Flash Plants Research Articles

Study the effect of solar power on the efficiency of desalinating saline water: Case studies Al-Khafji and Gulf of Aqaba areas

The desalination of salty water has become a necessary industrial process to overcome the next global shortage in freshwater. In this study, adding a Reheat Solar Collector Cycle (RSCC) to a multi-stage flash plant is used to increase the optimization of the desalination process, improving efficiencies, reducing energy, and increasing the production of freshwater demands to overcome the global crisis of shortage in freshwater. Two projects employ this numerical technique. The first project is conducted in the Al-Khafji multi-stage flash plant in Saudi Arabia with an input mass flow rate of 1 Mkg/h (277.78 kg/s), TDS of 35,000 ppm, and wind velocity of 1 m/s. The second project is conducted in the Gulf of Aqaba in Jordan with an input mass flow rate of 1 Mkg/h (277.78 kg/s), TDS of 40,000 ppm, and wind velocity of 1 m/s. The module of the LS-2 Parabolic Trough Collector (PTC) is used to gain the required energy to heat seawater. The results show that in the Al-Khafji project, an increase of 7.1% in the plant capacity per day and an increase in efficiency from 7.8 to 8.4 were observed. While, in the Gulf of Aqaba, an increase of 7.7% in the plant capacity per day and an increase in efficiency from 7.8 to 8.4 are observed.

Advanced structures of reversal multi-stage flash desalination

Three different modifications of the reversal multi-stage flash (MSF) plant are proposed and compared. One configuration consists of hybrid MSF and membrane distillation (MD), denoted as HYB, where the MD is linked to the MSF to leverage the thermal energy of the MSF outlet streams. The other configurations comprise cascaded MSF blocks connected sequentially to harness the thermal energy of the reject brine. One of the cascades uses independent external cooling water and is termed ICB while the other, termed CCB, uses the seawater intake to recover the heat in the brine cooler reducing the feed heating duty. Simulation indicated that the ICB possesses the highest recovery ratio of 33.6 % and the lowest specific area requirement of 327 m2/(kg/s) but the largest specific energy consumption of 320 kWh/m3. The CCB has the lowest specific energy consumption of 139 kWh/m3 and highest GOR of 4.9 but the lowest recovery ratio of 18.3 %. However, if the reversal MSF is powered by free waste heat, CCB possesses the minimum cooling demand and hence specific energy requirements. However, it has the minimum recovery ratio. Alternatively, the HYB can be argued as the best structure as it owns the second lowest energy consumption and second higher recovery ratio.

RETRACTED:A comprehensive study of a novel multigeneration system using a combined power plant based on geothermal energy and oxyfuel combustion

In order to increase the energy density and generate more products in a sustainable framework, the current study proposes a geothermal-driven power plant combined with an electrolyzer, boosted by an oxyfuel combustion power plant for a novel multigeneration task. The system produces power, heating, methanol, and carbon dioxide (CO2) in a coherent manner, benefiting from low-emission framework and high thermodynamic performance. This system has not been evaluated before. The proposed system consists of a combined flash and binary geothermal plant, a hydrogen production unit, an oxyfuel power unit, a heat and power generation unit, a transcritical CO2 Brayton cycle, a steam Rankine cycle, and a methanol generation unit. Hence, the proposed system is analyzed from the energy, exergy, environmental, and economic points of view. In addition, a parametric analysis is performed to assess the effects of some basic thermodynamic parameters on the cycle performance. The parametric study reveals that the increase in the working fluid temperature leads to an increase in the net power and energy and exergy efficiencies, and low pressure of the gas turbine is an important factor for enhancing the total thermodynamic efficiency of the system. Also, the system's energy and exergy efficiencies together with the total unit cost of products are found to be 47.2%, 40.34%, and 5.53 $GJ, respectively. Moreover, the CO2 footprint corresponding to the electricity and methanol outputs are obtained at 0.0023 kgCO2kWh and 0.056 kgCO2kgMeOH, respectively.

