All posts by Doug McKenzie

I’ll be speaking at the IEEE PV meeting at Xerox PARC at 7pm on Feb 11

I’ll be speaking to the IEEE Santa Clara Valley PhotoVoltaic Joint Society Chapter, at 7pm on Wednesday, February 11 (refreshments and networking are from 6:30 to 7).

Please join me if you can! There’s no charge and no registration is necessary.

Details about the talk.
More information about the IEEE SVPVS.

Here is the abstract for the talk:

Rapidly accelerating adoption of solar energy is urgent. A recent article in Nature suggests fossil-fuel exploration should cease globally and that only one-third of known reserves should be burned to limit catastrophic damage from climate change.

This urgent need is not widely recognized or understood because the situation is new, dramatic, complex, and countered by well-funded lobbying and media interests.

Technically literate people must address this chasm between reality and perception. Only we can grapple with spurious “research” findings and partisan media assertions, and only we can translate technical jargon into understandable content. We also should recognize that in order to cast doubt onto findings that challenge vested interests, scientists and science itself are under attack.

How to bridge this chasm by communicating with less technical people, is the focus of this talk. Technical people are persuasive to those who share the desire for rigor, but we are often much less able to persuade ideological people who lack tools for assessing the validity of quantitative conclusions.

The focus of this talk is on communication. Whether you agree or disagree that climate change poses a threat, or that solar power is the best or only way to deal with it, I believe you’ll find the communication strategies intriguing.

Lots of good things: Meet great people, partake in free refreshments, and collect a copy of a book on climate change in the US I’ll be handing out (free of charge)! I hope to see you there.


PS: If you’re not familiar with the IEEE SVPVS, the speaker series is (almost) always on the 2nd Wednesday of the month, same time, same place. Previous speakers are here.

Comparing Emissions and Efficiency in Electric Cars and Gasoline Cars

Electric cars are not really zero emission vehicles, they just shift the pollution away from where they’re driven to where the power is produced. Most are powered mostly by burning coal which is dirtier and more environmentally destructive than burning gasoline. 

Most gas cars are probably more efficient than electric cars, if you take into consideration all the waste in the process of mining and burning the coal and transmitting the electricity from the power plant to wherever the electric car is charged.

I heard these two claims from a friend last week. He accepts the scientific consensus about climate change caused by human industry, and is a strong environmentalist. Yet both claims are very wrong. Why would he hold these misconceptions? Maybe because while electric cars have been around 100 years, they’ve only recently become mainstream–readily purchasable from a variety of established car companies. Only a few years ago they were complex, cobbled-together “conversions” from gas-engine cars. Today’s electric cars really are new and different, and not yet widely understood. And there are well-funded misinformation campaigns from vested interests ready to amplify every problem, half-truth and lie regarding electric cars, trying to keep alive the fear, uncertainty and doubt. Probably these campaigns have an effect, especially since they’re being used against unfamiliar new technology.

My friend hadn’t found research comparing electric cars and gas-engine car emissions and efficiency. Because grid electricity is produced from different sources in different states, the comparison will vary state by state (as well as country by country). We live in California so I will address these two statements from a California-centric perspective. Details follow this summary of the conclusions derived below.


  • Electric cars in California emit far less CO2 than gas-engine cars, and are far more efficient even considering the entire supply chain, from “well to tank” and from “tank to wheels.”

Debunking Claim 1 (CO2 Emissions)

  • Gas-powered cars emit at least 9 times as much CO2 per mile driven, as electric cars.

Debunking Claim 2 (Overall Efficiency and Waste)

  • Significantly more energy is required for oil and gasoline transport from wells to the end user (gas station), than for fuel transport from wells to electrical generating plants and electricity transmission and distribution to the end user (home or office or other charging station).
  • Significantly more waste from environmental and health issues is associated with the oil and gasoline supply chain from the well to the gas station, than with the fuel and electricity supply chain to the electric car charging station.
  • There is no significant military involvement in protecting the energy supply for electric cars.
  • There is enormous waste (and casualties) for the military protection of the oil supply chain required for our gas cars.
  • There is over 9 times as much cost based on California climate change remediation for gas cars, than for electric cars.


Electric cars are not really zero emission vehicles, they just shift the pollution away from where they’re driven to where the power is produced. Most are powered mostly by burning coal which is dirtier and more environmentally destructive than burning gasoline.

It’s true that electric cars are powered by electricity, and a lot of electricity is generated from burning coal. In the US in 2013, 39% of our electricity was generated from coal. For reference from that page: Natural Gas 27%; Nuclear 19%; Hydropower 7%; Wind 4.13%; Biomass 1.48%; Petroleum 1%; Geothermal 0.41%; Solar 0.23%; Other Gases < 1%.

However in California, coal power provides only about 1% of our electricity. 60% is from natural gas followed by Hydropower 13%; Nuclear 9%; Geothermal 7%; Wind 5%; Biomass 3%; Solar, Coal, and Other Gases are each 1%. Comparisons between electric cars and gas cars in California should not be based on coal. Other factors are relevant:

  • California has a Renewable Portfolio Standard (RPS) which by law requires 33% of our electricity to be generated by renewable sources by 2020; over 20% is renewable now in 2014, with PG&E supplying the most of California’s three large investor-owned utilities, at 23.8% in 2013. Electric cars are more and more running on carbon-free electricity.
  • Some utilities offer customers a renewable-energy option to pay a higher price for clean energy (for example, PG&E).
  • Many electric car owners are aware of and concerned about carbon emissions, and many have installed solar power on their roofs to supply cleaner as well as cheaper electricity.

