Thursday, July 30, 2009

You Do The Math - Cell Phone Chargers Cause Global Warming

So I heard recently that kids' cell phone chargers are using up the world's energy supplies, and creating a big carbon footprint that will cause global warming. The helpful hints are for you to "stomp out" those carbon footprints, and tell your kids to unplug the chargers when not in use. Or ground your kid for a week.

Tell your kids not to worry, we'll put their fears to rest. And you can un-ground them, because today, You Do The Math!

I just happen to have a year old Motorola that has a 500 milliamp "wall wart", aka transformer, which supplies 5 volts to the cell phone for charging. Before doing any math, we have to realize that 500 milliamps is actually 1/2 amp. What you do is multiply volts by amps to determine watts. So, this should supply about 2.5 watts to the cell phone.

Compare that to your energy saving, 25 watt, spiral, fluorescent light bulb, and you can guess where this is headed.

However, the wall warts have heat losses in the transformer, and use more energy than they supply the phone. When tested at the wall outlet, my meter tells me it uses 28.9 milliamps while charging. Since the wall supplies us with 120 volts, we multiply the two, and get about 3.5 watts.

To calculate energy use, simply multiply power by time. If I charge this cell phone for 10,429 hours at 3.5 watts it will use 36.5 kilowatt-hours of energy. This is the same amount of energy in a gallon of gasoline. At least, that's what you will be billed for. The actual energy used is about 3.7 times that amount. In a previous installment of You Do The Math I used Department of Energy statistics to determine that the US's coal powered utilities as a whole are between 22% and 32% efficient, depending on the type of coal they use. (Interestingly, that's the same range as cars' and trucks' gasoline engines.)

If you take the average of 27%, this means that your utility probably uses 3.7 units of energy for every 1 unit you get out of your wall outlet. Take the 10,428 hours of cell phone charging, divide by 3.7, and we get 2,819 hours. This is how long it takes to use the same amount of energy in a gallon of gas.

Assuming your cell phone is similar, charging it for 7 hours a week (pretend you talk as much as your 13 year old daughter), it will take about 403 weeks, or about 7.75 years to use up a gallon of gas. If your squawk-box-for-a-daughter rides her bicycle 20 miles in the next 8 years, she made up for all her yappin, because she saved a gallon of gas.

Ah, but what about leaving it plugged in 24 hours a day? My charger uses 0.45 milli-amps when the phone is not attached. Multiply by 120 volts, and that's 0.054 watts. Divide 36.5 kilowatt-hours by 0.054 watts, divide by 3.7, and we get 182,683 hours.

What did you say? Yes, 182 THOUSAND hours. So, your daughter can leave a cell phone like this one plugged in for 7,612 days, or about 21 years, to equal a gallon of gas. By that time, you'll be worried about which junior high your daughter is planning to send your grand kids.

Some of you are asking, "What about my husband's huge cell phone that is essentially a hand held computer? Don't those use a lot more power?" I'm sure they do, since they play music, have lots of processing power, lots of memory, lots of internet surfing, and lots of video downloads. So, I tested a first generation iPhone that does all that, which went on the market in 2008.

When the wall charger was left in the wall, it used about 1.4 milliamps at 120 volts. That comes to 0.168 watts. So, it burns a gallon of gas' worth of energy in 58,719 hours, or about 6.7 years.

When actually charging, the iPhone averaged about 16.7 milliamps, a tic over 2 watts, which is actually less power than my little cell phone. For the sake of argument, if you charged the iPhone 7 hours a week, it would use a gallon of gas's worth of energy in 703 weeks, or about 13.5 years.

Seems like an energy hog. But, bear in mind the iPhone does what your desktop PC does. Yet, a modern, fast desktop burns energy 100 times faster than when an iPhone is actually charging. At that rate it uses a gallon of gas's worth of energy in 49.3 hours, or about 2.75 weeks if you use it 18 hours a week. Yet, even a coal-guzzling, desktop PC saves energy if it can spare you a drive in the car once every 2.75 weeks.

Compare the PC to the clothes dryer, which burns energy at a whopping 5000 watts. It uses a gallon of gas's energy in a mere 2 hours. So, if you use a clothes line to dry 2 loads of wash, you could leave your cell phone charger plugged in for 21 years. I think you better remove the green "Energy Star Compliant" sticker from your dryer.

