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The Relationship Between Human Beings and the Nature
June 28, 2007 02:45 AM PDT


What makes human beings distinguish from the other beings on earth is the fact that they have always placed supreme objectives. The basic factor for Man’s constant evolution and progress has always been the Natural Environment and his relationship to it. This relationship, however, has gone through a lot of stages and fluctuations.

The “Stone-Age Man”, who is primitive and his only goal is to satisfy his survival instinct, is being “under the control of Nature”. His survival methods include hunting and collecting food. Human beings do not intervene in the evolution of natural elements; on the contrary, they feel an intense awe and a fear towards Nature.

During the second stage of the Man-to-Nature relationship, the “Bronze-Age Man” finds himself co-existing “with the nature”. Human beings have become equal to it. They do not exploit Nature, they simply use it in a “friendly'' way in order to improve their life. Therefore, the first forms of rural life started coming up and lasted up to the Industrial Revolution. In this phase, elements of nature are exalted to the skies and the first forms of religious worship are developed. In our country, Greece in particular, during Ancient times, people worshipped not only Nature itself but also the Gods who had the power to control the greatness of Nature. We mean, of course, the Twelve Gods of Ancient Greece, who were known to control the birth and death of every little thing on earth.

To conclude, we reach the present phase. The “Hydrocarbon-Age Man” finds himself “above Nature”. Human beings have tried to escape from all natural bonds which might have prevented, to their mind, their evolution.
Modernity wishes to kill the biological gods of Nature and destroy animist beliefs (the notion that each part of the global ecosystem has a soul and is therefore value in itself). Modernity considers progress to be the only god to which people, communities and ecosystems may be sacrificed. However, this attitude has resulted in their extended intervention in the ecological balance. People have overcome Nature (its restrictions and limits) with considerable and rather dangerous consequences. The improved quality of life, which was their objective, is currently being placed in horrible danger.

Now that an ecological destruction is imminent, we, the Earth’s habitants have to comprehend all our faults and realise the unison we have with Nature. From now on, we have to realize that we are not only the “consumers'' of Nature but we have to become the “Re-creators” of Nature.

Fotini Diakopoulou,
Teacher of the English Language and Literature,
2nd Professional Lyceum,
Kallithea, Athens

The Offers of Nature to Humanity
June 28, 2007 02:43 AM PDT


The relation of human beings with the nature has always been dialectic and friendly by origin. Nature has helped people upgrade their quality of life, providing not only material but also moral and intellectual benefits to them. First of all, the nature constitutes a source of life, since people are given birth and live within it. It ensures them material goods, food, raw materials and everything essential for their survival. Furthermore, energy coming from the sun, the wind and the waterfalls gave people the possibility to activate themselves and evolve into the self-sufficient beings of the 21st century. In conclusion, Nature ensures their mental and physical health.

However, apart from determining the biological evolution of human beings, Nature has constituted a source of inspiration, artistic creation and intellectual reflection. The harmony of nature, the composition of colours, the alternation of seasons caused awe to people mainly in the past. The classic arts, the lyrical element, the bucolic poetry of Ancient Greece highlight the respect people felt towards nature and their need to express it. Nature elevates human emotions, calms down mental disturbance and smoothes the person’s mental outlook. In addition, Nature influences people intellectually. It intrigues their intrusive spirit and arouses their wish to learn the attributes and the forces of Nature. Moreover, it offered as a basis for the growth of Natural Sciences and Technology. Besides, it led also to the growth of Philosophical Reflection. The perfect causality of the natural world, the order and the organisation of nature, the circle of birth and death, genesis and deterioration prompted the person in the search and the interpretation of truth. Existential problems, which were mainly expressed by Natural Philosophers, became the stimulus for seeking the way Nature operates. The greatness of creation amazed human beings. Whatever could not be approached via the logic inspired awe to people and they exalted it to the skies. The harmony of nature stimulated the religious sentiment.

