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Climate change, caused by an increase in greenhouse gas emissions such as carbon dioxide (CO2), has required the use of renewable energy sources. This study analyzes the structure of Romania’s electricity sector in 2017, specifically the share of renewable energy sources in the sector’s mix. The electricity sector uses both conventional (coal, hydrocarbons, and nuclear) and renewable energy sources (hydro, wind, photovoltaic and biomass). According to the study, the electricity sector in 2017 is still heavily reliant on conventional sources, which account for 64% of total energy consumption, while renewable energy sources account for 36%. Nuclear energy has the most stable operation of all the sources studied, but the power variation is small, with this technology operating at nearly constant parameters. However, nuclear power can experience outages due to the availability of the cooling source or the flow of cooling water in some situations. Nuclear energy had a maximum coverage of 30.66% of electricity consumption in 2017 and an average annual value of 19.53%. Renewable energy (wind energy and photovoltaic energy) has very large fluctuations because it is completely dependent on atmospheric parameters. Wind energy had a maximum of 45.86% and an annual average of 12.28%, while PV had a maximum of 14.56% and an annual average of 2.25%. The most important renewable resource, hydro energy, presented a maximum of 51.96% and an average annual value of 24.01%.

Drinking water has long been a free resource, but its cost is rising due to increased pollution of both surface and aquifer water sources. Drinking water requires special treatment to be potable and usable by the general public, treatments that consume a certain amount of energy. In addition, the treatment process of wastewater before it is discharged into the environment consumes energy. According to the study, the energy required for wastewater treatment is significantly greater than the energy required for preparing drinking water. Water treatment is a significant source of GHG emissions due to the use of energy and chemicals, and reducing energy consumption would significantly reduce our overall carbon footprint. Furthermore, the UN’s Sustainable Development Goals encourage access to safe drinking water and sanitation while also calling for greater resource efficiency. This research aims to provide an overview of the energy used in water treatment. This study attempts to depict the energy used in water treatment. Electricity consumption for water supply and wastewater treatment is substantial and has a significant environmental impact, particularly in countries where electricity is generated using fossil fuels.

Decarbonization of the energy sector to mitigate the consequences of climate change is possible by incorporating a greater share of electricity from renewable sources and thus reducing the share of fossil fuels in the energy mix, improving energy efficiency in general and increasing energy storage capacities. Renewable energies are increasingly permeating energy systems, causing significant shifts in the energy production mix. The success of transforming the electricity mix is dependent on the variability of renewable energy sources such as solar photovoltaic, wind, biomass, and hydro. The share of renewable sources in Romania’s energy mix was determined based on real data on electricity generation and consumption in 2019. However, the current electricity consumption has significantly surpassed the electricity produced from renewable sources. Specifically, the combined contribution of hydro, solar photovoltaic, wind, and biomass energy accounted for 39.86% of the total electricity consumption.

The discovery of radioactivity proved that the energy stored in the nucleus could be released as radioactive particles’ kinetic energy. Fission and fusion reactions generate enormous amounts of energy that could be used to generate electricity in nuclear power plants. The energy released or absorbed in these nuclear reactions comes from the different binding energies associated with each nucleus. Nuclear binding energy is the amount of energy required to keep a nucleus’s protons and neutrons together, and nuclear power is the amount of energy released during nuclear fission or fusion. Each type of nucleus has its own binding energy, which is the amount of energy lost when its nuclei came together and are the same as the amount of energy needed to split them. The paper describes a web application for computing nuclear binding energy per nucleon. The calculation of nuclear binding energy in terms of MeV/ nucleon entails determining the mass defect and converting the mass defect into energy per nucleon.

Using the Weibull distribution function, the study presents a statistical evaluation of wind characteristics and onshore wind power potential under temperate continental climate conditions. Wind energy projects are more expensive to install than conventional energy sources, but they have lower operating and maintenance costs (zero costs for fuel). Because the initial investment is so large, conducting as precise and reliable feasibility studies as possible is critical because they play a significant role in lowering the cost of energy production. As a result, wind speed measurements are critical for conducting accurate feasibility studies. The availability and accuracy of weather data are critical for determining wind potential at a specific location. Wind speed is an important factor to consider when analyzing the wind speed distribution function. The monthly and yearly values of Weibull parameters, and wind power density at the analyzed location, were estimated using wind speed data. The yearly value of the k parameter for the Weibull analysis was 1.153, and for the c parameter was 5.602, respectively. Also, the yearly average wind speed was found to be greater than the maximum wind speed. Another important conclusion is that the maximum energy-producing wind speed, rather than the average or most frequent wind speed, has the greatest influence on wind potential. The final outcome of this study indicate that the location analyzed is adequate for the exploitation of wind energy.

