Abstract

MAIOLI, A.; PULFER, J.  and  MITJANS, F.. Generating electricity during peak hours in Asuncion, Paraguay, through anaerobic digestion of cultivated water hyacinths. Ing. Investig. [online]. 2011, vol.31, suppl.2, pp.66-70. ISSN 0120-5609.

The objective of the present paper is to present an innovative and sustainable proposal for generating electricity in the metropolitan area of Asuncion, the capital of Paraguay, based on a renewable source of energy. Electricity would mainly be generated during peak hours with the aim of reducing power contracted by the Paraguayan Electricity Administration (ANDE) from existing hydroelectric power plants and thus reduce costs and stabilise transmission and distribution grids in the area of Asuncion. Electricity would be generated at a 130 MW combined cycle thermal power plant using biogas as fuel, this being obtained by anaerobic digestion of water hyacinths cultivated in pools, which would be built on the banks of the Paraguay river opposite Asuncion's botanical garden. The main advantage of using water hyacinths is their high growth rate, this being 100 to 500 g/day/m² depending on environmental conditions, thereby allowing plant mass to double every 6 to 15 days. Additionally, carbon to nitrogen ratio in water hyacinth vegetal mass is optimum for biogas generation. About 6.4 kWh/m³ biogas calorific value is high enough to be used for producing heat and, therefore, for generating electricity in a thermal power plant. Such power plant could be directly connected to the national grid through the Puerto Botanic transformer station by building a 2 km long 220 kV transmission line crossing the Paraguay River. This project could save ANDE up to 25 million US$ every year due to reduced contracted power at the Itaipu power plant. Although this reduction will decline by 3% each year due to increased electricity demand, the investment of around 98 million US$ could be repaid within 15 years and would have 5% IRR and US$ 40.5 million NPV.^.

Keywords : water hyacinth; biogas; renewable energy; electricity generation; peak hour; gas plant; grid stabilization.

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