Investec has kept its positive stance on the temporary power rental market and says that the investment case remains "compelling".The broker quotes the International Energy Agency as saying: "In a world full of uncertainty, one thing is for sure: rising incomes and population will push energy needs higher".Investec added that the supply of electricity is "critical to maintaining robust economic growth, especially in developing economies."A buy rating and 2,250p target price are retained for FTSE 100 temporary power and temperature control provider Aggreko. Meanwhile, the broker initiates coverage of sector peer APR Energy with a buy rating and 1,230p target."Both Aggreko and APR Energy stand to benefit from insufficient permanent generating capacity, especially as finance for new plants is harder to obtain," the broker said. "A strong structural growth story, in our view."BC