Are Stirling Engines the Future of Renewable Energy Storage?

Sponsored by SurfShark VPN. Click the link in the description below. Thanks to the rise of intermittent

renewable

energy

sources, we have seen increased demand for new

energy

storage

technologies such as 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 could be a promising solution? Let's explore the Stirling engine and the

future

of

renewable

energy storage. I'm Matt Ferrell. Welcome to Undecided. I don't want to continue beating a dead horse here, but finding viable energy storage solutions is the only way for intermittent renewable energy generation, such as solar and wind, to solidify as part of the energy mix.

We typically talk about chemical batteries or mechanical storage systems, but we may be able to add the thermal propulsion Stirling engine to that list. It has been innovatively reapplied to become another potential option for energy storage. And the only 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, with combustion and jet

engines

. Unlike these, the Stirling engine does not use steam or fuel. It can operate from absolutely any externally applied heat source, heating, cooling and recycling the same air to provide useful energy 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 in his first parish. His invention was developed to overcome some problems of steam engines, such as operating at high pressure with the risk of explosion, having low efficiency and also requiring a lot of water to operate. An added benefit, since it does not rely on contained explosions like an internal combustion engine, is that the Stirling engine runs quietly. There are three main types of Stirling engines: alpha, beta and gamma, distinguished by how they move air between hot and cold zones.

Which brings me back to my little friend, which is a displacer type Stirling engine. There are five key elements of a Stirling engine: Heat The source of energy: heat. It is where the engine gets all the energy to use in the process, like a solar mirror that concentrates the heat of the sun, a charcoal fire or even a cup of tea. Seriously, a cup of tea...yes, it will only provide a small amount of energy that will be used up quickly as the tea cools, but it works. Just placing this on top of a hot cup of tea sets things in motion.

That heat transfer to the base of the engine brings me to the second key element of a Stirling engine... Gas, also called the working fluid, is used to move thermal energy from the source (the teacup) to the heatsink. of heat. , 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 is just air, but it could be hydrogen, helium, or any substance that remains in a gaseous state when heated and cooled during the process. As the hot air inside expands, it pushes up 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 operate... this toy has one. The alpha configuration has a compression and an expansion piston that are placed inside two separate cylinders. Once the heated gas reaches the top of the chamber, the gas has reached the cooler side and the heat sink... which is the fourth key element. The heat sink This is where the heated gas is cooled before returning to the heat source. The heat sink is usually a piece of metal that releases heat into the air, sometimes into the body of the machine itself.

For medium to high horsepower engines, a radiator is required to transfer heat from the engine to the ambient air. . In this case it is just the top metal plate. The cooled gas then returns to the hot side to repeat the process again, driving the piston inside the machine. Heat exchanger And the last 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 retains the heat released by the hot gas moving inside the chamber.

When the gas recedes, it regains heat again. The heat exchanger is important because it retains heat that would be lost to the environment and, if lost, would decrease the efficiency of the machine. In the case of beta and gamma Stirling engines, they have a working piston and a displacer piston. The first piston fits snugly into the cylinder and converts the expansion energy of the gas into useful work, powering the driving engine. In the beta Stirling engine, both pistons are in the same cylinder, while the gamma configuration has them separated into a cold and a hot cylinder.

There is one important thing we need to understand about a Stirling engine...it only needs a temperature difference between the heat source and the heat sink (where it ends) to operate. In the case of this toy, what do you think will happen if I put it on top of ice water? But before we get to that, I'd like to thank Surfshark for sponsoring this video. I always use a VPN when using public Wifi, but VPNs can be very useful even when you're at home. Many online services use fairly sophisticated commercial segmentation and tracking... a VPN can protect you from that.

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SurfShark offers a 30-day money back guarantee, so there's no risk in trying it out for yourself. The link is in the description below. Thanks to Surfshark and all of you for supporting the channel. So what happens when I put this in ice water? In fact, it will slow down and start turning in the opposite direction. Because? I just reversed which side is hotter. Room temperature air makes the top metal plate the warmest side. It all comes down to the temperature difference between the dishes. In the end, a Stirling engine can run on any energy source, such as combustion fuel, waste heat or solar heat.

