All organisms need energy to live. Energy is connected to all human activities: whenever we think or move, we use the energy that is stored in our body and all the objects that we use or that surround us need energy to work or needed energy when they were built. Energy illuminates us and warms our houses, allows us to move, feeds the tools we use to produce food, and so on.
All that produces energy is “an energy source”. The Sun is the main source of energy for the Earth.
The Earth receives from the Sun an uninterrupted flow of energy that, as well as supplying all vital processes (both vegetal and animal), melts the ice and supplies the water cycle between the sea and the atmosphere; it produces the wind, favours the growth of those plants that during millions of years have transformed, together with animal remains, into fossil fuels, coal and natural gas.
In general, all the energy available on our planet derives, directly or indirectly, from the Sun: water energy, wind energy, chemical energy of fossil fuels (coal, oil and natural gas) and biomass (i.e. wood); even waves energy.
Tides energy derives from the gravitational fields of the Sun, Moon and Earth.
Geothermal and nuclear energy do not derive from the subsequent transformations of solar energy, but are related to the Earth formation.
Primary and secondary sources
The numerous existing energy sources can be classified in different ways. Primary sources can be used directly, as they appear in the natural environment. Secondary sources derive from the transformation of primary energy sources
Renewable and non-renewable
Some sources are renewable, i.e. they provide energy, which is constantly regenerated by means of chemical transformations (e.g. biomass) or physical transformations (e.g. water power, solar, wind power, etc.). In particular the sun, the wind, the water cycle, the tides, the heat of the Earth are non-exhaustible sources, which are always available and will never end.
The units of measurement used by human beings to express the quantity of energy sources are numerous. There are measures for physical quantities and measures for the energy or heat content.
Albeit in different forms, energy is everywhere. However, the energy available which can be controlled, transformed and used by human beings (thanks to today’s technology) is only a small part of the energy contained in the primary sources.
For example, energy can be found in the chemical bonds of oil, coal and gas (chemical energy turning into heat during the combustion process) or in the power of the blowing wind or water falling from the mountains (mechanic energy which can be transformed into electric energy) or the nuclear bonds (nuclear fuels) which, if they are altered through ad hoc processes caused by human beings, produce huge quantities of heat (thermal energy).
Work and heat energy
Energy mainly comes under two forms: work-energy and heat-energy. The former can be fully transformed into the latter, but not vice-versa because the heat tends to disperse. The energy that produces work can again be divided into potential and kinetic energy.
All energy forms can be transformed into other forms of energy: by burning coal we transform its chemical potential energy into thermal energy (heat). Thanks to the steam engine, the heat can in its turn be transformed into kinetic energy, i.e. the motion of the locomotive.
At this point the notion of efficiency is to be dealt with. As a matter of fact, energy resources are precious goods, which are to be used efficiently and effectively. A basic concept to assess the quality and waste of any human activity is efficiency. Efficiency assesses which part of the energy and materials making up any action or process was successful and which part was lost. Energetic transformations too always lead to some losses.
When can it be said that use of a natural resource is sustainable? Generally we can say that a natural resource is used by man in a sustainable manner when, knowing its capacity to reproduce (consider fish as a natural resource) or to maintain a determined quality (for example the purity of the air we breathe) it is not exploited more than a determined threshold. When use of a resource exceeds the said threshold, it means that there will be a progressive and dangerous impoverishment, in terms of quantity (the global population of fish drops to a limit below which the species is destined to disappear) or in terms of quality (the air is so polluted that it is bad to breathe and causes severe diseases among human beings). If this “impoverishment” of the natural resource is definitive (disappearance of the species) we say that an “irreversible” damage has been provoked, i.e. it is not possible to go back and bring the species back to life. Impoverishment, instead, is considered “reversible” if it is possible to go back and recover the natural resource (polluted air can become breathable if polluting substances are no longer emitted).
Actually the concept of sustainability can only be applied to renewable natural resources that can be reproduced in times that belong to a “human scale” (for example, firewood). For non-renewable sources, such as fossil fuels, it is best to talk of optimum exploitation. In other words we must try our best to use these in an efficient manner (making them last as long as possible) and in the meantime, find technologies that allow the exploitation of alternative sources in their place, which may even be characterized by a “renewable” nature (for example to replace the energy produced by fossil fuels in the future with solar energy, which is a renewable source).
