Department of Civil Engineering

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3D characterization of thermo-hydro-geological fields and estimation of power potential from Puga geothermal reservoir, Ladakh, India
(Elsevier, 2020-02) Jha, Shibani K
Puga geothermal reservoir in India shows promising thermal manifestation zones. However, no systematic study is done to develop the 3D characterization of thermo-hydro-geological fields for this reservoir. A new methodology is developed to characterize porosity, thermal conductivity, density, specific heat, radioactive heat capacity and permeability as 3D block heterogeneity till a depth of 4 km from resistivity maps. The temperature field and stored heat energy in a geothermal reservoir are dependent on these parameters. Based on the developed characterization, 3D coupled flow and heat transport processes are simulated to estimate the extractable temperature and power to be generated from doublet extraction scheme with various operational conditions. The study finds energy recovery factor of 8.16% and 37.83% and minimum electrical power potential of 1.2 MWe and 50.4 MWe with 12% conversion efficiency from the depths of 250 m and 1875 m respectively over 50 years from Puga field. Sensitivity for fluid injection/extraction rate and well spacing is studied. The results show promising power potential from 1.4 to 2 km of depth. The block heterogeneity characterization is more reliable than layered and homogeneous characterization. The outcomes would certainly acquire a significant role in decision-making strategies for Puga geothermal exploitation.
Assessment of floating solar PV (FSPV) potential and water conservation: Case study on Rajghat Dam in Uttar Pradesh, India
(Elsevier, 2022-02) Jha, Shibani K; Mittal, Ravi Kant
Widely acceptable Photovoltaic (PV) technology faces the challenge of substantial land requirement. However, emerging PV technology over water bodies through floating solar panels can resolve this challenge and additionally leads to operation of the panels at low temperature, improving the energy generation efficiency and insulating water bodies to account for reduction in evaporation loss. In this work, simulation tasks are performed to assess the technical potential of floating photovoltaic power generation and discusses the sustainable system of floating solar PV technology in terms of prospective PV potential, conservation of water and potential to conserve agriculture land bank. The study estimates, power potential of 6513 MWp for 25% coverage of total submergence area at Rajghat dam located in the Southern part of Uttar Pradesh, India, and annual power generation of 10,623,501 MWh. The study also reports annual evaporation loss reduction of 1395 cubic meter per MWp (or 0.9 l per kWh) as an additional benefit. In terms of economic assessment, the Levelized cost of energy (LCOE) is reported as $ 0.036/kWh (INR 2.61/kWh) with 8.55% internal rate of return (IRR), a very encouraging parameter for large scale deployment of FSPV plants. Based on the findings, the study recommends FSPV installation in water reservoirs, justified by considerable savings in water evaporation losses and avoiding use of cultivable land for solar PV Installation purpose.
Assessment of subsurface temperature distribution from the gauged wells of Puga Valley, Ladakh
(Springer, 2017-04) Jha, Shibani K
Among the distinguished zones of geothermal potential in India, the Puga Valley is identified as one of the potential sites for tapping geothermal energy at industrial scale. The hydrogeological properties and the temperature variations with depth have been examined under the Geological Society of India by drilling borewells at a few locations. The temperature distribution is one of the most essential parameters in quantifying the energy potential of a geothermal reservoir in its life time. Such temperature distribution has not been mapped for the Puga Valley. 2D Kriging technique is adopted in this study to assess temperature distribution for thermal manifestation zone at various depths and these are further used to estimate the thermal gradients at ungauged locations of the valley. From the results obtained, it is observed that the thermal gradient in the eastern zone of the valley is relatively higher. This indicates a possible bottom heat source in the eastern zone of the valley. The results of this study could be helpful in identifying the distinctive conceivable locations of injection and production wells for the extraction of entrapped heat within the rock strata. Also, a priority order is drawn in terms of thermal gradients at gauged and ungauged locations which may be helpful in deciding the zones of high and low heat sources in the reservoir.
Conceptual modeling and characterization of Puga geothermal reservoir, Ladakh, India
(Elsevier, 2018-03) Jha, Shibani K
Evaluation of a potential geothermal reservoir depends on the conceptual model which governs fluid flow and heat transfer in the reservoir. Knowing the spatial variation of reservoir parameters is essential to develop a conceivable and explicable conceptual model. Lack of deep reservoir characteristics impaired the development of conceptual model for Puga geothermal field, India. This study proposes a methodology to develop a conceptual model of Puga geothermal field. The proposed methodology utilizes the resistivity model developed by National Geophysical Research Institute as preliminary data. The conceptual model developed in this study, maps the spatial variation of thermo-hydro-geological properties of Puga reservoir. The mapped properties of the reservoir are porosity, thermal conductivity, specific heat, radioactive heat capacity, density and permeability of reservoir. Furthermore, lateral extent of the possible heat source and spatial variation of steady state temperature of the reservoir are also estimated. The estimated reservoir temperature from the conceptual model of Puga geothermal field is in agreement with temperature interpretations of Na/K and Na-K-Ca geothermometer studies. The resulting conceptual model will further aid in the operational phase of reservoir development like volumetric assessment of reservoir potential and reservoir potential estimation under various extraction configuration.
