Fuel Cell Based Renewable Energy System for Off-grid Applications: Conceptual Design

The solar power changes during the day is the main challenge of using the photovoltaic panels in high reliability off-grid power system. Batteries are a primary solution for this problem; low gravimetric energy density, low life time and self-discharging are the main problem in long-term using of batteries for energy storage in off-grid solar power systems. In this paper, a fuel cell based hybrid solar power system proposed for sustainable power generation in off-grid application. The proposed hybrid power system includes solar panel, PEM fuel cell and low capacity batteries. In this system, a green energy storage system based on hydrogen energy is used for long-term energy storage. This system is suitable for low solar radiation areas such as the western and northern regions of Iran. A water electrolyzer unit is used for hydrogen production when sufficient solar power is available and the PEM fuel cell stack provides the load power while the solar power is insufficient. Conceptual investigation of the proposed hybrid power system is done by using this system for off-grid application (telecommunication tower). The proposed hybrid system can guarantee the ۲۴/۷ load supply without any logistics support.Developing hybrid power system based on the renewable energy sources has become more essential considering the shortcomings and the pollution issues of the fossil fuels. One of the main applications of the renewable source hybrid power systems is supplying the off-grid systems such as telecommunication towers. Also, many efforts have been done to develop such power systems in transport industries like electric vehicles.Solar power is considered as one of the main renewable energy source for which various hybrid power system structures have been designed and implemented. The solar panel/battery hybrid power systems are the most common structures usually including solar panels, different kinds of batteries with different gravimetric energy densities, power electronics interfaces and loads.Considering the growing use of the hydrogen energy, the fuel cell/solar panel/battery hybrid power system is a promising solution to supply the off-grid electric loads [۱]. Thanks to the high energy capacity and long-term storage capability of hydrogen, applying hybrid power system based on fuel cell, enhances the load supply duration in off-grid power system. In this paper a conceptual design for hybrid power system based on solar panel and PEM fuel cell with electrolyzer unit is done. Such power systems are recently developed for telecommunication stations [۲] considering their low availability and consequently the importance of energy storage capacity.The fuel cell/solar panel/battery hybrid power system model is presented in figure ۱. In this system, during the periods with sufficient solar power, the load is supplied and the extra power is used to charge the battery bank. When the battery bank is fully charged, the extra power is consumed by the electrolyzer unit to produce and store hydrogen. Note that the electrolyzer water should be supplied primarily. During the periods with insufficient solar power, the load is supplied by the battery bank. When the battery state of charge level reaches to its minimum value, the load is supplied by the PEM fuel cell and the electrolyzer tank is charged by the fuel cell produced water. Again at the periods with sufficient solar power and depending on the load profile, the battery is charged and then the electrolyzer unit is supplied to produce and store hydrogen to supply the fuel cell during the periods with insufficient solar and battery powers. This cyclic operations run to supply the load in the ۲۴/۷ manner with high reliability. Figure ۱: The fuel cell/solar panel/battery hybrid power systemThe load supply strategy in the fuel cell/solar panel/battery hybrid power system is shown in figure ۲. Thealgorithm is based on the design procedure introduced in [۳] with some modifications Figure ۱: The fuel cell/solar panel/battery hybrid power systemThe load supply strategy in the fuel cell/solar panel/battery hybrid power system is shown in figure ۲. Thealgorithm is based on the design procedure introduced in [۳] with some modifications Considering the design procedure presented in figure ۲, in the off-grid applications in the northern andwestern regions of Iran, the load can be supplied in the ۲۴/۷ manner; while in the conventional solarpanel/battery power systems, the continuous load supply in the mentioned regions of Iran is a seriouschallenge considering the insufficient solar power during long periods in days

کلیدواژه ها:

Fuel cell ، Solar Power ، Hydrogen ، Electrolyzer ، Battery