Electric Cars

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Electric Cars

Electric Cars. Are they really all they are hyped up to be? The short answer: hell yeah. These things are sweet. I want to get my hands on one right now.

Energy flows in the US.

Energy flows in the US. Transportation accounts for 28% of all energy use, primarily from burning petroleum. 

35% of US energy consumption is in transportation. Transportation requires that the energy source be within the vehicle (unless you are in South Korea, where the energy source is induction and is beneath the road. Pretty badass, if you ask me). Batteries currently weigh a lot, don't have nearly as much energy per pound as gasoline, and require a long time to charge. But if we could replace a huge percent of this with more efficient electric cars, it would go a long ways towards arresting GHG emissions.  

120 million Americans commute to work by car. The average person lives fewer than 20 miles from work. Substantially all of them commute alone. The Nissan Leaf gets 75 miles before it needs to be recharged. The Tesla model S goes about 275 miles. No matter what the source of energy for an electric car, it produces less CO2 than a normal car.

How does an electric car produce less CO2 than a gas one? No matter the source of the electricity, even if it is an old inefficient coal plant, the conversion efficiency of an electric car will result in lower CO2 emissions per mile than a gas powered car. The EPA estimates that the Nissan Leaf gets an estimated 125mpg using CO2 equivalent of gasoline. The recent fleet average for the US is about 30mpg for passenger cars. So electric cars emit only 25% the CO2 of your average normal car. Lets be generous and say they emit 40% the CO2 of your best gasoline powered cars.

Commuters would make a very significant difference in emissions if they changed over to electric cars.

Power

Most Americans base the acceleration needs of their car on the idea that they someday need to accelerate down on onramp to get to 65mph on the highway. The amount of power a car has is typically listed as horsepower (hp). This is a terrible measure. The real measure of power of a vehicle is Peak Torque.

Allow me to explain this concept. Roughly speaking, torque is the force going into a rotation of an object. It makes sense to use torque to describe cars, cause they have rotation parts. Think of it as the amount of energy going into the car from the tires rotating on the road.

(yes, that is a cross product) where r is the radius, or distance from the center of rotation, and F is the force. For the most part, the torque of a vehicle is entirely determined by its engine. It directly translates to how fast you can accelerate. More torque yields less time from zero to 60.

My motorcycle. Pretty, eh?

Let's compare some examples. First,  my favorite. My bike, a Kawasaki VN750, vs. a Hayabusa (fastest production bike in the world) and an electric bike from Zero Motorcycles, the Zero DS. The electric motorcycle gets up to the equivalent of 400mpg. Compare to a normal bike of around 40-50mpg.

VN750 Hayabusa DS-electric
Style Cruiser Sport Sort of cruiser
Weight 500 lbs 563 lbs 400 lbs
Torque (ft-lbs) 47 99.6 
69

Before comparing, let's talk about peak torque. Peak torque is the maximum torque an engine can put out. For a gasoline engine, it is pretty much right before it redlines. So the numbers of 47 and 99.6 you see for the first two bikes means that it is the best they can do. You can think of an electric motor as pretty much always putting out peak torque. In other words, the hayabusa has to jump up to 6500rpm before it can be at full power, then it shifts up a gear, and drops back down out of its full power range. The electric bike doesn't shift gears, either.

Let's look at the Hayabusa power band to illustrate this difference.

Hayabusa power band in yellow. It is not a flat line.

As you can see, the torque output of a gas engine changes with RPM. You will notice the Kawasaki ZX-14 has more max torque, but less torque at the lower end. This is one of the main reasons the 'Busa is considered faster. It comes off the line far faster than other bikes, cause it has higher starting torque. Compare this to an electric engine, which has max torque from 0 RPMs up. You probably see my point about how sweet electric engines are.

So now we can compare electric vs gas based on torque. The electric motorcycle trounces my motorcycle all the time. In the first few moments, it will likely nearly match the Hayabusa. In fact, until the 'Busa hits 3000 RPM, the electric bike won't look too shabby. Why? First, cause it has the same torque as the 'Busa up til the Busa hits 3000rpm. Second, cause it weighs 150 lbs. less. In short, a smaller electric bike kicks butt. (note that the electric bike doesn't have super wide tires to accommodate all its power, so it might slide around a bit when you hammer down).

Where does the electric bike fall short? Range. This bad boy will only go 75 miles on the highway between charges. Funny enough, it'll go 125 in the city. This is all owed to wind resistance.  Back to the point, you can't refill this guy as easily. You need to plug it in. It takes a while to recharge. You can just fill up a motorcycle and go on your way. This bike is pretty much for commuting or visiting friends in nearby cities.

(*2017 update! New electric motorcycles are capable of going 200 miles. Then they have to recharge for a long time. But 200 miles is a long trip).

Also, let's admit it, both my bike and the 'Busa are sexier.

The cars.

Audi A5 Nissan Leaf Tesla S
Cost $38k $21.3k 62,000
MPG 22 102 90
Peak Torque 258 210 443
Weight (lbs) 3549 3354 4650
Range (miles) unlimited 75 275

As you can see, if you are commuting the Nissan leaf makes a lot more sense in every possible way. It costs less to buy than most cars, it has the acceleration potential of a high-end Audi A-5, and the range you need to get to work and back. This beast will accelerate onto the highway just fine. Also, there is the whole power band thing. These electric cars have peak torque all the time.

Overview

Electric vehicles. These puppies accelerate as fast or faster than most vehicles in their class. The shorter range ones are less expensive to buy than most cars, and the cost of making them move is lower. Oh, and they save the environment relative to normal cars.

Whats the drawback? Range anxiety: the other event people think of when they don't want an electric car. Visiting Grandma. People want to buy one vehicle that can do everything they want. There is also the concern of "what if I am in an emergency and really need a car that can drive far right away?!?" How many times has that happened to you in your life? For me, the answer is 0. Any family emergency I had, I took a plane or a bus to.

Most families still own two cars. At least one should be electric. Here's an idea: get one gasoline car to visit grandma when you need, and then get an electric for your commute. Here's another idea: get an electric car or two, and rent a car when you need to go visit Grandma. You will save money either way.

The ridiculousness that is trucks and SUVs? Get a subaru with a roof rack, and rent the trucks and SUVs otherwise. Why the heck are you in a vehicle getting 12 miles to the gallon when gas is expensive, and when burning that gas helps wreck the environment? You, person who commutes to work in a pickup, are a selfish person.

Grid Stabilization

In the Solar and Wind articles, we read that these technologies produce intermittent power. In other words, they can't provide power on demand or at night. Imagine, if you will, that those 120,000,000 commuters all had electric cars. And that they all had excess batter capacity. They could charge up while the wind was blowing and the sun was shining, and discharge while the sun was sleeping and while the wind was lazy. Suddenly part of the problem with wind and solar has some help. This is a huge topic, though, and I won't go farther into it.

Shortest version:

Get an electric car for your commute.

Hokay, that is all for now. I will edit this as I get comments. Thanks for reading!

Jason Munster

Geoengineering

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So. Science can fix anything, right? Only if we have lots of time and money. And grad students that function as indentured servants in a pyramid scheme to get tenure.

Back to the point. The truth is that science can't fix everything on short time scales. Climate is one of them. Geoengineering can help to a degree, but it will only get us part of the way there to avoid the worst consequences of climate change. Let's discuss some.

White roofs, white roads, white buildings.

Two articles back, we discussed albedo, or reflecting sunlight. Ice reflects 90%, water reflects 90%. Whatever is reflected tends to go to space and not stay in the Earth system and warm it up. In fact, whatever is absorbed then gets in the greenhouse trapping loop, warming up the Earth a good bit. Dark surfaces (our roofs, our roads, most of our buildings) reflect little and absorb a lot. So, paint them all white, and more light is reflected. Excellent!

"But Jason," you say, "Cities are only a small percentage of land area. How could this possibly help? I mean, the rest of the Earth will still absorb just as much heat. Right?"

