ADVANCED BINARY CYCLES: OPTIMUM WORKING FLUIDSSignificant savings in the cost of power production can be achieved if Propane mixtures are favoured at the low end of the range of resources and isobutene mixtures at the high end, are used in binary plants.ADVANCED ORGANIC RANKINE CYCLES IN BINARY GEOTHERMAL POWER PLANTSImprovement in efficiency takes place with a mixture of more than one fluid.ADVANTAGES OF USING MIXTURES AS WORKING FLUIDS IN GEOTHERMAL BINARY CYCLES

Mixtures used as working fluids in binary cycle increases turbine work and decrease condenser duty and cooling water requirementsAN ECONOMIC EVALUATION OF BINARY CYCLE GEOTHERMAL ELECTRICITY PRODUCTIONHigh flow rates may be more desirable than high temperatures when selecting a site for binary cycle geothermal power plant construction because payback periods and breakeven sales rates were nearly identical for all geothermal gradients evaluated at the high flow rate.AN IMPROVED HYBRID AND COGENERATION CYCLE FOR ENHANCED GEOTHERMAL SYSTEMSThe hybrid system performs higher efficiency than conventional geothermal cycle. R-600 is a best working fluid to achieve highest thermodynamic performance in the proposed hybrid system. BINARY POWER PLANT MODELLING AND SENSITIVITY ANALYSIS FOR ELECTRICITY GENERATION FROM AN ENHANCED GEOTHERMAL SYSTEM1) Wet cooling options for plant heat rejection are better from a performance and capital cost perspective compared to dry cooling. However the operational cost, environmental impact, proximity to plant and security of supply need to be considered.

2) At present in an EGS setting a power development appears to be economically marginal.COMPARATIVE ANALYSIS OF POWER PLANT OPTIONS FOR ENHANCED GEOTHERMAL SYSTEMS (EGS)Flash type power plants have utilization efficiency ranging from 30% to 60% for geofluid temperature between 200 and 350C while expansion plants could achieve a utilization efficiency higher than 70% when fed with supercritical geofluid. The utilization efficiencies are around 70% for all supercritical fed geofluid temperatures. The energy efficiency of flash type plants ranges from 13% to 23% while ranges from 30% to 37% for expansion type plants. The exergy efficiency of flash type and expansion type plants are 40% to 55% and 70% to 75% respectively.

For supercritical feed geofluid, the analysis shows that lower geofluid feed pressure results in higher GFe, so the geofluid pressure should be kept as low as possible as long as it is in supercritical state. Comparison of air-cooled system with water-cooled system indicates that water-cooled systems could increase geofluid effectiveness GFe by 1.32%5.43% and decrease the specific embodied energy by 62.10%70.26%.

ENERGY, EXERGY AND THERMOECONOMIC ANALYSIS OF LAHENDONG BINARY CYCLE GEOTHERMAL POWER PLANT AT NORTH SULAWESI INDONESIA

Analysis shows that total capital investment cost of Lahendong binary-cycle power plant is about 1850 $/kW, and levelized annual cost of electricity is around 5.8 /kWh. FEASIBILITY STUDY OF BINARY GEOTHERMAL POWER PLANTS IN EASTERN SLOVAKIAKalina cycle has higher power output by utilizing less energy from the geothermal source.The difference between ORC and Kalina in terms of power output is 1 MWe. Kalina is able to produce 5 MWe power and ORC approximately 4 MWe power.

Inlet temperatures in these models are quite low and because of this high power outputs cannot be expected, but using binary power plants helps to increase the power output.It is just a question for investors Which of the modelled binary plants is more cost effective for them. The one with higher cost but higher power output and utilization of hot water (Kalina)? Or low coast and lower power output and additional water for heating purposes (Organic Rankine Cycle). Will they invest in a power plant that has been operating all over the world for more than 30 years or if they will put their trust into the system which is still under the development.GEOTHERMAL BINARY CYCLE POWER PLANT PRINCIPLES, OPERATION AND MAINTENANCEThe production of electricity from binary cycle power plants is useful for harnessing low and medium temperature resources and raising the total exploitable geothermal potential worldwide. The concept of a binary cycle power plant, known as an organic Rankine Cycle (ORC), is a modification of the Rankine cycle where the working fluid, instead of water, is an organic fluid having a lower boiling point and a higher vapour pressure than water.

The overall economic conclusion can be drawn that when the recuperator is added, the total plant cost is higher. As the basic binary cycle has a lower cost, in general, this option is the best when no constraints exist.

When the reinjection temperature is in the range of 80C to 160C, according to this research Isopentane and n-Pentane are the most suitable working fluids

The maintenance of binary cycle power plants is highly influenced by different factors such as: the nature of the geothermal fluid used in the primary loop, the nature of the working fluid, the technology and location of the plant, climate and weather. To develop the maintenance activities, it is necessary to have a maintenance management programme to help in coordination, control, planning, implementing and monitoring the necessary activities required for each component of the binary plant.GEOTHERMAL JAPANWith over 500 MW of generation capacity, Japan is the worlds sixth largest producer of electricity from geothermal energy resources. In addition, Japan has been an important player in providing input to international geothermal technical information exchange, including cooperative programs related to geothermal energy development.With limited energy resources, Japan must further develop its abundant geothermal potential. To do so, it will be necessary to gain new governmental support, as well as craft a new, long range plan for development that emphasizes economics, conservation of nature, and cooperation with local communities and the countrys many national parks.HOW GEOTHERMAL POWER PLANTS HELP TO REDUCE CO2 EMISSIONGeothermal power generation is an excellent power generation method with the following features: Low CO2 emission, and environment-friendly

High availability factor Runs on an energy resource thats hard to deplete

GEOTHERMAL ENERGYOverall, the geothermal-electric market appears to be accelerating compared to previous years, as indicated by the increase in installed and planned power capacity. The gradual introduction of new technology improvements, including EGS, is expected to boost the deployment, which could reach 140 to 160 GWe by 2050 if certain conditions are met. Power generation with binary plants permits the possibility of producing electricity in countries that have no high-temperature resources.With its natural thermal storage capacity, geothermal is especially suitable for supplying base-load power. Considering its technical potential and possible deployment, geothermal energy could meet roughly 3% of global electricity demand by 2050, and also has the potential to provide roughly 5% of the global demand for heating and cooling by 2050.LIFE-CYCLE ANALYSIS RESULTS OF GEOTHERMAL SYSTEMS IN COMPARISON TO OTHER POWER SYSTEMS

A process-based life cycle energy and greenhouse gas emissions analysis was conducted for geothermal power-generating technologies, including enhanced geothermal systems, hydrothermal flash, and hydrothermal binary. Results from the analysis were compared to those from other electricity-generating technologies including coal, natural gas combined cycle, nuclear, hydroelectric, wind, photovoltaic, and biomass. Because of a scarcity of geothermal life cycle data, a scenario analysis approach was chosen for conducting this assessment. Because of the significant amounts of additional materials and construction energy required for drilling and constructing geothermal wells, a special emphasis has been placed on determining the contribution of the plant construction stage, termed herein the infrastructure stage (or plant cycle), of the life cycle to total energy consumption and carbon emissions for not only geothermal technologies but also the other power-generating technologies covered herein. Data for the plant cycle required for the LCA of the non-geothermal technologies included in this study were extracted from the literature.

From both our literature review and geothermal modeling, tables of material and energy requirements to build the various electricity-generating technologies were compiled. Further, the operational requirements and the energy required to provide them were also gathered for these technologies. It was found that the mass-to-power ratios (MPR in tonnes/MW) for materials such as the steel and concrete required to build and equip a power plant are the lowest for the conventional power systems (i.e., the thermoelectric systems), including coal, natural gas combined cycle, and nuclear. Biomass-to-power, a thermoelectric renewable system, shows the same material dependence. Other materials like copper and aluminium were tracked but are used in considerably smaller amounts in the conventional power systems. Renewable systems generally required more steel and concrete per MW capacity than do conventional systems. This finding is especially true for EGS and hydrothermal binary plants, a consequence which is attributed to the need for deeper wells and air-cooled condenser systems for the binary plants. Temperature of the resource also plays a role. For a given power output, a greater geofluid flow is required for lower-temperature resources, thus necessitating that more wells be built and hence, use of more cement and casings.

Further, the concrete MPR for gravity dams is (not surprisingly) quite high, and the steel and concrete MPRs for wind turbines are roughly two to five times higher than those of conventional systems. For some of the renewable systems, the aluminium MPR is much higher than it is for conventional systems. This result occurs because of the aluminium frames for photovoltaic arrays and heat-exchanger fins that are needed for the large air coolers in binary geothermal power systems.

