Alternative energy products developer Flowgroup said on Tuesday it made significant operational and financial progress in 2015 and expects interim results to be in line with analyst forecasts.The group said its flow energy division grew "steadily through the year as planned", generating revenues of £33m and gaining 66,000 new customers since its launch.Its flow boilers, launched in January 2015, are currently being manufactured in Livigston, Scotland. It also announced it has expanded its manufacturing deal with Jabil, where it agreed to produce 500,000 boilers instead of 390,000.Chief executive Tony Stiff said: "Flow boilers are being manufactured, now, in the UK, and we have a clear strategy and initial agreements in place for international expansion based on the group's patented technology platform."We also believe that the UK market may present opportunities for significant growth for Flow Energy with regard to home energy supply alone. This makes 2015 another important year for Flowgroup and its investors."Investec analysts maintained their 'buy' recommendation and 90p target price as "the investment case continues to de-risk", they said.Shares in Flowgroup fell 5.08% to 29.9p on Tuesday at 12:16.