Final project results
The project has shown that the RED Heat Engine has the potential to achieve high efficiency and low cost for converting low-grade-heat to electricity. A roadmap has been developed with the actions required to bring the technology closer to the market. The main focus is on improving further the performance of the ion exchange membranes, as this has the highest impact on the system performance. The first applications targeted are for large systems that use the waste heat from industry or from gas compression stations.
A wide range of configurations, technologies, salts and solvents have been explored by a multidisciplinary team of scientists and engineers from the academia and the industry. Two combinations were selected for testing as integrated systems. A RED with membrane distillation and a RED with thermolytic salts and distillation columns for regeneration. Both have been tested in the lab as integrated systems proving the concept of the RED Heat Engine.
At the same time, advanced research and development activities explored options for improving the performance of the system. As part of these activities, new ion exchange membranes have been developed, reaching in the lab power densities at levels never seen before.
The modelling and simulation activities resulted in an optimised design, while providing a platform, where the performance of the system for different configurations and operating conditions can be predicted. The simulation platform has been extensively validated with several experimental activities.
The modelling shows that the best combination is the RED with multiple effect distillation (MED). While this cannot be demonstrated at scaled-down level, the process simulation shows that high efficiencies can be reached. It has been shown that with specific improvements on the membrane composition that are targeted, the conversion of heat that is at 100 degrees C to electricity can be achieved with efficiency of just over 10%.
A detailed cost assessment has also been performed. This has concluded, that when reaching the performance foreseen above with the RED-MED system using improved ion exchange membranes, the levelised cost of electricity will be between 0.04 and 0.05 Euro per kWh. The environmental life cycle assessment concluded that the impacts of the RED-MED heat engine are significantly lower compared to all conventional power generation technologies and lower or at the same level with all renewable energy technologies. Finally, a resource analysis has shown that there are over 480 TWh per year available as waste heat at about 100 degrees C from industry, biogas plants, gas compressing stations and in boats.
In the last phase of the project, a prototype has been constructed, which operated with real waste heat, at the industrial production facility of FUJIFILM, in the Netherlands. This is the first prototype in the world of a RED Heat Engine operating in a real environment.
The project results have been presented in 28 eight scientific papers that have been published in high-impact peer reviewed journals.
The most remarkable achievements are listed below:
- Record power density in the RED system of 39 W per m2 of cell pair
- Record specific thermal energy consumption of Membrane Distillation: 46.1 kWh thermal per cubic meter
- Use of Adsorption Desalination for the regeneration process, allowing the heat engines to be powered by waste heat at temperatures as low as 40 degrees Celcius.
- The first prototype in the world of a RED Heat Engine operating in a real environment using industrial waste heat
- Scaling up capacitive reverse electrodialysis to industrial level
- Optimised design that could potentially reach efficiency of 10% (heat at 100 degrees C, i.e exergetic efficiency of about 50%)