Availability A measure of time, expressed as a percentage of continuous operation 24 hours a day, 365 days a year that a generating unit is capable of generating electricity, regardless of whether or not it is actually generating electricity.
Baseload The minimum amount of power that we must make available to customers.
Biomass Plant matter used as a source of energy.
Blow down The process of opening a valve in a steam boiler to expel sediment that has collected.
Boiler A device for generating steam for power, processing or heating purposes or for producing hot water for heating purposes or hot water supply. Heat from an external combustion source is transmitted to a fluid contained within the tubes of the boiler shell.
Bottom ash A non-combustible by-product of coal combustion.
Btu (British Thermal Unit) A measure of energy. The amount of energy required to raise the temperature of one pound of water one degree Fahrenheit, when the water is near 39.2 degrees Fahrenheit.
Cap and trade Emissions trading.
Capacity The rated continuous load-carrying ability, expressed in megawatts, of generation equipment.
Carbon capture and storage (CCS) An approach to mitigating the contribution of greenhouse gas emissions to global warming, which is based on capturing carbon dioxide emissions from industrial operations and permanently storing them in deep underground formations.
Cenospheres A lightweight, inert, hollow sphere filled with inert air or gas produced as a by-product of coal combustion.
CO2 emissions intensity Amount of carbon dioxide emitted per MWh produced.
Coal gasification The conversion of solid fuel to gaseous form, for subsequent conversion into power, synthetic gas, hydrogen or a variety of other chemical products.
Cogeneration A generating facility that produces electricity and another form of useful thermal energy (such as heat or steam) used for industrial, commercial, heating or cooling purposes.
Combined cycle An electric generating technology in which electricity is produced from otherwise lost waste heat exiting from one or more gas (combustion) turbines. The exiting heat is routed to a conventional boiler or to a heat recovery steam generator for use by a steam turbine in the production of electricity. This process increases the efficiency of the electric generating unit.
Decommission To remove from service.
Derate To lower the rated electrical capability of a power generating facility or unit.
Disabling injury frequency rate The number of lost time injuries per 200,000 hours worked.
Emissions Substances released to the environment through industrial operations. For the fossil-fuel-fired power sector, the most common emissions to air are sulphur dioxide, oxides of nitrogen, mercury and greenhouse gases.
Enhanced oil recovery (EOR) A method of recovering oil by injecting, in the instance of TransAlta’s carbon capture and storage demonstration project, gas.
Exceedance An instance in which an action, activity or substance exceeds a limit set by regulations or permits.
Expected capability Plant capacity after consideration of station service use, planned outages, forced and maintenance outages, and derates.
Fly ash Fine particulate ash recovered as a by-product of coal combustion.
Geothermal plant A plant in which the prime mover is a steam turbine. The turbine is driven either by steam produced from hot water or by natural steam that derives its energy from heat found in rocks or fluids at various depths beneath the surface of the earth. The energy is extracted by drilling and/or pumping.
Gigajoule (GJ) A metric unit of energy commonly used in the energy industry. One GJ equals 947,817 BTU.
Gigawatt (GW) A measure of electric power equal to 1,000 megawatts.
Gigawatt hour (GWh) A measure of electricity consumption equivalent to the use of 1,000 megawatts of power over a period of one hour.
Greenfield Asset A new electric power generating facility built from the ground up on a new site.
Greenhouse gas (GHG) Gases having potential to retain heat in the atmosphere, including water vapour, carbon dioxide, methane, nitrous oxide, hydrofluorocarbons and perfluorocarbons.
Heat rate A measure of conversion, expressed as BTU/MWh, of the amount of thermal energy required to generate electrical energy.
Injury frequency rate (IFR) The number of medical aid, lost time and fatal injuries per 200,000 hours worked.
Intensity A measure of emissions per Mwh produced.
Lost time injury An injury in which the worker is absent beyond the day of the injury.
Megawatt (MW) A measure of electric power equal to 1,000,000 watts.
Megawatt hour (MWh) A measure of electricity consumption equivalent to the use of 1,000,000 watts of power over a period of one hour.
Merchant asset TransAlta uses the term merchant to describe assets that have contracts with terms less than five years. Given our low-to-moderate risk profile, TransAlta contracts a significant portion of its merchant capability through short- and medium-term contracts.
Net maximum capacity The maximum capacity or effective rating, modified for ambient limitations, that a generating unit or power plant can sustain over a specific period, less the capacity used to supply the demand of station service or auxiliary needs.
Offsets Created through projects that substitute a greenhouse gas-emitting process with a lower emitting process, offsets represent the avoidance of emissions in various industrial and agricultural processes. Generating electricity from renewable sources is an example of avoiding the emissions from power generation from fossil fuels. Offsets are denominated in tonnes. The term offsets trading refers to the practice of purchasing or selling the benefits of reduced emissions to “offset” the emissions being produced by a company.
Opacity The degree to which emissions reduce the transmission of light
Power purchase arrangement (PPA) A long-term arrangement established by regulation for the sale of electric energy from formerly regulated generating units to PPA buyers.
Precipitator A pollution control device that collects particles from an air stream.
Renewable Energy Certificates (RECs) Also referred to as Emission Reduction Certificates (ERCs), or green tags, RECs are certificates that can be traded and sold to represent the environmental benefit created by generating electricity from a renewable energy source. The owner of the REC can then rightfully claim to have purchased renewable energy. RECs are denominated in megawatt hours.
Renewable power Power generated from renewable terrestrial mechanisms including wind, geothermal, solar and biomass with regeneration.
Sub-bituminous A type of coal, low to mid quality, that is used primarily as fuel for power generation.
Supercritical technology The most advanced coal-combustion technology in Canada employing a supercritical boiler, high-efficiency multi-stage turbine, flue gas desulphurization unit (scrubber), bag house and low nitrogen oxide burners.
Target Zero TransAlta’s initiative designed to drive health, safety and environmental performance to zero lost-time, medical aid and environmental incidents.
Turbine A machine for generating rotary mechanical power from the energy of a stream of fluid (such as water, steam or hot gas). Turbines convert the kinetic energy of fluids to mechanical energy through the principles of impulse and reaction or a mixture of the two.
Turnaround Periodic planned shutdown of a generating unit for major maintenance and repairs. Duration is normally in weeks. The time is measured from unit shutdown to putting the unit back on line.
Unplanned outage The shutdown of a generating unit due to an unanticipated breakdown.
Uprate To increase the rated electrical capability of a power generating facility or unit.