22 May 2012

Earth's inside for better air

Wai-O-Tapu thermal area, Rotorua region.                  The active fault lines along the length 
of New Zealand (green colour), 
where the Pacific and Australian plates meet.
(Picture: NZ Waikato Regional Council)

New Zealand is a volcanic and seismic area. The tragic earthquake of 2010 in the Canterbury region, South Island of the country, was a sad reminder of this. Such an area is also a place where the earth’s interior shows itself at the surface, offering a unique experience of nature…

A natural source of energy

Hot water and steam from deep soils sometimes naturally gather in what is called a geothermal reservoir. A natural reservoir… of energy. Properly processed, this water and steam can be transformed to electricity for instance. These are the basis of geothermal energy.

As the energy is available naturally, it does not require any fuel to process it. This is why very low emissions of greenhouse gases result from the transformation. And this is why geothermal energy is considered as a low-carbon technology, among the low-carbon solutions that humankind must promote.

The Nga-Awa-Purua geothermal
station provides enough
electricity for about 140 000 homes.
“Although few regions in the world are currently undertaking geothermal projects, the potential is huge”, says Jonathon Clearwater. Jonathon works as an engineer at Mighty River Power. The company is a specialist in geothermal development, operating several stations in the North Island of New Zealand.

“Indonesia, Philippines, USA, or Iceland for instance take benefit of their geothermal capacities. Japan also has a lot of potential”, adds Jonathon. In the Philippines, 27% of the electricity comes from geothermal energy.

New Zealand takes advantage of the chance

A geothermal power station.
The extracted water can be
up to 300°C.
(Picture : Mighty River Power)
Jonathon explains : “geothermal electricity generation commenced in 1958 at Wairakei station. At that time, the plant was only the second geothermal plant in the world producing electricity. New Zealand was world leading! Development was slow in the following decades, mainly due to cheap petrol during the 1990s and the early 2000s. But now the technology is back. Expensive oil and global warming have changed the deal.”

“Mighty River Power has the exciting mission to promote this reliable and renewable energy”, Jonathon adds. “Any project is very specific as the technology must adapt to a site which is always unique. It is a case by case task.”

At Kawerau power station, the geothermal energy is not transformed to electricity but is directly used as heat for the nearby paper factory.

The carbon footprint of the electricity production

All electricity generation technologies emit greenhouse gases at some point in their life cycle but some are more environmentally friendly.

Geothermal electricity emits low quantities of greenhouse gases. It means that in order to produce a kilowatt-hour of electricity, few quantities of greenhouse gases are released into the atmosphere. By greenhouse gases we mean the carbon dioxide (CO2) and other gases. The quantity of these other gases is usually measured as gram of equivalent CO2 (g CO2-equivalent).

The unit “g CO2-equivalent per kilowatt-hour” is often used to compare the different technologies. The following comparison chart helps to identify what are the solutions for humankind to produce low-carbon electricity.
In this chart, the emissions of greenhouse gases concern the whole life cycle of the technology:
operation but also construction and maintenance;
the extraction, processing and transport of their fuel (when applicable);
and their decommissioning and disposal.
(Source: UK Parliament 2011 – Compiled by F. Gheung) 

Unfortunately not all regions of the planet allow developing geothermal or hydro-electric energies. Wind and solar solutions, which are subject to climate variations, have lots of potential. It is certain that new solar technologies will be a big part of our future energetic system. Sun sends a huge quantity of energy to Earth and today only a very low percentage of it is used by man. A star for a better air…

We had the chance to meet Jonathon on the 18th of April, at the office of Mighty River Power in Rotorua, located in the middle of New Zealand North Island.

About marine technologies...
At the end of 2011, the French electricity company Electricité de France installed their first marine turbines in the North of France. The installation will bring electricity to around 2000 homes.

Presentation video - in French language


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