Substitute 0 for in Equation 1 to get the reduced energy balance for flash chamber,. Here, enthalpy of steam at initial and final state is respectively.
Comment 0. Chapter , Problem is solved. View a sample solution. During the past few years, great attention has been paid to the use of waste heat and renewable energy due to their contribution towards reducing the reliance on fossil fuels. Moreover, there is a great demand for energy worldwide Sheng et al. Renewable energy is becoming an important source of energy for the industry. The use of renewable energy does not contribute to gas emissions that harm the environment at the same level as emissions from fossil fuels.
One of the most readily available renewable energy sources is geothermal energy which is stored within the Earth all over the globe at varying depths according to location. This new source of available energy is environmentally safe as it has fewer harmful effects than traditional energy sources that rely on fossil fuels Lurque et al. The depletion of the fossil fuel reserves calls for more sources of sustainable energies such as geothermal, wind, solar, and tidal energy.
As a result of this need, a new device for tidal energy conversion was tested El Haj Assad et al. The conversion of geothermal energy into electrical energy is neither a cheap nor a simple process so there is a real need to use the available energy in an efficient way.
As of today, there are three different types of geothermal power plants which are 1 the flash steam, 2 the dry steam, and 3 the binary ORC Organic Rankine Cycle geothermal power plant DiPippo Building these power plants depends on the geothermal resources which are classified accordingly as having low enthalpy, medium enthalpy, or high enthalpy Dickson and Fanelli In dry steam reservoirs, the dry steam is obtained by digging wells that are —10, feet deep, after which the steam is transported through pipe from the well to the turbine generator in order to generate electricity.
Moreover, the condensed water from the turbine can be used to cool the power plants. Using dry steam reservoirs is an efficient and successful way of generating electricity, but it is rarely used.
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As for hot water reservoirs, the hot water from the wells is connected to one, two, or more separators to convert the water into steam. This steam then flows through pipes towards the turbine to produce electricity, after which the steam is condensed and used to cool the power plant system. This type is more common than the previously described dry steam reservoirs.
In a single flash steam power plant, the geothermal fluid is in liquid state Ameri et al. This mixture of liquid and vapor is directed to a separator kept at a constant temperature and pressure, so that the liquid and the vapor are separated from each other. The produced vapor is directed to the steam turbine to generate electricity while the remaining liquid is re-injected to a re-injection well.
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The double flash steam power plant has the same working principles as the single flash power plant except that in the former, two separators are used which result in both high- and low-pressure steam flows that run the steam turbine. Double flash geothermal power plants produce a higher power output than single flash geothermal power plants but at a higher cost. The cost of the dual flash is higher than the single flash due to the use of more piping, a second separator, and low- and high-pressure steam turbines. To compensate for the high cost of a double flash power plant, an exergy analysis has been used as an effective tool to maximize the power output and hence improve the efficiency of the double flash power plant Ameri et al.
In a binary geothermal power plant ORC , the hot geothermal fluid is directed to a heat exchanger vaporizer where a secondary fluid of low boiling point and high vapor pressure circulates. The heat exchange process between the geothermal fluid and the secondary fluid causes the secondary fluid to vaporize and this generated vapor is then used to run the turbine in order to produce electricity. Due to the importance of ORC, recently many investigations have been conducted to evaluate the performance of the ORC power plant by using different mixtures of the secondary fluid in the Rankine cycle part of the geothermal power plant Bao and Zhao ; Garg et al.
Recently, second law analysis has been applied to evaluate the thermal performance of a suggested ORC-OFC combined geothermal power plant Jianyong et al. A second law analysis of combined Flash-ORC power plant has been applied to determine the power output and the efficiency of the power plant Gong et al. Negawo reviewed some geomaterial aspects of geothermal energy to show and discuss the role of geomaterials on the utilization of geothermal energy.
Modeling of these systems helps in anticipating the amount of power generated and the cost as a function of geothermal system parameters such as temperature, depth, and pressure along with many other parameters. This study was carried out based on the built-in location parameters for Geneva in Switzerland Vuataz at a time when countries such as Pakistan Younas et al. The geothermal source available under the ground of Geneva is hydrothermal resource. Hydrothermal resources mean that the fluid can be in vapor form as found in steam reservoirs or it can be at a high temperature as found in deep underground hot water which keeps the surface that comes in contact with it constantly hot.
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There are different ways to use hydrothermal resources depending on the temperature of the fluid and its depth. If the temperature of the hydrothermal resource is low, it can be used directly to heat buildings or warm swimming pools in addition to other similar uses. Such use of hydrothermal resources is referred to as direct use. On the other hand, if the temperature of the hydrothermal resource is high, it may be used to produce electricity Yari Two types of hydrothermal resources that can be used to produce electricity are 1 a vapor form source known as dry steam reservoirs , and 2 a liquid form source known as hot water reservoirs.
