Category Archives: Clean energy

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

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

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Wind Power

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I haven't posted anything in a while because I am teaching this semester (Earth Resources and the Environment), which has made me incredibly busy, and also I was playing a computer game for the past month. Anyways, some friends told me they actually read this, so I am gonna start up again.

Today we discuss how wind power works, how a wind turbine works, and limitations on placement of wind turbines.

Block diagram of a wind turbine. Wind spins the blades, which in turn goes through a transmission to spin a turbine to produce electricity.

Block diagram of a wind turbine. Wind spins the blades, which in turn goes through a transmission to spin a turbine to produce electricity.

Wind power harnesses the power of wind to turn a turbine. Unlike every other power plant we have discussed, this is not a thermal plant. How does wind even happen? As we all know, the sun shines more directly near the equator than it does the poles. And so the equator is heated more than the poles. The Earth doesn't like having one part heated and another not, so the major prevalent winds are the way the Earth redistributes this uneven heating from the equator to the poles. Smaller winds are local manifestations of this phenomenon. In short, wind power is extracting the energy deposited by the sun.

Next: the design

The mechanical design of a wind turbine. Link

The rotors of a wind turbine catch the wind, and thanks to Bernoulli's principle, the wind forces the turbine to spin. Think of it as creating an area of low pressure behind the blade, so the blade is getting sucked, or pulled, rather than pushed in a circle. These blades are attached to a hub, which spins with it. The entire box behind the turbines is called the Nacelle, and contains all the parts that produce power. The hub itself spins somewhat slowly, but thanks to a gearbox, the shaft that goes to the generator spins much more rapidly. The windvane senses the wind direction, and a motor beneath the hub rotates the entire turbine to face directly into the wind.

Wind power plants face four primary limitations. First, they don't work when wind isn't blowing. So you aren't placing these things in windless or low-wind locations. Second, depending on the design of the turbine, each has a maximum wind speed where it most efficiently extract energy. In fact, during high winds, they have to shut down to prevent damage. Third, there is a factor called the Betz limit that indicates that the most energy you can extract from wind is about 60%. In reality, the best might be 45% efficient. A corollary fourth limit is that you cannot place wind farms too closely, because they become far less efficient if you place them nearby. They literally suck out the power from the wind. In the end, availability of location is the most important

This photo from NOAA uses LIDAR to track the turbulence produced in the wake of wind turbines. It visually depicts the limitations of putting turbines in the same place. The turbulence behind the turbines can damage the props on the next turbine, requiring further replacement. It also reduces the efficacy of the next turbine. link to NOAA.

Ultimately, the largest problem is where to site wind farms. You can't put them in places without wind, or you spend a ton of money on them and they don't return the payment.

This map indicates regions and their use for wind farms. It shows that many areas are not great for wind farms. Click the link for a more detailed image.

There are two closely linked issues associated with wind power. In most places, wind does not always blow. When the wind is not blowing, power cannot be extracted. This is called intermittency. It means that wind power cannot provide baseload power. In some places, like California, the intermittency is dealt with by power up peaking gas-powered power plants. In other places, the intermittency is seen as an insurmountable issue (California surmounted it. Those other places are foolish.) Other methods of dealing with it are compressed air storage (more on that later), batteries, and pumped hydro (more on that later).

Another important feature of wind turbines is size. To get more power from a single turbine and reap larger economies of scale, you build a taller turbine. Also, taller turbines reach farther up into the part of sky where wind it a bit more constant. But those huge turbines, that can produce up to 5MW each (recall a larger power plant is 1000MW), are relatively new. We are not sure how long they last in the wild. Maybe 50 years (like a normal power plant) or maybe 20. This is important, because per MW, wind power used more resources to build than almost anything else.

Now, offshore wind is a different beast entirely.

Offshore wind turbines become progressively more expensive as you move to deeper waters.

Offshore wind turbines become progressively more expensive as you move to deeper waters.

These things need to be moored to the ocean floor, or have very expensive floats. It can increase production cost by a factor of three. Ameliorating this fact is that wind is often more consistent offshore. But these things face waves, corrosive ocean water, severe storms, etc., and need to be built very strong, increasing costs. Moreover, they need a way to connect them together, and then very powerful regional lines to transfer the power to mainland. Expensive. If you remember my post comparing the cost of nuclear power to other types, offshore wind is mad expensive.

