In Praise of Cogeneration (Combined Heat and Power)

by S. Tom Bond on November 18, 2012

Beechurst Power Plant. Morgantown, WV

An idea that is on the fringes of the current debate about an appropriate energy future is the use of waste heat from electrical generation to supply heat for industry, business and residences. Called “cogeneration” or “combined heat and power” (CHP), the idea is to take advantage of the huge amount of heat in hot water that is left over from generating electricity.

In thermodynamics, heat and work are equivalent forms of energy. The fuel produces superheated steam, and heat is converted to work (making electricity, for example) as the steam is cooled to the boiling point of water and condenses. At this point the hot water is customarily discarded. That is the function of the characteristic hyperbolic cooling towers one sees with the power plant, in addition to the tall chimneys and coal pile. Making electricity involves a little over one-third of the energy produced by the fuel. Water leaves the turbine in the plant at temperature just below the boiling point.

This hot water produced generating electricity can be used to warm buildings and do other things if proper planning is done. About as much energy can be removed from the hot water as it cools to room temperature as was extracted from doing work. This could be used, for example, to save the fuel required for heating buildings.

Why haven’t we always done this? When the electrification era began cities were very dirty. Coal was the chief fuel for factories, businesses and homes, and burning was much dirtier with a lot of carbon going unburned into the air. Horses were still the main way to transport goods and people when they wanted to avoid walking. Streets were messy and flies were bad.

It was cheaper in terms of energy to build power plants in cities and move the coal on trains than to transport electricity in long distance power lines from the coal mines. However, the decision was made to leave the dirt of power generation in the country, near the mines.

Today cities are relatively cleaner, which encourages building power plants in the city. Not only is combined heat and power an energy saver on fuel, less expense is needed for transmission lines and distribution.

Distributing the heat to buildings can be done by installing hot water heat, a well known technology. It is very clean, and is easily regulated by the user. Using heat produced by cogeneration is much like using geothermal heat or other heat from natural hot water, such as is done in Iceland.

Cogenerated heat is an excellent opportunity for investment and jobs. The technology exists today to do it. The skills are available and it would be great for small business. It is a sure thing. All that is required is to change our way of thinking. As old electrical generating plants are retired, we need to build new cogenerating plants in or near cities.

In the short term at least, cogenerating electricity and space heating should rate up there with solar and wind as a fuel-reducing, earth-saving practice. Over half of the world’s population now lives in cities. Reducing energy use by one-third the amount used in generating electricity is something to seriously think about.

Note: The Beechurst power plant in Morgantown generates steam (in addition to electricity) from coal with the steam being piped to local buildings of WVU.  Low grade coal and limestone are trucked into the plant for use in the fluidized bed combustion boiler system and spent limestone with flyash is trucked to local dump sites 24 hours a day and 7 days a week.

>>> S. Tom Bond is a cattle farmer in Lewis County.  He formerly taught chemistry in the public schools and at Salem College, Salem, WV. >>>

Leave a Comment

Previous post:

Next post: