For many years, coal has supplied most of Nova Scotia’s electricity. Until 1999, our plants were supplied with coal mined in Nova Scotia, utilizing what was a local and economic resource. Today, government-run coal mining operations in the province are closed and most of the coal we use is sourced from international markets. NS Power purchases domestic coal if it is available, meets environmental requirements, and is competitively priced.
NS Power is required to manage air emissions within annual limits set by regulation. The provincial Air Quality Regulations specify compliance limits for sulfur dioxide, mercury, nitrogen oxide and greenhouse gases. NS Power uses a mix of lower sulphur/lower mercury coals to comply with annual allowances. Declines in the annual emission limits have reduced the amount of coal used to generate electricity over the years. In addition, the Renewable Electricity Regulations require that 25% of NS Power’s annual energy sales be from renewable generation in 2015 and 40% by 2020. In 2015, coal accounted for 55.9% of the electricity used by Nova Scotians, down from as much as 80% in 2006. It is expected to account for 38% of generation in 2020.
The Point Aconi station is equipped with fluidized bed technology capable of removing a high percentage of sulphur dioxide and mercury emissions. That means this plant is able to consume a high percentage of petroleum coke, a bi-product of the oil refining industry, as well as coal.
Pet coke has a high heating value compared to coal and is usually lower cost than coal which makes it a beneficial fuel for us to use. Pet coke is used periodically in small amounts in the boilers at Lingan, Point Tupper and in Trenton 6. Point Aconi, however, was designed to use it, so it has the capability to handle larger quantities due to its fluidized bed technology.
We operate four plants that use coal or pet coke in Nova Scotia: Lingan, Point Tupper, Trenton and Point Aconi.
Natural gas is considered cleaner than other fossil fuels like coal and oil because it produces fewer air emissions. Around the world, it is found in reservoirs under the earth while in Nova Scotia, it's found under the ocean floor and supplied through a pipeline that leads to our Tufts Cove Generating Station in Dartmouth. The plant can burn oil or natural gas to generate electricity, but economical prices in recent years have led to it being run primarily with gas.
Because we’re producing so much electricity using natural gas at Tufts Cove – 21% of the province’s needs in 2012, up from 3% in 2006 – we’re making less power using coal at our plants, resulting in lower emissions and electricity costs.
Waste Heat Recovery
The Tufts Cove Waste Heat Recovery project added a sixth generator to the plant in 2011 that produces up to 50 MW of electricity, enough to power up to 35,000 homes.
The new equipment captures waste heat from the exhaust streams of the two natural gas combustion turbines and uses it to power a new steam turbine and generator set, generating 25 MW of electricity without any additional fuel or emissions. A second 25 MW is generated by burning gas added directly into the waste heat stream from the turbines to increase energy output even further.
Until the 1970s, most of Nova Scotia’s electricity was generated by burning oil. In the wake of the OPEC oil crisis, the government decided to switch from imported oil to Cape Breton coal as Nova Scotia’s primary source of electricity.
Today, oil supplies only a small amount of Nova Scotia’s electicity. The Tufts Cove Generating Station in Dartmouth is designed to burn either oil or natural gas, but due to low prices in recent years has run primarily on gas.
We also operate three oil-fired combustion turbine units, located in Victoria Junction (66 MW), Tusket (24 MW) and Burnside, Dartmouth (132 MW). Because they burn expensive light fuel oil and tend to be less efficient than other thermal generating units, the turbines typically serve as a secondary source of generation and are not commonly used. Oil supplied 0.1% of Nova Scotia’s electricity in 2012.