## 1 Introduction
\begin{table}
\begin{tabular}{c l l} \hline
**Energy Source** & **Features** & **Features/Sulfide-Driven Fuel Cell** \\ \hline \multirow{4}{*}{Heat power stations (oil, gas, coal)} & Carbon emissions; expensive production; & Carbon free; less operational costs; \\  & heavy operation; waste handling & easy switch-on/off; no waste Capital \\  & Capital costs, \$500-5000/kW & costs, \$2000/kW \\  & Operational costs, \$6-15 \(\upbar\upbar\upbar\upbar\upbar\up\bar\upbar\upbar\upbar\up\)/MWh & Operational costs, \$10 \(\upbar\upbar\upbar\upbar\)/MWh \\ \hline \multirow{4}{*}{Nuclear fuel} & Expensive fuel production; heavy and & \\  & hazardous operation; expensive and & \\  & dangerous waste storage. & Less operational costs; easy \\  & Capital costs, \$6000/kW & switch-on/off; no waste \\  & Operational costs, \$15 \(\upbar\upbar\upbar\upbar\)/MWh & \\ \hline \multirow{4}{*}{Wind} & Weather dependent; impact on environment & \\  & Capital costs, \$1900/kW & Weather independent, positive \\  & Operational costs, \$10 \(\upbar\upbar\)/MWh & environmental impact \\ \hline \multirow{4}{*}{Solar} & Weather dependent; environmental hazards & \\  & (soil and biodiversity degradation) & Weather independent, positive \\ \cline{1-1}  & Capital costs, \$2600/kW & environmental impact \\ \cline{1-1}  & Operational costs, \$10 \(\upbar\)/MWh & \\ \hline \end{tabular}
\end{table} 
Table 2: Comparison of sulfide-driven fuel cells and other fuels. Data for capital costs for the known fuels are extracted and extrapolated from References [19] and data for operational costs, from References [20]. Some estimates of the capital and operational costs for energy production by different methods and facilities are also shown here. One can see that alongside environmental advantages, the capital and operational costs for the SDFC-based method are comparable to those of wind and solar facilities, and even lower than those of nuclear power plants. In a previous paper [21], a similar fuel cell operating in aqueous phase was considered, but the oxidation yielded only elemental sulfur, which blocked the electrodes. The apparent electrode surfaces were enhanced by adding graphite beads. Additionally, [PERSON] et al. [22] applied a fuel cell to oxidize sulfide to sulfur by ferric tons, but at very low current densities. There is a paper by [PERSON] and [PERSON] [23] demonstrating best current densities in a sulfide-driven fuel cells operating in liquid phase, but in a strongly alkaline medium (3 M NaOH). This medium is inadmissible for sea water because of the threat of pollution and damage to aquatic life. In a recent work, [PERSON] et al. [24] tested a sulfide fuel cell with proton exchange membrane and platinum/ruthenium catalyst, but very low current and power densities were reached. Some studies propose simultaneous production of hydrogen and electricity generation in a membrane electrolyzer [25] and by hydrogen sulfide decomposition, cf. [PERSON] et al. [26]. The subject of this presentation is the experimental study of the performance of a sulfide-driven fuel cells operating under environmentally-friendly conditions. Parameters such as inlet sulfide concentration, fuel cell geometry and size, aeration type, effect of the separation membrane and cell efficiency were verified and tested under conditions compatible with those in genuine marine water in the Black Sea.