The paper analyzes the energy consumption of an energy-independent house in two different situations, namely when the exterior insulation is installed and, respectively, in its absence. The result of the analysis was used to assess the reduction of fuel consumption and greenhouse gas emissions of the auxiliary heating system, namely a biomass boiler. The home’s heating system consists of a Stirling cogeneration system with biogas, which produces 3 kW of electricity and 9 kW of heat, and a 50 kW biomass boiler. The biomass boiler must provide the additional heat necessary to cover the consumption of the house when the Stirling engine is running and respectively ensure the coverage of the complete heat consumption of the building when the Stirling engine is in standby mode. The analysis showed that the installation of external insulation on the building walls will reduce energy consumption by 13%–16%, depending on the variation of the outside air temperature.

The paper analyzes the variation of carbon dioxide emissions produced by burning fossil fuels for energy production in the European Union member states between 1960 and 2018. It was analyzed the evolution of CO2 emissions produced by the combustion of coal, gas, and oil in 28 member states. The analysis showed that Cyprus, Portugal, Greece, and Spain recorded the highest increases in CO2 emissions in 2018 compared to 1960, while the Czech Republic and Latvia recorded the lowest increase in CO2 emissions by only 7% compared to 1960. Only four countries (Germany, Luxembourg, Sweden, and the United Kingdom), out of the 28 countries analyzed, had in 2018, CO2 emissions lower than or equal to those of 1960. In 2018, CO2 emissions generated by burning coal increased in eleven countries and decreased in the other seventeen countries, compared to 1960 emissions. CO2 emissions from gas combustion increased in all 28 countries analyzed, with the mention that in 1960, eleven countries had no gas consumption. Regarding the CO2 emissions generated by oil burning, they have increased in 26 countries and only two countries have registered emissions reduction below the value of 1960. EU’s energy intensity (ratio of gross energy consumption to gross domestic product) decreased by 37% between 1990 and 2017.

Combustion of fossil fuels (even biomass combustion) to produce energy and heat for the industry is the most important anthropogenic source of nitrogen oxides (NOx=NO+NO2). Although NO2 is not a greenhouse gas, it is the precursor to the formation of such a gas, namely tropospheric ozone. Energy-intensive industries contribute up to 45% to the global greenhouse gas emissions, so to keep global warming below 1.5 °C according to the Paris Agreement requirements, CO2 emissions must be close to zero by 2050, so the industrial sector must be decarbonized. All decisions on reducing pollutant emissions and not just those of CO2 (by capturing and storing them), will lead to lower fossil fuel consumption and will increase energy efficiency in the industry and reduce greenhouse gas (GHG) emissions. The paper analyzes the synergistic effects of pollutants (NO2, NO), emitted by industry energy use, and meteorological factors in the formation of tropospheric ozone at an industrial site using Pearson’s correlation. Pearson’s correlation showed that the ozone concentration was significantly correlated with NO2, NO pollutants and the meteorological factors. Among them, NO2, NO, and relative humidity were negatively correlated with the O3concentration. We observed a significant positive correlation between solar radiations, air temperature and wind speed with O3concentration during the study period.

