Anyone interested
in the important issues around global climate change quickly comes to
appreciate that the modes of energy generation vary greatly with respect to the
extent to which they contribute to global warming.
Fossil fuels
make the largest contribution to global warming for a given amount of energy
produced, because greenhouse gases are formed as the fuels are burned, as in
coal-fired or natural gas fired power plants that generate electricity. Fossil fuels of course also power cars, trucks
and other things. Ethanol, a component
of automobile gasoline is in the same league; not only is carbon dioxide
produced when ethanol is burned, enormous amounts of energy, mostly derived
from fossil fuels, is needed to produce the ethanol. The notion that ethanol is
a renewable source of energy is a distraction. True, it is a plant product; carbon
dioxide was taken from the atmosphere by the corn plants. But the expenditure
of all the energy required to get it to the gas pump, and the environmental
costs of producing the corn and getting ethanol from it, more than null out that
argument.
The urgent
need to reduce emissions of carbon dioxide drives the effort to replace fossil
fuels with alternative sources of energy. We speak of renewable sources, but what does that mean? Renewable
energy is generated from natural
processes that are continuously replenished, such as sunlight, wind, oceanic
tides. It's common to include biomass such as wood, plants such as corn or soy
and other crops in this category, but the points I made with respect to ethanol
apply to many of these sources as well.
If we had a
government more inclined to advance the long-term welfare of the people who put
their faith in it, we would have continuing, substantial investments in
developing newer, more effective means of generating renewable energy. Unfortunately,
government often gets in the way of progress. Nonetheless, the private sector
has made substantial advancements in achieving ever more efficient conversion
of sunlight into electrical energy, and more efficient and environmentally friendly
wind generators. If we could get certain
state governments to enact progressive policies and regulations for deploying
solar panels more extensively, we could be even farther along than we are. What is clear is that the technologies of
both solar and wind power are making huge gains. Our dependence on fossil fuels is shrinking
steadily, despite powerful corporate and political fossil fuel interests bent
on slowing progress.
But, we have yet a long way to go, and there
remains one big problem with both wind and solar: the wind doesn’t always blow,
and the sun sometimes is not to be seen.
It is devilishly difficult to store electrical energy in large
quantities so that it can be used later.
Rechargeable batteries might seem like a good solution, but on a large
scale, it just isn’t going to work. We
need energy sources that are capable of getting us through the night, as it
were. Of course, the sun’s always shining somewhere, and the wind’s always
blowing somewhere, but transport of electricity across long distances is
difficult, and has its own environmental challenges.
Until now,
the two major alternatives to fossil fuels have been hydroelectric and nuclear
power. Each of these deserves a discussion. In this blog I’ll confine my
comments to hydropower, as it’s commonly called.
Despite increased deployment of solar and wind power generation, hydropower is the largest
source of renewable energy worldwide. You get it by creating a large basin,
placing a dam at the outlet end of it, and using the energy created by the
water’s fall from the top of the dam to the lower level to generate
electricity. As long as we can keep
enough water in the basin, and a suitable flow for the water once it’s gone
over the top, we should be good. But
there are problems, starting with the fact that the land required to form the
basin sometimes displaces people and is taken out of use for food production. Nevertheless,
power-hungry China has
already built more than 200 gigawatts of hydroelectric power generation, and
another 230 gigawatts is under construction, development or permitting. Taken together this amounts to the capacity
of about 85 of the largest coal-fired power plants ever built. Other Asian
nations, especially India, are following China’s lead.
In the US,
hydropower has long been the most important renewable source of electricity. It’s interesting in light of this fact that
the US is low on the list of nations with large dam projects. Worldwide, according to size, Grand Coulee Dam is #7, and only 5 other US dams are on the
list of the top 70. Many of our
largest ones have been controversial in terms of their impacts on the
environment and the uses of precious water resources affected
by their presences. Hoover dam and Lake Mead, its associated water reservoir, is one of the earliest and largest dam projects. The dam was completed during the 1930s, and
is still the 6th largest hydroelectric facility in the US. This project
is often in the limelight because of the heavy demands made on Lake Mead, the
biggest reservoir in the Colorado River
system that irrigates Southern California crops and provides drinking water to
some 40 million people. A protracted
drought in the Southwest has resulted in a drop of more than 140 feet in the
lake’s level, to 1080 feet above sea level.
In January 2017, Hoover dam was operating at about only 39 percent of
capacity. Improvements in the design of
the turbines will make it possible to operate the dam at lake levels as low as
950 feet, but competition for the water will be vicious.
The example of Hoover dam illustrates
the connection between hydropower and global climate
change. A signature characteristic of global warming is drought in many of the world's settled regions. The Yangtze,
China’s longest river, is at its lowest level in the history of recording it. There
are water
shortages in many parts of China, affecting agriculture and the availability
of water for human consumption. What happens
when there’s not enough to sustain needed water levels for the big new dams? Hydropower
is a renewable source of energy in that the water it requires is transported
globally by the global climate machine, driven by solar energy, that ultimately
moves water from tropical regions toward the poles. The workings of that
machinery are being altered by global warming, with results that may be dire
for humankind.
Before we leave the topic of hydropower,
here’s another problem: dams
accumulate silt over time and lose their effectiveness as power sources if
that sediment is not removed. Add up all the existing and potential problems,
and it’s clear that hydropower is far from a panacea for our energy needs. Life
can be difficult! The next blog I post will concern itself with the vexing pros and cons of nuclear power. There's some interesting stuff going on in this area.
No comments:
Post a Comment