The paper presents the concept of a high-temperature tubular heat exchanger with a porous internal structure manufactured using metal additive manufacturing for application in concentrating solar collectors. In conventional linear solar absorbers, heat transfer between the outer heated surface and the working fluid, especially low-pressure gases such as air, is limited, which reduces overall system efficiency. Existing solutions are primarily based on internal finning or flow turbulization, which are constrained by manufacturing limitations and restricted geometry. The proposed approach introduces a new class of absorber based on complex porous structures that cannot be achieved using traditional technologies. The concept is enabled by metal 3D printing, allowing the design of advanced internal geometries inspired by lattice structures and nature-based cellular materials, aimed at increasing the heat exchange surface and improving thermal performance. The planned prototypes will be manufactured using aluminium and steel alloys, enabling the assessment of both thermal performance and material suitability for high-temperature applications. The project is currently at an early stage, where the experimental test rig has been adapted and a set of different porous geometries is being designed and manufactured. The planned research includes experimental investigations of heat transfer and flow characteristics, supported by numerical modelling of coupled thermal and fluid processes. In further stages, artificial intelligence-based optimisation methods will be applied to identify optimal internal structures under multi-criteria conditions, such as maximisation of heat transfer and minimisation of pressure losses. The study aims to verify the feasibility and performance potential of additively manufactured porous absorbers and to define a methodology for their design and optimisation in high-temperature solar applications. The expected outcomes include improved heat transfer performance compared to conventional tubular absorbers and the identification of optimal porous geometries for high-temperature solar applications.