Techno-economical study of the use of Itaipu dam spilled turbinable energy to produce ammonia

Abstract

In many hydroelectric dams, when the inflows are greater than the demand for energy, a portion of the water that could be used to generate electricity is diverted to the spillway and literally wasted. This energy,<br />designated as “spilled turbinable energy", could be used advantageously to generate other products or an energy vector that could be stored for later use, since in these situations the dam is full. This work studies<br />the feasibility of using the spilled turbinable energy from Itaipu dam to produce electrolytic hydrogen that, together with the nitrogen from air, is an important feedstock for ammonia synthesis, used to produce<br />nitrogen fertilizers. The minimum electrolytic hydrogen production cost was estimated in US$ 0,25/m3 or US$ 2,75/kg, for a plant capacity of 55 x 103 m3/h, which corresponds to 247,5 MW of electrical power deriving from 82% of spilled turbinable energy and 18% of guaranteed energy. Next to the electrolytic hydrogen plant it is possible to install an ammonia plant of approximately 500 t/day, operating 350 days/year, with a production cost of approximately US$ 562, 81/t. This capacity is enough to<br />supply 38,5% of the ammonia demand estimated for the region focused in the project, that is, 1300 t/day.Nowadays, ammonia is commercialized in the Brazilian market by approximately US$ 525, 60/t. For this reason, it can be concluded that ammonia production via the association of spilled turbinable energy and guaranteed energy next to Itaipu dam is not economically feasible by the moment due to the high cost of<br />imported electrolysers. Nevertheless, with the installation of an ammonia plant based on water electrolysis next to Itaipu dam and considering methane and carbon dioxide emissions of the Itaipu reservoir, an<br />annual carbon emission of 234 x 103 tons could be avoided. If the project is approved by the Clean Development Mechanism, that environmental impact decrease would represent approximately US$ 5, 5 million.<br />Considering that revenu.