The Sappi paper mill in Cloquet Minnesota produces most of the electricity it needs, using steam that also powers the industrial process. Sappi can even sell power when demand is high. Electric co-generation is enjoying a come-back. (Photo by Stephanie Hemphill)
More and mores states are establishing a “renewable energy standard”
for their electric utilities. So far, wind power is producing the bulk
of renewable energy. But there are other sources. Some are brand new.
Others have been around for a long time. Stephanie Hemphill reports:
Transcript
More and mores states are establishing a “renewable energy standard”
for their electric utilities. So far, wind power is producing the bulk
of renewable energy. But there are other sources. Some are brand new.
Others have been around for a long time. Stephanie Hemphill reports:
The first thing to know about electricity is that making it can be
incredibly inefficient.
In a conventional power plant, burning fuel turns water into steam.
The steam drives a turbine, which spins the generator. Only about a
third of the energy in the original fuel is converted to electricity.
Two thirds goes up the smokestack in the form of heat.
“Every time you convert energy from one form to another, you lose
something. That’s just the way it is, ’cause nothing’s perfect.”
Dwight Anderson works for Minnesota Power. He’s lived with that
inefficiency for his whole working life. Now, he’s trying to wring
more electric power out of every bit of fuel.
He’s high on something called co-generation. The basic idea is to
harness the heat or steam that normally goes up the smokestack.
There’s a good example of co-generation at the Sappi paper mill in
Cloquet, in northern Minnesota. Like many paper mills, Sappi makes
most of the electricity it needs.
Engineering Manager Rick Morgan points to a mountain of wood chips:
“We have about 20,000 tons of biomass stored.”
That’ll last less than a month. The plant uses 53,000 watts, enough to
power a small city.
Inside the sprawling buildings, there are several electric generators.
One of them is fueled by a recovery boiler, which burns the byproducts
of the paper-making process, to run steam through a turbine.
“…The actual turbine is manufactured in Czechoslovakia and the generator’s
made in Vestros, Sweden.”
Higher pressure steam spins the turbine to produce electricity. The
waste steam from the same boiler goes to the pulp dryer, the paper
machines, and other parts of the process.
Back in his office, Rick Morgan says energy is the fourth largest
expense for paper mills:
“If you can’t control energy costs in this business, you can’t be in
business.”
The main product here is paper, but sometimes Sappi sells electricity
too. That happened during a recent cold snap:
“The electric demand increases and the costs go higher and higher, to
the point that it’s financially feasible for us to generate power for
Minnesota Power.”
Opportunities to produce electricity turn up in some surprising places.
Like along natural gas pipelines. The pressure has to be boosted
periodically as the gas travels through the pipe. Compressors fueled
by the natural gas do that work, and normally they vent off waste heat.
But now in South Dakota, the waste heat is fueling small power plants.
They look like the barns and silos of a farm. The generator itself is
about the size of a truck.
Basin Electric Power Coop spokesman Daryl Hill says the plants are
owned and operated by an Israeli company, and the co-op buys the power:
“We get basically 22 megawatts of baseload for little investment.”
Other countries are leading in these approaches because their fuel
prices have been so high. As prices go up in the U.S., power producers
are finding ways to use more efficient technologies, and they’re
returning to old-fashioned ideas like combined heat and power. This is
a form of co-generation that was once common across the country.
A central electric plant uses its waste steam to heat buildings. Of
course, most people don’t want to live next to a coal-fired power
plant. But Neal Elliott, with the American Council for an Energy-
Efficient Economy, says with combined heat and power, cleaner fuels,
like natural gas, can become competitive:
“Use natural gas, but use it much more efficiently. And instead of
throwing more than half of the fuel value away, let’s do it with co-
gen.”
Elliott says combined heat and power and other forms of co-generation
could provide 20% of America’s electricity needs, and save on heating
fuel at the same time. And he says recovered energy generation like
along the natural gas pipelines could provide another 20%.
For the Environment Report, I’m Stephanie Hemphill.