And to you I say, "Excellent, sir! That is true. Making all our stuff white won't do much for the overall heat budget of the Earth. I am so proud of you for reading most of my website so you quickly figure stuff like that out."

So what does it do?

 

The heat island effect is based on the fact that cities are covered in dark buildings and pavement, and have a very low albedo, so they absorb heat

Cities are fucking warm. They suffer from this thing called the "heat island effect." That is a fancy way of saying that they are so dark, they absorb the sunlight and are easily 10 degrees F (around 5 degrees C) warmer than they should be. Turn everything white, and you can cool the city. This will actually have a very large effect on how hard our AC units have to work in the summer. Imagine if your city was suddenly 10 degrees F cooler. How sweet would that be? I posit that it would be pretty rad.

This one seems to help a bit, but we will still be using tons of energy and producing CO2 in all other ways. Moreover, it won't solve the problem of the agriculture, ice caps, and acidifying ocean.

Putting CO2 in the ground

There are two ideas of sequestering CO2 in the ground. The first is capturing it at the source. Like power plants. This sounds like an easy idea, but the first problem is the energy it takes to capture it. Thermal power plants take in atmospheric air. Which is 78% nitrogen, and 21% O2. Even if all the O2 were converted to CO2, what comes out of the power plant stack is still 78% nitrogen. Separating the two to store the CO2 takes more energy. In fact, the power plant is roughly 30% less efficient. So it needs to burn a lot more coal or natural gas to produce the same amount of power, and will cost a lot more to build. And any fancy idea you have to get around this 30% efficiency hit won't work. No matter what, you either have to pre-concentrate O2 to get a pure stream of CO2 on the other side, or separate the CO2 on the emission side.

The next problem is where to store it once you get it. Gases like to leak out of things. Some companies are trying to store the CO2 underground, much like petroleum is stored underground in a lot of places. This is why you need to separate it from the nitrogen in the air. There just isn't enough space to store both the CO2 and the nitrogen, and also it is expensive to pump stuff underground. Another issue is that it is unclear how long storing CO2 will last in the ground, since it more or less needs to be done indefininately.

Finally, since 35% of our energy use is from cars driving down the road, and it is impossible to capture that CO2. So Carbon Capture and Storage (CCS) from the source still won't do everything we need.

Direct Capture
The next idea is to capture CO2 directly from the air. We have increased CO2 in the atmosphere from 280 parts per million (.028%) 400ppm. The idea of direct capture is to do the opposite. Draw down the CO2 and then store it somewhere. Some might suggest we store it in trees, but that is an awful lot of trees, and unless we bury them trees somewhere underground, they are just gonna get consumed by bacteria and become CO2 again. Other options are to mechanically and chemically separate CO2 from the air, and them store it underground as above. This is very expensive. It might work in the future, but for now it won't.

The bonus of this, if it ever works, is that it is the best way to reverse our issues from an engineering standpoint. We can turn back the clock.

Stratospheric Injection

Injecting small sulfur or other particles into the atmosphere cools the entire globe by reflecting some small portion of sunlight before it hits the rest of the Earth. We know this cause when mountains like Pinatubo and St. Helens explode, they launch particles into the stratosphere and we get a cold year.

SO2 increase in the stratosphere by exploding volcano

Some people have suggested that we could do this. Just inject stuff into the stratosphere to reflect sunlight. The problem? It turns out that everything small enough to cause the proper scattering just happens to be the right size to promote adsorption of water particles. Which then allows for rapid recycling of CFCs in the stratosphere.

"But Jason," you say, "I thought recycling was good!"

Recycling plastics is good. Stratospheric recycling of CFCs is bad. Cause what happens is a CFC reacts with ozone, breaking it apart, wrecking the ozone layer, and then usually is all like, "Man, I am exhausted from catalyzing that reaction, I am gonna take a break." But that water that adsorbed onto our reflective particle provides an excellent place for it to re-radicalize. Which means it is ready to take out another Ozone particle. That's right, our CFC goes to chill out on some water droplets, effectively taking a restful timeout at a pool, and gets ready for work again destroying the ozone layer.

Let's pull this all back together. We try to put stuff in the upper stratosphere, if could make CFCs more effective at destroying the ozone layer, and then we are all screwed in a much much larger way than climate change. Cause the ozone layer is what protects us from getting fried by a lot of UV rays.

Here's where things get fun. Imagine you are a small country of 1 million people living on an island. And that island is going to get inundated with water in 20 years unless climate change is reversed. You don't give a damn about a chance of destroying the ozone layer. You only care about saving your people and your country. Stratospheric injection isn't exactly nuclear science. We aren't going to have rogue nations stumbling through how to do this, and failing all the time.

I'll leave you to ponder what all that means, cause it is more fun that way, and we are already at 1200 words.

The upshot of this is that it also fails to solve the acidifying of the ocean, we don't know how well it will work, and we don't know what will go wrong.

Solar Reflector

Another idea is to put huge mirrors in space and reflect a chunk of the sunlight coming in. This could work. Wasn't this a plot in some Bond movie, though? Also, it would be mad expensive. Probably much more expensive than some other options. And much like the option directly above, we still acidify the ocean.

Review

Hokay, so. Most of the technologies for fixing our problem don't exist, don't work, are too expensive, or could kill us all. And if they do work in the future, they won't solve all the problems we are creating. Even the one that does solve all the problems, direct capture from the atmosphere, won't do crap for our plight if we rely on that alone. As a species, we can easily outstrip any CO2 removal measures just by burning more things. Even if after rigorous testing proved all these work, we would need to some combination together to get anywhere. And even with that, we need to reduce the continued growth of emissions worldwide, otherwise no science or engineering solution will stop climate change.

Depressing, eh?

Thanks for reading,

- Jason Munster

Climate Change 2

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I am not expert on different effects of climate change. But I do know a good smattering of random things. More importantly, several of my coworkers in grad school are at the forefront of the research of a lot of things here.

Here are some events relating to climate change, with indications of how much I think I know about it. So, for these things, I will have a title, than a 5 star rating for my level of confidence in the material I am presenting. 5/5 means I think I know a whole lot, 4/5 means I know what a grad student in a related field should know, and I probably am friends with one of the experts in the field, 3/5 means I am conversant in it, 2/5 means I understand it a little and have seen the math, 1/5 means I have heard of it and think it is worth mentioning.  It is important to note that anything rated 1 or 2 should be taken with a grain of salt, and should absolutely not be cited. I don't really know much about these things, other than they are possible.

Melting Ice Sheets -  3/5

A snapshot of the Arctic sea ice extent from June 2013. Area of sea ice has decreased over time

A snapshot of the Arctic sea ice extent from June 2013. Area of sea ice has decreased over time

It seems like every summer, the news programs get all abuzz over the Arctic ice extent. No matter which way it goes, they get excited. The extent is literally the surface area that this ice covers. But as we discussed on an early post about thermodynamics, the amount of heat energy you have to pump into a system does not relate to its surface area, but instead to its volume, since volume is directly related to mass. And the story of ice volume yearly minimum is more telling: the minimum ice volume in the summer has decreased by a factor of nearly 50% over the past 5 years. In other words, half of the summer ice is gone.

The areal extent of ice seems somewhat erratic. The volume measurement of arctic ice over the last 5 years is a much more important measurement

What happens when the ice goes away?

Albedo changes - everyone knows about this, so I won't rate my knowledge here. In the last post, I mentioned that ice reflects 90% of light energy, and water absorbs 90%. If the sea ice disappears, more heat can be absorbed and trapped by the Earth, causing warming to happen more quickly.

Shortwave radiation is high-energy radiation from the sun. Longwave is infrared that comes off from Earth. Ice reflects shortwave (sun) radiation.

Stronger temperature changes in high latitudes

As the planet warms, the warming will be more felt in the high latitudes (ie the Arctic and Antarctic). As you can guess, this will have feedbacks with the ice melting and albedo changes.

