The Sun Shines at Night: Solar Thermal Power with Storage

Summary.  The Solana Generating Station, a solar thermal electric generating facility in Arizona, has begun operation in October, 2013.  Solar thermal plants capture energy from the sun as heat, which is then used to form steam that drives a turbine generator.  Solana additionally features a thermal storage capability, based on heating a molten “salt”, to buffer extra heat energy for use when the sun does not shine.  The buffer provides up to six hours of thermal operation.  Solana’s electricity is contracted to Arizona Public Service, an electric utility company.

Solana is one of several commercial-scale solar energy facilities in the U. S. currently under construction or newly operating.  Its financing included major support from the U. S. Department of Energy Loan Guarantee Program.  This program supports many projects that commercialize new or unconventional technologies that provide energy for the U. S. economy.  Only 6% of its guarantee funds were granted to projects that have been “discontinued”.  This indicates its funds have a highly creditable success rate of 94%.  The program  fulfills an important governmental function, that of supporting projects that would have difficulty attracting private investment.

Introduction.  Incoming solar radiation generates electricity on a commercial scale using two different technologies.  First, solar photovoltaic power uses semiconductor light-sensitive panels directly to generate electric current.  These include the familiar solar panels used on rooftops for local generation.  Photovoltaic power is not considered here.

The second technology is solar thermal power generation.  The heat contained in sunlight is captured in a circulating fluid that heats water to steam.  The steam is then used in a conventional turbine to generate electricity.  An industrial scale solar thermal facility with the added feature of storing heat has just become operational in Arizona; it is described here.

The Solana Generating Station has begun operation near Phoenix, AZ.    This station a) focuses the sun’s energy using mirrors to heat an oil fluid flowing through the black horizontal pipes in the photo below.

Thousands of curved mirrors focus sunlight onto black pipes to heat the oil circulating in them.

Source: http://www.nytimes.com/2013/10/18/business/energy-environment/arizona-utility-tries-storing-solar-energy-for-use-in-the-dark.html

 

The heat stored in the oil is used either to b) heat water to make steam, which then drives turbines to generate electricity, or c) heat a high temperature molten “salt” (not table salt) which stores the transferred heat in a hot salt tank.  This is shown in the image below for daytime operation of the station.

 

At night the station d) transfers the heat stored in the molten salt back to the oil, which is then used to heat water to steam, driving the electric turbines.  This is shown in the image below.



 

Enough heat is stored in the molten salt during the day for about six hours of generating service after dark.

 

Other solar energy installations have tried storing excess energy in electric batteries.  But these are expensive, and so not suitable for large installations.

 

Industrial scale electricity generation.  The Solana Generating Station operates two generating turbines to provide a peak power (power is the rate of generating electrical energy) of 280 megawatts (MW; millions of watts; a watt is a unit of power).  The parabolic mirror-circulating oil facility includes thousands of individual mirrors covering about three square miles of land.  The station was built by the Spanish electricity company Abengoa using primarily materials sourced in the U. S. 

 

The electricity provided by Solana is being sold under a long term contract to Arizona Public Service (APS), providing electricity sufficient for 70,000 customers.  In addition to the Solana station, APS will have a total installed solar power capacity of 750 MW by the end of 2013, enough to serve 185,000 customers.

 

The Solana Generating Station represents a capital investment of about US$2 billion.  The U. S. Department of Energy (DOE) Loan Guarantee Program supported US$1.45 billion of this amount.  The utility customer base and long service lifetime of the station provide reasonable assurance that the loan guarantee will have been a successful venture.

 

During construction, the project provided 1,500 jobs in the local community.  Abengoa will require a small number of local permanent positions for maintenance and service of the station.

 

Discussion

 

The Solana Generating Station is but one of several industrial-scale renewable energy generating facilities being developed in the U. S.  A previous post summarizes some of the solar projects included in this category.  These too have reached fruition or are about to begin operation.

 

General descriptions of solar energy, be it photovoltaic or solar thermal, have been concerned with intermittency of service since the sun’s energy is available only during daylight hours.  The Solana Generating Station overcomes this criticism by use of its heat storage system based on molten salt heat reservoirs.  Although inevitable engineering losses arise during heat transfer into and out from the reservoirs, the station’s design permits using the sun’s energy, in the form of the heat stored in the reservoirs, to generate electricity during dark hours of the daily cycle, and/or if clouds excessively obscure sunlight.  Additionally the stored heat complements portions of the daily light cycle when other renewable energy sources, such as solar photovoltaic generators or wind turbines, are poorly effective.

 

The DOE Loan Guarantee Program (LGP) provided valuable financial support for this project.  The objectives of the program are summarized as “guarantee[ing] loans that support early commercial use of advanced technologies, if there is reasonable prospect of repayment by the borrower.” DOE loan guarantees are intended to promote commercial use of innovative technologies, but not to support energy research, development, and demonstration programs.

