This document provides an overview of clean tidal power technologies, including their economics and environmental effects. It discusses two main tidal power methods - barrage systems that utilize tidal differences to power turbines, and tidal stream technologies that extract kinetic energy from moving water. While tidal power is renewable and predictable, its major drawbacks are high upfront costs to build infrastructure and potential negative environmental impacts. Barrage systems in particular can disrupt tidal flows and harm marine life. However, the document notes tidal power's competitiveness on cost once built, and that environmental effects are site-specific. It concludes that further turbine design advances could help lower costs and minimize impacts of tidal stream technologies.

1. Clean technology
Practical exercise
Tidal power
By: Gołębiowska Katarzyna
Havran Iva
Herzallah A M. Mohammed
Supervision: Dr. Thomas Schaubroeck
2014- 2015

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Tableof Contents
1. Introduction.................................................................................................................................3
2. Sustainability assessment: economics & environmental effects, improvements ................................4
2.1. Economics ...........................................................................................................................4
2.2. Environmental effects ...........................................................................................................5
2.3. Improvements, future prospective..........................................................................................5
3. Case studies and SWOT analysis ..................................................................................................6
3.1. Tidal power in Palestine and Serbia ......................................................................................6
3.2. Tidal power in Poland ..........................................................................................................6
4. Conclusions.................................................................................................................................7
5. References...................................................................................................................................8

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1. Introduction
Tidal energy exists as a result of the motion in the Earth-Moon system (1). The basic principle of the tidal
power utilization technology is to alter the tidal potential and kinetic energy into an applicable power
energy supply source (2). Research and developments in this emerging field have led to the design of
several types of devices to capture this energy for a purposes of generating electricity, thus there are
plenty of ways to harvest the tidal energy now days, but the most common types are the barrage systems
the tidal stream technology.
The key of tidal power technologies lays in the barrage system as the pioneer in tidal energy utilization.
Barrage or dam typically works as a converter of potential tidal energy into electricity by forcing the water
through the turbines, triggering a generator. The basic components of the system are a barrage, turbines,
sluice gates and slip locks, all put together in the embarked system on the coastline (3). When the tides
have sufficient difference in levels on two opposite side of the barrage, the gates open. The water is then
pushed through the turbines that, with an assistance of a generator, generate the electricity.
Tidal stream technology is rather new technology that utilizes the turbines for extracting the kinetic energy
from the moving water to generate electricity. Tidal current technology more or less is similar to wind
energy technology (4). However there are several differences in the operating conditions. Under similar
conditions water is 832 times denser than air and the flow of water speeds up generally much smaller (5).
Furthermore, tidal current turbines operate submerged in the water, thus they experience higher forces and
moments than the wind turbines. The tidal stream technologies are more efficient when they are installed
in the fast flowing water with high tidal movements.
As any power technology existing in the world, the tidal power application has its advantages and
disadvantages.
The advantages of tidal energy lay in the fact that it is:
- renewable and durable source of energy considering the size of the oceans
- predictable energy source compared with the other renewables and it is not influenced by the
climate change, since it only depends on the Earth and the Moon relation (3)
- pollution free not like some conventional energy sources
- more efficient than wind technology due to the density of water effect
- helpful in controlling the impacts on a coastline against damage from high storm tides
The disadvantages are:
- it is presently costly to build and maintain
- it has negative environmental affects
Still there are not any large scale applications of tidal stream energy. Back to a DTI (Department of Trade
and Industry) report, the World's appropriate tidal stream resources are estimated to be around the power
of 90GW, on behalf of 3% of the total tidal stream energy in total. The best sites are found to be in Korea,
the UK and North America. In the UK there is a potential for up to 16GW tidal stream energy, which
would reach a 15% of the total UK's electricity generated (6).