Projected temperature increases show that the high latitudes will have far more profound temperature increases under climate change.

The habitats of the Arctic will present another positive feedback - 5/5

This is what I study directly. I don't model this, I measure it. Well, my team does. I am a small part of that. In normal biomes, plants pull CO2 from the atmosphere and turn it into plant matter. A lot of this is leaves or grass and such. They then die, fall to the ground, and get consumed by bacteria or oxidized to become CO2 again. So most of the CO2 consumed by plants and such is recycled back into the atmosphere.

In cold places, it is different. Moss and grass grow in the summer (no trees, permafrost prevents them from ever taking root). Much of this after it dies does not get recycled to CO2 again,cause the freeze already happened and it is too cold for the stuff to become CO2. This has happened in the Arctic for 300,000 years or more. In the first 3 meters of Arctic soil, there is enough undigested carbon to double the amount of CO2 in the atmosphere. Obviously it won't all release at once, and most of it may not release. But even if a part of a percent started being released per year, it would match mankind's CO2 emissions. This hasn't started happening yet, but if it did, we'd want to work fast to reverse it if we hope to prevent climate change from jumping into a strong positive feedback loop that we cannot control.

More on this later, when I describe my actual research and what I do day to day.

Weather patterns change - 1/5

I can barely even hand-wave at this one. The ocean strongly influences atmospheric circulation patterns. Hurricanes, for instance, always form over the ocean. This is because the ocean has a ton of thermal momentum (it doesn't change temperature at the same rate as the atmosphere) and the top layer of it is well-mixed, so even if the top few inches warm up, it will rapidly be cooled off by the water beneath. The atmosphere has much less thermal momentum, mostly because it is far less dense than water. So what happens when you have an ice cap? The water-atmosphere interaction is cut off. The water is sealed away from the atmosphere, and suddenly the ocean stops controlling wind patterns and such. And then very large-scale atmosphere-driven wind patterns can develop without ocean waters impeding it. This leads to wacky weather. Like increased snow in winter at mid-latitudes, and much more variable weather. This is why we now call it climate change instead of global warming. Some places will get cooler, but the variability of weather patterns will increase because of this sort of event. Like in Boston on May 2th where we broke the record low, and then on may 29th we broke the record high. Yay more climate variability.

Drought in the US. Much of the west coast is short of water.

Drought in the US. Much of the west coast is short of water.

In addition to weather variability, some trends will be more pronounced. Dry seasons will be more dry and last longer. Rainy seasons will have more intense storms. This can be a problem, cause droughts prevent agriculture from working.

Which leads to:

Increases in Floods and Droughts - 2/5

There are floods called 100-year floods, cause they should only happen once every 100 years. Areas of Australia had two 100-year floods in a decade. This is because climate change will make large weather events, like floods and droughts, a lot more frequent.

Torrential rains flood Australia pretty frequently these days. Expect more of this in many parts of the world as climate change takes hold.

Melting Glaciers 4/5 (I hang out with the world experts on this all the time, cause they are cool)

Did you know that everything with mass exerts a gravitational force. Yes, hard to believe, but it is true! And it turns out that mountains and glaciers exert a sideways gravitational force. One that is strong enough to pull water from the oceans towards them. In other words, if the Greenland ice sheet melts, the sea level Greenland would actually drop. And the sea level around India, Africa, and South America would rise a more than you would expect. So instead of seeing 7m of sea level rise from all of Greenland melting, they might see 8m. In other words, all the poor countries that didn't put the GHGs in the atmosphere, and also cannot afford to prepare for the rise, will take the brunt of this one.

Disease - 1/5

Many people predict that certain diseases will become more rampant. Like how trees are getting destroyed all over California, because certain tree-eating bacterias and insects can survive in the slightly warmer weather. More trees and plants will die, yes. The disease part is a bit questionable how it will work. Diseases of many times will shift where they work, but it won't necessarily expand it. But just think about how much fun most of my readers (predominantly American) will have if Malaria creeps north into a bunch of our states. Overall, though, the jury is still out on this one.

Food Production difficulties - 2/5

Many staple grains, like corn and wheat, won't grow as easily if the temperature rises even 2 or 3 C. The world food supply could easily run short, especially with the combination of increasing population from 7 to 9 billion over the next 40 years or so, and the fact that as much of the world gets wealthier, they want more meat. Why is the meat thing an issue? It takes about 40 lbs. of grains and such to make 1 lbs. of cow meat. For pigs, it is much better, with a ratio of about 8. Cause pigs are excellent at turning calories into food for us. Yet another reason to like bacon, eh?

Anyways, food supplies will become more strained. It could be a very serious issue. People might fight over it. By people, I mean countries.

Also interesting, I sometimes brew beer with a guy who is one of the experts on this.

Wrapping up

I have only touched on a few things here. As more come up, I will update this post and tell people to check it out. Before leaving, let's review some of this stuff.

Wealthy countries by and large have pushed a ton of greenhouse gases into the atmosphere. It is causing climate change. Because of how gravity and glaciers work, climate change is going to effect predominantly Southern hemisphere countries. In other words, South America, Africa, areas around India, etc. Pretty much, it is going to have a more profound effect on the countries that can't afford to build walls around their cities to hold back water, and can't throw money and science at the problems as easily. Climate change already punishes poor countries cause they cannot afford to deal with the changes, but the melting glaciers problem exacerbates their situation.

One great example: If emissions of greenhouse gases are not somewhat arrested and sea level rises 1m, at least 17 million people in Bangladesh will find themselves inundated. Where are they going to go? They are surrounded by an ocean, India, Burma, and a whole slew of mountains called the Tibetan Plateau (think Himalayan mountains). India doesn't want them, they are already crowded. Burma is rather hostile. Sending 17 million climate refugees anywhere is likely to cause a problem. And that is just one country.

Hokay, that was depressing to write. To end on a cheery note, climate change will make the weather in both Canada and Siberia much nicer. Also, when the ice caps melt in the Arctic, international trade will have all new sorts of inexpensive ways to move around! This will prove useful.

Oh, one the thing.

The Arctic has a ton of resources that can be mined / produced. So when that ice melts, there will be a wealth a resources. And probably a lot of fighting over said resources.

Thanks for reading!

- Jason Munster

Climate Change

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So here it is. The post on how climate change works. Today, we return to Math!

*added later: thanks to the friends who noticed typos and order of magnitude errors, and prompted me to correct them

** Comments section has been opened up.

Climate Change

Some people say that the amount of CO2 in the atmosphere is so small that it couldn't possibly do anything. They say this because if you take one million random molecules in the atmosphere, only 400 of them are CO2. Seen another way, oxygen is 21% of the atmosphere, and CO2 is .04% (It was .028% before we got started playing with things. So we raised the % of CO2 by .01)

People who believe a small perturbation cannot change a complex system are in denial. Complex systems, like the climate or our bodies, respond to some inputs very strongly. As dumb as this comparison is, lets consider a poison introduced to your body. Let's say you weigh 50kg (a little more than 100 lbs). 0.01% (this is how much we changed CO2 by) of your body weight is .005kg, or 5000mg. A lethal dose of cyanide in a human is about 1.5mg per kg of weight. For a 50kg person, this is of 75mg. 5000mg of cyanide would be overkill.

It may seem drastic to compare CO2 in the atmosphere to cyanide in the body. One causes warming in the atmosphere (at least scientists argue that), the other causes death of a single person. It may actually be somewhat an apt comparison. Without warming caused by greenhouse gases, life as we know it would not exist on Earth.

Maths!

Here I will show that without greenhouse gases, the Earth would be a frozen wasteland. CO2 and other gases trap heat, more or less preventing heat given off from the Earth from escaping by reflecting back on itself.

The heat on the Earth's surface and in its atmosphere has one major input, and one major output. The input is solar energy (we call it solar radiation. Not the same type of radiation that uranium has when it goes through a radioactive decay.). The output is radiation that the Earth gives off. As the Earth heats up, it gives off more radiation. The output of heat from the Earth needs to match the input of heat from the sun, otherwise it heats up or cools off. If the output of heat drops and the input of heat remains the same (say, for instance, that greenhouse gases prevent output of heat by trapping some of it), then the planet will retain heat until it is so warm that it gives off enough energy to again have an output that is equal to the input.