Extraction schemes to harness geothermal energy from puga geothermal field, India
(Taylor & Francis, 2019-05) Jha, Shibani K
Various extraction schemes are proposed in this study for the exploitation of the Puga geothermal reservoir by considering the field constraints and geological structural setting. Considering a 3D thermo-hydro coupled simulation model, the dynamic response of the reservoir under the proposed extraction schemes is studied in terms of extractable power. The transients of extractable power are further examined by evaluating minimum extractable power in the successive 10 years of reservoir lifetime. A mathematical model is proposed to estimate the probable drilling cost involved in installing the proposed extraction schemes. Considering the evaluated parameters, the dominance of each proposed scheme is studied using Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). In view of the diversified perception of decision makers, sensitivity analysis is performed to study the variation of hierarchy. The evaluated dominance helps to identify the favorable extraction scheme that can tradeoff between extractable power and drilling cost. The findings of this study, supported by the findings of sensitivity analysis, ratify that the doublet extraction scheme is the most favorable extraction scheme for the exploitation of the Puga geothermal reservoir.
Groundwater Resource Estimation, Recharge Techniques and Research Initiatives in India
(Research Publishing, 2008) Jha, Shibani K
Identification and analysis of barriers for harnessing geothermal energy in India
(Elsiever, 2022-03) Singh, Ajit Pratap; Jha, Shibani K
The Indian Government envisaged generating 10 GW using geothermal power by 2030. Reaching this milestone is linked with numerous challenges, as geothermal exploitation in India is in the nascent stages. In this work, possible barrier categories and barriers to harness geothermal energy in India are identified with the help of literature review and questionnaire-based surveys. Fuzzy Delphi method is used to find the significant barriers among the listed. Subsequently, Fuzzy Analytical Hierarchy Process (Fuzzy AHP) is used to determine the relative dominance of each barrier category and the barriers within each category. Outcomes of this research show that the resource barrier category obtained highest priority. This category includes various barriers such as (i) conceptualization of geothermal reservoir, (ii) estimation of theoretical heat energy, (iii) determination of extractable power, and (iv) selection of suitable extraction schemes. Results suggest that a comprehensive conceptual model presenting the subsurface variation of thermo-hydro-geological parameters with depth at a geothermal field can support the accurate depiction of the available and extractable thermal potential. Stability of the obtained hierarchy is examined by sensitivity analysis. Findings of this study help to identify the barriers that can be reasonably encountered and to propose developmental activities to harness geothermal energy.
Identification of prospective significance levels for potential geothermal fields of India
(Elsevier, 2018-11) Jha, Shibani K
This study aims to predict prospective significance levels of potential geothermal fields already identified by Geological Survey of India (GSI) and National Geophysical Research Institute (NGRI) by field investigations. Wide range of criteria's are considered in determining the relative significance level of each geothermal field in terms of cumulative score. These criteria's include useful resource base (URBfield), Areal extent (Afield), Minimum temperature as per geothermometry (Tmin), Maximum temperature as per geothermometry (Tmax), Utilization score (USfield), Cumulative discharge of thermal springs (Q), Minimum electrical resistivity (Rmin), Maximum electrical resistivity (Rmax) and Representative reservoir temperature as per Gas thermometry (Tgas). Fuzzy Analytical Hierarchy Process (Fuzzy AHP) is used to study the dominance of each geothermal field, evaluated over the aforementioned criteria to find cumulative score. URBfield depends on possible extraction temperature of reservoir estimated by COMSOL Multiphysics® modelling and simulation software. The geothermal fields are conceptualized as shallow homogenous reservoirs with injection and extraction wells. The attributes of remaining criteria are collected from published works of NGRI and GSI. The results of this study ratify that Puga geothermal field is the most significant site among the identified potential geothermal fields, to conduct further developmental works and for commercial extraction of geothermal energy.
