Losses in the electricity grid mainly represent that portion of energy that is dissipated as heat along the entire electricity supply chain, from generation to end user. These losses are present along all phases, including transmission (high voltage), distribution (medium and low voltage) and in transformer cabins.
Under normal operating conditions, leaving aside the corona effect, we can say that the network does not “leak electrons”. Energy, as mentioned above, is mainly dispersed in the form of heat. This phenomenon, unavoidable and intrinsic to the electrical system. Network losses are therefore physiological in principle: as long as there is electric current flowing inside a conductor, it will develop heat and therefore energy loss.
What causes losses in the electricity grid?
The physical principle underlying these losses is theJoule effect. Losses occur due to the electrical resistance of current-carrying cables: the higher the (electrical) resistance of a conductor, the more the cable itself will produce heat. This effect also increases the more the intensity of the current passing through the conductor increases.
Electrical resistance depends on the conductive material used, its operating temperature and the section of the conductor itself (a cable with a larger section has a lower resistance). All electrical machines and all cables are made of conductive materials, so each device installed in the electrical supply chain (even if very efficient) has a resistance and will consequently produce losses.
Without going too much into the technicalities of electrical engineering, the systems in alternating current additional effects are introduced (the so-called inductive reactances) which do nothing but increase the absolute value of the current circulating in the system. And as we have understood, if the current increases, the losses also increase.
Impact of losses in the electricity grid
Let us now analyze the impact that these losses have from an economic and environmental point of view.
Economic Impact
Network losses translate economically both in terms of energy not sold and therefore lost revenues, and in terms of infrastructure management costs. These costs in Italy are charged to consumers through the rates present in the bill. These costs are defined by ARERA on the basis of the estimates that it itself carries out, the costs are related to the type of user, the supply voltage and calculated as a percentage of the consumption of the individual user.
Environmental Impact
We know that about half of the electricity production comes from non-renewable sources (mainly natural gas) and is therefore generated from primary sources that emit greenhouse gases (plus a series of additional polluting elements). To satisfy the demand of us end users, placed at the end of the supply chain, means compensating for network losses by generating more energy than necessary at the source. This difference in energy, produced “for nothing”, if generated with natural gas, contributes to environmental pollution.
How to reduce power grid losses
The only solution is to minimize these losses as much as possible, to do this different methods are used. Let’s start with the most common ones:
- design lines with conductive materials and sections such as minimize the overall electrical resistance valuewithout obviously exaggerating in the other direction. Increasing the section means more material, with an overall oversizing of the entire infrastructure, which then leads to an unjustified increase in investment and management costs, as well as waste of material;
- limit to a minimum the value of the electric current at equal power transmitted to the network. To do this it is necessary to raise the voltage to hundreds of thousands or even millions of volts, which is why we have high voltage transmission lines;
- limit the value of the electric current to a minimum by compensating the inductive reactances. For those in the know this technique is called rephasing and it is necessary beyond certain limit values to avoid incurring penalties that are applied directly to the user in the bill;
- invest in infrastructure and more efficient materials low losses, which in fact brings us back to the first point;
Additional structural methods useful for reducing losses are:
- the installation of distributed generation plants (possibly renewable) so that electricity can be produced and consumed at the same point. By reducing the extension of the infrastructure that connects generation to the consumer, lengths are limited, and consequently losses. By generating the energy you need locally, you do not absorb it from the grid, translating into a further saving on your bill given that portion of the tariff that takes into account grid losses that is not paid.
- Transmit energy in high voltage direct current (HVDC – High Voltage Direct Current) rather than alternating current. In this way I cancel the dissipative effects of the reactances present in the alternating regime.
In conclusion, we have seen how network losses produce both economic and environmental implications. Reducing such losses requires joint efforts by authorities, network operators, manufacturers and designers. The design choices of the latter must not only take into account the minimization of investment costs but also the impacts that their choices produce in environmental terms, in order to guarantee a more efficient and sustainable electricity system.
Bibliography
ARERA 2022 Annual Report on the Status of Services and Activities Carried Out