Schematic of how greenhouse gases trap and reflect heat from the Earth, preventing it from being released once it is absorbed.

Let's start from the basics, the energy emitted from the sun. If you want to take my word for this, you can skip to earth temperature calculation part

The energy emitted by the sun is based on its surface temperature. In fact, it is the surface temperature related to the 4th power (the reasons for this lie in quantum mechanics. If you are feeling smart, brave, or arrogant about your smarts, follow that link to find out why it is T^4).

Our sun puts out energy in many different wavelengths

Here, R is the radius of the sun, and is the stefan-boltzmann constant used specifically for blackbody radiation: . The surface temperature of the sun is 5800K.

So this is how much energy is emitted in total by the sun:

emitted by the sun.

What fraction of this hits Earth? Let's call is for flux of energy to the surface of the Earth.

where d is the distance between the sun and Earth()

Satellite observations show the actual value is closer to 1370. So our very basic theory shows us correct within 1.5%. So far so good, as far as this basic math model goes.

So, at the equator, we get 1370 watts for every square meter of land. As you move poleward, this amount decreases by roughly a factor of cosine.

Earth's Temperature

Hokay, so before we had an equation with in it. We can get Earth's equilibrium temperature by doing all this process in reverse. One important thing to consider: not all of this light reaches the ground. A lot is reflected. White snow, for instance, reflects about 90% of light. Water absorbs about 90% of light. The factor of reflection is called albedo (we will call this A in our equations). Overall, the current albedo for Earth is about .28. In other words, 28% of light is reflected back to space.

This is kinda how albedo works

Hokay, so light hits the Earth. It hits 1/2 of the Earth, which is a globe. So the light lands on the surface, which for a globe is roughly a circle. A circle with the radius of the Earth,

So the mean solar radiation absorbed by the Earth is:

We can approximate the black-body temperature of the Earth to be equal to this. So

whereis the temperature of the Earth

substitute numbers in:

Note, Kelvin is just celsius temperature, except 0 kelvin is absolute zero, the coldest possible temperature in our universe. 0 kelvin is roughly -273 C. So 256 K is 17 degrees below 0C. Let me emphasize that.

From a strict radiative standpoint, the surface temperature of the Earth should be at the very warmest 17 degrees celsius below freezing.

Did we do something wrong? Nope. We forgot one very important factor. Greenhouse gases trap heat. Without CO2 and methane and water (yes, water traps heat) in our atmosphere, the Earth would be frozen solid, and there would be no life, at least not on the surface. Even the oceans would be frozen over.

How greenhouse gases absorb and trap heat

A CO2 molecule has a C in the center and two oxygens hanging off it. When light of a certain wavelength hits it, those two oxygens start vibrating faster and get excited. Which means the light was absorbed and converted to heat. It turns out that the temperature of the Earth is such that the bulk of light it emits is a wavelength that things like CO2 and H2O and CH4 can absorb. They are heated up. If this happens all over the place, the entire atmosphere heats up. And then, since everything emits light based on its heat, the CO2 molecules release some of this energy as light, again in infrared, and it has a chance of being re-absorbed by another molecule. Eventually some of these photons (the light energy) escape the Earth.

So, now we have to change our equilibrium temperature equation to have a greenhouse forcing:

where f is the greenhouse forcing factor.

I am not going to run through this, cause everyone gets my point. Going back to our analogy, these tiny amounts of CO2 and other gases in the atmosphere make our planet livable by increasing the temperature. And the more we pump into the atmosphere, the more the atmosphere and surface of the Earth will heat up. In short, climate change is real, and it is caused by people.

Here we have CO2 concentrations over the past 400,000 years plotted against temperature. These can be derived with reasonably accuracy directly from air bubbles in ice cores that are up to 700,000 years old, or inferred from isotope ratios of oxygen (another story, another time)

Here is more recent data, with direct measurements. Yes, the axes are scaled to make the correlation stand out. The point is that the correlation between rising CO2 and temperature exists. CO2 goes up, then temperature goes up.

Here is more recent data, with direct measurements. Yes, the axes are scaled to make the correlation stand out. The point is that the correlation between rising CO2 and temperature exists. CO2 goes up, then temperature goes up.

At this point, it should be clear how important CO2 and other greenhouse gases are, and how changing GHGs by a small amount can make some pretty big changes in the complex Earth system. These conclusions are rooted in science. It's the same science that makes cars work. Anyone who believe in cars should also believe in GHGs causing climate change.

Some effects of climate change

We all have heard of sea level rise. Most people think the primary cause of all the sea level rise we have seen over the last century (about an inch every 15 years) is melting glaciers. This is untrue for most of the sea level rise of the last century. What causes it, then? Water is most dense at 4 degrees celsius. If it moves in either direction away from this, it begins to expand (as ice in one direction, as water in the other). Thermal expansion of water has caused much of the sea level rise we have seen.

Sea ice melting doesn't raise sea level at all. Because the ice contracts when it becomes water. In short, sea ice doesn't displace water. Those melting arctic ice caps aren't going to change the sea level much from melting alone* (we will get back to this later).

Melting glaciers, on the other hand, will make a difference in the future. That is water that has been removed from the ocean and placed on mountains. When it comes off those mountains, it flows to the ocean. It is estimated that the Greenland ice sheet has about 7m of sea level rise worth of water, or about 20 feet. Most of Florida would be gone in this case. NYC, Shanghai, many European cities, Vancouver, DC, Boston, etc., will be underwater. No one really knows what timescale this melting will occur at. We will cover this more in depth in another article. These may have already started to go. The average annual sea level rise for most of last century was about 1.7mm/year. In the past decade, it has doubled to about 3.4mm a year. The Greenland ice sheet has definitely been melting in recent years. It is unclear how fast this will unfold. More on that later.

*Melting Arctic ice: remember when I said that snow reflects 90% of light energy, and water absorbs 90%? What happens when we melt ice caps, then? More of the light that hits that area will be absorbed. So let's recap here. The Earth heats up. The ice caps melt, exposing water, which absorbs more light, making the Earth heat up more. This is what you call a positive feedback mechanism. It is not "positive" in that it good. Positive means that it has an accelerating effect. Normal people call this a self-perpetuating cycle. Some people call it a "vicious cycle." But we are going to call it a positive feedback mechanism, and know that in this case, it is a bad thing.

** A colleague mentioned that I should also talk about the water vapor feedback, since it is often a tool used by climate skeptics. Water vapor is a very strong greenhouse gas. When the temperature rises, more water vapor goes into the atmosphere, which can in turn raise temperature more. It sounds like a permanent positive feedback mechanism, but it has stark limits if it acts alone. But when you put CO2 into the atmosphere, it causes warming, and then causes more water vapor. In this case, we can say that water vapor amplifies CO2 greenhouse forcing. Again, the additional water vapor warming from CO2 atmospheric load increase is limited, but NASA and later studies show that in some places, the effect of water vapor can amplify the greenhouse forcing of CO2 by a factor of 2. While the theory is not perfectly understood, the observations (areas with high water vs. low water, accounting for all other types of forcing) are very good.

And now we have exceeded 2000 words.

-Jason Munster

Other Alternatives

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Here we will cover a few more electricity producing alternatives, specifically geothermal in its different flavors, and the waste of money that is tidal power. Before that, let's make a quick roadmap of what we have covered, where that is going, and what we haven't yet covered.

Pretty much, we have talked about electricity producing resources. We have only briefly touched on energy as a whole. In the US, for example, 35% of all energy use is petroleum for transportation. None of the stuff we have discussed is useful to replace that without better battery technology. Nonetheless, it is likely that at some point in the next century, much of our domestic energy needs, including transport, will be covered by electricity. And we will require a lot more of it. An upcoming post will assess all the different tech for producing energy we have discussed, and which ones can be potential solutions.