For simplicity, even though electric car drivers often try to consume relatively cleaner electricity, assume a generous 65% of California’s electricity generation to be carbon emitting, 35% to be carbon free.  Burning one gallon of gasoline generates nearly 20 pounds of CO2. Natural gas is not typically measured in gallons, but it’s easy to normalize by comparing how much CO2 each fuel emits to produce a given amount of energy. British Thermal Units (BTUs) are commonly used to compare energy generation. Burning natural gas emits 117 pounds of carbon dioxide (CO2) per million BTUs and burning gasoline emits 157 pounds per million BTUs. Natural gas emits about 117/157 or about 75% of the CO2 of gasoline.

Emissions Per Unit of Energy Consumed

To compare emissions, gas cars emit 157 pounds of CO2 per million BTUs of energy consumed, electric cars emit 65% of 117 pounds or about 76 pounds of CO2 per million BTUs of energy consumed (because the electric cars are powered 65% by CO2-emitting fuel). Therefore, even considering the emissions from the fossil fuels plants that generate electricity for their batteries, gas cars emit at least twice as much CO2 as electric cars (157 divided by 76).

This effectively debunks the assertion that electric cars are dirtier and more environmentally destructive than gas engine cars. But the truth is even more in favor of electric cars, because gas cars are far less efficient in terms of energy needed per mile driven.

Emissions Per Mile Driven

Gasoline-powered engines are 25 to 30% efficient. “Tank to wheel” efficiency numbers are meant to indicate the overall efficiency (for example including the drive train, not just that of the engine) of a gas-powered car. One careful estimate calculates this overall efficiency at 16%. Of course this will vary by type of car. This particular estimate was for a car that gets 26 MPG.

Electric motors are about 90% efficient. The graph shows the efficiency of the Nissan Leaf’s motor, and that almost all driving is done at or above 90% efficiency.


There’s no transmission in an electric car so no losses from gear changes. There’s no starter motor, and electric cars never “idle” meaning efficiency doesn’t drop in stop-and-go driving. There are losses in converting the electricity from grid-AC to battery DC and back to AC to drive the motor. One careful estimate sets electric car “tank to wheel” efficiency at 73%, using .9 (motor efficiency) times .95 (inverter efficiency) times .9 (battery efficiency) times .95 (charger efficiency).

Therefore, tank to wheel efficiency of electric cars is 4.5 times that of gas-powered cars (73% divided by 16%). However, this neglects “regenerative braking” where stepping off the accelerator pedal recharges the battery (great for city traffic and mountain roads). How much effect this has varies greatly with driving conditions; one study of buses (which stop and start a lot) found efficiency could be improved by between 15% and 30%, meaning tank to wheel efficiency would improve from 73% to between 77% and 81% (that is, adding back 15% to 30% of the 100-73 = 27% wasted). Thus regenerative braking may push electric cars more toward 5 times as efficient “tank to wheels” as gas cars.

Gas-engine cars emit over twice as much CO2 as electric cars per unit of energy, and electric cars are at least 4.5 times as efficient at turning energy into miles driven. So gas-engine cars emit at least 9 times (2 times 4.5) as much CO2 per mile driven as electric cars.

Summary: Gas-powered cars emit at least 9 times as much CO2 per mile driven, as electric cars.

Most gas cars are probably more efficient than electric cars, if you take into consideration all the waste in the process of mining and burning the coal and transmitting the electricity from the power plant to wherever the electric car is charged.

This claim is also incorrect. But first, what exactly does it mean? One should count all the energy measured in BTUs associated with all the steps in the processes–exploration, drilling, production, transportation to refineries, refining, delivery to the end location (as well as each car’s efficiency at energy consumed per mile, calculated above)–and see if they add up to less for a gas-engine car than for an electric car. Then to this amount, add the energy measured in cost and waste as well as BTUs, required to remediate all the associated health and environmental damage, to provide necessary military protection to energy industries, and to remediate climate change in California. It’s beyond the goals of this article to fully quantify all these elements, but clear, strong conclusions can be drawn.

Exploration, Drilling, Refining and Distribution of Oil and Gasoline Versus Natural Gas

Natural gas must be discovered, drilled, refined and distributed hundreds or thousands of miles first to refineries then to electrical generating stations. California receives most of its natural gas by pipeline from production in the Rocky Mountains, the Southwest, and western Canada. It is efficiently transported from these sources to power plants through pipelines. Where end use is not electricity generation–therefore not applicable here–natural gas is transported less efficiently, by rail and truck. From the power plant, the electricity must be transmitted and distributed to where the electric cars are charged. Transmission and distribution losses are about 6%.

Oil must be discovered, drilled, refined and distributed hundreds or thousands or tens of thousands of miles first to refineries then to gas stations where cars fill up. Half of California’s oil is drilled in California (including off-shore wells), half is imported “mostly from the Middle East, South America and Africa, according to the California Energy Commission.” Unlike electricity transmission and distribution, the cost of distributing gasoline varies greatly because of differing sources, the methods and length of the distribution channel, the end location of the gas station, the type of gasoline and other factors.

Exploration and drilling are broadly similar for oil and natural gas. Both are often found together. Processing natural gas is somewhat simpler than refining oil. Pipelines are the most efficient means of transporting oil and natural gas, followed by tankers which are used to bring oil to California from the around the world. Also, transporting gasoline from refineries to gas stations is mostly by rail and truck, which are significantly less efficient than pipelines or tankers and far less efficient than transmitting electricity by wire.

