A dam in the center of the earth

Renewable energies except solar electric or thermal (seeforums dedicated below): wind turbines, energy from the sea, hydraulic and hydroelectricity, biomass, biogas, deep geothermal energy ...
freddau
I posted 500 messages!
I posted 500 messages!
posts: 641
Registration: 19/09/05, 20:08
x 1

A dam in the center of the earth




by freddau » 20/03/08, 21:37

The Shem took up a 50-year-old challenge: to build a dam, 700 meters deep, in the heart of the Pyrenees.

This is a scenario for Jules Verne lovers. Imagine the bottom of a green valley in the heart of the Pyrenees mountains, a few kilometers from the Spanish border. The road climbs slowly in switchbacks. At the bend of a bend, clinging to the more hostile flanks, a small inn with white walls and a small church almost lost. The end of the trip?

Not so sure. By pushing further, road rollers and bulldozer complete a very steep path which collides 400 meters higher up into the mountain. Terminus. This time there is only nature. Well almost. In this grandiose setting, the eye is drawn to a green door stuck to the rock. Once the obstacle has been overcome, a horizontal tunnel is emerging, two meters high and a little over one meter wide. This is the start of a journey to the center of the Earth. Very quickly, all that remains is the sound of footsteps, a slight cold (5 degrees all year round) and a gallery that never seems to stop. Bifurcation to the right, then to the left. Gradually the Earth begins to rumble. We continue, and after 660 meters, it's the end of the tunnel.

700 meters below the top of the mountain, flourishes the Salle de la Verna, a jewel of the Pierre-Saint-Martin chasm, a gruyere with 360 kilometers of galleries and cavities made famous by Haroun Tazieff's camera in the 1950s. Each year, speleologists come to explore it by the hundreds. La Verna is the largest cave ever discovered in France. A true cathedral 190 meters high and 250 meters wide. So immense that the headlamps cannot distinguish its limits.

The tunnel leads to a balcony formed by huge rocks almost halfway up the room. The condensation is such that fine droplets float like a light cloud. On the left, in the distance, the Saint-Vincent river cascades down the slope, burying itself under the earth. Strange sensation where hum and inner peace mingle. “This room is so large that its first discoverers believed they were outside after reaching it… We could bring Notre-Dame de Paris into it six times!” Marvels Bernard Bertuola. This fifty-something on the eve of retirement is not a caver, but project manager for the Hydroelectric Company of the Midi (Shem). This subsidiary of the Suez group, specializing in electricity production, has just completed the construction of a dam in the very heart of the Verna room itself. A "crazy" project, inseparable from the history of this cult place for speleologists from all over the planet.

EDF gave up in 1960

The hydroelectric adventure began in 1956, five years after the discovery of the massif by Tazieff and his companions, and three years after the entry of three speleologists from Lyon into the immense room of La Verna. "We have in fact taken over an old project led by EDF since 1956", explains Bernard Bertuola. At the time, the incumbent operator was in a frenzy of construction of hydraulic dams. First interested in the capacities that the Saint-Vincent river seemed to offer, EDF gave up its project in 1960, after having dug this Pyrenean rock for four years. The site does not deliver the expected electricity production capacity. Far from being abandoned, the tunnel built by EDF has since been used by speleologists, the true custodians of what has become the first European caving center.

Without the support of these enthusiasts, no roadblock could have been envisaged. The engineers of the Shem know this. We had to gain their trust and convince the municipalities. "Membership was made without difficulty," recognizes Bernard Bertuola, who launched the project at the end of the 1990s. Because everyone sees their interest in it. Michel Douat is a speleologist. With his friend Jean-François Godart, from the departmental caving committee, they followed the industrial site with keen interest. “The construction of this dam is done with respect for the environment. Biotope studies have been carried out. And the risks to the environment are very limited, ”they explain, pointing to an Aphaenops. These little beasts, which look like ants, are actually beetles. Depigmented and without eyes, they have developed, in the absence of light, a great tactile sensitivity to devour bacteria and humus. So far the only companions of the Aphaenops, the speleologists want to take advantage of the hydroelectric project to democratize their activity, little known to the general public.

Local authorities are also being won over: the development of access to the tunnel will make it possible to make access to the Verna room accessible to tourists this year. A site that should quickly earn its three stars in the Michelin Green Guide, as the place is spectacular and steeped in history.

