Tag Archives: Wave power

Ocean waves pack bigger and stronger punch

The ocean waves are now hitting harder than ever. As the world warms, they gain in energy, impact and height.

LONDON, 23 January, 2019 – As the world’s seas warm, the ocean waves are starting to pack more power. Spanish scientists monitoring the tropical Atlantic report that the waves today contain more energy than they did 70 years ago. Sea surface temperatures influence wind patterns, and the payoff is a wave with more impact.

What this means for marine creatures, mariners, meteorologists and the mayors of seaside cities is not yet certain. But it does mean that wave energy could join carbon dioxide atmospheric ratios, global sea level rise and global air temperatures as yet one more metric of overall global warming and climate change.

And Chinese scientists who have been calculating the heat absorbed by the oceans over the last 30 years have confirmed that in 2018 ocean temperatures reached record levels. Before that, 2017 was the hottest oceanic year ever, followed by 2015, 2016 and 2014. Once again, the implications are uncertain: sea levels will rise with ocean temperatures.

“The new data … serve as an additional warning to both the government and the general public that we are experiencing inevitable global warming”

Researchers from the University of Cantabria in Santander, Spain report in the journal Nature Communications that waves have been growing in height in recent decades, and satellite studies confirmed a change of about 1% every four years from 1985 to 2008.

But their research focused on changes in wave energy, important because of the effect wave behaviour has on estuaries, shoals, beaches, dunes, headlands, harbours and sea defences. They examined data from 1948 to 2017 to trace a small but measurable increase in wave energy with the decades.

“For the first time, we have identified a global signal of the effect of global warming in wave climate,” said Borja Reguero, of Cantabria’s environmental hydraulics institute, who is also at the University of California Santa Cruz.

“In fact, wave power has increased globally by 0.4% per year since 1948, and this increase is correlated with the increasing sea surface temperatures, both globally and by ocean regions.”

A hundred million Hiroshimas

Chinese and US researchers recently calculated the heat absorbed by the oceans as ever higher ratios of greenhouse gases – the product of fossil fuel combustion and other human action – are added to the planet’s atmosphere.

Members of the same team report in the journal Advances in Atmospheric Sciences that between 2017 and 2018 alone, the oceans must have absorbed an extra quantity of heat equivalent to 388 times the total electricity generation in China, and – to choose another and more vivid unit of measurement – around 100 million times the heat released by the atomic bomb that in August 1945 destroyed the Japanese city of Hiroshima.

“The new data, together with a rich body of literature, serve as an additional warning to both the government and the general public that we are experiencing inevitable global warming,” said Lijing Cheng of the Chinese Academy of Sciences, the lead author of the report.

“The ocean and global warming have already taken place and caused serious damage and losses to both the economy and society.” – Climate News Network

The ocean waves are now hitting harder than ever. As the world warms, they gain in energy, impact and height.

LONDON, 23 January, 2019 – As the world’s seas warm, the ocean waves are starting to pack more power. Spanish scientists monitoring the tropical Atlantic report that the waves today contain more energy than they did 70 years ago. Sea surface temperatures influence wind patterns, and the payoff is a wave with more impact.

What this means for marine creatures, mariners, meteorologists and the mayors of seaside cities is not yet certain. But it does mean that wave energy could join carbon dioxide atmospheric ratios, global sea level rise and global air temperatures as yet one more metric of overall global warming and climate change.

And Chinese scientists who have been calculating the heat absorbed by the oceans over the last 30 years have confirmed that in 2018 ocean temperatures reached record levels. Before that, 2017 was the hottest oceanic year ever, followed by 2015, 2016 and 2014. Once again, the implications are uncertain: sea levels will rise with ocean temperatures.

“The new data … serve as an additional warning to both the government and the general public that we are experiencing inevitable global warming”

Researchers from the University of Cantabria in Santander, Spain report in the journal Nature Communications that waves have been growing in height in recent decades, and satellite studies confirmed a change of about 1% every four years from 1985 to 2008.

But their research focused on changes in wave energy, important because of the effect wave behaviour has on estuaries, shoals, beaches, dunes, headlands, harbours and sea defences. They examined data from 1948 to 2017 to trace a small but measurable increase in wave energy with the decades.

“For the first time, we have identified a global signal of the effect of global warming in wave climate,” said Borja Reguero, of Cantabria’s environmental hydraulics institute, who is also at the University of California Santa Cruz.

“In fact, wave power has increased globally by 0.4% per year since 1948, and this increase is correlated with the increasing sea surface temperatures, both globally and by ocean regions.”

A hundred million Hiroshimas

Chinese and US researchers recently calculated the heat absorbed by the oceans as ever higher ratios of greenhouse gases – the product of fossil fuel combustion and other human action – are added to the planet’s atmosphere.

Members of the same team report in the journal Advances in Atmospheric Sciences that between 2017 and 2018 alone, the oceans must have absorbed an extra quantity of heat equivalent to 388 times the total electricity generation in China, and – to choose another and more vivid unit of measurement – around 100 million times the heat released by the atomic bomb that in August 1945 destroyed the Japanese city of Hiroshima.

“The new data, together with a rich body of literature, serve as an additional warning to both the government and the general public that we are experiencing inevitable global warming,” said Lijing Cheng of the Chinese Academy of Sciences, the lead author of the report.

