Institute Superior Tecnico, DEM-STE, 1049-001 Lisboa, Portugal

The Sociedade de Transportes Colectivos do Porto (STCP, the main public transport company in the city of Porto, Portugal) has introduced, under the project CUTE – Clean Urban Transport for Europe and together with other 8 European cities, 3 fuel cell transit buses in their fleet, with an hydrogen refuelling infrastructure supplied by BP. The objective of the CUTE project was to demonstrate and develop a locally emission-free and low – noise transport system, including the accompanying energy infrastructure. The hydrogen used in Porto was produced by electrolysis (using grid electricity) in a Linde factory in Alenquer (north of Lisbon). Three different hydrogen production strategies where evaluated: steam reforming of natural gas, water electrolysis using grid electricity (used in the project) and water electrolysis using renewable electricity. Two other fuels/technologies were also evaluated and compared to the hydrogen results: Diesel and natural gas. Two parameters with relevant impact (both environmental and energy) where evaluated: consumption of non-renewable energy as MJ per km and emission of greenhouse gases (GHG) as equivalent kg of C02 per km.

1. Introduction

Under the Kyoto protocol, Portugal was allowed a 27% increase of emissions of GHG (relative to the values of 1990) by 2010. As by 2000, emissions were already 30,4% above 1990 levels. The transport sector is the largest contributor to the global GHG emission, with about 30% of the total national emissions. Within the transport sector, 70% of the emissions result from road transports.

Besides GHG emissions (to which pollutants should be added, although this is beyond the context of this paper), the growth of the road transport induces an ever increase of importation of fossil energy sources, creating a problem of security of supply. Renewables must contribute to a solution.

To address these issues, the European Commission has developed policies with the objective of:

• Better integration of transports, using more environmentally benign and less energy demanding modes of transport;

• Stimulating the development of new technologies;

• Improving road safety.

Within this framework, the project CUTE-Clean Urban Transport for Europe was approved and, with the support of the European Commission, had the objective of introducing hydrogen fuelled vehicles in Europe. This was successfully achieved by the operation of 27 buses in 9 European cities (one of which is Porto). The buses operated for a period of 2 years, the Porto test starting February 2004.