Finally, in California, at least 35% of electric car “fuel” is from renewables. How this relates to efficiency may seem somewhat ambiguous; for example solar panels are rarely more than 20% efficient in terms of the amount of sunlight they convert to electricity. However because the fuel for renewables is virtually limitless and free, there is effectively no cost for the “wasted” fuel. On the other hand, there is significant cost and waste in all steps related to supplying fossil fuels, whether directly for gas cars or indirectly for electric cars.

Additional benefits to electric cars are that the driver needn’t drive anywhere to “fill up,” and electric charging stations needn’t be periodically removed and replaced as the underground tanks at gas stations do.

Summary:  Significantly more energy is required for oil and gasoline transport from wells to the end user (gas station), than for fuel transport from wells to electrical generating plants and electricity transmission and distribution to the end user (home or office or other charging station).

Health and Environmental Considerations

It would be tremendously complex and being controversial, subject to loud argument, to quantify all the health and environmental issues related to the natural gas and oil and gasoline industries. A brief summary of the issues is followed by a cautious conclusion.

Health and environmental issues associated with natural gas include (from here and here):

  • Groundwater contamination
  • Disposal of wastewater
  • Control of air pollutants
  • Climate change considerations including CO2 from combustion and methane from leakage
  • Radioactivity
  • Earthquakes

Health and environmental issues associated with oil and gas include:

  • Toxicity of the oil
  • Air, water and land pollution
  • Climate change – CO2 primarily from combustion
  • Release of volatile organic compounds
  • Spills
  • Waste oil

Almost all natural gas in the US is now produced by fracking. Almost all new oil production in the US comes from fracking (because of fracking, the US will soon pass Saudi Arabia as the world’s largest oil producer). While some issues of natural gas production (notably methane leakage) do not apply anywhere near as much to oil production, there are also dangers of oil production that do not apply to natural gas (notably oil spills). Issues (fracking and other) are perhaps roughly equivalent between the natural gas and oil industries.

In addition to normal business risks, there are demonstrable risks of disasters from the natural gas supply chain such as when 8 people were killed in a natural gas pipeline explosion in 2010. Note that this involved a pipeline transporting natural gas to be burned for space heating, hot water heating, etc. and was unrelated to electricity generation.

There are far more risks of disasters from the oil and gas supply chain (for example here and here). There do not appear to be any reports of disasters or serious problems related to installation or use of electric car charging stations.

Considering the day-to-day health and environmental costs and risks of the natural gas and oil/gasoline supply chains as roughly equivalent, and that the risks of catastrophe are significantly greater in the oil industry, a conservative conclusion is:

Summary: Significantly more waste from environmental and health issues is associated with the oil and gasoline supply chain from the well to the gas station, than with the fuel and electricity supply chain to the electric car charging station.

Military Protection

Because all California’s natural gas comes from within the US or from Canada, and because the price of natural gas, unlike oil, is not priced similarly around the world, no significant military protection is needed. The primary reason natural price varies so widely is because it costs so much to compress it into a liquid for export and then uncompress it back for distribution. Prices are several times as much in some areas of the world as in others. Currently, natural gas in the US is $3.84 per million BTUs, about $9.24 in Europe (over double the US), and $17.17 in Japan (over four times the US). Electrical transmission and distribution lines, though somewhat unprotected from attack, also do not have and do not yet appear to need significant military protection.

Summary: There is no significant military involvement in protecting the energy supply for electric cars.

On the other hand, there is an enormous expense associated with the military effort to protect vulnerable elements of the oil industry. Because California imports half its oil from the Middle East, South America and Africa, some of the military expense should be factored in.

The United States pays billions of dollars annually to our friend-enemies for their oil. We imported about 1.3 billion barrels from OPEC countries in 2013, so at the current price of $85 per barrel (the lowest it’s been in two years), that’s over $100 billion per year. Our ally Saudi Arabia is not Canada; they beheaded 79 people in 2012-13, for “crimes” including adultery, sorcery, blasphemy. But we have to pay for oil anywhere we get it, so these dollars, though they may not be put to good use, don’t add to the overall expense or “inefficiency.”

Much more relevant to the efficiency question, we also spend many billions to protect our oil interests from sabotage and piracy, for example with the military might of our Fifth fleet. A good estimate puts this protection cost at $500 billion per year. We are continuously at war over oil (we are very unlikely to go to war over natural gas because we have so much domestic supply). The US military itself consumes billions of gallons of fuel per year, but much more significantly, thousands of Americans died in the oil-related wars in Iraq and Afghanistan, tens of thousands came home with major injuries, and hundreds of thousands have long-lasting mental injuries (PTSD or traumatic brain injuries). These enormous sacrifices are some of the “inefficiencies” in the supply chain that takes oil from the wells to the refineries.

What is California’s share? The good news is California ranks 49 of 50 states in per-capita energy consumption. This is partly because of our good climate, partly because of vigorous energy efficiency policies. However, we are a large and populous state and we consumed 1,700 trillion BTUs of gasoline in 2012. World consumption of gasoline is about 20 million barrels per day ( World consumption of oil is about 90 million barrels per day so gasoline is about 22% of the total.

To normalize the units, one gallon of gasoline contains 114,000 BTUs. So 1,700 trillion BTUs in a year divided by 114,000 means California consumes about 15 billion gallons per year. Divide 15 billion by 365 to get 41 million gallons per day. Divide 41 million by 42 (gallons in a barrel) and the result is California consumes about 1 million barrels per day, about 1/20th of world gasoline consumption.

