Dave,
Did you consider a negative differential resistance scenario for the input? This would make for nonlinear operation but it is closer to what Rossi is suggesting. It implies a "sweet spot" in the parameters which should be easier to control since there would be both positive and negative feedback. From: David Roberson Subject: [Vo]:Linear Operation of ECAT Modeled I have been toying with a new computer model of the ECAT that I constructed the other day. The concepts that are being presented are based upon a simple model of the ECAT that has many assumptions since Rossi has not released many of the detailed technical information required to construct a truly accurate one. This particular model run assumes that the internally generated heat power follows a forth order function in the region around the thermal run away temperature. It can be adjusted to include any polynomial or other function once that has been verified. The main idea at work is that the ECAT must use positive feedback in order to operate at a reasonable COP. Negative internal feedback or no reinforcing heat from the powder will not work to a useful degree. The model suggests that Rossi must carefully set the thermal resistance into which heat is delivered by the device. If the coolant flow rate is excessive, which would represent someone attempting to extract too much heat from the system, the positive feedback can be defeated and the temperature would collapse. This implies that there must be a tradeoff between the variables which is most likely where a lot of Rossi's time is being expended. I did notice that under the ideal conditions operation slightly below the run away core temperature can be theoretically controlled and the gain large. My model demonstrates this is possible, but the control system is subjected to a positive feedback behavior which it must overwhelm. Operation at these types of location are tricky since any error in temperature of either direction tends to compound and the device heads ever stronger in that direction. If the core experiences a slight increase in temperature it heads toward thermal run away and must be reversed by the control loop. On the other hand a tiny drop in core temperature leads to total cooling unless compensated. The control loop has to contend with environment changes such as input coolant temperature and flow rate, or for example changes to the activity of the powder with time. I am confident that there are many other factors which attempt to influence the instantaneous balance required at the chosen operation temperature and all of these require an excess of control range for proper allowance. The time constants associated with the device must also be contended with and of course these are not being revealed by Rossi at this time either. Any delays built into the heat generation mechanism itself further complicate the control system. For all of these reasons, a model such as the one I have constructed makes assumptions that will likely be found in error, but at least the trends should be revealed. One of the model runs that I conducted assumed that an input power set to a constant 1000 watts(modified by the loop) could control a total output power of 10000 watts for a net COP of 10. Other drives can of course be used which yield higher or lower values of COP, but this value has a nice ring to it! The thermal run away trip point is within 5% of the absolute temperature of operation in this particular case. I have noticed that most any other polynomial relationship between core power generation and temperature work in a similar fashion to the forth order where the higher ordered functions tend to be more critical. This is to be expected. Dave
