Kilowatt-Hour per Unit of Fuel. The energy value of a unit of fuel depends on its mass, carbon and hydrogen content, and the ratio of carbon to hydrogen. In general, hydrogen generates approximately 62,000 BTU per pound and carbon generates around 14,500 BTUs per pound.
Quick Answer. The three largest rivers in Portugal are the Tagus River, the Douro River and the Guadiana River. All three rivers also flow through Spain. The largest river in Portugal is the Tagus River; it is 645 miles long. Continue Reading.
Portugal is right next to Spain (both of these nations are part of what is known as the Iberian Peninsula) at the western end of Europe.