A scenario for geothermal electric power development in Imperial Valley

The growth of geothermal electric power operations in Imperial Valley, California is projected over the next 40 yr. With commercial power forecast to become available in the 1980s, the scenario considers three subsequent growth rates of 40, 100 and 250 megawatts (MW) per year. These growth rates, along with estimates of the total resource size, result in a maximum level of electric power production ranging from 1000 to 8000 MW to be attained in the 2010 to 2020 time period. Power plant siting constraints are developed and used to make siting patterns for the 400 through the 8000 MW level of power production. Two geothermal technologies are included in the scenario: flashed steam systems which can produce their own cooling water from the geothermal steam condensate and which emit noncondensable gases to the atmosphere; and high pressure, confined flow systems which inject all the geothermal fluid back into the ground. An analysis of the scenario is made with regard to well drilling and power-plant construction rates, land use, cooling water requirements, and hydrogen sulfide emissions.     

Geothermal development and the Salton Sea

One of the limiting factors on energy development in the arid American West is the availability of water. Even geothermal development must take into account the hydrologie cycle of the surrounding area. In the Imperial Valley, the bloodstream of the economic body is water and, owing to the nature of the region and its water source, the mineralized Colorado River, the disposal of waste water is of major importance. The Salton Sea is presently the sump for agricultural drainage in that area. Quite incidently, the Sea has become popular for recreational use.

It is universally recognized that geothermal development in the Valley will involve the flow to the surface of large quantities of highly mineralized water. After extraction of heat, the water must be safely disposed of. Moreover, many geothermal power generation methods would require cooling water supplies, and other methods may require water for reservoir injection. Geothermal development may well impact the hydrologic cycle. Conversely, the requirements of the local hydrologic cycle may well impact the nature of geothermal development. The purpose of this study is to examine the relationship of the Salton Sea, a key element of the Imperial Valley water system, to potential geothermal development.     

Thermodynamic analysis and assessment of a novel integrated geothermal energy-based system for hydrogen production and storage

In this paper, thermodynamic analysis and assessment of a novel geothermal energy based integrated system for power, hydrogen, oxygen, cooling, heat and hot water production are performed. This integrated process consists of (a) geothermal subsystem, (b) Kalina cycle, (c) single effect absorption cooling subsystem and (d) hydrogen generation and storage subsystems. The impacts of some design parameters, such as absorption chiller evaporator temperature, geothermal source temperature, turbine input pressure and pinch point temperature on the integrated system performance are investigated to achieve more efficient and more effective. Also, the impacts of reference temperature and geothermal water temperature on the integrated system performance are studied in detail. The energetic and exergetic efficiencies of the integrated system are then calculated as 42.59% and 48.24%, respectively.     

Lime treatment program: an alternative cooling water treatment program for geothermal power plants in the philippines

The National Power Corporation (NAPOCOR) of the Philippines spends millions of pesos annually for treatment of cooling water and preventive maintenance work to ensure the efficient operation of its geothermal power plants supplied by liquid-dominated reservoirs. Therefore, NAPOCOR deemed it worthwhile to look for cheaper water treatment alternatives for the benefit not only of the geothermal power plants, but the whole country as well, in terms of lower power generation costs and improved plant operation. The results of tests on the use of lime in the cooling water of NAPOCOR geothermal power plants are presented in this paper. Initial results show substantial savings in water treatment costs and a significant decrease in corrosion rates on metal parts and equipment.     

