Review Article Review of travelling-wave thermoacoustic electric-generator technology Carmen Iniesta 1 , Jose ´ Luis Olazagoitia 1 , Jordi Vinolas 1 and Javier Aranceta 2 Abstract The proliferation of environmentally friendly electricity-generating technologies has fostered a growing interest in travelling-wave thermoacoustic electric-generator technology and its potential applications. Although reviews exist that focus generally on Stirling engines and thermoacoustic engines, no specific and complete review has addressed the generation of electrical energy through a thermoacoustic Stirling-like cycle engine (TA-SLiCE), which has undergone extensive development in recent years. The present review covers this gap and focuses on the analysis of electric power generation through the TA-SLiCE over different temperature ranges. Therefore, in this review, the general status of travelling-wave thermoacoustic energy generation and the evaluation of the TA-SLiCE types that represent current travelling-wave thermoacoustic generator technologies are presented. In addition, the agents involved in the develop- ment of this technology are reviewed, and selected examples of prototypes and promising products currently in a research and testing phase using this technology are presented. In closing the difficulties in this field, the novelties and current research are presented concluding with the main ideas and recommendations. Keywords Stirling-like cycle engine, thermoacoustic electric generation, technological prototypes, acoustic travelling-wave, electro- acoustic transducers Date received: 25 April 2017; accepted: 25 January 2018 Introduction The global energy issue involves challenges related to the delivery of sustainable, secure and competitive energy. These inter-related challenges are multifaceted and require a coordinated response to accelerate the development and deployment of cost-effective low-carbon technologies. Thus, producing electricity by means of eco-innovations is an essential field of ongoing investigation. Thermoacoustics is a field of growing interest and activity due to its potential for reducing noxious gas emissions, for contributing to the responsible use of energy and for the effective management of clean sources of energy and of waste- heat 1 used as an external power supply. Since its first proposal in 1979 by Ceperley, the thermoacoustic travelling-wave engine has undergone nearly 40 years of development. 2 Ceperley observed that the flow paths of the working fluid molecules followed a sequence similar to that of the Stirling cycle. 3 The thermoacoustic Stirling-like cycle engine (TA-SLiCE), based on travelling-wave phasing, has become the latest evolution in conventional Stirling engines, dramatically simplifying their mechanics since the TA-SLiCE lacks pistons. The following are some of the notable benefits to using travelling-wave thermoacoustic generator technology: 1. No mechanical moving parts in the thermo- dynamic process, thereby greatly reducing the cost of repairs and maintenance. 2. Simple construction using ordinary materials, thus reducing the initial capital expenditure. 3. Great freedom of implementation, thus facilitating distributive energy-generation arrangements. 4. Wide temperature range and feasibility of using different heat sources. 5. Scalable from watts to kilowatts. 1 Department of Industrial and Automotive Engineering, Nebrija University, Madrid, Spain 2 CS Centro Stirling, S. Coop., Aretxabaleta-Guipu ´zcoa, Spain Corresponding author: Jose ´ Luis Olazagoitia, Nebrija University, Pirineos 55, Madrid 28040, Spain. Email: jolazago@nebrija.es Proc IMechE Part A: J Power and Energy 0(0) 1–18 ! IMechE 2018 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0957650918760627 journals.sagepub.com/home/pia