Category Astrophysics

What was the World’s oldest tidal power station?

The La Rance tidal power station in Brittany, France is the world’s first tidal power station. Inaugurated on November 26, 1996 and still operational, it is, naturally, the world’s oldest tidal power station as well. A.S Ganesh takes a look at tidal energy and the La Rance power station…

Our energy needs have constantly been on the rise throughout our existence with a burgeoning worldwide population and increased per capita energy consumption, the amount of energy that we need has been skyrocketing. Climate change and global warning in the midst of all this has pushed the conversation towards finding better alternatives than fossil fuels in items of energy sources.

A renewable source                                          

Tidal energy is a renewable source of energy that is produced by the surge of ocean waters during the ebb and flow of tides. The production of tidal energy, however, is still in its infancy with only a small amount of power produced by it overall so far. This does not mean that the necessary technology isn’t available with us. Far from it. The ways to use tidal movement to produce electricity was developed by our scientists and engineers in the 20th Century.

Tidal range

Tidal energy is harnessed in area between low tide and high tide – the tidal range – is significant. One such area is on the Rance estuary at Ille-et-Vilaine in Brittancy, France. This area houses the La Rance tidal power station, the world’s first and oldest tidal power station. Tidal plants use a barrage or enclosure-type installation in order to build an artificial reservoir as they rely on the changing heads of water that tides bring to device the turbines that produce the electricity. The Rance river estuary is suited for this purpose owing to its large tidal range, with an average of 8m between low and high tides – a figure that can jump up to 13.5m in the spring and neap range.

Not easy to construct

While plans to build the La Rance began as early as 1943. it was nearly another quarter of a century before the completed structure was ready to use. Construction was no easy task as dams were raised to block the Rance river, so that the estuary was completely drained out and the reservoir’s establishment across the site could be facilitated.

On November 26, 1966, the La Rance tidal power plant was officially inaugurated by French President Charles de Gaulle. With a 330 m-long dam enclosing a 22 km2 area basin, the plant has a large reservoir of 184 million cubic meters. As bulb turbines allow for power generation both in the ebb and flood cycles of the tide, this plant houses 24 bulb turbines, each of which weights 470 tonnes with a 5.4 m diameter and a eating of 10 MW.

Low maintenance

Operated by Electricite de France (EDF). the plant has produced over 27,000 GWh of electricity in its over five decades of operation Maintenance requirements have been minimal as cathodic protection is employed for all the turbines, the gates and the metallic parts of the lock. This, despite the fact that each of the 24 bulb turbines have run for over 2,00,000 hours on average.

According to the details provided by EdF, ebb generation accounts for 60% of the total energy produced, free flow through the turbine orifices corresponds to 20%, pumping for 15-20% while flood generation is responsible only foe 2-6% of the energy generated.

Even though the La Rance power plant was built at a prohibitive initial cost of $ 100 million, the long-term rewards are there to see. In addition to paying for itself in its first 20 years, it has by now recovered all of its costs through the savings created by energy production.

Predictable, perpetual

Tidal energy can be a viable option in the search for replacements for fossil fuels. Not only does producing tidal energy cost less than nuclear or solar power, but it also has the advantage of being predictable and perpetual. Engineers have access to the cycles predicting the movement of tides from a daily basis to even an annual basis, allowing for little interruption in the energy generation. It is also not much influenced by weather, meaning it can keep generating electricity day and night foe as long as the plant is operational.

Despite the advantages of tidal energy, there are very few commercial –sized tidal power plants operational in the world at the moment. One of the major concerns or drawbacks that this form of energy generation has is its environmental impact.

Negative impact

Tidal power negatively impacts marine life by altering sedimentation patterns. The barrage causes progressive silting in the surrounding ecosystem, thereby affecting the native aquatic plants, fish and other organisms.

While La Rance continues to operate and produces energy that is equivalent to that consumed by city the size of Rennes, France, a lot more needs to be done if tidal energy is to become an alternative to conventional energy sources. Engineers and scientists worldwide are not only working to improve the technologies and costs involved, but are also looking at how best to minimize the impact on the environment.         

Picture Credit : Google

WHAT IS SEA LEVEL RISE AND WHY IS IT HAPPENING?

As our planet warms, oceans across the globe absorb a large portion of the heat generated. In the process, the water expands, resulting in universal sea-level rise. In addition, the rise is also caused by the melting of glaciers and icebergs. Usually such melting during warmer months and freezing during colder months is a natural phenomenon. However, with global warming, there’s more of the former than the latter, leading to alarming sea-level rise, threatening to submerge several cities within just a few decades.

