An analysis of energy efficiency for transcritical compression unit with CO2 (R744) as the refrigerant has been carried out using empirical operating characteristics for the two-phase ejector. The first stage of the refrigerant compression is carried out in the ejector. The criterion adopted for the estimation of energy efficiency for the cycle is the coefficient of performance COP. The analysis is performed for the heat pump and refrigeration systems. The results of COP for the systems with the ejector has been compared with the COPL values for the single stage Linde cycle.
The evaporation temperature is regarded as one of the major parameters influencing the organic Rankine cycle (ORC) efficiency. Majority of contributions in literature for ORC cycle analyses treat the heat source as if it had an infinite heat capacity. Such analyses are not valuable as the resulting temperature drops of the heat source needs to be small. That leads to the fact that the heat source is not well explored and in the case of waste heat utilization it can prove the poor economics of the ORC. In the present study cooperation of the ORC cycle with the heat source available as a single phase or phase changing fluids is considered. The analytical heat balance models have been developed, which enable in a simple way calculation of heating fluid temperature variation as well as the ratio of flow rates of heating and working fluids in ORC cycle. The developed analytical expressions enable also calculation of the outlet temperature of the heating fluid.
The increase of ship’s energy utilization efficiency and the reduction of greenhouse gas emissions have been high lightened in recent years and have become an increasingly important subject for ship designers and owners. The International Maritime Organization (IMO) is seeking measures to reduce the CO2emissions from ships, and their proposed energy efficiency design index (EEDI) and energy efficiency operational indicator (EEOI) aim at ensuring that future vessels will be more efficient. Waste heat recovery can be employed not only to improve energy utilization efficiency but also to reduce greenhouse gas emissions. In this paper, a typical conceptual large container ship employing a low speed marine diesel engine as the main propulsion machinery is introduced and three possible types of waste heat recovery systems are designed. To calculate the EEDI and EEOI of the given large container ship, two software packages are developed. From the viewpoint of operation and maintenance, lowering the ship speed and improving container load rate can greatly reduce EEOI and further reduce total fuel consumption. Although the large container ship itself can reach the IMO requirements of EEDI at the first stage with a reduction factor 10% under the reference line value, the proposed waste heat recovery systems can improve the ship EEDI reduction factor to 20% under the reference line value.
Improving energy efficiency is key to moving toward sustainable development. It contributes to the reduction of energy consumption and carbon emissions, as well as to climate change mitigation. Indicators of energy efficiency play an important role in this field because their improvement is targeted by policy makers. Indicators based on the ratio between energy consumption and gross domestic product (GDP) are currently used by multiple key organizations, including Eurostat and the World Bank, as the main energy efficiency indicators. This study examines the most widely used indicators and identifies their deficiencies. Over the last decades, these indicators tend to show a continuous strong improvement, signifying positive progress toward energy efficiency, even in cases when the physical consumption of energy has increased significantly. This phenomenon is based on GDP adjustment. The energy intensity of economies, used currently to measure energy efficiency, masks problems and has led to the green labeling of wealthier economies. An analysis of energy efficiencies reported for multiple countries and the structure of their energy spending shows that the reported values are counterproductive for comparing economies in the context of environmental protection. The indicators sanction economies with low energy consumption and low or moderate GDP. The economies belonging to the group of the largest energy spenders per capita are labeled highly efficient because of GDP adjustment. Decision makers are therefore prompted to focus on GDP growth even at the cost of a major increase in energy consumption. An additional problem in the indicators is that they do not properly model international trade. The responsibility for energy spending is shifted toward the producers of energy-intensive goods and services. Energy intensity is a useful indicator to measure the resistance of an economy to the volatilities of energy prices. However, the challenges in the fields of environmental pollution and climate change are related to physical processes and energy consumption rather than to changes in the GDP or the monetary valuation of products and services. Indicators measuring energy efficiency as GDP per unit of energy use are inadequate and misleading as principal tools to measure energy efficiency.
