Fuel cell fuel cells so efficiencies vary, but most are between 40% and 60% energy efficient. However, when the fuel cell's waste heat is used to heat a building in a cogeneration system this efficiency can increase to 85%. This is significantly more efficient than traditional coal power plants, which are only about one third energy efficient. Assuming production at scale, fuel cells could save 20–40% on energy costs when used in cogeneration systems. Fuel cells are also much cleaner than traditional power generation; a fuel cell power plant using natural gas as a hydrogen source would create less than one ounce
Interlanguage fossilization advance gradually until it becomes equivalent, or nearly equivalent, to the target language. However, during the second language learning process, an interlanguage may reach one or more temporary restricting phases when its development appears to be detained. A permanent cessation of progress toward the target language has been referred to as fossilization. This linguistic phenomenon, interlanguage fossilization, can occur despite all reasonable attempts at learning. Fossilization includes those items, rules, and sub-systems that second language learners tend to retain in their interlanguage, that is, all those aspects of interlanguage that become entrenched and permanent, and that the majority of second