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STC vs. PTC: Why Solar Panel Testing Matters

Energy Miser

Mark Durrenberger’s Blog — writing about homes and energy.

STC vs. PTC: Why Solar Panel Testing Matters

December 1, 2015

Solar Installation in New EnglandYou’re the proud owner of a new 7,800-watt solar energy system. But every time you check your online monitoring, your system is operating below the full 7,800 watts of capacity.

Then you notice the rating plate on your inverter in the basement says 7,600 watts. What the heck?

I can explain the perfectly legitimate reasons for the discrepancy, but first, I have to go off on a tangent and discuss solar panel testing.


Standard Test Conditions (STC)

A solar panel is first tested right in the factory. As the panel comes off the production line, a worker (or robot) places the panel on a “flash table” and hooks up the positive and negative leads to a measuring device. The panel is then “flashed” with fake sunlight.  The connected electronics record a number of performance values including the panel’s voltage (volts), current (amps) and power (watts).

STCThese testing conditions are called “Standard Test Conditions” or STC. But what’s standard about them? Well, the light source is calibrated to a defined set of wavelengths and so that precisely 1,000 watts per square meter fall on the front glass of the solar panel. Temperature is the other key test condition – everything is at 77°F (25°C). The solar cells, glass, aluminum frame, and back-sheet are all at 77°F.

If you haven’t noticed already, these test conditions are nothing like the real world. So why does the manufacturer even bother?

As it turns out, there is quite a bit of natural variation – upwards of 5-6% – in the power output from solar cells and panels, even from panels made in the same production run. The manufacturer uses STC testing to sort panels by power and ensure that similar panels are sold and used together.

For example, let’s say that after a flash test, a panel measures out at 257 watts. The manufacturer will “bin” that panel in the “255 to 259.9 watt” bin. A 263.4 watt panel will end up in the “260 to 264.9 watt” bin and so on. The manufacturer will then sell the 255-259.9 watt panels as 255-watt panels, and the 260 to 264.9-watt panels as 260-watt panels. (By the way, even though the panels come off the same production line and cost exactly the same to manufacture, manufacturers charge more for the higher wattage panels.)

Unfortunately, this testing gives only a rough indication of how solar panels will perform in the real world. That’s where the next test comes in.


PVUSA Test Conditions (PTC)

In the mid-1990s, under the direction of the National Renewable Energy Laboratory (NREL), a set of test conditions were developed to measure solar panel performance under “real world” conditions. The conditions were called “Photovoltaics for Utility Scale Applications Test Conditions” or PVUSA Test Conditions; more commonly “PTC.”

Source: STC vs. PTC: Why Solar Panel Testing Matters

After Hurricane Sandy, a Park in Lower Manhattan at the Center of a Fight – The New York Times

Listen to This Article  Listen 44:42

To hear more audio stories from publications like The New York Times, download Audm for iPhone or Android.

“The day after the storm swallowed her neighborhood, Nancy Ortiz woke before dawn to buy ice. It was 2012, and Hurricane Sandy had reclaimed Lower Manhattan for Mother Nature. Making landfall near Atlantic City, it swept north, ravaging the New Jersey coast, destroying thousands of homes and inundating New York City with waves as high as 14 feet.

Sandy shuttered Wall Street, rattling global markets, and for a moment the storm restored Manhattan’s early 17th-century coastline. A brackish murk of waist-high water submerged all the landfill that humans had dredged, salvaged and shipped to widen the island, and that now supported the Franklin D. Roosevelt Drive. It also swamped a large cluster of public housing developments and a beloved but bedraggled ribbon of greenery built by Robert Moses during the 1930s called East River Park.”

“. . . . In the debate over what is officially called John V. Lindsay East River Park, I sensed there might be some useful lessons about how we got here and how we might try to think differently. The park saga is not a conflict between bad versus good actors, but a confluence of different interests, different areas of expertise, different notions of community. It is a parable of progress.”

