This paper reviews water electrolysis technologies for hydrogen production and also surveys the state of the art of water electrolysis integration with renewable energies. First, attention is paid to the thermodynamic and electrochemical processes to better understand how electrolysis cells work and how they can be combined to build big electrolysis modules. The electrolysis process and the characteristics, advantages, drawbacks, and challenges of the three main existing electrolysis technologies, namely alkaline, polymer electrolyte membrane, and solid oxide electrolyte, are then discussed. Current manufacturers and the main features of commercially available electrolyzers are extensively reviewed. Finally, the possible configurations allowing the integration of water electrolysis units with renewable energy sources in both autonomous and grid-connected systems are presented and some relevant demonstration projects are commented.

Hydrogen Production From Water Electrolysis: Current Status and Future Trends

A vacuum cleaner includes an electric air blower; a dust separator placed at an upstream side of the electric air blower and having a filtration filter for taking in dust-containing air sucked by the electric air blower and separating the dust from the air; and a dust accommodating section for accommodating the dust separated by the dust separator. The filtration filter includes a plurality of through-holes penetrating from an upstream surface at an upstream side to a downstream surface at the downstream side, and a central axis of the through-hole is inclined with respect to a normal line direction of a surface of the filtration filter.

Electric vacuum cleaner

This paper presents a new operational strategy for a small scale wind farm which is composed of both fixed and variable speed wind turbine generator systems (WTGS). Fixed speed wind generators suffer greatly from meeting the requirements of new wind farm grid code, because they are largely dependent on reactive power. Integration of flexible ac transmission systems (FACTS) devices is a solution to overcome that problem, though it definitely increases the overall cost. Therefore, in this paper, we focuses on a new wind farm topology, where series or parallel connected fixed speed WTGSs are installed with variable speed wind turbine (VSWT) driven permanent magnet synchronous generators (PMSG). VSWT-PMSG uses a fully controlled frequency converter for grid interfacing and it has abilities to control its reactive power as well as to provide maximum power to the grid. Suitable control strategy is developed in this paper for the multilevel frequency converter of VSWT-PMSG. A real grid code defined in the power system is considered to analyze the low voltage ride through (LVRT) characteristic of both fixed and variable speed WTGSs. Moreover, dynamic performance of the system is also evaluated using real wind speed data. Simulation results clearly show that the proposed topology can be a cost effective solution to augment the LVRT requirement as well as to minimize voltage fluctuation of both fixed and variable speed WTGSs.

A Variable Speed Wind Turbine Control Strategy to Meet Wind Farm Grid Code Requirements

A system and method for combining power from DC power sources. Each power source is coupled to a converter. Each converter converts input power to output power by monitoring and maintaining the input power at a maximum power point. Substantially all input power is converted to the output power, and the controlling is performed by allowing output voltage of the converter to vary. The converters are coupled in series. An inverter is connected in parallel with the series connection of the converters and inverts a DC input to the inverter from the converters into an AC output. The inverter maintains the voltage at the inverter input at a desirable voltage by varying the amount of the series current drawn from the converters. The series current and the output power of the converters, determine the output voltage at each converter.

Distributed Power Harvesting Systems Using DC Power Sources

The increasingly manifest impacts of global warming have made it a global priority to phase out the use of petrol and diesel as transportation fuels in favour of hydrogen. But the production of hydrogen by most existing technologies entails substantial use of fossil fuels and CO 2 emissions; indeed as much as 2.5–5 tonnes of carbon is released as CO 2 per tonne of hydrogen currently produced by conventional means. Hence the production of hydrogen can be ‘carbon-free’ only if it is generated by employing genuinely carbon-free renewable energy sources. The present review deals with the options, prospects, and challenges associated with this very high-priority area of global concern.

‘Renewable’ hydrogen: Prospects and challenges

To shorten a startup interval to reach a synchronizing condition, a phase difference and an amplitude difference between the grid voltage and the stator voltage of one phase of a winding are obtained. The difference in amplitude is decreased prior to or in parallel to synchronizing the stator voltage with the grid voltage. The calculated compensation phase compensation value is used as an initial value for synchronizing at the next synchronizing operation.

Wind Turbine Generator System

In a vacuum cleaner, both static pressure Hdata and a variation width ΔH in the static pressure appearing when a suction port is operated are detected from a pressure sensor provided at a rear side of a filter within a main body of the vacuum cleaner; a current variation width Δpbi appearing when the suction port is operated is detected from a current of a nozzel motor for driving a rotary brush stored in a power brush suction port; an air quantity at the suction port is calculated from the current, rotational speed of a fan motor and static pressure; command values are newly obtained by performing a fuzzy calculation with the variation width Δpbi, static-pressure command value Hcmd; the variation width ΔH and the static-pressure command value Qcmd; the variation width Δpbi and static-pressure command value Hcmd; and also the variation width ΔH and static-pressure command value Qcmd as the input thereto; the rotational speeds of the fan motor and nozzel motor are controlled from the result of the command values; and further optimum air suction force is automatically obtained, depending upon the suction port under use and cleaning floor plane.

Vacuum cleaner with fuzzy logic control

A wind power generation system includes: a wind turbine in which at least one blade is mounted on an axis; a generator for generating multiphase alternating current power by rotation of the axis; and a multiphase power conversion device for performing PWM-control for adjustment and output of generated power of the generator. With the configuration, the PWM-control provides for each phase a control paused period in which no overlap occurs. Thus, the pulse density between the control period and the control paused period of other phases is low, thereby generating high and low density in an inter-phase pulse.

Wind power generation system

This paper presents a combination system of wind energy conversion and hydrogen production. Hydrogen is expected as an alternative energy source in the future, and this is the best way to produce it from renewable energy like wind energy. On the other hand, the output of a wind generator, in general, fluctuates greatly due to wind speed variations, and thus the output fluctuations can have a serious influence on the power system operation. In the proposed system, a variable speed wind generator is adopted, and an electrolyzer is installed in parallel with it for hydrogen production. Output power from the wind generator is smoothed and supplied to the power system as well as to the electrolyzer based on the cooperative control method. The performance of the proposed system is evaluated by simulation analyses, in which simulations are performed by using PSCAD/EMTDC.

Output Power Smoothing and Hydrogen Production by Using Variable Speed Wind Generators

Recently, wind energy conversion system using a Doubly-Fed Synchronous Generator (DFSG) has attracted an interest. This system can control rapidly real and reactive power output independently by secondary AC excitation. Furthermore, since wind turbine can be operated in variable speed, fluctuations of the output due to changing wind speed in short period can be reduced. This paper proposes a new control method for this system to enhance the transient stability of neighboring induction generators in the same wind farm.

Motoo Futami

Papers

Wind Turbine Generator System

Vacuum cleaner with fuzzy logic control

Wind power generation system

Output Power Smoothing and Hydrogen Production by Using Variable Speed Wind Generators

A New Control Method for Wind Energy Conversion System Using a Doubly-Fed Synchronous Generator