See the Tabbed Pages for links to video tutorials, and a linked list of post titles grouped by topic.

This blog is expressly directed to readers who do not have strong training or backgrounds in science, with the intent of helping them grasp the underpinnings of this important issue. I'm going to present an ongoing series of posts that will develop various aspects of the science of global warming, its causes and possible methods for minimizing its advance and overcoming at least partially its detrimental effects.

Each post will begin with a capsule summary. It will then proceed with captioned sections to amplify and justify the statements and conclusions of the summary. I'll present images and tables where helpful to develop a point, since "a picture is worth a thousand words".

Friday, July 22, 2011

Summer Heat Waves, Carbon Storage and Natural Gas

Summary.  Man-made emissions of greenhouse gases are producing higher long-term global average temperatures.  A New York Times Op-Ed discusses a new normal of increased average global temperature accompanied by more, and more serious, extreme weather events with damaging consequences.  An editorial in the New York Times describes how a pilot project for CO2 underground storage, which could reduce emissions, lost U. S. federal funding because of Congressional inaction.  A display ad by Chesapeake Energy, and its web site, describe the company’s new funding for projects to develop natural gas as a domestic American fossil fuel to replace imported oil.

Analogies are presented to illustrate that even if mankind stopped emitting new CO2 now, the present level of warming and its attendant spawning of extreme weather events would still be with us.  A peer-reviewed article by Davis and coworkers concludes that even if mankind ceased putting new fossil fueled equipment into service, fuelling the existing equipment would still lead to increased atmospheric CO2 with its attendant harmful weather consequences.  It is concluded that we must move toward a zero-emissions energy economy as soon as possible.

Introduction.  An overwhelming majority of the world’s climate scientists support the conclusion that man-made emissions of greenhouse gases are producing higher long-term global average temperatures.  This increase leads to more occurrences of short-term extreme weather events, carrying with them significant financial, humanitarian and societal harms.

In this post we consider first, an Op-Ed article by the climate scientist Heidi Cullen; second, an editorial describing termination of U. S. federal support for a pilot project whose goal had been developing viable technology to store the greenhouse gas CO2 underground for geologically long time periods; and third, an effort announced by Chesapeake Energy to produce natural gas domestically in the U. S. as a replacement for imported petroleum based fuels.

In an Op-Ed in the New York Times of July 20, 2011, Heidi Cullen of Climate Central summarizes a recent report of the U. S. National Oceanic and Atmospheric Administration (for a preliminary version, see here).  The report redefines “normal” temperatures upward as a result of higher temperatures recorded over the last 30 years in the U. S.  It finds that the last 10 years in the U. S. were about 1.5ºF warmer than in the 1970s.  Furthermore, the U. S. National Center for Atmospheric Research found that heat waves and damaging rainfall could cause as much as US$485 billion in losses from crop damage, construction delays and disrupted travel.

Ms. Cullen continues that climate scientists, using a statistical method intended to identify causes, have determined that mankind’s burning of fossil fuels that yield greenhouse gases has led to the warming of the climate, and, just as importantly, to the occurrence of extreme events such as the severe 2003 European heat wave.  It is expected that this trend will continue.

Our earlier post entitled “Global Warming Is Responsible For Extreme Rainfall” summarizes two reports in the journal Nature in February 2011 that apply similar methods to ascribe unambiguously, for the first time, extreme rainfall events and flooding that occurred in 2000 and earlier directly to the effects of man-made global warming.  In addition, a report entitled “The Hot Summer of 2010: Redrawing the Temperature Record Map of Europe”  published in the journal Science (see Note 1) in April 2011 concluded that extreme heat waves such as experienced over 50% of Europe in 2003 and 2010 exceeded 500 year old temperature records.  Similar events are predicted in the future using climate models that include a “scenario” of increasing greenhouse gas levels.  In view of the scenario, the predicted behavior can be directly attributed to increases in atmospheric greenhouse gases arising from fossil fuels.

Also in the New York Times of July 20, 2011 an editorial entitled "Blame Congress” discusses the termination of a commercial pilot project on underground storage of CO2 at an American coal-burning electricity plant.  Burning coal produces more CO2 per unit of heat obtained than does the burning of other fossil fuels.  Therefore it would be important to find a way to capture the CO2 and store it permanently underground in suitable geologic formations, instead of releasing it to the atmosphere.

This project originally received significant funding from the U. S. Department of Energy.  Energy legislation that would have provided economic incentives for innovative projects such as this has recently failed in Congress.  As a result, no funding is available any more, and the project is held up.  The industry relies on federal funding for such development projects aimed at reducing  greenhouse gas emissions.

Chesapeake Energy.  In the same issue of the Times, Chesapeake Energy displays a full-page advertisement on American energy independence.  The company announced three initiatives that it says will reduce America’s dependence on imported oil.  These are 1) extracting 50% more oil and natural gas domestically using horizontal drilling and hydraulic fracturing; 2) providing a US$150 million investment in Clean Energy Fuels Corp. to install liquefied natural gas fueling capability in filling stations in the U. S.; and 3) providing a US$155 million investment in Sundrop Fuels, Inc. to produce nonfood biomass-based alternative gasoline fuel derived from natural gas and waste cellulosic material.

The company will divert 1-2% of its annual drilling expenditures to these projects for the next 10 years.  It intends to stimulate acceptance of natural gas and gas-to-liquid fuels in the U. S.   Burning natural gas in place of diesel and gasoline  reduces CO2 emissions by about 40% (still, burning natural gas, a carbon-containing fossil fuel, does not totally eliminate greenhouse gas emissions).


