Much of technology consists in getting things done for us without our having to exert much towards the attainment of the goals. We exploit the laws of nature in ways that make non-human entities do the work for us. Work implies the expenditure of energy. Hence the importance of understanding the nature and principles of energy in the context of technology. It was no coincidence that both the elucidation of the energy concept in physics and the impact of science on technology took place at about the same period in human history: the mid-l9th century.
Energy appears in one of several forms as far as humans are concerned. Thus, there is electricity and light, heat and motion, chemical energy and sound and nuclear energy. It is a fundamental law of nature that in all the possible transformations of energy, whether they be spontaneously or artificially induced, ultimately all forms of energy are dissipated into heat energy. But heat energy may also be converted into every other form of energy, except nuclear. Thus, in the energy aspect of technology the challenge is to devise things in such a way that, starting from any one form of energy, we can get another form that is of circumstantial value and utility to us. In some contexts, we may need heat, in other contexts, light; and in yet other situations sound or motion is what we may want. The problem then will be to design devices which convert energy from one available farm into another desired form.
There is another aspect of energy which is of practical importance: the rate of conversion. In any specific situation it is not enough to have a particular form of energy: we must have it in the appropriate quantity. It is a little like having a check of very large denomination in our name. First we must find a bank that will cash the check: this corresponds to the problem of converting the energy in the required form. Secondly, the bank should be able to give us the cash in suitable bills to meet our needs. If we can only get $1000 dollar bills when our need is to buy a loaf of bread the money will be totally useless. When large amounts of energy are given out in a very short time (somewhat like having a $1000,000 check on hand), we have an explosion (usually from a chemical reaction), or an avalanche, or a hurricane. On the other hand, if the energy release is too slow, then too the situation may be useless. Geological processes involve impressively large amounts of energy, but at such slow pace that they are of very little practical interest. (Some explosive geological processes also occur, such as volcanic eruptions and earthquake tremors).
This brings us to the problem of energy storage which is another crucial problem of technological energetics. When, considerable amounts of energy are available we must find ways of storing them so that we can tap them as and when needed. In some instances such storage has been done far us by nature, and our problem is merely one of releasing that energy ingeniously and in suitable amounts. Coal, oil, gas, etc. are examples of stored energy. In other instances we invent storage devices. Such are springs and flywheels for mechanical energy, capacitors and batteries for electrical energy, and molten solids for heat energy, for example.