ELECTRICITY GENERATION DURING PEAK HOURS IN ASUNCION, PARAGUAY THROUGH ANAEROBIC DIGESTION OF CULTIVATED WATER HYACINTH

The objective of the present paper is to present an innovative and sustainable proposal to generate electricity in the metropolitan area of Asuncion, the capital of Paraguay, based on a renewable source of energy. Generation would take place mainly during peak hours with the aim to reduce the contracted power by ANDE (National Electricity Administration) from the existing hydroelectric power plants and so to reduce costs and at the same time to stabilize the transmission and distribution grids in the area of  Asuncion. Electricity would be generated in a combined cycle thermal powerplant of 130 MW using as fuel biogas, which would be obtained by anaerobic digestion of water hyacinth cultivated in pools, which would be built on the bank of the Paraguay river opposit the Botanic Garden of Asuncion. The main advantage to use water hyacinth is its high growing rate, which is between 100 and 500 g/day/m² depending on the environ-mental conditions, what allows to double the plant mass each 6 to 15 days. Additionally, the relation between carbon and nitrogen in the vegetal mass of water hyacinth is optimum for biogas generation. With about 6.4 kWh/m³ the calorific value of biogas is high enough to be used for heat generation and therefore also for electricity generation in a thermal powerplant. This powerplant could be connected directly to the national grid through the transformer station of Puerto Botanic building a 2 km long 220 kV transmission line crossing the Paraguay river. With this project ANDE could save each year up to 25 million US$ due to the reduction of contracted power at the Itaipu powerplant. Although this reduction will decline 3% each year due to the increase of electricity demand, the investment of about 98 million US$ could be payed back in 15 years and would have an IRR of 5% and a NPV of 40,5 millon US$.