Carbon negative geothermal: Theoretical efficiency and sequestration potential of geothermal-BECCS energy cycles

Geothermal systems are an attractive option for baseload electricity generation with low emissions intensity (average 122 gCO2/kWh). However, about 70% of geothermal systems are low or medium enthalpy (<160°C), which often renders them uneconomic to develop for electricity production. A solution to increase both power production and utilization efficiency of these systems is hybridization with a biomass fuel source. In this work, we introduce and verify the concept of biomass hybridization combined with in-line dissolution and reinjection of biomass flue CO2. This subclass of bioenergy and carbon capture and storage (BECCS), termed geothermal-BECCS, has improved power production and negative CO2 emissions. This dual approach of using geothermal systems for power production and as carbon sinks can be a potential decarbonisation tool in areas with suitable geothermal and bioenergy resources.Here, we quantify the thermodynamic and sequestration performance of four geothermal-BECCS configurations. Up to 100% of flue gas is dissolved and reinjected with the spent geofluid. Scaled to a 1 kg/s geofluid production rate, flash and binary benchmark plants generated 32 and 43 kWe at efficiencies of 6 and 8%, respectively. In comparison, four geothermal-BECCS designs yielded 64 kWe at 9% efficiency (flash plant), 76 kWe at 9% efficiency (ORC binary plant), 62 kWe at 7% efficiency (compound flash-binary plant), and 589 kWe at 20% efficiency (bioenergy based geothermal-preheat plant). Annual biogenic CO2 sequestration rates ranged from 217 to 675 tonnes per kg/s with emissions intensities from -131 to -922 gCO2/kWh. By simultaneously boosting low-emissions energy and sequestering biogenic CO2, geothermal-BECCS promises to be an essential technology for meeting climate targets.

Numerical simulation and production prediction assessment of Takigami geothermal reservoir

A numerical model was developed for the Takigami geothermal reservoir. A conceptual model of the field was constructed, initial and boundary conditions were defined according to available data. For the optimum model, permeability values of assigned rock types, mass flow rates, enthalpies, and locations of recharge zones were estimated according to matching between computed temperature for wells and their temperature profiles before the exploitation. Observed and calculated temperature profiles confirmed the validity of the conceptual model. The best model could successfully reproduce the initial temperature profiles of 13 wells located mainly in the production area. A developed model was used as an initial model for future prediction of the reservoir performance. The prediction simulation was conducted by assuming two different development scenarios for the Takigami geothermal power plant. Scenario I was continuing the current power production. Scenario II was to investigate producing 8.6 MWe more electricity by employing bottoming binary cycle to the currently under operation single flash plant. Effects of production and reinjection temperatures under proposed development scenarios were evaluated. Simulation results indicated that most probably there is no direct interaction between reinjection and production zones in the Takigami reservoir, and installing a binary plant will not have any severe impact on reservoir performance.

LCA and Exergo-Environmental Evaluation of a Combined Heat and Power Double-Flash Geothermal Power Plant

This study deals with the life cycle assessment (LCA) and an exergo-environmental analysis (EEvA) of the geothermal Power Plant of Hellisheiði (Iceland), a combined heat and power double flash plant, with an installed power of 303.3 MW for electricity and 133 MW for hot water. LCA approach is used to evaluate and analyse the environmental performance at the power plant global level. A more in-depth study is developed, at the power plant components level, through EEvA. The analysis employs existing published data with a realignment of the inventory to the latest data resource and compares the life cycle impacts of three methods (ILCD 2011 Midpoint, ReCiPe 2016 Midpoint-Endpoint, and CML-IA Baseline) for two different scenarios. In scenario 1, any emission abatement system is considered. In scenario 2, re-injection of CO2 and H2S is accounted for. The analysis identifies some major hot spots for the environmental power plant impacts, like acidification, particulate matter formation, ecosystem, and human toxicity, mainly caused by some specific sources. Finally, an exergo-environmental analysis allows indicating the wells as significant contributors of the environmental impact rate associated with the construction, Operation &amp; Maintenance, and end of life stages and the HP condenser as the component with the highest environmental cost rate.

