Post #1721: Gas versus electric lawn mowing, part 1: The conundrum

 

Preface:  I was an early adopter of electric lawn mowing.  Early, in this case, being somewhere around 1995, well before battery-powered electric mowers existed.  But after a couple of burnt-out mowers and many trashed extension cords, I gave up and bought an efficient gas walk-behind mower. 

That was circa 2015, and I have not looked back.  Until now.  This is the first of a series of posts looking at gas versus electric lawn mowing.

Part 1:  The conundrum

I keep reading ever-more-outlandish statements about just how much pollution gas lawn mowers generate.  Depending on which source you read, you will come across this generic format:

  • One hour of mowing your lawn using some gas-powered lawn device
  • produces as much something-something-something
  • as 200 or 300 or 350 miles of driving something.

Weirdly enough, it’s always one hour.  Everything else varies from source to source.  In addition, I am not the only person to have noticed that these car-versus-mower statements are all over the map.  This has gotten to the point where the EPA apparently doesn’t support statements like this any more (reference).

I’m sure there’s some truth in there, somewhere, but that has the look of a standard advocacy statement.  Typically, if you take one of those apart, you’ll find that somebody has purposefully created a worst-possible-case-vs-best-possible-case contrast.  Statements like that are crafted to convince rather than to inform.  And that’s done with forethought,  in pursuit of some presumed policy or economic goal.

Worse, as variants of that get tossed around, further and further from the actual research, they start to take on urban legend aspects.

Let’s play “spot the loony”.  Consider this statement, from an otherwise reputable source, Family Handyman magazine:

One hour of running a gas mower emits as much carbon dioxide as driving a car 300 miles, ...

That’s obviously a mistake.  Carbon dioxide (C02) emissions are directly proportional to the amount of gasoline burned.  Each gallon of gas generates about 20 pounds of C02 (Source:  EPA).  The average new (2021) U.S. passenger vehicle, including electric and plug-in cars, gets less than 25 MPG or equivalent (Source:  EPA).  Taken literally, the statement above says that a lawn mower burns (300/25 =) 12 gallons of gas per hour?

Must be one hell of a lawn mower.  Big agricultural combines (as above) can easily have that level of fuel consumption.  But not your typical 21-inch 3.5 HP Briggs and Stratton lawn mower.

My wife confidently informs me that we burn two gallons of gasoline per year, cutting our grass.  She’s confident because a) she mows the lawn, and b) she hates putting the gas can in her car.  So she’s sure she does that once per season.   This, on a half-acre suburban plot, less the footprint of house, driveway, and landscaping.

By contrast, for cars, in the U.S., we burn an average of about 650 gallons of gasoline per licensed driver per year (Source).  For me and my wife, if we were average, we’d be burning 1300 gallons of gasoline per year, in our car. (We aren’t — we drive a Prius Prime and arguably use about 40 gallons of gas per year in that.)

Plus two more gallons, for the lawn mower.

So there’s the conundrum.  Where does this gas-lawn-mower-as-environmental-horror-story come from, given how little fuel the typical suburbanite consumes for lawn mowing, compared to driving?

For sure, the carbon footprint of our gas lawn mower is rounding error in the context of total household fossil fuel use.  Not because small gas engines are any great shakes.  Simply because the fuel used to mow the lawn is negligible.

For perspective, using Virginia’s power generation mix (0.65 lbs C02 per KWH), two gallons of gasoline generates as much C02 as 60 kilowatt-hours, or roughly 160 watt-hours per day.   Based on these typical wattages, the gas lawn mower has the same carbon footprint as the following daily use of these home appliances:

In short, for my primary environmental concern — global warming — mowing the lawn just doesn’t matter.  Or, it matters less than many other common activities of daily living, such as washing dishes or watching TV.

But I still would like to know the full story here,  Given the small amount of gasoline consumed, how closely does whatever-it-is that is the underlying research actually apply to my situation?  Should I consider early retirement for my gas lawn mower, in favor of battery-powered?  Should I plan on buying a battery-powered mower if and when my current one dies?

