The Engineering Challenges of Renewable Energy: Crash Course Engineering #30

Engineering has given a lot to the world. It’s transformed the nature of work, improved
sanitation and helped create vital infrastructure. The bad news is that to power the tools and
processes behind those developments, we’ve
relied on non-renewable fuels – the kind that get produced at a much
slower rate than we use them. As the name implies, non-renewables won’t
be around forever. Resources like oil and natural gas might be
gone in just half a century. And using them has been, frankly, pretty terrible
for the environment. 87% of the harmful carbon dioxide emitted by humans in the last 50 years has come from burning fuels such as coal, oil, and natural gas, known collectively as fossil fuels. It’s been terrible for the atmosphere and oceans,
and is changing our climate in dangerous ways. Whether we like it or not, we’re gonna have
to find new ways to power our world. [Theme Music] Despite their terrible effects on the environment
and limited supply, for now, non-renewables do
a really good job of meeting our energy needs. In 2017, 80% of the power used in the United
States was supplied using fossil fuels. And the need for energy doesn’t appear to
be shrinking any time soon. Another 9% was delivered from nuclear fission,
the process of splitting atoms, which releases
far less CO2. Unfortunately, fission produces radioactive
waste and also relies on non-renewable fuel
sources such as uranium and plutonium. All of these methods operate on broadly the
same principle, essentially operating as a
heat engine. A working fluid, often water, is heated by
the fuel to expand and do work, turning the
blades of a turbine. The turbine is connected to an electrical generator
that converts the rotational motion of the blades into
electrical power, which is then fed into the grid. So what about that remaining 11% of power? That came from renewable energy sources – the
kind that are generated about as fast as we use them. Some of the major renewable energy sources
come from processes that are naturally occurring
on Earth: wind power; solar power; hydropower – which is
based on flowing water; and geothermal power,
which uses the heat of the Earth deep underground. None of these sources are things we’ll run
out of – we have a good few billion years
left of sunlight, for example. And what’s more, renewable energy tends
to release fewer harmful byproducts, like
carbon dioxide, into the environment. Take hydropower, for example, which converts
the kinetic energy from the motion of running
water into electrical power. In a fast flowing river, a run-of-river power plant
diverts part of the river’s flow, sometimes through
a tunnel, to turn the turbinesof a generator. That works well in some places, but the problem
with this approach is that it’s tricky to control the
generation of energy to meet demand. You don’t want to put lots of power into the grid when
it won’t get used, and you want to be able to ramp up
the supply when the demand suddenly spikes. Like during the halftime break when the English
football team – that’s soccer to you Americans –
played Colombia in the 2018 World Cup. A huge number of people in the UK opened their
refrigerators to grab a drink or a snack, causing
the compressors inside them to turn on. Then there were the people who’d already
had a bunch of drinks. All those people simultaneously flushing their toilets during the break created an increased demand for power on the local pumping stations that maintain pressure in the water system. The total increase in demand was measured
to be 1200 megawatts. That’s an extra demand for power equivalent
to several power plants! With fossil fuels, you can control the amount
of fuel being burned, and therefore the amount
of power being produced. Run-of-river power plants struggle with this
because the amount of power they generate
depends on the flow of the river, which in turn depends on things like the rainfall
during the time period and even the temperature –
both things we can’t control. To get around this, the more common form of
hydropower is a hydroelectric dam. In this case, you can install a dam that floods
an area and creates a huge reservoir of water. The water then falls through the generator’s
turbines at the bottom of the dam, which turn
the water’s kinetic energy into power. If you install an intake valve that opens
or shuts to control the water flow through it, you can even manage the production of energy to
meet the changing demands of the electrical grid. Unfortunately, flooding an area with water
isn’t consequence-free. Changing the environment so suddenly and preventing
the natural flow of water downstream can have
devastating consequences for the local ecology. There’s also the risk of the dam breaking
if it was built improperly. Despite those challenges, hydropower has been
enormously helpful. In recent years, it’s produced as much as
16% of the world’s energy and up to 70%
of all the world’s renewable energy. The other renewable energy source that works
very similarly to hydropower is wind power,
which also uses turbines. The main difference is that the fluid doing
work on the wind turbines is air instead of
water. One of the biggest engineering challenges
here is designing the turbine blades to efficiently
extract energy from that air. As we saw with fluid mechanics, predicting
the flow of a fluid around an object can get
seriously tricky! Blades have to be engineered to withstand the stress
they’re subjected to while also allowing the wind to
efficiently rotate them to power the generator. It’s as complicated as designing an airplane
wing. Once again, you run into the problem of demand:
you can’t control the strength of the wind to increase
or decrease power generation as you need it. Even if that were possible, you’d still have to
transport it from the sparsely populated, open
plains where the wind blows more easily, to dense urban centers with low amounts of
wind but high demand for power. Transporting that power becomes even trickier
over long distances because you lose some energy
as the electricity travels through the wires. For that reason and others, engineering considerations
often play a big role in deciding where wind farms (as
a collection of turbines is known) should be built. So wind power has only generated 4% of the
world’s total power supply in recent years. Location also plays an important role in another
renewable energy source: geothermal power. Like conventional power plants, geothermal