Consider a 15 mpg van or large pickup truck that uses a gallon of gas in half an hour while city driving, as opposed to a 22 mpg car that would make that gallon last 45 minutes. At that rate, if you drove a car a couple days out of the year, and saved a gallon of gas, you could leave your cell phone charger plugged in 21 years.

If you ride a 50 mpg moped or motorcycle 50 miles, perhaps one day's worth of commuting, you can use about 2.3 gallons of gas less than the light truck, and that will allow you to leave your cell phone charger plugged in for 48 years.

I hope you get my point. To be environmentally conscious, don't sweat the small stuff, especially cell phones.


Karl said...

Thank you for the work you’ve done here. It is good to know that leaving my charger plugged in all the time isn’t a significant thing. It was getting to be a real pain plugging and unplugging it all the time. However, when I first heard the claim that cell phones contribute to global warming, I didn’t think of the chargers, I thought of the usage. There are other energy costs to cell phones than just the chargers and they should be addressed if we want to put to bed the claim that cell phones contribute to global warming. After all, which of us want to give up the wireless device on our hip or in our purse?

First off, have you found any information on how much electricity is consumed to actually use a cell phone or other wireless device? It has to be more than just the charging the phone was given the night before. After all, even if you are just texting someone across the room, it has to go through a relay tower and that must be a fairly sophisticated process. When I call my son in Wisconsin, it takes no longer for the system to find him than when he was living in my home here in Nevada and our cell phone numbers haven't changed. How much electricity is used in the process of finding that other phone and in maintaining the connection?

Also, what is the current estimate on how many devices are using this process at any given time? I would have to guess that, on the average in the USA, there are more phones in use than cars on the road. This accumulative total (chargers included) could be a lot of electricity being used equaling the effects of a lot of gallons of gasoline.

These are important questions to answer because the experts are saying that we are on the verge of the damage being irreparable. If this is the case, then anything we can do must be done. Even if it means giving up our wireless devices.


WoodHugger said...

Karl, you opened up a huge can of worms here... All I wanted was parents to un-ground their kids.

There are two other ways to figure out how much energy this service or that product uses. One way is to track heat. All energy used by humans ends up as heat.

So, if the cell phone towers in your city raise the temperature of your garage by 10 degrees the way your car does when you park it, then it's probably using the same energy as your car. Afterall, they transmit in microwaves, right?

Cars get tremendously hot while driving, and all this heat escapes into the atmosphere. Your home is hot, too, and all it's heat escapes constantly, at a sufficient rate that your furnace runs several minutes out of every hour.

Microwaves are the opposite. They transmit through the air, loosing a small percentage of their energy, and then are absorbed by solid or liquid objects, like houses, cars, trees, and lakes.

So, if cell phone towers used as much energy as cars, then the snow would be melted on the roadway, the way a tiny percentage of a car's energy ends up melting the snow in the right lane.

But, we know none of that happens. If cell phone towers did that, we wouldn't have Winters.

The other way to track energy is to follow the money trail.

How much money does a cell phone cost you? Perhaps $275 a year?

And what percentage of this $275 goes to energy? Probably a third, since labor and infrastructure account for a lot of a cell phone company's costs, especially Verizon, when they follow you around with a hundred workers.

But, ultimately a certain percentage of every dollar spent on labor and infrastructure also pays for energy. When the AT&T employee drives home, she gasses up her car using money she earned from your cell phone bill.

So, let's say that half of your $275 annual cell phone bill goes to energy. That's equal to 52 gallons of gas if you pay $2.64 per gallon. At 20 miles per gallon (close to the national average) those 52 gallons move you 1050 miles.

However, the average American drove 14,737 miles in 2005 (while people in rural states drove close to 20,000 miles a year). So, simply driving a car uses 14 times more energy than a cell phone's entire industrial support structure.

How about the auto industry? Buying a new car these days cost 100 times more than your annual cell phone bill. If your car lasts 10 years, then buying a car accounts for 10 times more energy than owning and operating a cell phone.

If You Do the Math, 14 plus 10 equals 24. So, using the money trail, cars use about 24 times more energy than cell phones.

Doesn't quite sound right to me. Afterall, my cell phones weigh 4 ounces, whereas cars weigh between 2000 and 4000 pounds. Pickups and SUV's and vans weigh between 3000 and 8000 pounds.

So my cousin's miniscule Honda Civic weighs 6000 times more than my cell phone, while my friend's Ford Excursion weighs 24,000 times more than my cell phone.

That's a lot of strip mining for iron, a lot of coal to melt that iron, a lot of truck and train usage to transport the coal, the iron, and the finished product to the showroom floor.

