zone 107 b may be established such that the output power and the heat dissipated from housing 107 equals the input power cold zone 107 b may be cooled and maintained at a pre determined temperature by fluid e g air such fluid may flow in channels provided in walls of housing 107 b or by other means known to those skilled in the art efficiency for the heat transfer may be enhanced by pressurizing the hot and cold zones alternatively rather than using air other gases may also be used the operating temperature difference between hot zone 107 a and cold zone 107 b either by the cooling method discussed above by controlling the output power or both the output power can be controlled by increasing or decreasing the magnetic field coupling between magnet 108 and coils 109 by motor 110 driving coils 109 up or down a temperature sensor not shown sensitive to the temperature difference between hot zone 107 a and cold zone 107 b may be provided to sense the operating temperature difference fig5 shows control circuit 501 capable of controlling the output power based on the operating temperature difference the control scheme may be implemented using digital or analog techniques as known to those skilled in the art as shown in fig5 a signal v representing the operating temperature difference is received from the temperature sensor and provided to control circuit 501 based on the value of signal v output control signal w drives step motor 110 up or down to vary the magnetic coupling between magnet 108 and coils 109 as appropriate for generating ac electrical.