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 does motivation to achieve native-like competence diminish? The concept of fossilization in SLA research is so intrinsically related to interlanguage that Selinker considers it to be a fundamental phenomenon of all SLA and not just to adult learners. Fossilization has received such wide recognition that it has been entered in the "Random House Dictionary of the English Language" (1987). Selinker's concept of fossilization is similar to that of Nemser, Tarone, and Sridhar, all of whom attempted to explore the causes of fossilization in second language learners' interlanguage. Fossilization has attracted considerable interest among researchers and has engendered significant differences of