 

The LGP has provided loans totaling US$24.2 billion to 29 renewable energy and advanced technology commercial projects other than loans supporting nuclear energy.  They are summarized as having saved jobs or provided construction jobs totaling about 50,000 (although 33,000 of these are ascribed to jobs saved by loans to Ford Motor Co.).  Most of the loans are listed as “closed”.  Only a few, totaling US$1.5 billion, are listed as “discontinued”, including a loan to Solyndra Inc. which gained unfavorable political attention two years ago. 

 

In other words, only 6% of the funds guaranteed under the LGP have performed unsatisfactorily.  This is a highly positive outcome for a program intended to encourage novel or unproven technologies.  Thus the LGP has been remarkably successful in supporting the commercialization of new or unconventional technologies that promote expansion of the energy mix, and greater efficiency in transportation, for the U. S.  It is concluded that the LGP fulfills an important governmental function, that of supporting projects that would have difficulty attracting private investment.

 

  

© 2013 Henry Auer

IPCC Fifth Assessment Report, Part 1: The Physical Science Basis

Summary.  The Intergovernmental Panel on Climate Change issued Part 1 of its Fifth Assessment Report, “The Physical Science Basis”, on September 30, 2013.  The Report first summarizes past changes in the climate system.  It states that the recent warming of the earth/s climate is “unequivocal”.  Since the 1950s changes in many climate parameters including concentrations of greenhouse gases; temperature; loss of snow cover, glaciers and ice sheets; and rising sea levels are “unprecedented” considering the last decades to thousands of years.  There are many recognized contributions to these effects but by far greatest single factor is the increase in the atmospheric concentration of the greenhouse gas carbon dioxide.

A variety of climate models of lesser or greater complexity successfully reproduce the earth’s recent climate history on global and regional scales and over longer periods of time, showing that the models adequately account for the major processes involved in evolving climate change. 

These same models are then employed together with four scenarios of decreasing stringency concerning greenhouse gas emissions. Imposing rigorous emission constraints will limit further warming to a low, but still more elevated, level than the present by 2100; whereas continuing “business as usual”, an essentially unconstrained scenario, will lead to drastic increases in temperature by 2100 and induce severe changes in climate and the consequences thereof.

Furthermore, since carbon dioxide remains in the atmosphere for centuries or thousands of years, humanity’s actions today and in the near future will lead to irreversible and persistently higher global average temperatures for long time periods, affecting the lives and wellbeing of mankind’s progeny for generations.  For this reason this writer believes it is now time for the member states of the United Nations to coalesce around a meaningful agreement to reduce GHG emissions toward zero in order to stabilize the climate at the lowest level possible of its  new, higher greenhouse-mediated temperature.

 

Introduction.  The Intergovernmental Panel on Climate Change (IPCC) is established under the United Nations Framework Convention on Climate Change.  Four Assessment Reports (ARs) have been issued previously beginning in 1990; they are summarized here. Part 1 of the IPCC Fifth Assessment Report (5AR), “The Physical Science Basis”, was released on September 30, 2013.  This post is based on the Summary for Policymakers. 

(Part 2,  “Impacts, Adaptation and Vulnerability”, is due in late March 2014; and Part 3, “Mitigation of Climate Change”, is due in early April, 2014.)

As explained below in the Details section, IPCC ARs are prepared by hundreds of eminent climate scientists selected from among all member nations of the U. N.  First and second drafts are prepared in succession, each reviewed by others before moving to the next stage, and finally reviewed by selected government officials.  For this reason the 5AR meets every reasonable standard for scientific rigor, objectivity and validity.  It represents a worldwide consensus on the current status of climate science and projections of future effects as the world continues to warm, and merits serious consideration by all in view of the process outlined here and in expanded form below.

Part 1 of 5AR is presented in four sections: a summary of data characterizing past and present trends, the sources for the heat energy that is warming the planet, providing an understanding of past climate patterns using models, and projections of possible future warming depending on assumptions of humanity’s behavior.  These are summarized here and expanded in the Details section.

Observed Changes in the Climate System.  The Summary characterizes the warming of the earth’s climate to date as “unequivocal”.  Since the 1950’s many climate parameters have changed to an extent that is “unprecedented” with respect to historical patterns going back from decades to thousands of years.  Particular findings include increased concentrations of greenhouse gases (GHGs) in the atmosphere, warming of the atmosphere and the waters of the oceans, decreased amounts of snow (such as found in high mountain regions) and ice (such as land-based glaciers and sea ice), and a higher average sea level.

Properties of the Earth System That Contribute to Global Warming.  Contributions from many climatic features must be considered in arriving at a final value for the rate that the earth absorbs energy from the sun or releases it back into space.  The result shows that the overall rate of energy absorption per unit area of the earth’s surface is in fact a warming contribution.  This rate of absorption was 43% higher in 2011 than the value given for 2005 presented in the IPCC Fourth Assessment Report (4AR).  The largest contributing factor is the increase in atmospheric concentration of CO₂.

