PV-Fuel Cell vs. PV- Diesel Generator Hybrid Power System: A Comparative Study

Hybrid power systems are considered efficient and reliable energy solutions to overcome the intermittent nature of renewable energy sources (RES) [۱]. In these systems, hydrogen plays the role of power storage to surmount the intermittency of RES and also during the times of low or no output power [۲]. In this paper, a hydrogen based hybrid renewable energy system (a PV-Fuel cell HPS) and a PV-diesel generator HPS are simulated and optimized based on the minimum net present cost criterion using Homer Pro software. A comparative evaluation for these two hybrid systems is conducted for off-grid applications based on their technical, economic and environmental performance. The schematic diagram for each hybrid system in Homer software is showed in figure ۱. In the PV-diesel generator system, the diesel generator provides the required power during low or no energy output from PV. In PV-Fuel cell HPS, the hydrogen is produced from the electrolysis of water and the electrolyzer uses excess output energy from PV to produce hydrogen. The hydrogen will be stored in the hydrogen tank and will be used as fuel by a series of PEM fuel cells to produce electricity and is considered a backup power source when the system fails to meet the required energy demand. The following reactions represents the electrolysis [۳]:This study evaluated and compared two different optimal configurations of hybrid power systems. The results of the simulation and analysis showed that the net present cost for the optimal PV-Diesel generator hybrid configuration is about half of PV-FC HPS. The levelized cost of energy for PV-generator and PV-FC are about ۰.۲۵$ and ۰.۵۳$ respectively. However the environmental benefits of utilizing PV-FC is significantly higher and will lead to a reduction of about ۸۰ Kg of CO۲ per year while the PV-generator has an emission level of about ۲۹۵ ton of CO۲ per year as well as higher levels of emission for other pollutants. The LCOE for PV-FC is higher than feed-in-tariffs in Iran which makes is less economically viable for on-grid applications. Hydrogen-based hybrid systems are capable of producing power in a sustainable and environmentally-friendly way and are considered a solution to the intermittent nature of output power from renewable energy sources. A policy implication from this analysis is that an increase in the feed-in-tariffs will lead to the improvement in the cost efficiency of hybrid renewable energy systems and as a result will increase the economic attractiveness of these systems and will give the hydrogen-based hybrid power systems an economic competitive edge against the hybrid systems that use fossil fuel based technologies as backup power supply.

Keywords:

Hydrogen-based HPS , Fuel Cell , Simulation , Fossil Fuels , Renewable Energy , Intermittency