Atmospheric concentration of CO2.  Worldwide the burning of fossil fuels for energy continues to increase.  The atmospheric concentration of CO2 accordingly continues to increase as well, by about 2 parts per million (ppm; parts by volume of CO2 gas per million parts by volume of air total) per year, and presently stands at 391 ppm. The increase in CO2 from 1958, measured at Mauna Loa in Hawaii, is shown below (the red line is the averaged curve from monthly data).

It should be noted that, rather than being a straight line, the curve actually bends upward because emissions are increasing each year.

Ms. Cullen’s Op-Ed article emphasizes the need to minimize new emissions of greenhouse gases, indeed to reduce them to zero, as soon as possible.  This is because the atmosphere retains the CO2 released for very long times, on the order of 100 years or more.  (See Note 2)  Essentially all the gas released today will still be in the atmosphere a century from now.  There is no natural mechanism known that depletes CO2 from the atmosphere once released into it.

The CO2 bathtub.  A simple model for atmospheric CO2 is a bathtub containing CO2.  Its faucet continues filling the tub with more CO2 (from continued burning of fossil fuels), but the drain mechanism is essentially plugged, so virtually no CO2 leaves the bathtub (our atmosphere).  As a result, the CO2 level has increased from about 280 ppm

before the industrial revolution began to 390 ppm today.  Even if no further CO2 is added, by turning off the faucet, the earth’s atmosphere already has an elevated level of CO2 which has already increased the average global temperatur and produced extreme weather events.  These would not cease even if mankind stopped now to emit all new CO2. Although this ideal cessation  is not possible, it behooves mankind to minimize new CO2 emissions as soon as possible. (See Note 3)

The fiscal analogy.  Another analogy to global climate change is drawn from the the current U. S. budgetary drama.  In fiscal terms, the analog of yearly increases in atmospheric CO2 levels is the yearly deficit in the budget of the U. S. federal government.  Each year’s deficit is added to the total deficits accumulated over the preceding years; this accumulated deficit is the U. S. national debt.  The national debt is the analog of the total concentration of CO2 already in the atmosphere.  Even if the deficit were reduced to zero next year (no new emissions), the total national debt (atmospheric CO2) would still be there. 

These analogies indicate that the people of the world should be striving to bring new emissions of CO2 close to zero as soon as possible. 

Global average temperature will increase due to existing fossil fuel-burning installations. In 2010 in Science, Davis, Caldeira and Matthews (see Note 1) assessed the future production of atmospheric CO2 and its effect on global temperature from only fossil fuel-burning equipment already in place.  Their analysis predicts that atmospheric CO2 will increase from the present 390 ppm, to a predicted maximum of about 412 ppm at about 2037.  After 2037 the predicted CO2 concentration falls slightly to about 408 ppm by 2060. (See Panel C from Fig. 1 of Davis and coworkers below). 

© American Association for the Advancement of Science.  The upper and lower line projections relate to upper and lower bound estimates by Davis and coworkers for the reduction in CO2 emissions over the time period to 2060.

The current average global temperature is about 0.7ºC (1.3ºF) higher than it was in preindustrial times due to increased atmospheric CO2 emitted since 1850.  Davis and coworkers predict that as a result of the continued emission of CO2 from only existing installations (Panel C above) the average global temperature will continue to rise slowly over the next 50 years, reaching 1.3ºC (2.3ºF) above average preindustrial temperature by 2060, according to the Middle scenario. (See Panel D from their Fig. 1, above).  Thus even if we were to cease building new power plants and cars, global temperature would continue rising.  This scientific assessment by Davis and coworkers amplifies the simple bathtub and fiscal analogies presented above.

The U. S. has no national energy policy in place, as detailed in the New York Times editorial described above.  This void is currently filled by various state and regional greenhouse gas reduction initiatives, including California’s plan, the Western Climate Initiative, the Midwest Greenhouse Gas Reduction Accord, and the New England and mid-Atlantic Regional Greenhouse Gas Initiative.  These programs have varying levels of coverage and differing terms of duration.  In the absence of federal legislation governing energy policy, the Obama administration is implementing various policies by executive and administrative actions.

Is Natural Gas A Long-Term Solution?   The energy industry is promoting natural gas as a way to achieve American independence from reliance on imported petroleum, and as a “clean” fuel.  (See the earlier post “Producing More Natural Gas in the U. S.: The Pickens Plan. )  Coal is the worst of the fossil fuels, producing the most CO2 for a given amount of heat energy released.  Natural gas is the most efficient of the fossil fuels, emitting the least CO2 for the amount of heat energy obtained.  It is called “clean”-burning for this reason, and because it emits no mercury and sulfur dioxide as pollutants, in contrast to coal. Nevertheless, natural gas still emits large amounts of CO2 on burning. 
Natural gas is an abundant domestic fuel resource, especially with the development in recent years of hydraulic fracturing technology (“fracking”) to extract it from gas-containing shale formations that occur widely in the U. S.  At least one major oil company, Shell, is actively producing natural gas as a supplement to extracting crude oil.  In 2012 the company will produce more natural gas than petroleum. 

