Energy Efficiency of Existing Buildings: Optimization of Building Cooling, Heating and Power (BCHP) Systems

The enhancement of the energy efficiency of existing buildings represents an important task, specifically addressed by the European Directives. Among the currently available technologies to achieve this issue, the combined generation of heat and power (CHP) is found. Its higher efficiency with respect to the separate production of heat and power mainly depends on the occurrence of a profitable use of the cogenerated heat. This technology is now rapidly spreading because of its benefit from both the energy and the environmental sustainability points of view. However, in order to properly size the CHP system capacity and operation strategy, some specific design rules have to be identified. In particular, the CHP systems optimal design requires the building energy loads to be known on a hourly time scale. In the present paper a simplified procedure for estimating the hourly energy load for space heating and cooling of existing buildings is applied to the assessment of building cooling, heating and power systems energy performance. The results, obtained for a complex nine storey building located in six representative climates, point out that the suggested method allows to estimate the primary energy savings index with an approximation error, averaged over the considered combined generation system capacity range, less than 2.8% and 3.3% in continuous and time scheduled plant operation, respectively.