Though we import “only” half our oil, we owe our share of protection money to keep the world’s oil safe to prevent price spikes. Unlike natural gas with enormously expensive export and import facilities necessary for global shipment, oil can be relatively more easily loaded onto tankers for shipment. With significant supply and demand changes or impactful news, the price of oil spikes and drops around the world relatively evenly.

With gasoline at 22% of all oil products, California’s share is about 1/20th of 22% of $500 billion, or about $5.5 billion per year to protect our oil. California consumes 15 billion gallons of gasoline per year, so $5.5 billion divided by 15 billion means California owes about 36¢ per gallon to protect our oil supply.

Gasoline in California currently costs about $3.67 per gallon. Included in that is 18.4¢ per gallon in Federal tax, but that barely covers construction and maintenance of highways and bridges. So the 36¢ per gallon for protection is not included in the $3.67 we pay at the gas station. In economics terms, it is an external cost or “externality,” a subsidy hidden from the price at the gas station pump.

The $500 billion per year for military protection of oil is just one estimate. And charging California’s $5.5 billion per year as its rightful “share” of oil-protection money would be menacingly unpopular. Still, it is straightforward to conclude:

Summary: There is enormous waste (and casualties) for the military protection of the oil supply chain required for our gas cars.

Climate Change Remediation

Another large cost, for both electric cars powered partly by natural gas and for gas-engine cars, is the cost of managing climate change caused by emissions of CO2. California passed into law and is implementing a mechanism to price CO2 emissions – the California Air Resources Board Cap-and-Trade Program. The goal of the program is to bring California greenhouse gas emissions to 1990 levels by 2020. To accomplish that, over time as decreasing amounts of CO2 emissions are legally allowed, emitters must pay either for less polluting equipment or for their CO2 emissions on a dollars per ton basis. The current price is about $12 per ton of CO2 and is expected to rise to about $15 per ton by 2020.

At 15 billion gallons of gasoline consumed per year, and 20 lbs of CO2 emitted per gallon of gasoline burned, the cost of $12 per ton can be extrapolated to $15 billion times 20 lbs divided by 2000 (lbs per ton) times $12 or about $1.8 billion per year.  Dividing $1.8 billion by 15 billion gives approximately 12¢ per gallon as the hidden subsidy for CO2 emissions in California.

The cost of the Cap-And-Trade program is a hidden subsidy now but not for long. Transportation fuels have been exempt but the exemption ends on Dec. 31, 2014. We will soon see the roughly 12¢ per gallon hidden subsidy becoming visible in the price of gasoline at the pump in California.

CO2 emissions from burning natural gas have also been exempt, and that exemption also ends on Dec 31, 2014. Because gas cars emit about 9 times as much CO2 per mile driven as electric cars, the hidden CO2 subsidy is also about 9 times as much for gas cars.

Summary: There is over 9 times as much cost based on California climate change remediation for gas cars, than for electric cars.


In conclusion, electric cars in California emit far less CO2 than gas-engine cars, and are far more efficient, even considering the entire supply chain from “well to tank” and from “tank to wheels.”

Beyond the emissions and efficiency comparisons, there are a few other important comparisons. Electric cars are also much cheaper to drive, and with the single exception of “range anxiety” (that you’ll be left stranded when your batteries run out), are much more fun to drive than gas-engine cars (see a presentation on “The Joys of Driving an Electric Car“). Range anxiety is caused by the scarcity of charging stations, and the amount of time required to charge batteries. Both of these problems are being solved, with Tesla leading the way by building hundreds of charging stations across the state, country and world, and implementing a battery-swap so that a “refill” takes less time than to fill up a tank of gas.

Electric cars are inherently far simpler than gas-engine cars, and so will eventually become much cheaper as battery technology improves (and especially if the price of oil rebounds). Again, Tesla is leading, building a huge battery factory that is expected to reduce the price of batteries by 30% by 2017.

Finally, if climate change turns out to be anywhere near as formidable as reported and predicted by the International Panel on Climate Change (IPCC), burning gasoline, natural gas and other CO2-emitting fuels must diminish, soon and forever.

I taught Palo Alto’s Solar Power 101 Workshop 5/17/2014

I teach this 2.5 hour solar basics workshop periodically for the city, to introduce solar mostly to homeowners considering rooftop solar, though the workshop is open and free to everyone. Palo Alto runs its own utilities, so some elements of the workshop such as the net metering rules are Palo-Alto specific, but most of material is relevant to everyone in PG&E and other territories.

The PDF slideset is here. The slides will show up on the Palo Alto site soon, and I’ll add that link here then. Many thanks to Palo Alto Utilities Lindsay Joye for sponsoring the workshop and for her great knowledge on all things Palo Alto. For example, she let us know the excellent news that following the completion of the Palo Alto Green program, which allowed residents to pay ~10% more for 100% carbon-neutral electricity (ended because now ALL PA’s electricity is green) a similar program for natural gas will be begun.

I want to deliver similar workshops to other municipalities to help encourage their residents to consider solar.  Please Contact me if you’d like me to speak in your area.

Stanford Guest Lecture on Solar Myths and Truths

I gave a guest lecture to Stanford University’s Solar Energy Conversion (EE 237) class which covers “Basics of solar energy conversion in photovoltaic devices.”  Whether a student wants to create a solar technology startup, work as an employee in an established solar organization, or do something completely unrelated to solar while maintaining an interest in local, state and federal policy related to solar, an ability to combat the well financed, partisan anti-solar misinformation campaigns is crucial to our environmental, health and economic progress.