Problems with Natural Gas. The problems with natural gas are two-fold.  Natural gas (i.e., methane) is itself a greenhouse gas which is 25 times as potent a greenhouse gas as CO2.  The New York Times on April 11th, 2011 reported that natural gas wells, especially those using hydraulic fracturing, leak significant amounts of methane into the atmosphere.  These wells therefore worsen the global warming conundrum, rather than help it.

Also, fracking uses toxic chemicals in water to get the gas out.  Unfortunately the chemicals, as well as toxic substances (metals, radionuclides) leached from the shale, may contaminate ground water and may be released into surface waste water. 

The Pickens Plan for Use of Natural Gas in Transportation.  T. Boone Pickens, a oil and gas businessman, recognizes the disadvantage that the U. S. has with its energy economy, transferring about $220 billion a year to the Organization of Petroleum Exporting Countries alone.  Pickens has responded to this situation with a plan to develop natural gas and alternative energy domestically in the U. S. in order to reduce our dependence on imported petroleum.  He believes that natural gas can serve as a bridge fuel that is more advantageous than using gasoline and diesel made from imported crude oil.

Mr. Pickens has promoted the New Alternative Transportation to Give Americans Solutions Act of 2011 (H.R. 1380).  The bill offers tax credits to promote domestic production and distribution of natural gas, as well as the production and purchase of vehicles capable of using it.

Chesapeake Energy seeks to expand use of domestically produced natural gas instead of imported petroleum based fuels such as diesel and gasoline in transportation.  It will commit 1-2% of its drilling budget to the projects itemized above, amounting to at least US$1 billion over 10 years.  This means that its expected drilling budget overall will be US$50-100 billion, a very large expenditure indeed, over this period.  Contrary to Mr. Pickens, Chesapeake Energy appears, at least in its press release, not to view its new investments as a step along a transitional path to abandoning fossil fuel use.  This may be true for Shell as well.  Commitment to major investments in new gas wells likely is not undertaken with a view to phasing them out before the end of their useful lifetimes.

Conclusion.  Increases in the average global temperature, arising from mankind’s burning of fossil fuels for energy since the onset of the industrial revolution, is upon us.  The rate of burning fossil fuels has been increasing, as has the corresponding increase in the concentration of atmospheric CO2. 
Heidi Cullen’s Op-Ed spotlights the need for world-wide action to curb further emissions of CO2 and other greenhouse gases.  She emphasizes the occurrence of extreme weather events, whose frequency is projected to increase with the increase in atmospheric greenhouse gases.   The New York Times laments the cessation of a federally-subsidized pilot project that might have led to a technology for constraining emissions of CO2.

The energy industry is rapidly developing natural gas contained in shale formations.  In the U. S. development of domestic energy resources is intended to eliminate dependence on imported petroleum.  It is not clear whether this new drilling activity is viewed as an interim phase which will be phased out as we move more comprehensively to renewable sources of energy.

Yet the work of climate scientists such as Davis and coworkers clearly shows the necessity of attaining a worldwide energy economy that is free of greenhouse gas emission as soon as possible.  The analogies provided by the bathtub model and the budget model help drive home this urgent need.  Since natural gas produces major amounts of CO2 when burned, it should not be considered to be a long-term solution, but at best only a temporary crutch to lean on as the world progresses to a fully renewable and alternative energy economy.


Note 1. Abstract available free; full article available online for a fee or through personal or institutional subscription.  Many public libraries, and university libraries open to the public, receive the journal.

Note 2. About 30% of released CO2 dissolves in the oceans; this fraction essentially does not change.  Thus the comments presented here refer to the remaining 70% which stays in the atmosphere.

Note 3. It would be beneficial to be able to remove CO2 already in the atmosphere in order to reduce its concentration.  Currently there is no engineering solution that would succeed in accomplishing this worthy objective.  Reforestation is one way of achieving this objective.

© 2011 Henry Auer

Friday, July 15, 2011

Economics of Renewable Energy

Summary:  In the U. S. regional and state initiatives are in place aiming to reduce emissions of greenhouse gases significantly.  Use of renewable energy sources plays a prominent role in these programs.  This post presents a discussion of wind energy, solar photovoltaic electricity, and solar thermal electricity, focusing on the economics of utility-scale projects.  Generally, each of these modalities has already attained, or is projected to attain, economic competitiveness with fossil fuel-driven electricity generation, based on evaluation of the “levelized cost” of electricity.  A previous post on this blog presented the harsh economic and humanitarian costs arising from extreme weather events tied at least partly to global warming.  Here it is concluded that those costs and the investments needed to construct renewable energy facilities are broadly comparable.  Renewable energy is preferable in order to mitigate the need for dealing with the harms caused by extreme weather events. 

Introduction.  Warming of the long-term average worldwide temperature due to accumulation of greenhouse gases such as those that result from burning fossil fuels has been proceeding with increasing severity in recent decades.  In a recent post entitled “Economic Costs of Extreme Weather Events Due to Global Warming” we assessed the economic impact of three events tied to extremes of weather that could be ascribed at least partly to global warming.

The U. S. has failed to implement a national energy policy that addresses global warming.  In the face of this void some regions and states in the U. S.  have implemented their own initiatives to reduce greenhouse gas emissions and to seek to mitigate global warming.  For example, the state of California, both by itself and as part of the Western Climate Initiative, is actively taking steps to limit its greenhouse gas emissions, including the solar power projects described below.  Expanding renewable sources for electricity is an important aspect of such programs.  Here we assess economics and energetics of three types of renewable energy, wind power, solar photovoltaic electricity and solar thermal generation.  (The discussion of these topics is relatively lengthy.  Some readers may wish to jump directly to the Conclusion section at the end.)

