“Geothermal power facilities currently generate 25% of the country’s total electricity production.”
Over the past of a few years, Iceland has definitely made a change. Iceland went from what was known as one of Europe’s poorest countries to a country with high standard of living. Studies have shown that “In 2014, roughly 85% of primary energy use in Iceland came from indigenous renewable resources. Thereof 66% was from geothermal.”
Iceland as a country…
Iceland is relatively a young country geologically. It lies astride one of the earth’s major fault lines, the Mid-Atlantic ridge. This is the boundary between the North American and Eurasian tectonic plates. As a result of its location, Iceland is one of the most tectonically active places on earth, More than 200 volcanoes are located within the active volcanic zone stretching through the country from the southwest to the northeast, and at least 30 of them have erupted since the country was settled. In this volcanic zone, there are at least 20 high-temperature areas containing steam fields with underground temperatures reaching 250°C to 1,000 m depth.
As a way to understand its “concept” in an easier way, the video below explains and shows how Iceland is based on geothermal energy and describes how this benefits the country in many different ways by showing geothermal potential around the world:
Now that we have some background information about this country let’s talk a little bit about how they use geothermal resources…
The island itself its basically a blister of porous basalt at the crack in Earth’s crust where the North America. There are enormous underground reservoirs of water that are continually renewed by levels of annual precipitation that range as high as 177 inches over Iceland’s glaciers, and shallow patches of magma that heat the deepest reaches of these reservoirs to temperatures in excess of 750 degrees Fahrenheit.
The graphic below represents the use of geothermal energy during the year of 2013.
The following image shows how electricity generation has developed since 1970-2013.
It is clear to see, how the demand for geothermal energy has significantly increased over the years.
Iceland is known around the world as a leader in the use of geothermal district heating. Today, about 9 out of 10 households are heated with only geothermal energy.
Geothermal energy has been used for thousands of years in some countries for cooking and heating. It is simply power derived from the Earth’s internal heat. This thermal energy is contained in the rock and fluids beneath Earth’s crust. It can be found from shallow ground to several miles below the surface, and even farther down to the extremely hot molten rock called magma
There are three types of geothermal power plants: dry steam, flash, and binary. Dry steam, the oldest geothermal technology, takes the steam out of fractures in the ground and uses it to directly drive a turbine. Flash plants pull deep, high-pressure hot water into the cooler, low-pressure water. The steam that results from this process is used to drive the turbine. In binary plants, the hot water is passed by a secondary fluid with a much lower boiling point than water. This causes the secondary fluid to turn to vapor, which then drives a turbine. Most geothermal power plants in the future will be binary plants.
Generating Heat:
In difference from the U.S there is not a national grid in Iceland- harnessing the energy comes via the remarkably simple method of sticking a drill in the ground near one of the country’s 600 hot spring areas, and using the steam that is released to turn the turbines and pump up water that is then piped to nearby settlements.
Geothermal water is used to heat around 90% of Iceland’s homes, and keeps pavements and car parks snow-free in the winter. Hot water from the springs is cooled and pumped from boreholes that vary between 200 and 2,000m straight into the taps of nearby homes, negating the need for hot water heating. It’s also purified and cooled to provide cold drinking water.
Generating electricity:
Once this heated water is forced to the surface, it is a relatively simple matter to capture that steam and use it to drive electric generators. Geothermal power plants drill their own holes into the rock to more effectively capture the steam.
There are three basic designs for geothermal power plants, all of which pull hot water and steam from the ground, use it, and then return it as warm water to prolong the life of the heat source. In the simplest design, known as dry steam, the steam goes directly through the turbine, then into a condenser where the steam is condensed into water. In a second approach, very hot water is depressurized or “flashed” into steam which can then be used to drive the turbine.
In the third approach, called a binary cycle system, the hot water is passed through a heat exchanger, where it heats a second liquid—such as isobutane—in a closed loop. Isobutane boils at a lower temperature than water, so it is more easily converted into steam to run the turbine.
These systems are best representing in the picture below
References:
http://www.scientificamerican.com/article/iceland-geothermal-power/
http://www.theguardian.com/environment/2008/apr/22/renewableenergy.alternativeenergy
http://ourworld.unu.edu/en/geothermal-energy