In this type of a fuel cell, a ceramic membrane is used as an electrolyte, and there is no need for expensive catalysts. These cells operate at high temperatures (around 800-1000°C), and their efficiency can be increased by using the reaction products in a expansion turbine. Gas from the steam reforming of fossil fuels and biogas, natural gas, or biogas can be used as fuel, and air is used as an oxidizing agent. This type of fuel cell found applications in cogeneration units and power plants.