US-based AES Corp., a major investor in Bulgaria’s energy sector, is planning to start building a USD 850-million, 670mw lignite coal-fired plant in Bulgaria in May 2002.AES would invest USD 225 million of own funds in the AES-3C Maritsa East One joint venture between Bulgaria’s National Electricity Company (NEC) and AES, the venture said in a statement. Bulgarian firms would be awarded contracts worth some USD 92.6 million during the plant’s construction.The plant will be located at the Maritsa East lignite coal mining complex that generates 30% of Bulgaria’s power. It would replace an adjacent old unit under a build-and-operate model and would use only domestic lignite coal.