Another interesting point about wind power (and solar): they produce DC power. This is direct current, like a battery. The power we get from the wall is AC power. It alternates. Anything with a motor likes AC power a lot. Many electronics prefer DC power, hence needing AC adapters for all your electronics. Batteries use DC. Another fun fact about AC vs DC? Electricity make your muscles constrict. If you grab something with AC, since it alternates you let go. You grab something with DC, like a car battery or a taser while being arrested, that stuff causes constriction and you can't let go. Point is, stay away from DC electricity.

Back to the point: Somewhere in the process, whether at the turbine or at a collection station, this electricity needs to be converted to AC to use on the electrical grid. More expenses. In short, offshore wind is incredibly expensive, and only for countries that are afraid of nuclear power. In a later article, I hope to compare the resource costs per MW of constructing each of these types of power plants.

Thanks for reading again!

-jason munster

 

Nuclear Reactors Final

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I am getting bored of this topic, and I want to get to wind-solar-hydro so I can finish up with the energy technology stuff and write varied stuff. So I am going to compress it a lot. If anyone wants to see it expanded, let me know and I will take care of it later.

This post is about breeder reactors, thorium reactors, preventing nuclear proliferation, how the electricity costs stack up to other power plants, and why nuclear power is so expensive.

Nuclear power is expensive because the up-front costs are massive. The cleanest and most efficient coal fired power plants might cost a billion dollars to build. It might take 5 years to build it. Nuclear power plants seem to cost about $8 billion to build with all the safety features they use to prevent nuclear meltdowns (seriously, the new tech is very safe, and it shows in the cost). And they seem to take 8-15 years to build, depending on how much Greenpeace or pretty much every other group tries to stop construction via litigation. In other words, they take out an $8B loan and accrue interest for 8-15 years before they can start paying it back. Stuff costs a lot. Why do it? Cause nuclear waste can be contained, unlike the NOx and CO2 from natural gas and coal plants. Also, South Korea thinks it can build a nuclear plant a nuclear power plant in a short amount of time for only $5 billion. United Arab Emirates decided this was a good idea, and is buying four South Korean nuclear reactors to desalinate water.

Schematic of the South Korean nuclear power plant to be built in the United Arab Emirates, from link above.

The US Energy Administration Administration agrees that nuclear power is now less expensive than it used to be. I have ripped a table straight off their web page that shows it (see, I really am getting lazy in this post).

Table 1. Estimated levelized cost of new generation resources, 2018 
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

 

Note that last column is $ per megawatt hour. It is the bottom line cost of producing power from that plant. First, what is dispatchable vs non-dispatchable? Dispatchable means you get it whenever you want it. You can ramp it up or down however you please. Non-dispatchable means that you depend on external factors, like the fickle winds of.. well.. winds?

Tangent! Winds are really just redistribution of energy from the equator to the poles. The sun shines more at the equator, heating it up, and then energy likes to move from areas of high energy to areas of low energy, so it does it using wind. And sometimes hurricanes. So really, wind power is just really inefficient solar power. You know what else is really inefficient (and slow) solar power? Hydrocarbons and coal. Cause they are really just buried plant and algae matter and such. That is tens to hundreds of millions of years old. So, coal and oil are really just really old, slow, and dirty solar power. Tangent done!

Tangent picture? This shows how the equator heats more than the rest of the earth. These extra heat has to redistribute to be more even. Hurricanes start near the equator cause of the heat there, then move away from it. from: http://oceanworld.tamu.edu/resources/oceanography-book/oceansandclimate.htm

Nuclear power is almost as cheap as coal power, and cheaper than clean coal (note, clean coal still produces a ton of CO and NO)! What gives? How is nuclear so inexpensive? Well, we haven't built a nuclear power plant in the US in years. We don't know what it will actually cost. Those are just estimates. Also, people are quite scared of nuclear power. The cost of building nuclear power rises when you have environmentalists and NIMBY folks suing the pants off nuclear power developers. But let's make one thing clear: if the new generation of nuclear power plants are as inexpensive as they are supposed to be, the power is less expensive that all other power plants other than natural gas (note: the US does not have capacity to build more hydro power), and less expensive than even that if you account for NO produced by and methane leaks associated with natural gas power (methane production and transport will always have leaks, and it is 23x as powerful a greenhouse agent as CO2).

Let's look at a few more things on the chart above. Remember when I said natural gas got cheap? Look at how cheap it is to produce power from natural gas on the chart above. Think anyone is building nuclear, solar, or offshore wind when you can build and deploy reliable natural gas power? Somehow, the answer to this is yes. Yes, people are building all these things, despite being expensive. Which is kind of cool.