The present study aims to analyze the wind power potential in two locations in Galati county, Romania, before making a decision on the appropriate area for wind turbine installation. The hourly series of wind speed and wind direction were analyzed for the period between January 2017 and December 2018, measured at two meteorological stations of the national network at 10 m height. The Weibull and Rayleigh distribution models were applied to hourly wind speed data to evaluate wind speed characteristics and wind power potentials at wind turbine height. The annual values of k parameter for the Weibull analysis range from 2.15 in 2017 to 2.1 in 2018 for the GL3 site (GL3 — Galati county measurement station number 3, with geographical location: latitude 45.47 N and longitude 28.03 E), while for GL5 site (GL5 — Galati county measurement station number 5, with geographical location: latitude 45.82 N and longitude 27.44 E), the values are 1.33 in 2017 and 1.46 in 2018, respectively. Another important factor in wind resources assessment in addition to the average wind speed is the wind speed distribution in the regime, because two wind turbines installed in two different places (locations that have the same average wind speed), may generate a very different amount of energy, due to differences in wind speed distribution in the two locations. Thus, in 2017, the average annual wind speed at the two locations was approximately the same, being 5.44 m/s at GL3 and 5.41 m/s at GL5, respectively, but the maximum values of power density for the two locations were determined to be 260 W/m2 for GL3 and 361 W/m2 for GL5, in 2017. It was observed that the average annual wind speed was higher than the most frequent wind speed. Another important conclusion is that the greatest influence on the wind power potential has a speed that produces the maximum energy of the wind regime and not the average wind speed or the most frequent wind speed. From the data analysis, it was found that application of the Rayleigh distribution is not suitable for the GL5 case, as the wind speed does not have a normal distribution.

Controlling heat transfer and managing heat flows in a building has become very important in recent years and is essential to ensure the thermal comfort of occupants, increase energy efficiency, and sustainable development. These measures reduce energy consumption in buildings, save resources and money and at the same time reduce pollution and CO2 emissions into the atmosphere, as the severity of the climate increases. The paper describes the analytical method used to analyse the one-dimensional, steady-state heat transfer through homogeneous walls and composite walls of buildings (wall structure may contain different construction materials, air spaces, insulation, etc.). The web application allows users to analyse one-dimensional and steady-state heat transfer through the building walls and calculate the heat flux density, total heat flux, overall heat transfer coefficient of the building wall, thermal resistance, temperature profile through the wall, the specific thermal resistances and the temperatures at the interface between wall layers. The user can analyse the one-dimensional, steady-state heat transfer through homogeneous and multilayer walls of buildings, being able to analyse a wall composed of a single layer, or one with a maximum of seven layers. The application allows the user, after defining the cross section’s geometry, materials properties, and boundary conditions, to determine the optimal insulation thickness, depending on its placement, on the inner or outer wall surface.

Buildings are the major energy consumers, especially when they are located in severe climatic conditions where the energy requirements for heating and cooling are very high. Implementation of renewable energy sources in buildings to reduce their energy consumption and thus the fossil fuel consumption is a priority measure to reduce energy bill costs and greenhouse gas emissions, respectively. Although the initial cost of purchasing and installing renewable energy systems remains high, the costs associated with the operation and maintenance of these systems are negligible. This study aimed to analyse the integration of renewable energy sources in the building sector, namely the solar air heating system (SAHS), to assess the techno-economic-environmental performance of this system on reducing building energy consumption, economic benefits, and greenhouse gas emissions reduction. The paper analyses the annual efficiency of the SAHS integration into the building envelope, in a temperate-continental climate, with hot summers and cold winters. Finally, the proposed SAHS system was evaluated against the natural gas boiler heating system. The results of the financial analysis showed that the simple payback period of SAHS investment will recover in a period between 14 years to 5 years when the subsidies granted by the state are between 0% and 50%. The SAHS proposed here is economically feasible for the weather conditions and the building geographical orientation analysed and system implementation is a good solution to reduce buildings’ energy consumption by using renewable energy. The results show that the implementation of SAHS efficiently reduces, depending on weather conditions, the dependence on fossil fuels by reducing the thermal energy need to heat the building by a minimum of 15.53% in 2011 and a maximum of 24, 68% in 2007. Installing SAHS on the building wall, it will reduce the building heat loss through the wall, achieving a lost heat recovery at a rate ranging between 9.8% and 12.51%. Besides the economic benefits, the paper also highlights the environmental benefits of reducing CO2 emissions. Thus, the use of this system will reduce yearly CO2 emissions, depending on weather conditions, between 38 t CO2/year (2014) and 44 t CO2/year (2007).