Geothermal

Geothermal energy exists because it gets hot underground. In general, the temperature of the Earth rises by 30 degrees C for every km you go underground. This temperature increase in depth is called the geothermal gradient. If you go 7km underground, you are pretty much guaranteed temperatures of higher than 200 degrees C. Which, as we all know, is hot enough to boil water. 7km underground is pretty deep, however. In some places, the underground is much hotter. The temperature rises much more rapidly. It could be due to volcanic activity in the area, or radioactive decay underground. Either way, when hot temperatures are closer to the surface, that heat can be harnessed to drive a turbine.

Map of the geothermal resources available in the US. In general, this represents areas of higher temperature gradients.

Geothermal comes in two main flavors. One directly harnesses the steam from the ground to produce electricity (called flash steam, cause the pressurized hot water comes out, flashes to steam at atmospheric pressure, and drives a turbine), the other uses a heat-transfer mechanism where pressurized hot water from the subsurface (it needs to be pressurized, because it is above the boiling point of water at atmospheric pressure) is run through a set of heat-exchanging pipes before being put back underground. There is a third type discussed later in the article called hot dry rock.

Surprisingly, the first mechanism of directly using steam, in practice, is unsustainable and produces pollution. This is because the used steam is often vented to the atmosphere. The steam produced underground has pollutants. Like CO2 and sulfur, amongst other things. If the steam is used directly in a turbine and then expelled to the atmosphere, these pollutants come with it. If the used steam is instead re-injected into the formation, this problem is avoided.

Reinjecting the steam is easier and more common in the heat-exchange mechanism. The super heated stream of steam from underground is already isolated, and re-injection is pretty simple.

And here comes the fun part. If the steam is used and then vented rather than reinjected, the formation will run out of water. Instead of being a renewable resource, the geothermal will be a depletable resource that will only last for 10 or 20 years. This is because the pressure of the formation will drop, and the steam will no longer be able to rise. Does this sound familiar? Oil and gas production need to do this all the time to get maximum recovery rates. Reinjection of fluids is rather easy, and has been pretty well developed by the oil and gas industry.

Hot Dry Rock

The next major innovation takes a cue from the oil and gas industry. Hot dry rock is exactly what it sounds like. The rock starts off hot and dry. It has plenty of heat in it, but there is no steam or water to produce and then make energy from. How is this dealt with? Hydrofracking and injection. A well is drilled, the drill hole goes horizontal, it is fracked to drastically increase the surface area that the well hole can be exposed to, and water is injected into the rock. The water heats up a lot, then it is produced via a separate well to make steam. It is fairly complicated, and costs a lot more.

EGS

EGS stands for enhanced geothermal systems. You will run across this term a lot these days. It more or less means that the heat in the field is managed by either fracking beforehand, injecting water afterwards to maintain pressure in the field and extend the life of the geothermal power plant, or a combination of both. It drastically increases the lifetime and viability of a geothermal site.

Cost

The capital costs of geothermal pretty much will dictate the average cost of electricity produced. It looks like flashed steam will cost the least. In reality, unless the steam is reinjected afterwards, the field won't last as long, and the capital investment costs will have to be paid out over a shorter period of time, resulting in higher costs. Hot dry rock will undoubtedly always remain more expensive because of the costs associated with fracking and reinjection.

Footprint and other

Most of our power plants produce heat above ground, and need storage for either spent nuclear fuel or a coal pile (except for gas plants. They just need pipelines). So geothermal power plants don't take up a ton of space

fun uses of geothermal: geothermal heat is produced and used in Iceland to melt snow on the roads and such.

Tidal

I tend to think that tidal power sucks. In part because it is very expensive, and in part because at best it could provide all of 1% of world electricity.

Tidal power has two main problems: it uses salt water and it has only a few areas that it will work. There needs to be tides of sufficient strength that it can produce electricity, and even then, salt water is corrosive, limiting the lifetime of these power plants and making the levelized capital cost very high.

Tidal power also comes in two main flavors. One is tidal impoundment. Think of it as creating a hydroelectric dam every time the tide goes out. The tide comes in, fills up the area behind the impoundment dam, and then as the tide goes out, the area behind the impoundment dam is filled, and as it flows out, it generates electricity. As you recall from the hydropower article, the energy produced from a hydro dam directly relates to its height. The height of a tidal impoundment dam is limited by the height of the tide. In most parts of the world, this is not very high, so it is not very efficient. Moreover, it kinda messes with natural habitats.

The other type of tidal power is more or less an underwater wind turbine. The problem is that all the moving parts are underwater in the ocean. Where decay and breakdown happens quickly. Moreover, looking at the equation of energy produced via such a turbine:

where A is area, and v is velocity,

we quickly realize that the area of the rotor for a tidal turbine is small (wind turbines have 40m blades, and we aren't gonna have 80m of water depth in most places to replicate that scale in tidal areas), and the speed is slower (water doesn't flow at 6-8m/s very often). Tidal power can't scale and produce as much energy as wind. And the environment is unfavorable. In short, this is not a viable resource for large-scale energy production. And it costs a lot.

Hokay, that is all for today! Thanks for reading!

-Jason Munster

 

Solar 2

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Photovoltaic solar cells. Solar PV.

This is not an easy thing to describe. For some, you may want to just skip past the technical section, cause it is pretty technical.

Solar PV: they used to take as much electricity to make as they produced in their lifetime. Now they they produce about 5x as much energy as they take to make, and the time to break-even on emissions compared to our cleanest fossil fuel stations is about 6 years (see Kannan, 2005, Lifecycle Assessment Study of Solar PV). Of all the clean technologies (nuclear power excluded), this is the only one with the potential to supply world energy needs (that is the subject of a later post).

In other words, when you hear some fool saying that solar panels take as much energy to manufacture as they ever produce, they are referring to a specific type of solar cells called thin film. A type that was made in the 70s and 80s and only goes into things like calculators. Feel free to ask them to stop being foolish.

Some Math

The light we see is not a homogenous single color. In fact, the light we see is not even all the light that is coming from the sun. Infrared and UV rays are also light, but we cannot see them at all. All this light is just an electromagnetic wave. The waves have different wavelengths, but the same speed, and so all the different wavelengths travel together. What we see is a blend of a tiny part of the electromagnetic spectrum.

This is the electromagnetic spectrum. Visible light, what we can see, is only a small part of it.

This is the electromagnetic spectrum. Visible light, what we can see, is only a small part of it.

The amount of energy contained in a photon is equal to

where is the wavelength. h and c are Planck's constant and the speed of light, respectively.

Smaller (shorter) wavelengths give more energy. This is easily shown just by plugging a smaller number into the denominator. Stuff in the infrared is long wavelength, and stuff in UV, X-ray, Gamma ray, etc, are really short wavelength.

Technical Stuff

There is no easy way to do this. I am going to use some terminology that most of you all are unfamiliar with.

A Photo Voltaic (PV) solar panel is a sandwich of two materials. The materials are largely the same, with a few key differences. Both are likely made of silicon (processed sand). But each one has very specific impurities put into them, in a process called doping (not the same type that Lance Armstrong does). This doping is incredibly technical, and very skilled chemists are paid a ton of money to figure out how to do it.

Doping

I won't get into specific materials. Some elements cause there to be a shortage of electrons, or a electron hole, in the whole material (p-type semiconductor). Other elements cause an excess of electrons (n-type semiconductor). So you have one material that can accept electrons, and another material that can give electrons. Putting them together (literally stacking them together) makes magic happen. And by magic, I mean quantum mechanics. Which to most people, including many who study it, is no different than magic.

Just because one has more electrons doesn't mean it wants to be nice and share them. The electron in the n-type literally needs to be excited to be shared. And in PVs, what turns the n-type material on is sunlight. More specifically, photons. Photons are particles of light. ("But Jason!" you say, "Isn't light, like, a wave?" to which I say, "It is both a wave and a particle! Please don't ask me why, just accept it.") Photons contain energy based on their wavelength. Shorter wavelength, more energy (see above).

