As time permits I have been running computer simulations of the behavior of an ECAT type of device in order to better understand its operating states. It appears that there are three distinct regions of operation that are encountered which have well defined characteristics. A brief discussion of these modes follows.
1. This mode of operation is when the amount of positive thermal feedback is limited or non existent altogether. A dummy system such as currently being measured by the MFMP team falls into this category at the very low end. In general the temperature of the outer surface as well as the inner core area will rise smoothly as the input power to the device is increased. Radiation, convection, and conduction of heat power away from the core exceeds any internally generated power to such a degree that it is sometimes difficult to determine that any excess power is generated at all. Any operational temperature and its associated input drive power can be reached and stable operation at that point achieved. COP will generally be limited to a modest value for a device that operates within this mode to likely less than 4. The latest independent third party testing indicated that the unit they examined probably operated in this manner. Unfortunately, the scientists did not have an opportunity to carefully adjust the input power and monitor the output power to generate a stable curve with several static operating points to verify the mode. One characteristic of this operating region is that the temperature and thus output power will rapidly rise as the input is slowly increased if the feedback is adjusted to approach operational levels of the next region(2). The data that was presented suggested that this was the situation for that test. Note the very rapid rise in output power that they saw for a modest change in input power. 2. The second mode of operation appears to be the ideal one to utilize if a large COP is desired and it is necessary for the device to cool back to room temperature once input drive power is removed. I consider the region as defined by the presence of a negative resistance region occurring within the operational range of the device. The negative resistance section is limited in scope so that there is no temperature of operation existing at which the internally generated heat power exceeds the power exiting away from the core by radiation, convection, and conduction. This limited negative resistance range ensures that the device will cool down once input drive is removed. One very noticeable characteristic of a device operating within this region is that it is impossible to keep the core temperature constant at any constant fixed drive power level for operation within the negative resistance portion of the device. At any static long term fixed input drive level, the core temperature and output power will vary until operation reaches one of the positive slope regions. You can use a PWM input drive waveform to control the transition through the negative region, but you will not be able to keep it confined in that section without modulation of the input drive power. Very large values of COP are possible for a system that operates in this fashion. Of course, the more positive feedback that is designed into the system, the higher the possible COP. My simulations suggest that achieving a COP of 10 or more would not be too difficult in this mode provided the feedback is accurately controlled and operation approaches the third mode. Also, the ECAT will always cool back to room temperature once the input drive power is removed as would be normally desired. 3. Operation within the third region can truly be considered SSM by anyone's definition. A device of this type has increased positive feedback as compared to one that is confined to the second region(2) discussed above. As in number 2 above a region of negative resistance operation is located within the curve that defines core temperature versus input power. The difference between this mode and that one is that the feedback is increased to such an extent that a latching of temperature and output power occurs even when the input drive power is totally removed. You can drive the device into a state where power is constantly being supplied to the load until some additional control action, such as water flooding, is required to initiate a final cooling down. An interesting characteristic that a device that operates within this region will demonstrate is that as the input power is slowly increased the output power will initially rise smoothly. Once the input reaches the portion of the curve containing the negative resistance region the positive thermal feedback takes over and rapidly drives the core temperature higher as the output power rises. The system should settle at a high output power point that is located within the positive resistance region that falls above the negative one. If input power is then removed the temperature will fall somewhat lower until it reaches the point where the power generated by the core exactly matches the power leaving the device by radiation, convection, and conduction. The temperature should remain stable at this point. When it is desired to shut down the device additional input water, in the case of the warm ECATs, can be pumped into the unit to extract enough additional heat power to force it into cooling. The amount of thermal cooling shock required depends upon the design of the ECAT and can be relatively minor if the negative feedback is restricted to a value near to that needed for operation in the second mode above. The three modes of operation that I have discussed assume that the original problem of thermal runaway has been resolved. The latest statements from Rossi suggest that this is true, but that needs to be verified by much additional testing. If thermal run away remains a problem, then it will be difficult to operate in any mode other than 1 above unless extreme care is taken to ensure that the device does not melt. It should be possible to take any device with a core that generates additional heat power as drive power is applied and modify it so that it operates in one of the modes above. Addition of a sufficient quantity of insulation to prevent heat from escaping the core should result in an increase in the positive feedback factor. I suspect that a good proof that internal power is generated can be established by this relatively simple technique. Of course many devices may exhibit thermal run away and melt when subjected to this abuse, but that result would constitute proof of performance. The demonstration by Dennis Craven indicates that his device is likely operating according to the first number(1) above. The magnitude of the positive thermal feedback is relatively small and it is obvious that operation is confined to a positive resistance region. If he elevates the temperature significantly he may find that the device enters into a negative resistance region, but it appears that substantial insulation will be required if that is going to be seen. Dave
