Energy Efficiency of Fossil Fuel Power Generation

According to a Dutch study, Australia, China, France, Germany, India, Japan, Nordic countries, South Korea, United Kingdom, Ireland, and United States are responsible for 65% of worldwide fossil fuel-fired power generation.  The average efficiencies of power generation are 35% for coal, 45% for natural gas and 38% for oil-fired power generation.  What this means is that 35% of the energy in coal results in electric power, the rest goes "up the stack" as heat.  the highest efficiencies observed are 42% for coal, 52% for natural gas and 45% for oil-fired power generation.  If all countries produced electricity at the highest possible efficiencies, it would reduce annual CO₂ emissions by 860 million metric tons.  The Department of Energy in the US estimates that if US power grid  were just 5% more efficient, the energy savings would equate to permanently eliminating the fuel and greenhouse gas emissions from 53 million cars.

I mentioned in a previous blog post, that sugar cane is arguably the World's most successful alternative fuel.  The energy balance (ratio of energy produced to input energy) of sugar cane ethanol is 8.3 to 10.2 and it is estimated that the CO₂ emission reduction is 86-90% compared to gasoline.  For comparison the energy balance of corn ethanol produced in North America is 1.3 to 1.6, and a University of Minnesota study concluded that corn ethanol may be worse for air quality than gasoline.

The reason that sugar cane ethanol is so much more efficient than corn ethanol or gasoline is that the energy in the bagasse (residual from sugar cane) that might otherwise have been wasted is used productively, some for distilling the ethanol and the remainder to generate electric power (cogeneration).  According to Frost & Sullivan, power generation from bagasse reached 3.0 GW in 2007, and it is expected to reach 12.2 GW in 2014. In 2008 sugarcane bagasse cogeneration produced 3.0% of total Brazilian energy power generation.

In the US in 2008 49% of electric power generation was produced in coal-fired power plants, and a recent study by the Department of Energy suggests given current policies this is not going to change rapidly in the future.  However, there is a way to improve the efficiency of fossil fuel power generation plants without replacing them.  In New York City, Con Edison distributes steam heat from its seven cogeneration plants to 100,000 buildings in Manhattan, which is the the largest steam district in the world. At peak this corresponds to about 2.5 GW.  The European Union currently generates 11% of its electricity using cogeneration and Europe has the three countries with the world’s most intensive cogeneration economies: Denmark, the Netherlands and Finland.  For example, 53% of Denmark's electric power is derived from fossil fuels.  But instead of sending the heat up the stack, in Denmark it is used for district heating.  Combined heat and power (CHP) plants are responsible for 81% of district heating in Denmark.  The most efficient of Denmark's CHP plants claim 90% fuel efficiency. 

Comments

[Zenon Todorski President]

Hdro-Themal turbine converts heat energy into kinetic energy of water to generate mechanical power, this yields twice as much mechanical energy as a steam turbine can genrate.
Zen Todorski President Dhom Co Ltd

[W.Ross Williams]

A month or 3 ago, you posted a chart showing the net energy that actually made into usable energy. Could you post that again or send me a link to it? I would be most grateful.

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