In my talk I tried to describe and debunk some prominent myths regarding solar, and to discuss a few psychologically-oriented approaches to refuting myths.

Abstract for the talk:

There is great variance in the knowledge and opinions held on the state and prospects of solar power in the US. Recent headlines range from “Solar energy could supply one-third of power in U.S. West” to “If California were to rely on solar power for its electricity consumption, the entire state would have to be covered with photovoltaic cells,” and from: “The world must shift to solar and wind power rapidly to avoid catastrophic global warming” to: “Renewables ‘Sound Good’ but Should Take Backseat to Coal.”

Doug will work quantitatively through selected solar claims, and will suggest tactical approaches technical people should consider in order to be effective during discussions with non-technical people.

Slides (PDF) for the talk are here. If you have questions or comments or would like me to speak at your venue, Contact Me or Ask a Question.

My sincere thanks to EE 237’s Professor Aneesh Nainani for inviting me to speak.

The Joys of Driving an Electric Car

I presented “The Joys of Driving an Electric Car” today to the EcoGreen Group of Silicon Valley ( The slideset (PDF) is here.

Introduction to the talk:

There are obvious environmental benefits of electric cars, such as reducing reliance on imported oil. There are also many not-so-obvious benefits to owning and driving an EV. This talk will compare environmental, economic and experiential benefits of owning and driving an electric car versus a gasoline-powered car.

Electric Vehicles are related to solar in two fundamental ways:

  • Solar enables 100% clean-powered transportation
  • Energy storage (eventually) will enable solar to be our dominant energy source, and EV batteries will (eventually) be a major source of storage.

Vaclav Smil on Renewables in Scientific American – a Rebuttal

Vaclav Smil recently hit the big time as “the Man Bill Gates Thinks You Absolutely Should Be Reading” (Wired Magazine 11.25.13). As Distinguished Professor Emeritus at the University of Manitoba and recipient of many awards, the plug from Gates was only his latest acclaim.

The Jan 2014 issue of Scientific American carries Smil’s article “The Long Slow Rise of Solar and Wind: Why, contrary to popular belief, we are not likely to wean ourselves from fossil fuels quickly” (subscription required). [Update: Smil’s article is available (PDF, no charge) on his website here.] The thrust of the article is contained in its last lines: “The shift from fossil fuels to renewable energy sources … will require generations of perseverance.”

I find the article infuriating, with its proofs by assertion, guilt by association, slippery logic, and the sprinkling of escape clauses that could be intended as vaccinations against future criticism. Maybe there’s a good payoff in personal branding to play contrarian against the momentum of renewables, but there is already so much misinformation flowing from so many suspect sources, that “experts” should avoid adding to it. Much more damage is done when a reputable author publishes “soft scorn” in a reputable magazine, than when blatantly partisan screed appears in blatantly partisan media.

Smil begins with an attempt to discredit Amory Lovins by citing his almost 40-year-old prediction on the speed at which renewable energy would spread, which turned out to be far too optimistic. There is no mention of any broader context, such as federal policy decisions that effectively delayed renewables for decades. A reader unfamiliar with Lovins might infer he is not a good source, and might therefore miss his 2011 book Reinventing Fire, which is probably the best researched (and sourced) plan available for shifting the US from a fossil-based to a renewables-based economy—and with a net gain to the economy! Or his August 2013 article “Separating Fact from Fiction In Accounts of Germany’s Renewables Revolution which is probably the best debunking of the oft-echoed anti-solar myths that Germany’s electrical grid is being sabotaged by the high percentage of renewables, that Germany is turning back to coal, etc.

Smil continues by claiming that the slow pace of renewables “is not surprising. In fact it is expected” because shifts from one source of power to another always take 50 or more years. He provides charts showing the growth of coal, oil, natural gas, and “modern renewables” (wind, solar, geothermal, liquid biofuels) as a percent of global energy supply plotted over the decades since 1840. However, elsewhere in the article he admits: “A mere three sequences do not dictate the tempo of future global energy transitions. And [breakthroughs in nuclear power or energy storage] could hasten another change.”

Exactly. Given the tremendous scale of change wrought by technology and politics and population in the 170 years since coal hit Smil’s entry-level mark of 5% of world energy supply, why is his timeline to fuel dominance anything but coincidence? He spends plenty of space describing why each timeline is accurate, but no space arguing why they are or should be or must be similar. The world is littered with the debris of claims of causation found to be mere correlation (see any superstition, or the ultimate global average temperature versus the number of pirates). Even taking on faith that Smil’s timeline could be predictive, it should halt at fossil fuels. Nuclear power is a glaring counter-example of a major power source that did not follow Smil’s timeline and therefore invalidates it for non-fossil fuels. Nuclear is far from dominant more than 50 years since the days of “Our Friend the Atom” and has by now achieved, at best, a very dubious future.