Renewable sources of energy in the U. S., as of 2009, constituted 8% of the total supply, according to the U. S. Energy Information Agency’s Annual Energy Outlook 2011 (AEO).  Nuclear energy, which is not responsible for any greenhouse gas emissions once the plants are in operation, accounts for 9%. (Manufacture of cement, and refining of metals, which are used in construction, are both very greenhouse gas-intensive.)  The predicted levelized costs of generating electricity (see indent following the graphic) from coal, uranium, wind, and natural gas using a combined cycle generator are shown below, for the years 2020 and 2035.

Price in cents per kWhr for electricity generated from four sources predicted for 2020 and 2035.  The contributing factors are blue, capital costs; green, fixed costs; magenta, fuel and other varying costs; and orange, incremental transmission costs.
Source: U. S. EIA, Annual Energy Outlook 2011;

Levelized Cost of Generating Electricity models the expected cost including all factors over the operating lifetime of a project.  A model includes the capital cost and the future discounted cost of the capital, any investment tax credits and preferential land use credits, fuel costs where applicable, the expected lifetime of the installed facility, its peak power output, the capacity factor accounting for the fraction of the time that power is actually generated, operating and maintenance costs, and transmission and distribution costs.  In the case of fossil fuels, the levelized cost does not include costs associated with considering waste CO2 as a greenhouse gas and its harmful effects on global warming.
Considering the levelized cost for wind power in the graphic above, the capital costs decrease from 2020 to 2035, presumably as more units are installed leading to economies of scale.  Importantly, wind power has no variable costs such as those arising from fuel costs.  The transmission costs are greatest for wind power of all those shown, perhaps because wind installations require completely new transmission lines.  For natural gas, using a combined cycle generator (one in which gas is first burned in a jet engine-like turbine, then the hot exhaust gases are used to heat water to steam, producing additional turbine-driven power) the levelized costs remain approximately unchanged between 2020 and 2035.  The biggest expense in natural gas is the price of the fuel, which can be quite volatile.  The cost for the other three modalities decreases significantly between 2020 and 2035.

The graphic below shows that the projected contributions in 2020, 2030, and 2035 of generating capacity from geothermal power, solar power, biomass-fueled generation and wind power all increase significantly over the actual 2009 level, as reported by the AEO.

Sources for renewable electric power generating capacity. Black, municipal solid waste/landfill gas (MSW/LFG); brown, geothermal energy; orange, solar; light blue, biomass; and green, wind. Source: U. S. EIA, Annual Energy Outlook 2011;

In the graphic above, wind energy is shown as remaining relatively constant in the future years.  The AEO’s projection giving this result is based on expiration of an investment tax credit for wind energy before 2020, which discourages projected further development of wind.

Considering the total amount of electric generation in the U. S. in 2009, nuclear energy provided 20%, hydroelectric generation provided 7%, wind provided 1.8%, geothermal generation provided 0.2%, and solar provided 0.02% (USEIA).

Wind Energy.  According to the American Wind Energy Association’s (AWEA) Annual Market Report for 2009, more than 10,000 MW of wind generating capacity was constructed that year (see the left-hand multicolored bar for 2009 in the graphic below).

Annual additions of generating capacity (blue and multicolored bars), and cumulative total of installed generating capacity (green bars) from 1995 to 2009.

AWEA points out that wind power capacity installed in 2009 represented 39% of all new generating capacity added during that year. 

The wind industry employed 85,000 people in the U.S. in 2009.  There were over 200 operating facilities manufacturing wind energy equipment in the U. S.  Nine corporations making wind turbines share the market currently.

Cost of wind energy.  Specifying costs for installing utility-scale wind turbines results in varying numbers.  Factors included in arriving at final numbers may differ regionally and over time.  The first graphic above shows that wind energy is fully competitive with coal-fired power, and becomes more competitive with natural gas by 2035.  Here are some additional examples of identified costs for onshore (land-based) facilities.

Wikipedia provides an estimate by the British Wind Energy Association for wind generated energy (see Details below for the distinction between electrical power and electrical energy) of US$0.05-0.06/kW-h as of 2005.  Such a cost basis was evaluated as being comparable to the energy cost from new coal- or natural gas-fired plants providing electrical energy.  These costs for fossil fuels do not include recognizing that the CO2 produced by burning fossil fuels is a waste product responsible for global warming which creates further economic costs and societal harms (see the post “Carbon Dioxide – The Waste Product of Our Energy Economy”).  In addition, in the U. S. generation of electricity by wind entitles the producer to a Production Tax Credit of US$0.01/kW-h. 

Clipper Windpower, Inc. reports that from 1989 to 2004, as exemplary wind turbines increased in rated power output from 25 kW to 1,500 kW the cost fell from $2,600/kW of capacity to $800/kW.  The overall cost of electrical energy is calculated as US$0.0617 per kWh in 2004 before the production tax credit. New technologies have improved the efficiency of generation as well as the ability to interface with the electrical grid. 


The rate of delivering electricity is the power, identified in watts, kilowatts (thousands of watts; kW), megawatts (millions of watts; MW) or gigawatts (billions of watts; GW).  The energy delivered is the power averaged over time, or watt-hours (w-h), or KW-h, or MW-h. 

