January- the tubing is shaped for the system using new custom made jigs. Standard brass compression fittings are also modified to make connections of the tubing to the copper tubing of the ElectroCrown and new expansion tank. Some tubing connections are also welded together using a hot air welder. The silicone tubing of the peristaltic pump is replaced with opaque fluorosilicone tubing.
February-all the silicone tubing is disconnected and removed from the heat transfer system and replaced with the new tubing. The system is filled using the new HTF however, as testing begins, the fluid is too thick at startup and flows poorly in the system. The HTF is purged from the system and replaced with what we were using before.
March 5-we got some sun today and had our first no fail test ever.About 750mv at 2A. The temperature will be increased over the next few days because we will be insulating the return line to the Solar Heat Collector from where it exits the ElectroCrown. This means that the entire HTF system will be completely insulated, except for the peristaltic pump, and the HTF will probably need to flow faster through the system once it reaches 200C.
March 10-the new insulation for the return line is made and ready to install tomorrow. Let's see some sunshine!
March 11-the insulation is installed and holds the temperature in the system much better. It was not necessary to have full sunlight to test the system's electrical output. The Sun was close to sunset (5:30PM). We have now decided to insulate the entire system including the peristaltic pump soon after testing.
April-Testing of the tubing shows that it can not handle the high temperatures continuously in concentrated sunlight. We will experiment with metal tubing in this area.
May thru June-copper tubing is shaped and installed to replace the PFA tubing at the focal point of the concentrated sunlight. A flat black paint is applied to the surface of the copper.
July-the copper tubing is satisfactory and performs well. Another HTF provided by Dow Chemical is tested and exceeds the performance of the HTF that we have used from Germany. Things are beginning to look much better. We are insulating the entire hot side of the HTF system including the peristaltic pump. Awaiting new high temp parts for the pump.
August-testing of the insulated system was initiated and the fluorosilicone tubing of the peristaltic pump has failed. After 5 years of tinkering with the pump, it was decided to retire the peristaltic system and look for another pump style to work with that can withstand the harsh environment is it used in.
After contacting numerous companies locally and around the world, we discovered that no standard pump is suitable for our system mainly due to the extreme temperature of 200C. we are now designing our own pump that will handle this temperature and it is similar to a solenoid pump.
September-we are bench-testing our new solenoid pump and it looks promising. The power consumption to run it, is far less than the peristaltic pump which is terrific. We are using the same PFA tubing that we use for the HTF lines so it can handle the high temperature of 200C. The softening point of PFA is about 300C so it should be fine for the heat. After 48hrs of continuous dry operation, the tubing is showing no signs of wear due to the slick physical properties of PFA. This new pump is unique and once completed and tested, will have other applications for moving high temperature HTFs for many industrial applications.
February-The pump is installed and ready to go. should have results shortly.