ML12090A862
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| Site: | Indian Point  |
| Issue date: | 03/30/2012 |
| From: | Hydro-Quebec |
| To: | Atomic Safety and Licensing Board Panel |
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ENT000510 Submitted: March 30, 2012 COMPARING Power Generation Options Greenhouse Gas Emissions Why is climate change an important environmental issue?
In 2001, the Intergovernmental Panel on Climate Change (IPCC) produced a report on the impacts of climate change. In the Summary for Policymakers (pp. 7 and 14),
the panel assesses the following impacts as likely or very likely:
- More intense precipitation events: increased "oods, landslide, avalanche, and mudslide damage.
- Increased summer drying over most mid-latitude continental interiors and associated risk of drought.
- Increase in tropical cyclone peak wind intensities, mean and peak precipitation intensities.
- Intensi"ed droughts and floods associated with El Nino events in many different regions.
- Sea-level rise and an increase in the intensity of tropical cyclones would displace tens of millions of people in low-lying coastal areas of temperate and tropical Asia.
In Canada, as in all northern countries, climate Many northern species will also be endan-change is expected to be extremely rapid gered by climate change, e.g, polar bear, under the business-as-usual scenario. This beluga, caribou. In a recent publication means that ecosystems would have to entitled Sensitivities to Climate Change in migrate about 1,000 km northward in just Canada, Natural Resources Canada concludes 50 years. But forests cannot move at this that: The climate change associated with a speed. Forest "res and major dieback will doubled atmospheric concentration of CO2 result, affecting the overall productivity of may virtually eliminate salmon habitat from forests. the Pacific Ocean.
Greenhouse Gas (GHG) Emissions from Power Generation Options What pollutants The main greenhouse gases (GHG) are carbon dioxide (CO2) and methane (CH 4).
Both are directly related to energy systems. Any combustion will produce CO2.
cause climate CH 4 is emitted during the extraction of coal and natural gas. Any leakage in the change? distribution of natural gas will also result in CH 4 emissions, because commercial natural gas is composed of about 95% CH 4. Other greenhouse gases (N2O, CFC, HFC, PFC) are rarely included in the assessment of energy options, because of the low volumes emitted.
The various GHGs do not have the same effect on the climate. To take their differences into account, the IPCC has produced indicators of global warming potential, relative to CO2. In most studies, each GHG is converted to an equivalent of CO2 and added to the inventory. For example, a gram of CH 4 has a global warming potential of 23, relative to a gram of CO2 (over a 100-year period).
The data in Figure 1 is expressed in CO2 equivalent, meaning that CH4 emissions are included with CO2 emissions.
Which Rigorous comparisons must be based on life-cycle assessment (see Figure 1 and Table 1) energy option is responsible for To compare energy options fairly, all emissions from an energy system should be included. Recent studies, called life-cycle assessments, include emissions climate change?
from fuel extraction, processing and transportation, as well as from power plant construction and electricity generation. Figure 1 and Table 1 present the results of life-cycle assessments (LCAs), with typical data for eastern North America.
For each fossil fuel, Figure 1 includes two results: one for the technology typically in operation, and another for a high-performance modern technology (commercially available). For renewable sources, such as hydro or wind power, it is impossible to select one modern technology, as performance depends mainly on site-speci"c conditions. For these options, Figure 1 includes two results:
one for a typical existing project, and one for a very good site that will be available in the near future.
extraction processing transportation construction generation 2
Figure 1 - Life-cycle assessment of greenhouse gas emissions (kt eq. CO 2 /TWh) 1200 Base- and peak- Base-load options Intermittent load options with limited flexibility options that need backup 1022 999 990 generation 1000 (from oil) 941 841 800 787 kt eq. CO 2/TWh 649 600 499 548 400 422 (from gas) 121 100 90 33 51 16 14 20 38 10 3 4 6 0 9 0
Greenhouse Gas (GHG) Emissions er ir l oi l ;
le km ll; els l; m er se ar n ot S ow rvo yc 000 ce il fu oa 82 k iv tio st e r cl co ry w ov ola Di vy l c -
from Power Generation Options p
o e c
- 4 e ss s 4 of e ta m abu st ol r ea st e dr res d Nu Fu m fo n- ta an io ne ed ou ered W n y H u in ic bi liver n pl d H ith fro i v r po m eli w ph m o e re er w dr ic co d e
g en i tu al d y pp Fo a s gas d ro B o c H Co l g hy a
t ur Na NOTES: For each option:
3 Typical results for North America. the higher emission rate is based on typical existing technology Options presented in decreasing order of and the lower emission rate is based on the best available commercial technology for fossil fuels or on level of service. very good sites for renewable energy.