Providing an Understanding of Past Climate Patterns Using Models.  Humanity’s activities have been the dominant factor impacting global warming, both atmospheric and oceanic; changes in the global water cycle; reductions in snow and ice amounts; and the global mean sea level (95-100% likelihood).  Human activities affecting the earth’s climate are well understood, including adding to the atmospheric burden of GHGs. 

Historical data for the climate are well reproduced using climate models.  These have been improved greatly since 4AR.  More, and better quality, data have been acquired since then.  Computing power has greatly expanded.  Comprehensive models permit assessing effects with higher spatial and time resolution.  The Summary states with “very high confidence” that models now in use successfully provide temperature patterns at a continental scale of resolution and provide trends over many decades, capturing the dramatic warming since the middle of the 20^th century as well as transient cooling effects of large volcanic eruptions.

Projections of Possible Future Warming.  An ensemble of climate models, all of which successfully reproduce past climate behavior, was used to project future trends.  Four possible pathways (termed RCPs) are considered, characterized by increasing rates of heating the planet due to continued manmade emissions of GHGs, up to the year 2100.  Based on these models and pathways, the Summary concludes that if humanity continues emitting GHGs the earth will warm further, and the other climate responses discussed above will likewise continue worsening along paths already under way.  Limiting further climate change, beyond the level already established, depends on “substantial and sustained” reductions of GHG emissions.  The extent and severity of most further changes foreseen in 5AR differ little from those already characterized in 4AR; sea level rise, however, is projected to be more pronounced.

Conclusion

The Summary ends by stating

“Cumulative emissions of CO₂ largely determine global mean surface warming by the late 21^st century and beyond…. Most aspects of climate change will persist for many centuries even if emissions of CO₂ are stopped. This represents a substantial multi-century climate change commitment created by past, present and future emissions of CO₂.”

The global average temperature increases essentially linearly with the amount of CO₂ emitted into the atmosphere from 1870, through the historical period ending at 2010, and on into the projected emissions-temperature pathways through 2100.  The only difference in the projections for the four RCP cases is that for RCP 2.6 the trajectory ends in 2100 at a low level of total accumulated CO₂, with an overall increase in temperature under 2ºC (3.6ºF); the intermediate RCPs extend to higher total accumulated emissions and correspondingly higher temperatures projected for 2100; and ending with RCP 8.5 at the highest level of total accumulated CO₂ emitted by 2100 corresponding to a total temperature increase from 1870 of about 4.6ºC (8.3ºF).

Additional contributors to the rate of energy increase of the earth arise from sources other than CO₂ such as other GHGs, warming feedbacks that affect the rate of energy accumulation and sources such as melting permafrost which emits new methane.  Accounting for these additional factors leads to lowering the projected amounts of manmade CO₂ emissions permissible in order to remain below any given level of global warming.

The Summary further states “A large fraction of anthropogenic climate change resulting from CO₂ emissions is irreversible on a multi-century to millennial time scale” for the portion not absorbed into the ocean or taken up by photosynthetic plants.  There is no natural process operating within this time scale that removes CO₂ from the atmosphere.  It is projected that 15 to 40% of emitted CO₂ will remain in the atmosphere longer than 1,000 years.  Therefore the resulting warming of the earth will likewise persist at the higher temperatures projected in the models for many centuries, even after all new emissions of CO₂ will have come to an end. At least partly for this reason global sea levels will continue rising beyond 2100, due to further thermal expansion and continued melting of ice sheets and glaciers.  Melting continues as long as the air temperature at the ice sheet surface remains above the melting point.  By 2300 the sea level could rise by 1 m (3.3 ft) under the RCP 2.6 scenario, or by as much as 1 m to more than 3 m (10 ft) under the RCP 8.5 scenario.  Sustained warm temperatures are thought to lead to complete loss of the Greenland ice sheet over 1,000 years, producing a sea level rise of up to 7 m (23 ft).

 

Analysis

 

The IPCC, starting in 1990, has concluded that our planet is warming as the result of manmade emissions of GHGs including CO₂.  In its First AR and thereafter, it has urged the nations of the world to reduce emissions drastically in order to minimize anticipated increases in the long-term average global temperature. Recent ARs corroborated the earlier ones as more, and more sophisticated, data has been accumulated and analyzed, and more robust modeling has permitted more detailed projections of future climate trajectories to be made.   As a result statements of the likelihood of potential outcomes have become more certain.

The present 5AR continues this progression, benefiting from robust newly gathered data and analysis, and elaboration of climate models of increasing sophistication, regional and spatial resolution, and time development.  It continues the trend of the earlier reports, presenting data analysis and projections that have not changed significantly in substance, but that are now presented with higher degrees of certainty in view of the newly acquired information and the specificity of new modeling forecasts.