Here's the fun part. It takes energy to make the n-type semiconductor want to party with the p-type semiconductor. There is a threshold level of energy that needs to be met to kick that electron up from the n-type to the p-type. Too little energy, and the photon doesn't get excited enough to go to the electricity-production party. If there is enough energy from the particular wavelength of light to make that electron jump, then is does jump.

But what if there is more than enough? This threshold level is pretty much determined. Any extra energy will be wasted. This is why PV cells are not particularly efficient. There is a huge amount of light that is too low-energy (all of infrared) for the cell to gather any energy from. There is a lot of light that has much higher energy than required to meet the threshold energy as well. The excess energy is wasted as heat. This can be solved by having a multiple junction cell (multiple junctions just means it has a bunch of different width absorption gaps, so it can harness tons of different energy levels in light). It is capable of absorbing more wavelengths of light, increasing efficiency. And since it has multiple junctions, it is also more expensive and complicated to produce.

Hokay, so, what happens next? You have an electron that has jumped the gap. Then you close the circuit by connecting them with a wire. The electron will go home, back to the n-type, and create an electric charge on its way down. That's about it.

New Methods 

Transistors are expensive. Normal glass optics are relatively cheap. The transistors absorb about 20% of the light that hits them. So it would make sense to use cheap optics to focus more light on the transistors and make the transistors small, yes?

One problem with these cells is how warm they get. If they warm up too much, they begin to lose efficiency. Here we see that we have a tradeoff. We want more optics and fewer cells, but if we do this, they get too warm. They stop being efficient. Some scientists and engineers are working on increasing the efficiency of the cells instead, to get more electricity from light. Otherwise, there are clever ways that some mechanical engineers are trying to get around these issues. One new design uses focusing mirrors and liquid cooling to get around this issue.

The pertinent stuff

Everything pertinent, like insolation and weather, was in the last solar article.

Next post: rounding up some of the stray power sources: tidal, geothermal, wave, and then I am pretty much done.

Thanks for reading.

-Jason Munster

Some dams

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Dams. They provide clean electricity. Sometimes they cause earthquakes that kills thousands of people.

As I mentioned before, hydro is a tapped resource in all places except Asia, Africa, and South America. In other words, it works great in developing countries. It is not an option for developed countries.

Despite that I provide references where I can, this post is pretty unprofessional. Also, since I didn't post last week, this will be a mid-week post. It is as close as I will get to a blog rather than a collection of science-based articles.

Hydro Plants Causing Earthquakes

Three gorges dam represents the domination of Man over Environment like nothing else on the planet.

Remember that earthquake in Sichuan earthquake in 2008 that killed 60,000 people? This earthquake was likely caused by the three gorges dam.

three gorges dam! "I cause Earthquakes" says Three Gorges.

How do earthquakes happen in general? Stress builds up in the Earth, usually from shifting tectonic plates. Loading a massive amount of water in an area increases the stress by huge amounts. Dams load billions of tons of water into an area. Dams are not the only way to do load the environment to prime it for an earthquake. Downtowns of cities with skyscrapers also do a pretty good job of it. But dams are way better at it.

Pros and Cons of a hydro plant

Let's look at more information on Three Gorges. I've recommended y'all read When A Billion Chinese People Jump. In that book, we find that the past several presidents of China have been hydrological engineers. The most recent one didn't show up at the opening of Three Gorges because, because in some ways, it is very controversial. It has very strong benefits and issues. Despite negative effects, it produces 22.5GW of electricity. In other words, it replaces 22 very large coal fired power plants. And in China, that means 50 years of 22 unfiltered powerplants not belching harmful pollutants into the atmosphere. In case you haven't heard, China in general and Beijing have some of the worst air pollution in the world. Before you start judging, remember all those jobs that are being outsourced to places like China? This is the result of that. We are exporting our trash and our pollution to poor countries, where environmental regulations are more lax. Getting back to the point, those 22 coal fired power plants that are being replaced would probably have caused more long-term deaths than the earthquake. Moreover, China is a very dry country. Like most dry countries, it is prone to flooding without controls. Containing the river behind the three gorges prevents the downstream from ever being flooded again. So they saves the homes and such of millions of people, but had to move millions behind the dam, and it also flooded historic areas. How's that for controversial? Serious positive and negative implications. No dam embodies the pros and cons of building a dam more than Three Gorges.

Other uses of dams

It turns out that producing electricity is only a small part of what dams do. Many are used for irrigation, for flood control, for reservoirs, and to protect the environment. We are mostly an energy blog, so we don't give a damn about all that stuff. Except one major point: electricity is less than 10% of the economic benefit from dams. A huge amount is in flood control, irrigation, and recreation.

FEMA says these are the benefits of dams. Notice that hydroelectric is tiny.

Hoover Dam

Hoover "meh" Dam

When you think of a huge American dam, you think Hoover. This is silly. It is a 2.5GW dam. It is 10% the size of Three Gorges. It is like comparing Bangor ME, to Boston, MA. One is just tiny. Why do people care about Hoover? I dunno. Maybe after spending too much time in Vegas they decide they want to see something natural? Hoover dam is tiny. It only replaces 2 or so coal plants. Hoover Dam, you are not worth wasting words on.

Grand Coulee Dam

Grand Cooulee Dam is one of the largest dams in the world. Notice the size of the houses for scale.

Grand Cooulee Dam is one of the largest dams in the world. Notice the size of the houses for scale.

You know which dam is an American dam? Coulee Dam. This dam produces 7GW. Fully 3x of Hoover, and near 1/3 of Three Gorges. It is also in Washington state, which, compared to Nevada, is better in every way except for gambling and prostitution. Which shouldn't be family activities. Why don't more people visit Grand Coulee instead of Hoover? This is not a rhetorical question. Someone please tell me.

Grand Coulee has this other sweet feature I already discussed. They have pumped hydro storage. In other words, they pump from the area behind the dam to another dam that is far higher up. This is a great way to make a giant battery. It recovers about 60% of the electricity that is put into it.

Interesting note: While scouting around the interwebs looking for information on the pumped hydro storage at Grand Coulee (it is really difficult to find), I stumbled across a blog that already has written posts that are way more in-depth maths about many of the things that I write about. If you are one of my sciencier readers, you might want to check his page out. I will poke around there some and give you more info on it later.

Dams produce clean power. They are environmentally friendly! Or not. 

We have discussed how dams get backed up and leave heavy metals in the sediment, and more or less create environmental issues. And how they block fish from swimming upstream. I wanted to touch on one thing again. In China, many places that built clean hydro plants attracted industry, cause industry loves inexpensive power. And hydro power is amongst the cheapest. So the skies and waters became quickly polluted with industrial wastes. Like, red polluted.

Image from the link above. It looks like the Earth is bleeding. I don't think this is healthy. And all my Boston readers are afraid of the Charles.

Outsourcing manufacturing seems even a bit crappier than it used to, doesn't it? Sure, we lose jobs, but they lose lives and the environment.

Alright, that's about it for my quite unprofessional rant. Thanks for reading.

-Jason Munster

Power Grid

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I was struggling to write a post about PV solar panels (the struggling part came in while trying to describe the quantum mechanics that take place), and realized that I need to describe how our power grid works in far greater detail than I had before. What follows is the gory details about how power is transmitted to your home. This is important because while solar power costs 5x as much as coal on the wholesale market, it only costs about 2x as much as coal at your house. Sometimes less. This is because coal-powered electricity is wheeled and dealed through several players as it reaches you, and is marked up every time. Solar power dumps straight into your home. Some of you are gonna love this article, others have already closed it.

power_grid_300

On a logistical note, I haven't posted in the last two weeks cause I am too busy with life things to write both the blog and play computer games. Computer games sometimes win out. Thanks, X-Com: Enemy Unknown.

