One of the major stumbling blocks for the proliferation of hydrogen fuel cells is that lack of infrastructure for refueling them. However, Toyota is now experimenting with a hybrid method that might solve the problem by using natural gas as the base fuel and incorporating a micro hybrid gas turbine into the system.
The structure for making this electricity generation possible is rather complex. The process starts by converting natural gas into carbon monoxide (CO) and hydrogen (H2). A compressor also injects air into the mix, and a chemical reaction through the fuel cell stack creates electricity.
After this step, some H2 and CO remains as waste fuel, and this material goes to the micro gas turbine where a combustion process generates more electricity. As a final step, a co-generation system uses waste heat for producing additional power.
Toyota is conducting trials of the hybrid fuel cell at its Motomachi Plant in Japan, and the company is evaluating the system’s energy efficiency, performance, and durability. The automaker’s photos suggest this system is massive, though. According to the company, it produces 335 horsepower (250 kilowatts), which also doesn’t seem very impressive given the large size.
The automaker believes the hybrid fuel cell has a generating efficiency of 55 percent, and the waste heat co-generation system boosts the figure to 65 percent. For comparison, the United States Department of Energy reports the type of hydrogen fuel cells for transportation generally have generating efficiency between 50 and 60 percent.
In 2016, Nissan showed off its own concept for a hybrid fuel cell, but the company’s solution ran on ethanol. It was also compact enough to fit in an E-NV200 van. A 24-kilowatt-hour battery and 7.9-gallon (30-liter) fuel tank provided an alleged range of 373 miles (600 kilometers). The company planned to further evaluate the experimental drivetrain on Brazilian roads.
Gallery: Toyota Hybrid Fuel Cell
Toyota Starts Trial of a Hybrid Power Generation System Combining Fuel Cell Technology with Micro Gas Turbines at Motomachi Plant
Toyota City, Japan, April 26, 2017―Toyota Motor Corporation has begun trial operations of the pressurized combined power generation system (hereafter, hybrid power generation system) which has been installed at Motomachi Plant in Toyota City, Aichi Prefecture. The hybrid power generation system combines the use of solid oxide fuel cells (SOFC)1 (hereafter, "fuel cells") and micro gas turbines2. The trial operations will utilize the system as an internal power generation facility, with the aim of testing and evaluating the system's energy efficiency, performance, and durability.
The hybrid power generation system uses hydrogen and carbon monoxide which have been extracted by reforming natural gas, and employs fuel cell technology and micro gas turbine in its two-stage power generation mechanism, with a rated output of 250 kW. In addition, it has a cogeneration system (combined heat and power) that uses the waste heat produced in power generation.
This hybrid system achieves high generating efficiency (55%3) with its two-stage power generation system, and also increases overall efficiency (65%) by using the cogeneration system. For this reason, Toyota has positioned it as an effective technology that would help to realize the goal of achieving a low-carbon society. The electricity and waste heat generated is used within Motomachi Plant.
The newly introduced hybrid power generation system is being implemented as part of the "Technological Demonstration for targeting Mass-production of Pressurized Hybrid Power Generation System Consisting of Cylindrical Solid Oxide Fuel Cell (SOFC) and a Micro Gas Turbine (MGT)"4 of the New Energy and Industrial Technology Development Organization (NEDO). This system was jointly developed by Toyota, Toyota's subsidiary, Toyota Turbine and Systems Inc., as well as Mitsubishi Hitachi Power Systems Ltd.
Toyota will continue to promote the development and introduction of the efficient utilization of hydrogen technology in plants, while continuously monitoring the results of the introduction and demonstration results of this hybrid power generation system. This represents a progress forward in terms of initiatives targeted at reaching zero CO2 emissions in plants, which is one aspect of the Toyota Environmental Challenge 2050 which had been announced in 2015.
1 Solid oxide fuel cells use ion conductive ceramic as an electrolyte, allowing for operating temperatures between 700°C-1,000°C.
Reference Difference between fuel cells
Solid Oxide Fuel Cell - Polymer Electrolyte Fuel Cell
A wide range of uses, from small-scale use (household) to large-scale use (plant power supply)
Suitable for small-scale use (household, vehicle power supply)
High generating efficiency
Platinum is not needed as a catalyst
Low operating temperature
Ease of start-up and shut-down
2 A very small sized gas turbine with a small power output.
3 Equivalent to the amount of electricity remaining after power used in the station (for operation of equipment used in power generation) is subtracted from the amount of power generated.
4 In aiming to put SOFC into practical use for commercial and industrial use, NEDO provided subsidies for R&D and introduction of SOFC.
Overview of the hybrid power generation system
Natural gas (CH4) is reformed within the fuel cell, and hydrogen (H2) and carbon monoxide (CO) are extracted.
Electricity is generated in the fuel cell through a chemical reaction that occurs between the hydrogen and carbon monoxide with the oxygen (O2) that is contained in the compressed air delivered by the micro gas turbine.
Waste fuel that is unused in fueled power generation (H2 and CO) is delivered to the micro gas turbines together with the heat and high pressure exhaust that is produced during power generation.
The waste fuel is burned in the micro gas turbines, and electricity is generated as it rotates.
Waste heat is collected from the exhaust gas produced during the burning process.