Case Studies of Wind Hydrogen System (part 1)

Water electrolyzers have been designed in the past for continuous or discontinuous operation with grid current converted to DC current. Most of the case studies reported in the literature refer to stand-alone systems. In fact, several of these stand-alone systems have part of their auxiliaries connected to the grid, or use the electrical grid as backup power.

A wind-hydrogen system of 20 kW installed power has been developed, constructed, and optimized at the Fachhochschule Wiesbaden in Germany since 1985. A 20 kW wind energy converter, designed for stand-alone operation, feeds DC to a pressurized alkaline electrolyzer of 20 kW, and the produced hydrogen is used in two gas motor generators of 8 and 4 kW electrical output. The overall energy effi ciency from wind electricity to gas generator electricity is around 15%.

At the University of Stralsund in Germany, a 100 kW wind turbine and a 20 kW alkaline electrolyzer supplying hydrogen at 25 bars to a storage tank of 8 m3 have been in operation for several years. According to the wind speed, the asynchronous wind generator can be operated at 1000 or 1500 rpm producing 20 or 100 kW of electricity, respectively. Both the static and the dynamic behaviors of the wind-hydrogen system were investigated, and an electrolyzer efficiency of approximately 65% with respect to the HHV has been reported.

The Hydrogen Research Institute in Canada has developed and tested a stand-alone renewable energy system composed of a 10 kW wind turbine, a 1 kWpeak photovoltaic array, a 5 kW alkaline electrolyzer, and a 5 kW PEM fuel cell. The components of the system are electrically integrated on a 48 V DC bus.

A small stand-alone, wind-powered hydrogen production plant was designed, constructed, and tested in Italy, at the National Agency for New Technologies, Energy and the Environment. The main aim of the project was to study the control of a wind turbine to produce a smooth power output, the tolerance of an electrolyzer to fluctuating power inputs, and the overall economics of a wind-hydrogen system.

The system was composed of a 5.2 kW wind turbine with a synchronous generator at variable speed, a 2.25 kW electrolyzer, and a 330 Ah battery bank. The variable frequency AC power output from the turbine was rectified and supplied to the electrolyzer. Hydrogen purity remained satisfactory even at low-capacity factors, with oxygen content in hydrogen in the range 0.15–0.35 vol%, although the efficiency of the electrolyzer stack (50%) was lower than state-of-the-art electrolyzers (70%).