Energy is a huge concept – but essentially, it is ‘the power to do work’. Man can neither create nor destroy energy; he can, however, transform it into forms that he can harness for his own purposes. Energy can come from a ray of sunlight, a gust of wind, or another natural phenomenon. It can be stored as potential energy for millions of years. Stored energy can be released, for instance by combustion, and used for a multitude of applications, such as to produce heat, light or movement, generate electricity, and power vehicles or manufacturing process. Of course, energy is used by plants and animals in the processes of growth or decay.
In the context of daily life, when people talk about ‘energy’ they usually mean the electricity and gas supplied to their homes, and their ‘energy supplier’ is the company that sends their fuel bills. More generally, people discuss the ‘energy crisis’ and debate the relative merits of meeting the world’s ‘energy needs’ from nuclear power, fossil fuels and other energy sources. However, the fact remains that whilst man has devised many methods of harnessing energy, he cannot create it. It derives from the natural environment – the sun, wind and water.
The Most Important Chemical Reaction on Earth
The sun is the primary source of the energy that powers life on Earth. Plants and animals require energy in order to grow and be active, and this energy is created by plants through the chemical process of photosynthesis. All chemical reactions require an input of energy, and the energy that fuels photosynthesis comes from sunlight. Plants – and some algae and bacteria – contain chlorophyll.
When chlorophyll is energised by sunlight, it absorbs carbon dioxide and water from the atmosphere and converts them into carbohydrates and oxygen. The oxygen is released back into the atmosphere. The carbohydrates, which are composed of carbon, oxygen and hydrogen, are either used by the plant, or those that are not used are stored within its cells. This store of carbohydrates is the first link in the food chain. Animals derive energy from eating plants and vegetable matter containing carbohydrates, or by feeding on other animals that have eaten plants; they can then either use this energy, or store it as body fat.
This same process of photosynthesis led to the creation of fossil fuels. Since energy cannot be destroyed, once it has been produced it will continue to exist in the same form until it is converted into a different form. So all the energy that is still stored inside the cells of an organism when it dies, will stay there until something happens to release it. It can be passed on to insects and bacteria during the decomposition process; but if the decaying remains are fossilised, the energy in them will be preserved. That is what fossil fuels are: the decayed, compressed remains of vegetation and organisms that died in prehistoric times. The energy we obtain from fossil fuels today is carbon that was trapped by photosynthesis using energy from the sun many millions of years ago. That is another reason why photosynthesis is sometimes called ‘the most important chemical reaction on Earth’.
Harnessing Natural Energy
Naturally-occurring fossil fuels provide a convenient source of solar energy that we can extract from the earth with relative ease. However, we have now developed alternative, more technologically advanced methods of harnessing solar power. We collect it via photovoltaic panels. We build wind farms and wave farms to convert wind and wave power into usable forms of energy. We tap into the thermal heat that is buried deep in the Earth via heat pumps, and we construct geothermal power plants to generate electricity.
Another source of energy is nuclear power. This is energy that is released by the splitting or fusing of atomic nuclei. The nucleus of an atom is bound by very strong nuclear forces, and by splitting a nucleus, or forcing together two nuclei, massive amounts of energy can be released.
Energy comes in many forms. Some are more plentiful than others; some are easier to harness than others; some cause pollution, and some are considered potentially dangerous to the environment and to human life. The extent to which we consume each type of energy affects the world we live in, and this must be taken into account when choosing which energy source to use. Energy is necessary to sustain life, but we must be careful that we do not jeopardise our environment and the survival of the human race by consuming energy recklessly.