Unfortunately, however, the human arrogance, which was caused by scientific developments, is owed to the human pervasion in nature, both its microcosm and macrocosm. In our time, people have utilized, exploited, sacrificed and even discarded anything that exists in the natural environment to their profit. Nature still has a lot to offer to us but it is probably about to take its revenge on us. The aim of our environmental project “Green Planet, Perfect Planet” is to make other people aware of the current condition of our planet and persuade them to make just a little effort to save it from destruction and make it a better place.

The Students of the 1st Class,
2nd Professional Lyceum, Sivitanidios, Kallithea

The Consequences of The Destruction of the Natural Environment
June 28, 2007 02:42 AM PDT


Human evolution and progress has unequivocally caused immense problems to nature and what constitutes it. The consequences of the destruction of the natural environment have touched upon the human beings themselves, the balance and the quality of their life.

Unfortunately, the air we breathe threatens our respiratory system because it is polluted by the emissions of cars and factory fumes. The water (rivers, lakes and seawater) which is contaminated by industrial waste, sewage and waste coming from the ships, including oil slicks, has lost its generating quality and thousands of fish are decimalized. The cultivable land which has dramatically decreased has led to the production of artificial types of food in laboratories. As a result, new types of cerial and other seeds that can bear unfavourable conditions are currently being produced: However, all these are under the control of multinational companies, which means that they check up even the production of foods on the planet Earth.

Human evolution and progress has rendered our life inhuman and has downgraded its quality. To make matters worse, the emission of radioactive substances and nuclear waste, apart from the fact that they cause deadly infections, they also lead the entire ecosystem to dangerous changes. Phenomena, such as the hole in the ozone layer and the acid rain, involve environmental changes which undermine the future but also in the longer-term the survival of the human race.

Apart from the deterioration of the Man’s material substance, the cutting off from nature has also caused a crack in his inner self. Removed from the natural environment, people of our century have lost their sensitivities and their stimuli. The landscape around them has been aesthetically deformed. This is quite obvious in the big urban centres where pollution, fumes and unreasonable town planning have degraded the quality of life.

Besides, the natural environment in its declining course sweeps along the archaeological monuments, which, even if they have existed for many centuries, are in danger by modern culture.

Last but not least, the rich national cultural heritage is lost in the impersonal big cities where people lead an exhausting lifestyle. They have to work for a lot of hours in order to secure for themselves and their family what modern life dictates. Consequently, the need for the resolution of the environmental problems is imperative. Above all, a redefinition of the values of life and the priorities people place is required. Only then will an essential solution be found by the people themselves.

Stella Lionaki,
Kyriakos Kostopoulos,
Anna Neskourenko
(Class: A6 , 2nd EPAL, Sivitanidios)

Climate Changes in the 21st Century
June 28, 2007 02:37 AM PDT

Climate Changes in the 21st Century

Since the Industrial Revolution in the mid 1800s, global temperatures have risen about 1 degree Celsius. When compared to earth’s long history of incredibly slow climate change, this is frighteningly fast. Ice core samples from Greenland and Antarctica reveal that over the last 160,000 years, global temperature change has been linked to the amount of CO2 in the atmosphere. With CO2 levels rocketing as a result of modern technology, the effects on the planet are likely to be catastrophic.

Global warming is the theory that due to man’s activity on the planet, dangerous gases such as CO2, methane, water vapor and ozone are collecting in the earth’s atmosphere, making it hotter. This phenomenon is also called the Greenhouse Effect, because the gases trap in heat like a greenhouse. CO2 is released into the atmosphere when fossil fuels (such as wood, coal, and petroleum) are burned. Use of fossil fuels is an essential part of our everyday lives, primarily through transport, heating and other energy consumption. IN this way, we are all responsible, on an individual and national level.