The development of our society is tied to energy consumption. Without energy, man would not have been able to reach the present level of wellbeing and quality of life. Without the availability of sufficient energy resources future economic development would be jeopardized.
Effects on the environment
The energy issues arose in relation to the environmental issues. Use of energy greatly modifies the state of the environment and the effects can be of a local, regional and global nature. In this perspective, that is valid on a planetary scale no less than on a national and regional scale, right up to each one’s home, the protection of the environment becomes a primary objective to be achieved in the development of the different energy systems.
Hydrocarbons and climate change
Fossil fuels (oil, gas and coal) are, today, the most utilized sources worldwide for the production of energy. They account for over 80% of the energy consumption of the planet. Their combustion, however, involves the emission of large amounts of carbon dioxide (CO2), whose increasing concentration in the atmosphere is considered the principal cause of climate change.
The technology used for the geologic capture and sequestration of CO2 (CCS)
Since fossil sources are destined to be the protagonists of the world energy scenario for many more years, we must act immediately, directly on their utilization, in order to reduce CO2 emissions with regard to their combustion. CO2 Capture & Storage (CSS) technology enables the capture and sequestration of the CO2 generated by the use of fossil sources, reducing the emissions in the atmosphere.
In the improved utilization of natural resources (and not only energy), research and technological innovation, national and local energy policies, and especially culture and behaviour of the population, will surely have a fundamental role.
A reduction and correct management of waste, an appropriate use of electrical appliances, an intelligent management of household lighting and of heating in offices and apartments, use of public transport instead of one’s own car, all these are actions that, if put to use by all of us on a daily basis, will lead to a decrease in the waste of energy, an increase in the performance of the overall energy system and especially a “saving” in terms of natural resources, the environment and also of money.
Each one of us, therefore, can strive to save the present energy sources, by using innovative technologies, but also adopting small improvements in our daily life. To do one’s best to realize a sustainable development however does not mean giving up what one has, but rather to avoid wasting.
A considerable amount can be saved in electric energy if users are well-informed and their behaviour reflects their awareness, and by adopting the so-called “good practices”, such as:
• do not leave the lights on in rooms that are not occupied;
• choose chandeliers with less bulbs (for an equal amount of lighting produced, chandeliers or lamps with a number of bulbs consume more energy than those with one light bulb only);
• position the refrigerator or the freezer in well ventilated places, far away from sources of heat…
Saving energy when washing clothes
Washing machines consume about 25% of the electric energy for domestic use and every year they produce polluting emissions that have been calculated to be 7 million tons of carbon dioxide, 65,000 tons of sulphur dioxide and 20,000 tons of nitrogen oxides. There are models equipped with a double water intake (hot water and cold water, depending on the selected programme) that allow greater savings, while the “wash & dry” models use a lot of energy.
Saving energy in the kitchen
The dishwasher. For a washing-cycle at 65°C, a dishwasher consumes an average of 20-30 grams of detergent, 1.5-2 kWh and it produces about 1 kilogramme of carbon dioxide. Remember not to position this electrical appliance near the refrigerator and make sure there is a BIO button so that it can be used with detergents that do not contain phosphorus (a very polluting agent).
Saving energy in the rest of the house
The air conditioner. In order to protect our health, it is good to keep the filters clean. These can accumulate harmful substances such as bacteria and dusts. Furthermore, it is advisable not to set the temperature at a level that is very different from the temperature outside, because it is equally harmful for us, and it is very costly from the point of view of energy. In fact, it would be better to use fans or dehumidifiers, and favour cooling the house by keeping the windows open at night and allowing the air to circulate.
The European Union has ruled to gradually banish all incandescent bulbs (which regards the production of new bulbs). Exception is made for incandescent light bulbs made for specific purposes (e.g. refrigerators, ovens, etc.).
The heating system
With regard to the heating system of houses, the conditions of a beautiful day in spring should be created, 20 degrees centigrade, humidity about 50% and good circulation of air: only slightly heat the rooms that are not used at all, or which are used rarely; during the day, keep the temperature at 20 degrees centigrade, at night 16 degrees centigrade…
What you can do
Our small daily actions can contribute to energy saving, and these include some ways to behave with regard to the use of “household energy”, i.e. the energy used for heating and electricity. It is pointed out that energy for domestic use absorbs more than 18% of the national energy requirements and is responsible for approximately 27% of the polluting emissions. We can try to save up to 50% of the household energy that we utilize.