Report

Teaser, summary, work performed and final results

Periodic Reporting for period 3 - RED-Heat-to-Power (Conversion of Low Grade Heat to Power through closed loop Reverse Electro-Dialysis)

Teaser

ProblemLarge amounts of primary energy are wasted in the form of low temperature heat that is discarded to the environment, either indirectly or through cooling facilities in industrial plants. RED-Heat-to-Power adopts a game-changing approach that generates electricity from...

Summary

Problem
Large amounts of primary energy are wasted in the form of low temperature heat that is discarded to the environment, either indirectly or through cooling facilities in industrial plants.
RED-Heat-to-Power adopts a game-changing approach that generates electricity from this low grade heat. The electricity is generated from salinity gradients using Reverse Electrodialysis (RED) in a closed-loop system, where artificial saline solutions are used as working fluids. The solutions exiting from the RED unit are then regenerated, in order to restore the original salinity gradient using low-temperature heat.

Importance
The new system has the following characteristics, which make it ideal for contributing to the mix that will form the backbone of the future energy system.
1) Competitive electricity generation: The use of artificial solutions provides the flexibility to choose the salts and the conditions that maximise the productivity of the Reverse ElectroDialysis process, making it possible to drive costs down.
2) Exploiting widely available low-grade heat: The system can be installed practically anywhere in the world where low grade heat is available.
3) Offering flexibility to the power system: The technology is a fully controllable source of electricity. This flexibility is a distinctive advantage over variable renewable energy.
4) A safe and clean source of energy: The technology involves only simple circulation pumps and any noise will be minimal. There are very low operation and maintenance requirements.

Project Objectives:
The overall objective is to prove this revolutionary concept, develop the necessary materials, components and know-how for achieving high performance and bring it to the level of a lab prototype.

Conclusions:
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.

Work performed

The consortium explores the materials and components that maximise performance and minimise costs. 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.

In terms of dissemination and exploitation:
• More than 3,500 users have viewed the project videos on YouTube
• Over 9,800 relevant stakeholders have been reached through representation at 37 events
• Over 3,600,000 people reached through the coverage of the UNIPA project activities by Italian TV in three separate occasions.
• Twenty-eight scientific papers have been published in high-impact peer reviewed journals.
• There have been interactions with 13 potential end-users, discussing possible next steps in implementing the systems

Final results

Beyond the state of the art
Reverse Electrodialysis has been used so far only for power production from salinity gradients generated by natural streams (e.g. river water/seawater or seawater/brine). With this project, we applied for the first time RED in a closed-loop, thus opening a new era of the salinity gradient power technologies and reshaping the low-temperature heat prospects. 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%)

Impact
Replicability: The system is highly replicable, as it is modular and can be applied anywhere where a source of low temperature heat is available (solar, geothermal or waste heat)
Socio-economics: The system is safe and widely acceptable by society as it quiet, with low operation and maintenance requirements, it does not involve high pressures or high temperatures.
Environment: The system generates electricity using available heat resources and there are no additional associated emissions of carbon dioxide or any other pollutants. In addition, the use of low-temperature heat that would be otherwise wasted increases the resource efficiency of the industry.

Website & more info

More info: http://www.red-heat-to-power.eu/.