A novel process is presented to generate electricity from low-grade heat by combining a Reverse Electrodialysis membrane with an Adsorption desalinator in a closed-loop system. A Reverse Electrodialysis membrane generates electricity by controlled mixing of two salt solutions of different concentrations. An Adsorption desalinator restores the initial salt gradient by utilising low-grade heat for the separation. In this study the process is designed from optimising the salt and material selection to the development of the real system application. Energy and exergy efficiencies of the proposed system show the potential of this novel renewable energy technology. The efficiencies of 227 salts with a range of different valences and 10 adsorption materials have been investigated over a large number of system parameters. The results show that the optimised system can achieve an exergy efficiency of up to 30 %. Moreover, high salt concentrations do not significantly increase the specific energy consumption of the Adsorption desalinator, which allows operating the Reverse Electrodialysis membrane at the optimal salt concentrations.

Adsorption heat transformers use low-grade heat to produce potable water and provide cooling at the same time. In this study, we present a comprehensive performance analysis for an experimental system featuring the world's smallest design using silica gel, which is commonly used as benchmarking material. We analyse the system performance in a thorough cycle analysis that quantifies the influence of isosteric heating times and cycle times onto the adsorption working capacity. In addition, the performance is assessed through common performance indicators for desalination as well as cooling. We found that the system achieved a Specific Daily Water Production of up to 10.9 kg w /(kg sg d) at 80°C. The combination of cooling and desalination is discussed highlighting advantages as well as disadvantages, which are often neglected. The results show that silica gel has a high performance in desalination, which decreases by more than 60 % if cooling is desired as well.

Closed-loop Reverse Electrodialysis is a novel technology to directly convert low-grade heat into electricity. It consists of a reverse electrodialysis (RED) unit where electricity is produced exploiting the salinity gradient between two saltwater solutions, coupled with a regeneration unit where waste-heat is used to treat the solutions exiting from the RED unit and restore their initial composition. One of the most important advantages of closed-loop systems compared to the open systems is the possibility to select ad-hoc salt solutions to achieve high efficiencies. Therefore, the properties of the salt solutions are essential to assess the performance of the energy generation and solution regeneration processes. The aim of this study is to analyse the influence of thermodynamic properties of non-conventional salt solutions (i.e. other than NaCl-aqueous solutions) and their influence on the operation of the closed-loop RED. New data for caesium and potassium acetate salts, i.e. osmotic and activity coefficients in aqueous solutions, at temperature between 20 and 90°C are reported as a function of molality. The data are correlated using Pitzer's model, which is then used to assess the theoretical performance of the whole closed-loop RED system considering both single and multi-stage regeneration units. Results indicate that KAc, CsAc and LiCl are the most promising salts among those screened.

This work investigates the application of novel sorption materials to heat-powered desalination systems. Two ionic liquids 1-ethyl-3-methylimidazolium acetate (Emim-Ac) and 1ethyl-3-methylimidazolium methanesulfonate (Emim-Oms) ionic liquids were impregnated in two silica supports, namely Syloid AL-1FP and Syloid 72FP. Emim-Ac and Emim-Oms composite sorbents have been compared on morphology, water vapor sorption equilibrium and heat of sorption. Fourier-transform infrared spectroscopy shows the ionic liquid partly organises on the silica surface. When used in a sorption desalination process powered by low grade heat at 60°C, these composites have exceptionally high theoretical working capacities ranging from 1 to 1.7 gwater gsorbent-1. Experimental tests on a lab scale desalinator show that Emim-Ac/Syloid 72FP in real operating conditions can produce 25 kgwater kgsorbent-1 day-1. To date, this yield is 2.5 times higher than the best achieved with silica gel.

• Design and experimental results of the world's most compact adsorption desalinator for the first time • Achieving a Specific Daily Water Production of 7.7 kg w /(kg sg d) and Performance Ratio of 0.6 • The small scale is not detrimental to the performance as the system is on a par with the best performing system in the literature • A novel thermal response experiment informs about the partition of energy, the heat of adsorption, and water production