 AWEA offers a detailed list of considerations in creating a wind farm project.
Understand the wind pattern.  A minimum average wind speed of 11-13 miles per hour (mph) is needed.
Distance from existing grid lines.  Transmission lines cost several thousand dollars (US) per mile.  Siting should minimize this distance.
Access to land. Arrangements for land use, whether public or private, need to be made.  During construction, load-bearing roads need to be available or built.  Local opinion should be favorable.
Arranging capital.  As of 2009, AWEA estimates wind power requires about US$2 million per MW of power generating capacity, installed.  For economies of scale, a project should include several turbines, say at least 20 MW, translating to a cost of US$40 million.
Contract for a buyer of the generated power.  Long term purchase commitments should be arranged, covering an operational lifetime of up to 30 years.
Siting arrangements.  This factor includes considerations such as visual and sound esthetics, multiple uses for the land, environmental regulations, and community acceptance.
Wind energy economics.  Wind speed and rotor length affect the amount of power generated.  Financing modalities, including interest rates and investor relations, affect overall profitability.
Zoning and environmental permitting.  This is a major ancillary requirement that needs to be satisfied before a project can begin.
Understand the characteristics of the turbines.  Various models and designs for turbines exist.  These should be explored and understood.
Make arrangements for operation and maintenance.  Reliability of turbines installed is important.  Qualified operators and service personnel should also be available.

As discussed by Wikipedia, a wind turbine, or turbine farm, produces only a fraction, called the capacity factor, of the total possible energy that could be generated, because of the intermittency of the wind, and because the grid load may not require the full power at all times.  Typical capacity factors range from 20% to 40%.  According to the U. S. Department of Energy’s Office of Energy Efficiency and Renewable Energy, new wind turbines achieve capacity factors of 36%.  Let’s assume 35%, so averaged over one year a 1 MW turbine will actually deliver power at 0.35 MW, and provide a total amount of energy of 0.35 MW x 24 hrs/day x 365 days/yr, or 3,066 MW-h. 

Solar Photovoltaic Renewable Energy.  There are two differing approaches to using solar energy for electric power.  Photovoltaic (PV) energy uses semiconductor films, made of ultra-pure silicon, to convert the sun’s energy directly into electricity.  Solar thermal energy uses extensive arrays of mirrors to concentrate sunlight onto a single heat-absorbing element containing a high-boiling heat exchange liquid.  The liquid then heats water to steam which drives a turbine to generate electricity.  Both modalities require large land areas to provide enough generating scale to be commercially significant.

About half the cost of solar PV is consumed by the silicon PV elements themselves.  Solar PV produces direct current (like a simple battery).  In order to be introduced into the commercial power grid, this has to be converted into alternating current using a device called an inverter.  In order to minimize equipment failures many inverters are used to connect a relatively small number of PV cells.  Much of the remaining cost of solar PV is taken up by the inverters, the circuits controlling their operation, and the cabling that connects them. 

In a recent description of a solar PV project, Solargen Energy Inc. summarized its new installation using land under existing power transmission lines.   Its cost is minimized because the company uses newly-developed thin-film silicon PV cells, which can be as much as 99% cheaper than older conventional PV cells.  For this project Solargen states

The project installs 250 MW of solar PV capacity, which is expandable to 1,500 MW;
          It requires 1,000 acres;
          It uses 550,000 thin-film solar PV panels;
          Its cost is $750 million; and
          It has contracted for at least 20 years of delivery of the resulting power.

This project is to be installed in California’s Central Valley.  Because of California’s renewable energy policy, and federal tax credits, there is considerable incentive for developing renewable energy sources such as this.  In addition, as solar PV is expected to expand, its cost per installed watt capacity is expected to fall.

The U. S. Department of Energy announced on June 30, 2011 that it is offering conditional commitments for partial loan guarantees totaling almost US$4.5 billion for three solar PV projects in California.  The projects utilize cadmium-telluride PV films made by First Solar, Inc., rather than the more usual silicon.  When completed, the projects together will generate solar electricity using utility-scale inverters for stable continuous delivery of power to grid power companies.  The total power rating is expected to be 1,330 MW (1.33 GW), which should deliver enough electricity for 274,000 homes.  During construction these projects will create 1,400 jobs for electrical and installation work, and subsequently additional jobs for maintenance and operation.  It is expected these farms will eliminate 1,810,000 metric tons of CO2 emissions per year.

The National Renewable Energy Laboratory (NREL) published an analysis of solar PV in February 2011.  We will focus here on utility-scale solar PV.  NREL analyzes that the cost per watt for installing solar PV facilities falls dramatically with the scale of the project (see the graphic below, in which both axes are logarithmic scales)

The solid and dashed red lines refer to utility-scale solar PV farms, showing the installed system cost in US$/watt of peak DC electric capacity (before conversion to AC and feeding to the grid).  Both the capacity axis (horizontal) and the cost axis (vertical) are on a logarithmic scale.
Source: National Renewable Energy Laboratory, U. S. Department of Energy

The various factors involved in contributing to the cost of a utility-scale PV farm are shown in the following graphic, referring to the three bars on the right for, respectively, silicon PV with fixed mirrors, silicon PV with moveable mirrors, and cadmium telluride PV with fixed mirrors.

