Geothermal Water Desalination Research Articles

Thermoeconomic and environmental optimization of geothermal water desalination plant with ejector refrigeration system

In this paper, a multi-objective optimization of geothermal water desalination plant with ejector refrigeration system is proposed. The multi-objective antlion optimization algorithm is used. Six different optimization scenarios were performed with economic (total investment cost and profit) and thermodynamic (exergy destruction) objectives for refrigerants R11, R114 and R717. Multi-criteria decision making with integrated AHP and PROMETHEE II approach is executed for evaluating the most suitable design project and refrigerant. Besides economic and thermodynamic criteria, three additional environmental criteria were used: ozone depletion potential, global warming potential and toxicity. The sensitivity analysis showed that water desalination plant with R114 refrigerant and coefficient of performance 0.507 is optimal for a wide range of criteria weights. A similar result of the optimal design point is obtained in scenarios where only economic objective functions were considered during the optimization procedure. Furthermore, it is proved that R114 Pareto front is more optimal in comparison with other refrigerants.

New approach to the utilisation of concentrates obtained during geothermal water desalination

New approach to the utilisation of concentrates obtained during geothermal water desalination

Application of a Hybrid Uf-Ro Process to Geothermal Water Desalination. Concentrate Disposal and Cost Analysis

Abstract M embrane-based water desalination processes and hybrid technologies are often considered as a technologically and economically viable alternative for desalination of geothermal waters. This has been confirmed by the results of pilot studies concerning the UF-RO desalination of geothermal waters extracted from various geological structures in Poland. The assessment of the feasibility of implementing the water desalination process analysed on an industrial scale is largely dependent on the method and possibility of disposing or utilising the concentrate. The analyses conducted in this respect have demonstrated that it is possible to use the solution obtained as a balneological product owing to its elevated metasilicic acid, fluorides and iodides ions content. Due to environmental considerations, injecting the concentrate back into the formation is the preferable solution. The energy efficiency and economic analysis conducted demonstrated that the cost effectiveness of implementing the UF-RO process in a geothermal system on an industrial scale largely depends on the factors related to its operation, including without limitation the amount of geothermal water extracted, water salinity, the absorption parameters of the wells used to inject water back into the formation, the scale of problems related to the disposal of cooled water, local demand for drinking and household water, etc. The decrease in the pressure required to inject water into the formation as well as the reduction in the stream of the water injected are among the key cost-effectiveness factors. Ensuring favourable desalinated water sale terms (price/quantity) is also a very important consideration owing to the electrical power required to conduct the UF-RO process.

Evaluation of geothermal energy in desalination by vacuum membrane distillation

This paper presents the energy evaluation of the cross-flow vacuum membrane distillation (VMD) for three types of lab-fabricated polyvinylidene fluoride (PVDF) membranes and the commercial Westran S PVDF membrane. Membranes with the effective area 23.5cm2 are tested with distilled water and geothermal water as the feed solutions. Results show that the membrane porosity controlled the flux through the fabricated membranes and the commercial membrane. The commercial membrane with porosity of approximately 76.5%, which was the most porous among the tested membranes, gave the highest flux at 9.28kg/m2 h under the optimum conditions of 33.2L/h feed flow rate and 30kPa downstream pressure. The corresponding specific energy consumption was 66.03kW/kgh−1 when distilled water was examined. Heating energy of 87–89kW/kgh−1, which is approximately 95% of the total energy consumption, could be saved when the warm geothermal water is fed directly into the VMD system. The water produced meets the drinking water quality with the TDS varying between 102 and 119ppm, thus the geothermal water desalination using the VMD system to produce the drinking water is satisfactory. An economic analysis for a 20,000m3/d VMD desalination plant finds that the water production costs are $0.50/m3 and $1.22/m3 respectively for the plant operated with and without geothermal energy (GE). Compare to the plant without GE utilisation, the water production costs of the plant operated with GE are less than $0.50/m3 that is at least $0.72/m3 or approximately 59% in cost saving when the water fluxes are larger than 6.6kg/m2h. The specific membrane cost reduced from $0.058/m3 to $0.035/m3 when the membrane life extended from 3 to 5years.