Exploitation assessment of geothermal energy from African Great Rift Valley

Countries that are in the Great Rift Valley have one of the lowest average annual electricity consumption per capita in Africa with a value of 164 kWh per inhabitant. Furthermore, the electrification rate is 34% that is more than fifty percentage points below the world average, which is around 86%. One possible solution to improve the electrification rate is to properly exploit the energy resources present in the territory. One of the most significant energy sources of this region is certainly geothermal energy which has a potential of about 15 GWe, mostly concentrated in Ethiopia. Furthermore, it is possible to find the resource in a wide temperature range, not only to produce electricity, which, nonetheless, has a very limited exploitation rate, as only 900 MWe are installed between Kenya and Ethiopia, but also for direct use. In this study, two geothermal power plants for two different geothermal sites, Corbetti and Arus-Bogoria, respectively in Ethiopia and Kenya, have been hypothesized after analyzing the resource potential. For the first, which has been estimated to be of high enthalpy (~300°C), a flash plant configuration was assumed, and the estimated energy production potential was found to be around 50-100 MWe. While for the second, at medium enthalpy (T&lt;200°C), the use of a binary cycle plant was assumed with an obtained production of about 20 MW of electricity. Finally, the possibility of geothermal water exploitation for greenhouse heating, drying of agricultural products, civil sanitary uses, recreational uses (spa), or for industrial purposes has been assessed.

Hybrid desalination and power generation plant utilizing multi-stage flash and reverse osmosis driven by parabolic trough collectors

This investigation represents the optimum operation of a co-generation plant producing water and electricity at a specified geographical location in Ras Gharib, Egypt. A model has been set employing Parabolic Trough Collectors (PTC) utilizing molten salt as the working fluid for the solar island which exchanges heat with a simple steam Rankine cycle. Thereby, the steam turbine generates an adequate amount of electricity used to cover all the plants’ requirements including the Reverse Osmosis (RO) water desalination unit demand. Moreover, the Multi-Stage Flash (MSF) plant acts as a condenser for the proposed system, taking full advantage of hot steam exiting the turbine unit to desalinate seawater. The results are displayed considering the optimum operation of the plant along the year anticipating the amount of freshwater and electricity produced all year long using MATLAB/Simulink package. Monthly assessments yield that maximum production of 16000 m3/day and 2000 m3/day of fresh water can be produced from the MSF and RO plants respectively in July together with 12.65 MW can be supplied to the grid after meeting all the plant demands.

Tax Incentive Policy for Geothermal Development: A Comparative Analysis in ASEAN

This paper examines tax incentive policies in geothermal industries in ASEAN to better understand the development of geothermal industry investment in the ASEAN Member States (AMS) using a qualitative method. The results indicate that tax incentive policies have supported the investment climate and the development of geothermal industries in the AMS. Geothermal investments and production capacities in AMS have increased significantly. AMS that provide geothermal tax incentives include Indonesia, Lao PDR, the Philippines, Thailand and Vietnam. The performance of geothermal tax incentive policies is reflected in the level of utilization of geothermal potential, which is higher in states that provide greater tax incentives. The results also indicate that geothermal power plants in AMS use dry steam, flash and binary cycle technologies with flash plants being the most common. Results suggest that the future development of geothermal energy in AMS will be related to the tax incentive policy and investment climate in those states. Furthermore, the granting of various types of tax incentives should be focused on the initial investment in geothermal development. ©2020. CBIORE-IJRED. All rights reserved

Intermediate pressure reboiling in geothermal flash plant for increased power production and more effective non-condensable gas abatement

Non-condensable gases (NCG) in condensing geothermal flash plants have negative effects as they reduce heat transfer and thus deteriorate vacuum in condenser. Therefore, it is necessary to evacuate the condenser by vacuum pumps which substantially increases the parasitic load of the plant. Furthermore, NCG consist mostly of CO2 and H2S, gases for which methods of abatement are being searched for. In such case, further compressors or blowers are usually required to push the gas through absorption systems.Alternative methods of NCG separation consider a reboiler upstream of a turbine. This process is however connected with significant loss of steam enthalpy, moreover the NCG in high content have also certain work potential. Therefore, this method is often not considered as very perspective.We are proposing a novel solution where the turbine is split in two parts at high and low pressure. The splitting point is at a pressure right above an ambient pressure, wherein a reboiler is placed. By doing so the NCG stream is easily obtained without energy penalty of vacuum pumps, without decreasing turbine admission parameters, and also utilizes its pressure potential. This stream is thus easily ready for processing and subsequent CO2 separation and conditioning. Condensed water is from large part turned back to steam in the cold side of reboiler which gives further work in low pressure turbine with achievable lower backpressure and therefore potential for higher power production. Another advantage of this method is liquid phase elimination from the turbine thus achieving higher turbine efficiency.