On the other hand, the accelerating adoption of renewables has clear, major causal drivers. One is the imperative to shrink carbon emissions to better manage the consequences of a warming planet. Another is the cost of solar, which tracks an exponential curve downward (not unlike Moore’s law for integrated circuits), versus fossil fuel extraction and production costs which will continue to climb relentlessly, if not monotonically higher. The adoption of distributed solar where there is no reliable grid is another driver, and it appears to be taking the same non-linear leap in many areas of the developing world, as the leap from no phones directly to cell phones did (skipping land lines). Yet another driver causing accelerated adoption of renewables is security. FBI Director James Comey recently said “Cyber attacks and organized cyber criminal activities will emerge as the greatest threat to national security over the next decade.” “Behind the meter” distributed solar combined with battery storage will become an ever more affordable and appealing alternative to power-grid vulnerabilities.

This is not our great-great-great grandfather’s energy industry. Smil would seem to characterize the context and environment and challenges related to the adoption of renewables today as about the same as those of coal 150 years ago—or at least close enough for him to claim he can predict the timeline of renewables adoption because it matches that of coal. But most of today’s industries didn’t even exist back then, and those that did bear faint resemblance to their descendants today. The Edison Electric Institute, an association of investor owned utilities, weighs in, in a January 2013 report: “Recent technological and economic changes are expected to challenge and transform the electric utility industry” (pdf). Little is the same, much is different, and the path to renewables dominance is not constrained by the history of coal.

One can never be sure of an author’s intent when writing a polemic. Is he misinformed? Is he a shill for some vested interest? Does he believe that becoming a fly in the ointment will improve his following? Some clues:

  • “After more than 20 years of highly subsidized development, new renewables … have claimed only 3.35% of the country’s energy supply.” One might suppose this means, even with help of big subsidies, renewables have grown far less than 1% per year (about 3% in 20 years). This is classic How To Lie With Statistics and is misleading in at least two important ways. First, renewables subsidies in the US have been very choppy over the last 20 years, repeatedly degrading long-term confidence with boom/bust cycles. The most recent “solar coaster” was in 2008 when it was entirely unclear until it occurred, whether the Bush administration would extend the 30% Federal Tax Credit. It was extended, to 2016, meaning the solar industry now entering 2014 is again facing another near-term policy question – how to make business plans for 2017 and beyond. Meanwhile subsidies for fossil fuels (which renewables must of course compete against) have remained consistent and huge ($544 billion worldwide in 2012, slightly up from 2011) for many decades. Second, a more revealing statistic about renewables (solar in particular) is that while it took over 50 years from the sale of the first commercially available solar cells, to reach the first 100 gigawatts (GW) of global installed capacity in late 2012, it will take only 3 years to install the next 100 GW as we continue on the path of doubling installed capacity every 2 to 3 years. Smil’s statistic hints at sub 1% growth per year; real growth of solar has been running at 33% per year.
  • “Of course it is always possible that a disruptive technology or a revolutionary policy could speed up change.” This hedge allows Smil to say “I told you so” regardless of whether his main thesis holds or falls apart, and it makes him look to me more like a noisemaker than an independent (much less disruptive) thinker. In fact the disruptive technology is already here: the price of solar panels dropped 70% since 2000 (this and related stats are here, part of Zach Shahan’s great CleanTechnica site). As a result, solar has moved from niche to mainstream: “FERC: Almost All New US Electricity Generation Coming from Solar.” On the policy front, solar in the US is more cumbersome to install than in most of the rest of the developed world. Our permitting, installation and sales costs are almost double those of Germany. Imagine the dazzlingly fast adoption of renewables if we added revolutionary policy changes to the existing disruptive technology! The biggest hurdle to revolutionary policy in the US is education; Smil, echoing and adding deceptions, makes that hurdle a little higher.
  • “Another factor is the intermittent nature of wind and solar.” Ah yes, the sun doesn’t shine at night. This talking point easily finds its way over the low bar at Fox News. Better insights include that solar delivers energy at close to when it’s needed most (peak demand is in the afternoon), and the most expensive electricity for utilities to provide is the “spinning” resource to meet the spikes during peak demand.
  • “If electric utilities had an inexpensive way to store massive amounts of excess power … then the new renewables would expand much more quickly. Unfortunately, decades of development have provided only one good, large scale solution [pumped hydro].” This is the third time Smil has resorted to his escape-clause hedge that breakthroughs of this or that or whatever kind will invalidate his thesis. A glance at 170 years of technological innovation should give pause to everyone who asserts what cannot be done. Meanwhile, utilities are beginning to mandate significant amounts of storage, and battery innovations, as the subject of wide and intense research for the burgeoning electric vehicle market as well as for energy storage at every level from the home to the grid, are inevitable (who knows exactly what and when… maybe Don Sadoway’s liquid metal battery).
  • “In Germany, all this variability can cause serious disruptions in electricity flow for some neighboring countries.” Not so much, as Smil would know if he’d kept up with Amory Lovins’ work (see above) instead of disparaging him.
  • “Governments should not offer large subsidies or loan guarantees … exemplified by Solyndra …” Solyndra! Two years after Solyndra went under, some form of “solar equals Solyndra” or “the death of Solyndra means the death of solar” seems to be a go-to rant for every anti-solar partisan. When Smil proclaims Solyndra reveals the dangers of the government picking winners, he joins the crowd of anti-solar, anti-government partisans who can’t seem to understand that the DOE loan guarantee program performed better than silicon valley venture capital firms at picking winners.
  • “… prices of all forms of energy should reflect as much as possible, the real costs, which include both the immediate and the long-term environmental and health impacts of creating that energy.” This is absolutely valid, and in fact is the reason we must shift off fossil fuels as fast as economically practicable. But instead of pursuing the straightforward carbon-impact logic, Smil shifts to sophistry, saying, “The impacts range from greenhouse gases and black carbon from burning fossil fuels … to the cost of a high-voltage supergrid to link far-flung wind and solar farms.” That is, he is implicitly equating the impact of burning gigatons of carbon with the “impact” of upgrading the US grid infrastructure. Infuriating.

