EnPot was rolled out on a commercial scale at TRIMET following on from the successful trial installation on 12 pots which began in June 2014. Roman Düssel, Production Manager – Electrolysis, TRIMET Aluminium, Essen, says the goal for TRIMET has been to find pathways to allow the smelter to shift power use by +/- 25%.
"The biggest problem with our conventional cell design is that we cannot maintain an operational cell heat balance when varying cell power, meaning the pots will either 'tap out' or 'freeze over' if the power input to them is shifted up and down by such a degree," he says.
“The EnPot technology allows us to dynamically control the heat loss of the pot and therefore maintain heat balance under a wide range of operating conditions. It basically allows us to break the restraints of the current cell design and open up the operating window”, he said.
Roman says TRIMET have successfully maintained stable operations with power increases of 20% and reductions of 13%, on the 12 pots installed with the EnPot heat exchangers and are currently only limited by the remainder of the pots that are not fitted with EnPot technology.
"We have proven that when modulating power, the pots with EnPot installed operate with approximately 1 DCkWh/ kg lower energy consumption than pots without EnPot, which is a huge saving," he said.
Roman says that under normal operating conditions with normal line amperage, the pots with EnPot installed have outperformed the rest of the pots in the line with 0.25 DCkWh/kg lower energy consumption and 0.4% higher current efficiency.
"These results underpin our confidence in the EnPot technology and we are confident we will realise our goal of +/- 25% energy usage when we have it on the whole potline," he said.
Dr. Martin Iffert, former CEO of TRIMET Aluminium SE, believes that the EnPot technology can be used like a virtual battery to buffer demand against supply in Germany, as the country seeks to increase its use of renewable power generation under the Energiewende programme.
“TRIMET’s trials of the EnPot technology indicate that by being able to dynamically increase or decrease our energy use, TRIMET could become the energy bridge buffering supply and demand in Germany,” he says.
“This would enable TRIMET to become a significant part of Germany’s energy storage capacity. Our goal is to use our smelters to give Germany a virtual battery capacity of 12GWh, which would be approximately 25% of Germany’s current pump hydro storage capacity,” Dr. Iffert says.
The installed EnPot system has proven to be robust, stable and reliable with no major equipment failures or problems since start up.
The system responds quickly to set point changes and the reproducibility of the system outputs such as air flow rates and heat extraction is high. This has meant that the outcomes of any set point changes can be predicted and the system is readily customisable and controllable to changing conditions.
In April 2016 TRIMET had a lengthy power outage. The cells fitted with EnPot had less difficulty in being restarted than the cells without EnPot. The TRIMET outage proves EnPot’s value in the case of a serious power outage, that pots can be kept warmer for longer, and that restarting is less problematic.