Greenhouse Gas (GHG) Emissions from Power Generation Options Table 1 - Life-cycle assessment of greenhouse gas emissions (kt eq. CO2/TWh)
Typical results Technical for North America comments Generation options Best commercial Typical Source Notes on thermal generation (classi"ed by level technology (very good existing of data
- Assessment without cogeneration of service) sites for renewables) technology
- Scrubbing of SO2 would increase GHG emissions from coal and oil.
Hydropower 10 33 HQ Estimates include gross emissions with reservoir reservoir reservoir from boreal reservoirs, which
= 40 km2 /TWh = 160 km2 /TWh overestimates their real net emissions.
Diesel 649 787 NRCAN Plant eff.43% Plant eff.35% industry data Heavy oil 841 999 NRCAN Plant eff.38% Plant eff.32% industry data Heavy oil 1019 1177 Cdn Climate Extraction/processing:
from oil sands Plant eff.38% Plant eff.32% Change Oil sands 203 kt CO 2 /TWh Secretariat Conventional oil - 25 kt CO 2 /TWh Added emissions = 178 kt CO 2 /TWh Natural gas 422 499 US NREL Extraction/processing about 50 kt /TWh combined-cycle turbines; Plant eff.58% Plant eff.49% + ef"ciency Transportation 4000 km = about 65 kt /TWh gas delivery 4000 km change Fuel cell; 548 990 US NREL Gas delivered over 4000 km hydrogen from H from gas; H from oil; reforming +
fossil fuel Cell eff.55% Cell eff.55% ef"ciency Bituminous coal; 941 1022 US NREL
- Surface mining; average user by river coal delivered Plant eff.35% Plant eff.32%
- For farthest user: emissions + 6%
482 km Lignite 1340 Dones Peat 1300 Kivisto Hydro run-of-river 3 4 HQ,Vattenfall, Dones Nuclear 6 16 Vattenfall, Dones Short rotation 51 90 Matthews, UK Coppice transportation distances coppice plantation Plant eff.30% Plant eff.30% + distance = 20 km (for 51) and 100 km (for 90) changes Forestry waste 0 14 Vattenfall Zero rate assumes that, combustion + correction for if not used, some waste would CH4 from wastes decay and create CH4 emissions.
Wind power 9 20 White 2 sites in Wisconsin, average use factor of 24%
Solar photovoltaic 38 121 Vattenfall, Dones Emissions from fabrication process 4
Greenhouse Gas (GHG) Emissions from Power Generation Options Rigorous comparisons must consider:
- the level of In Table 1, options are presented in decreasing order of level of service. This issue is important, because storing electricity in large quantities is very expensive and reliability and a reliable electricity supply must be achieved by generating electricity at the flexibility same time as it is consumed. If the balance between production and consumption is not maintained, frequency fluctuations will result, with major impacts on electrical equipment such as computers or appliances. Many ancillary services are required to provide reliable electricity:
- Presence during the maximum peak load
- Capacity to meet hourly and daily variations in load
- Frequency and voltage control, to keep transmission voltages within the required ranges
- Regulation, to maintain minute-to-minute generation/load balance Generation options are not all equally capable of providing such services.
Reliable electricity networks cannot depend only on must-run generation such as nuclear energy or on intermittent energy such as wind power, which requires a backup option to compensate for "uctuations. In comparison, hydropower with reservoir or diesel plants can provide all the services required for reliable electricity.
The assessment of hydropower is exceptional, because a reservoir can have
- the many many purposes, such as modulating power generation, irrigation, "ood control purposes of and water supply. If irrigation uses a lot of water, this may reduce the overall hydro projects electricity generation, thereby affecting the performance of a project (per kWh).
To make a fair comparison among power generation systems, the assessment of hydropower should include only projects designed strictly to generate electricity, or else the parameters should be corrected to attribute impacts to other purposes.
generation modulation irrigation 5
Greenhouse Gas (GHG) Emissions from Power Generation Options Main findings concerning GHG emissions
- The options with the lowest emissions are run-of-river hydropower, wind power and nuclear.
We should remember, however, that their production cannot be modulated to meet peak demand; often, fossil fuels will be needed to support these options.
