Experimental Study On The Hydrogen Production With RED Reactor Powered By Concentration Gradient Energy

Salinity gradient energy(SGE)has aroused extensive attention as a clean and renewable new energy source.As a kind of chemical potential energy contained in solutions of different concentrations,it exists widely in the junction of rivers and seas or salt lakes.At the same time,there are a large amount of low-grade heat(LGH)generated in the industrial production process.Due to the low temperature of low-grade heat energy,it's difficult to be utilized efficiently.The use of low-grade heat energy to drive hydrogen production has a positive significance for reducing the cost of hydrogen production and improving energy efficiency.Basic working principle of the RED hydrogen production technology driven by low-grade heat is that the LGH is firstly converted to the SGE by distillation,and then it is converted to hydrogen energy by reverse electrodialysis reactor.Our research team proposed a novel method of hydrogen production with RED reactor,which powered by the SGE of solution and available in alkaline environment.The OH~-generated by the reduction reaction of the cathode and the OH~-consumed by oxidation reaction of the anode reach a balance under the action of membrane potential.So all around the hydrogen production process,no additional electrolyte needs to be added to the electrode solution,which is beneficial to reduce the cost of hydrogen production.In order to verify that the RED reactor can convert the SGE of solution into hydrogen energy,and explore the infiuence of key operating parameters on the energy conversion process,an experimental system of hydrogen production with RED reactor powered by SGE was developed.In this paper,NaCl and NaOH aqueous solution were selected as the working solution and electrode rinse solution respectively.By changing the key operating parameters(such as the inlet concentration of concentrated and diluted solution,the flow velocity of working solution and electrode rinse solution,the number of membrane pairs and the output current),the effects on the hydrogen production rate,hydrogen production and energy conversion efficiencies were investigated experimentally.The results show that under the condition of external circuit short connection,the hydrogen production rate and efficiency of the RED reactor get further increased with the increase of the inlet concentration of the concentrated solution,while the energy conversion efficiency decreases.When the concentration of concentrated solution is fixed,with the increase of the diluted solution,there is an optimal concentration ratio exist to make the hydrogen production rate and efficiency reach the maximum,but the energy conversion efficiency generally shows an increasing trend;The increase in the flow velocity of working solution is beneficial to improve the hydrogen production rate and efficiency,and the net energy conversion efficiency increases first and then decreases due to the pump power consumption.It's also can be seen that the output current and theoretical hydrogen production rate of the RED reactor is found to be enlarged by speeding up the flow rate of electrode solution.Besides,the more the membrane pairs are,the higher the hydrogen production rate and efficiency are,but the lower the energy conversion efficiency is;Moreover,the hydrogen production rate and efficiency of the RED reactor are benefit a lot from increasing output current,while its output electrical energy,total output energy and net energy conversion efficiency all show a trend of increasing first and then decreasing.