Study Concludes Wind-Powered BEV and Hydrogen Fuel Cell Vehicles Best Options, Biofuels the Worst to Address Climate, Energy Security and Pollution
13 December 2008
|A combined weighted ranking of the 12 combinations of energy sources and vehicle type against 11 impact categories. Click to enlarge.|
A new study by Stanford University professor Mark Jacobson (earlier post) reviews and ranks major proposed energy-related solutions to global warming, air pollution, and energy security while considering impacts of the solutions on eleven different factors ranging from resource availability to mortality. To place electricity and liquid fuel options on an equal footing, Jacobson considered 12 combinations of energy sources and vehicle type: nine electric power sources (solar-PV, CSP, wind, geothermal, hydroelectric, wave, tidal, nuclear, and coal with CCS) and two liquid fuel options (corn-E85, cellulosic E85) in combination with three vehicle technologies (battery-electric, BEVs; hydrogen fuel cell, HFCVs; and flex-fuel E85 vehicles).
The overall rankings of the combinations (from best to worst) were: (1) wind-powered battery-electric vehicles (BEVs); (2) wind-powered hydrogen fuel cell vehicles; (3) concentrated-solar-powered-BEVs; (4) geothermal-powered-BEVs; (5) tidal-powered-BEVs; (6) solar-photovoltaic-powered-BEVs; (7) wave-powered-BEVs; (8) hydroelectric-powered-BEVs; (9-tie) nuclear-powered-BEVs; (9-tie) coal-with-carbon-capture-powered-BEVs; (11) corn-E85 vehicles; and (12) cellulosic-E85 vehicles. His findings are published online in an open access article in the journal Energy & Environmental Science.
The impact categories examined included:
- Resource abundance
- CO2e emissions
- Water consumption
- Effects on wildlife
- Thermal pollution
- Energy supply disruption
- Normal operating reliability
Upon ranking and weighting each combination with respect to each of 11 impact categories, four clear divisions of ranking, or tiers, emerge. Tier 1 (highest-ranked) includes wind-BEVs and wind-HFCVs. Tier 2 includes CSP-BEVs, geothermal-BEVs, PV-BEVs, tidal-BEVs, and wave-BEVs. Tier 3 includes hydro-BEVs, nuclear-BEVs, and CCS-BEVs. Tier 4 includes corn- and cellulosic-E85.
Wind-BEVs ranked first in seven out of 11 categories, including the two most important, mortality and climate damage reduction. Although HFCVs are much less efficient than BEVs, wind-HFCVs are still very clean and were ranked second among all combinations. Tier 2 options provide significant benefits and are recommended. Tier 3 options are less desirable. However, hydroelectricity, which was ranked ahead of coal-CCS and nuclear with respect to climate and health, is an excellent load balancer, thus recommended.
The Tier 4 combinations (cellulosic- and corn-E85) were ranked lowest overall and with respect to climate, air pollution, land use, wildlife damage, and chemical waste. Cellulosic-E85 ranked lower than corn-E85 overall, primarily due to its potentially larger land footprint based on new data and its higher upstream air pollution emissions than corn-E85. Whereas cellulosic-E85 may cause the greatest average human mortality, nuclear-BEVs cause the greatest upper-limit mortality risk due to the expansion of plutonium separation and uranium enrichment in nuclear energy facilities worldwide. Wind-BEVs and CSP-BEVs cause the least mortality.—Jacobson 2009
|Summary table of rankings. Click to enlarge.|
For his analysis, Jacobson estimated the comparative changes in CO2e emissions due to each of the 12 energy sources considered when they are used to power all (small and large) onroad vehicles in the US if such vehicles were converted to BEVs, HFCVs, or E85 vehicles.
For BEVs, Jacobson considered all nine electric power sources. For HFCVs, he assumed the production of hydrogen by electrolysis, with electricity derived from wind power; he did not analyze other methods of producing hydrogen for convenience.
However, estimates for another electric power source producing hydrogen for HFCVs can be estimated by multiplying a calculated parameter for the same power source producing electricity for BEVs by the ratio of the wind-HFCV to wind-BEV parameter (found in ESI). HFCVs are less efficient than BEVs, requiring a little less than three times the electricity for the same motive power, but HFCVs are still more efficient than pure internal combustion (ESI) and have the advantage that the fueling time is shorter than the charging time for electric vehicle (generally 1–30 h, depending on voltage, current, energy capacity of battery). A BEV-HFCV hybrid may be an ideal compromise but is not considered here.—Jacobson 2009
Wind-BEVs performed the best in 7 out of 11 categories, including mortality, climate-relevant emissions, footprint, water consumption, effects on wildlife, thermal pollution, and water chemical pollution. jacobson found that the footprint area of wind-BEVs is 5.5–6 orders of magnitude less than that for E85 regardless of ethanol’s source, 4 orders of magnitude less than those of CSP-BEVs or PV-BEVs, 3 orders of magnitude less than those of nuclear- or coal-BEVs, and 2–2.5 orders of magnitude less than those of geothermal, tidal, or wave BEVs.
Jacobson said that the intermittency of wind, solar, and wave power can be reduced in several ways:
- Interconnecting geographically-disperse intermittent sources through the transmission system;
- Combining different intermittent sources (wind, solar, hydro, geothermal, tidal, and wave) to smooth out loads, using hydro to provide peaking and load balancing;
- Using smart meters to provide electric power to electric vehicles at optimal times;
- Storing wind energy in hydrogen, batteries, pumped hydroelectric power, compressed air, or a thermal storage medium; and
- Forecasting weather to improve grid planning.
(In 2007, Jacobson and colleague Cristina Archer published a paper in the Journal of Applied Meteorology and Climatology on the interconnection of wind farms to provide a steady, dependable source of electricity.)
In summary, the use of wind, CSP, geothermal, tidal, solar, wave, and hydroelectric to provide electricity for BEVs and HFCVs result in the most benefit and least impact among the options considered. Coal-CCS and nuclear provide less benefit with greater negative impacts. The biofuel options provide no certain benefit and result in significant negative impacts. Because sufficient clean natural resources (e.g., wind, sunlight, hot water, ocean energy, gravitational energy) exists to power all energy for the world, the results here suggest that the diversion of attention to the less efficient or non-efficient options represents an opportunity cost that delays solutions to climate and air pollution health problems.
The relative ranking of each electricity-BEV option also applies to the electricity source when used to provide electricity for general purposes. The implementation of the recommended electricity options for providing vehicle and building electricity requires organization. Ideally, good locations of energy resources would be sited in advance and developed simultaneously with an interconnected transmission system. This requires cooperation at multiple levels of government.—Jacobson 2009
Mark Z. Jacobson (2009) Review of solutions to global warming, air pollution, and energy security. Energy Environ. Sci., doi: 10.1039/b809990c
Cristina L. Archer and Mark Z. Jacobson (2007) Supplying Baseload Power and Reducing Transmission Requirements by Interconnecting Wind Farms. Journal of Applied Meteorology and Climatology doi: 10.1175/2007JAMC1538.1
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