全球变化知识资源中心(globalchange): Potential contribution of wind energy to climate change mitigation

It is still possible to limit greenhouse gas emissions to avoid the 2 °C warming threshold for dangerous climate change¹. Here we explore the potential role of expanded wind energy deployment in climate change mitigation efforts. At present, most turbines are located in extra-tropical Asia, Europe and North America^{2, 3}, where climate projections indicate continuity of the abundant wind resource during this century^{4, 5}. Scenarios from international agencies indicate that this virtually carbon-free source could supply 10–31% of electricity worldwide by 2050 (refs 2, 6). Using these projections within Intergovernmental Panel on Climate Change Representative Concentration Pathway (RCP) climate forcing scenarios⁷, we show that dependent on the precise RCP followed, pursuing a moderate wind energy deployment plan by 2050 delays crossing the 2 °C warming threshold by 1–6 years. Using more aggressive wind turbine deployment strategies delays 2 °C warming by 3–10 years, or in the case of RCP4.5 avoids passing this threshold altogether. To maximize these climate benefits, deployment of non-fossil electricity generation must be coupled with reduced energy use.

Kinetic energy in the atmospheric boundary layer exceeds both present world electricity and energy demand^{6, 8}. Estimates of the present technical potential for wind energy span an order of magnitude owing to the range of assumptions used (17–320 TW; ref. 6), and the global extractable resource may be >428 TW (ref. 9), which greatly exceeds present total primary energy supply (TPES) of 18 TW (ref. 9). Thus, there is opportunity for substantial expansion of wind-generated electricity supply from today’s level (~0.2% of TPES (ref. 6)). Indeed ‘on a global basis, at least—technical potential is unlikely to be a limiting factor to wind energy deployment’⁶. Further, the large increase in both raw materials and rare metals required for large-scale expansion of wind is manageable¹⁰, and ‘no insurmountable long-term constraints to materials supply, labour availability, installation infrastructure or manufacturing capacity appear likely if policy frameworks for wind energy are sufficiently economically attractive and predictable’⁶. For example, rare-earth oxides used in the 20% of wind turbines with permanent magnet generators have known reserves of ~1,000 years supply at present consumption levels².

About three-quarters of global wind power capacity (282 GW at the end of 2012) is installed between 30° and 60° N in Europe, North America and China^{2, 3}. Although site-specific near-surface wind speeds (and wind resources) are determined by multiple scales of motion, wind regimes in these high-resource locations are largely dictated by the track, frequency and intensity of mid-latitude cyclones¹¹. Whereas smaller-scale thermodynamic systems such as storms cells and thermotopographic flows are not well described by Earth system and regional climate models, larger cyclones and hemispheric-scale teleconnections associated with intra- and inter-annual variability of wind speeds are comparatively well understood and modelled^{11, 12} (Supplementary Fig. 1). The ‘storm tracks’ that mid-latitude cyclones follow are, to a first approximation, determined by Equator-to-pole temperature gradients that have been decreasing since 1870 (in a manner consistent with global warming), and there is evidence of a resulting slight poleward shift in cyclone tracks¹¹. However, the signal-to-noise ratio is small, and climate change projections for the main regions of wind energy penetration developed using climate model ensembles, empirical and hybrid downscaling, indicate a stable resource to mid-century and probably beyond^{4, 5} and thus over the projected lifetime of wind power plants (20–30 years).

On the basis of this body of research, we quantify whether using this low-carbon-dioxide (CO₂)-emitting electricity generation source can impact the magnitude of climate change by lowering climate forcing. To facilitate interpretation of our results, we present them within the context of the Intergovernmental Panel on Climate Change (IPCC) RCPs and in terms of a goal of avoiding/delaying the 2 °C warming limit often considered the lower threshold for dangerous climate change¹.

Electricity generation from any source affects the local and/or global environment. For example, coal-fired electricity generation is associated with externalities beyond release of CO₂, including an average of 24.5 deaths, 225 serious illnesses and 13,288 minor illness per terawatt hour of electricity generated¹³. Large wind farms, like major cities and forests, extract momentum from the air and add turbulence, thus altering the meteorology downwind. However, detailed in situ and remote-sensing measurements at operating wind farms show limited impacts on, for example, near-surface temperature beyond a few kilometres¹⁴. Modelling of wind deployment of 5 to >20 times TPES, and thus in excess of the wind energy scenarios considered here, resulted in only moderate meteorological impacts of <1% and 0.1 K change in zonal mean precipitation and surface temperature⁹. Modelling of 2020 wind energy scenarios for Europe also resolved very small downstream impacts that were statistically significant only in winter (to ±0.3 °C change in 2-m temperature and to 5% increase in precipitation)¹⁵. Thus, externalities from large-scale wind energy deployment seem modest.

