Eli5, even if they are not the most efficient or powerful things, why are stirling engines not sprinkled everywhere where there is a decent amount of thermal differential? or energy to recapture, Like in power plant cooling systems or other places where there’s lots of “waste heat” as a byproduct.
In: Engineering
The energy you get from most tiny differentials is, well, tiny. The expense to set up and maintain a Stirling engine is not tiny. It often would interfere with the function of the system you installed it on.
Like, at a power plant that waste heat needs to be dumped to avoid things like the plant melting itself or blowing up. A Stirling engine would get in the way of that cooling process. At best, you would just reduce the efficiency of the main turbine, offsetting whatever gains you would have gotten in exchange for more cost to maintain this other not as good engine.
If the energy differential *is* big enough to be worth capturing that energy flow to produce usable energy… there are almost certainly more efficient engines or turbines, and people will just use those.
Because a steam turbine is more efficient.
Most places (most notably gas turbine power plants) that have so much potent exhaust heat use it to power a steam turbine. The exhaust heat of a steam turbine is is too cool to effectively run a Stirling engine.
It’s not about thermal efficiency, it’s about cost. Half of every engineering choice is cost. Sterling engines make low power per unit cost, and there is not market for that.
If there is a significant amount of waste heat, there are other more efficient methods of using it.
Power plants cooling systems sometimes heat water for domestic use or for preheating incoming water used for steam (cogeneration).
Sometimes nothing is installed to save money, or for some other reason (like the additional weight not being worth it in a motor vehicle).
as a general rule, if you want a lot of something, you don’t want to get it from a bunch of little somethings. you can if you have to, but better if you can get it from one big source. when generating power, you get a lot more efficiency from a single big generator than you do from a bunch of little ones. when you factor in the costs of purchase, installation, maintenance, etc., little stirling engines are just not worth it for the additional power.
However hard your “waste” heat pushes on a turbine is exactly how hard the turbine is pushing back on whatever is making the waste heat.
There’s no such thing as free energy. It’s powered by the system before it in the chain, creating a restriction on that system, making it less efficient.
Energy has been always so cheap (even at peak oil prices), that it is simply not worth. It’s now slowly changing not only because the prices go even higher, but also because it can be sold as green solution.
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