The application of the Na-K-Ca geothermometer to thermal areas of Utah and the imperial valley,California

The sodium (Na), potassium (K), calcium (Ca) geothermometer is discussed as a tool for locating and evaluating areas prospectively valuable for geothermal development. Presented is a regional analysis of the major thermal springs of Utah to demonstrate the use of the Na-K-Ca geothermometer as a rapid and meaningful method of geothermal reconnaissance. Of the thermal areas of Utah, Roosevelt Hot Springs show the greatest geothermal potential where estimated temperatures are nearly 300 °C. This compares favorably with estimated and measured temperatures from proven geothermal fields such as Cerro Prieto in Mexico and the Salton Sea field of California. Also presented are more detailed studies of LaVerkin Ho¹ Springs and Wilson Hot Springs, Utah, and the Mesa anomaly, Imperial Valley, California. These studies examine the accuracy and precision of the Na-K-Ca geothermometer and the physical conditions under which it can be reliably used to predict subsurface temperatures. It is shown that in the saline environment of the Imperial Valley, it should be possible to obtain useful information even though the results might normally be considered suspect due to concentration or dilution of the analyzed samples.     

Geothermal energy use in hydrogen liquefaction

We propose the use of geothermal energy for hydrogen liquefaction, and investigate three possible cases for accomplishing such a task including (1) using geothermal output work as the input for a liquefaction cycle; (2) using geothermal heat in an absorption refrigeration process to precool the gas before the gas is liquefied in a liquefaction cycle; and (3) using part of the geothermal heat for absorption refrigeration to precool the gas and part of the geothermal heat to produce work and use it in a liquefaction cycle (i.e., cogeneration). A binary geothermal power plant is considered for power production while the precooled Linde–Hampson cycle is considered for hydrogen liquefaction. A liquid geothermal resource is considered and both ideal (i.e., reversible) and non-ideal (e.g., irreversible) system operations are analyzed. A procedure for such an investigation is developed and appropriate performance parameters are defined. Also, the effects of geothermal water temperature and gas precooling temperature on system performance parameters are studied. The results show that there is a significant amount of energy savings potential in the liquefaction work requirement as a result of precooling the gas in a geothermal absorption cooling system. Using geothermal energy in a cogeneration scheme (power production and absorption cooling) also provides significant advantages over the use of geothermal energy for power production only.     

Economics of geothermal energy development (In Imperial County,California)

The geothermal resources in Imperial County appear to have the potential of developing somewhere between 3000 and 6000 mW of power. At 3000 mW, the geothermal energy would add 9% to present installed capacity in California. By the year 2000, geothermal energy might supply about 4–5% of total capacity at that time.The steam flash technology presently available would appear to produce energy at competitive costs in the neighborhood of 20–28 mills per kWh, which is somewhat below comparative costs for coal, nuclear and petroleum as energy sources for electricity conversion.Geothermal development would provide benefits to Imperial County in terms of moderate increases in employment and payroll, royalty benefits and most significantly, perhaps, in tax revenues.     

A new solar and geothermal based integrated ammonia fuel cell system for multigeneration

In this study, a new solar and geothermal based integrated system is developed for multigeneration of electricity, fresh water, hydrogen and cooling. The system also entails a solar integrated ammonia fuel cell subsystem. Furthermore, a reverse osmosis desalination system is used for fresh water production and a proton exchange membrane based hydrogen production system is employed. Moreover, an absorption cooling system is utilized for district cooling via available system waste heat. The system designed is assessed thermodynamically through approaches of energy and exergy analyses. The overall energy efficiency is determined to be 42.3%. Also, the overall exergy efficiency is assessed, and it is found to be 21.3%. The exergy destruction rates in system components are also analysed and the absorption cooling system generator as well as geothermal flash chamber are found to have comparatively higher exergy destruction rates of 2370.2 kW and 643.3 kW, respectively. In addition, the effects of varying system parameters on the system performance are studied through a parametric analyses of the overall system and associated subsystems.     

Optimum design criteria for an Organic Rankine cycle using low-temperature geothermal heat sources

A cost-effective optimum design criterion for Organic Rankine power cycles utilizing low-temperature geothermal heat sources is presented. The ratio of the total heat exchanger area to net power output is used as the objective function and was optimized using the steepest descent method. Evaporation and condensation temperatures, geothermal and cooling water velocities are varied in the optimization method. The optimum cycle performance is evaluated and compared for working fluids that include ammonia, HCFC123, n-Pentane and PF5050. The optimization method converges to a unique solution for specific values of evaporation and condensation temperatures and geothermal and cooling water velocities. The choice of working fluid can be greatly affect the objective function which is a measure of power plant cost and in some instances the difference could be more than twice. Ammonia has minimum objective function and maximum geothermal water utilization, but not necessarily maximum cycle efficiency. Exergy analysis shows that efficiency of the ammonia cycle has been largely compromised in the optimization process than that of other working fluids. The fluids, HCFC 123 and n-Pentane, have better performance than PF 5050, although the latter has most preferable physical and chemical characteristics compared to other fluids considered.     