Multiphase models for simulating hot and slightly miscible DNAPL (dense non-aqueous phase fluids) in a saturated rock fracture under deformation
(IWA, 2009) Jha, Shibani K
In the present study a two dimensional model is first developed to show the behaviour of dense non-aqueous phase liquids (DNAPL) within a rough fracture. To consider the rough fracture, the fracture is imposed with variable apertures along its plane. It is found that DNAPL follows preferential pathways. In next part of the study the above model is further extended for non-isothermal DNAPL flow and DNAPL-water interphase mass transfer phenomenon. These two models are then coupled with joint deformation due to normal stresses. The primary focus of these models is specifically to elucidate the influence of joint alteration due to external stress and fluid pressures on flow driven energy transport and interphase mass transfer. For this, it is assumed that the critical value for joint alteration is associated with external stress and average of water and DNAPL pressures in multiphase system and the temporal and spatial evolution of joint alteration are determined for its further influence on energy transport and miscible phase transfer. The developed model has been studied to show the influence of deformation on DNAPL flow. Further this preliminary study demonstrates the influence of joint deformation on heat transport and phase miscibility via multiphase flow velocities. It is seen that the temperature profile changes and shows higher diffusivity due to deformation and although the interphase miscibility value decreases but the lateral dispersion increases to a considerably higher extent.
Pattern of two-phase (DNAPL-Water) flow through single fracture under temporal evolution of aperture
(ASCE, 2011-04) Jha, Shibani K
Among the distinguished zones of geothermal potential in India, the Puga Valley is identified as one of the potential sites for tapping geothermal energy at industrial scale. The hydrogeological properties and the temperature variations with depth have been examined under the Geological Society of India by drilling borewells at a few locations. The temperature distribution is one of the most essential parameters in quantifying the energy potential of a geothermal reservoir in its life time. Such temperature distribution has not been mapped for the Puga Valley. 2D Kriging technique is adopted in this study to assess temperature distribution for thermal manifestation zone at various depths and these are further used to estimate the thermal gradients at ungauged locations of the valley. From the results obtained, it is observed that the thermal gradient in the eastern zone of the valley is relatively higher. This indicates a possible bottom heat source in the eastern zone of the valley. The results of this study could be helpful in identifying the distinctive conceivable locations of injection and production wells for the extraction of entrapped heat within the rock strata. Also, a priority order is drawn in terms of thermal gradients at gauged and ungauged locations which may be helpful in deciding the zones of high and low heat sources in the reservoir.
Prospects of renewable energy sources in India: Prioritization of alternative sources in terms of Energy Index
(Elsevier, 2017-05) Jha, Shibani K
The growing energy demand in progressing civilization governs the exploitation of various renewable sources over the conventional sources. Wind, Solar, Hydro, Biomass, and waste & Bagasse are the various available renewable sources in India. A reliable nonconventional geothermal source is also available in India but it is restricted to direct heat applications. This study archives the status of renewable alternatives in India. The techno economic factors and environmental aspects associated with each of these alternatives are discussed. This study focusses on prioritizing the renewable sources based on a parameter introduced as Energy Index. This index is evaluated using cumulative scores obtained for each of the alternatives. The cumulative score is obtained by evaluating each alternative over a range of eleven environmental and techno economic criteria following Fuzzy Analytical Hierarchy Process. The eleven criteria's considered in the study are Carbon dioxide emissions (CO2), Sulphur dioxide emissions (SO2), Nitrogen oxide emissions (NOx), Land requirement, Current energy cost, Potential future energy cost, Turnkey investment, Capacity factor, Energy efficiency, Design period and Water consumption. It is concluded from the study that the geothermal source is the most preferable alternative with highest Energy Index. Hydro, Wind, Biomass and Solar sources are subsequently preferred alternatives.
Study of Geothermal Energy Potential with Geothermal Doublet: A Case Study for Puga Valley Ladakh
(Springer, 2017-10) Jha, Shibani K
The growing demands for renewable energy have made geothermal energy a popular option in recent past. The efficiency of such a system depends on the retention and transport capacity of heat. Hence, model studies under different reservoir conditions are essential. This study is concerned about a geothermal doublet to produce hot groundwater, extract heat, and reinject the cooled down water into the subsurface. Studies are performed by computational tool, COMSOL Multiphysics, to estimate the potential of geothermal reservoirs. The study shows the effect of geothermal doublet on coupled heat transport and groundwater flow. Puga Valley in Ladakh district, 1,600 km from New Delhi and at an altitude of about 4,400 m is considered for the study. The transient temperature distribution in the reservoir is discussed. The effect of natural groundwater flow on the temperature distribution and the influence of production and injection wells, the geothermal doublet, are also discussed.