If meaningful abatement steps were not undertaken, the ARs have warned, serious consequences to human welfare would occur.  These include rising sea levels carrying the danger of unprecedented storm surges, and region-dependent increases in heat and drought in certain areas or heavier precipitation and river flooding in others.  All these eventualities impact negatively on the socioeconomic wellbeing of affected populations.

These warnings are actually coming to pass with increasing regularity and ferocity in recent years; global warming contributes significantly to such extreme events.

 

Global warming is “unequivocal”; it is under way at the present time.  Climatic changes are due to manmade emissions of GHGs including CO₂ released when fossil fuels are burned.  The harms arising from greenhouse effects, such as record high temperatures and heat waves, more and more intense storms including flooding, and sea level rise, cause widespread damage and human suffering.  Ultimately society pays for these emergencies through relief and adaptation measures.  Now is the time for the member states of the United Nations to coalesce around a meaningful agreement to reduce GHG emissions toward zero in order to stabilize the climate at its new, higher greenhouse-mediated temperature.

 

Details

 

Significance of IPCC Assessment Reports.  The 5AR, like its predecessors, is produced by a large, ecumenical group of hundreds of  experts in their fields, and subjected to review by other experts and by appropriate governmental bodies before it is approved and accepted for release.  Technical details are based only on peer-reviewed journal articles and reports produced by renowned nongovernmental organizations or government agencies.  The exhaustive review assures that the released report both represents the current state of scientific and technical expertise, on the one hand, and the points of view of governments of the IPCC, on the other. 

The steps involved in preparing the reports are summarized here:

1. Governments and organizations nominate authors, who are then selected by the organizers of the Working Groups (here called “Parts”)
2. The selected authors prepare a first draft of the Part;
3. The first draft is reviewed by others;
4. Authors prepare a second draft considering reviewers’ comments;
5. The second draft is reviewed by governments and experts
6. A final draft is prepared considering reviewers’ comments;
7. Governments review the final draft; and
8. The final draft is approved and accepted by the IPCC, and released.

As a result of this thorough drafting and review process, the ARs are rigorously objective.  The reader cannot seriously believe that the ARs offer prejudiced or directed findings or opinions. Indeed, the approval and acceptance process likely leads to consensus positions on unresolved or contentious issues while minimizing the importance granted outlying results or evaluations.

Preparation of the first draft of Part 1 of the 5AR involved 659 experts and considered 21,400 comments; the second draft involved 800 experts and 26 governments, and considered 31,422 comments.

The following sections expand on the summaries outlined above.

Observed Changes in the Climate System.  As dates of observation advance from 1880 to the present, more data sets covering much of or all the globe have become available.   In recent decades satellite measurements have become significant. 

Considering 10-year averages, the last three decades have been successively warmer at the Earth’s surface than before, and warmer than any earlier decade going back as far as 1850.  For the period 1880 to 2012 the earth has warmed by 0.85ºC (1.5ºF), with a 90% confidence interval of 0.65 to 1.06ºC.   For the period 1901 to 2012, for which adequate regional data exist (this excludes the Arctic and Antarctica, and regions in the Amazon, central Africa and central China), a global map of temperature trends shows almost all regions on the earth’s surface of experienced warming (only a region of the North Atlantic south of Greenland became cooler).

The troposphere, the lowest part of the atmosphere closest to the earth’s surface, has warmed since the 1950’s (stated with virtual certainty, i.e. 99-100% likelihood).

The Summary specifically points out that short-term patterns are highly variable (speaking of periods as long as 10 to 15 years).  Variations on such a time scale cannot be taken to represent a change in long-term (periods of up to 60 years) trends.  It calls this phenomenon “natural variability”.  Short-term trends depend critically on the years that an interested observer might choose for the beginning and end of the period.  For example, the Summary cites the low rate of increase in temperature over the period 1998 to 2012, which began with a strong cyclical oceanic El Niño phase (warming of the ocean and atmosphere), was only 0.05ºC (0.09ºF) per decade.  The longer-term heating rate, however, from 1951-2012 was 0.12 ºC (0.22ºF) per decade. 

Heat energy is stored in the waters of the oceans to a far greater extent than on the surface of the earth or in the atmosphere.  Warming of the ocean accounts for more than 90% of the increase in heat energy experienced by the earth between 1971 and 2010, stored mostly in the upper 700 m (2,296 ft).  The upper 75 m (246 ft) warmed by 0.11ºC (0.20ºF) per decade over this interval.

The Greenland and Antarctic ice sheets and glaciers worldwide have decreased significantly.  The rates of loss due to melting have increased considerably over the past 20-30 years.  Arctic sea ice refers to permanent ice and peripheral seasonal ice frozen out of the Arctic Ocean.  The area of Arctic sea ice has decreased by 3.5 to 4.1% per decade over the period 1979 to 2012, and the summer minimum decreased by 9.4 to 13.6% (90-100% probability).  Northern hemisphere snow cover has decreased since the mid 20^th century.  Areas of permafrost have experienced surface temperatures warmer by 2-3ºC (3.6-5.4ºF).

