Residential Energy Efficiency: Analysing Economic Viability


Author: Roney das Mercês Cerqueira & Gabriele Costa Gonçalves

Energy Review, Vol 4. Issue 6. 2022

Electricity is increasing its use in various activities in the residential, commercial and industrial sectors. Due to this growth, a need has arised to use new energy sources, especially the use of renewable sources, in order to meet the increase in consumption. Given this scenario, as an alternative to improve the way of using electricity, aiming at reducing environmental impacts and waste of power systems and increasing the yield of electrical equipment, the concept of energy efficiency has emerged. Currently, the idea of ​​energy efficiency has raised many discussions, with the objective of improving the use of electric energy in all areas of activity, especially in the residential sector. According to the projection of electric energy demand 2017-2026 of the Empresa de Pesquisa Energética (EPE), residential electricity consumption has a significant impact on the country's electricity generation, estimated at 29.7% in 2026 and in 2018 residential consumers were responsible for approximately 28% of all energy consumed in Brazil.

For the Associação Brasileira de Distribuidores de Energia Elétrica (ABRADEE) approximately 8% of all energy generated between 2000 and 2016 corresponds to electrical losses from energy inefficiency of electrical installations and their equipment. It is possible to say that there are many challenges to better energy use, which in most cases range from social and economic issues to cultural issues that involve habits of misuse of electricity itself, especially in the residential sector. One of the main challenges is the implementation of Distributed Energy Resources (DER), established by the Ministério de Minas e Energia (MME) in the Plano Nacional de Energia (PNE) 2050, whose objective is to use new technologies to achieve an ideal of generation and distribution of energy. Other challenges that confirm this reality can be seen both in the high price of electrical materials for residential civil constructions, and in the search for unqualified professionals to carry out electrical projects, which implies the use of cheaper, but less efficient materials and installations in disagreement with the Norma Brasileira 5410 (NBR 5410), a standard that establishes the appropriate conditions for electrical installations. In the present work, a comparative study was carried out regarding the energy efficiency of a residence located in the city of Feira de Santana, Bahia, through a quantitative and qualitative survey of the existing electrical appliances in the house.

Analyzes of graphs of average monthly consumption for the years 2020 and 2021 were carried out, based on data provided by the electricity concessionaire, in order to verify the behaviour of consumption over the mentioned years and to elaborate alternatives for better adequacy in terms of energy efficiency, with regard to changes in habits, especially considering the time of use of certain electrical equipment. The reference location, used for the present analysis, is a residence, which has two residents, with average monthly energy consumption in the order of 234.86 kilowatt-hours per month. The total number of electrical equipment counted was 65, in which more than 70 hours are connected daily, requiring a total power of 30,916 Watts. Through the analyses carried out in this study, it can be seen that through the interventions that the results prove to be favourable. In the first scenario, where a new consumption proposal was suggested, based on the temporal reduction of some equipment and domestic utensils and the extinction of others, it was possible to reach a consumption of close to 200 kilowatt-hours per month, thus obtaining a reduction of 14.5% in relation to the previous average monthly consumption, which in monetary terms and according to the tariff of the electric energy concessionaire operating in the State, enabled savings of R$ 30.62 per month. Another intervention adopted was the adhesion of distributed generation with photovoltaic cells in an on-grid system, and this intervention revealed more expressive numbers.

The project installed in the studied residence with a power of 3.15 kilowatts, generates an average of 330 kilowatt-hours per month. Taking into account the minimum consumption established by the concessionaire of 50 kilowatt-hours per month, with a tariff of R$ 0.88 for each kWh of active consumption, including taxes and excluding tariff flag and contribution to public lighting, it can be seen that the current expenditure on electricity went to R$ 44.00 (forty-four reais), whereas before, the average monthly expense was R$ 206.67, accounting for annual savings of approximately R$ 2,000.00, sufficient to cover investments within 8 years. At the end of this study and through the analyzes exposed in the work, it can be concluded that in addition to investments in energy sources that promote energy efficiency and the adoption of suggested consumption behaviour, it was possible to obtain better use of energy sufficient to reduce energy consumption. values ​​on energy bills, proving to be economically viable. (Mr. Roney das Mercês Cerqueira is a Masters student, and Dr. Gabriele Costa Gonçalves is a Professor at the Energy Engineering Department at the Universidade Federal do Reconcavo da Bahia (UFRB), Brazil.) ■□■

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