Economics of hydrogen production and liquefaction by geothermal energy

Seven models are considered for the production and liquefaction of hydrogen by geothermal energy. In these models, we use electrolysis and high-temperature steam electrolysis processes for hydrogen production, a binary power plant for geothermal power production, and a pre-cooled Linde–Hampson cycle for hydrogen liquefaction. Also, an absorption cooling system is used for the pre-cooling of hydrogen before the liquefaction process. A methodology is developed for the economic analysis of the models. It is estimated that the cost of hydrogen production and liquefaction ranges between 0.979 $/kg H₂ and 2.615 $/kg H₂ depending on the model. The effect of geothermal water temperature on the cost of hydrogen production and liquefaction is investigated. The results show that the cost of hydrogen production and liquefaction decreases as the geothermal water temperature increases. Also, capital costs for the models involving hydrogen liquefaction are greater than those for the models involving hydrogen production only.     

Current status of ground source heat pumps and underground thermal energy storage in Europe

Geothermal Heat Pumps, or Ground Coupled Heat Pumps (GCHP), are systems combining a heat pump with a ground heat exchanger (closed loop systems), or fed by ground water from a well (open loop systems). They use the earth as a heat source when operating in heating mode, with a fluid (usually water or a water–antifreeze mixture) as the medium that transfers the heat from the earth to the evaporator of the heat pump, thus utilising geothermal energy. In cooling mode, they use the earth as a heat sink. With Borehole Heat Exchangers (BHE), geothermal heat pumps can offer both heating and cooling at virtually any location, with great flexibility to meet any demands. More than 20 years of R&D focusing on BHE in Europe has resulted in a well-established concept of sustainability for this technology, as well as sound design and installation criteria. Recent developments are the Thermal Response Test, which allows in-situ-determination of ground thermal properties for design purposes, and thermally enhanced grouting materials to reduce borehole thermal resistance. For cooling purposes, but also for the storage of solar or waste heat, the concept of underground thermal energy storage (UTES) could prove successful. Systems can be either open (aquifer storage) or can use BHE (borehole storage). Whereas cold storage is already established on the market, heat storage, and, in particular, high temperature heat storage (> 50 °C) is still in the demonstration phase. Despite the fact that geothermal heat pumps have been in use for over 50 years now (the first were in the USA), market penetration of this technology is still in its infancy, with fossil fuels dominating the space heating market and air-to-air heat pumps that of space cooling. In Germany, Switzerland, Austria, Sweden, Denmark, Norway, France and the USA, large numbers of geothermal heat pumps are already operational, and installation guidelines, quality control and contractor certification are now major issues of debate.     

基于有机朗肯循环的低温地热制冷系统热力学分析

为有效利用低温地热资源,本文以有机朗肯–蒸汽压缩制冷系统为研究对象,建立了系统的热力学模型,分析比较了分别以R290、R600、R600a、R601、R601a和R1270为工质时的系统性能,并以系统整体COP和每千瓦制冷量所对应的工质流量为关键指标对工质进行了优选。分析结果表明：当地热水温度为60 ~ 90℃,冷凝温度为30 ~ 55℃,蒸发温度为 –15 ~15℃时,R601是系统的最佳工质。当地热水温度为90℃,其余参数为典型工况值时,工质R601所对应的系统性能系数COP为0.49。     

Geothermal energy in imperial county,California: Environmental,socio-economic,demographic, and public opinion research conclusions and policy recommendations