The rate of rise of sea level has increased since the mid 19^th century to a rate larger than has been found for the last 2,000 years.  This rate of increase itself has grown from the late 1800’s and early 1900’s to considerably stronger increases since the early 20^th century.  Sea level rise originates largely from contributions of a) the expansion of the volume occupied by ocean water as it warms, b) melting of glaciers and the polar ice sheets, and c) changes in storage of water by land areas.

Atmospheric concentrations of GHGs have increased to levels unseen in the geological record for at least the last 800,000 years.  These include carbon dioxide (CO₂), methane (natural gas) and nitrous oxide.  Their atmospheric concentrations have increased since 1750 because of human activity associated with the Industrial Revolution.  CO₂ has increased by 40% in this time, mostly from burning fossil fuels and cement production, and somewhat from emissions arising from changes in land use.  About 30% of atmospheric CO₂ is absorbed by the waters of the oceans; since CO₂ is an acid the increase from human activity has caused a surface zone of the oceans to become more acidic by 0.1 pH unit; this translates to an increase in the concentration of acid in the water by 26%. 

Properties of the Earth System That Contribute to Global Warming.  Processes affecting the energy balance of the earth are measured in terms of the rates of energy exchange per unit surface area. In order of decreasing rates  of heating the earth, the contributors are CO₂, methane, ozone, fluorine-containing hydrocarbons (which originate from manufacture and recycling of refrigerators and air conditioners), nitrous oxide, carbon monoxide, and other lesser contributors. 

The role of aerosols has become better understood since 4AR.  Black carbon aerosols (originating from incomplete burning of fuels) contribute to net energy absorption, while white or light colored aerosols (from volcanic eruptions and byproducts of emanations from green plants) are negative, acting to reflect incoming sunlight back into space.  Aerosols figure importantly in the secondary effects of cloud droplet formation, and are evaluated here as having a net effect of increasing reflection of incoming sunlight back into space.  (Aerosols from volcanic eruptions and changes in net intensity of sunlight impinging on the earth are evaluated as being very small.  Volcanic aerosols are very transitory; even large eruptions, while having a cooling effect, last only a few years.)

Overall, the sum of the effects considered here result in a large increased rate of energy absorption per unit area by earth, almost double the rate evaluated in 1980.  The rate for 1980 in turn was more than double the rate evaluated for 1950.  (See the graphic below.)

Increase in the net rate of absorption of energy per unit area of the earth (Radiative Forcing, in watts per square meter) due to humanity’s activities for the years 1950, 1980 and 2011, relative to the value for 1750.  The horizontal black lines extending left and right from the tips of the red bars are estimates of the error in each value.  Values for the mean increase, and the lower and upper extents of the error (inside square brackets) are shown to the right of each bar in red.  These results are the sums of the contributions, positive and negative, described in the paragraph preceding this graphic.

Source: IPCC 5AR Summary for Policymakers; http://www.climatechange2013.org/images/uploads/WGIAR5-SPM_Approved27Sep2013.pdf.

 

Providing an Understanding of Past Climate Patterns Using Models.  Models successfully reproduce observed temperature trends over the long term from 1951 to 2012 with “very high confidence”.  But more short term effects are not matched in models.  For example, the reduced warming rate between 1998 and 2012, compared to the long-term trend from 1951 to 2012, is thought to arise equally from lower overall heating of the earth system, arising from volcanic eruptions and a weakening portion of the 11-year solar cycle, and a cooling contribution from internal variability such as larger removal of heat from the surface by the waters of the oceans.

Modeling global trends in extreme weather and extreme climate events has improved, as has continental scale modeling of precipitation.  Cyclical global patterns such as monsoons and the El Niño-Southern Oscillation have improved.

Modeling of positive and negative climate feedbacks has improved.  Surface warming, its effect on atmospheric content of water vapor, and dynamics of cloud formation are better.  The net feedback from these effects is “extremely likely” (95-100%) to be positive, amplifying warming effects on climate.

Climate sensitivity measures the extent of warming for a given change in overall energy absorption by the earth.  It is frequently characterized by the extent of warming expected from a doubling in atmospheric concentration of CO₂.  A lower number means the earth warms only weakly with increases in GHGs, while a high number indicates stronger warming with increased GHGs.  In 5AR climate sensitivity is likely (66-100%) in the range 1.5 to 4.5ºC (2.7 to 8.1ºF).  The lower limit of 1.5ºC represents a decrease from the 2ºC lower limit in 4AR, but the upper limit is the same.  

More than half of the increase in global surface temperature from 1951 to 2010 is due to human emissions of GHGs and other manmade contributors to warming effects (95-100% likelihood). 

It is “very likely” (90-100%) that manmade contributions have led to increased heat content in the upper 700 m (2,296 ft) of the oceans.  They have also contributed to increased atmospheric moisture content, and consequent changes in precipitation including intensification of heavy precipitation over land. 

