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The Yin-Yang of Hydropower

Unread postPosted: Fri 27 Jan 2017, 16:56:34
by KaiserJeep
For the record, I don't recall starting any thread in the "Environment" subforum before, but I figure this is the correct place for a discussion of hydropower and dams. Consider these IEA hydropower statistics (created June 25, 2016) for a moment:

Percent of world’s electricity produced by Hydropower: 21 %
Total number of people that hydropower supplies with energy: 1,250,000,000
Percent of U.S. energy supplied by Hydropower: 9.25 %
Percent of renewable consumption provided by Hydropower in the U.S.: 49 %
Total number of dams in the U.S.: 80,000
Total number of dams in the U.S. that are utilized for Hydropower: 2,400
Percent of efficiency hydropower turbines can achieve: 95 %
Total number of countries that utilize hydropower: 30 countries
Percent of electricity hydropower provides for the northwestern United States: 70 %
Percent of Norway’s electricity provided by hydropower: 99 %
Percent of New Zealand’s electricity provided by hydropower: 75 %

Cut and pasted today from this page:

I have also just watched and will separately post my review of the 2014 documentary "DamNation" in the Book/Media section later today.

Speaking as an Electrical Engineer who worked in computers but who has been obsessively studying energy sources for 3+ years, I would like to state a couple of things before the main discussion begins.

Firstly, the drought that afflicted the Western US in recent years appears to be over. Last June when the above statistics were generated, hydropower was 49% of the total "green" energy in the US. Here in Silly Valley, we have 280% of the average rainfall for the 12 months just passed, multiple mudslides, and localized flooding. Although it would take at least two more such wet years before we could declare that "the drought has ended", we at least are no longer facing a dire water shortage, and many of our hydropower facilities that were idled by lower water levels are again online, and the 49% statistic above is likely to go to 50-60% of the "green" energy this year in spite of the increases in wind and solar and other sources.

Secondly is something the documentary above does not state. Hydropower is much beloved by EE's because it is not an intermittent energy source as are wind and solar. A volume of water impounded behind a dam represents an energy store with a known value, that can be utilized at any time needed. It is also uniquely able (for a "green" power source) to be throttled up and down in a short period of time, simply via the mechanical actions in opening and closing sluices and gate valves upstream of the water turbines. In fact, the hydropower dams are a unique variable energy source that enable the much more variable solar and wind sources, by compensating for the intermittent nature of those two green energy sources in particular. It also is an enabler of nuclear power plants, which by their nature are slow to start, stop, and control.

In fact, one of the very few alternatives to hydropower in regard to controllable energy generation is large gas turbine "peaking power plants", which are not particularly efficient forms of fossil fuel energy generation, but are extremely controllable and can be throttled up and down as quickly as can hydropower. Gas supplies are at the moment more than adequate due to "fracking" and similar techniques, not to mention LPG imports from the Middle East, but "Peak Gas" looms in our future.

So the conundrum with hydropower would be:

- It is "green energy", in the sense that it does not emit carbon or waste heat in operation, since nothing is being burned. During construction of course, a lot of petroleum-fuelled machinery is used to move earth and rock, and to manufacture/mix/pour concrete, and coal is used to make the steel reinforcements for the concrete dam and a lot of both steel and copper are used in the huge generators.

- It is intensely destructive of the environment, for the most part in the construction phase, but also on an ongoing basis to a certain degree, as it suppresses the ebb and flow of rivers and removes the periodic floods that naturally renew riparian areas.

- It is the biggest single source of green power, and because it can be throttled, it also enables the more intermittent green energy sources such as wind and solar. The gas turbine alternative consumes FF and emits carbon dioxide.

- The reservoirs created are enjoyable recreation areas with multiple uses - but (being an avid trout fisherman) not as personally enjoyable to me as the natural fisheries the dams destroyed, and the annoyance of the millions of almost identical "clone" fish produced by the government fish hatcheries.

- The flood control and water supplies created are separate benefits, tempered by the fact that they enable us to grow grain in what were once arid desert areas, and enable human habitation in riparian river zones no longer subject to flooding.

Re: The Yin-Yang of Hydropower

Unread postPosted: Fri 27 Jan 2017, 17:38:30
by sparky
Hydro does create a carbon emission , the cement used is produced in quite impressive rotary kilns
burning large amount of fossil fuel , the construction need great quantities of fuel for the Earth moving machinery
However once the Dam is in operation the CO2 foot print is minimal .

It's the typical massive investment upfront with return over decades ,

Dams can be beneficial to the environment , beside the new niche for aquatic life ,
it maintain soil moisture and ground water level for the area ,
avoid massive runoff and has a quite noticeable local temperature balance

Re: The Yin-Yang of Hydropower

Unread postPosted: Fri 27 Jan 2017, 19:35:50
by KaiserJeep
Hydropower dams that are well engineered can easily last between one and two centuries. Let me express my admiration for the "great" dams such as the Grand Coulee and the Hoover dams in our country, as well as the Three Gorges dam and others throughout the world.

However, there are lots of smaller dams where the destructive impacts seem to outweigh the benefits. IMHO building a dam that destroys a natural Salmon or Steelhead run is a crime. I am one of those fortunate few who have experienced having a vibrating graphite rod in my hand and a live Steelhead Trout on the line. All I will say about that is that it is enough to get one out of bed before light, and to wade into a chillingly cold river in the rain of Winter for fish.

