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.

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.

Compressed natural gas can be globally used as fuel for combustion engines to reduce CO2 emission without negative impact on economy. Lack of refueling infrastructure is one of reason why NGVs shares only ~1.6% in total vehicle fleet worldwide. Operational tests of CNG home fast refueling station were performed to investigate: (i) natural gas demand, m3/h; (ii) energy consumption, kW/h; and (iii) total cost of one refueling. Two scenarios for operational tests were developed to monitor and collect data. Safety tests for leakage, fill pressure change, interrupted power and gas supply, temperature, and unexpected failures were performed. This article present results of operational and safety tests of compressed natural gas home, fast refueling station (CNG-HRS) based on one stage hydraulic compressor. The average duration of HRS full operating cycle was 7 h and 32 min (buffering and refueling mode). The average electric energy and natural gas consumption for one full cycle was 5.52 kWh and 7.5 m3, respectively. Safety tests results for leakage, fill pressure change, interrupted power and gas supply, temperature and unexpected failures demonstrated valid operation of HRS which positively affects the general safety level. To compare HRS with large scale CNG refueling infrastructure the costs of 1 Nm3 CNG was estimated for both solutions. Results shows that home refueling appliance might be become a solution for filling the gap in CNG refueling infrastructure.

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