David Lindsay Jr.
Hamden, CT | NYT Comment:
Great story, thank you Michel Kimmelman. It’s complicated, and hard to fathom what is best. It seems at first glance that the Dutch solution, the Big U, was always the best of the various options, with the longest timeline and deepest bow to ecology. Sorry DiBlasio killed it.
Sooner or later, more Americans will come to see that including nature, and allowing nature to thrive and do its thing, will be an essential part of any successful long term fight against rising seas and the disruptions of climate change.

Opinion | Haiti’s Best Hope for a Functioning Democracy – The New York Times


Ms. Clesca is a journalist, a civil activist and a member of the Commission to Search for a Haitian Solution to the Crisis.

“PORT-AU-PRINCE, Haiti — On the streets of Port-au-Prince in February, demonstrators demanded that the Haitian president, Jovenel Moïse, step down because he had overstayed his elected term. His administration had dissolved Parliament after failing to hold elections, and he had illegally packed the judiciary and electoral commissions. Armed gangs, acting with his support, massacred protesters and terrorized poor and powerless citizens. Government agencies were a shambles, as they have been for years.

With the United States and other countries providing unstinting support for Mr. Moïse, Haitian civil organizations realized that the only way Haiti would be saved was if they saved it.

That month, groups representing unions, professional associations, farmers’ alliances, human rights and diaspora organizations, Voodoo groups and churches formed the Commission to Search for a Haitian Solution to the Crisis. I am one of 13 commissioners.”

Opinion | Where the Pro-Choice Movement Went Wrong – The New York Times

” . . .  Chief among those mistakes was the relative neglect of grass-roots groups in states where the battle over abortion access has been quietly waged for half a century. A key turning point came in 1992, when the Supreme Court overhauled Roe in Planned Parenthood v. Casey, allowing states to restrict abortion before viability as long as they didn’t impose an “undue burden” on those seeking such care. This opened the door to states chipping away at abortion access through incremental restrictions — a trend that accelerated after the 2010 midterm elections, when a Tea Party-backed wave swept state legislatures.

The Casey decision “could have been, and probably should have been, a moment where abortion-rights organizations funneled attention and resources toward local and state-level organizations,” said Meaghan Winter, author of “All Politics Is Local: Why Progressives Must Fight for the States.” National groups, Ms. Winter said, should have been thinking “in terms of both changing the culture, and building clinics, doing whatever it took on a logistical level to provide access, and thinking about creative ways to build electoral power.”

That didn’t happen — at least not to the extent that it should have.

Instead, Ms. Winter writes, national abortion-rights groups and the progressive movement at large have tended to focus on federal policy and elections and on defending access through federal courts, while neglecting many fights at the state level. While big-name organizations like the American Civil Liberties Union and Planned Parenthood have long maintained a presence in states including Texas, those state groups operate independently and must raise much of their own money.

That often puts groups in conservative states at a disadvantage. For example, the Texas A.C.L.U. — which has the job of opposing attacks on the rights of transgender students and immigrants as well as efforts to roll back abortion access and voting rights — had a budget of about $5 million in 2018, similar to that of its counterpart in the much smaller state of Massachusetts.

Investing in states matters because states are often laboratories for a movement’s boldest ideas — like S.B. 8, with its unusual enforcement mechanism that’s made it extremely difficult for abortion providers to fight it in court.”

Thomas Friedman | Trump’s Iran Policy Has Become a Disaster for the U.S. and Israel – The New York Times

“The judges have voted and the results are in: President Donald Trump’s decision to tear up the Iran nuclear deal in 2018 — a decision urged on by his secretary of state, Mike Pompeo, and Israel’s prime minister, Benjamin Netanyahu — was one of the dumbest, most poorly thought out and counterproductive U.S. national security decisions of the post-Cold War era.

But don’t just take my word for it.

Moshe Ya’alon was the Israeli defense minister when the nuclear agreement was signed, and he strongly opposed it. But at a conference last week, he said, according to a summary by Israel’s Haaretz newspaper, “as bad as that deal was, Trump’s decision to withdraw from it — with Netanyahu’s encouragement — was even worse.” Ya’alon called it “the main mistake of the last decade” in Iran policy.