In power plants or any combustion systems, for a maximum efficiency of combustion, an operational safety procedure (reduction of CO emissions) and environmental pollution reduction, it is highly important to determine and monitor the flue gas composition resulting from burning of solid fuels in combustion chambers. The paper presents the development of a web application, which can prove extremely useful for thermo-energetic engineers and researchers who wish to perform combustion calculations of the solid fuels (coal / biomass / solid waste materials). The application allows users to enter the data on the elemental composition of the analyzed fuel, excess air and fuel flow rate to determine volume of oxygen and air necessary for fuel combustion and flue gas volume. This web application can be also successfully used both in designing stage of the combustion equipment and in the operating stage since the chemical composition of solid fuels is extremely variable (particularly in the case of waste materials) consequently it is highly important to know the optimum quantity of air required for a maximum efficiency of combustion. Proper control of the combustion process will lead both to the optimum functioning of the equipment and to less polluting combustion gasses and will also reduce thermal losses. Keywords: Coal, Biomass and solid waste combustion, Combustion air, Flue gases, Combustion emissions analysis, Solid fuel combustion

The depletion of energy resources has been of primary concern in the `70s and `80s. In recent years, the decline of the environment due primarily to our energy-related activities has become severe and raises serious concern too. For this reason, method to analyze, improve and optimize energy-intensive systems have to deal not only with energy consumption and economics, but also with the pollution and degradation of the environment.

This paper analyzes the impact of thermal insulation on heat demand of a house in the SE of Romania. Can be noticed that by insulating the exterior walls of the building can reduce heat flux transmitted through them about 5 times and therefore the total losses by exterior walls about 25-40% depending on the glazing surface of the building and the materials of walls are made. [ABSTRACT FROM AUTHOR]

The paper presents a procedure for sizing a hybrid system with which it will examine annual performance photovoltaic hybrid power system considering wind-renewable resources available. The hybrid system, which includes PV panels, wind turbines, inverter and batteries, has been designed to provide a building with energy consumption of 319.7 kWh/day, given that renewable energy resources of the site are: solar radiation the 1700Wh / m2 / day and an average speed of wind of 3.43 m/s. [ABSTRACT FROM AUTHOR]

Combating the pollution with hydrocarbons includes preventive methods but also intervention methods. In present worldwide, are used five methods to combat the pollution with hydrocarbons. Using either of these methods involve a number of factors such as: weather limit conditions, technical features of intervention equipment, boundary conditions on the state of the pollutant and a number of advantages and disadvantages depending on the type of method chosen. [ABSTRACT FROM AUTHOR]

One of the most effective methods to include ecological technology in a house is the use of solar systems for water heating. This paper determined solar water heating potential (SWH) for the South - Eastern region of Romania. It resulted that the use of solar energy covers approximately 35-50 % of the thermal energy needs for water heating from January to April and from October to December and 80-100 % from May to September. This solar system reduces by up to two thirds the need to use traditional methods for water heating and minimizes costs for electricity or for fuel used in heating water, thus reducing the environmental impact. [ABSTRACT FROM AUTHOR]

Solar photovoltaic system is one of renewable energy system which uses PV modules to convert sunlight into electricity. Recent fossil fuel energy price escalation and likely future carbon dioxide emission cap-and-trade programs will substantially improved the cost-effectiveness of investment in energy conservation and renewable energy resources. Solar PV system is very reliable and clean source of electricity that can suit a wide range of applications. In this paper, a technical study about implementation of photovoltaic (PV) module which can be installed on the rooftop of the house to be used as clean energy source was done. The system's mathematical model is developed in MATLAB. [ABSTRACT FROM AUTHOR]

In this paper is illustrated a method to calculate the solar fraction for a solar thermal system with specific data. The installation is formed for a solar flat collector, a water storage tank, a heat exchanger, and two water pumps. The results of simulation for solar system are realised for producing hot water for a family. The mathematical model is used and evaluate for the annual variation of the solar fraction. Different parameters and specific data are for Bracanga, a Portuguese city. [ABSTRACT FROM AUTHOR]

Although methods of using renewable energy are knows all over the world (biomass, solar, wind, geothermal and hydro), so far only a relatively small fraction of the technical and economic potential of renewable energy is being used today. Investments in renewable energy and energy efficiency represent an important solution for environment and for economic crisis that Europe and the world at large are facing today. This paper presents the evaluation of renewable energy potential use for an independent house. The house uses a system comprising photovoltaic panels and solar panels. When there is surplus of electricity supplied from panels, this extra energy is stored in batteries to be used during not producing periods. We also use a solar thermal collector for thermal energy. The energy required for the home is used for household's appliances, for heating and for domestic hot water. Local real weather data are used in the modelling. [ABSTRACT FROM AUTHOR]