Technology Blog Post: Power Generation Past, Present and Future

In the engineering world, it is said "Humanity keeps finding more efficient ways to generate steam". There is some truth to this as our daily lives rely on constant energy and electricity which, consequently, is primarily generated by turning water into high-pressure steam. This so called "Steam Power Cycle" is more colloquially known in engineering circles as the "Rankine Cycle". With that in mind, what exactly is the Rankine Cycle?

The Rankine Cycle is an idealized thermodynamic process used to describe typical steam power generation. A basic Rankine cycle will contain a pump, boiler/steam generator, a turbine and a condenser. The following steps occur in the basic Rankine Cycle ...

1. Isentropic Compression (Pump): Feedwater is pumped from the outlet of the condenser (lower pressure) to the inlet of the boiler (higher pressure). This process generally does not require much work. Due to the added energy, this generally comes with a temperature increase.
2. Constant Pressure Heat Addition (Boiler/Steam Generator): The feedwater undergoes boiling followed by superheating (Making the steam hotter and drier than if it was at its boiling point of 100C).
3. Isentropic Expansion (Turbine): The superheated steam is sent through the turbine where the steam expands and energy is extracted. This is the main "Power Generation" phase of the cycle. Due to the extraction of energy, turbines reduce the pressure of the steam greatly.
4. Constant Pressure Heat Rejection (Condenser): The low-pressure steam is cooled and waste heat is rejected so that feedwater (in liquid form) can be sent back to the pump. The cooling is achieved by an external loop involving a cooling tower or river typically.

Note that this assumes an idealized thermodynamic process. However, per the second law of thermodynamics, entropy ALWAYS increases in any thermodynamic process (dS > 0)! This leads to the concept of irreversibilities. A reversible process means that a process can return to its original state regardless of which part of the process you started with. However, irreversibilities exist such as friction, fluid drag, mechanical efficiency, and thermal efficiency leading to entropy increasing.  Furthermore, pressure drops will be experienced in both the boiler and the condenser. Therefore, this leads to the Real Rankine Cycle in which each process is irreversible. 

Now, what are the different methods in which we produce power? In today's world, humans utilize a mix of non-renewable and renewable power generation methods. The most commonly known energy production method is oil and gas or even more commonly known as fossil fuels. It is readily available, generally cheap and is easy to transport; it is also particularily useful for cold climates. The problem is the burning releases harmful emissions into the atmosphere known as greenhouse gases. These greenhouse gases reflect sunlight back to the earth causing additional unintended heating. This is the main problem with non-renewable energy generation.

As for renewable energy generation, several methods of power generation have become mainstream. Nuclear, solar, wind, hydrogen and geothermal are all different technologies humans have attempt to refine and master, particularily in the past couple decades with the accelaeration of global warming. The world is trending towards an entirely renewable energy grid as we attempt to achieve a "Net-Zero" future. The most promising of the renewable energy technologies that currently exist is nuclear power. While it is without a doubt the cleanest and most energy-dense way of producing power, it has fallen victim to media shaming and misinformation. Nuclear power can produce energy by means of fission or fusion. Fission splits heavier isotopes that are above iron (specifically iron-56), fusion combines isotopes under iron-56; this is due to Fe-56 having the highest binding energy per nucleon making it the most stable isotope possible. That being said, an isotope below and above iron could be fused, the key lies in the energy balance. While fission is currently the more viable nuclear energy method currently, the holy grail of energy is fusion. Essentially, we wish to replicate the process that our sun undergoes; after all it is its own confined nuclear reactor fusing hydrogen into helium and heavier elements. Should humanity figure out fusion technology, limited power will be a thing of the past!

So, is humanity ready for the next chapter of power generation? Unfortunately that is a loaded question. Many engineering challenges exist to achieve limitless power, particularly fusion and trying to replicate sustained conditions like within the core of the Sun. However, we as humanity have a lot to look forward to with scientific advancement in the years to come.

Glossary

• Pump: A device used to pressurize liquids by converting mechanical energy of a motor into pressure/hydraulic energy. Generally a pump has a low pressure suction side to draw fluid in and a high pressure outlet side to push fluid out.
• Boiler/Steam Generator: A heat exchanger and closed vessel device used to turn water into hotter water or steam. Oils, natural gas and other fuels are often used to heat the water.
• Turbine: A rotary mechanical device that extracts pressure/hydraulic and kinetic energy from a fluid and turns it into rotational energy. This is achieved with angled blades specially shaped to rotate a shaft.
• Condenser: A device used to cool the low-pressure steam leaving the turbine. In refrigeration, it refers to a device that expels heat from the high-pressure refrigerant vapour.
• Isentropic: Refers to a thermodynamic process where entropy remains constant.
• Saturation Temperature: The temperature at which a fluid changes phase from liquid to vapour or vice versa at a given pressure.
• Superheating: The process of heating a fluid beyond its saturation temperature. In the case of steam, it makes steam hotter and drier.
• Entropy: The measure of disorder and randomness in a thermodynamic system.
• Irreversibility: A principle of thermodynamics where a particular change to a system CANNOT be undone, leading to energy losses. Efficiencies, friction and drag are all irreversibiities. 
• Non-Renewable Resource: A resource existing with a certain finite amount, it cannot be replenished.
• Non-Renewable Energy: Energy that is produced using non-renewable resources that can't be replaced on human time scales. This type of energy production is also associated with harmful emissions/byproducts like carbon dioxide and methane. Examples: Oil, coal, natural gas.
• Renewable Resource: A natural resource that can generally be replenished faster than it is used. 
• Renewable Energy: Energy that is produced using renewable resources. Renewable energy production generally produces very minimal or no harmful emissions/byproducts. Examples: Solar, wind, nuclear, hydrogen, geothermal.
• Fossil Fuels: A common term used for oil and gas fuels, it is so named based on the process of formation over millions of years from heat and pressure within the earth. 
• Global Warming: A human created phenomenon inducing unintended heating of the earth through the release of greenhouse gases.
• Net-Zero: The idea that humanity can produce as much clean energy as it consumes annually.
• Nuclear Fission: The means of generating power by splitting atoms in a controlled manner.
• Nuclear Fusion: The means of generating power by combining atoms in a controlled manner.