Cost factors contributing to the installed cost of a utility-scale solar PV farm (187.5 MW), referring to the three right-most bars.  The contributing factors, reading from bottom to top of each bar, are costs for the solar PV module, the DC-to-AC inverter, installation materials, a tracker (purple, only in the fourth bar, turning the panels to face the sun), installation labor, permitting & commissioning, land acquisition, site preparation, contractor overhead and profit, and sales tax at 5%.
Source: National Renewable Energy Laboratory, U. S. Department of Energy

NREL also assessed the labor effort that would be needed for a 317,000 kW (peak DC) project.  Hours of effort for electrical work amount to 1,784,483, or almost 900 person-years, and for hardware hours, 544,735, or 272 person-years.  Each person-year corresponds to a new construction job for one year.  Additionally, considering all contributors to construction such as itemized in the legend to the graphic above, NREL estimates that the overall installed cost would be US$4.40 per watt at peak capacity, DC (before conversion to AC for delivery to the grid; this is not a levelized cost for energy).  The NREL presentation offers several cost factors that can be further optimized to achieve cost reductions from this level.

Solar Thermal Electricity.  An alternative way of capturing the energy of the sun is by solar thermal power plants, or concentrated solar power.  Although there are several variants of this method, its central feature is use of large arrays of mirrors to focus sunlight onto fixture containing  a circulating receiving fluid.  The fluid may be a high-boiling oil, or a pure melted salt.  It is heated to very high temperature by the focused sunlight.  The heated fluid is passed through a heat exchanger that converts water to steam for use in driving a conventional turbine to generate electricity.  Since the turbine produces AC power, no inverter is needed.  In addition, the heated receiving fluid can be stored for generating power at night.

An example of a solar thermal installation currently marketed includes several modular heliostat mirror arrays focused on a tower with heated fluid.  Each modular array has a capacity of 33 MW, and one installation can attain as high as 500 MW using many modules. 

The Mojave Desert region of California has had pilot solar thermal plants since the 1980s; many have been successful and have since been decommissioned.  Two solar thermal facilities currently being installed are discussed here.  The Blythe Solar Power Project, operated by a subsidiary of Solar Trust of America,  has four separate plants whose total generating capacity will be just under 1,000 MW, and whose rated energy will be 2,200,000 MW-h per year.  It will be the largest solar thermal plant in the world when completed.  Instead of a tower, it uses parabolic trough mirrors to focus light on pipes containing the circulating heat exchange fluid.  Its final cost is estimated at US$5-6 billion, and it will be located on over 7,000 acres (10.9 sq. mi; 28.4 sq. km) of federal land.  It has an agreement with Southern California Edison which will purchase the generated electricity.  The first of the four plants is scheduled for completion in the 4th quarter, 2013.

Its economic and environmental benefits include, for the four plants:
• Over 1,100 jobs during approximately a 3-year construction period;
• More than 220 permanent operations and maintenance jobs during its 30-year rated plant life;
• Annual economic impact of more than $135 million during construction period;
• Estimated annual economic benefit of more than $28 million during operation;
• Approximately 884,000 tons of CO2 emissions avoided  per year;
• Approximately 680 tons of NOx emissions per year avoided; and
• Approximately 585 tons of SOx emissions per year avoided

The second solar thermal plant is the Ivanpah solar tower facility, intended to have a capacity of 370 MW.  Seven other solar thermal were also under consideration during 2010 by California’s Energy Commission.  If all nine projects are approved, they would add 4,300 MW of solar electricity, creating 8,000 construction jobs and 1,000 operational jobs.  All were being considered during 2010 in order to qualify for federal American Recovery and Reinvestment Act (economic stimulus) funding.  The Blythe project is receiving a US$2.1 billion loan guarantee from the U. S. Department of Energy, and the Ivanpah project has a US$1.37 billion loan guarantee.

Levelized Cost of Solar Thermal Electricity.  A Wikipedia entry discussing solar thermal energy, after a long discussion considering factors such as those discussed earlier, arrives at a levelized cost of about US$0.10 per kWh.

A 675 MW tandem solar thermal facility under development west of Cuddleback Dry Lake, in the Mojave Desert (posted 11/05/2007), is to be run by Solar MW Energy, Inc. and affiliate Ecosystem Solar Electric Corp.  One plant will operate directly during daylight, and the second plant using stored molten salt heated during the day will operate at night.  A waste heat recovery system permits combined cycle operation throughout the 24 hour daily cycle.  The post states that as a result of these efficiencies, the levelized cost of electricity will be half that of other solar farms, noting an envisioned cost of US$0.06 per kWh.  The power is expected to be sufficient for over a half million homes and businesses.

Conclusions.  The earlier post on economic costs of extreme weather events discussed three anecdotal examples of consequences of extreme weather events which are, or may be considered to be, due at least partly to global warming.  Global warming is a change in climate which is determined over years and over the entire planet.  Nevertheless, single extreme events are considered consistent with the predictions of models for global warming that lead to the phenomena experienced in these anecdotal examples.  The examples chosen show that each in its own way brought enormous economic costs, humanitarian distress and long-lasting environmental effects, and that at least a part of those costs can be ascribed to global warming. 

