Assessing the contribution of energy saving technologies: the case study of variable speed drive air compressors

After the adoption of the 2006/32/EC Directive on energy end-use efficiency and energy services, the monitoring and evaluation of energy efficiency measures and actions have become a very urgent matter, but still the effectiveness of using top-down versus bottom-up approach is a hot topic for the experts. This paper aims at contributing in favour of the role of bottom-up methodologies of energy savings, bringing to the front the case of one specific technology: use of variable speed drives for air compressors, compared to fixed speed motors, with a load-unload technique. A simplified procedure for evaluating and monitoring the effects of such technological replacement is reported, potentials and drawbacks of a simplified assessment procedure are analyzed and, in terms of a case study, projections of potential savings in the Italian industry (i.e. the mechanical sector, equivalent to the NAICS 3335 sector) are proposed as a way of harmonizing top-down and bottom-up approaches.