- Hydropower with reservoir has a slightly higher emission rate. Overall, it should be considered as the option with the best performance, because of its reliability and other potential services such as "ood control, irrigation, and water supply. (There is still uncertainty, however, concerning GHG emissions from tropical reservoirs, an issue discussed in detail in another fact sheet.)
- Coal (modern or old plant) clearly has the highest emission factor, with twice the emissions of natural gas combined-cycle turbines.
- Heavy oil also has a very high emission rate. If the oil is extracted from oil sands, the emission factor is as high as for coal.
- Among fossil fuels, natural gas combined-cycle turbines have the best performance. The reported emission rates include emissions associated with delivering the gas over 4,000 km (typical for northeastern consumption). Emissions could be about 12% less for plants located close to gas wells. The emission rate could be further reduced with cogeneration. This is discussed in the next pages.
- Biomass can have an excellent performance, notably the use of forestry wastes within industries. The performance of biomass plantations is dependent on the energy expended in exploitation activities. The reported emission rates for short-rotation coppices depend on the average distance between the power plant and the source of biomass (20 and 100 km).
Expectations created by new technologies
- Fuel cells and hydrogen production Some have proposed a truly clean and reliable system, with the following steps:
Fuel cells consume hydrogen and emit no direct GHG emissions. They have raised high expecta- 1. Wind power providing electricity to a water tions concerning GHG reductions, but life-cycle electrolysis plant, producing hydrogen.
assessments show that these expectations are 2. Compression and storage of hydrogen.
unfounded. Currently, the only low-cost option to produce hydrogen is natural gas reforming, 3. Fuel cells would consume the hydrogen when electricity is needed.
with a life-cycle emission rate higher than burning gas in a combined-cycle turbine. If fuel cells In theory, this system is interesting because it are used in regions without gas distribution, offsets the intermittent character of wind power.
the reforming of oil leads to emissions similar In reality, it is very inefficient: electrolysis has an to those of coal-"red generation. ef"ciency of 70%, hydrogen storage needs energy for compression, and fuel cells are 50% ef"cient.
This means that, starting with wind power at 6¢/kWh, the final cost of electricity ends up as more than 20¢/kWh. This system will not be competitive for many decades.
6
Greenhouse Gas (GHG) Emissions from Power Generation Options
- CO2 scrubbing and sequestration In theory, a cogeneration plant with full heat utilization can achieve an overall ef"ciency of Another technology that has raised expectations 90%. What is the meaning of this maximum is CO2 scrubbing and sequestration. The CO2 must ef"ciency in terms of reducing GHG emissions?
"rst be captured from flue gas and then pumped In a scenario involving only natural gas (no fuel to an empty oil or gas well, which must be air-substitution), if the cogeneration plant replaces tight. This will be a huge task, as demonstrated a combined-cycle gas turbine with 54% electrical by a comparison with SO2 scrubbing. Even if the efficiency and a heat boiler at 90% efficiency, sulphur content in coal is only 1% or 2%, SO2 the GHG reduction will be about 25% (Eurelectric, scrubbing generates huge amounts of waste.
- p. 53).
Very few plants are equipped with scrubbers, because of the high cost and waste management In North America, cogeneration plants are rarely problems. In the case of CO2, the carbon respon- very ef"cient, because the emphasis is more sible for such emissions makes up more than on producing electricity than enhancing the 50% of the coal. CO2 scrubbing and sequestration use of waste heat. In order to achieve very high is technically possible, but will require huge ef"ciency, the size of the gas turbine must be amounts of energy, creating more pollution. adapted to the local use of heat, and plants would The ef"ciency of a thermal power plant with have to be much smaller than they generally are.
a CO2 removal system can be reduced by 30%.
If the storage well is located far away, the *
Conclusion:
Effective technologies energy required for pumping could equal half to reduce emissions the energy generated by the plant. Overall, Based on LCA, we can conclude that, in the the economic viability and environmental electricity sector, fuel cells and CO2 scrubbing bene"ts of CO2 scrubbing are still doubtful.
are unlikely to seriously reduce GHG emissions over the next 20 years. Moreover, the widespread
- Cogeneration and the implementation of these technologies is unneces-performance of thermal plants sary when we consider the numerous well-tested Cogeneration, or Combined Heat and Power technologies that can actually reduce emissions:
(CHP), plants have the potential to improve energy
- Hydropower, wind power and nuclear energy ef"ciency and reduce GHG emissions. But the word cogeneration can be misleading, because
- Natural gas combined-cycle turbines, replacing coal some low-ef"ciency cogeneration units can emit more GHGs than ef"cient separate equipment
- Quality cogeneration in thermal plants (one for industrial heat and another for electricity
- Energy ef"ciency measures generation). In many cases, plants have been con- Therefore, short-term emission reductions do sidered cogeneration plants, even though only not require new generation technologies, only a very small fraction of the waste heat is actually measures to favor the proper options.
used. In many cases, these plants have a worse environmental performance than ef"cient plants that produce only electricity. Because of this situa-tion, the European Commission is planning a directive on Quality-CHP.
