While SHA-2 is a ubiquitous cryptographic hashing primitive, its role in emerging application domains, e.g. blockchains or trusted IoT components, has made the acceleration of SHA-2 very challenging due to new stringent classes of requirements, especially implementation cost and energy efficiency. The survey discusses these emerging applications and their fundamental requirements. Then, the work presents a comprehensive review of the different design techniques available in the literature for SHA-2 acceleration. The main focus of the presentation is placed on the impact of each design technique on the area, energy, power, and performance of the resulting accelerator, guiding the designer through the identification of the appropriate technique mixes which meet the constraints of any given application.