This paper contains the results of a study in which a novel approach using continuous time notation was applied in the search for the optimum capacity of a heat accumulation tank to be combined with an existing CHP (combined heat and power) plant. The necessary condition associated with the economic profitability of the application of heat accumulation tanks in CHP plants is based on the condition that the profit from the exploitation of the modernized CHP plant does not decrease in relation to this profit before the process was initiated. Hence, the applied methodology provides a dependence that has universal application as it can be used to establish the optimal capacity of a heat accumulation tank suitable for any CHP plant design, i.e., for any thermal capacity of such a plant. The results also demonstrated that the specific enthalpies of the extracted steam before the base load heater and the maximum increase of the flow rate of the extracted steam feeding the base load heater in winter form the only necessary inputs for such calculations. The construction of the heat accumulation tank is only profitable for the case when the difference in the purchase prices at the times corresponding to peak load and base load electricity demand is sufficiently high.

This paper presents the results of analysis of energy and economic efficiency of the hierarchical gas-gas engine, with a note that a trigeneration system was analyzed, in which the production of electricity, heat and cold are combined. This solution significantly increases the energy efficiency of the gas and gas system compared to a system without cold production. The analysis includes a system comprising a compressor chiller which is driven by an electric motor in the system, as well as a system applying the mechanical work that is carried out via a rotating shaft of rotor-based machines, i.e., a gas turbine and a turboexpander. The comfort of the regulation of the refrigerating power rather promotes the use of a solution including an electric motor. Analysis contains also a schematic diagram of the system with a absorption chiller, which is driven by low-temperature enthalpy of exhaust gases extracted from a hierarchical gas-gas engine. Application of turboexpander with heat regeneration in the trigeneration system is also analyzed. Based on the multi-variant economic and thermodynamic calculations, the most favorable system variant was determined using, among others, the specific cost of cold production.

The paper presents the results of measurements and calculations concerning the influence of weather conditions on the operation of wet cooling towers of 905 MWe units of the Opole Power Plant (Poland). The research concerned the influence of temperature and relative humidity of air, wind and power unit load on the water temperature at the outlet from the cooling tower, the level of water cooling, cooling efficiency and cooling water losses. In the cooling water loss, the evaporation loss stream and the drift loss stream were distinguished. In the analyzed operating conditions of the power unit, for example, an increase in $T_{amb}$ air by 5 °C (from $20–22°\mathrm{C}$ to $25–27°\mathrm{C}$) causes an increase in temperature at the outlet of the cooling tower by $3–4°\mathrm{C}$. The influence of air temperature and humidity on the level of water cooling $\mathsf{\Delta }{T}_w$ and cooling efficiency $\epsilon$ were also found. In the case of $\mathsf{\Delta }{T}_w$, the effect is in the order of $0.1–0.2°\mathrm{C}$ and results from the change in cooling water temperature and the heat exchange in the condenser. The ε value is influenced by air temperature and humidity, which determine the wet bulb temperature value. Within the range of power changes of the unit from $400$ to $900\mathrm{MWe}$, the evaporated water stream ${\dot{m}}_{ev}$, depending on the environmental conditions, increases from $400–600\mathrm{tons}/\mathrm{h}$ to the value of $1000–1400\mathrm{tons}/\mathrm{h}$. It was determined that in the case of the average power of the unit at the level of $576.6\mathrm{MWe}$, the average values of the evaporation and drift streams were respectively $0.78\%$ and $0.15\%$ of the cooling water stream. Using statistical methods, it was found that the influence of wind on the level of water cooling, cooling efficiency and cooling water losses was statistically significant.