The use of hydrogen as a non-emission energy carrier is important for the innovative development of the power-generation industry. Transmission pipelines are the most efficient and economic method of transporting large quantities of hydrogen in a number of variants. A comprehensive hydraulic analysis of hydrogen transmission at a mass flow rate of 0.3 to 3.0 kg/s (volume flow rates from 12,000 Nm3/h to 120,000 Nm3/h) was performed. The methodology was based on flow simulation in a pipeline for assumed boundary conditions as well as modeling of fluid thermodynamic parameters for pure hydrogen and its mixtures with methane. The assumed outlet pressure was 24 bar (g). The pipeline diameter and required inlet pressure were calculated for these parameters. The change in temperature was analyzed as a function of the pipeline length for a given real heat transfer model; the assumed temperatures were 5 and 25 °C. The impact of hydrogen on natural gas transmission is another important issue. The performed analysis revealed that the maximum participation of hydrogen in natural gas should not exceed 15%–20%, or it has a negative impact on natural gas quality. In the case of a mixture of 85% methane and 15% hydrogen, the required outlet pressure is 10% lower than for pure methane. The obtained results present various possibilities of pipeline transmission of hydrogen at large distances. Moreover, the changes in basic thermodynamic parameters have been presented as a function of pipeline length for the adopted assumptions.

No abstract

During the natural gas pipeline transportation process, gas stream pressure is reduced at natural gas regulation stations (GRS). Natural gas pressure reduction is accompanied by energy dissipation which results in irreversible exergy losses in the gas stream. Energy loss depends on the thermodynamic parameters of the natural gas stream on inlet and outlet gas pressure regulation and metering stations. Recovered energy can be used for electricity generation when the pressure regulator is replaced with an expander to drive electric energy generation. To ensure the correct operation of the system, the natural gas stream should be heated, on inlet to expander. This temperature should be higher than the gas stream during choking in the pressure regulator. The purpose of this research was to investigate GRS operational parameters which influence the efficiency of the gas expansion process and to determine selection criteria for a cost-effective application of turboexpanders at selected GRS, instead of pressure regulators. The main novelty presented in this paper shows investigation on discounted payback period (DPP) equation which depends on the annual average natural gas flow rate through the analyzed GRS, average annual level of gas expansion, average annual natural gas purchase price, average annual produced electrical energy sale price and CAPEX.

This paper reviews the coal policy of Poland. It analyzes the forecasts of production and consumption of hard coal, the size of exports and imports and its importance for the energy sector on the basis of strategic documents. The main aim of the article is to show the role of hard coal in the fuel -energy balance of Poland until 2050. The adoption of appropriate assumptions for each scenario, including the maximum supply of hard coal from domestic mines, coal price curves, CO 2 emission allowances and several calculations performed allowed to obtain certain results on the basis of which the future role of hard coal was determined.Keywords: hard coal, forecast, energy policy, power sector, energy security, coal reserves, coal consumption W artykule dokonano przeglądu polityki państwa polskiego wobec górnictwa węgla kamiennego. Przeanalizowano jak kształtowały się w dokumentach strategicznych prognozy w zakresie wydobycia i zużycia węgla kamiennego, wielkości eksportu i importu oraz jego znaczenie dla sektora energetycznego. Głównym celem artykułu było ukazanie roli węgla kamiennego w bilansie paliwowo-energetycznym Polski w perspektywie do 2050 r. Po przyjęciu odpowiednich założeń dla poszczególnych scenariuszy, m.in. dotyczących maksymalnej podaży węgla kamiennego z krajowych kopalń oraz ścieżek cenowych węgla i uprawnień do emisji CO 2 oraz przeprowadzeniu obliczeń uzyskano wyniki, na podstawie których określono przyszłą rolę węgla kamiennego.

Due to ecological and economic advantages, natural gas is used as an alternative fuel in the transportation sector in the form of compressed natural gas (CNG) and liquefied natural gas (LNG). Development of infrastructure is necessary to popularize vehicles that use alternative fuels. Selected positive factors from EU countries supporting the development of the CNG market were discussed. The process of natural gas vehicle (NGV) fast filling is related to thermodynamic phenomena occurring in a tank. In this study, the first law of thermodynamics and continuity equations were applied to develop a theoretical model to investigate the effects of natural gas composition on the filling process and the final in-cylinder conditions of NGV on-board composite cylinder (type IV). Peng–Robinson equation of state (P-R EOS) was applied, and a lightweight composite tank (type IV) was considered as an adiabatic system. The authors have devised a model to determine the influence of natural gas composition on the selected thermodynamic parameters during fast filling: Joule–Thomson (J-T) coefficient, in-cylinder gas temperature, mass flow rate profiles, in-cylinder mass increase, natural gas density change, ambient temperature on the final natural gas temperature, influence of an ambient temperature on the amount of refueled natural gas mass. Results emphasize the importance of natural gas composition as an important parameter for the filling process of the NGV on-board composite tank (type IV).