Wellhead Power Plants Improvement by Introduction of Double Flashing Cycle

Kenya Electricity Generating Company Ltd (KenGen) has harnessed geothermal energy for over thirty seven years at the Olkaria geothermal field. The total installed capacity of geothermal energy in Kenya currently stands at 703.5 MW generated mostly by single flash and binary geothermal power plants. In the 1990s KenGen considered the Wellheads concept in which modular containerized single flash power plants were to be designed, customized and built on a wellpad for optimized well potential; this approach has largely been successful currently having an installed capacity of 83.5 MW and accounting for 15.7% of KenGen's total geothermal installed capacity. This was done to address an inherent deficiency in the construction of conventional geothermal power plants which was identified as the long period taken to put up the power plants. The wells that have been drilled by KenGen and GDC, tested and shut in awaiting the installation of power plants are rated at about 600 MW. The Wellhead power plant cycle is a single flash geothermal power plant; this research intended to improve the current Wellheads power cycle by introducing a second low pressure separator to harness more energy from the wellheads, design a turbine to be driven by the low pressure steam and evaluate an economic justification for introducing the double flashing cycle. A case study was carried out at Wellhead 914 and Wellhead 915. Data collected indicated that the combined mass flow rate of brine from wells in the two wellpads was 240.4 tonne per hour. This brine was saturated at 13.5 bar-a and at a temperature of 193.40C as it exits the high pressure separator for disposal. The optimal pressure of the low pressure separation was designed at 2.5 bar-a, 127.40C and had an ability to generate 3871 kW of electric power. A turbine operating at a steam inlet pressure of 2.5 bar-a, a speed of 6804 rpm and having an exhaust pressure of 0.075 bar-a was designed. The designed turbine had 4 stages of both stationary and moving blades with a maximum rotor disc diameter of 0.62 meters and an output of 4195 kW. The simple payback period for this project was estimated to be 1.9 years with a rate of return on investment of 42.24%. This would also minimize energy wastage by improving efficiency and footprints on the environment arising from the Wellhead power plants.

Low emission flash-binary and two-phase binary geothermal power plants with water absorption and reinjection of non-condensable gases

The power production from geothermal resources with a high content of non-condensable gases (NCG) is concerning an increasing number of regions and may affect the sustainability relating to geothermal projects. The selection of an emission abatement system based on water absorption and reinjection of NCG back to the reservoir could solve the environmental impact, yet it implies significant power output penalty and water demand, as demonstrated in a recent paper by the authors (Manente et al., 2019) focused on the retrofit of existing flash steam power stations. A reconsideration of the plant design could result in a better integration with the absorption and reinjection section and finally reduce the associated requirements. To address this point, two “greenfield” plant layouts are investigated in this paper for utilization of a high enthalpy liquid dominated reservoir, where the single flash steam generation unit is complemented or even totally replaced by air cooled binary cycle units. The first layout is an “integrated flash-binary” plant based on a backpressure steam turbine and a bottoming ORC system, whereas the second layout consists in a “two-phase binary” plant. The performance of the two novel layouts is compared against that of a brownfield layout, first proposed in Manente et al. (2019), based on an existing single flash plant retrofitted with the absorption and reinjection system, using a consistent set of assumptions. The results show that the net power output remains almost unaltered because in the novel layouts the lower parasitic loads for gas compression counterbalance the lower production dictated by the air-cooled system and the irreversibility in the heat transfer between geothermal fluid and organic fluid. Thus, due to the better integration between power block and emission abatement section the net power output penalty of the novel layouts is contained within 2%. On the other hand, the hydrogen sulfide and carbon dioxide abatement efficiencies markedly increase as the removal of the cooling tower eliminates the secondary gaseous emissions and makes the entire steam condensate available for NCG absorption. In the integrated flash-binary plant design the overall H2S and CO2 abatement efficiencies reach 99% and 90%, respectively, without any external water demand, provided that measures are taken for a controlled precipitation of silica and other minerals from the geothermal brine prior to using it for NCG absorption.