power relies on steam as the working fluid
on the turbines connected to the generator. But in this case, you don’t need fuel to
generate the steam. You can drill into underground deposits of hot, volcanic rocks, normally near the Earth’s tectonic plate boundaries, to use them as a heat source for a power plant. Then, all you need is to pump water to that
location and create another channel for steam
to rise through to do work on the turbines. The biggest problem comes with setting up
a geothermal power plant in the first place. It can be expensive to drill and explore for
underground conditions that are exactly right, and is only really possible in certain parts
of the world, like Iceland and Italy. But there’s one source of renewable energy
that’s so abundant and easily accessible you only have to step outside on a bright
sunny day to see it: solar energy! In fact, the amount of sunlight the Earth
receives in just a single year is twice the total amount of energy that will ever
be extracted from fossil fuels and the uranium used
in nuclear fission, combined. The challenge is finding efficient ways to
harness that energy, because turning sunlight
into electricity isn’t simple. The most promising technology we have is called
the photovoltaic, or simply, PV cell. Most people know them by the name given to
many cells arranged together: solar panels! Unlike everything else we’ve looked at,
there’s no trace of a turbine here. Instead, as we saw when looking at semiconductors, solar panels use two different semiconducting pieces to set up an electrical field that biases the movement of free electrons inside the material in a particular direction. In short, the materials encourage an electrical
current to flow when they receive energy, which then travels through the circuit delivering
power to whatever’s connected to the PV cell. That means solar panels can deliver power
directly to the grid. Between that and the abundance of sunlight,
it seems like there shouldn’t be an energy
shortage problem at all. But, as we’ve seen for the other energy
sources, costs, fluctuating demand, location,
and transmission all factor in here. For starters, solar cells aren’t all that
efficient. The very best solar cells can convert 40%
of the energy they absorb into electrical power, but they’re expensive to produce because of
the high quality of silicon needed in manufacturing,
among other reasons. On average, industrial PV cells are about
17% efficient. Once you factor in the cost of making the cells and energy storage, solar power ends up being anywhere between 3-6 times as expensive to produce as that from fossil fuels. Increasing solar panels’ efficiency would
bring this down dramatically. Another big challenge with solar power is that, like with the hydroelectric dam, you need a way to store energy to control the production in line with power demand. You won’t generate much solar power on a
cloudy day, whereas you might have a surplus
on sunny days. But you can’t store sunlight directly! Instead, engineers are working on ways to
temporarily store that extra solar power. These include solutions like batteries, or even
pumping water up a column to later give up its energy
as hydropower during periods of high demand. Once again though, efficiency plays a big
role in making both of these methods a suitable
form of energy storage. Despite the efficiency and storage problems,
there is one major advantage to solar panels:
they can be deployed pretty much anywhere. Rather than having to transmit power across
long distances, solar panels can simply be installed
on smaller scales close to areas of demand – even on the roof of an individual home. But manufacturing the panels themselves brings
its own set of issues. One of the raw materials used to currently make solar
panels is quartz, which has to be processed to produce
the high quality silicon needed for making PV cells. This itself is an energy intensive process,
which offsets some of the total energy production
of solar panels across their lifetime of usage. Even worse, processing quartz can often produce toxic byproducts like tetrachloride, which can end up spilling into the environment and causing damage to soil. That all sounds a little bleak, but the most
difficult challenges in engineering are often
the most important ones. In fact, the National Academy of Engineering
in the US has identified making solar energy more economical as one of the Grand Challenges that engineers in the 21st Century need to solve. Future engineers have lots of ways to contribute
towards making solar more feasible. Currently, researchers are looking at new
storage systems, such as using solar power
to drive hydrogen fuel production, which can be burned later on with no
carbon dioxide emissions. More on that next time. Engineers are also introducing new materials into the production of solar panels, and improving the ways in which PV cells themselves are linked and arranged on the panels. There are even experimental methods being
developed that use new structures on a molecular
level, called nanocrystals. These increase the amount of energy given to the
electrons in the material when ligh is absorbed
instead of losing the energy as heat. That could drive the efficiency high enough to make it
economically competitive with current power sources
and increase the adoption of solar worldwide. So there are lots of challenges ahead in bringing
renewable energy sources to the forefront
of electrical power production. But that’s all the more space for future
engineers to have an impact and create new
solutions to the world’s energy needs! In this episode we looked at renewable energy
sources and why we need them. We looked at how hydropower, wind, geothermal,
and solar power are used to produce electricity, some of the challenges faced in doing so,
and the areas engineers are working on to
make their use more widespread. In our next episode, we’ll see how engineers
have moved beyond natural processes, to invent
entirely new ways of generating power. Crash Course Engineering is produced in association
with PBS Digital Studios, which also produces Eons,
a series that journeys through the history of life on Earth. With paleontology and natural history, Eons
takes you from the dawn of life, through the
so-called “Age of Dinosaurs”, and right
up to the end of the most recent Ice Age. Crash Course is a Complexly production and
this episode was filmed in the Doctor Cheryl C.
Kinney Studio with the help of these wonderful
people. And our amazing graphics team is Thought Cafe.