Energy and GHG ratios for the infrastructure and other life cycle stages were also developed in this study to develop results for service functional unit (i.e., kWh). Energy burdens per energy output associated with plant infrastructure typically range from 2% to 6% for renewable power technologies, although PV can be as high as 50%. For conventional systems, the energy burden ranges from 0.1% to 0.3%. GHG emissions per energy output for plant construction follow a similar trend.Total GHG emissions are by far the largest for fossil power plants and are much lower for the renewable power systems. GHG emissions that exist for renewable systems tend to be dominated by plant construction, although flash geothermal emissions are primarily attributable to fugitive GHGs from the geofluid during the plant operation stage of the life cycle. The GHG emissions for biomass plants are dominated by the fuel production life cycle stage. Despite the large amounts of steel and concrete required per MW power capacity, enhanced geothermal systems are one of the lower GHG emitters of the renewable systems studied per unit of lifetime kWh output. EGS GHG emissions can be reduced even further as well depth decreases. When compared to GHG emissions values from other studies, GREET model results are in good accord with them overall. The two outliers noted are readily explained on the basis of different fuel properties assumed. Relative variation among GHG study results is larger for power-generating technologies where plant-cycle burdens dominate.

Finally, the capability of the GREET model to provide rich energy detail for power generation from various technologies has been demonstrated. Further, the capability of the model has been expanded. The GREET model already contains modules for conventional and some renewable electric power-generating systems. Energy and GHG results developed for this study were developed by using GREETs existing modules and new prototype modules. As a result of this study, the model has been updated to include several new power-generating technologies, including enhanced geothermal, hydrothermal flash, and hydrothermal binary. Furthermore, through this study, the GREET model was expanded to include plant cycle, as well as fuel cycle, for life-cycle analysis of electric power generation systems.LIFE CYCLE ASSESSMENT OF GEOTHERMAL BINARY POWER PLANTS USING ENHANCED LOW TEMPERATURE RESERVOIRSThis paper evaluates greenhouse gas emissions, consumption of finite energy resources and SO2- and PO -equivalent emissions during the life cycle of geothermal binary power plants. The results show that geothermal binary power plants cannot be described by representative environmental key figures due to the wide range of geological site preconditions, different plant set-ups and data uncertainties, which are typical for theoretical evaluations of complex technical concepts not yet established on the market. Based on the results general conclusions, however, can be drawn:

The life cycle of geothermal binary power plants is characterized by large material and energy inputs, especially during construction of the subsurface plant part. Successful exploration and access to the reservoir with minimum drilling and completion efforts referring to a specific site is hence the precondition for low environmental impacts. Due to the large influence of the auxiliary power required for delivering the geothermal fluid from the reservoir on the net power output, a sufficient reservoir productivity is required in order to make up for the large material and energy inputs during construction. The enhancement of the reservoir productivity by means of technical measures is, therefore, a key aspect for the improvement of the environmental performance of geothermal binary power plants. The surface plant part is determining for the efficient use of the geothermal heat. Regarding an optimum net power output at a specific site, not only high conversion efficiency of the binary power unit but also low auxiliary power for re-cooling are important factors for the environmental performance.

Geothermal binary plants offer a large potential to provide power and heat from the same plant, and the supply of district heat significantly improves the environmental key factors. The possibility to supply heat is, however, based on an adequate heat customer structure that needs to be developed at the beginning of a geothermal power plant project.Comparing geothermal binary power plants to the environmental key figures of a reference electricity and a reference heat mix shows that sites with above average and average conditions have significantly lower emissions of CO2-equivalent pollutants, a significantly lower consumption of finite energy resources and lower SO2-equivalent emissions. PO4- equivalent emissions are significantly lower only at sites with above average geological conditions. For typical sites, assured conclusions regarding PO4-equivalent emissions can only be drawn after further investigations due to uncertainties with the used life cycle data base.

Less favourable geothermal sites can also be realized with greenhouse gas emissions and consumption of finite energy resources that are significantly below the values of the reference mix. The precondition is adequate design of the surface facilities (i.e. high-efficiency technology and continuous supply of district heat). Referring to SO2- and also PO - equivalent emissions, lower impacts cannot always be achieved at these sites so that a detailed and site-specific environmental analysis including all relevant options of energy supply must be carried out for proper decision making.If the aspects addressed above are taken into consideration, geothermal heat and power generation from low-temperature resources can make a large contribution to a more sustainable energy system today and in the future.MAGIC AT MAGUARICHICWith experience gained at Maguarichic, CFE has learned a number of answers to technical and economic questions that will be taken into account for similar, future projects in Mexico.Regarding the geothermal reservoir: The aquifer to be exploited should be located preferably at depths of 500 m or less, so wells can be drilled with a small rig. To acquire reservoir information, it is better to drill a production well instead of a slim hole. Costs are almost the same, but a slim hole probably cannot exploit a reservoir because of its inability to accept a downhole pump. Minimal reservoir temperature should be 115-120C. Lower temperatures increase water needs, demanding more than one well to supply the required flow. In addition, the size of the heat exchanger must be greater. Optimum flow rate for a 300-kW binary unit is 150 t/h.

