Promoting Green Power in Canada - Centre for Human Settlements

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Promoting Green Power in Canada Pollution Probe2. What Really is a “Green” Power Source?2.1 Terms and AcronymsThree main terms are used to describe powersources different from conventional energysources that have sustained modern industrialeconomies: alternative power, renewablepower, and green (or clean) power. Theseterms are not equivalent. For example,although large hydro is a renewable powersource, it is often excluded from renewablesources in a green power marketing contextbecause it is seen as a mature technologythat does not need to be supported by greenpremiums. Renewable power sources maynot be the same as “green” power sourcessince they can have important negativeenvironmental impacts that would disqualifythem from being considered green.A variety of products are currently sold underthe “green power” label. The energy sourcesmentioned in the list of terms belowrepresent today’s commercially available andproven technologies, as well as emergingtechnologies, such as ocean energy.Conventional power sources — nuclear,coal, oil and gas-fired power stations, largehydro.Alternative power sources — othersources than conventional energy sources.Renewable power sources — wind, solar,hydro, geothermal, ocean energy, biomass.Ocean energy — tidal energy (water storedfrom high tide and flowing through aturbine at low tide) and wave energy (energygenerated from the movement of waves).Biomass — a wide variety of fuels havebeen included under this heading: fuelsextracted from specially grown oil seeds(energy crops); agricultural waste; biogasfrom controlled fermentation processes;landfill gas; waste-to-energy; wood waste;sewage sludge incineration; etc.Solar power — photovoltaic energy (directconversion of sunlight into electricity) andthermal solar (electricity generated from heatcreated by sunlight).Hydro power — large hydro (larger than 30MW), small hydro (1 MW to 30 MW), minihydro (
Promoting Green Power in Canada Pollution Probelevel if green power certificates are tradedamong countries.2.2 An LCA-Based Comparison ofPower SourcesWhereas conventional energy sources areknown for their polluting emissions (e.g.,coal, oil, gas) or their safety and wasteproblems (nuclear), alternative energysources can also have negativeenvironmental impacts. One method used tocompare the relative impacts is life-cycleanalysis (LCA), which looks at impacts fromthe manufacture, construction, use anddecommissioning of energy productionplants. Some environmental impacts can bequantified and compared, others can only beevaluated on a qualitative basis. Theinformation contained in this chapter willhelp the reader understand the “greenness”of alternative energy sources.Box 2.1 — Literature on ConnectedIssuesFor a description of the harmful effectsof smog-causing pollutants, see TheSmog Primer atwww.pollutionprobe.org/Publications/ Air.htm.For a description of the harmful effectsof mercury, see The Mercury Primer atwww.pollutionprobe.org/Publications/Mercury.htm.For a description of some renewableenergy sources and technologies, seeUNEP’s technology fact sheets atwww.uneptie.org/energy/act/re/fs/,and see The Renewable EnergyTechnologies Primer atwww.pollutionprobe.org/Publications/Energy.htm.2.2.1 Emissions of CO 2, SO 2and NO xEnergy-related emissions include carbondioxide (CO 2 ), nitrogen oxides (NO x ),sulphur dioxide (SO 2 ), particulates, volatileorganic compounds (VOCs), and mercury.Comparative data were only available for thefirst three types. Emissions are compoundedover the whole life cycle of a plant, includingconstruction and decommissioning.As renewable power sources are added to thegrid, they influence power generation fromexisting, often fossil fuel-based, sources. Thechanges in operation due to the addition ofsources with variable outputs, such as windor solar, lead to additional emissions thatmay not otherwise occur. These are calledback-up emissions. The inclusion of back-upemissions increases the emissions ascribed tothe renewable sources. If the use ofrenewable power leads to the replacement offossil fuel-based energy generation. the backupemissions will eventually be reduced asmore low-emission sources get on the grid.Back-up emissions have been left out of thefollowing discussion of the environmentalimpacts of power sources.Figure 2.1 compares life-cycle air emissionsfrom different energy sources. Air emissionsfrom alternative energy sources are generallylower than those from conventional sources.Only nuclear technology has air emissions aslow as renewable power sources. Natural gascontains little or no sulphur and thereforecauses essentially no SO 2emissions. Socalled“clean coal” technology is now beingproposed and can reduce emissions to levelscloser to, but still higher than, those ofnatural gas and renewable power sourcesthrough technologies such as fuel cleaningand gasification (clean coal technologiesinclude, for example, Fluidized Bed,Integrated Gasification Combined CycleTechnology and Low-Emission BoilerSystems).3
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Promoting Green Power in Canada - Centre for Human Settlements

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