The future pervasive systems will be focused on distributed heterogeneous systems designed with increased autonomy and operating under high uncertainty. In this context, self-adaptive computing can provide an efficient and disruptive response to the design of such ubiquitous systems by providing dynamicity, efficient use of system resources and support for live maintenance, extensibility and evolving requirements. In AETHER+ project different security approaches presented in the scientific literature have been extended by proposing a new design methodology and algorithms for supporting self-adaptive selection of the most suitable security solutions based on available system resources. In particular, a comprehensive model of system supporting self-adaptive security has been introduced. Moreover, two adaptation mechanisms, as implementation of such a model in the context of Wireless Sensor Network (WSN), have been implemented. Proposed approaches can be used to enhance the design of future nodes aimed at increasing their lifetime by selecting the best security solutions according to nodes energy conditions. Effectiveness of proposed solution has been evaluated by means of both simulations and experiments on a real hardware prototype.