Simply put: Energy is the capacity for doing work.
Energy comes in various forms: Potential, Kinetic, Thermal, Electrical, Chemical, and Nuclear. Man has devised many, many ingenious ways of putting it to use. The reason that I chose to pose the two questions is because there are many people who simply are ignorant of the importance of energy. Without it your body dies. The food we eat, the water we drink and the oxygen we breath are all used in a process plant called the human body which transforms it to energy - energy that gives us the capacity to exist. The human body performs work 24/7 until it dies. The beating heart consuming calories to pump the blood that carries that chemically transformed energy to the rest of our body, the electrical energy that is produced from that to maintain our nervous system. All that and more. Its all energy that is consumed and transformed.
It occurred to me a long time ago when I was in high school physics class that energy is a very neat phenomena. Everything has it and its just sitting there in its various stored forms begging to do work. Along comes Greek mathematician Heron and conceives a windmill. He did not ever actually build it that anyone knows of, but he dreamed it, a couple hundred years later in Persia the Panemone Windmill was born. It is unknown if that was a transfer of knowledge because a Persian fellow read Heron’s work or he was simply a mechanical genius himself, his name is lost so we may never know. The Tibet Prayer wheels came into existence roughly at this same time. Man has consistently developed new means to use energy since he came into existence. For the most part, all them were for one simple reason - security. One is not secure if he is not warm, well fed, and protected from his environment. That all takes energy.
This is the root of my question. If this one thing is the basis of all life, our existence, why wouldn’t everyone at least not want be informed of the basic information and have some even little knowledge about energy? It is after all the single most studied physical thing known to man. Yet so many fail to understand that eating a cream cheese bagel is exactly the same thing as putting a gallon of gasoline in your car. [they are not the mathematical equal in stored energy but they are both fueling a vehicle]
The Law of Conservation of energy states: Energy cannot be created or destroyed, only transformed from one form to another. What does this mean? Simple, we cannot create it. Because we cannot create it, we also should not rename it or redefine it! Even Leonardo da Vinci recognized that as well as Albert Einstein. While man cannot create energy, we have certainly exhausted billions of brain cells trying to perfect the use of it, the many ways to transform it, to try and recapture it, and every once in a while someone comes along and poof! The light bulb shines brightly… The man that invented that incandescent bulb could not have done so without another mans invention - the Faraday disk. Men working, sometimes together, sometimes not, but all working to build a better mouse trap so to speak. There are two words that critical thinkers use when designing new ways to make use of energy transformations. Efficiency and Practicality. As there is always a loss when energy is transformed, that entropy that cannot be harnessed, that random flaw in our system, that friction or resistance, one strives to minimize that. Man cannot create a perfect machine - but we can sure try and many have. What we have succeeded at is constantly improving efficiencies and practicalities.
We also occasionally take a step backwards. Or in the case of energy, several. I give you the wind turbine. While practical in some small deployments, it is not practical in large sustained systems and proves it reliability issues regularly. That is the very reason I gave a windmill as my first example of mans harnessing and transforming energy. While in use for a long time, as soon as readily available, reliable, practical -(cost is part of practical), came along, most windmills, water wheel mills, and other machines that relied upon the weather to function they went by wayside, right along with the horse drawn taxi’s, just as soon as a Model T became practical. The Rankine cycle, fossil fuels, and the modern marvel that is a thermal power plant gave us security and stability, an efficient, reliable source and system of Energy. The word renewable should never be used to describe a form of energy, none of them are. Renewable energy is an oxymoron. Man cannot renew energy no more than we can create it. So remember the next time you plug in your highly illuminated, chromium plated 900 watt Keurig coffee maker - the energy it consumes giving you that cup of goodness, is not renewable - its in the heat being held by the elixir in your coffee cup. Just as when the wind blows on that wind turbine the energy transformed into mechanical energy to drive the generator cannot be renewed, it is forever transformed. It cannot be reversed. Rankine cycle plants originally were about 34% efficient, that has been improved and B&W just finished building one in India that is boasted at 64%. A wind turbine is 9% on its best day. A leap backwards. Enjoy your coffee and I hope you enjoyed this, maybe even got a morsel to think on. Spud.