The Cost of Being Green

Cordless electric lawn mower... bah.

Here's my lawnmower... no gas, no electric.  The only CO2 created and emitted to use this thing comes out of my own lungs.  Granted my yard is teeny-tiny.  But seriously, these newer manual reel mowers are a big improvement over the old fashion ones and I actually find it enjoyable to use.

The weird thought occurred to me as I drove into work this morning.  How many solar panels need to be built before we experience a global cooling effect due to them?  After all, we are deriving energy from the suns rays that would normally be heating the planet.  Come on ScottThornley ... do the math on this one please.

Last I looked, solar panels on roofs would still be on this planet I doubt there'd be any noticeable effect due to energy absorbed by solar panels vs roofs, but that is just a wild-assed guess.

Here's some other random thoughts though:

Even if you are using natural gas or coal to produce electricity to run your vehicle, the generators found in power plants run much more efficiently than the engine in your vehicle. So even with the US average 7.5% transmission losses, you are still going to be producing less pollution per unit of energy. It's not just pollution relocation. And as Zeelander said, producing gasoline and getting it from the oil fields to your gas tank also requires additional energy. There are "transmission losses" in that energy supply chain too.

Obligatory math portion - Take Seans new EV with a range of 150 miles. Now take the rule of thumb that an EV can travel 5 miles per kilowatt*hour and you come up with a power cell capacity of 30 kW*hrs, which can be charged in 15 minutes using a mega-charger. With an input voltage of 220 volts, how much current (in Amperes) must be passed into the mega-charger for those 15 minutes? * The answer will explain why a mega-charger is not portable. And will also explain why you will not get a mega-charger in your home any time in the near future.

A hybrid that's been in the experimental phase for a while now, but which I personally would like to see out on the streets:  http://www.grc.nasa.gov/WWW/RT1996/6000/6920v.htm   

There's a company here in Silicon Valley that purports to have a process that will allow them to make solar panels for $1 a watt. If this is true, and drives down solar panel cost  to the $1/W level, then solar panels for electrical generation really do become a smart business decision.

Regards,
Scott

*For the mathematically disinclined: 30kW*hrs, charged in 15 minutes means you need a charger capable of producing 120kW. 120kW/220V = 545A (youch!!!!)

The weird thought occurred to me as I drove into work this morning.  How many solar panels need to be built before we experience a global cooling effect due to them?  After all, we are deriving energy from the suns rays that would normally be heating the planet.  Come on ScottThornley ... do the math on this one please.

Last I looked, solar panels on roofs would still be on this planet I doubt there'd be any noticeable effect due to energy absorbed by solar panels vs roofs, but that is just a wild-assed guess.

I assume you meant "solar panel OR roofs would still be on this planet".

Solar panels and roofing panels have entirely different characteristics.  Roofing panels will transform the suns rays into heat (you can feel it radiating when standing on a roof on a sunny day) or reflect the suns rays.  Solar panels transform the rays to electricity, reducing the effective heat transformation or reflection.

So let's see, convert the electric power per square foot for solar panels to equivalent units of heat ...

-Allen

Cordless electric lawn mower... bah.

Here's my lawnmower... no gas, no electric.  The only CO2 created and emitted to use this thing comes out of my own lungs.  Granted my yard is teeny-tiny.  But seriously, these newer manual reel mowers are a big improvement over the old fashion ones and I actually find it enjoyable to use.

I tried a push mower before I went electric. It would just roll over tall weeds without cutting them. It would also just slide over wet grass, and the wheels couldn't get a grip. For the right kind of lawn, they're great, but the electric works best on the kind of jungles that I typically call a lawn.

Allen,

Take the efficiency of solar panels into consideration. Not even the majority of solar energy is converted into electricity, in fact efficiency is normally calculated in the low teens, with experimental cells getting into the 40% range. So most of the energy hitting a solar panel is absorbed/radiated/conducted/convected in much the same way as energy striking a standard roof.

