41.
Next to the generator itself, a tidal or wave farm also needs to be connected to the energy grid by cables. The electricity running through the cables produces an electromagnetic fields. A number of marine species use magnetic fields for navigation for example when mating or feeding. Foreign magnetic fields such as those from cables may affect the animal’s ability to do this. Fish might be either attracted to fields or repelled by it, which affects the distribution of species in the area of the energy farm. While submarine cables are protected against emitting electric fields, they still produce a small magnetic fields. Artificial electromagnetic fields are suspected to be a contributing factor to the stranding of whales, but more research on this is necessary 41.
Another aspect of the environmental effects of wave and tidal farms is the underwater noise and vibration it emits. The construction and decommissioning of the structure lead to a lot of noise pollution under water, especially due to the fact that sound travels a lot farther through water than air. Similar to magnetic fields, a number of fishes and especially marine mammals use sound to communicate or navigate. Loud noises can therefore heavily affect the animal’s ability to do so. The sound of the construction and decommissioning can damage the hearing of species within 100m of the site 43. This also leads to species avoiding the area in the future. The effect of the noises lessens after the construction but as the operation of the farm also produces noise and vibration, it will always be a potential problem 41.
Mitigation of negative effects
While potential stressors of marine renewable energy projects exist, it is still possible to mitigate their effect on the natural environment. First, it is important to know the specific effects of a project on the local ecosystems and environment. Environmental Impact assessments are used to understand the potential damage a proposed tidal or wave farm might cause. Specific stressors to the type of generator and its arrangement have to be identified as well as the parts of the ecosystem that are potentially affected by them. Next, the impact of the stressors on the natural environment has to be predicted based on previous studies and experience. Then, the vulnerability of the parts affected needs to be evaluated and last, plans on how to mitigate the effects of the farm need to be implemented into the project plan. The mitigation measures that are determined have to either avoid or reduce the negative effects or compensate for them in a reasonable way. Potential measures are relocating the project to a different, less vulnerable, location, changing the design or method of electricity production to a less harmful one or taking a more sensitive approach to the construction 41.
Carbon emissions
The main goal of replacing the electricity production by means of fossil fuels with renewable energy sources is to save emissions of greenhouse gases. Therefore, it is important to understand if and how much carbon output is saved through the replacement. Especially relevant is this for tidal and wave energy, as the construction of the power plant is relatively complicated and has a high chance of disturbing the natural environment 44.
To understand how the carbon output of a tidal or wave farm compares, all steps during the process of constructing, maintaining and decommissioning the power plant need to be considered. The whole lifecycle of the power plant is important, but as the effort that is being made to build and dismantle it as well as the energy output is depending on the physical characteristics of the chosen location and the design of the generator, no general statement can be made 45. Another important factor is the mix of energy sources that are present in the power grid and about to be replaced by tidal and wave energy. The new power plant has to replace fossil fuels in the grid to make a significant impact 44.
During the construction of the power plant, the materials make up the largest part of the carbon footprint as the main material of marine renewable energy plants is steel. Some designs replace parts of the turbines with alternative materials such as PVC foam. But if a large foundation has to be built, steel is chosen for its durability as well as concrete. Other materials used are iron, copper and stainless steel. A proportion of the materials can be used from the recycling of other constructions. This can reduce the emissions to a certain degree. The materials used then need to be constructed into the necessary parts, transported to the desired location of the power plant and finally assembled at the site. The emissions of the transportation are dependent on the distance of the construction site to the place where the materials are being produced as well as on the distance to ports and coastline and the infrastructure that is available. The Installation of the power plant consists of drilling in the sea floor for the foundation, placing the structure and connecting the generators to the energy grid by cutting cable trenches and laying the cables themselves 44.
After the power plant is constructed, maintenance needs to be carried out to ensure that everything is working as intended. The emissions that occur through the maintenance mostly rely on the frequency and method of maintenance, as some devices only require on-site maintenance while others need to be partly removed for repairing. Carbon output of maintenance consists of the transportation, the work on or off site and the replacement parts necessary 44.
The decommissioning of the power plant needs to be considered as well to get a whole picture of the effort and carbon output necessary. While most of the devices currently used are relatively new, and have therefore not been fully replaced yet, experiences from other marine renewable energies such as offshore wind farms can be used for an assessment 45. It can be assumed that the entire system of a tidal power plant has a lifetime of around 25 years. While not all actions done when constructing the power plant have to be reversed, all structures and infrastructure have to be removed if the power plant is not replaced by another one. Materials used for the power plant might be able to be recycled, improving the carbon footprint 44.