I already know some of the answers.

Briefly:   First, the horror story is about smog (not carbon footprint).  Second, it focuses on major small-engine consumers of gasoline.  The total environmental impact appears to have been estimated based on consumption of 3 billion gallons of gasoline annually, for lawn and garden equipment.  With lawns surrounding roughly 100 million U.S. households, that works out to about 30 gallons of gas, per lawn, per year.  Or about 15 times the rate at which my mower uses gas.

The upshot is that I’m not deeply concerned about this.  But I would like to know more.  The rest of the posts in this series will dig a little deeper into this, including (if possible) finding the original EPA research that has spawned this class of gas-lawn-mower-bad advocacy statements.

More to come.  It’s a nice day.  I’m going to go work in the yard now.

Post #1720: The Systemic Risk Clause and the FDIC

 

This is here only because it’s hard to look up, and so many people get it wrong.  Here’s the law that enables the FDIC to pay off all deposits in the event of a bank failure.  (Actually, it lets the FDIC do pretty much whatever seems to be required):

From the Federal Deposit Insurance Corporation Improvement Act of 1991 (FDICIA):


PUBLIC LAW 102-242—DEC. 19, 1991 105 STAT. 2275

"(G) SYSTEMIC RISK.—
"(i) EMERGENCY DETERMINATION BY SECRETARY OF THE
TREASURY.—Notwithstanding subparagraphs (A) and
(E), if, upon the written recommendation of the Board
of Directors (upon a vote of not less than two-thirds of
the members of the Board of Directors) and the Board
of Governors of the Federal Reserve System (upon a
vote of not less than two-thirds of the members of such
Board), the Secretary of the Treasury (in consultation
with the President) determines that—
"(I) the Corporation's compliance with subpara-
graphs (A) and (E) with respect to an insured
depository institution would have serious adverse
effects on economic conditions or financial stabil-
ity; and
"(II) any action or assistance under this subpara-
graph would avoid or mitigate such adverse effects,
« the Corporation may take other action or provide
assistance under this section as necessary to avoid or
mitigate such effects.

Source: Google link to Govinfo.

In short, it takes a two-thirds majority of both the FDIC governing board and the Federal Reserve Board in order to invoke the FDIC’s systemic risk clause.  Also, agreement from the Secretary of the Treasury and the President of the U.S.

So, it’s kind of a big deal.

Based on what I’ve read, prior to this, it was common for the FDIC to make a case-by-case determination of whether or not to cover all deposits, regardless of the stated limits on coverage.  The Congress got tired of that and decided to codify the regulatory procedures, in this 1991 legislation.

After that codification in 1991, the systemic risk clause has been invoked rarely over the following decades.  Most notably, it was invoked for several large banks during the 2008 banking crisis.

So it’s notable in that it’s being used here.  That should be, at most, a once-a-decade event.

You do have to wonder when or whether the other shoe is going to drop.  Or whether we’ve had our once, for this decade.

Post #1719: A brief note on the 1980s Savings and Loan Crisis, or why sometimes It’s (not) a Wonderful Life.

 

FSLIC.  Raise your hand if you are old enough to recall what that stands for.

Briefly, FDIC : Bank :: FSLIC : Savings and Loan

You have to interpret the second  “:” as “was to”, not “is to”.  The Congress formally declared the Federal Savings and Loan Insurance Corporation (FSLIC) dead in 1989, after a decade-long illness.  It was beyond bankrupt at the time.  Its functions were subsumed into the Federal Deposit Insurance Corporation (FDIC).

I mention this bit of economic history because of the recent failure of the Silicon Valley Bank.  That seems to have been driven by the same factor that drove the majority of S&Ls into bankruptcy in the 1980s.

