Document Type

Conference Paper


Available under a Creative Commons Attribution Non-Commercial Share Alike 4.0 International Licence



Publication Details

Irish Transport Research Network Conference, Trinity College Dulbin, 5-6 September, 2013


Luas is a state of the art light rail system operating in Dublin Ireland. Being electrically powered, energy is a major operating cost for Luas. One component of rolling stock identified by this research that consumes a disproportional amount of energy is that of the heating and ventilation systems. The heating and ventilation systems fitted to Luas vehicles consume as much as 60% of total vehicle power, and under certain conditions can consume more than that of the traction motors. This paper explores solutions to reducing the energy consumption of Luas heating and ventilation systems. The identified software modifications and hardware installations proposed by this research have been estimated to save over 1,400,000 kWh, 7% of total Luas energy consumption. Based on the current average industry price of €0.12 per kWh, this saving equates to almost €170,000 per year.

Transport systems are not immune to the economic downturn seen throughout the Europe Union. With decreasing passenger numbers, operators are faced with reduced revenue streams, which could lead to reduced services or possible job losses. To avoid such action, operators must reduce their operating costs adequately. Heating and ventilation systems provide passengers with a controlled, fresh, temperature-regulated air supply to ensure maximum comfort. Light rail systems are arguably one of the most difficult transport modes in which to regulate air temperature and quality, due to their short trip distances with a high number of stops.

Each Luas vehicle has three heating and ventilation units. The total rated power of the three systems is 60 kW, power is supplied by way of 750 V DC direct from the overhead catenary supply. Each unit is controlled by a self-contained control unit where in all eventualities, the system endeavours to achieve a variable interior set point between 14 °C and 20 °C. The system is set up to automatically start once the vehicle is prepared (switched on) and will remain on (temperature depending) until the vehicle is de-prepped (switched off).

Testing of the system, recorded a maximum consumption of 60 kWh at an operating temperature of 2 °C. Contrastingly a test conducted at 19 °C the consumption was 3 kWh. Detailed analysis of Luas operations indicates that on average 30% of the time Luas trams are in operation, is not actual passenger service. However the heating and ventilation systems are operational during these periods. Automatically disabling the systems during these non-passenger periods would reduce energy consumption significantly, while not adversely affecting passenger comfort.

To achieve this objective, three modifications have been identified. The first two will automatically disable the heating and ventilation system while operating in periods of non-passenger service when the vehicle is in traction and while the vehicle is stable in the shunt (end of line). The third modification will reduce the set point profile, the system endeavours to reach. The paper describes in detail the software modifications and hardware installations required to roll out these modifications across the Luas fleet.