Working fluid parametric analysis for recuperative supercritical organic Rankine cycles for medium geothermal reservoir temperatures

The conversion efficiency of geothermal energy is very low. For low-temperature resources, such as geothermal energy, a supercritical organic Rankine cycle (ORC) has been shown to be more efficient than an ORC. Recuperative supercritical ORCs have been proven to yield even higher efficiencies for cases where the heat source is limited above the ambient temperature. Most studies on these cycles have focused on turbine inlet temperatures between 80 and 130 °C. Only a few studies have explored other working fluids between 180 and 350 °C but did not analyze optimum turbine inlet pressures. Turbine inlet temperatures ranging from 170 to 240 °C were tested with the heat source provided by a medium temperature geothermal reservoir. A parametric analysis was performed for various turbine inlet pressures and temperatures. Numerous environmental and nontoxic fluids were analyzed. Temperatures and pressures were selected for each tested fluid to achieve the maximum plant efficiency and net work. The best performing binary cycle fluid was R1233zd(E) with a plant efficiency of 16.2% and a second law efficiency of 52.3% for a turbine inlet temperature of 240 °C. This cycle was compared to a single flash plant. The binary cycle plant produced over double the work and had significantly less exergy destruction.

Performance of geothermal power plants (single, dual, and binary) to compensate for LHC-CERN power consumption: comparative study

The aim of this study is to compare between single flash, dual flash, and binary power plants in terms of the power generated, their performance, and the related cost. The results from the comparison are used to find the best plant type that can be implemented to compensate for the very high power requirements of a large hadron collider (LHC). Using the setting and requirements of the CERN LHC in Geneva, Switzerland, the study uses System Advisor Model software to analyze the implementation of the different plant types. Results show that the binary power plant has the best performance and lowest cost compared with other geothermal power plants analyzed, and there is a reduction in the total power generation cost when using renewable energy sources.

Potential performance of environmental friendly application of ORC and Flash technology in geothermal power plants

The successful exploitation of geothermal energy for power production relies on to the availability of nearly zero emission and efficient technologies, able to provide flexible operation. It can be realized with the binary cycle technology. It consists of a closed power cycle coupled to a closed geothermal loop, whereby the closed power cycle is generally accomplished by means of an organic Rankine cycle (in a few cases the Kalina cycle has been adopted). The confinement of the geothermal fluid in a closed loop is an important advantage from the environmental point of view: possible pollutants contained in the geothermal fluid are not released into the ambient and are directly reinjected underground.Although a well-established technology in the frame of geothermal applications, the adoption of the binary cycle technology is at the moment typically confined to the exploitation of medium-low temperature liquid geothermal reservoirs, generally between 100-170 °C. The important advantages of the binary cycle technology from the environmental point of view suggest nevertheless that it is worthwhile to investigate whether the application range could be extended to higher temperature reservoirs, and up to which extent. Moreover, the paper investigates the effect of an increasing CO2 content in the geothermal fluid. The paper compares in a convenient high temperature range of the geothermal source the performance of a properly optimized geothermal ORC plant, with the performance of a modified flash plant, whereby the geothermal steam enters a turbine, and the CO2 stream is separated, compressed and finally reinjected. An environmentally friendly working fluid, recently introduced in the market, is considered in the ORC optimization process. The performance comparison will involve the assessment of plant net power. As far as the calculations are concerned, the geothermal fluid is assumed to be a mixture of water and possibly CO2. The auxiliary power consumption is properly accounted for: beyond cooling auxiliaries, a submersible well pump for the ORC plant and a gas compressor for the reinjection of the non-condensable gases in the flash plant are considered.

Zero Emission Geothermal Flash Power Plant

The successful exploitation of geothermal energy for power production relies on the availability of nearly zero emission and efficient technologies. Two zero emission flash plant layouts, with full reinjection of the geothermal fluid (non-condensable gas included), are considered. This paper focusses on the CO2 issue, and therefore only the carbon dioxide is considered as non-condensable gas present in the geothermal fluid; the CO2 flow is separated, compressed, and reinjected with the geothermal fluid. Both the reservoir and the power plant are simulated. A first scheme of plant presents a conventional layout in which the CO2 is separated and compressed after the condenser. The second scheme presents a plant layout that allows the separation of the CO2 at higher pressure with respect to the conventional layout, thus reducing the requested power consumption.The conventional plant scheme performs always better at higher temperature and at lower concentration of CO2. The new layout results better for low temperature and higher gas content.