Briefly, they borrowed short and lent long.  Short, as in short-term.   The money they took in — borrowed from their depositors — could be withdrawn at any time.  Long, as in long-term.  They apparently bought a lot of U.S. Treasury bonds. Which, although liquid enough at any given time, are still long-term loans to the U.S. Treasury.  (And a fundamentally odd thing for a bank to invest in, when you get right down to it.  It’s as if they couldn’t be bothered to find something with a better rate of return.)

In any case, as with any fixed-return asset, the price of those bonds drops as interest rates rise.  Owning a lot of fixed-return long-term securities, in an era of rising rates, is a recipe for bank failure.  (Or, as in the case of the 1980s, S&L failure.)  As I shall explain below.

And, after more than a decade of more-or-less zero inflation and below-zero real interest rates, I have to wonder how many more banks are now lurking out there, in our current environment of rising interest rates, waiting to fail from that same root cause.

If you just want to see a professional write-up of the S&L crisis — minus the dirt — this piece by the Federal Reserve Bank of St. Louis is about as good as it gets.


Skipping the details, how does the FDIC operate?

U.S. banking regulation has a lot of generally-unrecognized quirks.  Many of these derive from the fact that States were in the business of chartering banks long before the Federal government got in on that.  States never relinquished that right.  As a consequence, what appears to consumers today as a more-or-less monolithic industry is actually a mix of a institutions following different rules and regulations.

The practical consequence of this is that almost anything you say about bank regulation and deposit insurance will have some exception, somewhere.  In Virginia, it appears that all state-chartered banks are in fact FDIC insured, meaning that they are subject to Federal regulation.   But you can find states that allow some commercial banks to have no deposit insurance (e.g., CT), to (typically) states that operate bank insurance funds secondary to the FDIC, insuring deposit amounts in excess of the $250,000 FDIC limit (e.g, MA).  You can also find entire categories of bank-like institutions that only exist under state charters (read the CT reference above to get the gist of that).

The FDIC insures most bank deposits in the U.S., so it’s worth a paragraph or two to explain the finances of that.  (The FDIC reference page is here, the corresponding Credit Union reference page is here.).

The FDIC gives every bank a risk rating (termed CAMELS), based on factors such as capital adequacy and the riskiness of their underlying assets.  This risk rating seems to be a pretty good predictor of which classes of banks are at higher risk of failure.

Source:  Federal Deposit Insurance Corporation, Staff Studies. Report No. 2020-01. A History of Risk-Based Premiums at the FDIC, January 2020.

The FDIC charges banks a quarterly insurance premium based on the amount of insured deposits and the riskiness of the bank. As you can see, a large and risky bank might easily pay 10 times the insurance premium of a small bank with low apparent default risk.

Source:  https://www.fdic.gov/deposit/insurance/assessments/proposed.html

In normal times, best I can tell, on average, covered institutions pay insurance premiums equal to about 0.12 cents per dollar of deposits.   Effectively, that’s what you pay, in order to have your deposits insured.  The bank just makes that transaction on your behalf.  But the FDIC can add a temporary surcharge if the amount in the insurance fund gets too low.

The target value for the deposit insurance fund is 2% of the value of all of the covered assets (Source:  FDIC).  Which doesn’t sound like a lot, but the FDIC is a “full faith and credit” entity, meaning that the Federal government has to step in and make good on those insured deposits even if the insurance fund itself has been depleted.

(Oddly enough, while banks and S&Ls are insured by the FDIC, Federally-chartered credit unions are not.  They are insured by a different “full faith and credit” entity, the National Credit Union Share Insurance Fund, and are supervised by the National Credit Union Administration.)

That “designated reserve ratio” was 1.25% of assets before the near-death of our banking system in 2008-2009.  I went over this years ago, in Post #341.  Since the demise of the FSLIC in the 1980s, we’ve only had one episode where, arguably, the FDIC’s Deposit Insurance Fund was subject to significant strain.

The graph below, courtesy of the Federal Deposit Insurance Corporation (FDIC), show the surge in bank failures that occurred in 2008 and 2009.  In 2008, despite significant intervention by the Federal Reserve to try to stabilize the financial system, banks with assets amounting to more than a third of a trillion dollars failed.

