11 May 2009


Intelligent automotive air conditioning yields fuel savings

11 May 2009 | The Sentience project, which aims to demonstrate the significant advantages of extending the electronic automotive horizon through the integration of automotive systems, mobile telecoms and advanced mapping technology, today announced the results of extensive climatic testing of an intelligent air conditioning control system. Under conditions representative of UK summer weather, the new system consistently delivers fuel savings in excess of 9 per cent over the urban portion of the NEDC drive cycle.

Sentience is a research collaboration led by Ricardo, and also involves Jaguar-Land Rover, TRL, Ordnance Survey and Orange Business Services, with part-funding provided by innovITS, the UK centre of excellence for intelligent transport systems and sustainable mobility.

The project team unveiled the Sentience research vehicle (based on a Ford Escape Hybrid) at a press launch in early March 2009. At that time the vehicle exhibited the Enhanced Acceleration/Deceleration (EAD) control strategy, in which the vehicle speed is controlled to meet actual and virtual speed limits using an advanced form of adaptive cruise control linked to the hybrid powertrain system of the vehicle. Virtual speed limits are calculated using GPS and mapping data including features such as bends and even speed bumps, as well as less predictable road features including roundabouts and traffic lights. Once EAD is operating, the driver simply steers the vehicle but can at any time, of course, manually over-ride the system if a change of route is required or for safety reasons.

Since its initial unveiling, testing and development of the Sentience vehicle has been actively progressed using climatically controlled test facilities at the Ricardo Midlands Technical Centre. A new Enhanced Air Conditioning (EAC) control strategy has now been successfully developed which manages the air conditioning system in parallel with the hybrid powertrain. This is particularly useful in urban traffic with frequent stop/start transitions. In the test vehicle, the air conditioning compressor is driven by the engine so that when the hybrid powertrain operates in electric only mode or the vehicle is stationary, the air conditioning system does not operate.

By linking the EAC and powertrain control strategies however, knowledge of when the combustion engine may be stopped allows the system to plan an appropriate and more efficient cooling strategy. Cabin air temperature can thus be maintained within a narrow range while maximising the opportunities for the gasoline engine to switch off – and hence minimising the time that the engine is run solely to drive the air conditioning.

The measured fuel saving in summer driving of in excess of 9 per cent is entirely due to the optimised control of the air conditioning system, as this is completely independent of the vehicle's EAD strategy, which could not be used for a defined regulatory drive cycle such as the NEDC. The subject of a Ricardo patent application, the new EAC technology is also highly applicable to all types of hybrid vehicles, including the stop-start systems which are becoming increasingly common.

Tom Robinson, Sentience project director for Ricardo, said: "The Enhanced Air Conditioning (EAC) control system we have announced today is a further very tangible technology breakthrough for the Sentience project, which has already demonstrated the potential synergies to be realised by connecting the existing on-board systems of vehicles with mobile communications and advanced mapping technologies. EAC is highly applicable to a wide range of hybrid vehicle types from simple stop-start systems to plug-in hybrids, and Ricardo will seek to exploit this technology actively in its future client programmes".

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