Before moving away from costs, look at the variable costs. The variable costs are high for everything except renewables and nuclear. Why is this? Cause renewables and nuclear don't really use fuel. Yes, a nuclear plant uses fuel, but it costs almost nothing relative to the labor and the capital costs. All the cost of these is upfront CAPEX (capital expense), and then you get free power.

Finally, lets take a really close look at the variable costs. This link is pretty sweet for those of you interested. It contains variable costs for each power source. You can see that fuel is the bulk of cost of fossil steam plants, but less than a quarter of the total cost of nuclear, and nuclear fuel is 1/4 the price per energy unit than even dirt cheap natural gas.

Enough about costs! Onto breeder reactors!

In the first post I mentioned that one part of nuclear reactions is to give off neutrons. Sometimes instead of a neutron splitting an atom, the atom absorbs it. U-235 is the uranium we use in nuclear reactors. U-238 doesn't produce as much heat, cause it doesn't like to decay as fast, so it isn't viable nuclear fuel. Or is it?! U-238 is like a catcher in baseball. Except it catches neutrons. And then it incorporates them into its nucleus to become U-239. In other words, it really isn't like a catcher in baseball.

The breeder reaction series. From: http://nuclearpowertraining.tpub.com/h1019v1/css/h1019v1_76.htm

What's special about U-239? It decays rapidly through a special type of decay to become neptunium-239 and eventually plutonium 239! This process can extract up to 100x the energy from nuclear fuel. You know what's magic about that? Less nuclear waste produced. Also, you produce a ton of nuclear fuel this way. You can also use thorium-232, which then becomes uranium-233 after absorbing a neutron, which can in turn be used for nuclear fuel. Thorium is very cheap and very abundant. So the plutonium and uranium that is magically created through awesomely manipulating nuclear forces is then used in nuclear thermal reactors to produce power.

Nuclear proliferation!

Having a nuclear power plant does not mean you can make nuclear bombs. Nuclear bombs required U-235 enriched to a very high level. What exactly is enrichment? Natural uranium is less than a few percent U-235, the rest is U-238. The uranium comes as a solid, and is processed by making it dance with a bunch of flourine. UF is produced, which is gasified uranium. The U-238 is slightly heavier than U-235, so it very very slowly settles to the "bottom" if you spin it very fast in centrifuges. Once you have enriched it to somewhere between 5 and 8%, U-235, it is good to go into a reactor and make energy. To make a bomb, you have to enrich it to around 90%. Enriching it further gets exponentionally more difficult. Getting from 50% to 70% is much more difficult than getting it from 10% to 50%. So making bombs is hard.

What about plutonium? Seems like any fool can make plutonium. And in fact, they can! All you have to do it get some U-235, wrap it in U-238, and you have make a breeder reactor in your back yard! This seriously happened. Someone made a breeder reactor in their garage at 17. And this wasn't one of those kids that comes from a brilliant family with a ton of money that goes to work in a world famous lab and 'discovers' a new technique under the watchful eye of one of the most brilliant researchers in the world. This was your every day kid who was just really interested in something.

Except that building a nuclear weapon from plutonium is even more difficult than from uranium. Cause when you make the plutonium, you always get a large amount of another plutonium isotope. The other isotope loves to go critical much earlier than Pu-239. Remember what happens to a potentially critical nuclear reaction when the fuel gets split up? No? Remember what happened to Chernobyl when a small gas explosion spread the core out everywhere? It completely shuts down the critical reaction. In other words, plutonium loves to accidentally blow up to early and just spread itself around without going critical. Not much of a weapon there. How do we have plutonium bombs then? Really smart people made special triggering mechanisms to make this happen. How do they do this? I dunno. If I did, I wouldn't be out in public writing a blog, I'd be doing super secret awesome research somewhere.

Turns out that only the US and a handful of other countries have figured this one out. So while any old fool can make a breeder reactor, the combined science of most nations is not good enough to figure out how to do it.

One last thing. If nuclear power is so difficult, how did so many countries get it? Well, US and Russia developed it. The US gave it to China at some point to balance some power issues with the Soviet Union. The US gave it to several other allies as well. The Soviet union gave it out some, too. China then distributed to crazies like North Korea years later, and Pakistan and India were given it through similar pathways. In other words, it is still pretty difficult to develop.

Hey, I just covered 4 whole things in one post, and managed to get more terrible jokes in. Awesome.

Aww darn, I forgot to include the small amount of original research I did on this topic. Next article

Thanks for reading

-Jason