The energy output of a tidal power plant produces no direct emissions. The output of carbon is negative when it replaces fossil fuels or other, less sustainable, sources. An advantage of tidal power over many other renewable energy is that it is reliable. Wind and photovoltaic are reliant on weather and wind as well as day and night cycles. The tides are relatively unaffected by outside influences. In addition to that, tidal power is low maintenance and requires almost no operational cost, often being treated as base-load generation comparable to a nuclear power plant. This makes tidal power an ideal replacement for traditional fossil fuel plants such as coal and gas 46. When calculating the emissions saved through a new renewable energy plant such as tidal power, it is important to look into the future. It cannot be assumed that the energy mix stays the same. Rather, it is likely that in the future the percentage of renewable energy will rise overall. This would bring down the savings of a tidal power plant relative to the energy production it replaces. A lifecycle assessment on a hypothetical location for a tidal power plant in England showed that in 2013, a newly built tidal power plant with an 10W output would emit between 34,099 and 54,914 tCO2 against a projected saving of 842,770 and 1,099,705 tCO2 when calculating with the current energy mix of that time. In a projected scenario for the future, with an energy mix that gradually turns more renewable, the projected savings are lower and make up only about a fifth of the savings with the current carbon intensity. The payback of CO2 emissions thus the point where the plant reaches a net zero emission, is calculated to be between 3.5 and 5.9 years considering different models of generators. Compared to other energy sources, tidal energy is less efficient regarding greenhouse gases on a lifecycle than other renewable energies such as wind and photovoltaics but still far more efficient than fossil fuels and nuclear energy 44.
4 Social Impact
To comprehensively examine tidal power which, being a renewable energy, is part of the concept of a sustainable developing world, it is inevitable to include not only economic and environmental aspects, but also the social perspectives on tidal power 47. However, researching social impacts is a rather new discipline within the frame of tidal power. The available scientific literature from this perspective on the topic is therefore still very limited. In the past years, multiple case studies examining social aspects regarding specific sites have been done, mostly through surveys. What is still missing is a more general theoretical understanding of social impacts on tidal power which could be concluded from the broad range of studies on specific sites 48. While there has been a rising awareness in recent case studies on tidal power projects regarding the importance of including social impacts, this perspective has not been considered in the 1970s at all. Ten years after the tidal power plant “La Rance” had been built in the North-West of France, which was completed in 1967, a report on the so far experiences was published. It only considered operating results and environmental effects, but excluded social aspects completely 49.
Meanwhile it has been understood that when planning the building of a tidal power plant it is necessary to look at the project from a social point of view in an early stage of the whole process. In doing so, possible social problems or public concerns can be taken into account in order to prevent them posing a risk to the realization of the project 50. Since multiple stakeholders are involved when it comes to tidal power, many different perspectives must be considered which can sometimes be conflicting. Important stakeholders are developers, regulators, and government agencies at state, federal, or even tribal level. Besides, specific members of the community such as people living in the area, owning properties there, or visiting temporarily, as well as people involved in fishing, marine infrastructure, and tourism can be considered equally important stakeholders 51.
The Acceptability of Tidal Power
One key aspect when researching social aspects regarding tidal power is public acceptability 51. Its importance has been understood by the tidal power industry leading to them focussing more on the communities’ opinions in order to achieve long-term goals 52. Acceptance is influenced by many different socio-political factors in the fields of culture, economy, environment, and health, which are described more detailed below. In many surveys the overall level of acceptability towards tidal power is quite high 51. Whereas the acceptance or acceptability towards a project can be reached through convincing the stakeholders simply to agree to the project, it is more complicated to also achieve their support as this also includes the stakeholders’ active participation in the process 48. Therefore, the support of projects does not often reach the level that has been expected when only considering the public acceptance of tidal energy 51.
Also, the degree of public support of tidal power in general differs from the support towards projects that are being implemented locally 52. Here, the concept of NIMBY (“Not In My Backyard”) is very notable, as some people are less convinced of tidal energy projects in their immediate neighbourhoods than they are in the general debate 50(Edwards-Jones et al., 2024). A more comprehensive explanation of why an individual changes one’s opinion on a project, in this case the implementation of a tidal power plant, when it is being realized in an area that the individual has a personal connection to can be given by the concept of place-attachment. An important factor that plays a role here is to what extent the individual’s perception of and identification with the place is compatible with the planned tidal power plant 48,51.
Other influences on acceptability are trust and justice. People tend to trust a project more when small local businesses are involved. Regarding justice it is important to stakeholders that the process of implementing the tidal power plant is conducted fairly and expenses as well as profits are distributed equally on a local and global scale 48. Multiple surveys have shown a high public acceptance towards marine renewable energies, such as tidal power 51,52. 80% of the sampled population of Nova Scotia in Canada and 82% of the interviewees of a survey in the UK showed a high level of support towards tidal power projects 52.