It is “very likely” (90-100%) that manmade effects have increased the frequency and intensity of extremes of temperature across the globe, probably doubling the occurrence of heat waves.  It is also “very likely” that manmade influences have contributed to loss of Arctic sea ice and the global rise in sea level.

Projections of possible future warming were carried out using a variety of models, ranging from simple climate models, to models of intermediate complexity, to comprehensive climate models, and Earth System Models.  These were run with four emissions scenarios termed RCP 2.6, RCP 4.5, RCP 6.0 and RCP 8.5.  (The numbers refer to the rate of energy increase per unit area at the surface of the earth, in watts per square meter.)  RCP2.6 is intended to project a pathway to warming equilibrium within the guideline established earlier by the IPCC to limit global warming to 2ºC (3.6ºF) above the level before industrial times.  The remaining RCP scenarios reflect worsening, more severe warming originating from increasing rates of emission of GHGs.  RCP 8.5 approximates a “business as usual” pathway in which no significant policies are implemented to limit GHG emissions through 2100.

(Temperature changes in AR5 shown below are referenced to the starting period 1986-2005.  These are 0.61ºC (1.10ºF) above the preindustrial level.  This amount should be added to all values mentioned here to arrive at the full change since the beginning of the Industrial Revolution.)

The following table shows projected temperature increases over the 1986-2005 reference, and projected increases in global mean sea level over the 1986-2005 reference.

Changes in global mean surface temperature in ºC (top) and global mean sea level rise in m (bottom) for the two time periods shown, referenced to the period 1986-2005.  The “likely range” gives confidence limits for a 5%-95% interval. 
For temperature, corresponding values for ºF are exemplified as 1ºC =1.8ºF, 2.0ºC = 3.6ºF, and 3.7ºC = 6.7ºF.

For sea level, corresponding values for feet are exemplified as 0.24 m = 0.79 ft, 0.30 m = 1.0 ft, 0.40 m = 1.3 ft, and 0.63 m = 2.1 ft.

Source: IPCC 5AR Summary for Policymakers; http://www.climatechange2013.org/images/uploads/WGIAR5-SPM_Approved27Sep2013.pdf.

 

Global maps of warming are shown below for the mildest scenario, RCP 2.6, and the most severe scenario, RCP 8.5, referenced to the period 1986-2005.

Global grid of projected temperature changes by 2081-2100 referenced to the period 1986-2005.  The changes are color coded in ºC according to the heat bar at the bottom.  The number of models used is shown at the upper right of each map.  The stippling (dot pattern) is used to show high significance of the result for the given map location above internal variation (exceeds 13-87% deviation from the mean).

Source: IPCC 5AR Summary for Policymakers; http://www.climatechange2013.org/images/uploads/WGIAR5-SPM_Approved27Sep2013.pdf.

 

It is seen that temperatures are projected to be higher over land masses than over oceans.  Also, the size of the temperature increase is highest over the Arctic in both scenarios.  The changes in the Arctic would give rise to significant losses in sea ice and ice sheet masses, and would melt permafrost.

It is “virtually certain” (99-100% likelihood) that the frequency of hot temperature extremes on both daily and seasonal timescales will increase, and that of cold temperatures will diminish.

The models project regional changes in precipitation amount over the globe.  The range of differences between wetter and dryer regions will grow, and the contrast between wet and dry seasons will increase.  Extreme precipitation events are “very likely” (90-100%) to become more frequent and more intense.

It is “very likely” that Arctic sea ice will continue to decrease, that Northern hemisphere snow cover will be reduced, and the amount of glacier ice will decrease.  Permafrost will continue melting, and large fractions will be lost, depending on the scenario.

Global mean sea level will continue rising due to increased ocean temperature (thermal expansion, 30-55%) and increased melting from glaciers (15-35%) and the Greenland ice sheet.

Oceans will continue warming.  Heat absorbed from the atmosphere will be redistributed to greater depths, affecting the long-term ocean circulation. 

© 2013 Henry Auer

The Keystone XL Pipeline Would Significantly Worsen Global Warming

Summary.  President Obama is weighing a decision whether it is in the national interest to approve the Keystone XL pipeline.  It would carry bitumen from Alberta’s tar sands to refineries on the U. S. gulf coast.  He has said he would not approve the pipeline if it would make climate change “significantly” worse.

Tar sands oil, being very different from conventional petroleum, requires far more energy, derived by burning fossil fuels, to extract it for shipment and to refine it for final use.  The high capacity of the pipeline would transport so much bitumen that, once burned as refined fuel, it would add between 82.5 million tons and 181 million metric tons per year of carbon dioxide to the atmosphere, corresponding to at least 1.4% of all emissions from the U. S. The pipeline would commit the U. S. to these emissions for each year of its operational lifetime, perhaps 40 years or more. 

Officials of the Canadian government have visited Washington several times in recent months advocating assertively for approval of the pipeline.  Clearly the Keystone XL pipeline figures importantly in Canadian political and economic considerations.  Those interests do not necessarily overlap with those of the United States.