I will give Smil credit for promoting energy efficiency as the most important way to speed the path to renewables. Though his article is fraught with deceptions and half-truths, it will truly be very difficult to ramp up renewables as fast as we need to, and fast-payback efforts to reduce energy demand will be key. It’s too bad Smil didn’t point to Lovins’ great Reinventing Fire which so clearly and carefully shows us how to do exactly that.


Solar Basics – kW and kWh

In a previous post, I reported that French journalist and economist Guy Sorman proclaimed, “If California were to rely on solar power for its electricity consumption, the entire state would have to be covered with photovoltaic cells.” In reply, I proclaimed that Mr Sorman is wrong by 50,000%.

How would you go about deciding who is correct? In teaching and observing solar classes and talking to a variety of people outside the solar industry, I’ve found that many or even most people can’t with confidence confirm or deny this type of claim.

So let’s go through it. It’s a bit laborious, but the good news is it’s not technically difficult. Even better news is that the few key concepts needed to dig into the claim are probably also the most important needed to start thinking through solar on your own rooftop.

Kilowatts (kW) and kilowatt-hours (kWh) – these are very clearly defined units, but also very frequently confused. kW is a unit of power, kWh is a unit of energy. Power and energy are unambiguously different from physics and engineering perspectives, but are often used interchangeably in common English as well as by some reporters who should know better. Unfortunately, many web pages define watt in potentially confusing ways such as in terms of other more fundamental units of physics.  This doesn’t help. Also, one of’s 16 definitions of power is “Electrical or mechanical energy.” This really doesn’t help.

A good definition of power is: the rate at which work can be done. A good example is a 100 watt incandescent light bulb. If it’s on, the work it’s doing shows up as light and heat. It’s designed to run at 100 watts and no more, and and so its name is based on the peak capacity of the bulb to put out light and (a lot of) heat. Solar panels are also named by the maximum amount of watts they can put out. A solar panel is kind of the opposite of a light bulb: Put light into a solar panel and out comes electricity (and some heat).

Like light bulbs, solar panels come in different wattages. A common power rating for a high end solar panel is 345 watts. The size of this panel is about 61″ by 41″ or about 17.3 square feet. So, this panel, at its maximum, puts out 345 watts from sunlight falling on its 17.3 ft² area. Another way to say this is, at its maximum, a 345 watt solar panel puts out a maximum of about 20 watts per square foot (345 divided by 17.3 equals about 20).

Back to the light bulb. If a 100 watt light bulb is left on for one hour, it will consume 100 watt-hours of energy. Left on for 10 hours, it will consume 1000 watt-hours, which is the same as 1 kilowatt-hour, or 1 kWh. Similarly (and under ideal conditions), if a 345 watt solar panel is left in the brightest sun for 1 hour, it will generate 345 watt-hours of energy. Under those same ideal conditions, after three hours, it will generate a little over 1 kWh.

One might wonder if “watt-hours” might mean watts minus hours (since it looks like that) or watts per hour, or some other variant. But watt-hours means watts multiplied by the hours the watts are doing work.  The definition of energy is very clear to physicists, but there are probably even more English language definitions for energy than power. A good definition of energy is: power consumed (or generated) over time.

The size of a solar system is specified in watts, or kilowatts (kW) or megawatts (MW). For example, a commonly seen residential rooftop solar system might be 4kW, a large solar power plant in the California desert can be well over 100 MW. The output of a solar system is given in kilowatt-hours (kWh) or megawatt-hours (MWh) or gigawatt-hours (GWh). Only the W is “supposed” to be capitalized but few people care and all variations are used interchangeably. Your electricity bill is priced in cents per kWh. There are many pricing complexities; in California you’ll probably be paying somewhere between a little under 10¢/kWh to (rarely) over 50¢/kWh.

The big question, whether you’re considering solar for your roof, for all of California, or for anything in between, is how much energy will your system generate? How many kWh’s will your kW’s generate? There are very many factors that go into making the calculations, including some, like the weather, that are not precisely predictable. A lot of effort goes into the design, construction and monitoring of solar systems, to make sure that the kWh’s that are supposed to be generated, actually are. But the good news it’s easy to arrive at ballpark numbers. Estimates made by competent people off by over 10% are very unusual. (I am claiming that Mr Sorman is off by 50,000%.)

So… how do you estimate kWh’s from kW’s? Here is just one way to do it:

  • Step 1 is to start with the maximum power your system can generate, and then “de-rate” it for each less than ideal factor. For example, dust may build up on the panels, blocking some of the light. Also, the “direct current” (DC) that the panels produce must be “inverted” into “alternating current” (AC) that homes and the power grid use, and there is some loss in the process. There are other factors that every solar installer understands, and there are standard tools to do the calculations. The result is that the maximum AC power that a rooftop solar system will generate is typically between 75% and 80% of the maximum DC (“nameplate”) power that’s stamped on the panels by the manufacturer. For example, if you purchased a 4.14 kW system (that would be 4.14 kW DC, comprised of 12 345-watt DC panels), it would generate at its maximum between about  3.1 kW and 3. 3 kW AC. Let’s go with  3.1 kW AC.
  • Step 2 is to calculate how much energy the system will generate on an average 24-hour day. At noontime on the brightest summer day, the system will put out 3.1 kW. Over the noontime hour on that bright day, it will generate  3.1 kWh.  An average day means taking the average of a full year’s worth of 365 days to account for seasonal changes. This would be a hard calculation involving morning fog, nighttime, rain, the sun’s varying angle, but the National Renewable Energy Laboratory (NREL) has made it easy for everyone, by giving us the “peak sun hours” for a large number of locations across the country. Peak sun hours describes, given your system’s maximum power (3.1 kW AC), how much energy that system will generate on the average day.  The San Francisco Bay Area’s number is about 5.5, meaning for a 3.1 kW AC system, 3.1 times 5.5 or about 17 kWh will be generated during the average day. Because the 5.5 is based on the full year’s worth of 24-hour days, the yearly output of the 3.1 kW AC system is simply 365 times 17 kWh or 6205 kWh.