In this post we have tried to show, again by anecdotal example, that planned expenditures (or rather investments) have total costs that are in the same range as damages created by various anecdotal extreme weather events.  These investments can be used to develop renewable energy sources whose effects will be to mitigate the worsening of global warming.  In addition, the examples show that each modality, wind turbine farms, solar PV farms and solar thermal facilities, has levelized costs of electricity estimated to be comparable to those of nuclear energy, for example, and to fossil fuel-derived generation of electricity (see the earlier graphic).  As already noted, the levelized costs for fossil fuel-powered generation do not account for the harms ascribed to CO2 as a waste product such as the costs of the extreme weather anecdotes described in the earlier post.  If these were included, the levelized cost of electricity for fossil fuels would be higher.  In addition, it is important that renewable energy projects create new jobs in the economy, both during construction and throughout the operating lifetime of the project.

The earlier post on economic costs of extreme events and the present post consider the relative costs of dealing with catastrophic disasters arising from extreme weather events on an unpredictable, emergency basis on the one hand, and making rational long-term plans for mitigating global warming by investing in new renewable energy sources on the other.  The latter course is the better  one to follow, for it confers significant economic and societal benefits that are absent in emergency responses to catastrophic climate-induced disasters.

© 2011 Henry Auer

Friday, July 8, 2011

President Obama Considers Increasing the Fuel Economy Standard for Cars

Summary:  The New York Times reports that President Obama is considering an increase in the average fuel economy standard for passenger cars and light trucks, for the period to 2025.  The standard could be raised to 56.2 miles per gallon, which represents a considerable increase from the standard of 35.5 miles per gallon to be reached by 2016.  Currently only about 13% of the total energy content in gasoline fuel reaches the drive wheels to propel the car forward.  This post summarizes various improvements, some already operational, others at various stages of development, that could be implemented in future auto products to help reach a standard such as that being considered.  Auto makers argue that putting such changes in place would not be economical and/or would not be accepted by consumers.  In balance, we conclude that both economically and from a policy perspective, increased fuel economy in the cars of the future would be beneficial.

Introduction.  Warming of the average temperature of the world, as measured over much of the earth’s surface over the time frame of years, is currently occurring, due to the release of ever-increasing amounts of greenhouse gases into the atmosphere.  This conclusion is broadly accepted among the scientific community based on collective scientific studies by almost 2,000 climate scientists around the world (the United Nations Intergovernmental Panel on Climate Change) , and understood by much of the American public at large (see the previous post on this blog).  Most emissions of greenhouse gases arise from mankind’s burning of fossil fuels for energy.  The increase in greenhouse gas emissions began with the industrial revolution in the nineteenth century.

According to Wikipedia, the U. S. was responsible for almost 20% of the world’s CO2 emissions in 2007, (using data collected by the Carbon Dioxide Information Analysis Center for the United Nations).  Yet, the U. S. has only 4.5% of the world’s population, showing that its energy consumption per capita is very high.  It had the seventh highest energy consumption per capita in the world as of 2005, after Canada and other nations with small population numbers.

The total amount of energy used in the U. S. in 2008 is given by major economic sector in the table below, in units of quadrillion (1015) Btu (British thermal units; the amount of energy needed to heat 1 pound of water by 1ºF, about 1,055 joules).

Pct (%)

Source: Summary, Real Prospects for Energy Efficiency in the United States,; citing U.S. Energy Information Agency Annual Energy Outlook 2008.

The table shows that of the total energy demand in the U. S. in 2008, 28% was devoted to transportation.  This category includes light cars and trucks, which serve individuals and families in their work and leisure lives, as well as heavy duty trucks and air travel.  As of 2003, excluding air travel, about 75% of vehicular transportation energy was consumed by cars and light trucks.

The U. S. Energy Information Agency (EIA) reports that CO2 emissions from the transportation sector in 2008 broke down as shown below:

2008 Million Metric Tons
2008 Percent
Jet Fuel
Diesel and related fuels

Higher Fuel Efficiency Standards for Cars.  The New York Times has reported that the administration of President Obama is likely to propose a large increase in average fuel efficiency for cars and light trucks to be effective by 2025.  The proposal is being contested by the auto industry. 

Currently the U. S. has a regulation in place requiring that the average gas mileage for the cars that a manufacturer produces must reach 35.5 miles per gallon (6.62 L per 100 km) by 2016. 

The new standard for the period leading up to 2025 is likely to be 56.2 miles per gallon (4.18 L per 100km).   According to the newspaper report, the fuel consumption standard in effect in Europe will reach about 60 miles per gallon by 2020, almost 7% higher and 5 years earlier than the new, more stringent standard being discussed in the U. S. American automakers are concerned that reaching this goal will make cars very expensive, so that sales will suffer, and that extensive research will be necessary to devise new technologies that will permit meeting the objective.  They further claim that, in order to meet the new criterion, cars will have to be significantly smaller, a feature they fear will turn American car buyers away.

Sources of energy losses in gasoline-powered cars.  The graphic below shows the losses that occur in operating a gasoline-powered car, using an internal combustion engine.  Of 100% of the energy potentially available in the fuel, only about 13% reaches the drive wheels to propel the car, and another 2% is used to operate accessories in the engine, and air conditioning, for example.  At the web site, clicking on any of the blue arrows explains the losses shown here. 

Attaining the new, higher goal for fuel economy being considered by the U. S. government relies on minimizing these sources of energy loss, converting the lost energy into useful energy propelling the car along its way.

In this post, we restrict consideration of fuel economy to cars with internal combustion engines.