Geothermal power plants mainly come in two groups, namely, steam and binary power cycles. These cycles operate at high geothermal fluid enthalpy. The single flash cycle contains only one throttling valve expansion valve through which the geothermal fluid is expanded, and one separator to separate the vapor from the liquid after the expansion process in the expansion valve.
This separation occurs at constant pressure and temperature. The vapor generated is sent to a steam turbine to produce electricity while the liquid is re-injected back to the ground. Flash steam power plants use a condenser to condense the steam leaving the turbine and then re-inject it into the ground.
The benefit of such a power plant is that the geothermal fluid is circulated in a closed loop so as not to produce any harm to the environment. However, this cycle needs a secondary fluid which is heated by the geothermal fluid in the heat exchanger vaporizer where it eventually vaporizes following which it gets sent to the turbine for electricity production. Single flash power plant Valdimarsson Single flash power plants are classified according to their steam turbines types, i. Two such basic types are the single flash with a condensation system and the single flash back pressure system.
In the first type, a condenser operating at very low pressure is used to condensate the steam leaving the steam turbine. The condenser should operate at low vacuum pressure to maintain a large enthalpy difference across the expansion process of the steam turbine, hence resulting in a higher power output.
The geothermal fluid usually contains non-condensable gases which are collected at the condenser. Such a collection of gases may raise the condenser pressure, therefore the gases should be removed from the condenser. This can be achieved by installing vacuum pumps, compressors, or steam ejectors. The condenser heat removal is done either by using a cooling tower or through cold air circulation in the condenser.
The condensate forms a small fraction of the cooling water circuit, a large portion of which is then evaporated and dispersed into the atmosphere by the cooling tower. The cooling water surplus blow down is disposed of in shallow injection wells. In single flash condensation system, the condensate does have direct contact with the cooling water. Dual flash power plant Valdimarsson Following the steam production at high and low pressures, all steam gets directed to a steam turbine using separate pipelines.
The steam turbine can be a dual admission turbine, a separate turbine, or may be made up of two separate tandem compound turbines which operate based on the steam inlet pressure. The components of a dual flash power plant are similar to those of a single flash steam power plant.
The mineral content of the water becomes concentrated depending on how the dual flash is designed, hence the resource conditions are of extreme importance. Binary flash power plant Valdimarsson A binary power plant has several advantages such as reservoir sustainability, high reliability operation, and environmental friendliness. In our study, we used Isopentane as the secondary working fluid. The main advantages of ORC are that it operates at a low temperature which results in low-mechanical stresses on the turbine, along with the fact that there is no erosion of the turbine blades due to the absence of moisture during the vapor expansion in the turbine.
Geothermal Power Plants
Moreover, the turbine in ORC has a smaller size so it is consequently less expensive, and there are no air in-leakage problems nor problems due to operating in a vacuum, since a vacuum is not needed DiPippo It is a software that can be used by engineers, researchers, and project managers alike who are involved in the renewable energy industry. Moreover, SAM estimates the energy cost of the geothermal power plant project based on the results obtained from the performance model over the whole project life-cycle. Annual, monthly, and hourly electric power output, LCOE levelized cost of energy , revenue, and power factor.
Steps 1 and 2 are used to obtain the energy production. Using steps 3, 4, 5, and 6, SAM estimates the parameters of step 7. Calculated recapitalization cost includes drilling costs, pump costs, and surface equipment. When the reservoir temperature drops below an allowed minimum, new wells must be drilled and costs accounted for in the out years of the analysis. The working fluid used in this study is Isopentane. No other parameters are required for the performance model of SAM. Pump costs are estimated based on the depth and size of the pump.
The table shows the total installed cost which is obtained by summing up the total direct and indirect capital costs specified by the user. The indirect capital cost consists of three different costs presented as a percentage of the direct cost as given in the table.
Annual energy production versus percentage contribution of geothermal energy to the total energy demand. Power factor versus percentage contribution of geothermal energy to the total energy demand. Cost versus percentage contribution of geothermal energy to the total energy demand. This work presented a comparative study between three geothermal power plants using SAM.
SAM first estimates the electric power production performance model and then estimates the energy cost based on a performance model, or more precisely, on a combination of performance and finance models. The comparison is based on the electric power production and energy costs related to the power plant. The annual energy produced by the binary is the highest and its power factor is the highest as well. This type of geothermal power plant offers a cost reduction of Authors agree on the names arrangement given in the manuscript title page.
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Authors Authors and affiliations M. El Haj Assad E. Bani-Hani M. Open Access. First Online: 15 September Background During the past few years, great attention has been paid to the use of waste heat and renewable energy due to their contribution towards reducing the reliance on fossil fuels. The use of a flash system results in the elimination of a large portion of energy in brine liquid form from the separator due to the low steam quality that emanates from the two-phase fluid following the expansion valve.
Higher temperature resources will produce more liquid and steam for natural pressure conditions.