A commercially available ASPEN PLUS simulation using a pipe model was employed to determine the maximum safe pipeline distances to subsequent booster stations as a function of carbon dioxide (CO2) inlet pressure, ambient temperature and ground level heat flux parameters under three conditions: isothermal, adiabatic and with account of heat transfer. In the paper, the CO2working area was assumed to be either in the liquid or in the supercritical state and results for these two states were compared. The following power station data were used: a 900 MW pulverized coal-fired power plant with 90% of CO2recovered (156.43 kg/s) and the monothanolamine absorption method for separating CO2from flue gases. The results show that a subcooled liquid transport maximizes energy efficiency and minimizes the cost of CO2transport over long distances under isothermal, adiabatic and heat transfer conditions. After CO2is compressed and boosted to above 9 MPa, its temperature is usually higher than ambient temperature. The thermal insulation layer slows down the CO2temperature decrease process, increasing the pressure drop in the pipeline. Therefore in Poland, considering the atmospheric conditions, the thermal insulation layer should not be laid on the external surface of the pipeline.
Energy and spectral efficiency are the main challenges in 5th generation of mobile cellular networks. In this paper, we propose an optimization algorithm to optimize the energy efficiency by maximizing the spectral efficiency. Our simulation results show a significant increase in terms of spectral efficiency as well as energy efficiency whenever the mobile user is connected to a low power indoor base station. By applying the proposed algorithm, we show the network performance improvements up to 9 bit/s/Hz in spectral efficiency and 20 Gbit/Joule increase in energy efficiency for the mobile user served by the indoor base station rather than by the outdoor base station.
The objective of the paper is to analyse traceability issues in real-life gas flow measurements in complex distribution systems. The initial aim is to provide complete and traceable measurement results and calibration certificates of gas-flow meters, which correspond to specific installation conditions. Extensive work has been done to enable a more credible decision on how to deal in particular situations with the measurement uncertainty which is always subject of a flow meter’s calibration as a quantitative parameter value obtained in laboratory, and with the qualitative statement about the error of an outdoor meter. The laboratory simulation of a complex, real-life distributed system has been designed to achieve the initial aim. As an extension of standardized procedures that refer to the laboratory conditions, the proposed methods introduce additional “installation-specific” error sources. These sources could be either corrected (if identified) or considered as an additional “installation-specific” uncertainty contribution otherwise. The analysis and the results of the experimental work will contribute to more precise and accurate measurement results, thus assuring proper measurements with a known/estimated uncertainty for a specific gas flow installation. Also, the analysis will improve the existing normative documents by here presented findings, as well as fair trade in one of the most important and growing energy consumption areas regarding the legal metrology aspects. These facts will enable comparing the entire quantity of gas at the input of a complex distributed system with the cumulative sum of all individual gas meters in a specific installation.
About 55% of over 14 million Polish households live in multi-family buildings. Cooperative or housing association buildings have a large share in this group. The heat is supplied from the district heating network or from local sources. With respect to facilities fed from gas boiler rooms, the signing and execution of fuel supply contracts is required. From October 1, 2017, the obligation to submit tariffs for gas trading set for all final customers (except for individual gas consumers in households) for approval to the President of the Energy Regulatory Office was lifted. Decisions regarding the choice of the supplier and the content of the concluded contract are made by the authorized bodies of the cooperative or housing association. The consequences of such decisions are borne by the owners and users of residential premises. Ensuring the continuity of a contract for the supply of gaseous fuel essentially comes down to establishing prices and rates in force for a given period. The right decision on the moment of signing the contract or the amendment, termination of the existing contract and signing a new one, or negotiation efficiency will result in financial profits for all users. The costs of heating and domestic hot water preparation are a significant component of the overall cost of the maintenance of flats in Poland. Therefore, it is even more important that the prices and rates agreed upon with the gas supplier are as favorable as possible to users. The high costs of heat are not only expenses for apartment owners. The attractiveness of flat on the rental market is also decreasing. The business activity carried out in facilities located in such buildings is also less competitive.