Predictions for the future
Rising seas, floods and disease

Flooding, higher levels of intense rain and snowfall, and the planet’s rising sea level have been connected to global warming. Scientists predict that if the Earth heats up between 1 degree Celsius and 3 degrees Celsius in the next 100 years, then the sea level will rise between 15 centimeters and 120 centimeters in that time or up to 20 centimeters by 2030. This means that major US cities such as New York, Boston and Miami could soon find themselves submerged in water. According to present day calculations, any area 2 meters above sea level will be at risk in only 30 years time. Favourite vacation spots which contain rich ecosystems and fairy beaches are likely to become devastated. Ocean City, Maryland and the islands in North Carolina and Chesapeake Bay could certainly be affected by rising sea levels. Apart from the USA numerous other spots will not remain untouched by global warming. The Great Barrier Reef in Australia would be at risk of bleaching along its entire length resulting in the destruction of many species. Sea levels around the British Isles would actually recede due to ocean and atmospheric circulation patterns. In Russia and Canada, forests which trap CO2 and help guard against global warming will be at risk of forest fires and pest attacks. Ten percent of mammals in China are already threatened with extinction, and climate change could affect the lovable giant panda. Wetlands in Spain and Brazil could lose their own endangered species. To make matters worse, dangers of serious disease are imminent. As tropical climates spread, mosquitoes will multiply and spread malaria and yellow fever to new areas. Heat waves and droughts will dry up land and harm existing ecosystems, drastically affecting the quality of life we experience today.

Who is to blame?

Although home to less than 10% of the world’s population, the USA leads the world in CO2 emissions, by contributing nearly one quarter of the planet’s man-made greenhouse gases China is a close second, with other Third World countries accounting for half, and Europe producing 12% (relatively low, due to increasing use of nuclear and wind power.

What is the action of the European Union against greenhouse gases emissions?

The Protocol of Kyoto resulted from the Convention-frame on the climatic changes which was signed in the Conference of Rio, in June 1992, by almost all the participating states. The objective of the Convention was "the stabilization of the accumulated greenhouse gases in the atmosphere, to such an extent that the anticipated dangerous-for-the creatures-of–the-planet consequences could be avoided".

In 1997, the Protocol of Kyoto was signed with a view to control the emissions. The Kyoto Protocol constitutes a legal guaranteed engagement of the industrially developed states that they will decrease the level of the emissions of six gases of greenhouse during the period 2008-2012, in a 5.2 percentage in comparison with the 1990 percentage. The Protocol became an international binding law when ratified by a certain number of countries. Greece with the rest member states of the European Union ratified it in May 2002.

Flexible mechanisms of the Protocol

A country can achieve the objectives set by the Kyoto Protocol either by decreasing its emissions, or, alternatively, using the so-called "flexible mechanisms" allocated by the Protocol. These mechanisms are the following three:
1) Negotiation of the rights of emissions by an industrially developed country with another which is hard to achieve the objective.
2) Creation of "Mechanism of Clean Growth" by the developing industrially countries with the economic help of developed countries.
3) Application of programs by the countries which have been committed to reduce the emissions via the Protocol of Kyoto.

Shared Responsibility: The Roles We All Play

Power plants have been proved to contribute a 33% of total emissions. If individuals could put pressure on governments to get companies to use renewable energy sources, this frightening figure could decrease. There are many non-governmental international organizations who are sensitive to global warming issues, such as the World Wildlife Fund, Friends of the Earth, and Greenpeace. A visit to their websites may get you more involved.

Everyday actions

Since transportation – the cars, trains and airplanes we all use – gives off 34% of emissions, and factories and home heating systems produce a further 33%, we can all play a huge role. We can opt to take public transport or share cars with others, or use a bicycle. Also, if you intend to buy a new car, be on the lookout for new exhaust-free ones, already being produced by General Motors, Toyota and Mercedes Benz. Choose energy-efficient domestic appliances, and use energy-conserving fluorescent light bulbs. Inevitably the role of the state leaders is crucial. However, if all these billions of people on the Earth lead their lives with the appropriate respect to the environment and follow simple and practical tips, not only will we save the planet, but we will also make it a better place to live!

