Energy efficiency optimization in distribution transformers considering Spanish distribution regulation policy Paola Pezzini a,1 , * , Oriol Gomis-Bellmunt a, b, 1 , 2 , Joan Frau-Valentí c , Antoni Sudrià-Andreu a, b,1 , 2 a Centre d’Innovació en Convertidors Estàtics i Accionaments (CITCEA-UPC), E.T.S. Enginyeria Industrial Barcelona, Universitat Politècnica Catalunya, Diagonal, 647, Pl. 2, 08028 Barcelona, Spain b IREC Catalonia Institute for Energy Research, Josep Pla, B2, Pl. Baixa, 08019 Barcelona, Spain c ENDESA, Carrer Joan Maragall, 16 07006 Palma, Spain article info Article history: Received 16 April 2010 Received in revised form 15 September 2010 Accepted 22 September 2010 Available online 27 October 2010 Keywords: Distribution transformers Energy efficiency Regulation policy abstract In transmission and distribution systems, the high number of installed transformers, a loss source in networks, suggests a good potential for energy savings. This paper presents how the Spanish Distribution regulation policy, Royal Decree 222/2008, affects the overall energy efficiency in distribution trans- formers. The objective of a utility is the maximization of the benefit, and in case of failures, to install a chosen transformer in order to maximize the profit. Here, a novel method to optimize energy efficiency, considering the constraints set by the Spanish Distribution regulation policy, is presented; its aim is to achieve the objectives of the utility when installing new transformers. The overall energy efficiency increase is a clear result that can help in meeting the requirements of European environmental plans, such as the ‘20e20e20’ action plan. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction The Kyoto Protocol [1] can be considered as the first step towards the mitigation of effects due to climate change. In 2007, the European Commission published an initiative to develop an energy policy for the EU, introducing an action plan [2] to achieve three objectives by 2020: 20% reduction of greenhouse gas emissions, 20% share in renewable energy and 20% improvement in energy efficiency. This action plan later became the 2009/28/EC Directive [3] on the promotion of the use of energy from renewable sources, amending and subsequently repealing the Directives 2001/77/EC [4] and 2003/30/EC [5]. So far, literature has shown several opinions about climate poli- cies [6] and their role in reducing the greenhouse gas emissions by means of different technologies [7]. There are also interesting studies, showing how different energy scenarios can meet the requirement of a 20% share in renewable energy in final energy consumption [8] and [9]. This paper focuses on the improvement of energy efficiency in power systems [10], not only from an opera- tional or planning point of view [11]. In electrical transmission and distribution (T&D), transformers are one of the major components of a distribution system, and their losses represent almost 30% of the overall losses in such systems. Considering average values, T&D losses consume between 1% (Luxembourg) and 16% (Estonia) of generated electricity [12]. Such a large span suggests a large improvement potential, as presented in the European Project Solu- tion Guide of SEEDT (Strategies for development and diffusion of Energy Efficient Distribution Transformer) [13] and [14]. A reduction in transformer losses would also represent a reduction in CO 2 , and consequently, an increase in energy savings in T&D systems. In an ideal power system, energy savings could be achieved by replacing all installed transformers with others, presenting a higher efficiency [15]. Transformer technology is already mature enough to offer a wide variety of high efficiency transformers that would increase electrical system efficiency. Advances made in amorphous metal- based transformers can provide a considerable impact on energy efficiency and the reduction of CO 2 emissions [16] and [17]. However, technology alone cannot be the solution for the previously mentioned issues; there should be another driving force to enhance electrical systems efficiency, a clear help in this sense are regulation policies, as presented in [18] and [19]. Policies should be very effective and actually encourage all power system decision makers to carry out the changes needed to ensure the achievement of their objectives. This paper presents a novel method to optimize the energy efficiency of the electricity distribution network, based on the replacement of the transformers installed, according to failure and demand rates, under the constraints of the Spanish Distribution * Corresponding author. E-mail address: paola.pezzini@citcea.upc.edu (P. Pezzini). 1 Tel.: þ34 934054246; fax: þ34 934017433. 2 Tel.: þ34 93 3562615. Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy 0360-5442/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.energy.2010.09.035 Energy 35 (2010) 4685e4690