TPES more than doubled between 1973 and 2011 (ref. 16). In 2011, TPES was ≥540 EJ, of which renewables (excluding biomass/biofuels) contributed ~3.3% (ref. 16). Electricity production increased ~3.4% per year from 1973 to 2011 when it reached 22,000 TWh (ref. 16; 68% from fossil fuels), and annually consumes ~25% of global TPES (ref. 17). All plausible future scenarios indicate TPES and electricity generation increasing to 2035 (refs 7, 16). The International Energy Agency (IEA) projects that annual electricity demand may exceed 40,000 TWh by 2035 (2.3% increase per year) and even the IEA 450 scenario indicates >30,000 TWh of generation by then¹⁸ (Table 1).

Table 1: Scenarios of potential electricity generation from wind energy to 2050 shown in terms of terawatt hours and percentage of total electricity generation.

Full table

Capacity factors.

To convert from installed wind capacity (in gigawatts) to electricity generation (in terawatt hours), a capacity factor (the ratio of actual electrical power production to potential power production if operating at full nameplate capacity indefinitely) of 30% is assumed for wind energy. This is consistent with wind power plants operating at present². Capacity factors for wind turbines range from 20–50% for onshore, 35–45% for offshore and exceed 30% for wind turbines deployed in the US (refs 2, 6). Capacity factors are increasing owing to, for example, higher hub-heights, larger rotor diameters, expansion into higher-resources areas and better rotor design for lower wind speeds⁶.

Wind energy scenarios.

Although continued growth in wind energy installed capacity at present rates of 24% per year is unlikely to be sustained in the long-term, if it were continued wind energy could supply present electricity demand by 2040 (Fig. 1). Projections of technically feasible wind energy deployment for 2030 and beyond are shown in Table 1 and can be grouped into: Current Policies including IEA Current Policies and IEA 6DS, which project wind-generated electricity supply of ~2,250 TWh by 2035; New Policies including IEA 4DS and GWEC New Policies, which project wind-generated electricity supply of ~2,400–2,800 TWh by 2035; Intermediate Scenarios including IPCC scenarios Cat I + II and III + IV and IEA 2DS, which project wind-generated electricity supply of ~3,100–3,700 TWh by 2035; Moderate Scenarios including GWEC Moderate and IEA HiRen and 450 Scenario, which project wind-generated electricity supply of ~4,200–4,400 TWh by 2035; and Advanced Scenarios including the GWEC Advanced scenario, which projects wind-generated electricity supply of ~6,700 TWh by 2035.

The Moderate scenarios equate to supply of 14% of total annual electricity from wind by 2035. The GWEC Advanced scenario projects 22% of electricity from wind. Thus, both scenarios entail significant expansion of wind energy electrical power production (of 8–10 and 12–15 times present generation, respectively). The former is equivalent to: ~9% annual expansion of deployed capacity for a fixed capacity factor 30%, or if coupled with a gradual increase in capacity factor from 30 to 35%, ~6% annual increase in installed capacity. The energy scenarios shown in Table 1 are modelled to 2050. In this analysis, we extend these scenarios to 2100 by assuming that installation of wind capacity continues at the rate during the 2040s. In the Current Policies scenario, no further expansion of wind energy installed capacity occurs after 2030.

RCPs, description and assumptions.

The IPCC RCPs are described in detail elsewhere^{7, 26, 27, 28, 29}. In brief, RCP2.6 projects negative C emissions (that is, greater uptake from the atmosphere, than releases to the atmosphere) at the end of the century, leading to maximum emissions around 2030 (Fig. 2). This scenario assumes increases in energy efficiency, replacement of fossil fuels, addition of carbon capture and storage, and increase in bioenergy²⁹. RCP4.5 stabilizes radiative forcing at 4.5 W m⁻² (associated with CO₂ concentrations ~650 ppm), peak CO₂ emissions in 2035, and projects declines in overall energy use combined with increases in the contribution from nuclear, bioenergy and renewables. In RCP6.0 policy intervention is modelled as a carbon tax to limit radiative forcing to 6.0 W m⁻². TPES increases to 838 EJ per year in 2100, but growth slows after 2060 leading to peak CO₂ emissions in 2060. In this scenario, penetration of renewable energy sources increases over the century (2000–2100) from 12.9% to 15.7% (ref. 26; Supplementary Table 1). RCP8.5 is intended to represent the baseline scenario and hence applies slow improvements in energy efficiency with a tripling of TPES (met for the most part by increases in use of fossil fuels, particularly coal), which results in continuously increasing CO₂ emissions to 2100 (ref. 27). Global CO₂ emission trends observed at present are consistent with those in RCP8.5 (ref. 25). The cumulative CO₂ emissions from the four RCPs extend over the range of emission scenarios used in previous assessments (SRES A2, SRES B1 and IS92A; Fig. 2). TPES and renewable fraction in 2050 are estimated from each RCP based on the scenario descriptions^{26, 27, 28, 29}. In 2011 hydropower generated about 3,500 TWh of electricity worldwide and other renewables generated about 1,000 TWh (ref. 16). For each RCP, we assume 10% of TPES from renewables derives from wind²⁷ (Fig. 2 and Supplementary Table 1).


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Capacity factors.

Wind energy scenarios.

RCPs, description and assumptions.

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