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 (ecogreengroup.org). 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 thefreedictionary.com’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.