A maximum current point tracking algorithm for photovoltaic hydrogen production

Integrating electrolyzers with photovoltaic (PV) arrays allows clean hydrogen production. Today's solar electrolyzers require multiple power devices for maximum power point tracking (MPPT) and optimal power delivery. Each of these power devices (inverters, rectifiers, and transformers) introduces significant cost and energy loss. Moreover, megawatt-scale electrolyzers present scalability challenges as the electrical current required for each electrolyzer stack far exceeds the capacity of a conventional power converter. Furthermore, the amount of hydrogen produced through water electrolysis is directly proportional to the current, not the power, as each hydrogen molecule requires two electrons to produce. This paper describes two major innovations for solar electrolyzers. One is a new direct-coupled system topology for MPPT without a central power converter, which can deliver large currents to electrolyzer stacks. The new system has a ∼50 % lower levelized cost of electricity than today's solar electrolyzers, ∼15 % from the reduced system cost by eliminating most power devices and ∼35 % from the improved system energy efficiency from ∼75 % to 99 %. The second innovation is a maximum current point tracking (MCPT) algorithm specifically tailored to maximize photovoltaic hydrogen production. Simulation and experimental results demonstrate that the MCPT algorithm implemented in the new system topology delivers ∼2.5 % more charge than traditional MPPT algorithms. It is also shown that the MCPT algorithm can incorporate voltage regulation so the operating voltage of the system remains within the manufacturer-specified optimal range 94 % of the time, minimizing under-voltage or over-voltage operation. These results validate the MCPT algorithm implemented in the new system topology as a low-cost and efficient solution for large-scale photovoltaic hydrogen production.