What’s this all about? Aluminium is highly recyclable and takes only 5 percent of the original energy used to make it, to recycle it. But the original electrical energy requirements to produce primary aluminium electrochemically from alumina and carbon are massive. Hydro uses 26 TWh per year, producing 1.8-1.9 million tonnes of aluminium (world production is about 38 million tonnes).
While more efficient use of energy in the electrolysis process is needed, your challenge here is to develop a concept that efficiently repurposes the energy ‘wasted’ as heat from the electrolysis cell during the production process.
Where energy flows Most of the heat from the electrolysis cell is generated as ohmic heat in the electrolyte between the electrodes. This energy needs to be removed from the cell to keep it in thermal balance. In the electrolysis process we lose about 50 percent of the primary energy input as heat. To focus the development of your concept, you need to identify where heat can be recovered in and around the cell.
One consideration A possible area to start is using this ‘wasted’ energy for CO2 scrubbing (removing CO2 from the effluent air). One problem with ”low temperature” heat flow is that converting it to electricity has a very low efficiency. Dropping the temperature from a raw gas temperature of 130°C to 40°C in a heat exchanger to produce electricity typically has an efficiency of only ~5 percent. However, a new ventilation system being tested enables the use of “cold” air to drop 50-60 percent and a gas temperature of >200°C. This could be utilized in your solution.
At the heart of this challenge is ensuring the large quantities of energy needed to make this essential metal are not wasted. Considering the scale of our industry, the potential reduction in the CO2 footprint and/or of utilizing this ‘wasted’ energy in new ways is significant.
Click here to download the full brief for Challenge 1: Amp it up challenge