Now we can figure out how much energy (kWh) will be generated per square foot of solar panel. The 3.1 kW AC system is a 4.14 kW DC system made up of 12 345-watt panels, where each panel is about 17.3 ft². So 12 panels would be about 207 ft² and if that 207 square feet of panels generates 6205 kWh per year, then one square foot of solar panel generates about 30 kWh per year (6205 divided by 207 = 30).

Just two more things and we’ll be able to assess Mr Sorman’s claim: how big is California, and how much electricity does California consume in a year.

  • Enter “size of California” into Google: California is 163,696 square miles. That was easy.
  • Electricity consumption is a little more involved. It’s under the California Energy Consumption Data Management System here. Choose “ALL” under County, select “Total” in Sector, select the most recent year (2011), click on Create Report. “Total” reports all types of solar per county, but does not give the sum of all the counties which is the total for California. So copy the entire report (column titles plus 58 counties) and paste it into a spreadsheet. Then add up the county totals with a formula such as “sum(c2:c59)” and the result is 272645.3171. The report says all numbers are in expressed in millions of kWh, so we now know California consumed 272,645 million kWh of electricity in all of 2011. Other ways of expressing 272,645 million kWh include: 272,645 thousand MWh; 272,645,000 MWh; 272,645 GWh. We can get a sanity check in the California Energy Commission’s Energy Almanac here where it says California generates about 200,000 GWh per year and that’s about 70% of how much California uses. 200,000 GWh divided by .7 = about 285,000 GWh which is a good match to our 272,645 GWh.

How many square miles of solar panels would be needed to generate 272,645 million kWh per year? The arithmetic is simple, but it’s with giant numbers so care is needed. Our one square foot of panels generates 30 kWh per year. There are 5280 times 5280 or about 28 million square feet in one square mile. So one square mile of panels will generate about 840,000,000 kWh per year (28 million times 30 kWh) which is the same as saying one square mile of panels will generate about 840 million kWh per year. Now we can just divide total consumption by generation per square mile to find how many square miles we need to satisfy California’s consumption. 272,645 million kWh divided by 840 million kWh = 324. So 324 square miles of solar panels will generate enough electricity during the year to satisfy California’s total electricity consumption for the year.

Last step! California has 163,696 square miles, so the piece of California, filled with solar panels, needed to generate what California consumes is 324 divided by 163,696 or .0019. This is 19/10,000ths, or about 2/1000ths or about 1/500th or 1/5th of one percent. One fifth of one percent of California, filled with solar panels, would generate enough electricity in one year to satisfy California’s total electricity consumption for one year. Mr Sorman is wrong by a factor of 500, which is the same as being 50,000% wrong.

While there is nothing inaccurate above, I have left things out in the interests of clarity. For example, panels are never packed so tightly together (maintenance access is needed, etc),  some of California is forests or lakes or steep mountains or streets and highways and so on. Mr Sorman doesn’t mention these things either, and considering the magnitude of his error, they amount to nothing. A great source to learn more about this (and many other things) is Physics for Future Presidents by Physics Professor Richard Muller. Prof. Muller has several other books with similar titles (shown on the link above), and they are all excellent.

If you don’t understand something, Contact Me, or Ask a Question, or leave a comment.

Solar Truths and Myths and Questions

“I don’t think we live in times that are particularly kind to objective information.” Bob Howarth, Professor of Ecology and Environmental Biology at Cornell, said that in 2013 in the movie Gasland II.

Steven Chu, in a 2010 interview in the San Jose Mercury News, said, “Americans were believing [in global warming] because of sound bites, and now they’re disbelieving because of sound bites.”

Fox News solar reporter Shivani Joshi said in Feb. 2013, as the news ticker on the lower third of the screen predicted the imminent death of the solar industry,  that the reason “solar is working out great for [Germany]” is “because they’ve got lots of sun, right? They’ve got a lot more sun than we do.” (Germany receives less sun than anywhere in the US other than western Washington and Alaska, and barely half the sun received in the western half of the US.)

French philosopher and economist Guy Sorman wrote in 2011, “If California were to rely on solar power for its electricity consumption, the entire state would have to be covered with photovoltaic cells.” (In truth, Mr. Sorman was wrong by 50,000%!)

Though everyone has heard a lot about solar, it’s a complicated topic and hard for most people to separate out truth from fiction, news from noise, valid statistics from bogus claims. Vested interests are threatened and their voices are ubiquitous and amplified in our extraordinarily partisan, dollar-driven times.

I will post truths, news, and statistics here about solar and other energy-related topics. If you’d like to know something about solar, or are just wondering how you might participate in “the solar revolution,” Ask a Question or Contact Me.