“The ocean and global warming have already taken place and caused serious damage and losses to both the economy and society.” – Climate News Network

Offshore wind at risk from wave power

EMBARGOED until 0001 GMT on Saturday 2 March Offshore wind turbines are vulnerable to sudden and catastrophic destruction in moderately stormy seas, according to new research. LONDON, 2 March – Wind turbines are at constant but unpredictable risk of being snapped in pieces like matchsticks by medium-sized waves, a researcher has found. “The problem is, we still do not know exactly when the turbines may break”, says Professor John Grue from the Department of Mathematics at the University of Oslo, Norway. In 1989 Grue, a leading wave researcher, discovered a phenomenon called ringing, which is a type of vibration that occurs when choppy waves strike marine installations. So far scientists have studied ringing only in small and large waves, but it now appears to be more common in medium-sized waves. For marine turbines with a cylinder diameter of eight metres, the worst waves are those that are more than 13 metres high and have an 11-second interval between them. These waves occur in even small storms, which are fairly common off the Norwegian coast. The ringing problem may increase significantly, because there are plans to build tens of thousands of offshore turbines. “If we do not take ringing into consideration offshore wind farms could lead to financial ruin”, Grue told Apollon, Oslo University’s research magazine. The largest offshore wind farms are off the Danish and British coasts, though these are small scale compared with installations planned in the area of the Dogger Bank, out in the North Sea.

Oil industry also at risk

So far it has not been possible to use an actual turbine to measure the force exerted by ringing. But Grue says laboratory measurements show the biggest vibrations occur just after the wave has passed, not when it strikes the turbine. Immediately after the crest of the wave has passed, a second force hits the structure and it’s this which creates the ringing. “If that resonates with the structural frequency of the turbine, the vibration will be strong… This increases the danger of fatigue”, says Grue. Estimates of the damage caused by ringing are not yet reliable enough to allow an accurate calculation of the material fatigue that it produces, says Grue. “Ringing is very difficult to measure –  there is great uncertainty.” Scientists also need to consider whether the turbines are in deep or shallow water. “The structural frequency also depends on conditions on the seabed. You can compare it with a flagpole in a storm, which vibrates differently depending on whether it is fixed in concrete or in soft ground.” Ringing does not harm wind turbines alone. It is already a big problem for the oil industry. The designers of one oil platform did not take ringing into account, and lost NOK 12 billion (US$ 2.1 bn), says Grue. “It’s possible to build your way out of the ringing problem by strengthening the oil rigs. But it doesn’t make financial sense to do that with turbines.” Many advocates of wind power argue in favour of siting turbines offshore, where they tend to attract less opposition and there’s space to place wind farms far apart (see our story of 27 February, Wind power ‘may be less than thought’. Professor Grue’s research suggests that siting farms at sea could give rise to serious problems. – Climate News Network

EMBARGOED until 0001 GMT on Saturday 2 March Offshore wind turbines are vulnerable to sudden and catastrophic destruction in moderately stormy seas, according to new research. LONDON, 2 March – Wind turbines are at constant but unpredictable risk of being snapped in pieces like matchsticks by medium-sized waves, a researcher has found. “The problem is, we still do not know exactly when the turbines may break”, says Professor John Grue from the Department of Mathematics at the University of Oslo, Norway. In 1989 Grue, a leading wave researcher, discovered a phenomenon called ringing, which is a type of vibration that occurs when choppy waves strike marine installations. So far scientists have studied ringing only in small and large waves, but it now appears to be more common in medium-sized waves. For marine turbines with a cylinder diameter of eight metres, the worst waves are those that are more than 13 metres high and have an 11-second interval between them. These waves occur in even small storms, which are fairly common off the Norwegian coast. The ringing problem may increase significantly, because there are plans to build tens of thousands of offshore turbines. “If we do not take ringing into consideration offshore wind farms could lead to financial ruin”, Grue told Apollon, Oslo University’s research magazine. The largest offshore wind farms are off the Danish and British coasts, though these are small scale compared with installations planned in the area of the Dogger Bank, out in the North Sea.

Oil industry also at risk

So far it has not been possible to use an actual turbine to measure the force exerted by ringing. But Grue says laboratory measurements show the biggest vibrations occur just after the wave has passed, not when it strikes the turbine. Immediately after the crest of the wave has passed, a second force hits the structure and it’s this which creates the ringing. “If that resonates with the structural frequency of the turbine, the vibration will be strong… This increases the danger of fatigue”, says Grue. Estimates of the damage caused by ringing are not yet reliable enough to allow an accurate calculation of the material fatigue that it produces, says Grue. “Ringing is very difficult to measure –  there is great uncertainty.” Scientists also need to consider whether the turbines are in deep or shallow water. “The structural frequency also depends on conditions on the seabed. You can compare it with a flagpole in a storm, which vibrates differently depending on whether it is fixed in concrete or in soft ground.” Ringing does not harm wind turbines alone. It is already a big problem for the oil industry. The designers of one oil platform did not take ringing into account, and lost NOK 12 billion (US$ 2.1 bn), says Grue. “It’s possible to build your way out of the ringing problem by strengthening the oil rigs. But it doesn’t make financial sense to do that with turbines.” Many advocates of wind power argue in favour of siting turbines offshore, where they tend to attract less opposition and there’s space to place wind farms far apart (see our story of 27 February, Wind power ‘may be less than thought’. Professor Grue’s research suggests that siting farms at sea could give rise to serious problems. – Climate News Network