Prototype (Experimental) Serial Hybrid system

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Over recent years there has been a great deal of interest in Hybrids. This technology has the potential to provide reductions in fuel consumption and the electric drive enables quiet, green boating. An experimental system was designed to evaluate Hybrid components and to develop a sophisticated hybrid control system.

An integrated serial hybrid system was develpoed from the ground up. Each component was selected to provide an efficient / low cost drive train. A computer controled generator was designed together with a custom power control system. Multiple renewable resources (solar panels, wind generators etc) can be attached to the system. The energy accumulated over time from these green resources can provide a considerable contribution to a crafts power requirements.

Using patented "Pulse Charging" technology this serial hybrid system is able to efficiently charge the battery bank from a depleted condition, through bulk charging, trickle charging and equalisation. A fully autonomous system is implemented that is able to spend prolonged times at sea. All power requirements can be supplied while keeping the battery bank in optimum condition. With the addition of Solar panels, wind generators, AC mains etc, the control system is able to intelligently select between available resources to minimise use of fossil fuels.

A regenerative option is also available. When an auxiliary craft is under sail the propeller can be allowed to rotate. The Motor then turns into a generator and the batteries can be re-charged. Under fresh wind conditions the extra drag on the craft is minimal and a large amount of electrical energy can be generated. The Control system is able to vary the energy extracted from the propeller and hence adjust the drag incurred. Via a simple control panel a user can set the amount of regeneration required or disable it completely.

A considerable amount of energy can be stored in the battery bank. This can be used for much more than propelling the vessel. Using AC inverter technology a powerful mains circuit can be provided. Microwaves, electric kettles, fan heaters, even an arc welder, can now be using in craft previously thought to be too small for such equipment. This serial hybrid effectively provides the functions of propulsion engine and generator in one compact package.

The generator may be located in any position in the craft allowing very flexible arrangements. When encased in a sound proof cocoon the noise during operation is considerably less than a standard propulsion engine.

Unique technology has been employed in the generator to obtain efficient operation with low fuel consumption. The battery bank is charged with very high energy and the generator only needs to be used for a proportion of vessels operating time. This provides long spells of whisper quiet electric only operation and makes pleasure boating much more pleasant.

A number of operating modes have been implemented to provide a highly flexible system. These modes are automatically selected by the control system depending on prevailing conditions, no user intervention is required. These modes can be summarised as follows:

  • Electric drive only : For shorter passages in calm condition. Recharge can be then effected via solar panel, wind generator or AC mains upon return to the marina/mooring.
  • Hybrid mode : The generator charges the battery bank with high energy then is cycled off. Over a longer period power is supplied from the battery to the electric drive motor. Depending on the sea conditions and vessel speed the generator is only operated for a fraction of the passage. At all times the control system knows the battery's state of charge and the current drain from the motor. This provides the ability to fully charge and condition the battery bank while also driving the vessel.
  • Parallel mode : At times of high demand the generator is able to supply power in parallel with the battery
  • Diesel Electric mode: Under prolonged conditions of moderate to high power demand it can be more efficient to supply energy direct from the generator to the motor (battery isolated from system). The system will automatically enter this mode when conditions dictate.
  • Failsafe mode : No matter how reliable a control system, problems can occur. In a marine environment it is essential to have failsafe operation should the electronics fail. In this mode the battery bank, control system and motor controller are completely disconnected. Power goes straight from the generator to the motor. Vessel speed is then controlled in the conventional way by operating the engine's governor. In this mode of operation the generator & motor transfers power from engine to prop shaft in a similar way to a hydraulic drive (though with much higher efficiency).
  • Generator only : Whether the vessel is at sea, at anchor or on the mooring the generator can still be operated to provide all onboard power requirements. No more running out of batteries on passage. Many DIY projects can be conducted regardless of the location with plenty of power for tools.

System operation

A  simple control panel is provided. All system information can be monitored via the display. Using the key pad the hybrid can be activated and performance parameters set.

 

Display Functions include

  • Operating mode
  • Battery monitor (%Capacity, Voltage, Current)
  • All system drain and charging currents.
  • Instantaneous Fuel consumption
  • Charging efficiency
  • Fuel consumed / fuel left.
  • System alarms with automatic shut down

Control functions

  • Automatic : Systems decides when to run generator depending on battery condition, availability of green resources, and power demand.
  • Green only : Used when vessel is not occupied. Over time a considerable amount of energy can be accumulated in the battery bank.
  • Disabled : For system servicing and set up of operating parameters.

Motor installation

How much power do you need?

Careful attention to detail is required when sizing your system, factors to consider include :

  • Hull drag characteristics
  • Hull windage and performance in heavy weather.
  • Range and speed requirements.
  • On board power needed for DC and AC circuits.

The graph below shows a power model we have developed for a typical 10M auxiliary sailing craft. The bottom line represents smooth water conditions. As can be seen operation at 5kt in smooth water requires little over 1kW delivered to the water. This explains why low powered systems are specified for inland waterway craft. The top curve shows the power required in heavy weather (when travelling at 45° to wind & waves, Force 7, North Sea conditions). This includes drag caused by wave action and windage on the hull / rigging . Here we can see approximately 5 times the power is required to achieve 5kts and shows why larger systems are required for open sea vessels.

There are many losses in the drive chain, for example a typical propeller may only be 50% efficient. All these losses must be factored into the power calculation to determine the sizing of the system. As part of this research program we developed sophisticated software tools to analyse a vessels power requirements

This serial hybrid system completed initial sea trials in the spring of 2007. A summary of results together will a more detailed report can be found on the Downloads page.

After reviewing this site, please take our brief survey        Hybrid Survey