A Renewable Boom means more Expensive and Less Reliable Electric Power

Posted by PITHOCRATES - October 20th, 2013

Week in Review

The news on our green energy initiatives sounds good.  We’re importing less oil.  And adding more and more wind power.  If you’re a proponent of green energy you no doubt are pleased by this news.  But if you understand energy and economics it’s a different story.  You’ll think the country is moving in the wrong direction.  Ultimately raising our energy costs.  Without making much of an impact on carbon emissions.  And just because we are exporting gasoline doesn’t mean we’re on the road to being energy self-sufficient (see The Renewable Boom by Bryan Walsh posted 10/11/2013 on Time).

Earlier this year, the U.S. became a net exporter of oil distillates, and the International Energy Agency projects that the U.S. could be almost energy self-sufficient in net terms by 2035.

This is not necessarily a good thing.  Being a net exporter of oil distillates.  It means that US supply exceeds US demand at the current market price.  That’s an important point.  The current market price.  The US has been in an anemic economic recovery—though some would say we’re still in a recession—since President Obama assumed office.  During bad economic times people lose their jobs.  Those who haven’t are worried about losing theirs.  And they worry about the uncertainty, too, about the cost of Obamacare.  So people are driving less.  And they are spending less.  Because they have less.  And worry about how much money they’ll need under Obamacare.  So they’re not taking the family on a cross-country vacation.  Some are even spending their vacation in the backyard.  The so called ‘staycation’.  No doubt the 10 million or so who disappeared from the labor force since President Obama assumed office aren’t driving much these days.  So because of this US demand for gasoline is down.  And, hence, prices.   Even though gasoline prices are still high and consuming an ever larger part of our reduced median family income (also down since President assumed office), gasoline prices are higher elsewhere.  Which is why refineries are exporting their oil distillates.  To meet that higher demand that has raised the market price.

But the biggest source of new electricity in the U.S. last year wasn’t a fossil fuel. It was the humble wind. More than 13 gigawatts of new wind potential were added to the grid in 2012, accounting for 43% of all new generation capacity. Total wind-power capacity exceeded 60 gigawatts by the end of 2012—enough to power 15 million homes when the breeze is blowing.

These numbers do sound big for wind.  Like it’s easy sailing for wind power to replace coal.  But is it?  Let’s look at the big picture.  In 2011 the total nameplate capacity of all electric power generation was 1,153.149 gigawatts.  So that 13 gigawatts though sounding like a lot of power it is only 1.127% of the total nameplate capacity.  Small enough to be rounding error.  In other words, that 13 gigawatts is such a small amount of power that it won’t even be seen by the electric grid.  But it gets even worse.

We used the term ‘nameplate capacity’ for a reason.  This is the amount of power that this unit is capable of producing.  Not what it actually produces.  In fact, we have a measure comparing the power generation possible to the ‘actual’ power generation.  The capacity factor.  Which measures power production over a period of time and divides it by the total amount of power that the unit could have produced (i.e., its nameplate value).  Coal has a higher capacity factor than wind because coal can produce electric power in all wind conditions.  While wind power cannot.  If the winds are too strong the wind turbines lock down to protect themselves.  If the wind is blowing too slowly they won’t produce any electric power.

The typical capacity factor for coal is 62.3%.  Meaning that over half of the installed capacity is generating power.  Some generators may be down for maintenance.  Or a generator may be shut down due to weak demand.  The typical capacity factor for wind power is 30%.  Meaning that the installed capacity produces no power 70% of the time.  And it’s not because turbines are down for maintenance.  It’s because of the intermittent wind.

So coal has twice the capacity that wind has.  Does this mean we need twice the installed capacity of wind to match coal?  No.  Because if you tripled the number of wind turbines in a wind farm they will still produce no power if the wind isn’t blowing.  In this respect you can say coal has a capacity factor of 100%.  For if they want more power from a coal-fired power plant they can bring another generator on line.  Even if the wind isn’t blowing.

You could say wind power is like parsley on a plate in a restaurant.  It’s just a garnishment.  It makes our electric power production look more environmentally friendly but it just adds cost and often times we just throw it away.  For if coal provides all our power needs when the wind isn’t blowing and the wind then starts blowing you have a surplus of power that you can’t sell.  You can’t shut down the coal-fired power plant because the wind turbines don’t produce enough to replace it.  You can’t shut down the wind turbines because it defeats the purpose of having them.  So you just throw away the surplus power.  And charge people more for their electric power to cover this waste.  Like a restaurant charges more for its menu items to cover the cost of the parsley the people throw away.



