Electromobility and electric cars are the words that began to gain significance in the social discourse in Poland especially intensively since 2017. Then, along with the announcement of the „Plan for the Development of the Electromobility Market in Poland”, government declarations appeared regarding one million electric cars that are to be used on Polish roads by 2025. It is already known today that such a result in Poland is impossible to achieve in the assumed time. According to the report of the Polish Alternative Fuels Association-PSPA (Polish EV Outlook 2020), in the event of introducing subsidies for the purchase of cars or subsidies, such as the possibility of 100% VAT deduction by buyers of such vehicles, the number of electric cars in Poland in 2025 could be over 280 thousand pcs. Without such government support, the Polish electric car park will be twice smaller. High prices of electric cars are one of the key barriers limiting Poles in making decisions related to the purchase of a vehicle. The aim of this article is to analyse the current state of the social environment in relation to the topic of ecological, electric cars. To what extent is it beneficial for the potential car owner to change from a traditional (petrol or diesel) car to an electric car due to purely financial benefits and other aspects? The article consists of an overview – presenting aspects related to the socio-economic benefits of buying an electric car. It also contains specific calculations regarding the profitability of using such a car in Polish conditions.

Using loans is an effective solution for the investment and construction of energy works in general and power plants in particular, especially for developing countries. In economic and financial studies of the project investment preparation stage, the options of using capital and paying interest will be taken into account to minimize risks and increase the project’s ability to pay due debts. However, it is difficult to know which loan repayment option is the most beneficial for the project and when the risk is for the project in the context of debt repayment. The current economic and financial analysis of the project mainly focuses on determining the feasibility of the project through basic parameters, such as net present value (NPV), benefit – cost – ratio (B/C), internal rate of return (IRR), profitability index (PI) and payback period (PP). These parameters do not indicate the most difficult time to pay off the project’s loans. This paper analyzes two options for repayment of long-term loans in Vietnam using the case study of Son La hydropower plant to clarify the above difficult times and recommend a suitable repayment plan for the power project. The analytical method is used to actualize the cash flow of capital and interest during the construction and operation of the works. In Option 1, the debt is paid annually for interest and capital with a constant amount of money during the repayment period. In Option 2, the original dept without interest is paid with a constant amount of money during the repayment period, the interest (due to the remaining original capital) must be paid in the year when the interest is incurred. The study results show that the amount of the annual payment in option 1 is smaller than in Option 2 in the first four years (of ten years of debt repayment). Thus, capital and interest payment in Option 2 may be more detrimental than Option 1 in the first three years of debt repayment, and the amount of money from debt repayment is greater than the profit obtained from power generation. Thus, depending on the profit in the first years when the power plant comes into operation, the investor needs to decide on a reasonable way to repay the loan so that the project can self-finance.

The average grades of copper mines are dropped by extracting high grade copper ores. Based on the conducted studies in the mine field, the uncertainty of economic calculations and the insufficiency of initial information is observed. This matter has drawn considerations to processing methods which not only extracts low grade copper ores but also decreases adverse environmental impacts. In this research, an optimum cut-off grades modelis developed with the objective function of Net Present Value (NPV) maximization. The costs of the processing methods are also involved in the model. In consequence, an optimization algorithm was presented to calculate and evaluate both the maximum NPV and the optimum cut-off grades. Since the selling price of the final product has always been considered as one of the major risks in the economic calculations and designing of the mines, it was included in the modeling of the price prediction algorithm. The results of the algorithm performance demonstrated that the cost of the lost opportunity and the prediction of the selling price are regarded as two main factors directed into diminishing most of the cut-off grades in the last years of the mines’ production.