I'm willing to bet that the auto industry uses more of your purchasing dollar for energy than the cell phone industry. But, that's all speculation until we get those rascally accountants to talk.

Karl Cranford said...

Ingenious approach. I didn‘t think of it. Obviously, a little phone which only puts out milli watts of power can’t have much more effect on global warming than a lit match. But the towers that have the power to suck up that weak signal, boost it, send it on to the next tower and, if necessary, to a satellite do use a lot of power. However, finding information on-line about that cost is difficult. So, 52 gallons of gasoline annually per phone seems like a workable ESTIMATE.

According to Sprint, there are two hundred fifty million cell phones nation wide. Multiplying this by 52 gallons equals thirteen billion gallons of gasoline to power the cell phone industry annually. This is probably a small percent of our total energy consumption, but….

If the “global warming alarmists” are CORRECT, within ten years the damage to the global climate will be irreversible causing devastation comparable to “Day After” horror stories. This means driving a hybrid and changing some light bulbs isn‘t enough. It means the high polluting (high employing) industries such as auto, steel, coal, etc. must be closed down immediately. It means our life styles have to drastically change like giving up cars and cell phones. It means we need to give up a two inch minnow and turn the water back on to the crop land in California. It has to be more energy efficient to grow our food here than to ship it from China or Mexico.

However, if the “global warming alarmists” are WRONG and irreversible damage is not immanent, then we have time. So why are we wiping out industries when our economy needs them most. Why are we buying CFL bulbs that are made in China by factories that pollute the ecosystem and the food they send us? We could still be buying bulbs that are safely made here in the US feeding our own suffering economy.

Perhaps your blog isn’t the appropriate place to raise these questions, but they seem central to the global warming issue and you seem like a person who could shed some light on them for me and others. I’m sure math is involved in their answers somehow. We should take care of our environment, this is a no brainer. However, the US seems to be the only country doing so and if the alarmists are RIGHT, its too little too late. If they are WRONG, then why are we devastating our national economy when there are other ways of handling it? We and the kids can talk all we want on our cell phones.

WoodHugger said...

I understand your dilemma, it's a tough choice. But, we can kill two birds with one stone. (So to speak.)

Personally, the only reason I'm against global warming is because I'm against fossil fuels. I'm against fossil fuels because of they contain things like mercury and thorium, a radioactive element.

The amount of mercury pumped into our atmosphere each year by the US is staggering, and China does the same. It's measured in tons. See the blog below on Mercury and Compact Florescent Lights.

One CFL actually REDUCES mercury pollution by more than 70%, even though each CFL has 5 milligrams of mercury in it.

WoodHugger said...

It's funny how the liberals, anarchists and anti-Americans think the US is the only country NOT doing anything about carbon emissions, while you think we are the only country that IS doing something about it.

In some ways, you're both right. Sure, we ARE doing a little to reduce emissions, and so is Europe, but developing countries such as China and India are not.

However, the US still pukes 20% of the world's carbon emissions, while we make up only 5% of the world's population. Mathematically, we produce 4 times more emissions per capita than people in other countries, so we each need to do 4 times more to reduce emissions.

Unless, of course, you don't think that the 38% increase in CO2 since the dawn of the industrial revolution is a man made phenomenon. It's just coincidence. Even though it's never happened this fast in recorded geological history going back billions of years.

Or you think the geologists are are full of it, which many of you do.

Or you think there is NO global warming, which many of you do.

Or you think global warming is good, and the Earth will be tropical from pole to pole. (See my first blog on that prediction.)

But, whatever, the problem will take care of itself.

True Communists? They don't have a big enough GDP to pollute.

Socialists? They make laws to reduce carbon emissions. And have less GDP than capitalists.

Capitalists? They will eventually use less carbon because it will eventually save money, as energy costs go up as China and India use their fair share, which they are rapidly approaching.

Fake Communists? Like China. Same as capitalists.

But, very soon, the human race will be using a heck of a lot more energy per capita than they are now. And carbon emission will skyrocket. So, we get to see who was right, the scientists or the skeptics.

How do I know this? Energy production keeps going up. That's the only thing you really need to look at.

WoodHugger said...

Oh, and another thing. Oceanographers have found enough methane on the bottom of the oceans (locked in ice) to power the human race for thousands (or hundreds) of years.

And, as it is "mined", it will be used, mostly because it's much cleaner than fossil fuels.

And, as it is used, it produces CO2. So, the future is hot!