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For utilizing the tidal power technology, sustainability assessment should be taken into account, in order
to be aware of all the benefits and drawback that it brings.
2. Sustainability assessment: economics & environmental effects,
improvements
As it is mentioned before, tidal energy is more predictable and reliable than other renewable energy
sources and as such, has a large potential as an innovative clean technology for generation of electricity.
However, beside all the advantages, there are some drawbacks that need to be considered in order to have
a whole picture of tidal power applicability.
Two main disadvantages of tidal power utilization are high investment costs and significant environmental
impact to the surroundings.
2.1. Economics
Construction of tidal barrage systems requires large capital investments and long construction time and
that is why these systems are not further developing (7). The major costs come from the utilization of
large quantities of material for building the system that is able to resist the huge volumes of dammed
water. Climate and geographical characteristics in situ can play a significant role. Powerful winds and
waves can influence the price of dykes that need to be built strong enough to be able to resist them (8).
However, these costs are partly compensated by the fact that, once built, power plants can last more than
100 years with the same barrage structure, and the same equipment for 40 years. Also, the operating costs
are not high.
With only four tidal barrage plants running around the globe, estimation of costs remains a challenge.
According to the researcher Eleanor Denny, the initial costs should be less than €530,000 per Megawatt
for the plant to be cost-effective, which is currently unreachable target, implying that, at the moment, this
industry is unprofitable (8). On the other hand, durability of these plants and rather low operation costs
make them competitive with other types of power generation facilities. It is estimated that maintenance
and operational costs stand for less than 0.5% of initial investments. La Rance, power plant in France with
initial costs estimated to be around $66 million, can serve as an example which shows that, even with high
opening investments, the money can be reclaimed due to long operating time (45 years).
For tidal current installations, innovative way of tidal power utilization, it is even more difficult to
estimate the costs. There are only few pilot scale power plants of this kind operating in the world. For
guidance only, Canadian Race Rock site with the single turbine that generates 65 Kilowatts of energy cost
$4,000,000. The first commercialized current turbine generator in the world, SeaGen in Ireland, generator
of 1, 2 Megawatts with a pair of turbines, initially cost around $11 million USD.
When the money that consumer has to pay is in question, tidal plants are highly competitive on the
market. For comparison, La Rance plant with 240 Megawatts generator generates the electricity at 3, 7
eurocents per kWh that is much more compiling than the price of 10, 8 eurocents per kWh coming from
conventional plant in the area. Furthermore, the price is more than compatible with 3, 8 eurocents charged

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by the Nuclear power in France. With the price of 3, 2 eurocents, hydroelectric plants is the only more
efficient power generation facility in France.
However, according to the BC Sustainable Energy Association (BCSEA), further developments in turbine
design and tidal technology in general, could lead to the price reduction to the range of 5-7
eurocents/kWh, the price that proves the great potential of tidal power as a sustainable energy solution in
years to come.
2.2. Environmental effects
Up to now, there are only few studies assessing the environmental impacts of tidal barrages systems. They
are site specific, and due to the lack of available studies, the impacts are difficult to compare. But in
general, it is known that a dam can disrupt tidal current flows and negatively affect flora and fauna of the
marine ecosystem (7). Water turbidity could also be affected due to the change of sedimentation
movements. Fish and marine mammals can suffer from the turbines and barrage by the direct contact with
them, while trying to pass to the other side. According to the studies, in Annapolis estuary, mortality of
fish during the turbine passage ranges between 20-80% depending on the species (8). Also, the intertidal
area can be declined as a result of lowered tidal range caused by the barrage, which can impact the coastal
life. The most affected are the birds that feed on this intertidal zone and by this disruption, they can starve
or migrate to some other ecosystem and disturb the balance between the species.
The tidal current turbines, as a rather new technology, do not have enough facts based environmental risk
assessments, but only those based on speculations, modeling and laboratory work. However, they are
believed to be much safer for the environment then their barrage predecessors. With turbines with low
rotations pace and screens located in front of them, they do not present a high risk for wounding the
species in the close surroundings (8). As the system is developed to harvest only small fragment of the
total tidal flow, the impact is minimized with optimal number of turbines.
On the contrary, the tidal fences systems with the big number of connected turbines, represent a
concerning issue. Land and water infrastructures for expanded activity can endanger sea species and birds.
They change the tidal flow, and, as it is a case with the barrage systems, they can decrease the space for
birds to feed on and disrupt the tide speed which result in decelerated sediment movements and shore
erosion. In addition, one laboratory test showed that sound linked with the turbines shifts the water
pressure, hence, harms fish tissue.
2.3. Improvements, future prospective
Tidal power, as a source of energy that is predictable and steady, has the advantage over the other types of
renewables. With further development of this technology, both cost of the process and the impact on the
environment can be reduced. This would make it more efficient and safer option for power generation,
than, for example, nuclear or hydroelectric plants, which malfunctions could have cataclysmic
consequences to the environment.