Two days later, Lt. General Gadi Eisenkot, Israel’s top military commander when Trump withdrew from the deal, offered a similar sentiment, which Haaretz reported as “a net negative for Israel: It released Iran from all restrictions, and brought its nuclear program to a much more advanced position.”

It sure has. The International Atomic Energy Agency recently reported that Iran has amassed a stock of enriched uranium hexafluoride that independent nuclear experts calculate is sufficient to produce weapons-grade uranium for a single nuclear bomb in as little as three weeks.”

Shingeki No Kyojin Opening 1 [With Lyrics] – YouTube

I can not find a copy of the violent cartoon video that Paul Gosar put up on his twitter account. It apparently including killing scenes from the animation above, only with the killer having Gosar’s head, and the victim executed had the head photo shopped, of A.O.C. The next scene used, was of the flying ninja attackint a giant head, and here it was Gosar attacking the head of Joe Biden.

How to Store Your Covid Vaccine Card or Test Results on Your Phone – The New York Times

The state of the digital Covid vaccine card — the bar code that we store on our phones and present to businesses and venues as proof of inoculation — is chaotic.

“While some states, like California and New York, accept digital records as proof of vaccination to allow entry into restaurants and other businesses, states like Alabama, Arkansas and Florida have banned their use. That means anyone who plans to travel in the United States this holiday season has to research the policies at the destination.

Yet it’s indisputable that a digital card is far more convenient than a physical record. For many, the thought of misplacing a paper record may induce great anxiety, so it’s nice to have our inoculation data on devices that we carry everywhere. And companies like Apple and Google have come up with convenient ways to store and retrieve our vaccine credentials.”

Peter Coy | A Spirit of Gratitude Is Healthy for Society – The New York Times

Opinion Writer

“Greetings as we approach the 400th anniversary of the first Thanksgiving celebration. The Pilgrims in 1621 had much to be thankful for. They had arrived a year earlier with “no friends to wellcome them, nor inns to entertaine or refresh their weatherbeaten bodys, no houses or much less townes to repaire too, to seeke for succoure,” in the words of their leader, William Bradford. The Wampanoags, hoping the white settlers would help them fight other tribes, helped them survive the harsh winter. The wary allies celebrated that fall with a feast of turkeys, ducks and venison, although probably not cranberry sauce or pumpkin pie.

What does giving thanks have to do with economics? A lot, actually. I apologize if this sounds like an imitation of a David Brooks column, but the truth is that a spirit of gratitude motivates precisely the behaviors that a successful economy requires, particularly patience and generosity. For this newsletter I interviewed David DeSteno, a professor of psychology at Northeastern University (about 35 miles from where the Pilgrims landed), who is one of the leading authorities on the social effects of gratitude.

DeSteno’s recent papers include “Gratitude Reduces Consumption of Depleting Resources,” completed last year with Shanyu Kates, and “The Grateful Don’t Cheat: Gratitude as a Fount of Virtue” written with Fred Duong, Daniel Lim and Kates and published in Psychological Science in 2019. He published a book this year titled “How God Works: The Science Behind the Benefits of Religion.” I also recommend a talk that he gave at Google in 2018 on the topic of gratitude.”

