Turbine project a worthy pursuit
Submitted by OCAA on Sun, 04/08/2007 - 23:30.
The Toronto Star
The parking lot at the Toronto headquarters of Enbridge Gas Distribution Inc. is currently a construction zone.
It's also the location of a natural gas letdown station, one of 2,200 scattered across the company's provincial pipeline system.
Such stations are important. Tremendous pressures are needed to move the gas over long distances through the pipeline. When the gas reaches a specific community, the pressure must be reduced or "let down" – essentially, it's squeezed through a valve – before it can be safely distributed to individual homes and businesses.
It's similar to the electricity system, which has a backbone of 500-kilovolt transmission lines that step down to medium-voltage lines and eventually become lower-voltage distribution lines that feed our homes with 120 volts. Believe me, you don't want 500 kilovolts coming into your home.
In the context of pipelines, you also don't want high-pressure gas coming into your home. The problem is, when pressure is reduced at a letdown station the energy that's released is just lost – like letting air out of a balloon.
So why is Enbridge's parking lot a construction zone? The company is installing what it calls a "turbo expander" at the letdown station there. It's essentially a small, highly efficient turbine created by a French company called Cryostar SAS.
Instead of squeezing the gas through a valve to reduce pressure, the gas is forced through the turbine. Pressure is still reduced, but instead of losing the energy, it spins the turbine and generates clean electricity. I say "clean" electricity because there's no burning of fossil fuels, only the use of energy that would otherwise be wasted.
"We decided we should try to create our own destiny and promote technologies that are aligned with our core business," says Chuck Szmurlo, vice-president of energy technology and power generation with parent company Enbridge Inc. in Calgary.
But Enbridge isn't stopping there. It wants to complement the turbo expander with fuel-cell technology, from a U.S. company called FuelCell Energy Inc., which efficiently converts natural gas to electricity through an electrochemical reaction. Again, no fuel is burned.
Why is a fuel cell needed? Turns out when pipeline pressure is reduced, the gas cools down and ice crystals can form around the pipes that could cause damage to roads and other municipal infrastructure. The de-pressurized gas must be warmed up again before it goes to customers. Typically, heat is supplied by burning some of the natural gas in a boiler – meaning the release of carbon dioxide and some smog-causing emissions.
When the boiler is replaced with a fuel cell, you get three benefits. First, you generate electricity from the natural gas that goes through the fuel cell. Second, the fuel cell generates by-product heat that can be used to warm up the gas at the letdown point. Third, the higher efficiency of the fuel cell means you produce relatively lower CO2 emissions and near-zero smog emissions.
"The integration of these two devices, we believe, represent the most efficient power plant for converting natural gas to electricity," says Dave Teichroeb, who heads business development for fuel-cell markets at Enbridge.
He figures the turbo expander could produce up to 1 megawatt of electricity and the fuel cell could generate another 1.2 megawatts of power at the parking lot site. In total, we're talking 2.2 megawatts – enough electricity to power 1,500 homes. It's also power when you need it, not intermittent power like that produced by wind energy.
If the demonstration project is a success, the company plans to scale it up to 10 megawatts at another letdown station. Teichroeb figures, initially, that up to 60 megawatts of clean electricity could be economically produced from between 12 and 18 stations across Enbridge's pipeline. That's assuming the company can sell the electricity back to the province for 11 cents per kilowatt-hour, the same amount it currently pays for wind.
"We believe that this hybrid plant is competitive with wind generation, and it does add that element of predictable supply," says Teichroeb, adding that smaller letdown stations could also be retrofitted as the cost of the technologies falls.
Later this month, the Ontario Power Authority is expected to release draft rules for a standard offer program for "clean" energy, similar to the one already in place to spur development of small-scale renewable energy project.
The new program is meant to set a price for power that comes from energy-from-waste facilities, combined heat and power systems and, Enbridge hopes, its hybrid fuel cell/turbo expander system – what you could call "low-carbon" technologies.
But Ontario is merely a starting point. "There are thousands of opportunities around the world," says Szmurlo. "But we have to demonstrate that this technology works in our own backyard. Simultaneously, we're going to be exploring the possibility of deploying this technology elsewhere, first in the U.S. and then more broadly."
It's a worthy pursuit, one that can establish Ontario as a leader in a new clean-energy field while helping the province lower its CO2 emissions.