You may read the following Green leaflet compiled by the students of 2nd Professional Lyceum, Sivitanidios, Kallithea, to see how simple and pleasant is to improve the current environmental state.

(The above article was compiled by Vassilis Vlasseros
Anna Neskourenko
Dimitris Spyropoulos
Helena Moutafidou
Yiakou Emirian
The whole processing and mixing of sound, picture and text was made by Emirian Giakou, Class A5, Sivitanidios).


Current, October 2005, Mary Glasgow Magazines
Go Natural, 1st Issue, February 2007
Guardian newspaper, June 5, 2006

Green Leaflet: A few tips to help save the Earth
June 28, 2007 02:30 AM PDT

2nd Professional Lyceum, Sivitanidios
The Green Team advises: A Few Tips to Help Save the Earth

The e-twinning project Green planet Perfect planet made us become aware of the current precarious situation of our planet. We have considered which actions each of us must take and addressed ourselves to our common tasks of preserving all life on earth. Our message is that small changes can save the planet. So how do we start making a difference?

1. Turn off the lights and the TV. Don’t also
leave appliances (e.g. mobile phone charger)
on standby and remember not to leave any of
them on charge unnecessarily.

2. We can both save energy and reduce our
electricity bills if we replace regular bulbs
by fluorescent which consume 4-5 times
less energy and last 8-15 times more than
regular bulbs. If all Greek households
swapped three regular bulbs for greener
versions, it would save enough energy
to supply all the countries street lights
DID YOU KNOW that each kw/hour
saved in our country results in the decrease
of one kilo of CO2 for the atmosphere?

3. Buy energy efficient products looking
out for a logo denoting products it
recommends. By law, white goods must
now be labeled to show how energy
efficient they are. The most energy efficient
products get an A grade (AA for fridges and

4. Turning your thermostat down by 1°C
could cut your heating bills by up to 10%.
Cleaning and maintaining the heater/boiler
once a year ensures the effective operation
(over 80% of the heating system).

5. Double glazing and cavity wall insulation
keep the warmth in the cold out. Such a
measure might be expensive, but you can save
money in the long run. Insulating 50 square
metres of the ceiling saves up 350lt of oil
per year.

6. Fix leaking taps and make sure they’re
fully turned off. DID YOU KNOW that
a dripping hot water tap wastes as much hot
water as to fill half a bath? According to the Mediterranean S.O.S network a leaking toilet flusher can consume in one day as much water as we could drink in 50 days. If we wash our teeth leaving the tap on for one minute we consume approximately 15 litres of water.

7. We can avoid using plastic bags for our shopping goods. There are non-disposable carrier bags which can be bought from supermarkets. DID YOU KNOW that every year about 500 billion plastic bags are used worldwide?

8. We should throw all newspapers magazines and paper waste into the recycling bins. DID YOU KNOW that round 10% of all household rubbish is still made up of newspapers and magazines

9. If you have a garden, you could recycle some of your waste as compost.

10. Rather than chucking out items that are still in reasonable condition, you could recycle them by giving them away to friends or to a charity shop. You may also find takers for your unwanted furniture and white goods by putting a classified add in a newspaper. Giving things away reduces not only the amount of waste in landfills sites but also the energy needed to produce new goods.

The Energy Issue in the 21st Century
June 28, 2007 02:17 AM PDT

The Energy Issue in the 21st Century

At present, 80% of total world energy consumption is based on fossil fuels (oil, coal, natural gas), while only 2% comes from renewable energy sources such as the wind or the sun. Our continued dependence on these energy sources entails a serious problem of sustainability, associated with two factors: the limited stocks of fossil fuels and the pollution that results from their conversion into electrical energy.