The energy economy may be considered as a zero sum undertaking, balancing new investments in fossil fuels with those in renewable energy.  It is estimated here that if the investment in the Keystone XL pipeline were instead directed toward investment in wind energy, it could result in installation of 1,420 high capacity wind turbines and construction of a high voltage transmission line 1,563 miles long.  This investment would provide many jobs during construction, making a positive contribution to economic activity in the U. S.

The President should not approve the XL pipeline.  Instead, his administration should promote development of renewable energy sources as avidly as possible.

 

Analysis and Conclusions

 

The extent of warming of the earth’s climate depends not on humanity’s annual rates of adding new greenhouse gases to the atmosphere, but rather on the total accumulated amount of such gases added since the industrial revolution began 150 years ago.  Carbon dioxide, the main greenhouse gas, remains in the atmosphere for a century or even longer (referring to the large portion not captured by photosynthesis or absorbed into the oceans).  Therefore, even if we reduce our annual emissions rate we can never lower the accumulated total, but rather only minimize the new higher accumulated total of greenhouse gases in the atmosphere.  For this reason it is imperative to migrate away from a fossil fuel-driven energy economy as soon as possible, and shift toward a renewable energy economy.

Approving the Keystone XL pipeline would commit the U. S. to additional accumulation of new greenhouse gases from burning this fuel throughout its operational lifetime, to the extent of at least 1.4% per year of all fossil fuel derived carbon dioxide emitted by the U. S.  Thus use of Canadian bitumen for the lifetime of the pipeline would add significantly to the world’s burden of new greenhouse gases.  Additionally, extracting and refining tar sands bitumen requires large amounts of energy, which itself is derived by burning fossil fuels and creating more greenhouse gas emissions.  Accordingly, the pipeline would significantly and adversely affect global warming if it were approved.  The urgings of Canadian government officials should be rejected.  It is not in the interests of the U. S. to grant approval.

Instead, the U. S. should take every opportunity to develop renewable sources of energy that have very low or zero rates of emission of new greenhouse gases.  Government and corporate policies should be encouraged that promote migration away from fossil fuel use and toward a renewable energy economy.

 

Details

 

Introduction.  The Keystone XL pipeline (XL) is an international transport pipeline project intended to carry bitumen (Alberta tar sands oil) from the Canadian border to refineries on the U. S. Gulf Coast.  Since the project has an international aspect, involving oil transport across the Canada-U. S. border, it requires positive review by the U. S. Department of State and approval by the President.  The query to be resolved is whether this is in the national interest.

While the XL pipeline application has been pending, President Obama delivered a major speech on his energy policy on June 25, 2013.  He said he would not approve the application if the pipeline would make climate change “significantly” worse.  

Canada is aggressively promoting approval of the pipeline in numerous visits to Washington.  Alison Redford, the Provincial Premier of Alberta, visited Washington, D.C. for the fourth time in 18 months during the week of April 8, 2013 to press the case for favorable action on the XL pipeline.

On September 9, 2013 Canadian Minister of Natural Resources Joe Oliver met with U. S. Secretary of Energy Ernest Moniz.   Minister Oliver has visited Washington on numerous occasions to promote approval of the pipeline application.  In addition, Canadian Prime Minister Stephen Harper is reported to have sent a letter to President Obama in August 2013 in which Mr. Harper proposed "joint action to reduce greenhouse gas emissions in the oil and gas sector."  By this gesture he seeks to further approval of the pipeline application.  This offer is a concession to U. S. concerns about greenhouse gases that Canada has not previously made.

The New York Times reported on August 25, 2013 that Canada would find other modes of transporting the bitumen to the U. S. market and/or other destinations for the bitumen if the XL pipeline application is rejected.   Nevertheless, internal Canadian government documents released to the Canadian Pembina Institute reveal that Canada has been relying on approval to expand production of bitumen from the tar sands.

[Update September 22, 2013]  An editorial contributor to the New York Times reports that the Canadian government is restraining government scientists from free and open communication of their findings, especially in the fields of climate change, the Alberta tar sands, and fisheries.  The writer concludes “the Harper [Canada’s prime minister] policy seems designed to make sure that the tar sands project proceeds quietly, with no surprises, no bad news, no alarms from government scientists.”

 
It is clear that approval of the Keystone XL pipeline is a major issue in Canada, both politically and economically.

Characteristics of bitumen.  Bitumen occurs as a highly viscous fluid or a soft solid, mixed with sand.  Extracting tar sands bitumen deposited near the surface requires expending about 20% of the energy content of the bitumen.  Deeper reservoirs require about 30% of the energy contained in it.  Obtaining conventional oil, on the other hand, needs only about 4%. Bringing the bitumen to the surface and freeing it from the sand mixture requires heating the raw material to temperatures hot enough that the bitumen flows more freely.  The process produces waste water that now includes toxic heavy metals and bitumen components that have to be stored to keep the waste from contaminating running streams. 

