Sustainability estimation of energy system options that use gas and renewable resources for domestic hot water production Marina Jovanovic * , Valentina Turanjanin, Vukman Bakic, Milada Pezo, Biljana Vucicevic Laboratory for Thermal Engineering and Energy, VINCA Institute of Nuclear Sciences,11001 Belgrade, Serbia article info Article history: Received 31 July 2009 Received in revised form 25 August 2010 Accepted 27 August 2010 Available online 27 September 2010 Keywords: Renewable resources Sustainability estimation Energy indicators abstract Two possible substitutions for fossil fuel used in heat production are biomass and solar energy. This paper presents an evaluation of various energy sources for hot water production in a heating plant. The heating plant was situated in one of the largest municipalities in the city of Belgrade, Serbia. It produces and delivers domestic hot water and energy for heating to approximately 17,000 households. It is possible to use of using renewable energy instead of fossil fuel for producing the thermal energy for the supply of domestic hot water. Hence, in this paper, an evaluation of the sustainability of different energy options for obtaining thermal energy was considered: 1) from gas combustion; 2) from gas combustion and solar collection 3) from biomass combustion 4) from gas and biomass combustion, and 5) from gas and biomass combustion and solar collection. To compare the different energy systems, the method of multi-criteria analysis was utilised. This method integrates various multi-dimensional criteria and provides an efficient method of estimating the sustainability of complex systems. The obtained results were compared by the General Index of Sustainability which is a measure of the complexity of a system. A basic set of energy indicators that relate to different aspects of sustainable development was defined. In this way, the results in the assessment of sustainability of energy options do not depend on the various analysts in decision making. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction According to the available data (in 2007), the total annual energy consumption worldwide exceeds 131e138 PWh or 473e500 EJ. Of this total amount, oil generates 35%, natural gas generates 20.7%, nuclear generates 6.3%, hydro energy generates 2.2%, biomass and residue generates 10%, coal generates 25.3% and other sources provide the remaining 0.5% [1]. The increased use of fossil fuels has led to air pollution problems, climate change and a constant growth in oil and gas prices on the world market. This has resulted in a worldwide expansion in the usage of renewable energy sources. The utilisation of renewable energy sources such as water, wind, sun, waves, biomass, and others is rapidly replacing the conventional methods of energy production by fossil fuels [2]. The scope and structure of Serbian energy resources are highly unfavourable. The reserves of high quality energy-generating products, such as oil and gas, are symbolic and represent less than 1% of the total energy reserves in Serbia and, the remaining 99% were comprised of various types of coal, with low-quality lignite amounting to 92% of the total reserves. The energy potential of the renewable energy resources in Serbia is important, and it amounts to over 3 Mtoe per year (with the potential of small hydro power plants being approximately 0.4 Mtoe). Approximately 80% of the total potential lies in biomass, to which biomass from wood sources contributes 1.0 Mtoe (wood cutting and wooden biomass residue during its primary and/or industrial processing), and over 1.5 Mtoe arises from agricultural biomass (agricultural and field crops residues including liquid manure). The energy potential of the existing geothermal resources in Serbia amounts to nearly 0.2 Mtoe [3]. The Renewable Energy Resources category in the Strategy of Energy Development of Serbia until 2015 includes biomass, the hydro-potential of small water streams (with structures up to 10 MW), geothermal and wind and solar radiation energy. It should be emphasised that special benefits and requirements exist for the organised usage of these renewable sources in decentralised heat production (by biomass combustion and solar radiation “collec- tion”) and electrical energy production (by construction of small hydro power plants with power potential up to 10 MW and wind generators with power potential up to 1 MW) to satisfy the requirements of local consumers [3]. * Corresponding author. Tel.: þ381 112458222; fax: þ381 112453670. E-mail address: marinaj@vinca.rs (M. Jovanovic). 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.2010.08.042 Energy 36 (2011) 2169e2175