During the last 50 years, global consumption of energy has risen more than fourfold. The current rate of consumption in the rich countries is a direct threat to future consumption, as just 34% of the world population consumes 72% of the energy produced. The amount of fossil fuels we use is set to rise though oil and gas are expected to reach their culminating point between 2010 and 2030. This fact troubled us and we started collecting information about the possible renewable sources of energy as well as their advantages and disadvantages. We also realized that the policy of clean technologies should be followed by the world’s governments otherwise the production will not be able to meet the growing demand. We thought to collect as much data as possible and produce short presentations of SOLAR, WIND and WATER POWER, BIOFUEL (coming from biomass), GEOTHERMAL and HYDROGEN POWER. However, we placed special emphasis on solar and wind power as the Greek climate favours the development and utilization of these natural resources.
The answer to the question “What can be done about the energy problem?” could be the following:
1) Limit energy consumption (individual level)
2) Develop and use renewable sources of energy (national and international level)

Energy Issue: The current situation in Greece

The energy sector in Greece has developed rapidly since World War II. Electrical production increased by almost 50% during the 1980s, due largely to the expansion of coal-burning thermoelectric stations. Two-thirds of the country’s energy is produced in power stations burning domestically produced coal. Hydroelectric power stations produce 8% of the country’s electricity. The rest comes from oil-fired generators. Almost all of Greece’s oil is imported.

Issidora Karra,
Kamelia Kounga

June 28, 2007 02:13 AM PDT


The sun is the basic source of energy of our planet. For 5 billion years, the sun has been radiating energy that constitutes approximately 70% from hydrogen. Consequently, the Sun is not expected to reduce its radiation for the rest million or billion years to come. Every square metre of the Sun’s surface emits 63 MW of power. In eight minutes’ time, solar radiation of 1355 Watt/m2 finally reaches the boundaries of the earthly atmosphere. The solar radiation that enters the earthly atmosphere is the one that causes the evaporation of water, moves air and marine currents and generally creates the meteorological phenomena. Despite the fact that the solar radiation that reaches the boundaries of the earthly atmosphere is constant everywhere, this is not true with the one that reaches the ground, the power of which seldom exceeds 1000 Watt/m2 . It depends on the season of the year, the hour of the day, the presence of clouds, fog and dust, while the smaller the angle of its incidence on the ground of the Earth is, it faints more. This last factor is also of utmost importance for the configuration of medium intensity of solar energy that reaches the ground. From this point of view, Greece is one of the most prosperous regions of our planet. The combination of Greece’s geographic width and intense sunlight results in the incidence of 4.3 KWh of solar energy for every square metre of its horizontal surface. In most of the regions in Greece, the sunlight lasts more than 2700 hours per year.


Solar power systems capture solar radiation and, distribute it to the water, air or other fluid, in the form of heat. Their most widespread application is the production of hot water for both domestic and professional use. However, they are also used for the production of electricity.
A typical system of hot water production is constituted by the solar collectors which have a specially designed reservoir for the storage of the redundant heat and also by the necessary piping system and control systems. The solar radiation is absorbed by the collector and the collected heat is drawn in the storage reservoir.
The energetic solar systems are separated in 2 big categories, depending on the way that the heating medium is used in order to transfer the heat to the water for use. The first big category includes the open solar power systems, in which the water of the supply network is heated directly and, afterwards, it is channelled to final use. The second big category includes the closed systems, in which a special antifreeze solution circulates through the piping of the collector. Afterwards, an alternator transfers the heat from the antifreeze solution to the water of the network. Such systems are mainly used in regions where there is the possibility of frost.


Solar PV (Photovoltaic cells)

Solar PV (photovoltaic) uses energy from the sun to create electricity to run appliances and lighting. PV requires only daylight – not direct sunlight – to generate electricity.