Generators, LSEs, Home Energy

Generators are all the different types of power plants we have discussed. They produce power, and in a deregulated market, sell the power to the grid. They are given a price based on demand. We have discussed how each power plant will "bid in" a day ahead and say how much power they can produce at which prices. As more power is demanded, the price will rise to bring more expensive power online. No matter what the power plant bids in, if they are online, they will get the per-MWh payment of the most expensive plant to come online. In other words, the marginal cost of energy production is what each power plant gets paid per MWh. If an expensive power plant is brought on-line for $1000/MWh, for instance, every single plant that is operating will receive that.

Okay, we have also seen the cost to produce power in several posts. It makes sense to repeat it here.

U.S. AVERAGE LEVELIZED COSTS (2011 $/MEGAWATTHOUR) FOR PLANTS ENTERING SERVICE IN 2018
PLANT TYPE CAPACITY FACTOR (%) LEVELIZED CAPITAL COST FIXED O&M VARIABLE O&M (INCLUDING FUEL) TRANSMISSION INVESTMENT TOTAL SYSTEM LEVELIZED COST
Dispatchable Technologies
Conventional Coal 85 65.7 4.1 29.2 1.2 100.1
Advanced Coal 85 84.4 6.8 30.7 1.2 123.0
Advanced Coal with CCS 85 88.4 8.8 37.2 1.2 135.5
Natural Gas-fired
Conventional Combined Cycle 87 15.8 1.7 48.4 1.2 67.1
Advanced Combined Cycle 87 17.4 2.0 45.0 1.2 65.6
Advanced CC with CCS 87 34.0 4.1 54.1 1.2 93.4
Conventional Combustion Turbine 30 44.2 2.7 80.0 3.4 130.3
Advanced Combustion Turbine 30 30.4 2.6 68.2 3.4 104.6
Advanced Nuclear 90 83.4 11.6 12.3 1.1 108.4
Geothermal 92 76.2 12.0 0.0 1.4 89.6
Biomass 83 53.2 14.3 42.3 1.2 111.0
Non-Dispatchable Technologies
Wind 34 70.3 13.1 0.0 3.2 86.6
Wind-Offshore 37 193.4 22.4 0.0 5.7 221.5
Solar PV1 25 130.4 9.9 0.0 4.0 144.3
Solar Thermal 20 214.2 41.4 0.0 5.9 261.5
Hydro2 52 78.1 4.1 6.1 2.0 90.3

So the cost to produce is the total system levelized cost (and now you should realize that producing power for $1000/MWh is ridiculously high. Except it has happened recently and momentarily in New England).

People at home don't see the price that a generator gets. Do you notice that you pay about 20 cents per KWh in MA (I use MA cause apparently all my readers are here), it is $200 per MWh. What gives? All these power plants are producing power for way less than that. Except for solar thermal and offshore wind, which both suck and are expensive.

The reason for this is that home/commercial retailers do not buy from the generators and from the wholesale market. Things called Load Serving Entities (LSEs) buy from the wholesale market. Often they will just be your utility company. They then distribute it to end-users or to other complicated things that we don't care about. The end users are your households and commercial things like shopping malls and stores and offices.

Sidebar: One important thing to note is that industry usually buys directly from generators. So while we pay $200/MWh for electricity, a Ford power plant might pay $60/MWh. This has implications that we will discuss later.

So, the LSE buys electricity off the wholesale market. And then marks it up and sells it to consumers. That is why you pay $200/MWh.

RTOs, system management

This section is getting specific, some of you may want to skip to the end of the article, the implications part.

Who tells generators when to come online and manages the wholesale market? Regional Transmission Operators. In New England, our RTO is called ISO-NE, for Independent System Operator of New England. They take bids and determine which power plants produce. They have important things to consider, like making sure a regional power line isn't too congested.

Line Losses

Nearly all power lines lose a percentage of their power as heat. Transmitting long distances loses around 8% of power. This is because there is always some resistance to the flow of electricity. It is like friction for the flowing of electrons. Power lines also have a limit to how much power can flow through them. If you try to go past the limit, they heat up rapidly and lose a ton of power.

The latter is something that the RTOs manage, to make sure that there won't be problems. The former has massive implications for renewable energy. Most of our renewable energy is wind and solar. Like wind in the sparsely populated midwest. And solar in completely unpopulated deserts. Transmitting this power to cities incurs huge line losses. With current capabilities, transmitting power from Iowa wind farms to NYC would make power more expensive than just building the wind farm near NYC, despite that wind in NY sucks (heh, punny). I don't have a source for this, I just saw it at a talk at Harvard.

Implications for installing renewables at home, commercially, and in industry

boa_photo1

We pay $200 per MWh of power as residents in Boston. Solar PV in the best cases is $144. This will be in deserts. In MA, we don't get as much sunlight. But for the sake of argument, lets say that the average cost of solar in MA comes out to be $200-$250. With subsidies, it will be less. So would you pay $200 per MWh from your utility, or $200 per MWh to produce your own energy and stick it to the man? Also your own power would be clean, with far less CO2. With subsidies available in places like MA and NJ, solar comes out to less than $200/MWh at home.

Next lets consider commercial places. They also buy from LSEs. This is why you see a ton of them building solar panels. It makes sense economically and gives them a good vibe that the public likes.

Finally, let's consider industry. They buy directly from the wholesale market. So they pay closer to $100/MWh. They won't give two shits about renewables. Because they won't save money by installing renewables on their sites.

And this, my friends, is the trend we see. On-site renewables are adopted by commercial real estate and by residents, and industry is highly unlikely to ever embrace it. Interesting, eh?

Thanks for reading!

-Jason Munster

Solar Power

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Solar power. It comes in two primary flavors: photovoltaics (PV) and concentrated solar power (CSP). The latter is easy. I decided to do solar power this week, and go back to the dams next week. Big picture: CSP is a bridge technology at best; an investment in most places is little more than a show that the investor is serious about green tech. Moreover, not all places are created equal to invest in solar power. Many of the places that offer the best incentives to have solar power (NJ, MA, Germany) are far from the best places to have solar power.

So this time: insolation, what it means, where it happens. And CSP. PV comes later. Cause it involves quantum mechanics.

So, first, solar insolation map, AKA "Where is the sun shining all the time" map.

Solar power resources in the US. Darker colors indicate better regions for solar power.

Solar power resources in the US. Darker colors indicate better regions for solar power.

Who is not surprised that Alaska is awful for solar power? But check out MA and NJ. Why are they giving tax breaks to install solar cells? Easy answer. To drive the technology forward. Solar panels are really useful in places without any other power source. Like small villages in Africa and other depopulated places. California also has big incentives to build solar, and at least that makes sense, yes?

What determines how much insolation a place gets? Well, you need sun to have solar power. The sun doesn't come out to party at night, so no solar power. A huge one is how much atmosphere the sunlight has to pass through on the way to the the solar panel. More atmosphere means more absorption and dispersing of sunlight (the atmosphere reflects, absorbs, and spreads out sunlight). So higher elevation, like mountains, helps. Less atmosphere. On a related note, the latitude is also very important. Far northern places don't get as much sun annually (Canada, Alaska). Finally cloud and moisture make a huge difference. If there are clouds or moisture in general, sunlight is blocked. This explains most of the east coast of the US, as well as why Nevada, a giant desert, has great insolation. It has a high elevation, and no moisture to make clouds or block sunlight.

The equivalent amount of sunlight hitting the earth at a high latitude spills out over a larger area. In other words, there amount of energy per area is lower. link

The equivalent amount of sunlight hitting the earth at a high latitude spills out over a larger area. In other words, there amount of energy per area is lower. link

CSP is easy. There are a bunch of mirrors, either flat or parabolic (to focus the light even more intensely), and they reflect light to a single point. It produces heat and and then that heat is used to make steam and drive a turbine, just like the basic thermal power plants we have discussed. The heat is typically stored in molten salt, cause it can store a whole lot of energy before it rises a degree in temperature (kind of like water). The heat from this molten salt is slowly released to make that steam for the thermal part.

