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.
1. Douro Valley. The Douro valley straddles the Douro river in inland Portugal and is one of the principal wine-producing regions of the country. The Douro valley is most known for the production of port wine. Portugal's world famous sweet fortified wine starts its life here before being transported down to the city of Porto.