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Click on the link in the description below Thanks to the rise of intermittent
renewable energy sources, we’ve seen increased demand for new energy
storage technologies, like batteries, pumped storage hydropower, and flywheels.
But what if I told you that this little toy, a 200-year-old invention, combined with
thermal energy storage might be a promising solution? Let’s explore the Stirling Engine
and the future of renewable energy storage. I’m Matt Ferrell. Welcome to Undecided. Not to keep beating a dead horse here, but finding
viable energy storage solutions is the only way for intermittent renewable energy generation like
solar and wind to solidify themselves as a part of the energy mix. Typically we’re talking about
chemical batteries or mechanical storage systems, but we may be able to add the
thermal-powered Stirling engine to that list. It’s been reapplied in an innovative way to become
another potential option for energy storage. And the whole reason I went down
the path of making this video is because of this little toy,
but I’ll get to that in a minute. Engines have been powering the world
since the Industrial Revolution, first with dirty, coal-powered
steam engines, and more recently, combustion and jet engines. Unlike those,
the Stirling engine doesn‘t use steam or fuel. It can run from absolutely any
source of heat that‘s applied externally, heating, cooling, and recycling the same air to
provide useful power that can drive a crankshaft. This engine was developed by the Reverend Robert
Stirling, when he was 26 years old and had just been ordained to his first parish. His invention
was developed to overcome some problems of steam engines, like operating at high-pressure with
a risk of explosions, having low efficiency, and demanding a lot of water to operate as well.
An additional benefit, since it doesn’t depend on contained explosions like an internal combustion
engine, is that the Stirling engine runs silently. There are three main types of Stirling engines:
alpha, beta, and gamma, which are distinguished by how they move the air between the hot and cold
areas . Which brings me back to my little friend here, which is a displacer-type Stirling engine.
There are five key elements of a Stirling engine: Heat The power source: heat. It’s where the engine
gets all the energy to be used in the process, like a solar mirror concentrating
heat from the sun, a coal fire, or even a cup of tea. Seriously, a cup of
tea ... yes, it’s only going to provide a tiny amount of energy that would be quickly
used up as the tea cools down, but it works. Just placing this on top of a hot cup of tea
gets things moving. That heat transferring into the base of the engine leads me to the
second key element of a Stirling engine... The gas, also called working
fluid, is used to move heat energy from the source (the cup of tea) to the
heat sink, which I’ll get to in just a second. The working fluid is sealed in a chamber inside
the engine, and in this case it’s just air, but it could be hydrogen, helium,
or any substance that remains in a gas state when heated and cooled during the
process. As the heated air inside expands, it pushes upwards against a displacer
piston, which is the third key element. Pistons Although there are different
types of Stirling engine designs, they usually have two pistons to work ...
this toy has one. The alpha configuration has a compression and an expansion piston that
are placed inside two separated cylinders. Once the heated gas reaches the top of the
chamber, the gas has reached the colder side and the heat sink ... which
is the fourth key element. The Heat Sink This is where the heated gas is cooled before
going back to the heat source. The heat sink is usually a piece of metal that releases heat into
the air, sometimes the body of the machine itself. In the case of medium to high power engines,
a radiator is required to transfer the heat from the engine to the ambient air. . In this case
it’s just the top metal plate. The cooled gas then returns to the hot side to repeat the process all
over again, driving the piston inside the machine. Heat Exchanger And the final key element is the
heat exchanger or regenerator. There isn’t one on this little guy, but a heat
exchanger is usually placed between the heat sink and the heat source, inside the sealed
chamber. It holds heat released from the hot gas moving inside the chamber. When the gas
moves back, it recovers heat from it again. The heat exchanger is important because it holds
the heat that would be lost to the environment, and if lost, would decrease
the efficiency of the machine. In the case of the beta and gamma
Stirling engines, they have a work piston and a displacer piston. The first
piston fits tightly into the cylinder and converts the gas expansion energy into
useful work, driving the engine it’s powering. In the beta Stirling engine,
both pistons are in the same cylinder, while the gamma configuration has them
separated into a hot and a cold cylinder. There’s one important thing to understand
about a Stirling engine ... it just needs a temperature difference between the heat source
and the heat sink (where it ends up) to work. In the case of this toy, what do you think
will happen if I put it on top of ice water? But before I get to that, I’d like to
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to try it out for yourself. Link is in the description below. Thanks to Surfshark and
to all of you for supporting the channel. So what happens when I put this onto ice
water? It will actually slow down and start turning in the opposite direction. Why? I’ve
just reversed which side is the hotter side. The ambient room temperature air makes the top
metal plate the warmer side. It all comes down to the temperature difference between the
plates. In the end a Stirling engine can be powered by any number of sources, like a
combustion fuel, waste heat, or solar heat. The thermal efficiency of Stirling
engines reaches values up to 40%, while the efficiency of similar Otto and Diesel
engines are 25% and 35%, respectively. In 1986, for example, the MOD II automotive engine,
which utilized Stirling technology with pressurized hydrogen as the working gas,
reached a thermal efficiency of 38.5%, much higher than a spark-ignition internal
combustion engine of the same power. But where are Stirling engines used? Well, not
many places. You’re not going to see them in something like a car because it takes too much
time to ramp them up and down, but the technology is useful in targeted cases. Like a cogeneration
unit, which combines a Stirling engine with something like a natural gas generator.