Accordingly, the balance in the FDIC’s Deposit Insurance Fund ran negative during that wave of bank failures.  Near as I can recall, this got absolutely no press coverage at the time.  Plausibly, the FDIC kept fairly quiet about it, and at the same time the FDIC avoided a cash-flow issue by requiring banks to make their next three years insurance premium payments, up front, to keep the money flowing.  (That, from detailed reporting in the Journal of Accountancy.)

Source:  FDIC

Unsurprisingly, after that, they upped the target from 1.25% to 2% of covered assets.

In short, the FDIC’s Deposit Insurance Fund was stress-tested in that episode, came up a bit short, and, accordingly, has been required to run a bit more conservatively ever since.  Acknowledging that if things really go south, the full faith and credit of the U.S. government stands behind them.

Unlike the S&Ls, discussed below, the proximate cause for those bank failures was the collapse of the sub-prime mortgage bubble, leading to a sharp downward adjustment in US housing prices, of a sort that had not been seen in the US for generations.  The blue line below (from the Saint Louis Federal Reserve) shows an index of U.S. housing prices.  The hump, peaking around 2006, is “the housing bubble”.  The  red line, for reference, is the US Consumer Price Index.  The graph runs from 1975 at the left, the 2019 at the right.  The gray bars are recessions.

Basically, a lot of banks made what in retrospect were a lot of really bad loans, based on ludicrously inflated real estate prices.  Based, in turn, on what in hindsight was clearly a speculative bubble in real estate, driven by exceptionally easy credit, even for high-risk properties.

Finally, the billion-dollar question:  How much does the FDIC lose when it shuts down a bank?  Obviously, that varies, but after staring at a few tables in various sources, a good guess is about 8% of the assets of the bank.  So if the Silicon Valley Bank is typical, and has $200B – $250B in assets, the Deposit Insurance Fund can expect to take a hit of about $20B.  Far below the current balance of around $120B in that fund.


The 1980s S&L crisis and the death of the FSLIC.

Source:  An Examination of the Banking Crises of the 1980s and Early 1990s,

The first thing to grasp is that S&Ls are not the same as banks.  Back in the day, they were a distinct class of depository institutions with their own separate regulators and insurance fund.  For purposes of this discussion, these were institutions that, by law, offered savings accounts to small depositors and used that money primarily to fund home mortgages. In their heyday, half the home mortgages in the U.S. were funded by S&Ls.

Note that I said “savings accounts” above.  Not checking accounts.  The radical notion of allowing S&Ls to offer checking accounts (NOW accounts) did not occur until 1980, with the Congress’s first attempt to quash the S&L crisis.

The interesting historical difference between a savings account and a checking account is that you couldn’t demand to withdraw your money held in a savings account.  These days, all vestiges of restrictions in withdrawal from savings accounts have disappeared (reference).  But there was a time when S&Ls could say, sure, you can have your money — sometime.

In fact, I have both a checking and a savings account at my local credit union.  If you bother to read the fine print in the account agreement, I find the following disclosure:

" The Credit Union reserves the right to delay the availability of funds deposited to accounts that are not transaction accounts for periods longer than those disclosed in this policy."

Translation:  If they are having a problem, they have the right to prevent me from withdrawing money from my savings account.  Even now.  Even in 2023.  These days, with both savings and checking paying close to zero interest, this hardly matters.  I might as well keep the entire balance in checking.  But this is a holdover from the days of bank runs and interest-bearing savings accounts.  You got paid interest for your deposit, but the quid pro quo is that in the event of a bank run, you were stuck.  For other specialized types of saving accounts — Holiday Club, Christmas Club — the restrictions are more explicit, and typically involve penalties for excessive or early withdrawals.

And that’s by design.  With clauses such as that, the bank needs to keep fewer “reserves”, that is, less cash-on-hand and other liquid assets, to satisfy regulatory requirements.  This lets it put a higher fraction of deposits to work earning interest, and so (in theory) should lead to better economic performance.

