India-focused sustainable energy firm Mytrah Energy saw profits more than double in 2013, helped by a better-than-expected performance by its portfolio of wind farms.The company, which sells power mainly to state grids, said revenue totalled $50.92m last year, up 65% on the year before which was a nine-month period due to a change in the year-end date.Results were helped by a 71% jump in units generated during the year due to increases in operational capacity and plant load factors (PLFs)."Our operational portfolio, which post year end has risen from 309.9 megawatts to 459.75 megawatts, has performed slightly ahead of our expectations with an average PLF of 25.5% at the portfolio level," said Chairman and Chief Executive Ravi Kailas.Profit before tax (PBT) rose 107% to $10.7m in 2013. In rupee terms, revenue would have increased by 77% and PBT would have been 122% higher. Kailas explained that by Mytrah holding project and turbine costs generally constant, it is able to capture the "positive momentum" provided by rising tariffs in India. This benefitted the gross profit margin last year which rose from 82.8% to 83.8%."In addition, the fall in the rupee during 2013, although now seemingly stabilised, will undoubtedly put further upward pressure on the electricity price as the cost of production from coal increases due to higher import costs," he said. The stock was down 1.7% at 89p in early trading on Monday, pulling back after a 15% fall year-to-date.BC