Energy and Environmental Performance of Solar-assisted Desiccant Ventilation Units: a Life-cycle Perspective

When dealing with energy conversion, the most efficient systems usually require a higher energy supply for their production process. As a consequence, it is interesting to investigate whether their extra embodied energy content is balanced by their higher energy efficiency. In this paper such an investigation is focused on the most widespread technologies for air cooling and dehumidification; a comparison is made between conventional systems and systems based on the use of solar-assisted adsorption wheels. Through experimental and literature data concerning materials inventory and energy costs of basic materials, the embodied energy and the environmental impact associated with both the construction and the operation of the systems are determined, according to the Ecoindicator 99 method. This allows defining the overall life-cycle impact of the proposed systems; interesting evaluations will be done based on parameters such as the compensation time, which is defined as the time it takes for a system to save as much energy as the extra embodied energy needed for its production, in comparison with a less efficient reference system; the definition will be obviously extended to the environmental issues. The study is applied to three different climatic conditions, typical of Southern, Central and Northern Italy; the results will also take into account different possible values of the solar fraction F. The study will show the beneficial effects of the use of solar energy on a life-cycle perspective.