David Lindsay Jr.
Hamden, CT | NYT Comment:
Thank you Peter Coy. I just sent the following to your newsletter email:
I just turned 69 yesterday, and it is very tempting to say, What is there to be grateful for? I quickly smile, to communicate the intended humor, and my loving partner chirps back, Well, consider the alternative. I’m grateful for a beautiful partner, house, family, and friends. I’d like to include neighbors, but they refuse to speak to me, for not being just as Republican as they are, or something. I was never good at keeping my opinions to myself.
I am grateful for having Peter Coy in my life, first at Business Week, which I have subscribed to for decades, and now, at the New York Times. I deeply respect journalists who work hard to figure things out and explain them. That is what I aspire to do every day, as I read and write about climate change and the sixth extinction.
I’ve just added to my new manuscript, a joke reported the other day by Thomas Friedman, that he heard at the Cop 26 climate summit in Glasgow. Two planets are talking to each other, One looks like a beautiful blue marble, and the other a dirty brown ball. “What on earth happened to you?” the beautiful planet asks the brown one. “I had Homo Sapiens,” answers the brown planet. “Don’t worry,” says the blue planet. “They don’t last long.”
Yours, David
Author of: “The Tay Son Rebellion, Historical Fiction of Eighteenth-Century Vietnam” Blogging at: InconvenientNews.Net,

Paul Krugman  | What Europe Can Teach Us About Jobs – The New York Times

“Americans have a hard time learning from foreign experience. Our size and the role of English as an international language (which reduces our incentive to learn other tongues) conspire to make us oblivious to alternative ways of living and the possibilities of change.

Our insularity may be especially damaging when it comes to countries with whom we have a lot in common. Western Europe is our technological equal; labor productivity in northern Europe is just a little below productivity here. But Europe’s policies and institutions are very unlike ours, and we could learn a lot by looking at how those differences have played out. Unfortunately, any suggestion that Europe does something we might want to emulate tends to be shouted down with cries of “socialism.”

“. . .  Finally, let me offer a speculative hypothesis: Perhaps one reason Europeans aren’t engaging in an American-style Great Resignation is that they don’t hate their jobs quite as much.

Anecdotally, one factor behind Americans’ unwillingness to return to their old jobs is that enforced idleness during the pandemic gave many people a chance to reconsider their life choices — and a significant number may have realized that low-paying jobs with lousy working conditions weren’t worth having.

Of course, Europe is by no means a worker’s paradise. But some jobs that are grueling and poorly paid here are less awful on the other side of the Atlantic. Famously, in Denmark McDonald’s pays more than $20 an hour and offers six weeks of paid vacation each year. That may be an exceptional case, but the U.S. does stand out among wealthy countries for having a low minimum wage, for offering very little vacation time and for failing to offer parental and sick leave. Maybe the poor quality of U.S. jobs is one reason so many American workers are reluctant to return.

Which brings me to an under-discussed aspect of the current economic scene: Europe’s comparative success in getting workers idled by the pandemic back into the labor force.”

David Lindsay.   Amen.  Here are the two top comments at the NYT:

Times Pick

How can we possibly learn anything from France, the socialist dump? Have you ever been there? It’s terrible, all they have is great food and beautiful parks, amazing museums, walkable cities with excellent public transit, and a culture that values time with friends and family.

9 Replies724 Recommended
Socrates commented November 29

Downtown Verona, NJ Nov. 29

Europeans understand inherently that they are part of society. Many Americans fail to grasp the concept of society, preferring the catastrophic and ludicrous myth of “individualism” that has produced moral, intellectual and economic poverty for tens of millions of Americans. They pretend that millionaires and CEOs built companies all by themselves and they fall for that nonsensical myth and they blindly worship “individual” success. No doubt that there are many talented CEOs and business owners who were the driving forces behind their company’s successes, but they all needed a staff and government infrastructure and a stable society to build that success. But Americans have tolerated the broad daylight highway robbery transfer of wealth from worker wages to CEO and executive wages for fifty years now, aided and abetted by the marketing of largely unregulated “capitalism” and greed to the great detriment of workers, who increasingly are relegated to poverty wages. CEO compensation in the USA grew 940% from 1978 to 2019 while typical worker compensation rose just 12% during that time. CEO’s and executives are not gods or superheroes; they’re just people. The federal minimum wage in the USA has been frozen at $7.25 per hour since July 2009, thanks in large part to America’s vulture capitalist culture feverishly peddled to Americans by billionaire right-wing profiteers. America’s vulture capitalists need to be regulated and taxed back to civilization and a decent society.

21 Replies695 Recommended
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