The authors of the article analyzed gas prices on the Polish market over the last 3 years and presented the results of simulations of the effects of specific prices and rates set in the contract for the supply of fuel at the cost of heating from the point of view of a single apartment. As these are not large amounts per year, they do not motivate to optimize the terms of the gas purchase contract in this respect. The dynamics of changes in gas prices in Poland, although slightly different from world trends, is high. This makes it difficult for those responsible to make the decisions, and for residential users, it often means spending differences in subsequent years. One of the consequences of setting prices and rates significantly higher than obtainable may also be the reluctance of local communities to take measures to increase the energy efficiency of the heat supply system. From the point of view of heating costs, such decisions may distort the economic effect of thermo-modernization.
In this article, the author will try to conditionally transform the energy capacities of NNEGC
Energoatom by converting a liability into an asset using the example of bitcoin. With a surplus of
nuclear power generation, one of the modern tools for using excess electricity is directing it to cryptocurrency
mining. The author of the article will try to calculate the possibilities of Ukrainian NPPs
in the cryptoindustry market by analyzing the competitiveness, market trends and the approximate
profitability of this kind of activity. The essence of the article lies in the intervention of the state
energy giant in completely new activities, partial monopolization of the market and interference
in the activities of decentralized cryptocurrencies, as well as the very novelty of combining two
different fields of activity and the global nature of the consequences. Mining can be used to convert
the underdeveloped electricity or all of Energoatom’s capacities totally, but at the same time it can
also affect the cryptoasset market in the field of decentralization, as the primary cost factor to affect
the price of assets and allow for obtaining super-profits at a state enterprise. The author of the article
tries to understand the profitability of such actions and, in general, to understand the globality
of the idea. The results of the entry of the national energy giant into the cryptoasset market will
change the global processes in the ecosystem of the cryptoindustry and change the situation both
on the electricity market in the region and, in general, will affect the processes of globalization and
unification of the financial sectors of the economy.
The energy efficiency of photovoltaic modules is one of the most important aspects in energetic and economic aspects of the project related to system installations. The efficiency of modules and the electricity produced by photovoltaic conversion in solar modules is affected by many factors, both internal, related to the module structure itself and its technical and external factors related to the energy infrastructure, which includes: cabling, inverters, climate conditions prevailing at the micro-installation location and the orientation and angle of inclination of the solar modules. The installation of photovoltaic modules should be preceded by an energy efficiency analysis, which will help to indicate the optimal solution adapted to the given conditions. The article presents a comparative analysis of the amount of energy produced under real and simulated conditions. Analyzes were made on the basis of research carried out in the Wind and Solar Energy Laboratory located at the AGH University of Science and Technology, data from solar irradiation data-bases and computer software for estimating energy resources. The study examined the correlation of the solar irradiation on the modules and the amount of electricity generated in the photovoltaic module. The electricity produced by the module was compared under real conditions and simulated based on two sources of data. The comparison and analysis of the amount of energy of the module were also made, taking simulated different angles of the module’s inclination into account.
The article discusses issues related to improving the energy efficiency of heat supply systems. It draws attention to the need to take action not only for large objects and systems, but also for individual buildings and their boiler plants. Heat supply system monitoring allows for the diagnosis of the weakest elements and making decisions leading to the improvement of energy efficiency. In the case of the boiler room where the research was carried out, the results of such monitoring convinced to equip boilers with an additional automatic control system, with an algorithm limiting the number of burner switching cycles and shutdowns. Limiting the number of switching on the burners, as in the case of other combustion and electric devices, has a significant impact on the energy efficiency of the entire system. In addition, it also increases the durability of the devices, and thus reduces costs of servicing and repairs. The simplest control algorithms, often used in controllers installed in the boiler units, do not provide optimization in this respect. The external device used has allowed the number of burners on and off cycles to be limited while maintaining the quality of the heat supply to the heating installation and the heat treatment system.
The material also presents other ways to improve the energy efficiency of the heat supply system in existing multi-family buildings.
