What Major Factors Reduced U.S. Power Sector Carbon Emissions 2007-2017?

Newswire—Total U.S. carbon emissions from fossil fuels consumption peaked in 2007.  The Electric Power Sector has been the largest ‘direct' contributor to Total U.S. carbon emissions since 1977.  Total 2007-17 U.S. carbon emissions declined by 15%, primarily due to reduced Power Section's emissions.  What have been the major market, government policy and technology based factors that have enabled reduced Power Sector's carbon emissions 2007-17?
The Energy Collective, February 21, 2018, by John Miller 

Brief U.S. Carbon Emissions History – During 1990-2007 Total U.S. carbon emissions increased by 19%.  This was primarily due to growth in U.S. Electric Power and Transportation Sectors' increased fossil fuels consumptions.  Since 2007, the Power Sector's carbon emissions have declined by 28%.  Refer to Figure 1.

Data Sources: EIA MER tables 12.1-12.6. Note: carbon emissions are from ‘direct consumption' of primary fuels.  The Industrial and all other End-use Sectors exclude secondary emissions from the Power Sector electricity purchases-consumption.

Due to a number of factors the consumption of fossil fuels has changed in all End-use Sectors.  Some of the largest overall influences begin with increased U.S. Population and overall Economy growth.  During 1990-2017 the U.S. Population grew from about 250 million up to 326 million (+30%), and the Economy or ‘gross domestic product' (GDP) grew from almost $9,000 Billion up to $17,000 Billion (+89%; 2009 $ basis).   Even with this very large growth in Population and the Economy, the U.S. mitigated-limited Total carbon emissions growth to less than 2%, 1990-2017.

Since Total U.S. carbon emissions peaked in 2007, the Power Sector has clearly been the largest contributor to reduced emissions over the past 10 years.  Reduced Power Sector carbon emissions resulted from primary fossil fuels ‘mix' and ‘consumption' changes.  Refer to Figure 2.

Data Source: EIA MER table 12.6.  Note: ‘Other Sources' includes all other hydrocarbons (petroleum, heavier gases, etc.), and geothermal, wood and waste.

Coal has and continues to be the largest, but fortunately declining, source of Power Sector carbon emissions.  Similar to Coal displacing liquid Petroleum fuels 50 years ago, Coal is increasingly being displaced by cleaner-low carbon Natural Gas since 2007.  Refer to Figure 3.

Data Source: EIA MER table 7.2bNote: ‘Other Sources' (from Fig. 2) are not shown in this graph, since they are nearly equal to the Solar Power plot, but are included in the ‘Total Net Power'.

Figure 3 shows that the Power Sector's total net generation from primary energy supply sources have changed very significantly since 1990.  In 2007, the year that both the Power Sector's carbon emissions and net generation peaked, the increase in Natural Gas (directly) and renewable Wind & Solar power (indirectly) have increasingly reduced the need for and the net generation from Coal Power Plants.  During 2007-17, Coal Power electricity supplies dropped from 50% of the total Power Sector's net generation, down to 32%.  Individual power generation energy source changes 2007-17 are more clearly illustrated in Figure 4.

Data Source: EIA MER table 12.6.  Note: ‘Other FF' includes all other ‘fossil fuels'; petroleum, coke and other gases heavier than ‘Nat. (Natural) Gas'.

Figure 4 shows that the largest reductions in required net power generation occurred in ‘Coal' and ‘Other FF' (fossil fuels) Power Plants, and, ‘Total' reduced net generation from reduced overall End-use Sectors' retail sales/consumptions.  Most of these higher carbon power net generation reductions were replaced by lower carbon Natural Gas and zero carbon Wind, Solar, and Hydropower.  Fortunately, Nuclear Power has been sustained at almost constant net generation levels 2007-17.

Major Factors That Reduced Power Sector's Carbon Emissions and Net Generation – Since 2007 a number of market, government policy and technology factors have enabled and facilitated the reduction in Power Sector carbon emissions.  Refer to Figure 5.

Data Source: EIA MER tables 7.2b and 12.6.  Note: NG(Natural gas)-to-Wind &Solar Displacement is another form of ‘energy source switching'.  ‘Geo+non-FF' = Geothermal + Wood &Waste.

