Energy in a nutshell
by Harsha Wickramasinghe
@ The Island / 29 Nov 2008
"Energy" – what does it mean to us? The majority of us tend to think that the electricity we get from Ceylon Electricity Board and diesel pumped at a petrol shed are two different things. Firewood used in a cook stove is yet another thing. The much hyped oil prices are nothing but a pain in the neck. And what about the calories of many food items we gobble here at home and burn over there at the local gymnasium? These are all seemingly different and distinct strains. But they have just one thing common. Although present in a diverse array of forms and phenomena, they are all ‘energy forms’ – the vital building blocks of our modern society.
The quantum of energy contained in a piece of firewood, a ray of sun or a drop of oil can be measured or ‘quantified’ using the common SI unit of Joules. Earlier, ‘calorie’ was the preferred choice for this quantification, but later still the more systematic SI system was adopted. In previous articles of this series we discussed the taming of fire (the beginning of human manipulation of energy sources) and the subsequent roles energy played in the making and braking of human civilizations. Now it is the time to identify the common thread that runs through this seemingly different array of energy forms.
Before that, it is important to know the many forms of energy we come across in the environment we live in. Firstly, there is heat, generated from combustion of fuels such as kerosene, LP gas, fuelwood or coal. The energy contained in the fuel is released when the fuel reacts with oxygen producing heat. The sun too, as we all know, produces heat. It happens through a continuous nuclear fusion reaction, which combines two hydrogen atoms to produce one helium atom and vast amounts of heat energy. Geothermal energy, emitted by hot well springs and erupting volcanoes, is a less common energy form stemming from a completely a different source. Heat can be used in variety of ways, starting from the simple kitchen hearth used to cook food, heating steels and plastics so they can be modelled into different shapes with less effort, glow a piece of wire so it can illuminate your room…etc…etc.
Secondly there is kinetic energy, which is simply the energy contained in a moving or a rotating mass. A rock hurtling down a mountain, a cyclist, a moving body of air and all moving vehicles are obvious examples. The kinetic energy in the blowing wind is transferred to the rotating mass of a wind turbine to generate wind power. Solar systems which set their plants rotating about, involve enormous amounts of kinetic energy. So is the occurrence of a very common phenomenon, the crashing of meteorites into the upper atmosphere, happening even at this moment. Interestingly, this unruly ‘rolling’ form of energy can be meticulously ‘tamed’ into performing delicate and fine functions. For instance, a moving hand of a watchmaker could skilfully transfer a portion of kinetic energy of his limb to a delicate metal piece so as to make the wristwatch wind automatically.
Thirdly, there is potential energy, which can be simply accumulated by climbing a stairway. All of us know that it is more tiring to go up than to come down. Also, it is much more difficult to carry a large suitcase upstairs than, say a small book. This is because of the effort we have to make against the gravitational force pulling things downward. Hence all objects in higher elevations harbour certain amount of added potential energy than when the same objects are positioned at a lower level. This potential energy is the basis of all hydropower generation schemes the world over, which utilises the higher potential energy of a body of water atop of a mountain to turn a hydro turbine.
Apart from the above common forms of energy, there are other forms of energy such as light energy, chemical energy and nuclear energy. Energy can neither be created nor destroyed. But then, this begs the intriguing question as to what happens when energy is used? If it does not get destroyed (finished) then what becomes of it? The simple answer, energy undergoes transformation from one form to another each time it is used. For instance, if a speeding car screeches to a halt when the driver applies brakes, the kinetic energy of the vehicle is readily converted to heat (dissipated in a heated up brake drum/disc) and noise (dissipated in a sound wave). The kinetic energy is not destroyed. It is converted. The car in turn gained its kinetic energy from the rotating engine. This energy is manipulated through the gearbox and transferred to the tyres. The rotating engine on the other had gets its kinetic energy from pistons moving up and down, propelled by heat generated by the burning fuel. The fuel in turn produces heat by converting its original form of chemical energy into heat when burnt. The fuel had accumulated this chemical energy millions of years ago when its source materials of dead plants and animals were naturally compressed and forced to undergo complex physiochemical reactions. Down the line, animals suffice their energy needs by devouring plants, while plants produce their own energy-containing food by harnessing solar energy through a process commonly known as photosynthesis.
Well, had all these ever dawned on you when you hit the brake pedal of the moving car?! Perhaps not. But the underlying fact here is, it is actually this complex conversion potential of energy that makes certain form of energy more preferred to other forms of energy. For instance, firewood can be only used to generate heat if combusted. But this heat cannot be readily converted into kinetic energy, whereas heat produced by burning a refined fuel such as diesel or petrol can be readily used to generate both heat and kinetic energy inside a gas turbine or an engine. Inasmuch, electricity is an energy form with many uses. It can be used to generate heat in an electric kettle, kinetic energy in an electric motor or light in an electric bulb. Most importantly, all these functions are literally just a switch away. On the contrary however, much more complex systems are required to operate an energy conversion system which uses a lower quality fuel such as fuelwood. These systems typically demand a lot of attention in operation and maintenance. Electricity therefore, in this light is a ‘versatile’ form of energy, and this versatility carries a premium which warrants a high demand for this particular energy form.
Perhaps we are not aware, but 48 % of our primary energy is supplied by fuelwood and other biomass while another 46 % comes from petroleum imports. Electricity accounts for only a mere 8.6 % of our energy requirement. Yet it is this ‘minor’ base that grabs our attention. In essence, the usefulness of an energy form, ease of use at the point of usage, having it only on demand without the need for storage and versatility all improve the quality of an energy form, which is also why electricity crows as the king of all energy forms. On the other hand, other energy forms such as fuelwood have limited applications in energy generation and also require storage. Thus their versatility ranks low in the hierarchy of the energy ladder. But it is practical to use the lower rung fuels for lower end applications such as producing heat and conserve the higher rung energy forms such as electricity for more advanced uses such as motive power necessary for turning machine tools for other productive work.
However, the world today is alarmingly drifting away from this ideal condition and is dangerously moving to a point where the rich can afford to use a higher end energy form to do all the lower end tasks and the poor cannot even afford the lower end fuelwood in a mundane task such as cooking a meal. This opens the dark abyss of energy poverty, in fact, far more divisive than the financial poverty!
Graphs, curtsey of Sri Lanka Energy Balance 2005, Sri Lanka Sustainable Energy Authority.
The writer is the Deputy Director General (Operations) of the Sri Lanka Sustainable Energy Authority.