Maximization of primary energy savings of solar heating and cooling systems by transient simulations and computer design of experiments F. Calise a, * , A. Palombo a , L. Vanoli b a DETEC, University of Naples Federico II, P.le Tecchio 80, 80125 Naples, Italy b DIT, University of Naples ‘‘Parthenope”, Centro Direzionale IS.5, 80143 Naples, Italy article info Article history: Received 20 March 2009 Received in revised form 3 August 2009 Accepted 9 August 2009 Available online 15 September 2009 Keywords: Solar cooling Dynamic simulation Design of experiment abstract In this paper, the simulation of the performance of solar-assisted heating and cooling systems is analyzed. Three different plant layouts are considered: (i) the first one consists of evacuated solar collectors and a single-stage LiBr–H 2 O absorption chiller; here in order to integrate the system in case of insufficient solar radiation, an electric water-cooled chiller is activated; (ii) configuration of the secondly considered sys- tem is similar to the first one, but the absorption chiller and the solar collector area are sized for balancing about 30% of the building cooling load only; (iii) the layout of the thirdly considered system differs from the first one since the auxiliary electric chiller is replaced by a gas-fired heater. Such system configura- tions also include: circulation pumps, storage tanks, feedback controllers, mixers, diverters and on/off hysteresis controllers. All such devices are modelled for maximizing the system energy efficiency. In order to simulate the systems’ performance for dynamic heating/cooling loads, a single-lumped capacitance building is also modelled and implemented in the computer code. A cost model is also developed in order to calculate the systems’ operating and capital costs. All the models and the relative simulations are carried out by TRNSYS. A design of experiment procedure is also included. By such tool the effects of the system operating parameters’ variation on the relative energy efficiency are analyzed. In addition, the set of synthesis/design variables maximizing the system’s energetic performance can be also identified. The annual primary energy saving is chosen as the optimization objective function, whereas collector slope, pump flows, set-point temperatures and tank volume are selected as optimizing system design variables. A case study was developed for an office building located in South Italy. Here, the energetic and the economic analysis for all the three considered system layouts are carried out. The simulations’ results are referred to both the initial and the optimized systems configurations. The highest primary energy saving vs. the reference traditional HVAC system is reached by the first considered system layout. The economic performance of the investigated solar heating/cooling systems is still unsatisfactory. The eco- nomical profitability of the considered solar heating and cooling systems can be improved only by sig- nificant public finding. From this point of view, the best results were achieved by the second above mentioned system configuration. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Nowadays, energy saving and low environmental impact should be the primary targets for the HVAC systems designers and producers. From these points of view, the solar-assisted air conditioning systems show a very promising future. By the devel- opment of such renewable energy source technology, the growth of the primary energy demand for space heating and cooling could be strongly decreased. Such goal could be achieved consid- ering that solar cooling systems are, in general, able to balance the space cooling peak demand, which is typically simultaneous with the maximum daily availability of solar radiation. Con- versely, in such hottest day hours the conventional HVAC sys- tems perform at their minimum energy efficiency. In addition, during the winter season, the thermal energy produced by the solar collectors can be usefully employed to integrate the build- ing space heating system. Many institutions are presently involved in R&D and demon- stration activities on this research field. As an example, in 1998 the International Energy Agency (IEA) started a program (‘‘Solar Heating and Cooling, SHC”) aimed at improving conditions for 0306-2619/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.apenergy.2009.08.033 * Corresponding author. Tel.: +39 0817682304; fax: +39 0812390364. E-mail address: francesco.calise@unina.it (F. Calise). Applied Energy 87 (2010) 524–540 Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy