school energy&environment

The national energy balance

The importance of energy in modern society led man not only to create complex “energy systems”, but also to try and measure how much energy he uses each year and understand which source he gets it from and from which Country he imports it from. These problems have been solved by using adequate energy measurement units and a scheme representing the energy flows that enter a country and how energy is used in the different sectors along the year: the National Energy Balance. Like any other balance, the energy balance collects information on energy input and output. The national energy balance is the most famous one and is a collection of information on how energy is produced and used within a Country during the year. How can the National Energy Balance (NEB) be read? To begin with, the energy available from the various sources is reported with a common unit of measurement mentioned before: the Tonne of oil equivalent. This allows the sum and the comparison of data relating to different sources. The first piece of information contained in the NEB is the total available energy, subdivided according to the sources (also known as primary energy consumption and primary sources). Such data show how much energy is made available in a country to be consumed directly (for example, the electric energy imported or produced in hydroelectric power plants) or to be transformed into by-products to be launched on the final-user market afterwards (for example oil is refined into petrol and gas oil) or, finally, to be transformed into electric energy (coal, gas and oil used in thermoelectric power plants to produce electricity). The energy supplied by primary sources can belong to the country concerned (national production: for example the natural gas extracted by Italy from the field of the Po valley or the Adriatic sea) or be imported (for example the oil Italy imports from the Middle East or the natural gas imported from Libya and Russia). Mention should be made that during this definition stage of primary energy consumption the national production of electric energy only includes the production of hydroelectric, geothermal, solar and wind power plants or any renewable resources but, as was stated before, does not include the energy obtained by burning fossil fuels. This distinction was introduced to avoid that part of the energy available is counted twice, first as oil and then as electric energy produced by burning the oil. The exported energy and the variation of stocks are to be subtracted from the sum of the national production and imports of different sources. Thus the primary energy available is achieved (also said primary energy consumption or gross domestic consumption).