The following list covers the primary factors and influences to Power Sector carbon emission reductions 2007-17:

  1. ‘Coal-to-Natural Gas Fuels Switching' (47% of total carbon emission reduction) – a number of factors have influenced and resulted in displacing Coal Power Plant's net generation with Natural Gas Power Plant's electric supplies. The largest factor has been due to the recent substantially increased U.S. domestic Natural Gas production, resulting major market price decreases.  Natural Gas prices peaked in 2008, then dropped by over 60% 2012-17.  This market based factor in addition to aging and less efficient Coal Power Plants, and, growingly expensive EPA regulations (reduced stack Hg, PM, etc. emissions and the Clean Power Plan), have significantly reduced the economics of operating and sustaining older Coal Power Plants.  The development and growth of economically attractive cleaner/higher efficiency ‘combined cycle' Natural Gas turbine-generator technologies has also further contributed to increased Coal-to-Natural Gas fuels switching.
  2. Reduced Power Sector Net Generation Demand (20% of total) – this second largest factor to reduced Power Sector carbon emissions is fairly complex and will be covered in more detail in the following Figure 6/backup data.
  3. Natural Gas-to-Wind Power Displacement (17%) – variable Wind Power normally only displaces intermediate/peaking Natural Gas Power generation, which can be readily rapped up and down as Wind Power net generation supplies vary with weather conditions; in order to properly/reliably balance Power Grid's supply-demand. Most Wind Power Farms have been economically supported by fairly generous Federal and State ‘production tax credits' (PTC) and ‘investment tax credits' (ITC).  Most of these credits or power generation subsides have lasted for up to 10 years; from original construction-startup time frames.  These subsidies have made Wind Power generation more economically attractive compared to older/lower efficiency Natural Gas Power Plants.  Another factor has been the development of new-larger Wind turbine generator technologies.  These upgrades have significantly increased average Wind Power generation capacity factors (<30% up to 40%+), and, its directional ability to ultimately displace some future baseload power generation.
  4. Increased Hydropower Generation (7%) – increased Hydropower net generation 2007-17 directly displaced ‘baseload' Coal Power Plant's generation; another form of fuels/energy switching. Besides Hydropower's zero carbon and reduced pollution benefits, the recent-current operating economics appear superior to older Coal Power Plants.
  5. Reduced Petroleum and Other Fossil Fuels (5%) – these generally older Power Plants can be displaced/replaced by most other lower/zero carbon Power Plants. Only a fraction of these ‘Other fossil fueled' plants/operations can generally be displaced by variable Wind & Solar, since these fossil fuels are often used as ‘backup fuels' to both baseload Coal and Natural Gas fired steam boiler-generators.  Once again, the most likely motive to displacing these Other fossil fuels is their higher fuel prices and possibly some more costly EPA reduced stack emissions regulations (NOx, SOx, etc.).
  6. Natural Gas-to-Solar Displacement (4%) – variable Solar Power normally displaces intermediate/peaking Natural Gas Power, which can be readily rapped up and down as Solar Power net generation supplies vary with weather conditions and time-of-day. The economic advantage is also generally based on PTC/ITC subsides, and other local State economic incentives.
  7. Added Geothermal and NonFossil Fuels (1%) – these lower carbon power sources can displace a combination of baseload Coal Power and Intermediate Natural Gas and/or Other fossil fuels power generation. Some generation PTC subsidies have been available to make Geothermal and Wood/Waste power generation economically attractive over the years.

Reduction in the Power Sector's Retail Sales/Demand – The second largest factor that has reduced the Power Sector's 2007-17 carbon emissions has been ‘reduced demand' for power supplies.  Reduced demand has been largely due to changes in each U.S. End-use Sectors' retail power consumption requirements and recent Power Grid improvements.  Refer to Figure 6

Data Sources: EIA MER tables 7.1, 7.6 and 12.1-12.6.  Note: ‘T&D Losses' = Transmission and Distribution Power Grids' system losses between the Power Plant's supply and final End-use metered consumption.  Reduced demand data also includes distributed Solar PV generation consumed directly within most End-use Sectors.

