Cost-optimal sizing of solar thermal and photovoltaic systems for the heating and cooling needs of a nearly Zero-Energy Building: design methodology and model description

This paper deals with the cost-optimal sizing of solar technologies for thermal and electrical needs of residential or tertiary buildings. We consider a typical nearly Zero-Energy Building, whose requirements of thermal and electrical energy are evaluated on the basis of internal loads and external climate. The building is heated and cooled with radiant panels; a heat pump and a system consisting in solar thermal collectors and a thermal storage provide thermal energy, while PV modules supply electricity. The proposed design procedure finds the best number (i.e. the size) of solar thermal and PV modules to be installed, through a lifetime simulation of building loads and energy system according to proper cost-optimality considerations. The paper is divided in two parts. In this first part, we describe general features and principles of the methodology, together with the physical models of each component of the building-plant system. Then, in the second part, we present a case study implementing the illustrated procedure. Results show the notable benefits of the proposed design approach with respect to traditional ones, in terms of both energy and economic savings. We consider simulation-based technique a promising tool for engineering activity as its results can be used to compare different design alternatives and choose a proper cost-optimal solution according to the specific project, context and goals priority. Besides, the proposed methodology can be successfully applied in the more general framework of Net Zero Energy Buildings (NZEBs) in order to fulfill recent regulatory restrictions and objectives in building energy performances.