CSP in action. Lots of light reflected to a single point that then gets very hot. link.

Given that some places on Earth receive upwards of 500W/m directly to the surface (assuming no clouds, no pollution, and daytime), a CSP plant that is 500m*500m could produce 125MW of power. Sounds great, right? 'Cept we know from basic thermodynamics that a thermal power plant that this thing is likely going to be 30% efficient. So something with a quarter of a square kilometer footprint might produce 40MW of power.

So why don't we use this? First, the depiction above is too rosy a picture. CSP is not all that efficient, because if you look at the picture above, you see that not all the area is used for gathering light. There are plenty of empty spaces. Moreover, the transfer of heat from the salt to water is not very efficient. Cause the high temperature and low temperature of the Carnot cycle are closer together (review the thermal power plant post for a review of Carnot efficiencies for all heat engines). Finally, this stuff is expensive. It is easily 2x as expensive as almost any other power technology (other than PV). It requires water to clean the mirrors and has other maintenance costs, the mirrors themselves are quite expensive, and the entire design is expensive. And, if you want to harness the power of the sun, there are better alternatives. Like PV.

As you can tell, I don't have a very high opinion of CSP. Why is that? Take a look at this guy again:

U.S. average levelized costs (2011 $/megawatthour) for plants entering service in 2018
Plant type Capacity factor (%) Levelized capital cost Fixed O&M Variable O&M (including fuel) Transmission investment Total system levelized cost
Dispatchable Technologies
Conventional Coal 85 65.7 4.1 29.2 1.2 100.1
Advanced Coal 85 84.4 6.8 30.7 1.2 123.0
Advanced Coal with CCS 85 88.4 8.8 37.2 1.2 135.5
Natural Gas-fired
Conventional Combined Cycle 87 15.8 1.7 48.4 1.2 67.1
Advanced Combined Cycle 87 17.4 2.0 45.0 1.2 65.6
Advanced CC with CCS 87 34.0 4.1 54.1 1.2 93.4
Conventional Combustion Turbine 30 44.2 2.7 80.0 3.4 130.3
Advanced Combustion Turbine 30 30.4 2.6 68.2 3.4 104.6
Advanced Nuclear 90 83.4 11.6 12.3 1.1 108.4
Geothermal 92 76.2 12.0 0.0 1.4 89.6
Biomass 83 53.2 14.3 42.3 1.2 111.0
Non-Dispatchable Technologies
Wind 34 70.3 13.1 0.0 3.2 86.6
Wind-Offshore 37 193.4 22.4 0.0 5.7 221.5
Solar PV1 25 130.4 9.9 0.0 4.0 144.3
Solar Thermal 20 214.2 41.4 0.0 5.9 261.5
Hydro2 52 78.1 4.1 6.1 2.0 90.3
Solar thermal is expensive. And the capacity factor is junk. There are places for it, but those are so few that it is not worth further exploring this technology.
That's it for now. Thanks for reading!
-Jason Munster

Hydro Power

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Hydroelectric Power is pretty simple, yes? Build a dam, run water through turbines, get energy out. Turns out that it is a bit more complicated that that. But not by much, actually. So I am going to do a quick summary of how hydropower works, the environmental disaster that it can be (always with the tradeoffs, eh?). I was going to profile three major power plants: Hoover, Grand Coulee, and Three Gorges. But I ran out of space. Next week we will discuss pumped hydro to make the biggest batteries on the planet, and also these three dams in details.

DSC01732

Hey! Finally! A picture I took myself! I was at the three gorges dam as they were just completing it. Also, China has air pollution issues.

How does water power work? Put simply, water falls from a height and the energy of it is harnessed by spinning a turbine. More complicated, it is mass*gravity*height:

Schematic cross-section / block diagram of a hydropower plant. link.

Now we also need to round down for efficiency. Our thermal power plants are limited by carnot efficiency, yes? And even the best don't really break 50% efficiency all that easily. What would you guess the efficiency of a hydro plant turbine is, then?

That depends on the type of turbine used. It turns out that turbines are some of the most efficient parts of any generating facility. In short, expect these guys to have 90%+ efficiency, probably closer to 95%. Different styles are used depending on the height of water drop (water moving really fast from a half-kilometer drop will have very different dynamics than water moving from a 20m drop).

The general design of a hydropower turbine. Water flows through the blades and the generator is, in turn, spun quickly. link

So let's figure out how much water we need to move to make 100MWh of electricity from a 200m drop! Now 1 MWh is  , so 100MWh

of water needs to be moved. In other words, it takes 18 thousand kilotons of water movement to produce 100MWh. Or, looked at another way, 18,000 cubic meters of water. Still not following? It's about 8 olympic sized swimming pools worth of water. Dropping 200m. Or 1/8 a mile, for you Americans out there that don't play in Metric.

Hokay, enough maths for now. This sounds great, right? Why don't we build these things everywhere? When I take courses on how to fix the environment, there are always a majority of people that assume we can build more hydro power plants. But we can't in the US. Why not?

Well, it turns out that you need to have a large height drop to make this work. You also need a lot of water flowing into whatever reservoir is behind the dam, a ton of land behind that dam to flood, and you also need enough high terrain behind it so the water doesn't spill out everywhere. Moreover, you need a massive height difference between the upper reservoir and lower reservoir to make it work. Example: the Amazon river has a huge % of total world river flow, but we can't get electricity out of it, cause the elevation drop of it is so tiny. In short, there aren't a ton of places where where hydro works well. And imagine if a few people live there. Most aren't gonna take to kindly to their homes being put under tons of water. But you know where this can happen? China! They moved 1.3 million people to build Three Gorges. More on that later. Also, Africa has a ton of places that are building dams. Turns out that China is funding a lot of these. Cause China is starting to do humanitarian things internationally to make allies with the countries that will be the source of most world growth over the next 50 years. Upsides and downsides of a command economy, right?

Hokay, I got distracted there. Environmentalists don't like dams because they mess up fish migrations, destroy natural habitats, destroy the landscape in general, and in many countries, since hydro power is so cheap, heavy industry moves in next to them to get the cheap electricity. China is a great example (sorry I keep using you as an example, China, but I haven't read about other countries much). Along many rivers, supposedly clean hydro power goes in, only to be followed by very polluting industries. Rivers turn funny colors, the water is terrible to drink, and you can't see the sun through pollution on several days. This is getting better, cause China is making the middle-income transition, and citizens are demanding safer living environments.

I got distracted again. Other problems with dams? They tend to be on rivers. Rivers carry sediment. Much like wind can pick up grains of sand and throw then around, rivers do the exact same thing. They carry a lot of sand in them. But when they hit a damn, the river stops. The sediment load drops to the ground. After several decades, sufficient sand has dropped to clog the dam. Adding to this problem is that these sediments have a bunch of heavy metals that have been leached from the local environment. In short, a hydro dam leaves behind a mess that is quite hazardous. Cleaning it up can be difficult. Still, hydropower doesn't cause many deaths, unlike coal-fired power plants.

Focusing on that last point, what does hydro power not produce? CO2. Mercury. SO2. NOx. It produces none of the nasty things that coal fired power does (even gas-fired plants produce NOx and CO2). It tends to be very inexpensive. It is much prettier to look at a hydro plant than a coal, gas, or nuclear plant (Except on a polluted day in China, look at that picture again!).

We are running out of space in this article (I am calling them articles cause I am pretending they are articles on a web page instead of a blog post, cause I am pretentious). To summarize, hydro power is cleaner than other power supplies. It is cheaper than most. It does have its drawbacks, including displacing people and destroying land, but these are smaller than the drawbacks of coal and natural gas. It is also a nearly completely tapped resource in the US.

-Jason Munster

End-note: if you have a lot of interest in this sort of thing discussed here, I would highly suggest the book When A Billion Chinese People Jump by Jonathan Watts. It is an amazing book

.