In order to understand why individuals from the public accept tidal power projects to a certain extent or why they do not accept them it is important to examine the attitude in regard to different possible factors. One way is to look at it from an economic perspective how much money people would invest in a project. Another option is to find out about the public’s attitudes towards tidal power 48. Several surveys on this topic have shown a large variety of factors that influence the public’s overall perception on tidal power both positively and negatively 51.
Public Knowledge
According to the information deficit model acceptance and support can increase through knowledge 51. If the public is lacking awareness of or knowledge on renewable energies, in this case tidal power, people might be less willing to accept or support the projects 52. Additionally, it makes it harder for them to participate since making decisions cannot be based on an informed opinion. Currently, the public knowledge on tidal power is rather limited 51. A survey done in the UK reveals that 58% of the people are not at all or only very limitedly informed 52. The same applies to most Washington State residents who were part of a different survey. However, there is a demand for receiving more information on tidal power by the public. Especially the topic of possible effects on the environment draws people’s interest 51.
Positive Public Views
Even though the public knowledge on tidal power is still limited, there is an overall positive perception towards the topic 52. A core aspect that supports the idea of implementing tidal power plants are environmental concerns. Individuals who are aware of climate change and the consequent need for its mitigation through renewable energies assess tidal power as a good way to do so. Thereby, less emissions are set free through energy production which also contributes to a higher standard of public health. Another positive thought on the implementation of tidal power plants is based on its possibility to produce energy independently and locally 51. According to 89% of the interviewees of a survey done in areas along the Bristol Channel in the UK, tidal energy should be continued to be developed and researched by the UK. Also, 85% believe in tidal energy having the potential of being a significant part of the country’s electricity supply 52. However, a survey from Washington State in the US shows that the public sees tidal power as an addition to other both renewable and non-renewable energies but not as a main energy source. Besides aspects regarding the protection of the environment and the idea of economic growth, the public recognizes tidal power as a contributor to the availability of local jobs 51.
Negative Public Views
Even though, as mentioned before, the public acceptance towards tidal power is quite high, there are multiple negative views regarding this topic. Thus, the concerns mostly do not lead to individuals rejecting tidal power but reveal the view of the public on tidal power more differentiated. Although environmental concerns can lead to a positive perception of tidal power, they raise negative views on it as well 51. Respondents of a survey in the UK perceive the impact on their local environment as the most important aspect when discussing the implementation of tidal power plants 52, for instance, how marine life is being affected by it. Multiple surveys show public concerns regarding marine life, such as migrating salmon, other fish, and sea mammals, being endangered by the turbines. Even though there is still a lack of information on the impact of tidal turbines on marine life, it is known that there are possible harms. Another negative public view is the impact on fisheries. Depending on the location this issue can also involve the violation of tribal fishing rights, like a survey from Washington State in the US reveals. Also, there is an uncertainty on how cost-effective tidal energy is. The development and maintenance are quite expensive, and the generated energy could rise the electricity bills which is a problem especially to people with a lower income 51. Still, according to a survey from the UK, this aspect is seen as less relevant by the public than other topics 52. Besides, there are public concerns regarding the technology of the tidal power plants. Technical issues can pose a risk to the public’s safety, for instance when communication cables running under the sea get damaged through the turbines 51.
Additional Social Impacts
There are other positive social impacts of tidal power that have not been covered or barely touched by the public in the context of the surveys. For instance, the possibility for local economic growth in rural areas has not been given a lot of attention as well as job creation 52. To give an example, the previously mentioned tidal power project in them Bristol Channel led to the creation of 2,000 temporary jobs and 80 long-term jobs. Besides, touristic social impacts have not been considered by the public. Looking at the tidal power plant “La Rance” in France it becomes clear that with yearly 70,000 tourists visiting the site the touristic value of tidal power should not be underestimated 53. Also, a higher level of public health as a consequence of decreased anthropogenic emissions through the implementation of tidal power, is an important factor that did not get as much attention by the public than it would have deserved considering its severity. The third Sustainable Development Goal (SDG 3) sets targets for the year 2030 regarding “Good Health and Well-Being”. Target 3.9 of the SDG 3 focusses on the decline of deaths and illnesses caused by pollution. Since yearly 6.7 million deaths have been influenced by air pollution, the usage of tidal power to produce energy would avoid millions of deaths 47.