How It Works

Photovoltaic systems use cells to convert solar radiation into electricity. The PV cell consists of one or two layers of a semi conducting material, usually silicon. When light shines on the cell it creates an electric field across the layers, causing electricity to flow. The greater the intensity of the light, the greater the flow of electricity.

The most important benefit of using PV systems is that they do not generate greenhouse gases, saving approximately 325 kg of carbon dioxide emissions per year – adding up to about 8 tons over a system’s lifetime – for each kilowatt peak (kWp – PV cells are referred to in terms of the amount of energy they generate in full sun light).

PV arrays now come in a variety of shapes and colours. In particular, there are grey ‘solar tiles’ that look like roof tiles, panels and transparent cells that you can use on conservatories and glass which provides shading and generates electricity. Apart from the fact that they enable you to generate free electricity, they can provide an interesting alternative to conventional roof tiles!

Cost and maintenance

Prices for PV systems vary, depending on the size of the system to be installed, type of PV cell used and the nature of the actual building on which the PV is mounted. For the average domestic system, costs can be around 6500 – 14,000 Euros per kWp installed, with most domestic systems usually between 1.5 and 2 kWp. Solar tiles cost more than conventional panels, and panels that are integrated into a roof are more expensive than those that sit on top.

Planning considerations

Some local authorities require planning permission to allow you to fit a PV system, especially in conservation areas or on listed buildings. Always check with your local authority about planning issues before you have a system installed. Obtaining retrospective planning permission can be difficult and costly.

Helias Krikos ,
Pericles Mantzanas


• Centre of Renewable Energy Sources (CRES)
Solar Power (www.cres.gr)

June 28, 2007 02:11 AM PDT


Wind energy is a renewable source of energy that is created indirectly by the solar radiation. The invariable heating of the surface of the ground from the sun causes the locomotion of big masses of winds from the one region to the other, creating in this sense the winds.
The source of energy is contained in the force of the winds which blow across the earth’s surface. As soon as it was harnessed, wind energy was converted into mechanical energy for performing work such as pumping water or grinding grain (windmills). Nowadays, by connecting a spinning rotor to an electric generator, modern wind turbines convert wind energy, which turns the rotor, into electric energy.
As we have already mentioned, the source of this energy is practically inexhaustible and as it is continuously renewed, it is named “renewable”. Ιf there were a possibility to exploit the total wind potential of the Earth , using current technology, it is estimated that the electricity produced by the power of the wind in one year would be about double than the amount needed to cover the needs of humanity in electric energy in the same period of time.


The power of the wind has been used by the people since the antiquity. If we look up in an encyclopaedia about Greek mythology, we will find out that the importance and the usefulness of winds as natural forces, made Zeus, the Father of the gods, to nominate Aeolus the “manager” of the winds. Aeolus directed the winds from his fabulous island, Aiolida. Moreover, the idea of capturing the winds inside a skin expresses precisely the need of common people to allocate the winds in the place and time it suited them. For many hundreds of years, the movement of ships was supported exclusively by the force of the winds, while the use of the windmill as a locomotive machine, in the rural sector, has mainly been abandoned in the mid of the 20th century.

Did you know that?

• Egyptians may have been the first to capture wind energy when they sailed boats along the river Nile around the 4th century B. C

• Persians developed the first windmill in the 7th century A.D.

• The first windmills to appear in Europe were built during the 12th century in northwest France and southern England.

In the mid of the 20th century, when the use of fossil fuels expanded rapidly and the electricity reached even the most remote points the use of simple machines was abandoned. The interest in the exploitation of the wind power, mainly in the production of electric current, was expressed intensely during the mid of the 70s and it was the result of the oil crisis which had meanwhile burst out. Since then, there has been a continuously increasing tendency for the production of electric current via the exploitation of wind power.

In the 20th Century:

• The oil crisis of the 1970s urged efforts into developing wind energy as an alternative source of electricity. Many countries with Denmark having the lead were successful in developing modern wind turbines.