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3. Case studies and SWOT analysis
3.1. Tidal power in Palestine and Serbia
In the case of Palestine, the reasons for no application of Tidal power technology are the following:
- as known, Palestine is located on the Mediterranean Sea and far from the ocean, thus, it means it has
low potential for tidal harvest
- it is not economically feasible since the technology is expensive
- the political issues and the fact that Palestine does not have international borders recognition
- the conditions of the shore are not appropriate enough in the sense of technology application (no
caves or a natural water reservoirs to control the discharge of water)
Republic of Serbia does not have the access to the sea and as such it does not have any potential for tidal
power utilization. For the reasons above in this report we will discuss tidal potential in Poland.
3.2. Tidal power in Poland
The study case of Poland shows that at the moment, tidal power is not priority among other renewable
resources available. However, the legislation demands that the tidal power, as a part of hydropower in
Poland, should be raised up to 10% of total energy source in the near future (9).
Below we list the strengths, weaknesses, opportunities and threats of tidal energy utilization in Poland in
the future.
STRENGHTS
- financial support from EU
- quota system based on auctions or tradable green certificates
- increasing level of pollution forces to find alternative ways of providing energy
- growing capacity of renewable energy sources from 1028 MW in 2004 to 6000MW in 2014 (now
mainly from wind, biogas and biomass power) but it indicates some potential for other type of sources
WEAKNESSES
- coal traditions of generating power (actual situation: 90% of energy is produced from hard and brown
coal and 10% from renewable sources) reduces the possibility to take advantage of renewable sources
- lack of public acceptance for relatively high costs of application of the tidal energy
- small experience in using renewable energy
- problems with infrastructure and distribution of power sources (mainly integrating renewables to the
power system; hard to connect new generation units)
- engagement in environment protection (strong pressure from the environmental movements)

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OPPORTUNITIES
- access to the Baltic sea
- potential interest of investors (provided that some conditions are satisfied such as change of
environmental policy and more financial support)
- implementation of the Act on renewable energy sources, which refers to the providing energy
strategy until 2020, as a further plan for supporting renewable power utilization
THREATS
- unstable political situation (key role of relations with Russia – main gas provider)
- no long-term vision on energy policy puts investors off
- not clear environmental legislation
- high costs of technology (limited utilization hydro power to units below 1 MW)
To summarise, for now, tidal power is not the main interest in Poland among other renewable sources such
as wind, biogas and biomass. However, some future potential can be observed as the renewable energy is
increasing and becoming more efficient. According to the newest energy plan in Poland, hydro power has
utilization of 10% in total. It is not much, but taking into consideration some changes in the energy policy,
it can increase in the future. There is also increasing external support for turning from conventional to
renewable power such as green certificates related to quota system which stimulates investments.
Essential threats of the tidal energy utilisation are a low social acceptance, relatively high costs,
environmental effects and currently little interest from the investors. In addition, the political situation is
not stable because of relations with Russia - key gas provider.
4. Conclusions
Tidal energy is the type of green energy which is rather predictable and reliable. Every day development
of the technology makes it more applicable because it reduces its expenses thus it becomes more available.
The case of France shows that this technology currently is only less efficient than hydro power energy
utilization, which means that, in the recent future, tidal power technology has potential to become the
leading renewable energy source. In Poland, tidal power is expected to reach 10% of renewable energy
utilization till 2020 but from today’s perspective there are many challenges to overcome and the lack of
financial support is one of the major limitation. From the environmental point of view, tidal energy could
have negative effects on the surroundings. However, due to developments of technology, it is getting safer
every day. The problem lays in the fact that, because the tidal power utilization is relatively new
technology, there is still not enough research conducted in this field to give full view of the threats. For
this reason, there is a need for more studies that would increase the understanding of the impacts of this
technology to the environment. Also, it could affect the social attitude towards tidal power utilisation and
help to remove the scepticism among the societies of the countries that are planning to apply this
technology in the future.

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5. References
(1) Wenshi Ch. Tidal Energy 201. Course for Physics 240, Stanford University 2010.
(http://large.stanford.edu/courses/2010/ph240/chenw1/ )
(2) Block E. Tidal power: an update. Renewable Energy Focus 2008; 9(6):58-61.
(3) http://www.exergy.se/goran/hig/ses/06/tidal.pdf
(4) Rourke FO, Boyle F, Reynolds A. Renewable energy resources and technologies applicable to
Ireland. Renewable and Sustainable Energy Rev 2009; 13(8):1975–84.
(5) Bryden IG, Grinsted T, Melville GT. Assessing the potential of a simple tidal channel to deliver
useful energy. Applied Ocean Research 2004; 26(5):198–204.
(6) Green Rhino Energy forum. Tidal Stream Energy 2011. http://www.greenrhinoenergy.com/
(7) Rourke FO, Boyle F, Reynolds A. Tidal energy update 2009. Applied Energy 87 2009; 398–409.
(8) Helston Ch. Tidal. EnergyBC 2014. http://www.energybc.ca/profiles/tidal.html#teconomics
(9) Paska J, Surma T. Electricity generation from renewable energy sources in Poland. Renewable
Energy 71 2014; 286-294.