In short, prior to 1970, say, S&Ls were a backwater of American banking.  They could only offer savings-type accounts, and they were highly restricted in the types of assets they could invest in.  The maximum interest they could pay on deposits was set by law.  By and large, they were community lending institutions that issued mortgages, and little else.

Then along came the economic turmoil of the 1970s and 1980s.  Let me summarize the situation — borrowed short and lent long — in one graph.

The key to understanding why the S&Ls were trapped by rising interest rates is to understand that as interest rates go up, the value of fixed-income securities goes down.  Among which are fixed-rate mortgages. When the prime rate is 4%, a mortgage paying 6% is an attractive investment.  When the prime rate hits 21.5%, not so much.  If you want to sell a 6% mortgage in that environment, you’re going to have to sell it at a deep, deep discount.

And so, as rates rose, two things happened.  The value of S&L’s existing mortgage fell, so that if they had to sell them, they’d take a loss.  And, separately, they began to lose deposits, and (once rates were deregulated) then had to pay higher interest to keep those deposits. Higher than what they were earning on their portfolios of mortgages.

They were trapped.  If they liquidated their mortgages to pay off depositors, they took a loss.  If they raised interest rates enough to keep their depositors, they took a loss.  There was no way out.

Congress then spent the better part of a decade trying to do anything other than liquidate the bankrupt S&Ls.  They loosened restrictions on S&Ls.  They loosened them some more.  They basically urged S&LS to take ever-more-risky bets in the hope that they would somehow earn themselves out of the hole they were in.

In short, the Congress turned what had been a backwater of American banking was turned into America’s biggest casino.  All in the hopes that the S&Ls could earn enough to make up from the losses incurred by borrowing short and lending long in an era of rising interest rates.

From the original chart, it looks like a lot of S&Ls lasted until the end of the 1980s, but that’s an illusion.  Regulators turned a blind eye to the fact that many of those S&Ls were technical bankrupt, because they didn’t have enough money in the FSLIC to liquidate them.  At the time, the term was “zombie” S&Ls. Technically, dead, yet still functioning.  Meanwhile, the industry kept falling deeper and deeper into the hole.

After a few well-publicized scandals, the Congress finally threw in the towel circa 1989.  About a third of S&Ls were declared insolvent and were liquidated.  The FSLIC was bailed out by abolishing it and transferring the liabilities to the FDIC.  I assume the taxpayers in general made up for those cumulative losses, but I haven’t bothered to look up the details of that final FSLIC transaction.

I’m sure there was plenty of malfeasance along the way.  And some pre-existing regulations got in the way.  But the basic story — the reason a third of the industry went bankrupt — is far more mundane.  A combination of

  • Lending long (e.g., 30-year fixed mortgages).
  • Borrowing short (e.g., checking deposits, savings deposits, CDs).
  • Rising interest rates.

That’s just bad news, no matter who the actors are.  Maybe they have adequate capital and current earnings to keep going.  Maybe not.


And now?  Of toilet paper and bank runs, or bank runs were the original flash mobs.

Much like the 1970s/1980s, we’re now in an era of rising interest rates, following a prolonged period of low interest rates and low inflation.

Public information about of the failure of the Silicon Valley Bank sounded like the S&L crisis all over again.  Sure, if you look hard enough, you can find some combination of malfeasance and incompetence.  But from what I’ve read, the main problem is that they tied up much of their capital in long-term Treasuries.  Borrowed short, lent long.  Which, in the era of stable and low interest rates that existed from 2008 to circa 2022, was just fine.  But in an era of rising rates, was a form of economic suicide.

As long as their depositor base remained stable, that wasn’t necessarily a problem.  As long as they could earn enough to stay in business, they didn’t have to realize the losses on those long-term bonds.

But as soon as somebody suggested that withdrawing your money might be prudent, it was game over.  That rapid withdrawal of funds forces them to sell off assets to pay back their depositors.  And if the bulk of your assets are now far under water — well, you’re bankrupt in short order.