  1. Levelized cost of energy for solar is nowhere near that x3 more expensive than fuel. For most of the countries on earth fuel or gas is not free and needs to be imported. Utility scale solar without subsidies is being installed nowadays at levelized cost of electricity (LCOE) of around 40$/MWh which is well in grid parity. Gas combined cycle and coal are in the range of 40-70$/MWh. Residential rooftop solar are at 70$/MWh and people are installing it because even at that price is economically profitable considering all the distribution costs, utility companies profit and taxes on top of grid electricity production price.

    The answer is simple: install LOTS of industrial-scale solar and offshore wind FAST + pumped hydro energy storage, meanwhile maintain installed nuclear (those are already paid for!).

  2. Unfortunately as it is, Solar, Hydro and wind power all more expensive AND don't produce as much power as Coal, Gas and Oil.
    And until that time companies like Shell and EXXON aren't going to go for it.
    Make it cheaper and then they will.

  3. 1:39 This was a surprising choice for a visual. That's sarcasm by the way. Is anyone viewing these videos before they're published?

  4. Why'd it show a wind-turbine for nuclear-power? That's the second time in a month Though Cafe dropped the ball. ¬_¬

    Another problem with mass-producing solar panels is that we are running out of (usable) sand. No joke. (It shouldn't be a problem since they don't need to be the same kind of sand, but tell that to the people collecting it as cheap as possible.)

  5. The problem is that you should be saying this in mandarin, Cantonese, and Hindi considering they have trouble controlling their particulate matter before worrying about CO2. Besides CO2 is not a pollutant it feeds plants which in turn provide oxygen. How many animals can live without oxygen? CO2 has been higher in the past than it is today. It’s always been apart of the ambient air so I’m not sure how you can argue it’s a pollutant. If you burn up everything then you are left with CO2. We’re living longer now today I don’t see why we would make ourself suffer investing trillions into the generation and distribution sector when we’re so far in debt today millennials will probably not be as wealthy as their parents. Face it the millionaire screwed the middle class into becoming billionaires. Now they want to squeeze more out of us in the form of a CO2 tax. Just remember anytime a power plant adds a control device, the consumer is the one who ends up paying for it. Solar today is too volatile it can drop off in an instant then a coal fire boiler is started up just to offset the loss of solar. PBS makes crash corse unbearable with its political agenda. Is water vapor a pollutant. It could kill you if you breathed to much in.

