Hydroelectric Dams can’t make Electricity if it doesn’t Rain

Posted by PITHOCRATES - July 21st, 2012

Week in Review

Some people like to think that renewable energy is the energy of the future.  And that it will be free and abundant.  But with today’s technology it is none of these things.  It is just too unreliable.  And has such low capacity factors (CF).  The CF is a rating we calculate by dividing actual power produced by the amount possible under ideal conditions over a period of time.  Solar panels have a CF of about 20% because there are nights and cloudy days.  Wind farms have a CF of about 30% because there are times the wind doesn’t blow.  Big hydroelectric dams have a CF of about 50%  because there are times when it doesn’t rain (see Erratic monsoon clouds hydro power generation by Sadananda Mohapatra posted 7/18/2012 on the Business Standard).

Hydro power generation in the state may decline over the next couple of weeks due to erratic and deficient monsoon…

Daily generation from seven hydro power plants in the state reached up to 722 MW this week, up from 210 MW in early June. However, as the monsoon rainfall has been below normal so far, power managers feel this could hurt generation in coming days.

“All reservoirs, except Burla, have water levels below or at par with (MDDL) Minimum Draw Down Level. The generations had gone up on expectation of better rainfall, but it has to come down as rainfall has not been satisfactory,” said a senior official of state-run power trader Gridco…

Even though hydro power generation does not contribute significantly to meet the state’s power demand, cash-strapped Gridco depends on it heavily due to its low cost and easier availability. This summer, thermal units operating in the state had to shut down operations frequently due to technical glitch or coal supply problems, compelling the power trader to look for other sources such as captive power plants.

Fossil fuel-fired plants may not be as clean as the renewable energies but they are more reliable.  With capacity factors in excess of 90%.  As long as they aren’t broke.  Or run out of fuel.  Things we can minimize with proper maintenance.  And a sound energy policy.  One that encourages the extraction of fossil fuels from the ground.  Even with this though these plants can go off line because they only have a CF of about 90%.  And sometimes that 10% happens.

Of the renewable energies hydroelectric is the one with the most commercial potential.  A mix of coal and hydro can go a long way in meeting a nation’s energy needs.  One that normally works in India.  When the rains cooperate.  Which they sometimes don’t.  Which limits their capacity factor.  For if the water in the reservoir isn’t high enough it can’t spin those water turbines fast enough.  Or long enough.  And if it falls too low it may not even be able to enter the water inlets that feed those water turbines.  A prolonged dry spell could shut a hydro dam down completely.  Something you never have to worry about with coal.

Renewable energy can help.  But it just can’t replace fossil fuel-generated electric power.  For nothing is more reliable.  Which is a comforting fact when you head home after a tiring day at work.  Knowing that the electricity-provided creature comforts you so enjoy will be there waiting for you.  Thanks in large part to coal.  With the occasional assist from hydroelectric power.

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