A power plant (1) that includes at least one of a gas turbine (GT), a steam turbine (ST) with a water-steam cycle, and a heat recovery steam generator (B) operatively connected to a heat generating member such as solar energy system (Ssolar) by means of a primary circuit (10a, 10b, 10c) and a secondary circuit system (20a). The primary heat transfer circuit (10a, 10b) includes solar heating system (Ssolar) configured to heat a primary fluid (10), and the secondary circuit (20a) comprises a flow line (20A) for a secondary flow (20) and a main heat exchanger (23) to exchange heat between the secondary water flow and a gas turbine inlet air flow (2). A first line (10B) in the primary circuit (10b) leads to a first heat exchanger (12) to heat the water flow in the secondary circuit (20a).