New directions in nanofiltration applications — Are nanofibers the right materials as membranes in desalination?

Various desalination technologies are emerging to tackle the increasing water demand globally. Among them, nanofiltration (NF) has recently received an increased attention in the literature to desalt low salt content water. The developments of new membrane materials and novel processes have shown that NF can be potentially applied in the desalination due to enhanced flux, lower operational pressure and energy savings. Nanotechnology based products such as nanoparticles and nanofibers have been introduced to enhance the properties and performance of the membranes derived from conventional polymeric membrane materials and conventional phase inversion processes. When mid-layer made up of electrospun nanofibrous membranes (ENMs) produced by electrospinning has been applied in the thin film composite (TFC) configuration in NF application; higher permeate fluxes than conventional membranes were achieved. This has been ascribed to the high porosity, low transmembrane pressure and interconnected pore structure of ENMs. The ENMs as such or after mixing with nanoparticles are also explored in the area of membrane distillation for seawater desalination. In this article, recent developments of ENMs as TFC membranes in NF application and as desalination membranes in the membrane distillation, geothermal water desalination, and capacitive deionization application are summarized here.

The pilot of geothermal water desalination installation in Poland

The pilot geothermal water desalination installation in Poland was commissioned at the Geothermal Laboratory of the Mineral and Energy Economy Research Institute of the Polish Academyof Sciences (PAS MEERI). Laboratory is localised in Podhale region, in south-eastern Poland. Geothermal waters are extracted from carbonate formations of the Middle Eocene and from Middle Triassic limestones and dolomites. These exhibit relatively low mineralisation – 3 g/dm3. Their temperature at the well outlet ranges 90°C. Installation is supplied with water at a temperature of about 35°C. The capacity has been set at 1 m3/hour of desalinated water. The objective of geothermal water desalination will be to obtain water that meets the requirements stipulated in the regulation of the Minister of Health of 29 March 2007 (Journal of Laws of 2007, No. 61, item 417) concerning the quality of water intended for human consumption. The preliminary results from the geothermal water desalination study conducted at the PAS MEERI are optimistic. In order to validate the assumptions made in the context of industrial applications, further studies have to be conducted in accordance with the project plans. It is certain, however, that the utilization of geothermal water for drinking purposes on an industrial scale will require, first of all, better and more efficient water cooling. Optimum utilization of the thermal waters obtained is an important issue for most geothermal plant both in Poland and abroad. Efficient geothermal water management has one main goal: optimizing system operation and improving the economics of geothermal plant operation. Additionally, the use of cooled water for drinking purposes, particularly for open drain installations (without injecting cooled water into the formation) will contribute to the comprehensive utilization of geothermal water and the decentralization of drinking water production. Therefore the present study concerns two significant research areas: geothermics (cooled water utilization methods) and hydrogeology (water management).

A small solar desalination plant for the production of drinking water in remote arid areas of southern Algeria

The common methods of desalination salt water for production of fresh water by distillation, reverse osmosis and electrodialysis are intensive energy techniques. However, in remote arid areas, the desalination needs not exceed a few cubic meters per day. This decentralised demand favours local water production by developing other desalination processes, especially those using renewable or recovered energy (solar, geothermal, etc.). Solar desalination process is one of these methods used to resolve the scarcity of fresh water. Several reviews have been published by different authors. Small production systems as solar stills can be used if fresh water demand is low and the land is available at low cost. To supply the population of remote arid lands of South Algeria with drinkable water, solar distillation of brackish waters is recommended. It satisfies some of theses demands. Solar stills are used to produce fresh water from brackish water by directly utilising sunshine. These stills represent the best technical solution to supply remote villages or settlements in South Algeria with fresh water without depending on high-tech and skills. The production capacity indicates a possible daily production of far more than 15 l/m 2d. Therefore, the still has a place in the upper range of known comparable products with regards to production output. This depends on the material used and the price of the solar stills and their accessories. The best working temperature solves most problems. Small, modular high-performance stills with features like the possibility of decentralised use, less maintenance and robust construction can help to reduce fresh water scarcity. The recent development of stills based on new concepts and heat recovery has been successful. The technical optimization is still in process today, it aims to improvement of the efficiency of these distillers. In our research work, a plant for brackish water distillation by directly sunshine and heat recovery was constructed and investigated experimentally and theoretically in South Algeria. This study aims the improvement of the performance of this solar distillation plant, conducted under the actual insulation, for brackish underground geothermal water desalination.