Regarding the power plant: Binary equipment should be designed with different working fluid. Handling isopentane at an isolated rural area is very difficult because it is considered dangerous material. To replace leaked fluid (around 7% per year), it is necessary to rent a special transport vehicle that costs more than the fluid ($5,000 [US] for the vehicle compared to $2,500 for the isopentane). The plant should be designed to operate within a 120-135C range for brine inlet pressure. This range covers several site conditions for operation without problems. The Maguarichic power plant was designed for an inlet temperature of 150C, but available geothermal fluids are only 120C. By increasing the flow rate, the plant can produce 200 kW output, but will never reach the equipments rated 300 Kw.

The generation skid must be designed in a modular fashion, with a maximum weight of 15 tons per module. Heavier modules must be disassembled to transport them on a rough, steep roads. The heat exchanger should be designed for a maximum length of 9 meters, to avoid transportation problems. The main isopentane pump should be horizontal instead vertical, to reduce civil works. The assembly between the turbine and the generator should be direct instead of through a gearbox, which is noisy and demands maintenance. Power capacity should be higher than electrical consumption, in order to support a consumption increase. Too large of a difference between power capacity and consumption in the initial stages of a project can make it uneconomical. Too small a difference between capacity and consumption can also constrain desired economic development associated with electricity generation.

Regarding the economy of the project: Power plant operation and maintenance activities are handled by three people from Maguarichic. Operational costs were less than $8,000 (US) during the first year. CFE spent a similar amount for supervisory work. During the first year of power plant operation, each household paid an average $4 (US) per month for its electric consumption, since the village people cannot afford the electricitys actual cost. Local authorities helped by paying salaries of the three power plant workers. In developing countries, this type of rural electrification project must be financed by government agencies, but the community must also be involved and support at least a small share of costs.MODEL OF BINARY CYCLE POWER PLANT USING BRINE AS THERMAL ENERGY SOURCES AND DEVELOPMENT POTENTIAL IN SIBAYAKDesign and performance test of the 2 KW binary cycle geothermal power plant have been accomplished. Regarding the experimental result shown in Table 5 and the preliminary design of binary plant in Sibayak shown in Table 6, the important things that can be inferred from this study can be summarized as follows: Binary cycle power plant can be applied using relatively low enthalpy heat sources. The methods for designing the equipments have been proven to be accurate. Sibayak have a development potential for binary cycle power plant.OPTIMAL DESIGN OF BINARY CYCLE POWER PLANTS FOR WATER-DOMINATED, MEDIUM TEMPERATURE GEOTHERMAL FIELDSBinary plants with dry cooling systems represent a sustainable way to exploit low temperature, water-dominated geothermal fields. No additional water is required and emissions of pollutants and greenhouse gases are close to zero.

However, it is clear that geothermal binary plants can be competitive with other energy conversion technologies if and only if acceptable brine consumption levels (kg/s per net MWe generated) can be attained. Optimal design strategies that give the best match between the geothermal resource and the power plant are required. This involves the selection of a suitable working fluid for the thermodynamic cycle and a detailed design of the plant components like the recovery heat exchanger and the cooling systems.

In this paper, a hierarchical optimization procedure for the design of binary plants has been presented and applied to a range of representative cases. A sensitivity analysis taking into account different geothermal fluid (110-160C), rejection (70-100C) and condensation (30- 40C) temperatures, as well as various working fluids and thermodynamic cycles was presented. A study of the results permits some guidelines to be developed for the optimal matching of lower-temperature geothermal fluids and binary power plants, i.e.:

