Solid Waste & Recycling

Feature

Talking 'bout Cogeneration

Even though the burning of oil, natural gas and coal may not be considered the most efficient sources of energy, the use of fossil fuels to generate power is the most common source of electricity in N...


Even though the burning of oil, natural gas and coal may not be considered the most efficient sources of energy, the use of fossil fuels to generate power is the most common source of electricity in North America. The major problem with the efficiency of electricity generated by the burning of fossil fuels is the amount of energy lost, through waste heat.

However, companies and independent power producers are working on improved methods of energy generation to increase this efficiency dramatically. By capturing the heat exhausted from a turbine, waste heat can be reduced by 40 to 45 per cent. By combining a steam generator with the turbine, the captured waste heat and the electrical output — in a process called “Cogeneration” or “Combined Heat and Power (CHP)” — can increase the thermal efficiency of oil, gas, coal, or whatever fuel is used by up to 70 per cent.

One form of cogeneration uses biogas and biomass fuel from waste products and thereby offers a one-two punch as an alternative to conventional sources of energy and waste management option. The alignment of these exciting technologies finally makes the long-sought-after energy-from-waste concept viable.

“The barriers to CHP are capital investment costs, generator licenses, and environmental regulations,” explains Peter Ronson, account manager at Toromont Energy, a subsidiary of Toromont Industries Ltd. On the positive side, de-regulation of energy markets facilitates small power generators to add to the overall electricity mix. However, Mr. Ronson notes that the public’s acceptance of energy alternatives is slower than many would like.

“Industry typically wants a return on investment (ROI) in about 18 months to two years. The average project has a ROI of between six and eight years. Unless there is a champion within the organization pushing the concept, or unless regulations and tax incentives help lower the costs (as in the U.S.), companies and local government bodies have to accept a longer return on investment,” states Mr. Ronson.

Current installations

Cogen accounts for seven per cent of electricity produced in the U.S. Some two hundred hospitals and one hundred university campuses have invested in CHP. In Canada, CHP has made more modest inroads. The Ottawa Health Sciences Centre supplies electricity, steam, hot water and chilled water to member institutions. The Sudbury Regional Hospital is fed by the Sudbury District Energy Corporation, which provides 6.7 MW of power generation. Additional electricity is exported to Greater Sudbury Utilities. The City of Cornwall, London Health Sciences, Brock University in St. Catharines, and York University in Toronto are other centres of cogeneration, to name a few.

Hamilton Community Energy, a business unit of Hamilton Utilities and 100 per cent owned by the City of Hamilton, recently launched a 12 MW thermal and 3.5MW electricity CHP plant adjacent to a high school feeding 124 degree Celsius water through a series of underground pipes to eight buildings up to 1.5 km from the plant. The electricity will be used by the city (useful in a power outage or ice storm) with any excess sold to the public grid.

Robert Desnoyers, president of Hamilton Community Energy notes, “At this point there is a lot of interest but not a lot of commitment. The concept is not a slam-dunk in North America. Homeowners, for example, don’t want to give up control of their heating. Our goal is to tie into our commercial and industrial neighbours.”

While urban projects continue to develop using natural gas as a fuel, isolated projects use whatever fuel is available to create electricity and heat. For example, Bear Creek, Alberta, about 10 km from Grande Prairie, uses waste wood from the nearby Weyerhaeuser pulp mill to fuel a combustion turbine to produce steam and electricity. At Petro-Canada’s MacKay River oilsands development, 60 km northwest of Fort McMurray, cogen provides 165 MW of electricity and 720 tonnes/hour of high-pressure steam for use in the company’s steam injection wells.

Rahr Malting Co. of Shakopee Minnesota, produces 50,000 tons of biomass by-product annually from its barley malting plant. This can generate 7,500 BTUs per lb. Rahr is in the process of building a 20MW-energy plant, enough electricity for 11,000 homes.

Cogen and waste facilities

Municipalities have other factors that drive them to look at alternative sources of energy. Aging landfill sites pose both a problem and an opportunity. Methane, a potent greenhouse gas, is often just burned off to eliminate odour and yet has similar properties to natural gas as a fuel. With improvements in technologies such as anaerobic digesters and methane extraction, biomass (organic material and sludge from wastewater treatment) and biogas (usually methane) have drawn interest as sources of fuel.

Maxim Power Corporation has built a 5.6 MW landfill-gas-fuelled cogeneration plant in Delta, B.C. With methane gas being delivered via a three kilometre pipeline from the City of Vancouver’s landfill, the plant will supply electricity to B.C. Hydro under a 20-year contract and recovered heat will be delivered to the CanAgro greenhouse to support tomato growing operations.

The Region of Waterloo operates two landfill sites, both feeding the captured methane into cogeneration projects.

“It’s never easy to use gas collected from landfill,” admits Dave McCaughan, Supervisor of Environmental Systems for the Region of Waterloo. “The system requires a lot of monitoring, time and energy. The hill constantly moves as the site settles, but all landfills require a high level of maintenance. The main benefits are turning waste methane into useable fuel. It becomes a source of revenue rather than just an expense.”

Waterloo sends methane gas to Curtis Steel in Cambridge to heat its reheating furnaces and the electricity generated by a turbine is sold to the wholesale electricity market.

“At some point the economics will favour projects such as landfill gas to energy,” says Toromont’s Peter Ronson. “Up to now it’s been challenging and there have been failures in the past, but we feel there is a growing market and the benefits are encouraging.” Mr. Ronson and many others in this growing sector feel that as the strain on the existing power generators increases and as alternatives to natural gas are introduced, cogeneration using waste materials and landfill gas will become more common place.

(See “Final Analysis: Energy Opportunities” in the June/July 2002 edition.)

Lawson Hunter is a freelance writer and publisher of Renewable Energy eNewsletter, based in Burlington, Ontario. E-mail Lawson at lawson@newsandcomment.com


Print this page

Related Posts



Have your say:

Your email address will not be published. Required fields are marked *

*