It is estimated that thousands of megawatts of electricity could be generated from the geothermal fluids which underlie agricultural fields in Imperial County, California. Many potential environmental problems appear generally controllable. The possible inter-relationships between geothermal development and subsidence, seismicity, and water availability are, however, difficult to predict, and evaluation must await long-termed, commercial-sized operations. County population will interact with energy development through employment, geographical distribution, and interaction with the larger Mexican labor pool. Exportation of the bulk of the generated electricity, however, will limit the local socio-economic impact. County residents favor geothermal development at a ratio of almost 9:1. Thirteen policy recommendations applicable to other KGRA'S in the western U.S. include: the desirability of positive public opinion, the encouragement of on-line electrical power at an early stage in the development process, the importance of determining economic-technological exploitation feasibility, and the influences of local, state, and federal regulations.     

Exergy,exergoeconomic and multi-objective optimization of a clean hydrogen and electricity production using geothermal-driven energy systems

In this research paper, comprehensive thermodynamic modeling of an integrated energy system consisting of a multi-effect desalination system, geothermal energy system, and hydrogen production unit is considered and the system performance is investigated. The system's primary fuel is a geothermal two-phase flow. The system consists of a single flash steam-based power system, ORC, double effect water–lithium bromide absorption cooling system, PEM electrolyzer, and MED with six effects. The effect of numerous design parameters such as geothermal temperature and pressure on the net power of steam turbine and ORC cycle, the cooling capacity of an absorption chiller, the amount of produced hydrogen in PEM electrolyzer, the mass flow rate of distillate water from MED and the total cost rate of the system are studied. The simulation is carried out by both EES and Matlab software. The results indicate the key role of geothermal temperature and show that both total exergy efficiency and total cost rate of the system elevate with increasing geothermal temperature. Also, the impact of changing absorption chiller parameters like evaporator and absorber temperatures on the COP and GOR of the system is investigated. Since some of these parameters have various effects on cost and efficiency as objective functions, a multi-objective optimization is applied based on a Genetic algorithm for this system and a Pareto-Frontier diagram is presented. The results show that geothermal main temperature has a significant effect on both system exergy efficiency and cost of the system. An increase in this temperature from 260 C to 300 C can increase the exergy efficiency of the system for an average of 12% at various working pressure and also increase the cost of the system by 13%.     

Performance evaluation of a geothermal based integrated system for power,hydrogen and heat generation

In the present study, an integrated system is proposed and thermodynamically analyzed to reduce greenhouse gas (GHG) emissions while improving overall system performance. The integrated system is comprised of a supercritical carbon dioxide (CO₂) Rankine cycle cascaded by an Organic (R600) Rankine cycle, an electrolyzer, and a heat recovery system. It is designed to utilize a medium-to-high temperature geothermal energy source for power and hydrogen production, and thermal energy utilization for space heating. Therefore, parametric studies for the supercritical CO₂ cycle, the Organic (R600) cycle, and the overall system are conducted. In addition, the effect of various operational conditions, such as geothermal source, ambient and cooling water temperatures on the performance of each cycle and the integrated system, is illustrated. It is found that increasing geothermal source temperature results in slight increases of the exergetic efficiency of the overall system. The energy efficiencies of the CO₂ and Organic Rankine cycles do not considerably vary with source temperature changes. The decay of the cooling water temperature leads to a decrease in the overall system exergetic efficiency. The system configuration, which is introduced, is capable of producing about 180 kg/h for the geothermal source of mass flow rate of 40 kg/s and a temperature of 473 K.     