Brine specific consumption to produce electrical power is mainly influenced by the difference between the source and rejection temperatures (Tgeo Trej). For the range of source temperatures analysed (110160C) it can vary from 20 to 120 kg/s per MW net. It is between 20 and 24 kg/s per MW net when the operating conditions are favorable (160-70-30) and increases to 40-50 kg/s per MWe for a lower temperature source and a higher temperature condenser (130-70-40). If the temperature difference (Tgeo Trej) is further reduced (e.g. 130-100; 110-80), it may not be practical to generate power. In all cases the optimal matching of organic fluids, recovery cycle and condensation temperature is of fundamental importance; The values of First and Second Law efficiencies calculated for the basic Rankine cycle, as well as the values of brine specific consumption, are similar to those found in the literature; their variation is due primarily to differences between source and rejection temperatures. In particular, First Law efficiencies between 6% (110-80-40) and 12% (160-70-30) can be obtained, while Second Law efficiencies are between 22% (110-80-40) and 45% (160-70-30). Optimization of the energy conversion cycle can produce a reduction in brine specific consumption of up to 30%. For each combination of geothermal fluid temperature and working fluids, there is a particular recovery cycle that permits maximization of the thermodynamic performance of the system. The important point is that the optimal design for each working fluid leads to a similar performance if one finds the best match between the working fluid, the recovery cycle and the geothermal brine. The best results are obtained with R152a and Isobutane, while there are no apparent advantages in the use of multicomponent fluids for the range of conditions studied. Particular attention must be paid to the condensation temperature. While a reduction in ambient temperature is beneficial, the optimal condenser temperature is not necessarily the lowest one. There is a range of 10 to 20C above the average ambient temperature over which no beneficial effects are obtained by reducing the condensation temperature. This is because the higher thermodynamic performance of the recovery cycle is negated by the increase in fan power requirements. In some cases the advantages related to the use of complex technical solutions (e.g. supercritical, dual pressure level cycles or recuperative cycles) may be important (5-10% in terms of a decrease in brine specific consumption), but not always. In particular the advantages are greater if a higher geothermal fluid inlet temperature (140-160C) can be used, while they are negligible if only relatively low inlet temperatures (120-130C) are available. However, the real problem of the advanced recovery cycles is their high sensitivity to variations in operating conditions (e.g. a decrease in geothermal fluid inlet temperature during the life cycle of the plant).In conclusion, binary cycle technologies are promising because they permit the utilization of geothermal resources that could not otherwise be used to generate electricity economically. To exploit low- and medium-temperature geothermal sources on a wider scale, it is crucial to use advanced design methods and apply optimization techniques for fine-tuning plant design variables. This is because the results obtained are very sensitive, from both energetic and economic points of view, as well as to variations in design parameters. Finally, it must be emphasized that binary plant technology cannot be considered in isolation from the geological aspects (depth of the reservoir, chemical composition of the geothermal fluid, sustainability of brine production). For the utilization of any geothermal resource a multidisciplinary research approach is of fundamental importance.ORC-BASED GEOTHERMAL POWER GENERATION AND CO2-BASED EGS FOR COMBINED GREEN POWER GENERATION AND CO2 SEQUESTRATIONAn increasing concern of environmental issues of emissions & pollution, in particular global warming and the constraints on consuming conventional energy sources has recently resulted in extensive research into innovative renewable and green technologies of generating electrical power. One of these innovative emerging technologies includes renewable low temperature (low-enthalpy) geothermal energy source for clean electrical power generation. This promising technology offers potential applications in generation of electric power which can be produced using the vast renewable low-temperature geothermal energy resources available worldwide. In this chapter, the concept of ORC binary technology for power generation using low-temperature geothermal heat source was introduced and its potential applications and limitations for small-scale geothermal power generation and its relevant environmental and economic considerations were presented and discussed. Also, recent developments of ORC-based low-temperature geothermal power generation with their significant and relevant applications were presented and discussed. A number of successful ORC binary plants were installed in different locations (e.g. remote and rural sites) worldwide which demonstrated the ability of this promising alternative and green technology to utilize renewable low-temperature geothermal energy sources for generating electricity. Also, several patents were reported on the application of this innovative technology. Geothermal ORC power generation plants are normally constructed and installed in small modular power generation units. These units can then be linked up to create power plants with larger power production rates. Their cost depends on a number of factors, but mainly on the temperature of the geothermal fluid produced, which influences the size of the ORC turbine, heat exchangers and cooling system. Currently, ORC power cycles exhibit great flexibility, high safety (installations are perfectly tight), and low maintenance when coupled with low-enthalpy geothermal heat sources. The future use of low-temperature geothermal energy resources for generating electricity would very much depend on further overcoming technical barriers both in utilization and production, and its economic viability compared to other conventional and renewable energy sources used for power production. Another emerging dual-benefit technology is EGS using CO2 as the working fluid for combined clean power generation and geologic CO2 sequestration. CO2 is of interest as a geothermal working fluid mainly because it transfers geothermal heat more efficiently than water. While power can be produced more efficiently using this technology, there is an additional benefit CCS for reducing GHG emissions. The second part of the chapter presented the merits and fundamental aspects of CO2-based EGS technology. In 2000, Brown, D. (Pruess, 2006) proposed a novel EGS concept that would utilize supercritical CO2 instead of water as a more efficient heat exchange (carrier) fluid (due to its favorable properties over water), and would simultaneously achieve CO2 geologic sequestration as an additional benefit. It was found that CO2 is superior to water in its ability to exchange heat from EGS hot fractured rock and reduce hydraulic power consumption for fluid injection and circulation in the EGS reservoir. It was concluded that an EGS system running on CO2 has sufficiently attractive features to warrant further investigation. It was also concluded that EGS for power generation is still relatively a novel technology and remains to be proved on a large scale and that further research is needed for additional exploration of technological and economic aspects regarding the opportunities and challenges for CO2based EGS technology for combined carbon sequestration and power generation.ORGANIC RANKINE CYCLE CONFIGURATIONSImprovement of the efficiency of an energy conversion process can be carried out in many ways, including the selection of a suitable motive fluid or working with a mixture of more than one fluid. In this paper we have described improvement of the conversion efficiency by using advanced thermodynamic cycles, which can be applied to specific conditions of a given heat resource to enable adjustment of process and cycle parameters to different geofluid parameters. Such improved processes and thermodynamic cycles result in high efficiency while maintaining the high reliability, simple construction and operation as well as the high resource sustainability.PERFORMANCE ANALYSIS OF SUPERCRITICAL BINARY GEOTHERMAL POWER PLANTSIn this study, performance of the basic binary plant that operates at subcritical conditions is analysed with different workng fluids. After that, optimum turbine inlet pressures (cycle higher pressure) are determined under supercritical conditions. The turbine inlet temperature is kept constant. Performance improvement of switching to supercritical conditions is revealed.Analyses show that maximum power in optimal operating pressure is obtained by using R404a. The second suitable working fluid is R152a. Some articles are proposed to R152a for working fluid of supercritical ORC [7, 11]. When R404a is selected as the working fluid of the supercritical binary power plant, 13,751 KW power is generated in ideal conditions if the operating pressure is 8667 KPa. In subcritical conditions the same power plant can generate 8470 KW with the same working fluid. This reveals that there is 62.34% difference between subcritical and supercritical cases. Maximum thermal efficiency is also obtained by using R404a. In ideal conditions the maximum efficiency is 18.27%.Again difference between subcritical and supercritical cases s 62.4%. According to analysis, the basic binary cycle which uses R404a has the lowest required cooling water flow rate per power produced.

