Energy and Buildings 70 (2014) 106–116 Contents lists available at ScienceDirect Energy and Buildings j ourna l ho me pa g e: www.elsevier.com/locate/enbuild Optimal sizing of a thermoelectric heat pump (THP) for heating energy-efficient buildings Y.W. Kim a,∗ , J. Ramousse a , G. Fraisse a , P. Dalicieux b , P. Baranek c a LOCIE-CNRS UMR 5271, Université de Savoie, Polytech’Annecy-Chambéry, Savoie Technolac, 73376 Le Bourget-du-Lac, France b EDF – R&D ECLEER (European Centre and Laboratories for Energy Efficiency Research), France c EDF – R&D MMC (Département Matériaux et Mécanique des Composants), France a r t i c l e i n f o Article history: Received 5 March 2013 Received in revised form 18 October 2013 Accepted 1 November 2013 Keywords: Thermoelectric heat pump Optimal design Energy-efficiency building Exhaust/supply mechanical ventilation system a b s t r a c t This paper aims to determine the optimal design and operating conditions of an air-to-air thermoelectric heat pump (THP) composed of thermoelectric modules (TEMs) and two heat sinks, coupled to an energy- efficient building. We focus on the optimal number of TEMs and the optimal electrical current for three standard cases. The performance is quantified using two different coefficients of performance (COP) definitions: performance of THP only (COP HP ) and performance of THP coupled to an energy-efficient building (COP u ). These COP are also studied for both instantaneous and seasonal conditions. We show that for each coupling, a range of modules exists, with which the maximum performance of the THP can be approached, by simply adapting the electrical current for each condition. Finally, the seasonal performance COP s HP /COP s u for the French city of Macon is estimated and compared for the three cases considered. The original sizing approach proposed here leads to a slight increase of the COP s HP /COP s u (up to +4%), compared to the classical design based on instantaneous nominal conditions (norm). Moreover, we show that the optimal number of modules can be largely reduced (up to -39% for the cases considered) compare with nominal condition method. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Heat pumps systems are considered as one of the most efficient heating and cooling systems because they use less primary energy and again more efficient combined with renewable energy sources like aerothermal [1] and geothermal energy [2,3]. For these reasons, heat pumps will play a key role in reducing building CO 2 emission, contributing to approach the target of nearly zero energy buildings [1]. A thermoelectric heat pump (THP) is a system that uses an elec- trical current to produce a temperature difference between the two sides of a module. It utilizes the Peltier effect to pump thermal power from the cold side to the hot side [4]. The thermoelectric effect was discovered at the beginning of the 19th century [4]. First, practical applications were initially limited because of the low figure of merit (ZT) of the materials used at this time [5]. Afterward, new thermoelectric materials were discovered, allowing the development of new applications such as electronics, biotechnologies, and instrumentation [6–9]. Over the past decade, thermoelectric heat pump (THP) sys- tems have been developed for application to buildings per many ∗ Corresponding author. Tel.: +33 0479 757 716; fax: +33 0479 758 772. E-mail address: yeweon@gmail.com (Y.W. Kim). authors [10–14]. They proposed the use of thermoelectric modules (TEMs) in active building envelopes. L. Shen et al. (a novel ther- moelectric radiant air-conditioning (TE-RAC) system) as outlined in these studies, many thermoelectric advantages over thermo- dynamic heat pumps (with mechanical vapor compression) are highlighted: THP is not noisy, requires low maintenance due to the absence of moving parts, and is compact and potentially low-cost. However, Riffat and Ma [15] note that these elements are not highly efficient compared to classical heat pumps. According to Rowe [16] the THP is competitive in terms of performance when the temper- ature difference between sources of the TEM is minimized. The efficiency of a thermoelectric system depends not only on the temperature difference between the two sides of the TEM, but also on four other factors: (i) the properties of the thermoelectric materials (defined by the figure of merit ZT) [17,18]; (ii) the thermal resistances of the system R th [19]; (iii) the electrical current supply, which depends on the number of thermoelectric modules [20], and (iv) the number of modules. Many papers have been published on the optimization of the coefficient of performance (COP) of the THP (COP HP ). However, most of them only deal with a part of the ther- moelectric elements [19–21], the influence of the heat sinks [22,23], or the contact thermal resistance [19,24]. Notably, few papers to date have studied optimization regarding the sizing of the thermo- electric modules of a THP coupled with an energy-efficient building [24]. 0378-7788/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.enbuild.2013.11.021