  6. That diagram of the dam was terrible.

    You don't take water from the bottom of a dam but from the top where it has far more potential energy.

  7. You forgot one more kind of renewable energy. Its uses sun power too like solar panels but unlike solar panels it uses infrared light to boil water into steam which turns a generator. To achieve this they deploy thousands of large mirrors which reflect and concentrate the suns heat energy aka infrared to produce energy.

  8. why not enter the subject of the AMOUNT of oxygen created over how much is used/abused/converted/transformed to things WE CANT breathe..
    90% of our energy concerns tend to be Storage. Holding it until its needed.

  9. I have a solution to renewable energy and it is "Fifteen Million Merits".

    If every single human is required by law to ride a bike generator to supply part of his energy daily needs. That would cut down on grid energy usage but save Americans from heart attacks, diabetes and stroke. A win win i think.

  10. OTEC should be big in the future;
    Ocean thermal energy conversion uses the temperature difference between cooler deep and warmer shallow or surface seawaters to run a heat engine and produce useful work, usually in the form of electricity.

  11. Solar Power cannot be used anywhere. Of course you can mount panels everywhere but you can also build a hydroplant (almost) anywhere or a geothermal plant anywhere. They just wont be reasonably efficient. Solar really is not a solution to the distrubution problem quite the contrary. Big solar farm in deserts close to the equator are a major logistical challange and small distributed solar is only feasable in places like california not so much where i live though. And large parts of europe in general.

  12. This was the best Pro-Con analysis of renewable energy I have seen. As a student engineer, it's very easy for Science, Math and other engineer students/professionals to easily suggest that solar fixes every problem known to man, without knowing or considering the consequences of also implementing it.

  13. i had a feeling solar panels wouldnt pump out as much juice as it takes to make them. on that topic, i think the efficiency will be found in quantum biology.

  14. Cost reductions for solar and wind are kinda yesterday's news. These prices are plummeting already and are set to kill fossil fuels on a per KWh basis in the next few years.
    The main challenge which you barely touch on is intermittency and geographical limitations on solar and wind. Solutions like high voltage DC grids, distributed storage using various technologies, smart grids and AI-driven demand management are the way forward here. These are a big juicy engineering challenge that you should really cover on this channel.

  15. You really sold geothermal incredibly short. First, the graphic you used was for a design that hasn't been widely used for decades now. Yes, a few plants are still built like that, but the vast majority are binary cycle plants, where the hot brine from the geothermal resource is run through a heat exchanger to flash boil a secondary working fluid (typically pentane, butane, or another refrigerant with a low boiling point) to run a turbine. The main benefit obviously being that you can extract much cooler resources and still produce commercial amounts of power.
    Also, mentioning production from Iceland and Italy… and then leave out that the state of Nevada produces more geothermal power (in terms of gross megawatt hours produced) than Iceland and California produces more than Nevada, Iceland, and Italy combined. Even Utah and Idaho give Italy a run for its money. This isn't some niche power source only suitable for a few small nations. And, with the development of enhanced geothermal systems, where man made geothermal reservoirs can be created, instead of having to find a naturally occurring one, the only barrier to geothermal being viable option for baseload power production (a term conspicuously absent from this entire presentation, the ability to produce power round the clock) is drilling costs (because everywhere has pockets underground hot enough to create a geothermal heat source, if you drill deep enough).

  16. This video did not give nuclear energy the credit it desrves.
    There is no way we could adapt renewable energy on time to save the eart, but nuclear is there, ready to reduce our emmisions enough to give renewable and fusion the time they need to become mainstream.

  17. Very good explanation and demonstration of renewable energy. Burning of fossil fuels the problem is not CO2 that is a natural safe gas and theory of global warming as by political agenda IPCC is a dubious one so don't buy into that. Burning of fossil fuels the problem is the smog created NO2, SO2, low level ozone and particulates and also the general pollution from oil spills etc. This kills more than smoking by saying CO2 and global warming you minimize the real issues.

