At the Department of Management and Engineering (DTG) of the University of Padova (Italy), the research team led by Prof. Renato Lazzarin, formed by the authors, worked during the first fifteen years of the millennium on different topics focused on innovative heating, ventilation and air conditioning technologies. Both experimental and theoretical/modelling studies were carried out: an air conditioning system with liquid desiccant operating for annual climatization was designed, realized, and tested; a self-regenerating liquid desiccant cooling system based on an electric heat pump was installed and monitored in a new building of the Vicenza Hospital for dehumidification, heating and cooling; a gas engine heat pump plant for the air conditioning of a building of the DTG was designed, realized, and monitored for a long period; a multisource heat pump plant was modelled and dynamically simulated, and then realized and monitored for the climatization of a school building; hybrid water/phase change materials tanks were modelled, designed and tested for thermal energy storage; finally, thermal and electric solar cooling plants were modelled and dynamically simulated for evaluating energy performance. The paper highlights the main theoretical and experimental approaches and the results of the research during the fifteen-year period.