Now lets look at scale. Total planetary solar absorption is about 174 petawatts. Current energy consumption is 15 terawatts, or about .009% of energy absorption (yes, the decimal is in the right place). So even if the planet achieved 100% solar conversion, my (now it's scientific!) wild-assed guess remains that there is going negligible effect from solar panels vs simple roofs.

Regards,
Scott

Polelpole,

Thanks for the info on PG&E supply, eventhough I was born here and have spent my entire life in the SF bayarea I have been making an effort to get myself think more globally.  NIMBY might make me feel better today, but the CO2 produced in China will eventually affect us as much as it does them and viceversa.

In this thread I've seen some coments on "energy consumed" to produce fuela and electricity.

Some info I have that might not be readily available is how much energy is consumed to make motor fuels.  It used to be my job to calculate that number.

This is just the energy consumed inside the refinery fenceline.

About 7 years ago when I did it our refinery which was a little better than average on energy consumption used about 12.3% of it's total (energy) intake (crude oil and natural gas) to produce products (gasoline, jet fuel, and diesel).

Since then, I am no longer involved in that field but there has been some improvement to say about 11%. Again this just inside the refinery fenceline, and doesn't include drilling, production, transportation, etc.

Believe it or not most refineries are constantly working to reduce their CO2 emissions, not because of any environmental concern, but, because it saves them money, energy is expensive these days, the environmental benefit is what they advertise, but it's still about the money.

Obligatory math portion - Take Seans new EV with a range of 150 miles. Now take the rule of thumb that an EV can travel 5 miles per kilowatt*hour and you come up with a power cell capacity of 30 kW*hrs, which can be charged in 15 minutes using a mega-charger. With an input voltage of 220 volts, how much current (in Amperes) must be passed into the mega-charger for those 15 minutes? * The answer will explain why a mega-charger is not portable. And will also explain why you will not get a mega-charger in your home any time in the near future.

Exactly...but it was never inteded for home use.  It is intended to serve as a e-gas station, and as such the industrial wiring would not be an issue.  Plug in, buy some jerky and a slurpy, and you'd be ready to go for another 100 miles.  For commuting, plug it in at the office (we already have plugs in our carport) and/or [lug it in when you get home.  For my long (55 miles one way) commute it would be easy, and work 99% of the time I drive to work.

OK.   My wild-assed curiosity is satisfied for the time being.

BTW, of the 174, 4% is reflected by the ground and 51% is absorbed by the ground.  The rest is either absorbed or reflected by the atmosphere and clouds, which would never make it to a solar panel.

http://en.wikipedia.org/wiki/Earth%27s_energy_budget

BTW, tidal energy is only about 3 terawatts, so tidal energy could never supply the 15 terawatts currently consumed.

-Allen

Polelpole,

Thanks for the info on PG&E supply

Of course the breakdown is different in different parts of the world. Here's the total energy breakdown worldwide.  This is a breakdown of the 15 terawatts Scott was mentioning.



-Allen

Actually, when you use electricity it generally ends up in the form of heat, be that friction on a car, light from a bulb absorbing into the walls, or simply heat in the form of V*I losses in various electronics.  The solar panel only serves to move some of the heat from the energy that strikes the roof to wherever the energy is being spent.  The only way it doesn't end up as atmospheric heat is if you shine a laser into space.  However, it WOULD cool the earth if all our houses had mirror-like roofs on them to reflect the light back to where it came from.  This would reduce the heat island effect of urban areas, and with enough coverage could even cool areas to below what they would be in forest.  There may be some improvements in solar panels on this regard, if they reflected the 60% of light they can't use, that'd cool the earth and make green power at the same time.  I don't think folks are really far enough along to be taking this into account though.