• The modern wind turbine is the result of the technological advances of the 1980s and 1990s. Today, wind turbines which have the same size as the traditional European windmill, can generate 250 to 300 kilometers of power - a nearly tenfold increase in efficiency.


Τhe modern systems of exploitation of wind power include machines which convert wind power into electricity and are called wind generators. There are many types of wind generators which are classified in two basic categories:
• Wind generators of horizontal axis.
• Wind generators of vertical axis
In the world market, the wind generators of horizontal axis have prevailed in a percentage above 90%. The output of a wind generator depends on the wind potential of the region where they are installed. Today the cost of manufacture of wind generators has decreased considerably and it can be inferred that the wind energy has covered the first period of its maturity as it has become competitive with the conventional forms of energy. Taking into consideration the fact that wind generators are being constantly improved in terms of their output and reliability and the development of the relative technology, it can be estimated that the cost of the exploitation of wind energy can decrease up to 30% in the next 10 years.


The most important financial investment of wind generators could be their connection to the electric network of a country so as to achieve the maximum output of electric power and cover the energy needs of this country. In this case, a wind farm, that is to say a cluster of wind generators are installed in a concrete place with high wind potential and they channel the total output of their production to the electric network.
This application aims at the mass exploitation of the wind power and it is particularly simple. It simply connects the wind farm to the existing electric network through a substation, in which the step- up transformers and the other necessary means of protection are installed. In this way, it is not necessary to construct a particular system for managing and controlling the produced energy as all the produced
energy is distributed to the electric network.


Wind energy is a promising source of electrical power as it is a clean and renewable resource. However, because wind speeds vary by time of day, season, and even from one year to the next, wind energy is an intermittent source. At windy sites, it is common for wind turbines to operate 60 percent of the wind dynamics and as a result the wind may be insufficiently strong for the wind turbines to generate energy at full capacity. In comparison, coal-fired plants usually operate an average of 75 to 85 percent of full capacity. In the current energy market, where price is the primary benchmark, business and industry are not prone to invest in technologies that require long-term development. However, this could be achieved only with determined political commitment.

Panayiotis Trivizas


• Centre of Renewable Energy Sources (CRES)
WIND POWER (www.cres.gr)
• Microsoft Encarta (2002 Edition)

June 28, 2007 02:08 AM PDT


Power derived from the fall of water from a higher to a lower level, and extracted by means of waterwheels or hydraulic turbines. Waterpower is a natural resource, available wherever a sufficient volume of steady water flow exists. The development of waterpower has led to the extensive construction of storage lakes, dams, bypass canals, and the installation of large turbines and electric generating equipment. Because the development of hydroelectric power requires a large capital investment, it is often uneconomical for a region where coal or oil is cheap. However, the cost of fuel for a steam–powered generating plant is higher than the cost of running a hydroelectric plant. To conclude, increasing environmental concerns are focusing attention on renewable energy sources. The use of waterpower dates from Ancient Greece and Rome where waterwheels were used for the milling of corn.


Worldwide, hydropower represented 19 percent of the total energy generated in 1998, the most recent year for which data is available. More precisely:

• Norway derived 99% of its power from hydroelectric plants.
• In the Democratic Republic of Congo hydroelectric power provided 99% of the electricity used.
• The hydroelectric plant on the Panama River between Brazil and Paraguay has the greatest capacity in the world (12,600 megawatts in full operation).
• Canada, the largest producer of hydroelectric power in the world generated 340.3 billion kilowatt-hours in 1999- which amounts to 60 percent of the country’s electric power.
• In Greece, hydroelectric power stations produce just 8 percent of the country’s electricity.

Demetris Tassios


June 28, 2007 02:05 AM PDT


A) Tidal Energy

Tide is defined as the oscillation of sea level because of the magnetism exerted on the hydrosphere by the Moon and the Sun. The elevation of the sea level is called rising tide, while the drop of the sea level is called low tide or ebb.

