Hydroelectric power

[JonathanM]

Following on from discussions with @aveatry on other threads, I thought this issue deserved its own thread. Hydroelectricity is by far the largest renewable globally, and thousands of new projects are planned. But recently there have been growing concerns about the amount of greenhouse gases they release, which in some cases, especially in tropical climates, might actually be more than fossil fuelled electricity.

Anyway, here is a fascinating recent article which discusses very simply, but also with a good amount of detail, the four mechanisms by which hydropower can release greenhouse gases. It then goes on to discuss how good design can mitigate some of these releases.

Degassing is one of four emissions pathways associated to reservoirs. The other three include CH4 bubbling, CO2 diffusion and CH4 diffusion.

Carbon emissions from hydropower reservoirs: facts and myths

www.hydropower.org

 

[motorbiking]

Good grief. Someone was paid to research that?

hydrogen powered metal smelting, is interesting stuff. Solar makes electricity, electricity splits water, hydrogen fuels the fire to melt the metal. More versatile than electric arc furnaces

 

[JonathanM]

Good grief. Someone was paid to research that?

Do you mean it isn't worth researching?

 

[motorbiking]

Beyond the existing research which estimated 24 rather 23g/kwh? - No. What is the point of it? Its a highly dynamic industry and I suspect the assessment was immediately out of date.

It's all about choosing the right solution based on the location and its already vastly better than the alternatives.

 

[JonathanM]

Beyond the existing research which estimated 24 rather 23g/kwh? - No. What is the point of it?

It's all about choosing the right solution based on the location and its already vastly better than the alternatives.

What a bizarre way to look at things! Research that makes energy production more efficient is always worthwhile. With your attitude we would still believe the sun orbited the earth.

Anyway, that 24 figure is out of date. The new research has revealed that badly designed hydro in the tropics could actually be worse than fossil fuels. The ongoing research will now allow better design of hydro plants. That certainly seems worthwhile to me. It would be a massive shame if 60% of new global renewables ended up coming from hydro and only then did we find out, because they had been badly designed, it was actually worse for the climate than fossil fuels. I'm glad they are doing the research, so they can understand how to build them to work efficiently.

A new EDF study published this week in Environmental Science and Technology shows that hydropower — the leading renewable energy technology projected to grow rapidly — is not always as good for the climate as broadly assumed. Moreover, continuing to assume that it is could mean that projects meant to reduce greenhouse emissions will unintentionally increase them instead.

If minimizing climate impacts are not a priority in the design and construction of new hydropower facilities, it could lead to limited or even no climate benefits.

 

[Brigadier]

Flood a wooded valley = rotting, and release of GHGs = bad.

The above is a one-off thing though, is it not?

Once the existing [forest] has rotted, and its GHGs have been released, it can't rot-and-release all over again, can it?

Or, have I misunderstood?

 

[JonathanM]

Flood a wooded valley = rotting, and release of GHGs = bad.

The above is a one-off thing though, is it not?

Once the existing [forest] has rotted, and its GHGs have been released, it can't rot-and-release all over again, can it?

I've read elsewhere (in a very reputable source) that it goes on for several decades. According to the article above, it's more to do with the soil than the trees.

 

[motorbiking]

What a bizarre way to look at things! Research that makes energy production more efficient is always worthwhile.

Anyway, that 24 figure is out of date. The new research has revealed that badly designed hydro in the tropics could actually be worse than fossil fuels. The ongoing research will now allow better design of hydro plants. That certainly seems worthwhile to me. It would be a massive shame if 60% of new global renewables ended up coming from hydro and only then did we find out, because they had been badly designed, it was actually worse for the climate than fossil fuels. I'm glad they are doing the research.

from the article:

In a few rare and extreme cases, hydropower reservoirs have been documented to produce significantly higher emissions, while others have close to zero emissions or can act as carbon sinks.

But importantly there is no economic/feasibility assessment of what can be done to reduce / improve it. There is also no assessment of the benefits of man made "lakes".

 

[JonathanM]

from the article:



But importantly there is no economic/feasibility assessment of what can be done to reduce / improve it.

I think the main point of the article is to show how the emissions can be minimised. The two main suggestions don't sound expensive. Many of the new plants will be in the tropics, where if badly designed, they can be worse than fossil fuels. Anyway, that article is just a basic starting point. Here is some more info, demonstrating the danger of lacking curiosity.

https://blogs.edf.org/energyexchang...e-hydropower-can-actually-be-bad-for-climate/

A new EDF study published this week in Environmental Science and Technology shows that hydropower — the leading renewable energy technology projected to grow rapidly — is not always as good for the climate as broadly assumed. Moreover, continuing to assume that it is could mean that projects meant to reduce greenhouse emissions will unintentionally increase them instead.

Our research shows why it is important to ensure that future hydropower projects don’t hurt, but help, the climate. For example, if new hydropower plants in India have greenhouse gas emissions properties similar to existing Indian hydro plants, they could be worse for the climate than emissions from average natural gas plants over the first 50 years of operation, due to methane emissions as well as carbon dioxide emissions from reservoir creation.

https://pubs.acs.org/doi/10.1021/acs.est.9b05083

However, analyses of climate impacts of hydropower plants have been simplistic, emphasizing the aggregated 100-year impacts from a one-year pulse of emissions. Such analyses mask the near-term impacts of methane emissions central to many current policy regimes, have tended to omit carbon dioxide emissions associated with initial plant development, and have not considered the impact of the accumulation of gases in the atmosphere over time. We utilize an analytic approach that addresses these issues. By analyzing climate impacts of sustained hydropower emissions over time, we find that there are enormous differences in climate impacts among facilities and over time.

If minimizing climate impacts are not a priority in the design and construction of new hydropower facilities, it could lead to limited or even no climate benefits.

 

[motorbiking]

its not about lacking curiosity, its spotting an article that says nothing much other than might, could may... and we don't know.

Obviously it's no surprise that EDF, are keen to point out the natural gas, "could" be lower emission than hydro power.

There are so many other factors to consider than g/kwh.

 

[motorbiking]

Flood a wooded valley = rotting, and release of GHGs = bad.

The above is a one-off thing though, is it not?

Once the existing [forest] has rotted, and its GHGs have been released, it can't rot-and-release all over again, can it?

Or, have I misunderstood?

temperature makes a big difference. In hot climates, there is probably an argument to make the reservoir deeper, so that the Co2 sinks to the bottom due to the water being cooler. Thats effetely why oceans absorb Co2.

 

[JonathanM]

Obviously it's no surprise that EDF, are keen to point out the natural gas, "could" be lower emission than hydro power.

It's not EDF the power company

In 1991, The Economist called EDF "America's most economically literate green campaigners."

 

[motorbiking]

I was surprised they weren't telling us that Nuclear was the most environmentally friendly