Regarding negative social impacts, there are only a few additions to the aspects that have been listed by the public. It has been mentioned that tribal fishing rights might be violated 51. This issue can be looked at on a larger scale, as inequity is being observed everywhere where people who traditionally live off the ocean get restricted by new stakeholders, such as the tidal energy sector without being indemnified for it. The profits through the implementation of tidal power are often experienced by others while the livelihoods of these traditional stakeholders can be endangered. So far, this issue has not received enough attention in the literature. Thus, a policy change is necessary for a more equitable tidal energy development 48.
5 Political and Legal Aspects
The inclusion of tidal power into the energy grid is influenced by a number of policies and rights 54, since many stakeholders with different backgrounds are involved in the whole process. These regulations pose on the one hand a legal obstacle to the implementation of tidal power plants as they comprise multiple restrictions. On the other hand, policies and rights can enhance the usage of tidal energy by setting objectives which can be achieved through tidal power 48. Also, the three pillars of sustainability comprising economic, environmental, and social need to be taken into account sufficiently. Covering all three sectors is of high importance to act sustainable but it also leads to additional difficulties 54. Regarding the authorisation of energy generation, the United Nations of the Sea Convention (LOSC) defines the rights within which coastal states can act in offshore areas whereas in the Exclusive Economic Zone (EEZ) coastal states are allowed to govern the energy generation from marine renewable energies 55.
International Policies on the Environment
The importance of marine renewable energies, such as tidal power, has been particularly shaped when in 1992, 154 nations signed the United Nations Framework Convention on Climate Change (UNFCCC) with the goal of lowering the rate of temperature rise and reducing emissions 55. Through the implementation of the Kyoto Protocol these targets became binding to developed countries in 1997 56. Even though the UNFCCC does not refer to ocean energy, it is an appropriate way to reduce emissions in order to achieve the aims. Regarding other environmental impacts the United Nations Convention on Biological Diversity (CBD) was signed in 1992, too. The CBD emphasises the general importance of considering environmental impacts when realising projects and points out that it is the states’ responsibility to assure necessary measures for environmental protection being undertaken. This also applies for the building of tidal power plants. Thus, whereas the UNFCCC’s aims enhance the building of tidal power plants, the CBD demonstrates issues that need to be solved in order to act sustainably 55.
Another convention that has set up policies in favour of the environment and thereby influenced the implementation of marine renewable energies is the OSPAR Convention which has been signed by 15 European nations and came into effect in 1998. In addition to its original approach of counteracting pollution it was extended to other fields of human impacts on the maritime environment as well. For instance, it comprises the preservation of biodiversity which poses a challenge to tidal power and the limitation of emissions which enhances the shift to renewable energies. In 2010 the International Council for the Exploration of the Sea (ICES) mentioned further impacts of tidal power on the marine environment, such as underwater sound pollution caused by generation devices. Hence, these impacts have now been incorporated in the Marine Strategy Framework Directive by the European Commission 55.
Also, the Paris Agreement which has been implemented in 2016 is an underlying cause for the increased diffusion of renewable energies. To reach its goal of not exceeding a global warming of 2 °C carbon emissions need to be lowered drastically by the 187 countries that have signed the agreement 57.
Policies in the EU
The EU has implemented many directives on counteracting climate change and supporting renewable energies. In this regard, binding policies assure that the EU member states follow the regulations. For instance, in 2010, the Renewable Energy Directive (2009/28/EC) decided that every state had to present their National Renewable Energy Action Plan to the European Commission. The plans must be reached by 2020 and include for instance to run at least 10 % of the states’ transportation on renewable energies 57. It is noticeable that only seven out of 23 coastal states in the EU considered tidal power in their Renewable Energy Action Plan 55.
In the context of the Paris Agreement, the EU has presented their plan of reducing greenhouse gas emissions by 40% until 2030 compared to 1990 and to be carbon neutral by 2050. Thus, the EU plans to change their energy system towards efficient and affordable renewable energies and thereby become the world leader within this field. Therefore, the part of the energy system covered by renewable energies is to be raised by 32% until 2030 and by 80% until 2050 within the EU 57.
Beside energy policies, marine spatial planning policies have an impact on the implementation of tidal power. In 2007, the EU’s Integrated Maritime Policy passed in order to save marine environments. In this context the Maritime Spatial Planning Directive 2014/89/EU took effect. It focusses among others on interactions between maritime stakeholders, policies regarding activities in the sea, economic and environmental aspects as well as considering the impact of marine renewable energies on its surroundings in marine spatial plans. Besides, the Marine Strategy Framework Directive 2008/56/EC’s goal is to achieve a good environmental status of European marine waters and the Water Framework Directive 2000/60/EC’s goal is to achieve a good environmental status of transitional coastal waters. Both frameworks result in additional needed considerations regarding the environment when tidal power is implemented 57.
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