Are there more of these in the pipeline?  Now way for the public to know.  But I wouldn’t be surprised. And, I wouldn’t be worried either.  If you look at the numbers, banks fail all the time.

The problem here isn’t with the regulators.  Having learned some hard lessons from the foot-dragging of the S&L crisis, our regulatory authorities don’t screw around when a bank is in deep trouble.  They come down like a ton of bricks.  That’s not because they’ll somehow salvage more value out of the bank if they do that.

The problem is that — let’s face it — people are idiots.  Bank regulators act decisively to quash any general run on the banks.  The same mentality that gave us months of toilet paper shortages during the pandemic will give us bank runs. 

Now, deposit insurance should have put an end to that.  But in the era of constant internet disinformation, you know there’s somebody out there, right now, trying to start a bank run just to see if they can do it.  Maybe a foreign government.  Maybe just a home-grown jerk.  It doesn’t really matter.  Not to mention that you don’t even have to get up out of your chair to move your money out of a bank.

My take on it is that for the Feds to come out and say, hey, you’re covered, no matter what the size of the deposit?  I don’t necessarily think that was good policy.  I don’t think it was bad policy.  I think it was probably the only policy that would work, in this circumstance.

Because now deposit insurance isn’t just facing traditional human stupidity.  It’s facing stupidity, as amplified by social media and the internet.  Bank runs were the flash mobs of their day.  My guess is that bank regulators have to work faster and harder now, to stop those, than they have for the past half-century.  So far, they seem up to the task.  Let’s hope it stays that way.

 

Post G23-008: Simple geometry of sun and shade, or, keep your gnomon pointing north.

 

This post is about making sure my new garden beds don’t end up in the shadow of my back porch, during the summer.  Based on the length of the shadows today, in late winter.  And, ultimately, based simply on the height of the porch roof.

To cut to the chase:  If you use Excel, and the NOAA sun-angle calculator, you can accurately predict the length of a shadow, for any date and time, anywhere on earth, via this formula:

Shadow length = obstruction height * cotangent (solar elevation angle in degrees * π / 180)

The π / 180 is there because Excel wants to see angles expressed in radians.  If you’re using a calculator that accepts angles in degrees, omit that.

 

Continue reading Post G23-008: Simple geometry of sun and shade, or, keep your gnomon pointing north.

Post #1716: COP out. Does it ever get cold enough, in Virginia, to make gas heat cheaper to run than a modern heat pump?

 

Edit 1/5/2025:  Since I wrote this, I had a new heat pump installed.  It’s an air-source, two-headed mini-split heat pump.  See Post #2060 for the reasoning. 

The “which fuel is cheaper” analysis below needs to be modified a bit, because the “regular” unit I bought only works down to 5F outdoor air temperature.  At which, it still runs at COP 2.1 (see below).  But below which, it (presumably) does not run.  So, where I talk about temperatures of zero, below, assume a better unit than what I actually bought, that actually runs down to zero F.

Original post follows:

In Post #1706, I determined that, for heating my home here in Virginia, it was far cheaper to run my heat pumps than to run my natural gas furnace.  That’s based on costs of $1.70 per therm of natural gas, and $0.12 per kilowatt-hour (KWH) of electricity.  Like so: Continue reading Post #1716: COP out. Does it ever get cold enough, in Virginia, to make gas heat cheaper to run than a modern heat pump?

G23-006: The sunniest spot in a shady yard? Part 1, geometry.

 

This is the first of two posts on finding the sunniest spot in a yard that has shade trees on either side.  This one uses geometry.  The next one will use time-lapse photography on a sunny day.

With any luck, both approaches will tell me the same thing.

If your yard is bordered by shade trees, locate the beds so that due south (180 degrees) splits the compass bearing from your bed to each line of trees.  This gives a surprising-looking result for my back yard.  It’s not at all what you’d naively think, just looking at the trees and the yard.

Garden bed location 1:  Wrong.