Capturing waste heat.  Clearly, the largest energy loss occurs in the engine, where the heat of burning the fuel is deliberately disposed of in the radiator or other engine cooling mechanism.  Additional heat from burning the fuel, not shown in the diagram above, occurs in the catalytic converter, where the product of incomplete engine combustion, carbon monoxide, is burned with more oxygen to make the final combustion product, carbon dioxide.  Because of the large amounts of lost energy involved, capturing even a portion of the waste heat of combustion could make a significant contribution to improving fuel economy.

One way of using the excess heat might be by developing heat-driven turbines, for example, that could either contribute directly to the drive train, or generate electricity for electric hybrid vehicle operation.  A second way of seeking to capture the heat is developing solid state thermoelectric converters that directly produce electricity using temperature differences between two points.  Research on new materials and processes for thermoelectric conversion potentially usable in cars is discussed here   U. S. Patent 4,753,682 issued June 28, 1988 describes a thermoelectric apparatus for use in generating electric current from the excess engine heat of an internal combustion engine. This modality also could be used in electric hybrid operation.

Rolling resistance.  As they roll along the road, tires deform and then regenerate their cross section; this continuous process dissipates energy within the material of the tire which is lost as heat.  The heat of deformation reduces the efficiency of moving the vehicle.  This is shown as Rolling Resistance in the diagram above.  New synthetic rubber materials known as solution-polymerized styrene-butadiene rubber (S-SBR) have been developed which have improved rolling characteristics with less deformation loss, while retaining traction.  Several Japanese companies and a German company are setting up new plants to make S-SBR tire material in Asia as reported in the May 30, 2011 issue of Chemical and Engineering News, a publication of the American Chemical Society (unfortunately the link requires a subscriber login).

Energy Efficiency Opportunities in Gasoline-Powered Cars.  The U. S. National Academy of Engineering, a component of the National Academies, issued the report “Real Prospects for Energy Efficiency in the United States” in 2010.  A free summary may be obtained here.  Chapter 3 of the report deals with transportation.  It summarizes various technologies available or under development that would enhance the efficiency of operation of internal combustion engines.  In the near term these include variable valve timing, variable valve lift, cylinder deactivation, direct injection turbocharging with engine downsizing, reduction of friction and smart cooling systems.  In the time frame for the new fuel economy standards that are being considered, additional improvements include camless valve actuation, continuously variable valve lift, and homogeneous-charge compression ignition.  The report estimates that implementing such improvements would result in 10-15% improvement in fuel economy in the period to 2020, and an additional 15-20% by 2030.

Diesel engines, which rely on compression for ignition of the fuel, are already 20-25% more fuel-efficient than spark-ignited engines.  Additional improvements are also envisioned for these engines.

In the drive train, improvements in automatic transmission may increase efficiency by perhaps 6-9%.  Further improvements can be obtained by reducing vehicle weight.  The report states that reducing the weight by 10% can lead to a 5-7% increase in fuel economy when the weight reduction is accompanied by reducing the power of the engine accordingly.

Costs of Improving Fuel Economy.  The Energy Efficiency report estimates the additional costs that may be expected from incorporating fuel-economizing improvements such as discussed here.  In considering separately a gasoline-driven car, a diesel-driven car and a hybrid electric car, the additional cost in each category (in 2007 currency) varies between being cheaper by US$400 and being more expensive by US$2,000 in 2035.  This writer estimates that with the fuel economy of 56.2 miles per gallon that might be imposed, compared to the standard of 35.5 miles per gallon to be in effect by 2016, if one drives 15,000 miles per year, such an additional cost would be recovered in the savings from using less fuel in only a few years.

Conclusion.  The Obama administration is likely to propose increasing an average measure of fuel economy for passenger cars and light trucks, possibly to 56.2 miles per gallon, to be attained by 2025.  There are many benefits that would result from such a standard.  The U. S. imports much of the petroleum used to make the gasoline for our cars.  Much of this imported oil originates in parts of the world that are politically unstable and whose agreement with American interests may be questionable.  This makes us vulnerable to fuel disruptions, affecting costs and availability.  The disruption in supply from Libya earlier this year is an example.  It would be useful to be less reliant on foreign sources for oil, which is foreseen as a result of increasing our fuel economy standards.

The research, development and manufacture of cars incorporating new technologies such as mentioned here would be beneficial for America’s continued economic development.  The auto industry is a major component in this country’s manufacturing sector.  It is important to maintain and promote the employment of its workers.

Using less fuel for motor transport is effective to reduce the emission of greenhouse gases, thus lowering the rate of adding greenhouse gases to the atmosphere.  Even if production of all new items and equipment that emit greenhouse gases were to cease, emission of greenhouse gases from equipment already in use would continue for another 20-40 years until that equipment was taken out of service.   The atmosphere is like a bathtub containing greenhouse gases, whose faucet keeps pouring in more but whose drain is essentially plugged so that practically none can escape.  Under these circumstances, our atmospheric CO2 bathtub fills up higher and higher.  The additional greenhouse gases result in an even higher average global temperature, with all its detrimental effects.  Therefore it is to our advantage to minimize the emission of greenhouse gases as much as possible.

The Energy Efficiency report shows that the cost of producing cars with the improvements giving greater fuel economy is absent or moderate.  The concern expressed by auto manufacturers that producing these cars would price them out of the market appears to be countered by this writer’s “back of the envelope” estimate that any increased cost would be recovered in at most a few years as a result of the use of less fuel.

The considerations discussed here show that President Obama’s intended increase in the average fuel economy of gas-powered cars for 2025 is largely attainable and overall would benefit American interests.

© 2011 Henry Auer