A tool for evaluating geothermal power exploitability and its application to Ischia, Southern Italy

The paper proposes a method to evaluate the potential for electric power production at any site of possible geothermal interest. Accounting for geological data of the reservoirs, the method allows the computation of the available electrical power of the investigated site. Electrical energy production from geothermal sources is realized through different techniques, such as single flash and double flash, dry steam, and binary ORC plants. The technique chosen to be the most productive is determined by analyzing a specific range of geofluid properties, mainly temperature and pressure. Moreover, each plant typology has a global efficiency that may be correlated to geofluid enthalpy by empiric relations available in literature. The proposed evaluation method brings together all these correlations, yielding the power availability from a geosource, once its temperature and pressure are known. The method takes as input the geofluid available flow rate, its pressure, temperature and non-condensable gas content. It defines the best plant option from these parameters, calculates its global efficiency and finally returns the actual available power. For sites of geothermic interest, such as the volcanic island of Ischia in Southern Italy, the results of the application of this new method clearly highlight the most suitable zones for power plants installations.

Life cycle greenhouse gas emissions from geothermal electricity production

A life cycle analysis (LCA) is presented for greenhouse gas (GHG) emissions and fossil energy use associated with geothermal electricity production with a special focus on operational GHG emissions from hydrothermal flash and dry steam plants. The analysis includes results for both the plant and fuel cycle components of the total life cycle. The impact of recent changes to California's GHG reporting protocol for GHG emissions are discussed by comparing emission rate metrics derived from post and pre revision data sets. These metrics are running capacity weighted average GHG emission rates (g/kWh) and emission rate cumulative distribution functions. To complete our life cycle analysis, plant cycle results were extracted from our previous work and added to fuel cycle results. The resulting life cycle fossil energy and greenhouse gas emissions values are compared among a range of fossil, nuclear, and renewable power technologies, including geothermal.

Cumulative energy, emissions, and water consumption for geothermal electric power production

A life cycle analysis has been conducted on geothermal electricity generation. The technologies covered in the study include flash, binary, enhanced geothermal systems (EGS), and coproduced gas and electricity plants. The life cycle performance metrics quantified in the study include materials, water, and energy use, and greenhouse gas (GHG) emissions. The life cycle stages taken into account were the plant and fuel cycle stages, the latter of which includes fuel production and fuel use (operational). The plant cycle includes the construction of the plant, wells, and above ground piping and the production of the materials that comprise those systems. With the exception of geothermal flash plants, GHG emissions from the plant cycle are generally small and the only such emissions from geothermal plants. Some operational GHGs arise from flash plants, and though substantial when compared to other geothermal power plants, these are nonetheless considerably smaller than those emitted from fossil fuel fired plants. For operational geothermal emissions, an emission rate (g/kW h) distribution function vs. cumulative capacity was developed using California plant data. Substantial GHG emissions arise from coproduced facilities and two other “renewable” power plants, but these are almost totally due to the production and use of natural gas and biofuels. Nonetheless, those GHGs are still much less than those from fossil fuel fired plants. Though significant amounts of water are consumed for plant and well construction, especially for well field stimulation of EGS plants, they are small in comparison to estimated water consumed during plant operation. This also applies to air cooled plants, which nominally should consume no water during operation. Considering that geothermal operational water use data are scarce, our estimates show the lowest water consumption for flash and coproduced plants and the highest for EGS, though the latter must be considered provisional due to the absence of field data. The EGS estimate was based on binary plant data.

Simulation of a giant MSF recirculation plants

ABSTRACT This study describes the mathematical model that used for the prediction of the performance of the multi-stage flash plant (MSF) systems under steady state conditions. The developed model based on the mass, heat, and energy balance. The governing equations describe the behavior of temperatures, brine, and product streams within the flashing stage. The losses, densities, enthalpies, and other properties are (accounted) for the model. This model consists of sets of algebraic equations. The proposed model was validated by another data from previous models and by an actual data from existing plants. This model focuses on the evaluation of flow rate and temperatures profile. This model can be used for small and large capacity plants that vary in the range of 5,000–77,760 m3/d. Through this study, both the specific heat transfer area and the weir load vary in the range of 175–300 m2/kg/s and 150–310 kg/s/m, respectively, also the stage width varies up to 25 m and the stage length varies in the range of...