The energy of tide

As it happens with all kinds of waves, the tidal wave has energy potential which is essential to alter the sea level and mobilize the particles of hydrosphere during their rotational movement. The total tidal power output is enormous but it is lost because of the frictions in the bottom of the sea while the wave is spread over the coast. It is believed that this friction causes a slight deceleration of the rotation of the Earth resulting in a very small increase of duration of the day.
Tidal power is not new. Tidal mills were built in the eighteenth century when their major competition was windmills and water wheels. The tidal mills largely vanished once we had cheap steam engines. Today, people can claim the tide in many ways. The most obvious is to capture sea water at high tide, then run it out through a turbine during low tide. As a result, when tides come into the shore, they can be trapped in reservoirs behind dams. Then when the tide drops, the water behind the dam can be let out just like in a regular hydroelectric power plant. An increase of at least 16 feet between low tide and high tide is needed. Consequently, there are only a few places where this tide change occurs around the earth. Some power plants are already operating using this idea.

Operation of the first submarine station to produce electricity

In 1967, the first industrial plant to make use of the tidal power was constructed in Rance (France). It can power 240,000 homes.

In 2003, the first commercial submarine station to produce electricity by exploiting the tidal currents of the sea was constructed in Norway. The tide produces 300 kilowatts of electric force, which is enough to supply electric power to 30 Norwegian houses or 60-80 British houses.

THE TIDAL GENERATOR: This tidal generator exploits the tidal energy in the same way that the windmills exploit the force of air streams. This generator constitutes of a fin which has a ten-meter-diameter and rotates as the water passes above it. It is then connected with a generator in order to produce electricity. The whole mechanism is mounted highly above a 20-meter-column of steel fixed in the bottom. In addition, tidal mills tend to give immense sums of energy. The European Committee calculates that the tidal currents round Britain, for example, could produce as much electric energy as 48 Terawatts/hour per year. The Committee has determined 106 possible regions around Europe, 42 of which are located in Britain.

Tidal Power Systems: Advantages and Disadvantages

The tidal energy has a basic advantage compared to the other renewable forms of energy – it has the possibility of giving a continuous source of force for almost 24 hours a day. The wind and the solar power output fluctuate during the day. On the contrary, the tide flows continuously towards a certain direction precisely for 12 hours, it stops for a while, and then it is reversed. Despite all these, tidal energy has a basic disadvantage and this concerns the cost of its production compared to this of producing wind power. To sum up, although tidal energy has the potential for picking up about a fiftieth of our energy consumption, tidal power systems are potentially big and expensive, and they pose threats to ocean ecosystems.


The final ocean energy idea uses temperature differences in the ocean. If you ever went swimming in the ocean and dove deep below the surface, you would have noticed that the water gets colder the deeper you go. It’s warmer on the surface because sunlight warms the water. But below the surface, the ocean gets very cold. That’s why scuba divers wear wet suits when they dive down deep. Their wet suits trap their body heat to keep them warm.
Power plants which use this difference in temperature to produce energy, can be built. A difference of about 38 degrees Fahrenheit is needed between the warmer surface water and the colder deep ocean water.
Using this type of energy source is called Ocean Thermal Energy Conversion or OTEC. Currently, it is being used in some demonstration projects, in both Japan and Hawaii.


Kinetic energy (movement) exists in the moving waves of the ocean. That energy can be used to power a turbine. In such a construction, the wave rises into a chamber. The rising water forces the air out of the chamber. The moving air spins a turbine which can turn a generator. When the wave goes down, air flows through the turbine and back into the chamber through doors that are normally closed.
This is only one type of wave-energy system. Others actually use the up-and-down motion of the wave to power a piston that moves up and down inside a cylinder. That piston can also turn a generator.
Most wave-energy systems are very small. However, they can be used to power a warning buoy or a small light house.

Demetris Tassios


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