I started gardening seriously during the pandemic.  Temporary raised beds were made from recycled campaign yard signs and bamboo.  I placed those in seemingly-reasonable locations in my back yard. In part, they were filling in low spots on the lawn.  But it seemed like they were located so as to get the best sun.

I’m now getting around to putting in something more permanent.  This time, I’m not going to wing it, but instead want to know what spot in my back yard gets the most sunlight.

It’s not obvious.  I have tall trees on either edge of my yard.  And, interestingly enough, what appears to be the obvious solution — locate the garden beds in the middle of the yard, away from both tree lines — isn’t even close to being right.

So, eyeball a couple of birds’-eye views of my back yard, and see if you think I put the beds in roughly the right place:

Looks pretty good, doesn’t it?  You might even say that the location doesn’t much matter, because you’re going to get the same number of hours of sunlight almost anywhere in that back yard, regardless.  What’s shaded in the morning will be sunny in the afternoon, and vice-versa.

Problem is, an hour of sun is not an hour of sun.  Sunlight is much stronger around solar noon, and is weaker the farther you are from noon.  And, because the sun is due south at noon (in the Northern hemisphere), you have to know which direction is south, in order to judge what part of the yard gets the most solar energy.

Source:  Curtonics.com

You need to figure out the locations in your yard that place due south directly between those lines of trees.  Those locations get the greatest amount of high-intensity, near-noon sunlight.

To cut to the chase, you need to calculate where your potential garden site is, relative to the obstructing trees, and to due south.  The sunniest locations in the yard will have these two properties.

  • Due south (180 degrees) bisects the angle from your location to each side of obstructing trees.  E.g., find a spot where the bearing to one set of trees is 150 degrees (180 – 30), and the bearing to the other set of trees is 210 degrees (180 + 30).  That is, you get equal hours of morning and afternoon sun.
  • The angle from your location, to the obstructing trees, is as wide as possible.  For example, the location with a 60 degree spread above will get more total sunlight than a location with a 40 degree spread.   That is, you get as many total hours of sun as possible.

So now, take a look at my back yard, oriented so that south is directly down.  Do you want to change your prior answer?  By the look of the shadows, this is about 11 AM solar time.  Note that the left edge of the yard is already in sunlight.

 


Skirting a couple of pitfalls.

Let me take a brief break to mention a couple of pitfalls that can mess up your attempts to locate your garden in the sunniest spot on the yard.

Daylight savings time.  Man I hate having to get up at 2 AM to turn all the clocks forward, as required by law.  But the upshot is that solar noon occurs around 1 PM during daylight savings time.  For example, on the hourly insolation graph above, peak insolation occurs around 13:00, or 1 PM.  That’s not a mistake, that’s just daylight savings time.  So if it’s summer, and you look to see where the shadows fall at noon, you’re screwing up.  Because noon, daylight savings time, is actually 11 AM solar time.

Above:  Compass set up for 10 degrees west magnetic declination

Magnetic declination.  Declination is the extent to which magnetic north — where the compass needle points — deviates from true north.  Because of magnetic declination, you can’t simply use the raw readings from a standard magnetic compass in order to locate your garden in the right spot.

If you have a compass made for use on land, and it’s anything but the most basic compass, chances are you can adjust the compass to account for declination.

You can find the magnetic declination for your locality at the US Geological Survey, among other places. Currently, magnetic declination at Vienna VA is about 10 degrees west.  That means that the compass needle actually points to a heading of about 350 degrees, not 360 degrees (true north).  That’s about 2.5 degrees further west than when I was a kid in the 1970s.

Magnetic declination is one of those incredibly simple topics that always manages to get an incredibly opaque explanation.  But as long as you have a compass that can be set to account for your local declination, it’s really simple.  The picture above shows a compass set up for 10 degrees west declination.  Despite the fuzziness of the photo, I think it’s obvious that the compass body has been offset 10 degrees relative to the degree ring.  When the needle points to 350 degrees (10 degrees west of true north), 360 or 0 on the degree ring shows you true north.