But I am not a fanatic. I have caught a few salmon and trout in wild rivers, but most were in the nearby San Lorenzo river that terminates in the lagoon at Santa Cruz, and the fish come from a nearby hatchery which has also had me as a volunteer worker and fundraiser. Note that the San Lorenzo Steelhead run was 100% destroyed by habitat destruction in the 1930's when the redwoods were clearcut and housing and farms replaced them. The fish only exist today because trees were planted to restore the area and shade the water, and the fish hatchery was built. (The genetic strains of Steelhead were chosen from Northern California rivers.)

Given the choice between fish and electricity, I would choose fish. But I believe that dams can be designed, built, and operated today using computer simulation to minimize cost, to maximize electricity generation, and to keep riparian areas healthy with periodic sediment flows and real usable fish ladders around the dam where the fish can bypass the barrier imposed by the dam.

Re: The Yin-Yang of Hydropower

Unread postPosted: Tue 31 Jan 2017, 08:46:40
by diemos
yeah, they're great.

It's just that most of the low hanging fruit has already been plucked. Not much growth potential there.

Re: The Yin-Yang of Hydropower

Unread postPosted: Wed 01 Feb 2017, 08:46:11
by Zarquon

The Source Of All Knowledge says:
"Hydropower can be intermittent and/or dispatchable, depending on the configuration of the plant. Typical hydroelectric plants in the dam configuration may have substantial storage capacity, and be considered dispatchable. Run of the river hydroelectric generation will typically have limited or no storage capacity, and will be variable on a seasonal or annual basis (dependent on rainfall and snow melt)."

So hydropower is to some significant degree seasonally intermittent, different from wind & solar which are intermittent on an hourly basis. It gets interesting when the two intermittencies are combined, like with the Nordlink project: we send surplus German windpower to Norway, where it is either consumed or used to fill pump-storage reservoirs. We get it back when renewable output is low.

Transmission losses are said to be only 5%, but you'd need to add losses from pumping etc.

Re: The Yin-Yang of Hydropower

Unread postPosted: Wed 01 Feb 2017, 10:11:26
by KaiserJeep
It's not so much seasonably intermittent, as subject to drought. After 5 years of drought, we had hydropower in Northern California offline that had been online continuously for over a century. Now after one very wet year it is back online again. But by design a hydropower dam stores the wet season excess runoff and releases it slowly and steadily until the rains resume the following season. The five years of drought are very visible in the chart above.

We were formerly making up for the lack of hydropower energy by buying "green power" from Texas. In a strange way, the power market from Texas will be depressed by the rainy West Coast weather. The other thing that happened and is not ever changing back is that California finished an obsessive buildout of Solar residential rooftop PV, plus medium sized PV installations in parking lots, schools, and manufacturing facilities. We have virtually eliminated the kind of peak daytime power demands that resulted in the Enron scandal 25+ years ago. In fact, half the installed Solar PV in the entire USA is in California, and we are still building.

Re: The Yin-Yang of Hydropower

Unread postPosted: Wed 01 Feb 2017, 12:17:49
by joewp
Hold on a mintute, KJ:
Hydroelectric power's dirty secret revealed | New Scientist
The green image of hydro power as a benign alternative to fossil fuels is false, says Éric Duchemin, a consultant for the Intergovernmental Panel on Climate Change (IPCC). “Everyone thinks hydro is very clean, but this is not the case,” he says.

Hydroelectric dams produce significant amounts of carbon dioxide and methane, and in some cases produce more of these greenhouse gases than power plants running on fossil fuels. Carbon emissions vary from dam to dam, says Philip Fearnside from Brazil’s National Institute for Research in the Amazon in Manaus. “But we do know that there are enough emissions to worry about.”

In a study to be published in Mitigation and Adaptation Strategies for Global Change, Fearnside estimates that in 1990 the greenhouse effect of emissions from the Curuá-Una dam in Pará, Brazil, was more than three-and-a-half times what would have been produced by generating the same amount of electricity from oil.

This is because large amounts of carbon tied up in trees and other plants are released when the reservoir is initially flooded and the plants rot. Then after this first pulse of decay, plant matter settling on the reservoir’s bottom decomposes without oxygen, resulting in a build-up of dissolved methane. This is released into the atmosphere when water passes through the dam’s turbines.

There's no such thing as a free lunch when it comes to producing energy. :cry:

Re: The Yin-Yang of Hydropower

Unread postPosted: Wed 01 Feb 2017, 12:32:27
by KaiserJeep
You are correct, but a "good design" for hydropower also includes removing organics - including existing vegetation, downed wood, and structures from the impoundment area behind the dam. Then if water permeable soil exists, clay is often imported and tamped down to control water seepage, especially in earth-filled dams.

The rotting vegetation is gone in a few decades, and not any consideration at all in a dam over a century old. Nor does rotting even occur in many mountain lakes, from which people have salvaged 100+ year old "old growth" logs, dried them, and made beautiful furniture from the wood.

By today's standards, new hydropower is only green if all these precautions are taken. But existing hydropower is almost 100% constructed and quite old already.