Why does sea level change?

Causes sea level to rise because water expands as it warms up; melting of the world’s ice sheets. A large ice mass, which flows over hills and valleys and occupies a large portion of a continent. The world has only three major ice sheets today (Greenland, West Antarctica, and East Antarctica).

In Greenland and Antarctica;  melting of smaller around the world; and decrease in the amount of water held on land, for example, in groundwater beneath the land and in reservoirs above the land. Ocean warming accounts for around half of the observed change in sea level (this is often called “thermal expansion”), with the melting of thousands of small glaciers accounting for the other half of the increase in sea level. Since the 1800s, the melting ice sheets in Antarctica and Greenland have contributed relatively little to sea level change. But, these ice sheets are starting to melt faster due to global warming and may push sea level up much more in the future.

How much could sea level rise?

Because of global warming, the thermal expansion of the ocean and glacier melting will continue to play a role in the rise of sea level in the future . If all of the planet’s remaining as small glaciers were to melt, sea level would rise about 50 cm. The amount that thermal expansion can raise sea level in the future will depend on the continued warming of sea water. The largest possible contribution to sea level rise in the future comes from the world’s large ice sheets in Greenland, West Antarctica, and East Antarctica. If these ice sheets melted completely, the level of the oceans would rise about 7 m from the Greenland ice sheet, 5 m from the West Antarctic ice sheet, and 53 m from the East Antarctic ice sheet. This is why many glaciologists (scientists who study ice) focus on how Greenland and Antarctica are changing because of global warming.

How will sea level rise affect the countries of the world?

The effect of ice sheet melting on sea level is different across the world.

So, when the sea level rises, people will be affected in different ways, depending on where they live. The UK is used to occasionally dealing with rising sea level for short periods of time, particularly when there are storms at the same time as when the tides higher than usual. If the IPCC predictions are correct, we must consider the possible increase in sea level on top of natural tidal surges. This will cause dangerously high tides to occur more often in the coming decades, and these future tides might be more destructive than we are used to.

In farming regions near the coast, seawater flooding on land can contaminate the soils with salt, making them less able to support the growth of crops. The salty water may also get into underground stores of fresh water (known as groundwater), which is the source of important drinking water and also for farmers to grow crops.

In coastal cities, sea level rise will cause more flooding to houses, businesses, and while it may seem sensible to consider moving cities away from harmful floods, especially as we know it will likely happen in the future, our cities cost so much to develop that we are more likely to simply try to protect them from rising sea levels. A vision of our cities near the sea involves them with walls facing the ocean several meters high, with the street level of the cities themselves being below the level of the ever rising sea.

Credit : Frontiers for young mind 

Picture Credit : Google 

WHAT CAUSES TIDES?

Water level on the surface of the oceans rises and falls. These are called tides. Tides are a result of gravitational forces of the Moon and the Sun as well as the centrifugal forces of Earth’s spin. The total amount of water does not change; it just rises at one place while receding at the other.

High tides and low tides are caused by the moon. The moon’s gravitational pull generates something called the tidal force. The tidal force causes Earth—and its water—to bulge out on the side closest to the moon and the side farthest from the moon. These bulges of water are high tides.

As the Earth rotates, your region of Earth passes through both of these bulges each day. When you’re in one of the bulges, you experience a high tide. When you’re not in one of the bulges, you experience a low tide. This cycle of two high tides and two low tides occurs most days on most of the coastlines of the world.

Tides are really all about gravity, and when we’re talking about the daily tides, it’s the moon’s gravity that’s causing them.

As Earth rotates, the moon’s gravity pulls on different parts of our planet. Even though the moon only has about 1/100th the mass of Earth, since it’s so close to us, it has enough gravity to move things around.

When the moon’s gravity pulls on the water in the oceans, however, someone’s bound to notice. Water has a much easier time moving around, and the water wants to bulge in the direction of the moon. This is called the tidal force.

Because of the tidal force, the water on the side of the moon always wants to bulge out toward the moon. This bulge is what we call a high tide. As your part of the Earth rotates into this bulge of water, you might experience a high tide.

Credit: SciJinks

Picture Credit : Google 

What is nebula?

A nebula is a formation in space which is constituted mostly of helium, dust, and other gases in various concentrations. The shape and size of a nebula varies, and as such there can be various types of formations having different sizes. Very often, they are huge in size, and their diameters can be a number of light years across. It is derived from Latin, and as such means a cloud. Nebulae exist in the space between the stars—also known as interstellar space. The closest known nebula to Earth is called the Helix Nebula. It is the remnant of a dying star—possibly one like the Sun. It is approximately 700 light-years away from Earth.

