Need Converter (24 V AC to 12 V DC, approx. load 60 watt) Automobile application

Hello !!
Require Converter (AC to DC) for Automobile application.
Approx. input : 24 V AC (30 V max) generated by petrol engine
Output: 12 V DC suitable, load: 60 watt
(load: solenoid valves)
thanks in advance.
There are plenty of 24vDC to 12vDC converters on the market like Orion:
The tricky bit is the 24vAC supply:

You could fit a 24vDC battery in but would need diodes to rectify the 24vAC
or even build your own converter - this is lighter load but the principle is the same:
The suggested Farnell power supply is only 1A and you need 5A for 60W.

You might consider a step up transformer to 120Vac and then using conventional 120Vac input/12Vdc power supply of which there are dozens of commercial models.