The big problem with electric vehicles right now is that the batteries aren't capable of that many charges before they need to be replaced.  Hybrid cars typically only use 10-20% of the batteries capacity (compared to a digital camera for the same battery type) to extend the life of the battery, but that requires 5x the battery.  We're all familiar with how our phone and camera's batteries wear out after about 2 years, and the same will happen to batteries in a car.  Fortunately there are improvements being made in this area, recently I read this article: http://news-service.stanford.edu/news/2008/january9/nanowire-010908.html which if it pans out would certainly be nice.  However, for now if you buy an electric vehicle, you pay several times more to be able to store a KWH in a battery than it costs to get it from PG&E because of the batteries high cost and relatively short life.

Regarding putting a solar panel on the roof of the car, you may be able to squeeze 200-400W of panels on the car, but relative to the 20-30kWH battery, you'd need 100-200 hours of peak sun to charge the car.  In practice you're likely to get 2-4 in a day.  It'd be sufficient to make up for a battery that tends to gradually self-discharge, but it'd only be good for perhaps half a mile per day.

I used to drive a geo metro that go mileage in the upper 40s, comparable to a prius in a car that's equally small and fugly, but only cost something like 5k new.  Sadly that car was discontinued when 80c gas was available in 98-99 (in rural minnesota at least).  If they'd just held out another year or two it'd still be a big seller.

I'm only partly suspicious of the maintenence of electric vehicles, their parts are far simpler (and cheaper other than the battery) than normal cars.  No fluids to change, perhaps no transmission or cooling system even.  Hybrids are another story, they've got all the crap needed for an EV and and ICV under one hood. 

Also keep in mind that it takes the equivalent of 1-3000 gallons of gas to make and deliver a car, depending on it's size and complexity to manufacture.  The 'greenest' solution is often just to keep driving the car you have for another generation rather than upgrading.  If you buy a new car and it only gets 10mpg better, say 30 to 40mpg, then you have to drive 120k miles to save 1000g of gas and simply break even compared to keeping the 30mpg car.  Companies always want us to buy something to help the environment, but often not buying something is the better choice. 

I'm sitting out this generation of clean cars, they're simply not cost (or particularly environmentally) effective no matter how you cut it.  The only appeal is getting to use the carpool lane, but that's not going to last either as their adoption gets wider.  My work is fine with 9:30 to 6:30 days anyway, all carpool lanes did was kill family dinner and improve the viewership of the tonight show. 

Perhaps I'll buy a used hybrid in 5-10 years and use my engineering  knowhow to pimp it out with a modern battery.  I may even hold it in place with a 2x4...  Recycling cars is much better for the environment than buying new ones.  The greenest car you can buy right now is a used geo metro with the 3cyl engine and manual transmission.  They're really cheap too...

I may even hold it in place with a 2x4...

 

Lawnmowers.....humbug.......

I use ROUNDUP.

How's THAT for being GREEN.....!!!...???...

Judd

A lawnmower usually only uses about 10-20 gallons of gas in it's life.  This is another area where the returns of trying to 'green' the thing is pretty small.    Electrics do cost about the same, but they're only really practical if your entire front and back yards are reachable within 50' of an outlet.  They are also considerably weaker and don't do well at all for the weed and fire-suppression mowing of grasses outside my lawn in the spring.  The gas mower happilly chomps through knee deep brome.

A lawnmower usually only uses about 10-20 gallons of gas in it's life.

Yeah but ...

Gallon for gallon — or, given the size of lawnmower tanks, quart for quart — the 2006 lawn mower engines contribute 93 times more smog-forming emissions than 2006 cars, according to the California Air Resources Board. In California, lawn mowers provided more than 2 percent of the smog-forming pollution from all engines.

So your 10-20 gallons is effective 930-1860 equivalent automobile gallons ... at least in terms of smog forming pollution.

Of course a catalytic converter would help this problem.  And in CA, I think small engines are now required to have them.  The rest of the country doesn't seem to require them.

-Allen

Still, thats only 2% of the smog produced by engines, not including fireplaces and barbecues...  That's pretty small-fry to be going after, and the 20-30% price increase to small motors is much greater than the cost to put catalytic converters in cars.