Hydroelectric power is one of the oldest sources of energy. It was once used to power water and saw mills or turn a paddle wheel for grinding grain. Today, the power of moving water is largely used to produce electricity.

Hydro power accounts for 15 percent of the world's current electricity generation – more than nuclear energy. Other renewable sources of energy contribute just four percent.

And hydroelectric power is clean. Each megawatt of electricity produced by hydro power prevents the further rise of greenhouse gas emissions. Studies show that hydroelectric power alone could satisfy the present world demand for energy. But experts say that's unlikely to happen.

"The cost-benefit analysis simply doesn't add up," says Andre Boehling of Greenpeace. "You need to have a differentiated view of water as a source of renewable energy – that is on a case-to-case basis."

Doing things differently

As a green energy source, hydro is still far from perfect. Large hydroelectric facilities can often adversely impact ecosystems and land use.

But a project in Honduras shows that it doesn't have to be that way. The "La Esperanza Hydroelectric Facility" in Honduras is widely considered as an example of a successful and sustainable hydro power project.

It uses existing hydroelectric structures linked to an old dam, its impact on the surroundings is minimal and the benefits of constant electricity production are apparent in the region.

The project led by Canadian entrepreneur Ron Turner was nominated for the "World Clean Energy Award." It was also the first project of its kind in the world to be allowed to sell its own carbon credits after the Kyoto Protocol took effect in 1997.

Big hydro dogged by controversy

But elsewhere, hydro power's image as a "clean energy" source has taken a beating.

Many big dam projects around the world have turned into ecological, economic and social disasters. The controversial Sardar Sarovar dam in India and the Three Gorges dam in China have become symbols for environmental degradation and violation of human rights rather than for progress.

Large dam reservoirs, which destroy floodplain forests, are even more problematic. Research shows that rotting vegetation in such reservoirs releases significant amounts of methane, a greenhouse gas more than 20 times as potent as carbon dioxide.

Despite their damaging reputation, big dams are still being built in India, China and South America.

Drawing lessons from Honduras

Experts say the debate about the pros and cons of large hydro projects is unthinkable in industrialized countries.

"The discussion about new mega projects in Germany is over," says Harald Uphoff from the federal German Association of Hydroelectric Plants.

He says the potential for growth in the hydro power sector is centered on new technology. For instance, tests are being carried out on attaching power-generating buoys in rivers without greatly disturbing the ecology.

More importantly, existing hydro plants, which are often more than 50 years old, need to be modernized to produce more electricity. The "La Esperanza" facility in Honduras has demonstrated how that can be done.

Potential for Germany?

In Germany, hydro power is the second most important source of renewable energy after wind.

Hydroelectric energy accounts for 3.5 percent of total electricity generation. But the question of whether hydro power should be further expanded is the subject of fierce debate about the economic and ecological benefits.

"In the long-term we can't expect any significant growth in hydro power in Germany," says Andre Boehling from Greenpeace.

But others disagree. "This attitude has something of a self-fulfilling prophecy," says Harald Uphoff.

He says that operators of hydro plants in Germany believe that electricity generation from water could rise by at least a third.

Small-scale, decentralized hydroelectric plants with a capacity of five megawatts are considered the next big thing. So far, they generate about 20 percent of German hydro energy.

"Such a plant can often satisfy the energy demands of an entire village," says Uphoff.

15,000 unused dams

But Germany’s hydroelectric industry isn’t free of controversy either. In a study in 2008, the German government listed 15,000 embankments and dams in German creeks and rivers that still can't be used for electricity generation.

That’s because the hydro industry often faces resistance from environment activists, dampening hopes that it can gradually produce as much electricity as the nuclear sector.

An amendment to Germany's renewable energy law in 2009 has come up with a solution to appease both sides. The law aims to raise the incentive to produce clean energy that is really environmental-friendly.

Thus, operators who enhance a small-scale plant with sensible green measures such as fish ladders to enable easier passage receive more money for each megawatt of electricity produced.

Author: Oliver Samson (sp)

Editor: Ranty Islam