Origin and evolution of the bread wheat D genome

Bread wheat (Triticum aestivum) is a globally dominant crop and major source of calories and proteins for the human diet. Compared with its wild ancestors, modern bread wheat shows lower genetic diversity, caused by polyploidisation, domestication and breeding bottlenecks. Wild wheat relatives represent genetic reservoirs, and harbour diversity and beneficial alleles that have not been incorporated into bread wheat. Here we establish and analyse extensive genome resources for Tausch’s goatgrass (Aegilops tauschii), the donor of the bread wheat D genome. Our analysis of 46 Ae. tauschii genomes enabled us to clone a disease resistance gene and perform haplotype analysis across a complex disease resistance locus, allowing us to discern alleles from paralogous gene copies. We also reveal the complex genetic composition and history of the bread wheat D genome, which involves contributions from genetically and geographically discrete Ae. tauschii subpopulations. Together, our results reveal the complex history of the bread wheat D genome and demonstrate the potential of wild relatives in crop improvement

Experimental and numerical investigation of heat transfer performance and sustainability of deep borehole heat exchangers coupled with ground source heat pump systems

Deep borehole heat exchangers (DBHEs) are a state-of-the-art and feasible apparatus for building heating and renewable energy utilization. Conventional BHEs with long-term operation may experience notable performance degradation, DBHE may provide an alternative way to overcome this issue. In this paper, a numerical model was developed by considering the ground temperature gradient in the axial direction and multilayer thermal properties of rock and soil and was used to simulate the temperature distribution and the performance characteristics of coaxial DBHEs. The effectiveness of the model was validated against the experimental data collected from a demonstration project. It was shown that the simulation results agreed well with the experimental data. The DBHEs could offer a higher heat exchange capacity in comparison to conventional BHEs. In the intermittent operation for 10 years, the decreasing proportions of the outlet temperature under four different operation modes with the run-stop ratio (i.e. the ratio of the running time to the stopping time in a day) of 8:16, 12:12, 16:8 and 24:0, were no more than 3.57%. The rock temperature profiles in the heating mode of both commercial and residential buildings were presented and the annual decreasing proportions were less than 4.0%. The findings obtained from this study could be used as a reference for sustainability research of DBHEs under different working conditions and operation modes

Numerical Study on the Long-Term Performance and Load Imbalance Ratio for Medium-Shallow Borehole Heat Exchanger System

To contribute to the goal of carbon neutralization, the closed-loop borehole heat exchanger system is widely applied to use geothermal energy for building cooling and heating. In this work, a new type of medium-shallow borehole heat exchanger (MSBHE) is proposed, which is coaxial type and has a depth range between 200 m to 500 m. To investigate the long-term performance of MSBHE in the area with unbalanced cooling and heating load of buildings and the sustainable load imbalance ratio under different design parameters, a comprehensive numerical model is established. The results show that the drilling depth significantly influences the sustainable load imbalance ratio of MSBHE. As the drilling depth is increased from 200 m to 500 m, the load imbalance ratio of the MSBHE increases from 20.76% to 60.29%. In contrast, the load imbalance ratio is always kept at the same level with different inlet velocities and operation modes. Furthermore, in a 9-MSBHE array system, the heat exchanger located in the middle of the array has the lowest load imbalance ratio of 48.97%, which is 15.98% lower than the borehole in the edge location. This is caused by the significant influence of the shifted-load phenomenon among MSBHEs in an array system. The findings of the work imply that this newly proposed MSBHE can sustain a notable load imbalance ratio, which is particularly applicable to the areas with a strong imbalance of annual building load

Molecular genetics and quantitative traits divergence among populations of Eothenomys miletus from Hengduan Mountain region

Abstract An important objective of evolutionary biology has always been to grasp the evolutionary and genetic processes that contribute to speciation. The present work provides the first detailed account of the genetic and physiological adaptation to changing environmental temperatures as well as the reasons causing intraspecific divergence in the Eothenomys miletus from the Hengduan Mountain (HM) region, one of the biodiversity hotspots. One hundred sixty‐one E. miletus individuals from five populations in the HM region had their reduced‐representation genome sequenced, and one additional individual from each community had their genomes resequenced. We then characterized the genetic diversity and population structure of each population and compared the phenotypic divergence in traits using neutral molecular markers. We detected significant phenotypic and genetic alterations in E. miletus from the HM region that were related to naturally occurring diverse habitats by combining morphometrics and genomic techniques. There was asymmetric gene flow among the E. miletus populations, indicating that five E. miletus populations exhibit an isolation‐by‐island model, and this was supported by the correlation between FST and geographic distance. Finally, PST estimated by phenotypic measures of most wild traits were higher than differentiation at neutral molecular markers, indicating directional natural selection favoring different phenotypes in different populations must have been involved to achieve this much differentiation. Our findings give information on the demographic history of E. miletus, new insights into their evolution and adaptability, and literature for studies of a similar nature on other wild small mammals from the HM region

