PhD Thesis - Energy Systems Research Unit - University of Strathclyde

trigeneration system performance is that, the equation does not discriminate betweenthe different exergetic values of the energy products (thermal and electrical)produced by the unit [9, 11]. A more adequate method of comparison is to calculatethe system’s primary energy savings (PES) due to the system. This relies oncomparing the primary energy consumption of the micro-trigeneration system andthe primary energy consumption required to produce the same quantity and quality ofproducts using separate generation. Equation (4.11) shows how the primary energyrequired to produce the same quantities of energy products assuming separategeneration, PE SEPARATE in kWh, was calculated.- (4.11)In this research, to simulate the separate production of energy commodities, it wasassumed that in separate generation of energy commodities, the:DHW supply was supplied by an electric water heater having an electricalefficiency (including stand-by-losses), ƞ Water , of 85% [12];Space heating was supplied by an LPG heating system having an efficiency(including losses due to ancillaries), ƞ Gas Heater , of 85% [13]; andSpace cooling was supplied by a vapour compression chiller with aCoefficient of Performance (COP) of 3 [13, 14].The grid electrical efficiency based on actual electricity delivered (considering theactual energy going into the thermal stations in Malta and the actual electricitydelivered at end-use), ƞ Grid, was calculated as 25.5% [15].Once both PE μTRIGEN and PE SEPARATE are known, the performance of the microtrigenerationsystem can be assessed in terms of the PES of the system, calculatedusing equation (4.12), the official method defined in Directive 2004/8/EC to assess151