The sunniest spots in my back yard are directly next to the trees.

I can now take Google Earth, and start drawing in the angles between various backyard locations, and the ends of the lines of shading trees at the sides of the yard.  It’s a little crude, but the conclusion is inescapable.  I put the temporary beds too close to the middle of the yard.  For the most solar energy possible, they ought to be almost under the trees at the side of the yard.  Like so:

Which, to be honest, I would not have guessed, just eyeballing it.

Over the coming weekend, I’ll set up a stop-motion camera to film my back yard for one sunny day.  With that, I should be able to validate that the area that gets the most solar energy is the one outlined.  And I should be able to determine just how much energy I lose if I move away from that optimum spot.

Post G23-005: Wacky weather? No, just seems that way.

 

With last night’s frost, and this afternoon’s snowstorm, I’m trying to think back to the last time we had an 80 degree (F) day. 

Oh, yeah — day before yesterday.

Which got me to asking whether this most-recent temperature swing was unusual.  At Dulles Airport, they went from a high of 80F on Thursday afternoon, to a low of 27F on Friday night.   Or just over 50F swing over the course of two days.

As it turns out, that’s perfectly normal.  Below I’ve plotted the biggest two-day temperature swing, by year, at Dulles, through 2022.

Source:  Analysis of NOAA data, downloaded via https://www.ncdc.noaa.gov/cdo-web/

As you can plainly see, at least one event of this size seems to happen more-or-less every year.  The upshot is that in this part of the country, going from shorts one day to winter coat the next (or vice-versa) does not count as a particularly unusual weather event.

Post #1714: Ah, crap, another 80 MPG trip.

 

I am presently recovering from a severe shoulder sprain.

It was self-inflicted, the result of patting myself on the back too hard.

The problem starts with my wife’s Prius Prime.  It has more-than-met our expectations in every respect.  In particular, as-driven, it typically exceeds the EPA mileage rating, either on gas or electricity.

Lately, I’ve been trying a few techniques to try to squeeze some extra gas mileage out of the car.  Just some around-town trips, driving it to try to keep the gas engine in its most efficient zone.  Which, per Post #1711,  boiled down to fast starts on gasoline, followed by coasting on electricity.  Below, that’s an attempt to stay on the top of the green efficiency “hill”, followed by keeping the gas engine off while driving in the aqua “EV carve out” zone.  (The labels on the contour lines are “efficiency”, the percent of the energy in the gasoline that is convert to motion.)

Results were encouraging.  A couple of test trials showed mid-70-MPG for a series of trips and test runs, entirely on gasoline (using no grid electricity).  Given that the car has an EPA rating of 55 MPG for city driving, I figured I was doing something right.

But at some point, it dawned on me that

  1. the current EPA mileage test is based on the typical U.S. driver (i.e., somebody who drives like a bat out of hell, whenever possible), and
  2. I have no idea what my “typical” city mileage is, because I almost never drive the car, around town, on gasoline.

In short, I made a classic mistake of trying to do an experiment without a control.  I had no baseline to which I could compare my results.  I literally didn’t know what mileage the car would get if I wasn’t fooling around with the accelerator pedal.

I decided to find out.  Yesterday we took a trip out to my sister-in-law’s and back.  About 15 miles, mostly on 35 MPH suburban roads, rolling hills, no traffic to speak of.  Gas only.  Didn’t need the AC or the heat.  Relatively few stop lights.  Driving normally.  (But acknowledging that I’m a light-footed driver by nature, and that monitoring the car via a Scangauge 3 has done nothing but increase that tendency.)

In short, reasonably close to ideal conditions for a trip.

Results:  The odometer clicked over to 80 MPG for the trip, just as we were returning to our driveway.

I am reminded of the following medical advice:  If untreated, the common cold will last a week.  But with proper medical attention, you can expect a full recovery in just seven days.

Thus it would appear, for urban hypermiling in a Prius Prime.  As-driven, 80 MPG, for my suburban area.  No fancy footwork required.