  18. Just to add Nuclear power the issue is not CO2 emissions it is the serious byproducts and toxic waste and obviously if the thing meltdown the effect that will have on the country /world. Again by focusing on a political theory you can minimize and smoke screen the real issues.

  19. The "non-renewable" nuclear fuel doesn't have only centuries worth of fuel though it has many millenniums worrth, isn't that worth mentioning?

    Should totally do a nuclear engineering episode!

    Also Fission pretty much by definition doesn't release C02. Saying far less is a bit of an understatement.

    I love these videos and I love crash course, just trying to be more positive about all of our future energy options.

  20. wow, is hydrogen directly produced from solar power? or via pv cells generating electicity anyway?

  21. Alot of people are confused with the difference between Nuclear Fission and Nuclear Fusion.

    We humans have been using nuclear fission to create energy in power plants for decades.

    Nuclear Fusion is still being experimented on and has not been viable yet but it is the future.

    Nuclear fission reactors require specific fuel sources like uranium or plutonium. Which is a limited resource.

    Nuclear Fusion, in theory, you can use any kind of fuel as long as it is matter or molecules. You can use bananas, Nitrogen atoms, dandruff, trash even grains of sand to create energy. Because you just need to use two atoms from any of those items and smash them together and they go BOOM regaurdless of fuel source. Atoms like to repel each other so when you force them to fuse massive energy is released.

    Does anyone remember "Back to the futures" Mr Fusion Delorean?

  22. If the USA goverment is being controo by big pharma and oil companies it will be hard to have renewable energy. Specially if the USA keep puting taxes on new solar power equipment like they are doing in Florida. We should have alot of renewable energy sources if oil companies wouldn't controo the goverment for(war) their own benefits…

  23. Where did you get the 3x to 6x more expensive number? 7:45 That seems rather outdated. Power companies are building huge solar farms and if it was 3x more expensive that would be a very bad blunder.

  24. I MAKE POWER for a living and as this is an informative video, it misses a lot of big points and because of that is misleading…….
    1. biomass is not mentioned once however its a huge renewable provider and a sustainable one at that
    2. trash burning power plants aren't once mentioned however it is actually the largest contributor to the 11% figure of renewables on the grid (they consider trash a renewable fuel source, go figure)
                     these two are the biggest contributors to the mere 11% of power produced however they're not mentioned once.  and the figures given for solar contribution are completely false


    3. RENEWABLE ENERGY IS HEAVILY SUBSIDIZED TO APPEAR TO BE SUSTAINABLE.  TAX DOLLARS PROP UP RENEWABLE ENERGY MARKETS WITH "RENEWABLE ENERGY CREDITS" these are bought sold and traded but paid for by taxpayers.  big corporate knows this and chases the tax monies that are awarded for renewable power produced. 

    EXAMPLE—— so your a solar farm owner…. you produce 1mw of power an hour, local government gives you a credit for making that megawatt….. as more solar fields and windmills and other subsidized renewable sources are constructed, the renewable credit (only thing making renewable profitable) is worth less and less because theres more and more hands in the honeypot.  these renewable producers shut down or go out of business without subsidization.  so the only thing keeping renewable in business is YOUR TAX DOLLARS.  renewable sources cannot compete with traditional fossil fuel plants because they do not and will not produce enough to be self sustaining. 

    GOVERNMENT ALSO SUBSIDIZES THE CONSTRUCTION OF RENEWABLES.  if your a company building windmills or solar panels (in china) the US government sends you a check to do so.  if your a company that buys the stuff from china, the US government give ya a rebate too.  so renewables are based on fictitious numbers.  even with the heavy handicaps given to renewable its still highly unsustainable.

      don't even get me started on the carbon footprint associated with the construction of these things.  the sad truth is that natural gas fired gas turbines are and will be the most efficient way of turning a generator for all of our lifetimes.  if you play games with numbers and throw money at renewables it still doesn't even come close to what can be produced by natural gas.  we have a abundance of this fuel and they find more of it all the time despite what is said in the videos.  our world is becoming more and more efficient and the answer isn't in a totally renewable world.  the answer is a harmony of renewable and highly efficient fossil fuel plants,  that with an overall lower demand caused by more efficient appliances and energy saving measures in homes and industry we will sustain the human race for as long as we live on this planet.  don't scare yourself with the hype.  if anyone wants to learn more feel free to dm me

  25. Solar can't feed directly into the grid; inverters hardly have perfect efficiency and play havoc with grid power quality. Better to use solar collectors, hydro, wind, geo and nuclear in concert rather than bandwagoning on a technology that is far from ideal for most of the world. I, for one, would rather save my semiconductors.