It is not clear how exactly a nebula is formed, but it is believed that they are formed by the collapsing of interstellar medium, which then come together because of the gravitational pull of the particles. Nebula is an important object for observation by researchers, who derive significant information about the formation process of stars and planets. A nebula is capable of exerting a gravitational pull, and the force is derived from the particles which come together to form the nebula. With more particles coming together, not only does the nebula increase in proportion, but its gravitational pull also gathers more power and intensity. A nebula is also believed to be one of the primary stages in the formation of stars. Scientists are of the opinion that a nebula can be used to create a trajectory of stellar evolution. There are various nebulae that are in existence at present, though numerous others may exist in the far-flung corners of space that remain to be observed. Some of the most popular ones are Pelican, Crab, Eagle, and Ring Nebula, with Ring being among the most observed ones on the planet.

Credit : Economic Times

Picture Credit : Google 

How does the gravitational pull of the moon and the sun cause ocean tides?

High tides and low tides are caused by the moon. The moon’s gravitational pull generates something called the tidal force. The tidal force causes Earth—and its water—to bulge out on the side closest to the moon and the side farthest from the moon. These bulges of water are high tides.

As the Earth rotates, your region of Earth passes through both of these bulges each day. When you’re in one of the bulges, you experience a high tide. When you’re not in one of the bulges, you experience a low tide. This cycle of two high tides and two low tides occurs most days on most of the coastlines of the world.

Tides are really all about gravity, and when we’re talking about the daily tides, it’s the moon’s gravity that’s causing them.

As Earth rotates, the moon’s gravity pulls on different parts of our planet. Even though the moon only has about 1/100th the mass of Earth, since it’s so close to us, it has enough gravity to move things around. The moon’s gravity even pulls on the land, but not enough for anyone to tell (unless they use special, really precise instruments).

When the moon’s gravity pulls on the water in the oceans, however, someone’s bound to notice. Water has a much easier time moving around, and the water wants to bulge in the direction of the moon. This is called the tidal force.

Because of the tidal force, the water on the side of the moon always wants to bulge out toward the moon. This bulge is what we call a high tide. As your part of the Earth rotates into this bulge of water, you might experience a high tide.

One thing to note, however, is that this is just an explanation of the tidal force—not the actual tides. In real life, the Earth isn’t a global ocean, covered in an even layer of water. There are seven continents, and that land gets in the way. The continents prevent the water from perfectly following the moon’s pull. That’s why in some places, the difference between high and low tide isn’t very big, and in other places, the difference is drastic.

Credit : SciJinks 

Picture Credit : Google

HOW DOES GRAVITY AFFECT THE TIDES?

The moon, too, has gravity. Its gravitational pull is much less than the Earth’s, as its mass is smaller, but it still has an effect on Earth. On the side of the Earth nearest the Moon, the oceans are pulled out by the Moon’s gravity, causing a high tide. Exactly the same thing happens on the opposite side of the Earth, but this time because the Moon is exerting less pull on the waters of the oceans. As the Earth rotates on its axis, each part of the Earth is turned towards the Moon once in every twenty-four hours. That means that the seas have two high tides every twenty-four hours — once when they are facing the Moon and once when they are on the opposite side of the Earth from the Moon.

Tides are really all about gravity, and when we’re talking about the daily tides, it’s the moon’s gravity that’s causing them.

As Earth rotates, the moon’s gravity pulls on different parts of our planet. Even though the moon only has about 1/100th the mass of Earth, since it’s so close to us, it has enough gravity to move things around. The moon’s gravity even pulls on the land, but not enough for anyone to tell (unless they use special, really precise instruments).

When the moon’s gravity pulls on the water in the oceans, however, someone’s bound to notice. Water has a much easier time moving around, and the water wants to bulge in the direction of the moon. This is called the tidal force.

Because of the tidal force, the water on the side of the moon always wants to bulge out toward the moon. This bulge is what we call a high tide. As your part of the Earth rotates into this bulge of water, you might experience a high tide.

One thing to note, however, is that this is just an explanation of the tidal force—not the actual tides. In real life, the Earth isn’t a global ocean, covered in an even layer of water. There are seven continents, and that land gets in the way. The continents prevent the water from perfectly following the moon’s pull. That’s why in some places, the difference between high and low tide isn’t very big, and in other places, the difference is drastic.

Picture Credit : Google