Session: 30-05 Solar Thermal Systems

Paper Number: 127246

127246 - Preliminary Characterization of the Desolination Project Demo Plant: Design and Off-Design Operability 

This paper describes the design condition and the preliminary sizing of the components for a first-of-a-kind transcritical CO2 blend power plant coupled with solar energy and providing both power generation and desalinated water production. The plant will be built during 2025 in Riyadh (Saudi Arabia) within the framework of the EU H2020 project “DESOLINATION” and is designed to be powered by hot molten salts and to be coupled with a desalination unit based on the forward osmosis process which exploits the heat rejected by the cycle to produce fresh water. The power block consists of a transcritical power cycle using the CO2+SO2 mixture as working fluid unlocking the possibility of fluid condensation even at ambient temperatures above 40°C typical of arid areas where concentrating solar power plants are located.

The simple recuperative transcritical cycle is foreseen to work with the mixture at 82% CO₂ molar fraction (and 18% SO₂), to have a gross power output of 1.7 MW and a gross efficiency of around 30%. The cycle minimum temperature is above 50°C at design conditions (to match the high average ambient temperature of the location) a turbine inlet temperature of 550°C and a maximum pressure above 200 bar. Considering the very high minimum temperature and the limited power output, 30% of gross efficiency is a very ambitious target significantly higher than competitive technologies under the same operating conditions. Desalination section will be design on a thermal power of a 400kW_th collected by a thermal loop between the power plant and the forward osmosis system; the residual heat will be rejected through an air cooled condenser to demonstrate the condensation of the innovative working fluid even with very hot ambient temperatures.

Regarding the power cycle, the paper will address the thermodynamic design of the system, with complete heat and mass balance for each components and report the design of the primary heat exchanger, the recuperator (adopting an innovative geometry of Printed Circuit Heat Exchanger) and the air condenser. With a validated methodology from literature, the off-design performance of the cycle will be estimated. Moreover, with simplified assumptions on the piping and the hotwell, the overall working fluid inventory along the power cycle will be computed. Analysis will be extended considering a complete coupling between the desalination unit and the power plant in order to assess the real potential of the system.

Simulations of the desalination plant will be carried out with a dedicated tool able to quantify the specific heat consumption as function of the temperature, pressure and composition of the draw solution adopted in the forward osmosis section. Preliminary simulation results can show a thermal consumption of 100 kWh/m3 of fresh water for the large-scale plant can be achieved, representing an extremely competitive value with respect to conventional desalination technologies run by sensible waste heat at low temperature.

Presenting Author: Ettore Morosini Politecnico di Milano

Presenting Author Biography: Post-Doc in Energy Engineering at Politecnico di Milano. Currently working on thermodynamic cycles with CO2-based mixtures. Involved in the EU DESOLINATION project

Authors:

Ettore Morosini Politecnico di Milano
Marco Astolfi Politecnico di Milano
Michele Doninelli Università degli studi di Brescia
Paolo Iora Università degli studi di Brescia
Damien Serret Temisth SAS
Jean-Michel Hugo Temisth SAS
Giampaolo Manzolini Politecnico di Milano