The following covers the primary factors that have led to reduced Power Sector electricity demands:

  1. Industrial Sector (47% of total retail demand reduction) – despite the increases of this Sector's GDP over the years, electric power demand has declined by 8% 2007-17. This has been due to a combination of increased efficiency of manufacturing & processing facilities-equipment, lower energy intensive production & manufactured products (such as reduced raw & finished metals and major durable goods; major vehicles & appliances), and, shifting to substantially lower energy intensive-modern computer technologies.  Increased installation of distributed Solar power supplies has also directionally reduced the need for retail power purchases.  However, the largest impacting factor since 1990 has been increased U.S. ‘trade deficits'.   This factor has very significantly constrained required U.S. Industrial Sector power consumption and carbon emissions, which unfortunately has indirectly led to substantial increased U.S. ‘carbon leakage' to Developing Countries such as China.
  2. Residential Sector (22% of total) – despite the increase in U.S. Population, the combination of increased homes' insulation, more efficient appliances and smart-home utility control technologies, have been major contributors to reduced per capita and total power demand. Another significant factor has been increased distributed Solar PV installations, due to the ‘net-market' subsidies, and also, related Commercial leased-owned solar panel installations.
  3. Total (U.S. Power) Grids T&D Losses (up to 16%) – EIA data indicates that during 2007-17 overall End-use Sectors' and regional Power Grids have apparently made significant improvements that have very significantly reduced Transmission & Distribution systems' power losses; i.e. increased systems' efficiency and reduced retail power demand.
  4. Net Power Import Supplies (14%) – during 2007-17 U.S. net power imports increased significantly; primarily from Canada.  Since most of these Canadian net imports come from Hydropower, carbon leakage is relatively insignificant in this case.
  5. Transportation Sector (<1%) – EIA data indicates a very small decrease in power demand 2007-17; despite the growing increase of ‘electric vehicles' (EV's) in recent years. This change is relative insignificant, and is generally unrelated to charging EV's batteries within the Transportation Sector.  EV battery recharging is normally accounted for in the Residential & Commercial Sectors' power consumption-demands.
  6. Commercial Sector (1%) – Commercial facilities power demands apparently grew at a slightly greater rate than increased building & utility systems efficiency upgrades. This Sector's increased power demand has also been offset directionally by installed distributed Solar PV power generation, 2007-17.

Future Power Sector Carbon Emissions – The U.S. has made fairly decent progress in reducing its Power Sector's carbon emissions over the past 10 years.  Future projections are highly uncertain, beginning with recent policy changes made by the Trump Administration: 1) withdrawing from the Paris Climate Agreement (in 2020),  2) repealing the Clean Power Plan, and, 3) plan to ‘Make America Great Again' by growing the economy.

Growing the U.S. Economy generally includes expanding the Industrial Sector (manufacturing of durable goods) and reducing past-current U.S. trade deficits.  While the recent Administrative action to imposed U.S. import tariffs on Solar PV panels can have mixed results on future expansion of U.S. Solar Power capacity-generation, the growth in the Industrial Sector will very likely reduce U.S. ‘carbon leakage' from reduced imports and increased domestic manufacturing of many durable goods.  What is often overlooked is the fact that U.S. Manufacturing is significantly more efficient and less carbon intensive than Developed Countries, which reduces overall carbon emissions (or leakage) on a Global basis.

Other uncertainties include clean power technologies developments.  This includes sustaining and possibly growing Advanced Nuclear Power generation, and Industrial-scale Power Storage.  Industrial scale Power Storage is needed to enable variable Solar and Wind Power to eventually and directly displace Coal Baseload Power generation in the future.  Even ‘carbon capture and sequestration' (CCS) and increased advanced biofuels technologies developments may also become more feasible and economically sustainable in the future.

Will the U.S. eventually comply with past Administration's pledges, such as the Paris Climate Agreement (reduce U.S. 2005-25 total carbon emissions by 26-28%)?  The answer of course depends on future Administrative and Congressional actions, and, development of truly ‘affordable' clean power technologies.  Needed government policy actions could include: sustainably supporting domestic cleaner energy production & supplies, possibly extending/increasing future renewable power PTC subsidies, not curtailing existing CAFE standards & increasingly supporting EV's development-growth, and properly evaluating-ensuring that all future mandated clean energy technologies' ‘full-lifecycle' carbon emissions are truly being reduced by at least 50% compared to current fossil fuels energy supplies; in order to truly avoid more hidden global carbon leakage, and little or no reduction in Global carbon emissions.  Other recent carbon leakage examples: Brazil ethanol and Argentina biodiesel imports.

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