One measure of an electricity system's "greenness" is the metric known as carbon intensity, or the system average output of carbon dioxide per unit of electrical output. Low average carbon intensities are seen as "more green" and higher carbon intensities are seen as "less green". The coal phase-out in Ontario appears to be a clear driver behind Ontario's lessening carbon intensity when one looks at past and projected numbers. It will be interesting to see if Ontario's 2015 emissions can be as low as predicted.
Emissions from electricity systems can make a significant contribution to greenhouse gases. One measure of a system's "greenness" is the metric known as carbon intensity, or the system average output of carbon dioxide per unit of electrical output. A common unit of measure used is (metric) tonnes of CO2/MWh of electrical output.
Different generating types have their own carbon intensities. In Ontario, output from fossil plants comes with a value for coal plants of about 1.0 tonnes/MWh and for natural gas plants (with a heat rate of 7.5 MMBtu/MWh) of about 0.4 tonnes/MWh. Carbon-neutral sources such as nuclear, hydro, wind, and solar are generally viewed as having no carbon emissions and so their carbon intensities are zero. On a weighted basis then, electricity systems with extensive carbon-neutral resources have low carbon intensities while those relying more on fossil fuel have higher average carbon intensities.
Low average carbon intensities are therefore seen as "more green" and higher carbon intensities are seen as "less green".
In Ontario, the continuing retirement of coal, its replacement by natural gas and the addition of significant wind and solar generation mean the province's supply mix is in transition. With all the talk of "dirty coal", one would expect Ontario's carbon intensity to be high, meaning a lot less green than many other jurisdictions. We thought it might be interesting to compare Ontario to other jurisdictions.
Denmark and Germany
Denmark and Germany are seen as trailblazers in the implementation of green power. Without looking at the numbers, a natural conclusion to draw is that their electricity systems must be "more green" and hence have relatively low carbon intensities. An inspection of the numbers reveals this is not the case.
For Denmark, the most recent comprehensive data we found are for 2009 from the Danish Energy Agency's Annual Energy Statistics 2009. Total carbon emissions associated with electricity production were 18.2 million tonnes, while total electricity consumption was 31.6 TWh or 31.6 million MWh. The resulting carbon intensity was 0.58 tonnes/MWh.
For Germany, we used data for 2008 sourced from the International Energy Agency's CO2 Emissions from Fuel Combustion 2010. The data were less definitive since electricity and heat production numbers were lumped together. Total carbon emissions related to electricity and heat production were 337 million tonnes, from total electricity and heat production of 765 TWh or 765 million MWh. The resulting carbon intensity was 0.44 tonnes/MWh.
It should be noted that if electricity and heat production both use the same proportions of each fuel and given that heat production is inherently more efficient than power generation, the electricity-only carbon intensity is higher than the blended rate. Using Germany's 2008 consumption of 587 TWh and assuming the carbon intensity of heat production is half that of electricity production, the estimated electricity-only carbon intensity is 0.54 tonnes/MWh. Support for this comes from data for coal/peat-fueled generation: 291 TWh or 291 million MWh (46% of total production) with an emission intensity 0.827 tonnes/MWh yields 241 million tonnes of CO2 emissions from coal/peat alone, meaning the component contribution of just coal to the system-wide carbon intensity was 0.41 tonnes/MWh.
Even though many European coal-fired plants have a carbon intensity in the order of 0.8 tonnes/MWh, a cursory inspection of system-wide carbon intensities reveals that coal is the main driver behind these intensity numbers.
Canada and Other Provinces
As one would expect, Canadian provinces with extensive hydro and other renewable resources have low electricity carbon intensities, while those more dependent on fossil fuels have relatively high carbon intensities. Below is a sampling of these values.
|Other provinces, territories (weighted averages, weighted using 2009 production)||0.233||0.236||0.274||0.267|
Source: Canada - National Inventory Report 1990-2009, Greenhouse Gas Sources and Sinks in Canada, Part 3
The carbon intensity data for Canada are compared to the data for Denmark and Germany in the graph below.
As part of its consultation process for its updated Integrated Power System Plan, the Ontario Power Authority released past and projected emissions for Ontario. Using actual and projected provincial electricity consumption values, we calculated the carbon intensities shown in the table below.
(generation less net exports)
The coal phase-out, scheduled to be complete by the end of 2014, appears to be a clear driver behind Ontario's lessening carbon intensity. With CO2 emissions from natural gas of approximately 5 and 9 megatonnes in 2009 and 2010, respectively, it will be interesting to see if Ontario's 2015 emissions can be as low as the predicted 6 megatonnes.
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