## 1 Introduction
\begin{table}
\begin{tabular}{l c c c c} \hline \hline \multicolumn{1}{c}{**(a)**} & & & \\ \hline  & **GEV Coselle** & **GEV Optimum** & **VOTRANS** & **Knutsen PNG** \\ \hline _containment_ & coiled X-80 steel pipe & API 5 LX80 steel cylinders & X-80 steel cargo & tank cylinders \\  & forming a carousel & pipes & vertical tanks modules or horizontal pipes & vertically stacked \\ _arrangement_ & coiled pipe in holds & horizontal in holds & 125 & 250 \\ _gas press. (bar)_ & 200–275 & ambient & ambient & \(-\)30 & ambient \\ _gas temp. (\({}^{\circ}\)C)_ & 0.12–0.18 & 0.4 & 0.35–0.39 & 0.21 \\ _carcapcontainer_ & & advanced for 5.5 & advanced & concept \\ _weight ratio_ & & & & \\ _development stage_ & advanced concept & & & \\ _capacity (MNm3)_ & 1.5–15 & 5.5–12.5 & 2–30 & 2–35 \\ \hline \hline \multicolumn{1}{c}{**(b)**} & & & \\ \hline  & **TOG** & **TransCanada** & **CeTech** & **GASVESSEL** \\ \hline \multirow{4}{*}{_containment_} & composite HDPE and fiberglass cylinders & composite & composite or X-80 steel & composite \\  & (MEGC) & reinforced steel & pipes & reinforced steel \\  & container or modular & & & \\ _arrangement_ & cassettes with vertical & GTMs stacked & vertical/horizontal & vertical \\  & cylinders & & & \\ _gas press. (bar)_ & 250 & 206 & 150–250 & 300 \\ _gas temp. (\({}^{\circ}\)C)_ & ambient/\(-\)30 & ambient & ambient/\(-\)30 & ambient \\ _cargolcontainer_ & & & & 0.7 (composite) & 1.5 \\ _weight ratio_ & & & & 0.24 (X-80 steel) & \\ _development stage_ & concept & concept & concept & advanced concept \\ _capacity (MNm3)_ & 7 & 0.3–3 & 7–15 (composite) & 12 \\  & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: CNG vessel technologies, part a,b. which is then partially wasted during FFP. In turn, the filling time, underfilling, and compression work also depend on the gas composition, ambient temperature, storage type, and compressor performance. The first FFP model was presented by [PERSON]. In [6], with reference to a CNG storage cylinder, he found a rise of 40 \({}^{\circ}\)C of the storage gas temperature. It is also shown by [PERSON] that the fast fill of CNG cylinders, at 20 \({}^{\circ}\)C ambient temperature, typically achieves a fill efficiency of 80%. In [7], two methods are compared for storing fuel in CNG stations, namely buffer storage and three pressure levels cascade storage systems. The authors found that the filling time is lower and the charged mass is higher with buffer storage, whilst the compressor work is lower with cascade storage. In [8], the authors studied an FFP based on a three-stage compressor and both buffer and cascade configurations, which are referred to as a single storage system (SSS) and cascade storage system (CSS). The optimum amounts of inter-stage pressure have been found for every configuration using the particle swarm optimization (PSO) algorithm. They too found that SSS allows a low refueling time and high filling ratio, while CSS allows reducing the energy consumption. The influence of NG composition is investigated in [9] using the AGA8 EOS to calculate the thermodynamic properties of NG with methane percentage in the field 87-98.6%. They found that the composition has a small effect on the filling time but significant effects on the charged mass, with variations around 20%. In another work [10], the same authors, using a detailed model of a reciprocating compressor with automatic valves, found that natural gas composition, with methane percentage varying from 79% to 98%, has significant effects on compressor performance. The consuming work per cycle and the mean discharge temperature increases with methane percentage. In [11], the authors investigate the FFP of NG in Type-III cylinders, which have a metal liner and a full-wrapped composite reinforcement, for heavy-duty vehicles with and without active heat removal in order to improve the fill efficiency. The active heat removal system involves placing cooling coils inside the cylinder through which a coolant is circulated.