The problem of the proper functioning of Park-and-Ride facilities seems to be of key importance for ensuring appropriate transport in cities in which the intensity of road traffic is systematically increasing, together with the increase of environmental pollution (air pollution, noise etc.). The attractiveness of a car park of this kind seems obvious – instead of a burdensome journey in one’s own car, one changes the vehicle to fast municipal public transport or another means of transport (a bike, a scooter), or reaches the destination on foot. This results in benefits – above all in terms of comfort (shortening the time of the journey), health advantages etc. As has been proven by experiments, facilities of this kind are an expensive investment, the location of which (e.g. stand-alone) does not always ensure full utilization. The concept presented in the article assumes the possibility of a gradual extension of the multistorey car park following the increase of the demand. The article attempted to demonstrate that one of the sources of increasing attractiveness is the appropriate location (guaranteeing easy commute to the car park), the possibilities to continue the journey in an attractive way, then increasing the attractiveness through the possibility to use various services (shopping, the gym, the swimming pool, cinema, restaurants) and thirdly: the plan of launching the car park and its utilization in the life cycle should ensure the possibility of flexible reacting to changes of the demand (the experiences of the ongoing pandemic indicate that there is no guarantee of ensuring systematic demand increase). An element which also seems significant is the limitation of costs in the initial stage of investments of this kind with the possibility of gradual extension following the change of user habits.

Kolektory słoneczne są głównymi elementami solarnych systemów grzewczych. Praca tych urządzeń polega na konwersji energii promieniowania słonecznego na ciepło czynnika roboczego. Czynnikiem tym może być zarówno ciecz (glikol lub woda), jak i gaz (powietrze). Ze względu na konstrukcję wyróżnia się kolektory płaskie, próżniowe, próżniowo-rurowe i skupiające. Kolektory płaskie są stosowane przede wszystkim w budynkach, w których potrzeby cieplne są niskie lub średnie, czyli na przykład w gospodarstwach domowych. Rozwój kolektorów został ukierunkowany na zwiększenia wydajności oraz poprawy efektywności ekonomicznej inwestycji. W artykule oceniono wpływ zmiany powierzchni płaskich kolektorów słonecznych na opłacalność ekonomiczną inwestycji. Do analizy wytypowano dom jednorodzinny, zlokalizowany w województwie małopolskim, w którym instalacja przygotowania ciepłej wody użytkowej została rozbudowana o system solarny. System ten składa się z płaskich kolektorów, o łącznej powierzchni absorberów 5,61 m2. Jako czynnik roboczy w instalacji stosowany jest glikol. W celu poprawy efektu ekonomicznego zaproponowano zwiększenie powierzchni absorberów. Na podstawie trzyletnich pomiarów nasłonecznienia oraz efektów cieplnych instalacji, stworzono model ekonomiczny służący do oceny opłacalności zwiększenia powierzchni kolektorów słonecznych. Obliczenia z użyciem modelu promieniowania HDKR wykonano w środowisku Matlab dla lokalizacji Tarnów (najbliższej instalacji). Ponadto na podstawie rzeczywistych pomiarów z tej instalacji, odzwierciedlających wpływ wielu niemierzalnych czynników na efektywność przetwarzania energii słonecznej, wykonano symulacje efektu ekonomicznego dla różnych wielkości zapotrzebowania na ciepło. Otrzymane wyniki uogólniono, co daje możliwość ich wykorzystania w procesie doboru wielkości powierzchni kolektorów w przypadku podobnych instalacji.

Nucleopolyhedrovirus (NPV) of the satin moth Leucoma (=Stilpnotia) salicis L. was produced by infecting the larvae with the LesaNPV strain obtained from epizootic center in Katowice. The infected larvae were reared under laboratory, greenhouse and insectarium conditions. Because L. salicis can not be reared on a semi-synthetic food, the insects were maintained on natural products. Efficiency of the mass virus production depended on an insect growth stage, virus concentration and number of infected larvae in a rearing container. The fourth-instar larvae were the best for LesaNPV replication. Inoculation of younger larval stages (third instar stadium) provided less number of inclusion bodies (insects were dying sooner and did not meet their maximum body weight). On the contrary inoculation of older stages (fifth and sixth instars) resulted in slower virus replication and low larva mortality. The virus concentration of 3 x 10⁹ of inclusion bodies per container was the optimum inoculum for the mass virus production (double infection with the virus concentration of 1.5 x 10⁹ inclusion bodies/1000 larvae). The larvae reared at high-density became more infected and it caused their earlier death and in consequences low virus efficiency. Rearing the insect at low density (less than 10 larvae per 1.0 L container) was conducive for both an increase of insect body mass and virus replication as well. The highest number of inclusion bodies per one larva(5.3 x 10⁹ – 7.7 x 10⁹) and the highest total number of inclusion bodies (152 x 10¹¹ – 188 x 10¹¹) were achieved under these rearing conditions in a greenhouse and insectarium.