The Stirling engine can repurpose the natural gas generator’s waste heat as the heat source to
produce mechanical energy. This is something that you can find in the industrial and agricultural
industries. On top of that, it’s also utilized in submarines, nuclear plants, and even solar power.
In one application, the machine is placed at the focus of parabolic mirrors to convert solar
energy into electricity, as the example of the 1.5MW Maricopa Solar power plant installed
in Arizona, which reaches 31% efficiency. But it’s the use of Stirling engines and their
incredibly efficient conversion of thermal energy into mechanical energy that may provide another
great storage option. A Swedish company, Azelio, is already a leading supplier of Stirling
engine-based renewable energy solutions, which now focus on distributed and
dispatchable solar electricity, using the Stirling engine for
Thermal Energy Storage (TES). In TES systems, thermal energy is
stored by heating or cooling a material, so that the stored energy can be used later,
either for heating and cooling applications or for power generation. Depending on
the technology, the energy can be stored and used for hours, days, or even months,
which helps to address seasonal variability in energy supply and demand. Concentrated Solar
Plants are the most widespread application of TES, where the storage enables them to
dispatch electricity 24/7. The main storage technology used is Molten Salt Thermal
Storage which accounts for 75% of TES as of 2017. But, Azelio has been developing a different
approach. Its technology combines Stirling‘s technology with TES, being charged from
solar PV systems or wind generators. The technology is capable of providing 13
hours of clean and reliable electricity for continuous operation. In addition, Azelio‘s
technology requires no replacements and zero down-time during servicing, with
an incredible lifespan of 30 years. But how does it work? First, energy coming from concentrated
solar power, wind or solar PV is utilized to heat up a phase change material,
in this case, aluminum, to 600°C. Reaching this temperature causes the material
to change its phase state, maximizing the energy density to store that energy for a very long time.
This stored thermal energy is used to power up a Stirling engine, using a heat transfer working
fluid. The output of the engine is then connected to an electric generator to produce electricity
with zero carbon emissions. The storage has a capacity for 13 hours of electricity delivering at
nominal power, and longer when adjusting output to shifting demand. The system will also deliver heat
at 65°C, which is useful for industrial heating. Each unit is composed of a storage
unit and a Stirling engine with a peak power discharge rate of 13
kW and a heat discharge of 26 kW, and the conversion rate from heat
to electricity is around 30%. The modular feature of Azelio‘s technology provides
building installations from 0.1 MW up to 100 MW. The company installed a storage facility in the 580 MW Noor Ouarzazate solar complex
in Morocco in March of last year, and just this past December began to install
its technology in one of the world‘s largest solar parks in Dubai, where it will be part of
a mini-grid composed of panels and batteries. There are also early deals in the works
with Jet Energy in Francophone Africa and SVEA Solar in Sweden. So far
all of these arrangements account for 426 MW of power with 5.4 GWh of
storage capacity. All this provides a solid base to start series production,
which is scheduled for later this year. But how does it stack up to other energy storage
solutions? The data is still somewhat limited, but according to a Life Cycle Assessment
made by the Swedish research institute RISE, Azelio‘s technology is (23 g CO2/kWh) 29%
lower in CO2-equivalent emissions than a Li-ion battery system. Even when considering
that the batteries were only replaced once over a 25-year lifecycle (32 g CO2/kWh),
and 96% lower than a high-efficiency diesel generator (523 g CO2/kWh). While it
looks to be a promising solution, an effective cost comparison to other
storage technologies will depend on the start-up‘s projects and its technology
development over the next few years. My fascination with this little guy sent me
down an interesting path I wasn’t expecting. I had no idea this kind of technology was
being used as a possible clean energy storage solution until I started digging around.
Is the Stirling Engine the answer to the future of renewable energy? The jury
is still out, but it looks promising. I love seeing old technologies getting
repurposed in new ways like this. What do you think? Do you know of
any other unique storage solutions that I haven’t covered yet on the channel?
Jump into the comments and let me know. If you liked this video be sure to check out
one of the ones I have linked right here. Be sure to subscribe and hit the notification
bell if you think I’ve earned it. And as always, thanks to all of my patrons and
two new supporter+ members Mark Zeman and Marat Dyatko. I hope I didn’t butcher your names. Thanks
for watching and I’ll see you in the next one.
No
Good heat engines, i.e. stirling engines etc., running on solar power could in principle higher efficiency than solar cells and I suspect that they do in practice as well.
The problem is that they're kind of expensive, and the solar plants in Spain that use central towers heated by sunlight don't achieve quite as high MW/m2, taking into account the total plant area, as solar farms using panels. But then, you obviously get power at night with this solution, so it might be worth it.