Ten years history of a real gas driven heat pump plant: Energetic, economic and maintenance issues based on a case study F. Busato, R.M. Lazzarin, M. Noro * Department of Management and Engineering, University of Padova, Stradella S. Nicola 3, 36100 Vicenza, Italy article info Article history: Received 19 October 2010 Accepted 6 February 2011 Available online 12 February 2011 Keywords: Heat pump Gas engine Economic savings Energetic savings Condensing boiler abstract The building named “San Nicola” belongs to the public building stock in the town of Vicenza (IT). It was built in the 15th century and, after a major refurbishment, from 1999 it hosts the Department of Management and Engineering of the University of Padova (Italy). The core of the HVAC system is a gas engine driven heat pump, integrated with condensing boilers. The paper illustrates how, once the initial problems with the control and management strategies were solved, this system led to significant primary energy savings. Upon the offer from the local district heating (DH) provider for connecting the building to the DH network, an assessment was made to compare the existing plant to this solution. The connection to the DH network would have led to an increase in operational costs on one side and in primary energy consumption on the other hand, as described in a previous work by the authors. After about 10 years of operation, while facing the need for some major maintenance both on the mechanical and the control side, the engine half-life is forthcoming. The general service office of the University of Padova, instead of the half-life maintenance, is considering a replacement of the entire generation system with a traditional electric chiller for summer cooling and the uninterrupted use of condensing boilers for winter heating. It is then worthwhile to compare, on the economic side at first and then from the energetic point of view, the present solution and the option for the future. The comparison has been based on the measured consumptions of the past years and the additional cost for extraordinary maintenance not included in the maintenance contract. The analysis proves that the choice of dismantling the actual plant is wrong, even accounting the complete renewal of the actual system with a new one of the same kind. If the loss of productivity - generated by the machine downtime in summertime - is evaluated in terms of an economic loss, the present and the future solutions are quite similar from the economic point of view. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Energy consumed in residential and tertiary sectors for space heating and domestic hot water production is quite the 20% of the total Italian energy need. Since 93/76/EEC Directive on the energetic analysis of buildings and energy performance certification, the 2002/91/EU and the newest 2010/31/EU Directive on the energy performance of buildings (recast), a virtuous process of making responsible building’s owners and HVAC plant’s designers on the huge energy saving potentials on buildings has been started. In Italy, in a number of legislative acts have been issued during the last years but heat pumps as technology to satisfy space heating and domestic hot water production has been not attractive for the market till recent period. This is probably mainly due to unfavourable economic conditions with regard to the electrical tariff (only recently faced by the Italian main electricity distributor with a dedicated tariff) and to the modest technical knowledge of the HVAC designers and installers. Nowadays conditions are more favourable, due to the increase of diffusion of distributed electrical energy production technologies (i.e. by feed-in tariff and net metering) e they are suitable to couple with electrical heat pumps e and to new stan- dards on heat pump test methods and numerical procedures for energetic analysis. At the same time, consumption of natural gas as primary energy source in Italy is increasing during the last years, mainly due to the diffusion of the most modern natural gas-fired combined cycle power plants. As well known, it is quite opportune to increase use * Corresponding author. Tel.: þ39 0444 998704; fax: þ39 0444 998884. E-mail addresses: busato@gest.unipd.it (F. Busato), renato@gest.unipd.it (R.M. Lazzarin), noro@gest.unipd.it (M. Noro). Contents lists available at ScienceDirect Applied Thermal Engineering journal homepage: www.elsevier.com/locate/apthermeng 1359-4311/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.applthermaleng.2011.02.006 Applied Thermal Engineering 31 (2011) 1648e1654