  26. @CrashCourse check your facts at 8:00. Solar is not x3 to x6 times more expensive than fossil fuels! The cost of Solar has fallen so much in the last 10 years that it is CHEAPER than Coal! This has been the case for a very long time now and is continuing to get cheaper.

  27. Your very clear bias against non-renewables is ironic given the large number of plastic products in your background.

  28. Has CC covered storage and transmission of power? I remember as a teen wondering why batteries weren't used. It wasn't until college that i learned that isn't just about generating power but also the voltage and amperage. (How much and how strong the electrical power coming to you) In this is a Crash Course, but those things play a big part in power generation.

  29. Who is this speaker? You never show her name or why we should be listening to what she says. Please include the name and title/field of work your presenters are in if you want them to have any credibility. For all we know, as the audience, you could have just picked up this good lookin' brown girl off the street because it would attract more views. Obviously I'm sure that's not the case and I imagine she's an engineer of some discipline, but those new to the channel don't know who she is.

  30. @ 1:40 a wind turbine used by mistake when you was talking about steam engine. Use steam turbine animation would be better

  31. Hi guys. I was working control for the England V Columbia game and this weekend we dealt with just less than 50% renewables on the GB system. Any questions about how we manage renewables on the system let me know. Geography, asynchronous machines etc.

    Else if people want more I suggest a free download of MacKay's Sustainable Energy Without the Hotair.

  32. Renewable Energy creates more pollution and harm to environment than fossil fuels and nuclear. Solar is expensive clearing land and killing animals and reptiles. Solar is unreliable and not sustainable, so people will burn wood and coal in each individual home to compensate for what solar lacks. What will be done with spent solar paneling ? What is used in the process of the panels ? The renewable energy will kill off more land, trees, animals, and create more pollution. Fact.

  33. 7:24 For Solar PVs, transmission is not of a problem, at least in a residential/commercial setting where power is utilized where it is generated. Of course, transmission is a problem for all types of larger scale utility scale power generation.

  34. The thing about wind and solar is that they tend to compliment each other. If it's cloudy then it's probably also windy and clear skies might not have a lot of wind. You can also off set the issues with good meteorological knowledge, if you know the weather patterns of an area you can use that to compensate. Oceans for example usually have strong winds making them excellent for wind farms and this is how Denmark generates almost half of it's yearly energy usage with wind power alone. And it also turns out that you can supply peak demands with wind and solar since the amount of wind blowing changes throughout the day just like sun exposure. Again by choosing your location cleverly you can exploit natural differences.

  35. When you burn hydrogen, you create water vapor, or H2O (g), which is actually a far worse greenhouse gas than CO2 and has contributed much more to the Earth's warming than CO2 ever will…how do we solve this problem?

  36. Everything has its challenges, it is normal. Whenever you hear green energy isn't feasible don't believe it because it is a lie.

  37. LIES! as Lazard 2018 study shows, levelized cost of PV utility scale farm is lower than natural gas power generation(cheapest fossil fuel)

  38. Where I grew up we had the potential to produce all 4 forms of renewable energy. There was allot of open space and many days of cloudless skies for solar. There were almost always breezes and often wind especially on the local volcano. That's right a local dormant volcano which meant we had access to geothermal in fact our water needed to be placed in water towers to cool. Finally we had mountain streams rivers and damns which could have been used for hydro-electric power. Sadly the project to place wind turbines on our local volcano was sabotaged presumably since the local power producer would potentially lose control of controlling power generation and or its profits from it would drop since it wouldn't be able to keep prices higher. I believe that is why none of the other potential sources were pursued.
    We did get a coal fire plant but its electricity all went to California mostly LA hundreds of miles away. On the bright side the coal produced nearby and used in the plant is some of the cleanest coal anywhere.

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