Energy and Buildings 49 (2012) 294–299 Contents lists available at SciVerse ScienceDirect Energy and Buildings j our na l ho me p age: www.elsevier.com/locate/enbuild Groundwater heat pump selection for high temperature heating retrofit Dragi Lj. Antonijevi ´ c a,∗ , Dimitrije J. Mani ´ c a , Mirko S. Komatina b , Nedˇ zad R. Rudonja b a Innovation Center of Faculty of Mechanical Engineering, University of Belgrade, Kraljice Marije 16, Belgrade, Serbia b Faculty of Mechanical Engineering, University of Belgrade, Belgrade, Serbia a r t i c l e i n f o Article history: Received 21 January 2012 Accepted 17 February 2012 Keywords: High temperature radiator heating Heat pump Low temperature groundwater Seasonal COP Exergy a b s t r a c t Retrofitting of fossil fuel powered hot water radiator heating systems of the existing buildings by ground- water heat pumps can provide significant energy savings followed by economic and environmental benefits. The paper describes the procedure for selection of optimal low-temperature groundwater heat pump vapor compression cycle based on thermodynamic analysis of applied high temperature heat pump heating system. In comparative energy and exergy analysis observed are six different heating cycles, five of which utilize two-stage refrigerant compression, and one operate as basic one-stage heat pump sys- tem with an auxiliary heater. The systems validation is performed accounting strongly for the boundary conditions of the selected location. © 2012 Elsevier B.V. All rights reserved. 1. Introduction A significant part of total energy consumption in most South- east European countries is used for residential and office buildings heating. The heating system predominantly utilized in urban set- tlements is high temperature water heating, either as connected to district heating network or, frequently, with local fossil fuel pow- ered boilers as a heat source. In the second case the environmental impact of pollutants emissions in densely populated urban areas is especially harmful and therefore the existing buildings with hot water central heating systems should be considered the main target of energy efficiency measures. Utilization of ground source heat pump heating systems, is gain- ing in importance globally. Heat pump heating systems that use groundwater as heat source (open loop systems) have many advan- tages over closed loop systems that extract heat from surrounding soil. In an open loop systems a risk of direct environmental pollution is insignificant since the possible refrigerant leakages are restricted to the heating substation or engine room of the facility, and the heat source temperature deterioration, common by closed loop sys- tems, can be successfully avoided by appropriate water discharge technique [1,2], enabling a long term sustainable exploitation of groundwater resource. Furthermore, the heat extraction in an open loop system is more intense, which contributes to the overall heat pump system efficiency. In newly built residential and office buildings, one stage ground source heat pump systems have been successfully used in various low temperature heating applications. In case of retrofitting of high ∗ Corresponding author. Tel.: +381 63 7270654; fax: +381 11 3370364. E-mail address: dantonijevic@sezampro.rs (D.Lj. Antonijevi ´ c). temperature heating systems in existing buildings one stage sys- tems are generally considered inefficient due to the temperature requirements, and the more complex layouts of vapor compression heat pumps need to be assessed. Nevertheless, for efficient opera- tion and acquiring the maximal energy and cost savings effects of heat pump heating system with ground water as the heat source, a selection of location optimized vapor compression cycle is of pri- mary importance. Shallow groundwater is frequently found and various authors have addressed possibilities of its utilization in heating applica- tions. Milenic et al. [3] suggested the criteria for use of groundwater in systems of geothermal heat pumps. Kara and Yuksel [4] eval- uated use of low temperature geothermal energy by means of water to water heat pump. Wang et al. [5] developed and experi- mentally validated high temperature heat pump using geothermal water for heat recovery and building heating. Hepbasli and Akdemir [6] conducted energy and exergy analysis of ground source heat pump system, and Kodal et al. [7] a performance analysis of a two- stage heat pump. Concerning the comparison of vapor compression cycles used in heat pump heating applications, Bertsch and Groll [8] theoretically and experimentally analyzed three different types of two-stage air source heat pumps in order to find solution for sys- tem performance drop caused by large differences between heat source and heat sink temperatures. Recently, authors have focused on evaluation of the effectiveness of ground source heat pumps for heating and cooling applications in buildings. For example, Hepbasli and Balta [9] have modeled and evaluated performance of a heat pump system utilizing a low temperature geothermal resource, and energy and exergy analysis methods were used to assess the system performance based on the experimental data. Importance of exergy analysis of vapor compression heat pump systems has been stressed by Jan [10] and Akpinar and Hepbasli 0378-7788/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.enbuild.2012.02.028