The hardest part remained to be done: complete the incredible project. In the center of the Earth, this immense and empty belly fills with the din of the waterfall carved out by the Saint-Vincent river. Just upstream, when the water is expelled from the rock to enter the room, the torrent is trapped by a water reservoir; in fact a small pool four meters deep and a few meters wide, barely. From this small dam, a penstock captures most of the flow in the absence of a flood and conveys the water to a turbine installed nearly four kilometers below in the Basque village of Sainte-Engr Grâce.

Before reaching the forest, then plunging into the valley to the village, the pipe, 60 centimeters in diameter, follows the same path as the gallery previously dug by EDF. 70 centimeters below the initial path. Hence the need to use explosives for months. With thoroughness. Before each explosion, a man went to settle in the Verna room to prevent any speleologists at the end of the race from taking this exit dug by EDF. Equipped with his headlamp, this guard would ford next to a large chest filled with survival gear, food and a mattress, in case the tunnel became blocked for several days.

No big machine could get into the Verna room. Concrete, sand, steel joists were therefore transported by hand or on small trolleys. “To build the dam, we had to take up a real human challenge,” enthuses Bernard Bertuola. Among the difficulties to be overcome: the need to divert the bed of the torrent in order to dry up the part where the water reservoir is today built. It was also necessary to fix a footbridge to the cliff that allows men to access the dam, and the penstock to join the gallery dug from 1956 to 1960 by EDF. Work carried out by the Pyrenean company HC, specializing in special work related to the mountain environment. "The guys were held up by a rope and worked in suspension… A real acrobatic job", explains the engineer of the Shem.

The investment for the Suez subsidiary amounts to 6 million euros for around two years of work. A relatively low cost which should allow the Sainte-Engrace site to become profitable within ten years. In this regard, the Shem can say thank you to EDF, which previously worked to substantially reduce the costs of the site ... Without the tunnel drilling beforehand, the cost of the project would have been much higher and the dam would never have existed.

The first tests started in January. In a few days, the Verna dam, open to the general public for the first time on April 5 and 6, will deliver its 4 MW for decades. This is not much compared to the Three Gorges Dam in China, 4 times more powerful, but it is enough to meet the annual electricity needs of 500 people. Privileged people who will never know that their bulbs are powered from the center of the Earth.


source: figaro
Last edited by freddau the 22 / 03 / 08, 11: 25, 1 edited once.
0 x
User avatar
Remundo
Moderator
Moderator
posts: 15992
Registration: 15/10/07, 16:05
Location: Clermont Ferrand
x 5188




by Remundo » 21/03/08, 11:30

If I understood correctly, it would be a question of exploiting the natural cavities of a mountain (filled by a stream) as a dam, and having at the foot of the mountain a pressure equivalent to the height of the mountain, i.e. 10 bar for 100 m.

I fear nevertheless that the geological stability of the rocks and the possible leaks require a thorough and difficult study ...
0 x
Image
Christophe
Moderator
Moderator
posts: 79117
Registration: 10/02/03, 14:06
Location: Greenhouse planet
x 10972




by Christophe » 21/03/08, 11:31

So a kind of underground geysere?
0 x
User avatar
highfly-addict
Grand Econologue
Grand Econologue
posts: 757
Registration: 05/03/08, 12:07
Location: Pyrenees, 43 years
x 7




by highfly-addict » 21/03/08, 11:47

Yeah, in fact a simple diversion of watercourses by penstock. The only originality of the thing is the construction of the catchment basin underground and therefore without large machines.

This is to say if the number of new "exploitable" sites for hydroelectric power is limited in Europe!

a more detailed explanation and a series of photos here.
0 x
User avatar
gegyx
Econologue expert
Econologue expert
posts: 6930
Registration: 21/01/05, 11:59
x 2870




by gegyx » 21/03/08, 13:25

I just viewed the photos of the site.
Nothing too spectacular. But an interesting initiative.
Not stupid! To make white coal, we fill the valleys, and we fill the mountains ...
What do the organizations dealing with underground heritage think?
It is simply a water reservoir, for a penstock, as there are many in the Pyrenees. But does the holding capacity seem unimportant to me?
It's always good for renewables.
0 x
freddau
I posted 500 messages!
I posted 500 messages!
posts: 641
Registration: 19/09/05, 20:08
x 1




by freddau » 22/03/08, 11:28

They will seek electricity to the heart of the mountains.

The principle of forced driving is not new, but the place is.
0 x

 


  • Similar topics
    Replies
    views
    Last message

Back to "hydraulic, wind, geothermal, marine energy, biogas ..."

Who is online ?

Users browsing this forum : No registered users and 274 guests