Solar desalination plant for small size use in remote arid areas of South Algeria for the production of drinking water

The common methods of desalination of salt water for production of fresh water by distillation, reverse osmosis and electrolysis are energy-intensive techniques. However, in remote arid areas, the desalination needs not exceed a few m 3/d. This decentralized demand favors local water production by developing other desalination processes, especially those using renewable or recovered energy (solar, geothermal, etc.). Solar desalination process is one of these methods used to resolve the scarcity of fresh water. Several reviews have been published by different authors [1–5]. Small production systems as solar stills can be used if fresh water demand is low and the land is available at low cost. To supply the population of remote arid lands of South Algeria with drinkable water, solar distillation of brackish waters is recommended. It satisfies some of these demands. Solar stills are used to produce fresh water from brackish water by directly utilizing sunshine. These stills represent the best technical solution to supply remote villages or settlements in South Algeria with fresh water without depending on high-tech and skills. The production capacity indicates a possible daily production of far more than 15 I/m 2d. Therefore, the still has a place in the upper range of known comparable products with regard to production output. This depends on the material used and the price of the solar stills and their accessories. The best working temperature solves most problems. Small, modular high-performance stills with features like the possibility of decentralized use, less maintenance and robust construction can help to reduce fresh water scarcity. The recent development of stills based on new concepts and heat recovery has been successful. The technical optimization is still in process today. It aims at improvement of the efficiency of these distillers. In our research work, a plant for brackish water distillation by direct sunshine and heat recovery was constructed and investigated experimentally and theoretically in South Algeria. This study aims at the improvement of the performance of this solar distillation plant, conducted under the actual insulation, for brackish underground geothermal water desalination.

Fluidised bed crystalliser and air gap membrane distillation as a solution to geothermal water desalination

Tunisia has five major geothermal districts. Recorded hot spring temperatures range from 294 to 340 K with flow rates 0.1–10 2 L/s. In southern parts available groundwater resources are mostly hard and brackish (3 g/L). Recently, Tunisia has resorted to this resource for agriculture and potable water uses. Cooling towers have been built to lower down the temperature and hardness. Cooled brackish water irrigates greenhouses and feeds desalination plants. The cooling operation of groundwater rejects an important quantity of thermal energy in the atmosphere. However, energy requirements of thermal desalination plants are too excessive to be supplied by a geothermal resource. Membrane distillation (MD) is an emerged desalination technology, which can be driven by a thermal energy at low enthalpy (less than 363 K) as geothermal energy, and a fluidised bed crystalliser can ensure reduction of an important portion of hardness without significant loss of temperature. MD is realised by means of a microporous hydrophobic membrane separating a warm solution from the cooling chamber, which contains either liquid or gas. A fluidised bed crystalliser permits production of from it of a granular crystal calcium carbonate from the consumption rates of calcium ions, using aragonite or sand as seeding materials. The purpose of this paper is to realise experimental assembly constituted of fluidised bed crystalliser (FBC) and a cell of air gap membrane distillation (AGMD). It presents preliminary results related to characterisation of fluidised bed, growth of seeded particles size of CaCO 3 and operating parameters of AGMD. In laboratory scale, the technical feasibility has been shown. More investigation is needed to prove the efficiency and availability of coupled AGMD with FBC.