In this paper, five working fluid candidates have been selected for supercritical binary power plants that have 150C geofluid. These are R134a, isobutene, R152a, R404a, and n-Butane. In this study, it is revealed that maximum power and maximum thermal efficiency can be obtained by using R404a.It is interesting to note that the gas with maximum electricity generation is achieved with R404a. This gas is the mixture of R125, R143a, and R134a. The gas R404a which was used in the analysis is 44% R125, 52% R143a, and 4% R134a. As can be seen, using new gas mixtures in binary plants instead of pure work fluids reduces the irreversibility coming from the heat transfer and the power plant shows better performance. New investigations can be on this direction.How the performance of different geothermal fluids with different geothermal fluid temperatures will be was investigated and, as a result, it was found that when the geofluid temperatures increase, optimum turbine inlet pressure, net power produced, necessary work fluid flow, and energy produced for unit work fluid amount increase. However, the cooling water requirement per unit power produced decreases.RUSSIAN GEOTHERMAL POWER PLANTS EQUIPPED WITH ORC-UNITSA domestically produced 2.5 MW pilot binary-cycle geothermal power unit operating on geothermal brine discharged at the Pauzhetskaya GeoPP has been constructed for the first time. The results of commissioning works have confirmed serviceability of the equipment selected for the binary geothermal power unit at the Pauzhetskaya GeoPP. The mastering of binary power technologies on the pilot commercial model of the binary power unit at the Pauzhetskaya GeoPP opens prospects for wide-scale use of binary power technologies in Russia for recovering heat discharges from power-generating and industrial enterprises.