The paper presents the results of the energy analysis of the conversion of solar radiation energy into electrical energy in Polish weather conditions. The effect of sunlight and working temperature on the photovoltaic module on its power curve P = f(U) is shown. STC and NOCT conditions are described for which the manufacturers specify the parameters of the photovoltaic modules. The manufacturers of photovoltaic panels should give the PPV = f(E) characteristic for the different values of the operating temperature of the modules. An analysis of the economic efficiency of a photovoltaic power plant investment of 1 MWp taking the current legal regulations for the three variants into account was presented. Variant I – the investor benefits from the support of public aid of operational only, Variant II – the investor benefits from the support of public aid for investment in the amount of PLN 1 million, Variant III – the investor benefits from the support of public aid for investment in the amount of PLN 2 million. For all variants, indicators for assessing the economic effectiveness of the investment and the value of the auction price from the maximum price to the price at which the project loses its profitability are determined.
In this paper, selected aspects of energy efficiency are shown. The European Union regulations in area of energy efficiency such as Directive 2012/27/EU, are discussed. The national legal regulations which describe energy efficiency such as the Energy Efficiency Act are presented. Principles concerning the obligation of energy savings and energy audits of enterprises are described. National, regional and local programs and measures concerning the improvement of energy efficiency are performed. These are horizontal measures and energy efficiency measures in: industry, transport, the buildings of public institutions and energy generation and supplies. National economy energy efficiency is shown. The energy intensity indicators (primary, final) and rate of their changes in last years are performed. Moreover, directions of undertakings connected with the possible future reduction in energy intensity of the national economy, are defined. An analysis of energy efficiency measures and solutions for the improvement of energy efficiency, especially in industry and households, is performed. The improvement of economy energy intensity indicators constitutes the most effective solution which brings significant economic, technical and environmental benefits such as an increase in economic innovation and its competitiveness, the improvement of the energy supply security level, a reduction in the consumption of natural resources and a reduction of air pollution and greenhouse gas emissions. The conclusions contain an analysis of the present level of energy efficiency in Poland and the perspectives of its increase in the future along with the benefits connected with it.
General lighting is the most common way of illuminating interiors and the source of electricity consumption in buildings. This fact forces the search for lighting solutions effective both for people and the environment. In this study the impact of room and luminaire characteristics on general lighting conditions and energy efficiency in interiors is considered. In rooms of different sizes and reflectances, seventeen luminaire types with various light distributions were arranged in uniform layouts. The levels of average illuminance, uniformity and normalised power density related to two horizontal working planes were calculated. The impact of working plane reduction, room index and reflectances, lighting class and luminous intensity distribution of luminaire on the considered parameters was investigated. The use of the reduced working plane resulted in the increase in the average illuminance (7.7% on average), uniformity (33% on average) and normalised power density (23% on average). The impact of the room index and lighting class on the average illuminance and normalised power density was significant while the impact of the luminaire luminous intensity distribution and room reflectances was low. The normalised power density levels of the general electric lighting in interiors, with luminaire luminous efficacy of 100 lm/W, are in the following range: 1.08‒3.42 W/m² per 100 lx. Based on these results a normalised power density level of 2 W/m² per 100 lx is recommended for designing and assessing the new general electric lighting systems in buildings.
Technical and operational energy efficiency measures for ships, such as the energy efficiency design index (EEDI) and ship energy efficiency management plan (SEEMP), aim to improve the energy efficiency of international shipping. Studies show that absolute emissions from international shipping will increase despite their mandatory application. For this reason, it is important to assess the impact on the effectiveness of the application of mandatory efficiency measures on future emissions. Further measures are being developed at the International Maritime Organization to control emissions from ships, in particular greenhouse gases (GHG) that contribute to climate change. In January 2019, a system of collecting fuel consumption data by ships (Ship Fuel Oil Consumption Database) was introduced.
Energy efficiency measures promoted by the IMO Maritime Environment Protection Committee, initially as facultative, then as mandatory, show strong preventive character. The mandatory use of energy efficiency measures by ships as well as the development of energy efficiency management policies by shipping companies contributes to climate protection and adaptation to climate change.