高地温隧洞围岩温度场有限元分析

针对高地温隧洞存在的严重高温现象,以齐热哈塔尔水电工程为例,采用ANSYS软件对隧洞围岩高温段自然通风和采取降温措施两种工况进行模拟研究。与实测数据对比分析表明,随着自然通风和降温措施时间的增加,隧洞内部温度逐渐降低,最后达到平衡状态,模拟结果与实测数据基本吻合;同时对于隧洞整体围岩降温周期长、难度大的特点,可采取局部降温的措施达到施工作业要求的温度,这为工程项目的实施提供了可靠参考。     

A study on the optimized control strategies of geothermal heat pump system and absorption chiller‐heater

The world is becoming increasingly interested in renewable energy including geothermal energy. The utilization of geothermal systems is currently low because geothermal systems and existing source systems are used independently, but the supply rate of a geothermal system is increasing. Therefore, suggesting efficient operation plans and evaluations of the energy consumption and efficiency of a geothermal system is needed. This paper reports the results of a field study and survey of the present applications and operation conditions of a geothermal system. In addition, this paper proposes an efficient operation strategy for a geothermal system and compares this operation strategy with an existing operation strategy through simulation. The problems of existing operation condition were found out through a field study, and alternatives were proposed. The improvements were evaluated using the transient systems simulation program. And it would be possible for the reduction of the energy consumption through the comparative analysis of equipment efficiency and energy consumption. The result of analyzing the proposed combination header method through simulations compared with existing operation conditions can increase the use of geothermal systems, but the combined cooling and hot water of a geothermal heat pump and existing thermal source system reduced the efficiency of the heat pump. As a result of simulation on individual load‐sharing method, efficiency of geothermal system is increasing compared with the combination header method. This method was especially made to separate geothermal system's water loop and existing thermal source system's water loop. Copyright © 2013 John Wiley & Sons, Ltd.     

油区地热能开发新工艺的研究

在油区地热资源开发过程中,应用井内换热和尾水回灌的对井供热系统可以提高地热资源开发效益、避免地热水资源浪费和实现可持续发展。文章使用了地热储二维分布模型和井筒传热模型．通过对地热储的数值模拟预测了尾水回灌过程中地热储的压力响应和冷却效应,通过对井筒的热力计算得到了井内换热器的最优设计方法。计算结果表明,地热储对尾水回灌的压力响应非常迅速,压力场能很快达到稳定;回灌冷水的影响区集中在回灌井的周围,冷区半径增长的速度越来越慢。井内换热器在最佳设置深度时,经济效益达到最大值;井内换热器设置深度不变,增大载热水的流量经济效益将增加,但是获得的热能温度下降。     

Study of different grouting materials used in vertical geothermal closed-loop heat exchangers

As a renewable source, low-enthalpy geothermal energy is becoming more relevant in heating and cooling buildings, by using an adapted heat pump to exchange thermal energy with the ground. Vertical closed-loop geothermal systems exchange heat with the ground through a closed buried pipe system, sealed with a grouting material that ensures the stability and thermal transmission of the borehole. Different grouting materials have been tested recently, which use cement or bentonite as a base material. However, the use of recycled materials, which might contribute to the sustainability of the project, has not yet been studied. This paper analyzes the use of different natural and recycled aggregates as main constituents in cement-based mortars. Results show that all mixes fulfill the minimum consistency and strength requirements. The use of any of the aggregates proposed improves the thermal conductivity compared to the cement mortar on its own, independently of the proportion used. Limestone sand, silica sand and electric arc furnace slag enhance the thermal conductivity of the grout as its proportion of use increases. However, no satisfactory results have been obtained for Construction and Demolition Waste-based mixes because of their high water requirement.     

基于模糊综合权重法的地热水资源梯级利用模式评价

研究地热水资源梯级开发利用模式对于合理开发利用地下水资源意义重大。首先对地热水资源梯级开发利用模式进行设计,提出五种主要的地热水资源梯级开发利用模式;然后从社会经济、产业结构、地热水资源等三方面构建了地热水资源梯级利用模式评价指标体系,并简要介绍了模糊综合权重法的评价步骤;最后以安阳市为例,在制定模式评价标准的基础上,采用模糊层次分析法和模糊综合权重法分别评价了安阳市的地热水资源梯级开发利用模式。结果表明,运用模糊综合权重法得到的结果较符合实际情况,与区域的地域条件相协调,满足各区域的经济发展需要,为安阳市的地热水开发利用提供了参考。