It is planned to introduce the geothermal power supply with the help of binary power plants in Russian regions (Kamchatka, Kuril Islands, Krasnodar region etc.). The basic increase of power plant capacities will be ensured due to large-scale exploration of low temperature geothermal sources with using the binary technologies.SECOND LAW ASSESSMENT OF BINARY PLANTS GENERATING POWER FROM LOW-TEMPERATURE GEOTHERMAL FLUIDSGeothermal binary plants are relatively poor converters of heat into work. First Law or thermal efficiencies typically lie in the range of 812%. As a consequence, a 12 percentage point improvement in power output translates into a gain of about 1020% in efficiency.The results show that binary plants can operate with very high Second Law or exergetic efficiencies even when the motive fluids are low-temperature and low-exergy. Exergetic efficiencies of 40% or greater have been achieved in certain plants with geofluids having specific exergies of 200 kJ/kg or lower. The main design feature leading to a high Second Law efficiency lies in the design of the heat exchangers to minimize the loss of exergy during heat transfer processes. Another important feature that can result in a high Second Law efficiency is the availability of low-temperature cooling water that allows a once-through system for waste heat rejection.

Finally, this analysis demonstrates that broad claims of 1550% more power output for the same heat input for Kalina cycles relative to organic Rankine binary cycles are not being achieved for plants in operation. Under simulated identical conditions of ambient temperature and cooling systems, the calculated difference in performance is about 3% in favor of a Kalina cycle. It is uncertain whether the difference in inlet brine exergy favoring the Kalina cycle in this study may have played a role in the efficiency advantage of the Kalina over the ORC. It must be pointed out that ORC geothermal technology is mature, with hundreds of megawatts of various kinds of cycles installed throughout the world, whereas the Hsavk plant is the only commercial Kalina cycle in operation so far.THERMODYNAMIC ANALYSIS AND PERFORMANCE OPTIMIZATION OF ORGANIC RANKINE CYCLES FOR THE CONVERSION OF LOW-TO-MODERATE GRADE GEOTHERMAL HEATA thermodynamic analysis and performance optimization of small binary cycle geothermal power plants operating with moderately low-temperature and liquid-dominated geothermal resources in the range of 110C to 160C, was considered. Optimal operating conditions were determined for maximum cycle power output per unit mass flow rate of the geothermal fluid. The maximum cycle power output was observed to increase exponentially with the geothermal resource temperature, whereas the optimal turbine inlet temperature increased almost linearly with the increase in the geothermal heat source. The addition of an IHE and/or an OFOH has been very prolific in improving the effectiveness of the conversion of the available geothermal energy into useful work. However, to avoid a susceptible thermal pollution of the environment caused by the geofluid being discarded as waste heat at relatively high temperature, a combined power generation and direct use in process or district heating applications as a cogeneration system, can be an additional option to improve the energy utilization. In addition, a performance analysis of selected organic working fluids, namely refrigerants R123, R152a, isobutane and n-pentane, was conducted under saturation temperature and subcritical pressure operating conditions of the turbine. Organic fluids with higher boiling point temperature, such as n-pentane, were recommended for the basic type of ORCs, whereas those with lower vapour specific heat capacity, such as butane, were more suitable for the regenerative ORCs. Although the present study limited itself to the thermodynamic performance of the selected organic fluids based on their thermodynamic properties, the selection of the optimal organic fluid is also subject to the chemical stability and compatibility with materials, the environmental impacts, the safety concerns, and the economical operation of the working fluids.THERMODYNAMIC CYCLE OPTIMIZATION IN THE GEOTHERMAL ENERGY PRODUCTIONReservoir Velika Ciglena is taken as an example for thermodynamic cycle optimization in geothermal power production, although the proposed approach can be applied to all high temperature reservoirs. The whole idea is based upon the specific energy, analysed for both possible production fluids. In each case, the wellhead temperature is related to the geothermal energy as the temperature difference at the primary heat exchanger mostly influences total amount of produced energy. Moreover, it is proved that energy of the geothermal fluid arises with second power of temperature difference.

Thermodynamic cycle in power production can be further optimized from the view of the energy ratio, impacting the efficiency of heat transfer from geothermal fluid to the working media. Although it is known that the saturated steam gives more energy per unit than liquid, a quantitative value of the steam-liquid ratio is mathematically demonstrated for Velika Ciglena. If the value of sink temperature is constant, steam-liquid ratio strongly decreases with the geothermal fluid temperature growth. In the case of sink temperature of 80C, this ratio can be changed for as much as 60 to 10, if the wellhead temperature would be alternated from 100 to 200C. This kind of investigation can be useful in the determination of working point in whatever geothermal installation.THERMODYNAMIC PRE-DETERMINATION OF POWER GENERATION POTENTIAL IN GEOTHERMAL LOW-TEMPERATURE APPLICATIONSThe conclusion of this investigation is that a simplified model is suitable to determine expected power output from any combination of finite heat source and finite heat sink using any type of real low-temperature power cycle.

