Simulations of CSP combined with CO2 mixed power cycles and a forward osmosis desalination system in Dubai

Simulations of CSP combined with CO2 mixed power cycles and a forward osmosis desalination system in Dubai

This year, our project coordinator, Politecnico di Milano (POLIMI) carried out simulations at its CSP (concentrated solar power) plant in Dubai to combine CSP with CO2-mixed electric cycles and a forward osmosis (FO) desalination system.

Using innovative technologies, POLIMI’s CSP plant has demonstrated high solar-electric efficiencies (around 19% on an annual basis) and very low specific thermal consumption of fresh water (around 90 kWhth/m3) when PABG2000 is used as the drawing agent. The synergy between electricity and freshwater production was effective.

In particular, if the CSP+FO solution studied in DESOLINATION is compared with the CSP+MED solution, assuming the same solar power plant and energy cycles, freshwater production is increased by over 40%.

The DESOLINATION project aims to develop an innovative desalination system combining direct osmosis and membrane distillation, using a draw-off solution. Forward osmosis means that seawater is extracted from the sea, the water is drawn through the membrane by the draw solution and the remaining minerals (brine) are rejected.

When the DESOLINATION solution is compared with a PV+RO plant, a 47% reduction in reflective surface is predicted, if the PV+RO plant produces both fresh water and electricity.

We have also carried out an experimental campaign on the coalescer* using a solution of water and PAGB2000, the aim being to obtain an expression for the separation efficiency, which will then be used in simulations.

*Coalescer: used to separate elements from an emulsion (i.e. liquid water and oil from compressed air using a coalescing effect)

Finalization of the thermophysical characterization of CO2 mixtures to power our desalination plant

Finalization of the thermophysical characterization of CO2 mixtures to power our desalination plant

Our project has reached an important milestone: after an initial screening of promising dopants to be blended with CO2, thermal stability tests of the mixtures were carried out, and material compatibility test were performed for the most interesting blends. As an result, the most interesting CO2 mixtures for the pilot plant were determined.

The DESOLINATION project aims to develop an innovative CSP (Concentrated Solar Power) cycle using CO2 blends together with a heat recovery system to power a desalination plant. The working fluid becomes supercritical CO2-based and the turbomachinery is adapted to new ranges of temperatures and pressures, to be adapted to future CSP plants.

Thermo-chemical stability of the working fluid is one of the most important aspects to be considered for the working fluid selection, especially when dealing with high-grade sources such as concentrated solar power.

The thermodynamics of CO2 blends have been characterised based on experimental data available in the literature as well as with experimental campaign.

Relevant outcomes have been obtained from the test performed on the CO2 mixtures selected after an initial screening: three different dopants have successfully passed the thermal stability test above 550°C with the consolidated methodology developed in the Fluid Test Laboratory of our project partner, the University of Brescia.

However, it is crucial not only that the working fluid avoids chemical dissociation, but also that the interaction between the mixture and the equipment material is acceptable, particularly in the high-temperature sections of the power plant.

For this reason, the two most interesting fluid candidates have been tested in material compatibility test: a prolonged exposure of different material samples at the mixture atmosphere at 550°C, the maximum temperature of the pilot plant, provided interesting results.

The metal samples have been analysed with several methodologies, including mass weight change, optical microscope, and scanning electron microscope.

Our next step will be to test the compatibility of the new materials and coatings with the CO2 mixtures most suitable for the pilot plant. Stay tuned!

Contributors: Paolo Giulio IORA, Gioele Di Marcoberardino and Michele Doninelli (UNIBS)

Exploring the application of polymeric active layers on electrospun membranes to improve their performance for forward osmosis (FO)

Exploring the application of polymeric active layers on electrospun membranes to improve their performance for forward osmosis (FO)

Our project partner, TEKNIKER, is analyzing the promising use of electrospun nanofiber-based forward osmosis membranes in the desalination process, seeking to improve water flow and rejection performance through the implementation of advanced active layers.

The DESOLINATION project aims to develop an innovative desalination system combining direct osmosis and membrane distillation, using a draw-off solution. Forward osmosis means that seawater is extracted from the sea, the water is drawn through the membrane by the draw solution and the remaining minerals (brine) are rejected.

In recent decades, the electrospun nanofiber mat composed of numerous stacked polymeric nano-sized fibers has attracted growing attention in the fabrication of high-performance FO membranes. The unique interconnected pore structure and high porosity of the membranes can endow the composite FO membrane with a lower structural parameter, leading to the effective alleviation of ICP.

The DESOLINATION project analyzes the modification of the polymer surface to improve the performance of water treatment membranes.

Our project partner, the Technical University of Eindhoven (TU/e) is obtaining electrospun membranes of different polymers and TEKNIKER is applying polyamide thin film active layer on the electrospun membrane by interfacial polymerization, being possible to control the thickness of this active layer by adjusting the chemistries of the reactants and the conditions of the deposition and curing process.

The next step is to test the performance of the obtained membranes. Stay tuned!

Contributors: Saioa Herrero López and Miren Blanco

Finalizing the planning phase of the DESOLINATION project’s pilot plant

Finalizing the planning phase of the DESOLINATION project’s pilot plant

Our project partner, Protarget AG, is actively preparing the pilot plant site and all its equipment at Kind Saud University (KSU) in Riyadh, which will host the demonstration and commissioning of DESOLINATION’s innovative technology!

Over the past six months, the initial planning and design phase of the project site, which includes molten salt heaters powered by both fossil fuels and electricity, has been completed.

Our demonstration site, Riyadh Technology Valleys, is located at King Saud University’s grounds in Riyadh, spanning a total area of 1.67 million m2.

Collaborative initiatives with KSU have yielded specifications and initial concepts for the electrical supply and a cost-effective foundation concept, as well as the finalized of the top-level concept and specifications for the waste heat recovery system.

The work on the waste heat recovery system has included the creation of a spatial model to facilitate the optimal positioning heat exchanger, bypass and exhaust.

Furthermore, the planning and initial design phases for adaptive coupling have been successfully executed.  

In parallel to this, our project partner, Tekniker, has advanced the development of the Distributed Control System (DCS) and security concept, while simultaneously laying the foundation for functional descriptions of all domains.

TEMISTh has launched the manufacture of DESOLINATION heat exchanger core!

TEMISTh has launched the manufacture of DESOLINATION heat exchanger core!

The DESOLINATION project has reached an important milestone: after an initial design and simulation phase carried out by our project partner TEMISTh, the first heat exchanger model has now been printed!

Heat Exchangers can take different forms depending on many parameters: temperatures, pressures, chemical properties of the fluids, etc. But they are critical to the heat transfer within the CSP cycles to recover heat from the sun and make the turbine work.

In DESOLINATION, specific work will be on exchanging heat between the power cycle (air in the existing plant, CO2 in the innovative one) and the desalination draw solution (highly concentrated solution). New Printed Circuit Heat Exchangers (PCHEs) and Printed Fin Heat Exchangers (PFHEs) will thus be produced.

Following a simulation and design phase for supercritical CO2 and molten salt, our project partner TEMISTh has launched the manufacture of the Heat Exchanger core (system used to transfer heat between a source and a working fluid).

The aim of this first mock-up is to answer technical questions such as powder removal, assembly and design validation.

The next step is to test the mock-up on an sCO2 loop for validation.