There is a global need for people to have access to enough potable water to meet their daily needs. However, in developing countries water distribution infrastructure is often inadequate to meet demand. Water demand is anticipated to increase as a result of urbanisation, population growth and climate change. The solutions considered must be feasible for those subject to water scarcity. The current work is concerned with development of a solar desalination still to increase water security in developing countries. Design focus has been on the technical and sociocultural factors which are most important for optimising performance and community acceptance of a still. The work has particular focus toward applications in South Pacific nations where electricity supply, available capital and technical expertise are more limited than in more developed countries. The influence of several environmental, design and operational factors on water productivity have been tested as part of the current work. This testing led to the formulation of an equation set defining system dynamics. The equations were based on fundamental heat transfer and thermodynamics principles. Solar still desalination is an active field of research and a range of empirical and semi-empirical equations have been presented in prior literature. The studies offering a thermodynamic basis for the equations are relatively few. No prior work was found to have integrated relative humidity as a system variable within the equation set, although it has been acknowledged that internal humidity in the still is below saturated. The current work addresses relative humidity as a significant system variable for the equation formulation and the models have excellent fit to the data as a result. The key factors of influence were extracted from the empirical and model-building phase and consolidated into a series of design implications for practitioners focussing on solar stills and their design. These implications also considered the socio-cultural dimensions which are critical factors independent of the unit functionality. A framework was formulated which described a general new product design process, tailored specifically for application in developing countries. This framework was then applied to the solar still case, thereby presenting an implementation pathway relevant for practitioners in the field.