The thermal efficiency of Stirling engines reaches values ​​of up to 40%, while the efficiency of similar Otto and Diesel engines is 25% and 35%, respectively. In 1986, for example, the MOD II automobile engine, which used Stirling technology with pressurized hydrogen as the working gas, achieved a thermal efficiency of 38.5%, much higher than that of a spark ignition internal combustion engine. the same power. But where are Stirling engines used? Well, not in many places. You won't see them in something like a car because it takes too long to get them on and off, but the technology is useful in specific cases. Like a cogeneration unit, which combines a Stirling engine with something like a natural gas generator.

The Stirling engine can reuse waste heat from the natural gas generator as a heat source to produce mechanical energy. This is something that can be found in the industrial and agricultural industries. In addition, it is also used in submarines, nuclear plants and even solar energy. In one application, the machine is placed at the focus of parabolic mirrors to convert solar energy into electricity, as in the example of the 1.5 MW Maricopa Solar power plant installed in Arizona, which achieves 31% efficiency. But it is the use of Stirling engines and their incredibly efficient conversion of thermal energy into mechanical energy that can provide another great storage option.

A Swedish company, Azelio,   is already a leading provider of Stirling engine-based renewable energy solutions, now focusing 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, energy can be stored and used for hours, days or even months, helping to address seasonal variability in energy supply and demand. Concentrated solar power plants are the most widespread application of TES, where storage allows them to send electricity 24/7.

The main storage technology used is molten salt thermal storage, which accounts for 75% of TES in 2017. But Azelio has been developing a different approach. Its technology combines Stirling technology with TES, which is charged from solar photovoltaic systems or wind generators. The technology is capable of providing 13 hours of clean, reliable electricity for continuous operation. Additionally, Azelio technology requires no replacements or downtime during service, with an incredible 30-year lifespan. but how does it work? First, energy from concentrated solar, wind or solar photovoltaics is used to heat a phase change material, in this case aluminum, up 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 a Stirling engine, using a heat transfer working fluid. The output of the motor is then connected to an electrical generator to produce electricity with zero carbon emissions. The storage has a capacity for 13 hours of electricity delivered at rated power, and more when output is adjusted to changing demand. The system will also supply heat at 65°C, which is useful for industrial heating. Each unit is composed of a storage unit and a Stirling engine with a maximum power discharge rate of 13 kW and a heat discharge rate of 26 kW, and the heat-to-electricity conversion rate is about 30%.

The modular feature of Azelio's technology provides installations in buildings from 0.1 MW to 100 MW. The company installed a storage facility at the 580 MW Noor Ouarzazate solar complex in Morocco in March last year, and just last December began installing its technology at one of the world's largest solar parks in Dubai, where will be part. of a mini-grid composed of panels and batteries. There are also initial deals in the works with Jet Energy in Francophone Africa and SVEA Solar in Sweden. So far, all these agreements represent 426 MW of power with 5.4 GWh of storage capacity. All this provides a solid basis for starting serial production, which is planned for the end of this year.

But how does it compare to other energy storage solutions? Data is still somewhat limited, but according to a life cycle assessment by the Swedish research institute RISE, Azelio's technology is (23 g CO2/kWh) 29% lower in CO2 equivalent emissions than a battery system lithium ion. Even considering that the batteries were only replaced once over a 25-year life cycle (32 g CO2/kWh), and 96% less than a high-efficiency diesel generator (523 g CO2/kWh). While it appears to be a promising solution, an effective cost comparison with other storage technologies will depend on the startup's projects and its technological development in the coming years.

My fascination with this little guy led me down an interesting path that I didn't expect. I had no idea this type of technology was being used as a potential clean energy storage solution until I started researching. 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 being reused in new ways like this. What do you think? Do you know of any other unique storage solutions that I haven't covered on the channel yet? Jump into the comments and let me know. If you liked this video, be sure to check out one of the ones I linked here.

Be sure to subscribe and hit the notification bell if you think I've earned it. And as always, thanks to all my sponsors and two new members + followers, Mark Zeman and Marat Dyatko. I hope nothaving destroyed their names. Thanks for watching and I'll see you next time.