Power-to-gas technology plays a key role in the success of the energy transformation. This paper addresses issues related to the legal and technical regulations specifying the rules for adding hydrogen to the natural gas network. The main issue reviewed is the effects of the addition of hydrogen to natural gas on the durability of diaphragm gas meters. The possibility of adding hydrogen to the gas network requires confirmation of whether, within the expected hydrogen concentrations, long-term operation of gas meters will be ensured without compromising their metrological properties and operational safety. Methods for testing the durability of gas meters applied at test benches and sample results of durability tests of gas meters are presented. Based on these results, a metrological and statistical analysis was carried out to establish whether the addition of hydrogen affects the durability of gas meters over time. The most important conclusion resulting from the conducted study indicates that, for the tested gas meter specimens, there was no significant metrological difference between the obtained changes of errors of indications after testing the durability of gas meters with varying hydrogen content (from 0% to 15%).

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Abstract. Over the last years, the European Union has seen a rapid increase in installed capacity of generating units based on renewable energy sources (RES). The most significant increase in installed capacity was recorded in 2015, in wind farms and solar PV installations. One of the most serious is the volatile character of RES on a time basis. Therefore, for a further expected increase in the use of RES and their effectiveness improvements, investments are needed allowing for electricity to be stored. One of the electricity storage options is to use excess electricity in order to produce hydrogen by electrolysis of water. Although this process plays a marginal role in obtaining hydrogen on a worldwide basis due to high costs, experience in recent years has shown that periodically low (negative) electricity prices, developing on the power exchanges in the situation where there is surplus electricity available, affect economic requirements for hydrogen production technologies. The paper shows activities undertaken by European countries (mainly Germany) aiming at making it possible for hydrogen to be stored in the natural gas grids. A particular attention is given to material resource issues and possible operational problems that might arise while blending natural gas with hydrogen into the grid. The experiences of selected European countries are of particular interest from the Polish perspective, having regard to significant increase of RES in electricity generation during the last few years and adopted objectives for the growing importance of RES in the Poland's energy balance.

Abstract. The World market of liquefied natural gas (LNG) is growing rapidly. In 2015 LNG production exceeded 333 bcm with its predicted increase up to 450 bcm in 2019. The analysis of LNG role in natural gas import to the EU in recent years shows variability: LNG share in overall import reached 25% in 2011 and it went down to 15% in 2014. The smaller demand for natural gas including LNG in the EU can be due to, among others, a slower economic growth and a dynamic development of the use of renewable energy sources. The article shows the role of natural gas in the structure of consumption of primary energy as well as the changes in demand for natural gas in the years 2007-2014 for the main groups of end users: industry, energy production and individual households. The biggest fall in demand for natural gas has been observed in energy production sector in recent years. This publication continues to analyse the structure of natural gas supplies to the EU, with special emphasis on the directions of LNG import to the countries such as: The UK, Spain, France, Greece, Belgium, Portugal, Italy, Lithuania and The Netherlands. The significance of LNG in the balance of consumption of natural gas in these countries has been presented as well as the infrastructure connected with LNG and plans of development of regasification terminals. In the summary the most important conclusions have been drawn and a chance of the increase in significance of the role of LNG in the balance of natural gas supplies has been pointed out, which is due to the steep fall of LNG prices which has taken place in recent years.