Basing on the first and second law of thermodynamics the fundamental trends in the Polish energy policy are analysed, including the aspects of environmental protection. The thermodynamical improvement of real processes (reduction of exergy losses) is the main way leading to an improvement of the effectivity of energy consumption. If the exergy loss is economically not justified, we have to do with an error from the viewpoint of the second law analysis. The paper contains a thermodynamical analysis of the ratio of final and primary energy, as well as the analysis of the thermo-ecological cost and index of sustainable development concerning primary energy. Analyses of thermo-ecological costs concerning electricity and centralized heat production have been also carried out. The effect of increasing the share of high-efficiency cogeneration has been analyzed, too. Attention has been paid to an improved efficiency of the transmission and distribution of electricity, which is of special importance from the viewpoint of the second law analysis. The improvement of the energy effectivity in industry was analyzed on the example of physical recuperation, being of special importance from the point of view of exergy analysis.

The paper presents the results of optimizing the coefficient of the share of cogeneration expressed by an empirical formula dedicated to designers, which will allow to determine the optimal value of the share of cogeneration in contemporary cogeneration systems with the thermal storages feeding the district heating systems. This formula bases on the algorithm of the choice of the optimal coefficient of the share of cogeneration in district heating systems with the thermal storage, taking into account additional benefits concerning the promotion of high-efficiency cogeneration and the decrease of the cost of CO2 emission thanks to cogeneration. The approach presented in this paper may be applicable both in combined heat and power (CHP) plants with back-pressure turbines and extraction-condensing turbines.

The paper presents a modified algorithm for choosing the optimal coefficient of the share of cogeneration in district heating systems taking into account additional benefits concerning the promotion of highefficiency cogeneration and biomass cofiring. The optimal coefficient of the share of cogeneration depends first of all on the share of the heat required for preparing the hot tap water. The final result of investigations is an empirical equation describing the influence of the ratio of the heat flux for the production of hot tap water to the maximum flux for space heating and ventilation, as well as the share of chemical energy of biomass in the fuel mixture on the optimal value of the share of cogeneration in district heating systems. The approach presented in the paper may be applied both in back-pressure combined heat and power (CHP) plants and in extraction-condensing CHP plants.

Oxy-fuel combustion (OFC) belongs to one of the three commonly known clean coal technologies for power generation sector and other industry sectors responsible for CO2emissions (e.g., steel or cement production). The OFC capture technology is based on using high-purity oxygen in the combustion process instead of atmospheric air. Therefore flue gases have a high concentration of CO2- Due to the limited adiabatic temperature of combustion some part of CO2must be recycled to the boiler in order to maintain a proper flame temperature. An integrated oxy-fuel combustion power plant constitutes a system consisting of the following technological modules: boiler, steam cycle, air separation unit, cooling water and water treatment system, flue gas quality control system and CO2processing unit. Due to the interconnections between technological modules, energy, exergy and ecological analyses require a system approach. The paper present the system approach based on the 'input-output' method to the analysis of the: direct energy and material consumption, cumulative energy and exergy consumption, system (local and cumulative) exergy losses, and thermoecological cost. Other measures like cumulative degree of perfection or index of sustainable development are also proposed. The paper presents a complex example of the system analysis (from direct energy consumption to thermoecological cost) of an advanced integrated OFC power plant.

In order to analyze the cumulative exergy consumption of an integrated oxy-fuel combustion power plant the method of balance equations was applied based on the principle that the cumulative exergy consumption charging the products of this process equals the sum of cumulative exergy consumption charging the substrates. The set of balance equations of the cumulative exergy consumption bases on the ‘input-output method’ of the direct energy consumption. In the structure of the balance we distinguished main products (e.g. electricity), by-products (e.g. nitrogen) and external supplies (fuels). In the balance model of cumulative exergy consumption it has been assumed that the cumulative exergy consumption charging the supplies from outside is a quantity known a priori resulting from the analysis of cumulative exergy consumption concerning the economy of the whole country. The byproducts are charged by the cumulative exergy consumption resulting from the principle of a replaced process. The cumulative exergy consumption of the main products is the final quantity.

The paper is devoted to explication of one of the advantages of heat and electricity cogeneration, rarely considered in technical literature. Usually attention is paid to the fact that heat losses of the heat distribution network are less severe in the case of cogeneration of heat in comparison with its separate production. But this conclusion is also true in other cases when the internal consumption of heat is significant. In this paper it has been proved in the case of two examples concerning trigeneration technology with an absorption chiller cooperating with a combined heat and power (CHP) plant and CHP plant integrated with amine post-combustion CO2processing unit. In both considered cases it might be said that thanks to cogeneration we have to do with less severe consequences of significant demand of heat for internal purposes.

The paper is devoted to some problems connected with last modification of EU directive on energy efficiency, viz.: free choice of the measure concerning the improvement of energy efficiency, i.e. final or primary energy consumption, corresponding energy savings or energy-consumption index; however without cumulative consumption or cumulative savings of primary energy. In EU directive it has been stressed the importance of measurements systems (reliable measurement information); but has not been recommended any advanced validation of measurements results, nor energy auditing or algorithms of calculating the energy savings due to improvement of energy efficiency concerning large industrial plants. Evaluation of complex buildings should be realized by means of the system method (input-output analysis). The separate problem is devoted to application of thermo-ecological approach in the analysis of complete results of improving the energy efficiency. Human activity is connected with the depletion of nonrenewable resources, including primary energy, due to not only production of consumer goods but also the necessity of compensating the unfavourable effects of harmful emissions from energy-technological processes. Therefore the index of energy-ecological efficiency has been proposed as the most competent evaluation of improvement energy efficiency of production processes and systems.

This paper presents the Life Cycle Assessment (LCA) analysis concerning the selected options of supercritical coal power units. The investigation covers a pulverized power unit without a CCS (Carbon Capture and Storage) installation, a pulverized unit with a "post-combustion" installation (MEA type) and a pulverized power unit working in the "oxy-combustion" mode. For each variant the net electric power amounts to 600 MW. The energy component of the LCA analysis has been determined. It describes the depletion of non-renewable natural resources. The energy component is determined by the coefficient of cumulative energy consumption in the life cycle. For the calculation of the ecological component of the LCA analysis the cumulative CO2 emission has been applied. At present it is the basic emission factor for the LCA analysis of power plants. The work also presents the sensitivity analysis of calculated energy and ecological factors.

The paper presents the results of a simulative thermodynamic analysis of a multifuel CHP plant basing on the technological diagram of Avedøre 2. Calculations have been carried out for the operation of Avedøre 2 plant in the district heating mode. Several variants of simulation have been considered, determined by the choice of operation of the respective plants, viz. main boiler fired with natural gas, main and biomass boiler, main boiler and GT plant, joint operation of the main and biomass boiler and GT plant, main boiler (fired with heavy fuel oil or/and wood chips) and biomass boiler and GT plant. For each variants a diagram of iso-fuel curves has been developed, illustrating the variability of useful effects (power output and district heat) at various loads of the CHP steam part. In case of the variant in which the main boiler and GT are in operation with natural gas as fuel the exemplary energy indices were determined.