On road experimental tests of hydrogen/natural gas blends on transit buses Antonino Genovese a , Nicola Contrisciani a , Fernando Ortenzi b, *, Vittorio Cazzola c a ENEA e Italian National Agency for New Technologies, Energy and Sustainable Economic Development, Italy b CTL e Centre for Transport and Logistics, Sapienza University of Rome, Italy c ATM e Public Transit Company of Ravenna, Italy article info Article history: Received 10 September 2010 Received in revised form 27 October 2010 Accepted 28 October 2010 Available online 15 December 2010 Keywords: Hydrogen CNG blends Experimental tests Emissions Public transit bus abstract The promise of reducing harmful and CO 2 emissions by focusing on hydrogen-methane blends (HCNG) have recently attracted the interest of vehicle manufacturers and transport operators. Several experiments have been conducted in laboratory facilities to assess the potential of HCNG blends in order to decrease the exhaust emissions. This paper reports the results of experimental tests performed at the ENEA Casaccia Research Center aiming to evaluate the energy and environmental performances of a CNG vehicle when fuelled with a hydrogen-methane blend. Two buses for urban transit service were fuelled with HCNG blends with different percentage of hydrogen (5%, 10%, 15%, 20% and 25% of hydrogen by volume). A 100% methane gas was used as reference to compare the advan- tages and disadvantages that can be derived from the use of HCNG blends. Road tests have been carried out by running fixed tracks, which are representative of urban and suburban driving cycles. Vehicles were powered with a lean burn engine whose setup - based on ignition advance angle, has been tuned for controlling the NO x emissions. CO 2 emissions have been investigated to evaluate the leverage effect based on an increased CO 2 reduction resulting from an increased engine efficiency. ª 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved. 1. Introduction Natural gas (NG) is an energy source that is widely used in many fields: residential, industrial, electricity production and transport as well. The annual consumption of NG is steadily increasing in many countries in Europe and in other extra- European countries. The NG consumption for transport is growing due to its lower level of pollutants emissions and its very low particles emissions that make more attractive this intensive use. In public transport the NG is considered the most promising alternative to diesel fuel because of the high standards of service with no burden on the urban environ- ment. Furthermore the lower carbon content in NG meets the CO 2 emissions reduction requirements in order to decrease the greenhouse gases (GHG) emissions in the atmosphere. Manufacturers were ready to fulfill the expectations of transit companies putting on the market vehicles designed and produced to be fuelled with NG. In NG stoichiometric engine the emissions of NO x are high, consequently vehicles are provided with a catalytic converter for the reduction of NO x emissions acting on NO x, , HC and CO. The reduction of NO x emissions can also be achieved using lean burn engines. In such engines the air-fuel ratio (AFR) is greater than the stoi- chiometric AFR giving air to fuel mixture lean. A value of l (l ¼ actual air-fuel ratio/stoichiometric air-fuel ratio) up to 1.6 provides a lean mixture with a very low production of CO 2 and * Corresponding author. E-mail address: fernando.ortenzi@uniroma1.it (F. Ortenzi). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 36 (2011) 1775 e1783 0360-3199/$ e see front matter ª 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2010.10.092