Tags: , , , , , , , , , , , , , , , , , , , ,

Wind Turbines versus a Coal-Fired Power Plant

Posted by PITHOCRATES - August 26th, 2013

Economics 101

The Diameter of a 6 Megawatt 3-Blade Rotor is Greater than two 747-400s parked Wingtip to Wingtip

One of the largest coal-fired power plants in the world is in Macon, Georgia.  Plant Scherer.  Whose furnaces consume some 31,000 tons of coal a day.  Producing 3,500 megawatts of electric power.  Enough to power three good sized American cities.  A few million households.

One of the largest offshore wind turbines available on the market is 6 megawatt.  Which is huge.  One blade can be as long as 250 feet.  A typical 3-blade rotor can have a diameter of just over 500 feet.  To get a feel of this magnitude the wingspan of the world’s most common jumbo jet, the Boeing 747-400, is about 211 feet.  Which means one blade of a 6 megawatt wind turbine is longer than the wingspan of a Boeing 747-400.  And the diameter of a 3-blade rotor is greater than two 747-400s parked wingtip to wingtip.

A 6 megawatt wind turbine requires a tower of about 300 feet tall.  So the blades can spin without hitting the ground.  Which is about the same height of a 20 story building.  And if it’s an offshore turbine you can add another 2 stories or so for the tower below the surface of the water.  So these things are big.  And tall.  Some of the largest manmade machines built.  And some of the most costly.  It takes a huge investment to install a 6 megawatt wind turbine.  That can only produce 0.171% of the electric power that Plant Scherer can produce.

There is a Small Window of Wind Velocities that we can use to Generate Electric Power with Wind Turbines

So how many 6 megawatt turbines does it take to match the power output of Plant Scherer?  Well, to match the nameplate capacity you’ll need about 584 turbines.  If we install these offshore in a line that line would extend some 56 miles.  About an hour’s drive time at 55 mph.  Which is a very long line of very large and very costly wind turbines.

We said ‘nameplate capacity’ for a reason.  If 584 wind turbines were spinning in the right kind of wind they could match the output of Plant Scherer.  And what is the right kind of wind?  Not too slow.  And not too fast.  These turbines have gear boxes to speed up the rotational speed of the rotors.  And they vary the pitch of the blades on the rotors.  So the turbine can keep a constant rotational input to the electric generator.  If the wind is blowing slower than optimum the blades can catch more air to spin faster.  If the wind is blowing pretty strong the blades will turn to catch less air to spin slower.

In other words, there is a small window of wind velocities that we can use to generate electric power with wind turbines.  Too slow or no wind at all they produce no power.  If the wind is too great the blades turn parallel to the wind.  So the wind blows across the blades without turning them.  They also have brakes to lock down the rotors in very high winds to prevent any damage.  So if a storm blows through 584 offshore turbines they’ll produce no electric power.  Which means they can’t replace a Plant Scherer.  They can only operate with a Plant Scherer in backup.  To provide power then the winds just aren’t right.

The more Wind Turbines we install the more Costly our Electric Power Gets

Now back to that nameplate capacity.  This is the amount of power a power plant could produce.  It doesn’t mean what it will produce.  The capacity factor divides actual power produced over a period of time with the maximum amount of power that could have been produced.  A coal-fired power plant has a higher capacity factor than a wind turbine.  Because they can produce electricity pretty much whenever we want them to.  While a wind turbine can only produce electricity when the winds are blowing not too slow and not too fast.

So, if the winds aren’t blowing, or if they’re blowing too strongly, it is as if those wind turbines aren’t there.  Which means something else must be there.  Something more reliable.  Something that isn’t weather-dependent.  Such as a Plant Scherer.  In other words, even if we installed 584 turbines to match the output of Plant Scherer we could never get rid of Plant Scherer.  Because there will be times when those windmills will produce no power.  Requiring Plant Scherer to produce power as if we never had installed those wind turbines.  And because it takes time to bring a coal-fired power plant on line it has to keep burning coal even when the wind turbines are providing power.  So it can be ready to provide power when the windmills stop spinning.

Wind may be free but 584 wind turbines cost a fortune to install.  And this investment is in addition to the cost of building, maintaining and operating a coal-fired power plant like Plant Scherer.  All of which the consumer has to pay for.  Either in their electric bill (adding a surcharge for ‘clean energy investments’).  Or in higher taxes (property tax, income tax, etc.) that pays for renewable energy grants and subsidies.  Which means the more wind turbines we build the poorer we get.  Because we have duplicate power generation capacity when a single power plant could have sufficed.



Tags: , , , , , , , , , , , , ,