A comprehensive review of deep borehole heat exchangers (DBHEs): subsurface modelling studies and applications

Deep borehole heat exchangers (DBHEs) with depths exceeding 500 m have been researched comprehensively in the literature, focusing on both applications and subsurface modelling. This review focuses on conventional (vertical) DBHEs and provides a critical literature survey to analyse (i) methodologies for modelling; (ii) results from heat extraction modelling; (iii) results from modelling deep borehole thermal energy storage; (iv) results from heating and cooling models; and (v) real case studies. Numerical models generally compare well to analytical models whilst maintaining more flexibility, but often with increased computational resources. Whilst in-situ geological parameters cannot be readily modified without resorting to well stimulation techniques (e.g. hydraulic or chemical stimulation), engineering system parameters (such as mass flow rate of the heat transfer fluid) can be optimised to increase thermal yield and overall system performance, and minimise pressure drops. In this active research area, gaps remain, such as limited detailed studies into the effects of geological heterogeneity on heat extraction. Other less studied areas include: DBHE arrays, boundary conditions and modes of operation. A small number of studies have been conducted to investigate the potential for deep borehole thermal energy storage (BTES) and an overview of storage efficiency metrics is provided herein to bring consistency to the reporting of thermal energy storage performance of such systems. The modifications required to accommodate cooling loads are also presented. Finally, the active field of DBHE research is generating a growing number of case studies, particularly in areas with low-cost drilling supply chains or abandoned hydrocarbon or geothermal wells suitable for repurposing. Existing and planned projects are thus presented for conventional (vertical) DBHEs. Despite growing interest in this area of research, further work is needed to explore DBHE systems for cooling and thermal energy storage

In-situ test and numerical investigation on the long-term performance of deep borehole heat exchanger coupled heat pump heating system

Given the substantial initial investment required by the drilling and implementation of the Deep Borehole Heat Exchanger (DBHE), it becomes imperative to quantitatively evaluate its long-term performance and sustainability. This work introduces a pilot DBHE project in Xi’an, along with the 500-h in-situ monitored data, which is used to validate the 3D numerical model established and simulated in the OpenGeoSys (OGS) software. Based on the validated model, a series of extended scenarios are executed to evaluate the influence of design and operational parameters on the long-term performance and sustainability of the DBHE system. The results show that the drilling depth is the most significant factor that influences long-term performance. On the contrary, pipe diameter and inner pipe thermal conductivity have a very limited impact. A comprehensive evaluation is suggested to determine operational flow rates in real projects while considering the energy consumption by the circulation pump. Moreover, the heat extraction performance and energy analysis of the DBHE coupled with a geothermal heat pump under intermittent operation are also investigated. With a fixed daily heating demand, a longer daily operating time results in lower circulating temperature drops, which is advantageous for the heat pump’s energy efficiency in long-term operation

Multi-faceted performance analysis and optimization of a hybrid deep borehole heat exchanger heating system with latent heat thermal energy storage

Deep borehole heat exchangers (DBHEs) coupled with heat pump systems present a promising solution for building space heating. However, conventional heating systems have limited demand flexibility and ignored the potential of direct heating using DBHEs. Thus, this study proposed a hybrid DBHE heating system by integrating latent heat thermal energy storage (LHTES) and borehole direct heating (BDH), and evaluated its performance in terms of energy, exergy, economy, and flexibility. This work aimed to achieve a matching operation between the LHTES and the heat pump and quantify the performance improvement potential of the hybrid system. Firstly, a thermodynamic analysis was carried out based on a pilot project, showing that the seasonal performance factor (SPF) of the system can reach 4.3 under the high-temperature heat storage mode, with a 45.5% improvement in exergy efficiency. Based on the field-measured data, a transient model of the hybrid system was developed using TRNSYS and MATLAB. With the established model, the single and interactive impacts of multiple critical parameters on the system performance were explored. Subsequently, a multi-objective optimization was performed using artificial neural networks and a genetic algorithm by considering several scenarios with different geographical locations and electricity tariffs. The optimization results revealed a trade-off between the levelized cost of energy (LCOE) and the flexibility factor, both of which were highly sensitive to the tank volume of the LHTES. The case studies showed that the LCOE of the optimized hybrid system was decreased by up to 8.5%, while the SPF, exergy efficiency, and flexibility factor were improved by up to 20.3%, 3.0%, and 998.7% respectively, in comparison with the conventional system. Compared with the hybrid system without using LHTES, integrating LHTES led to a decrease in LCOE by up to 5.0% and an increase in SPF by up to 3.8%. This study demonstrated the potential of using such hybrid systems for building heating decarbonization