7
Greenhouse Gas (GHG) Emissions from Power Generation Options Note concerning GHG emissions from reservoirs Recent research on aquatic ecosystems supports Thus, emissions measured at the surface of reservoirs the following statements: must be considered gross emissions, that systema-
- Many research programs have confirmed signifi- tically overestimate the level of GHG emissions for cant GHG emissions at the surface of all types of which reservoirs are responsible.Net emissions water bodies (reservoirs, natural lakes and rivers). must be defined by considering the emissions that would have occurred anyway, in the absence of a
- Most of the flooded biomass at the bottom of dam.
reservoirs has not decomposed after decades The following GHG emission rates were used in under water.
comparing options: 7 kt eq. CO2/TWh for best sites
- After the initial first few years (after impoundment), and 30 for the La Grande complex, with large reser-GHG emissions from reservoirs are similar to those voirs per unit of energy. These are gross emissions, of nearby natural lakes. These emissions, either measured on boreal reservoirs. They clearly represent natural or from old reservoirs, are mainly due to pessimistic estimates, because future de"nitions of organic carbon that is flushed into reservoirs net emissions will be much smaller.
from surrounding ecosystems.
References Andseta, S., M.J. Thompson, J.P. Jarrell, and D.R. Pendergast, 1998. CANDU reactors and greenhouse gas emissions. Canadian Nuclear Society.
[Cites emissions of 3 to 15 kt eq. CO2/TWh for CANDU reactors.]
Bates, J., 1995. Full fuel cycle atmospheric emissions and global warming impacts from UK electricity generation. ETSU-R-88, Harwell.
Dones, R., U. Gantner, and S. Hirschberg, 1999. Greenhouse gas total emissions from current and future electricity and heat supply systems. Proceedings of the 4th International Conference on GHG Control Technologies. Pergamon.
Dubreuil, A., Inventory for Energy Production in Canada, Natural Resources Canada (NRCAN), Int. Journal LCA, 2001, vol. 6 no. 5, p.281-284.
Eurelectric, 2002. European combined heat and power: A technical analysis of possible de"nition of the concept of quality CHP.
Intergovernmental Panel on Climate Change, 2001. Climate change 2001: Impacts, adaptation and vulnerability.
International Energy Agency, 1998. Benign energy? The environmental implications of renewables. OECD.
Kivisto, A., 1995. Energy payback period and carbon dioxide emissions in different power generation methods in Finland. IAEE International Conference.
Matthews, R.W., and N.D. Mortimer, 2000. Estimation of carbon dioxide and energy budgets of wood-"red electricity generation systems in Britain. IEA Bioenergy Task 25.
Spath, P.L., and M.K. Mann, 2000a. Life cycle assessment of a natural gas combined-cycle power generation system. National Renewable Energy Laboratory, US. NREL/TP-570-27715.
Spath, P.L., and M.K. Mann, 2000b. Life cycle assessment of hydrogen production via natural gas steam reforming. National Renewable Energy Laboratory, US. NREL/TP-570-27637.
Spath, P.L., M.K. Mann, and D.R. Kerr, 1999. Life cycle assessment of coal-"red power production. National Renewable Energy Laboratory, US.
NREL/TP-570-25119.
Uchiyama, Y., 1996. Life cycle analysis of electricity generation and supply systems: Net energy analysis and greenhouse gas emissions.
Central Research Institute of the Electric Power Industry, Japan. Paper presented at the symposium: Electricity, health and the environment:
Comparative assessment in support of decision making, International Atomic Energy Agency, Vienna, 16-19 October.
Vattenfall, 1999. Life cycle studies of electricity.
White, S.W., and G.L. Kulcinski, 1999. Net energy payback and CO2 emissions from wind-generated electricity in the Midwest. University of Wisconsin-Madison.
Author: Luc Gagnon gagnon.luc@hydro.qc.ca Hydro-Québec, Direction - Environnement www.hydroquebec.com/environment January 2003 Reproduction of this fact sheet is authorized.
2002G130-1A Cette publication est aussi disponible en français.