Market Opportunities of Water Treatments Powered by Solar Micro Gas Turbines: Chile and Ecuador Case Studies

Abstract

Throughout the last decades the developments on desalination field have been focused on energy consumption and costs reduction. However, water recovery and brine disposal are becoming a matter of concern to desalination industry. In this work, a Zero Liquid Discharge (ZLD) unit coupled with a Solar Micro Gas Turbine (SMGT) system is presented to address, among others, the challenges of mining industry in remote areas, in particular, fossil fuel dependence, water availability and pollution derived from effluents disposal. As a way to assess the feasibility of the proposal, a techno-economic analysis of the application in two Southern American regions (Chile and Ecuador) of photovoltaic modules, wind turbines and Solar Micro Gas Turbines is performed. Afterwards, the main novel feature of the new system—i.e., the ZLD unit—is described and a sensitivity analysis on its functioning whilst coupled with the SMGT is carried out. The aim is to propose a preliminary design of the ZLD process. The selection of the optimal ratio between exhaust gases and brine mass flow rates is analyzed, as well as variation in inlet salinity and temperatures. Furthermore, the water which could be recovered from effluents, at the same time that the heat of exhaust gases from SMGT is harvested, is quantified. Lastly, according to the results obtained, a preliminary design of a 10 kWe rated power SMGT system, coupled to Reverse Osmosis (RO) and ZLD units, is proposed.

Innovative desalination system driven by a solar micro gas turbine for off-grid applications

“…A fraction of this stream is then sent to the ZLD unit, where part of the water content evaporates thanks to the thermal energy available in the exhaust gases of the micro gas turbine. The ZLD unit is a direct-contact heat exchanger whose purpose is to reduce the amount of water released for disposal [16].…”

“…The performance of the RO system for the treatment of industrial effluents and brackish or seawater has been modelled through well-known equations from literature [25], compiled in a block model callibrated against the software Q+ developed by LG Chem [26]. finally, still within the water treatment subsystem, the proof-of-concept ZLD unit has been experimentally demonstrated for this application, and the associated model has already been published by the authors [16].…”

“…Further to the aforecited potential of micro gas turbines for decentralised power, in particular applied to renewable energy sources, and based on the past experience of the authors, a solar desalination system based on SmGTs with the techno-economic features already presented in [13][14][15] seems to be a cost-effective solution with a promising future against other popular renewable desalination options integrating PV panels. This has already been explored for isolated units [16] but, according to recent literature on the topic, it might also apply to larger scales by coupling several SmGTs in parallel.…”

“…15. The ZLD system is modelled through the methodology already presented and discussed by some of the authors in [16]. The ratios of mass flow m bo /m bi and salinity S bo /S bi are estimated for operating conditions different to the rated values, noting that there is an operational limit of the inlet mass flow ratio (m gi /m bi ).…”

“…Figure 16: (a) Ratio between outlet and inlet brine salinities as a function of temperatures of inlet brine and inlet exhaust gases from the turbine in evaporation chamber, for S bi =0.07 kg/kg and m g /m b =10; (b) Ratio between outlet an inlet brine mass flow rates as a function of temperatures of inlet brine and inlet exhaust gases from the turbine in evaporation chamber, for S bi =0.07 kg/kg and m g /m b =10; (c) Ratio between outlet and inlet brine salinities as a function of temperatures of inlet brine and inlet exhaust gases from the turbine in evaporation chamber, for S bi =0.12 kg/kg and m g /m b =10; (d) Ratio between outlet an inlet brine mass flow rates as a function of temperatures of inlet brine and inlet exhaust gases from the turbine in evaporation chamber, for S bi =0.12 kg/kg and m g /m b =10[16] …”