Refining tar sands bitumen takes extra processing compared to refining conventional petroleum.  The additional steps require additional large amounts of energy and use large amounts of water.

In summary, extracting and refining tar sands bitumen is far more energy intensive than recovering and refining conventional petroleum.

The Keystone XL pipeline is expected to transport 830,000 barrels of fuel a day.  Refining petroleum yields about 75% of carbon-containing fractions that are suitable for use as fuels.  Although bitumen is different than petroleum, If bitumen provides the same yield, this writer estimates conservatively that the annual amount of fuel transported would emit 82.5 million tons of carbon dioxide (CO₂) a year when burned.  (This figure does not include the extra emissions arising from the energy used in extraction and refining.) This works out to this pipeline alone transporting fuel that would emit 1.4% of all CO₂ produced by burning fossil fuels in the U. S. (fossil fuel data).  Another report estimates annual emissions to be 181 million metric tons per year, or more than twice as much as the lower estimate.  These emissions would continue for the useful service lifetime of the pipeline, perhaps 40 years or more.  Not approving the pipeline and not extracting this amount of bitumen would prevent this amount of emissions indefinitely into the future.

Continuing fossil fuel use, such as by building the XL pipeline, is but one arm of the energy economy’s zero sum undertaking.  In weighing whether to approve the Keystone XL pipeline, the choice is not whether to approve it or simply to reject it.  Rather the correct decision to consider is whether to use the funds foreseen for the Keystone XL investment, prolonging the fossil fuel energy economy, or to shift such investment to expand renewable energy.  A current estimate of the cost of constructing the XL portion of the Keystone system is US$7 billion.  Earlier phases of the Keystone system experienced cost overruns of as much as 100%; if so, the XL portion under consideration could cost as much as US$14 billion.

As noted above, the pipeline, if built, commits us to continued atmospheric emissions of CO₂ over its full service lifetime, perhaps 40 years or more.  If the pipeline were not built and its intended capacity for bitumen remained in the ground, emissions equal to about 1.4%/yr of the U. S. total would be avoided.  The longer we delay the abatement of emissions, the more intensive and more expensive mitigation efforts would need to be.

Renewable energy is a second arm in a zero sum energy economy.  An alternative strategy is to shift the US$7-14 billion investment envisioned for the pipeline into developing industrial scale, renewable energy sources and energy transmission infrastructure. We should stop harvesting tar sands oil and build wind farms and solar farms instead.  We should reject new oil pipelines in favor of new transmission lines to deliver electricity from those farms to energy consumers.

The cost of wind energy generation is falling dramatically each year.  A report from the Lawrence Berkeley National Laboratory, a facility of the U. S. Department of Energy, reports that the levelized cost of electricity from wind (a measure of the expense incorporating all costs  throughout the lifetime of a project) ranges from US$20 to US$40 per MWh (megawatt-hour, a unit measuring the amount of energy).  It is lowest in the windy portion of the U. S., the Midwest interior. Broadly, this is the region that the projected Keystone XL pipeline would traverse.  

Construction costs for wind energy based on generation capacity are as low as about US$1,760/kW (kilowatt, a unit of power, or the rate of generating energy in a fixed time).  The average capacity of installed individual turbines was almost 2 MW in 2012.  Wind power provides an important source of jobs in the U. S. economy, since the domestic content of turbines increased from 25% in 2006-2007 to 72% in 2012.

We need new high voltage transmission lines to carry power from a renewable facility to consumers.  The American Electric Power Company estimates costs for constructing a lower-voltage line (345 kV) at about US$1.1-2.0 million (2008 dollars) per mile, and for the highest voltage listed (765 kV), a cost of US$2.6-4.0 million per mile.  Most of this expense comes from direct labor costs (construction, 41%; siting and management, 8%) and in labor involved in providing the materials (the materials cost is given as 41% of the total).  Thus it is seen that constructing a high voltage transmission line provides a large number of high-skilled jobs during the project.

Substituting investment in wind energy for the Keystone XL pipeline provides a high amount of installed capacity.  This writer has estimated investing in wind energy for a cost, US$10 billion, intermediate between the stated cost of the XL pipeline, US$7 billion, and a 100% cost overrun.  The sum is divided evenly between wind turbines and a transmission line.  Using the information above it is calculated that

investing in 2MW turbines would provide 1,420 turbines; and

investing in a 765 kV transmission line would provide 1,563 miles.

Turbines with even larger power capacities are currently becoming available.  Turbines that can operate at low wind speeds with high efficiency are available.  Wind turbines have to be installed with wide separations, so that original use is retained for a large fraction of the land that the wind farm occupies.

It is concluded that investing in the Keystone XL pipeline is not in the national interest of the U. S., as it contributes significantly to worsening the problem of global warming.  Investment should be directed instead to renewable energy sources, such as industrial wind farms described here, solar farms and the like.

 

© 2013 Henry Auer