Furthermore, this simplified model can be reduced to only require the input data of flow rate, heat capacity and entry temperature of the heat sink and heat source.

WATER RESOURCE ASSESSMENT OF GEOTHERMAL RESOURCES AND WATER USE IN GEOPRESSURED GEOTHERMAL SYSTEMSThe results from the two analyses indicate that water management can be an issue in the long-term planning of geothermal power plants. In Part I the growth in water demand resulting from growth in geothermal electricity generation was quantified for a range of scenarios. Analysis of future electricity growth scenarios indicates that in some cases growth in geothermal power will decrease the average water intensity of electricity generation. However in many western states fresh water intensity of electricity generation is already quite low, so growth in geothermal power will result in an increase in water intensity. The availability of produced water from oil and gas was considered as an alternative water source and sufficient quantities are available in several states to support geothermal development.

Geothermal resources are typically located in water-stressed areas, and any increase in water demand in these areas can represent challenges. It is therefore important to examine water consumption within the life cycle to better understand how it can be minimized. To that end, Part II expanded the suite of geothermal technologies evaluated over the life cycle to include low- temperature geopressured geothermal resources.

For geopressured geothermal systems, water consumption is focused on the construction stage, because water for reservoir makeup is not anticipated for these systems. Additionally, when normalized per kilowatt hour of lifetime energy output, water consumption during the construction stage for geopressured geothermal systems is similar to that of hydrothermal systems. Operational water losses are minimal because the spent geofluid is directed to a disposal well, and operators are not concerned with maintaining reservoir pressure for long-term sustainability. Hydrothermal and EGS systems, on the other hand, have the largest volume of water consumption for makeup water during operations. Non-potable water resources may be available to meet this operational water demand. In addition to potentially reusing geofluid from geopressured geothermal resources, other sources include water produced from oil and gas activities, water extracted from carbon capture and sequestration projects, and saline groundwater resources.SMALL GEOTHERMAL POWER PLANTS: DESIGN, PERFORMANCE AND ECONOMICSExtensive research and development over the last two decades has resulted in an impressive array of commercially available technologies to harness a wide range of geothermal resources. Off-the-shelf power systems of the Direct-Steam, Flash-Steam or Binary types can be ordered for use with low-to-high temperature resources of the vapour- or liquid-dominated variety, with any level of non-condensable gas or dissolved solids. If new plants are to be built, however, they must demonstrate an economic advantage over alternative systems. The economics are governed by site-specific and time-specific factors. For example, in the United States in the late 1990s, it has been difficult for any energy source to compete with natural-gas-fired plants, particularly combined steam-and-gas-turbine cycles.The effects of deregulation on the electric industry have also had a negative impact on geothermal plants. No longer endowed with favourable power purchase agreements, geothermal plant must now compete openly with other energy systems. Interestingly, privatization in many other countries, particularly those lacking in indigenous fossil fuels, has actually enhanced the attractiveness of geothermal plants which often turn out to be lowest cost option among new electric power plants.Since geothermal projects are heavily loaded with upfront costs for exploration, reservoir characterization, and drilling, all of which carry a measure of risk for investors, research directed at improving the technology in these areas is appropriate. Also, better methods of monitoring and predicting reservoir behaviour, both prior to and during exploitation would allow more systematic and reliable development strategies to maximize energy extraction over the long term.In countries with long histories of operating geothermal plants (such as Italy, the U.S. and New Zealand), geothermal re-powering projects are replacing order, less efficient units or units that no longer match the resources (due to long-term reservoir changes) with modern, high-efficiency, flexible systems. In many countries, both large and small, which are endowed with abundant geothermal resources, there is good potential for strong growth in geothermal power capacity. Of particular interest are Indonesia, the Philippines, Mexico, Japan, Italy, Kenya, and countries in Central America including Costa Rica, El Salvador, Guatemala and Nicaragua. In the United States, further development of its abundant geothermal resources will depend strongly on the prices of competing conventional fuels.Geothermal is now a proven alternative energy source for electric power generation. Because of its economic competitiveness in many situations, the operational reliability of the plants, and its environmentally friendly nature, geothermal energy will continue to serve those countries endowed with this natural energy resource.