By Elliot Gulliver-Needham Renewables Infrastructure Group’s net asset value (NAV) has declined four per cent since the start of the year as low power prices and weak energy generation have hit the investment trust. The £2.5bn trust was launched in 2013 to invest in renewable energy generation and supporting infrastructure. In its interim results today, it revealed that generation over the six months had been below budget, thanks in part to two cable outages at UK offshore wind farms, one of which has been repaired. Remedial works have been scheduled for the second site. Despite the challenges…