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Transcriptional feedback loops are central to the architecture of eukaryotic circadian clocks. Models of the Arabidopsis thaliana circadian clock have emphasized transcriptional repressore, but recently, Myb-like REVEILLE (RVE) transcription factors have been established as transcriptional activators of central clock components, including PSEUDO-RESPONSE REGULATORS (PRR5) and TIMING OF CAB EXPRESSION1 (TOC1). We show here that NIGHT LIGHT-INDUCIBLE AND CLOCK-REGULATEDI (LNK1) and LNK2, members of a small family of four LNK proteins, dynamically interact with morningexpressed oscillator components, including RVE4 and RVE8. Mutational disruption of LNK1 and LNK2 function prevents transcriptional activation of PRR5 by RVE8. The LNKs lack known DNA binding domains, yet LNK1 acts as a transcriptional activator in yeast and in planta. Chromatin immunoprecipitation shows that LNK1 is recruited to the PRR5 and TOC1 promoters in planta. We conclude that LNK1 is a transcriptional coactivator necessary for expression of the clock genes PRR5 and TOC1 through recruitment to their promoters via interaction with bona fide DNA binding proteins such as RVE4 and RVE8.

Key messageCCA1α and CCA1β protein variants respond to environmental light and temperature cues, and higher temperature promotes CCA1β protein production and causes its retention detectable in the cytoplasm.CIRCADIAN CLOCK ASSOCIATED1 (CCA1), as the core transcription factor of circadian clock, is involved in the regulation of endogenous circadian rhythm in Arabidopsis. Previous studies have shown that CCA1 consists of two abundant splice variants, fully spliced CCA1α and intron-retaining CCA1β. CCA1β is believed to form a nonfunctional heterodimer with CCA1α and its closed-related homolog LHY. Many studies have established that CCA1β is a transcription product, while how CCA1β protein is produced and how two CCA1 isoforms respond to environmental cues have not been elucidated. In this study, we identified CCA1α and CCA1β protein variants under different photoperiods with warm or cold temperature cycles, respectively. Our results showed that CCA1 protein production is regulated by prolonged light exposure and warm temperature. The protein levels of CCA1α and CCA1β peak in the morning, but the detection of CCA1β is dependent on immunoprecipitation enrichment at 22 °C. Higher temperature of 37 °C promotes CCA1β protein production and causes its retention to be detectable in the cytoplasm. Overall, our results indicate that two splice variants of the CCA1 protein respond to environmental light and temperature signals and may, therefore, maintain the circadian rhythms and give individuals the ability to adapt to environment.

The single-well enhanced geothermal system (SEGS) is an innovative approach designed to overcome the limitations of traditional deep borehole heat exchangers (DBHEs). It achieves this by modifying the well structure and circulating working fluid through an engineered reservoir to enhance heat transfer. This study presents a laboratory-scale experimental investigation of a SEGS analog to identify key performance determinants. The research explores the impacts of injection flow rate, injection temperature, and the initial temperature of the sandbox on the system’s thermal performance and temperature distribution into the sandbox. A series of experiments were conducted under different conditions, and the results were analyzed to determine the optimal operating parameters for maximizing heat extraction while minimizing temperature decay. The study also investigates the influence of injection–production spacing on the thermal breakthrough and the overall efficiency of the SEGS. Based on the observed trade-offs within the tested range, a flow rate of 0.4 m 3 /h, an injection temperature of 31 °C, and a spacing of 120 cm provided the best compromise between high heat extraction rate and stable production temperature. These findings provide foundational insights into SEGS thermal behavior and a basis for optimizing system design, supporting the development of sustainable geothermal energy solutions.

Open-loop borehole heat exchanger (OBHE) is a single well geothermal heat exchanger with an open-loop structure that can realize the geothermal energy extraction without mining the geothermal water. In this paper, a sandbox experiment is designed to simulate the convective heat transfer process in the reservoir area of OBHE. The mechanism of convective heat transfer in the reservoir area is studied, and the key factors that affect the convection heat transfer intensity are analyzed. The results show that the convection heat transfer of OBHE in the reservoir area is affected by both the driving effect of fluid flow inside the screen tube and the buoyancy effect. In the forward flow mode, the two effects have the opposite direction. While in the backward mode, the two effects have the same direction. The backward flow mode is more conducive to convective heat transfer. In addition, many factors influencing significantly the convective heat transfer of OBHE include inlet temperature, inlet flow rate, reservoir temperature, fluid flow direction and inner tube diameter.

Due to its deep utilization of geobrine and its high net power output, the binary-flashing cycle (BFC) is deemed to be the future geothermal energy power generation technology. The working fluids considered in present analysis are zeotropic mixtures (R245/R600a). The system thermodynamic model is built, and the energy and conventional and advanced exergy analyses are carried out to reveal the real optimization potential. It is demonstrated that the optimal ranges of R245fa mass fraction and working fluid dryness at the evaporator outlet are 0.30~0.50 and 0.40~0.60, considering the thermodynamic performance and the flammability of the zeotropic mixtures, simultaneously. Conventional exergy analysis indicates that the maximum exergy destruction occurs in the condenser, followed by the expander, evaporator, flashing tank, preheater, high-pressure pump and low-pressure pump. Meanwhile, the advanced exergy analysis reveals that the expander should be given the first priority for optimization, followed by the condenser and evaporator. The BFC has a large potential for improvement due to higher avoidable exergy destruction, about 48.6% of the total system exergy destruction can be reduced. Moreover, the interconnections among system components are not very strong, owing to small exogenous exergy destructions. It also demonstrates the effectiveness of advanced exergy analysis, and the approach can be extended to other energy conversion systems to maximize the energy and exergy savings for sustainable development.

Deep borehole heat exchanger (DBHE) technology does not depend on the existence of hot water reservoir and can be used in various regions. However, the heat extraction from DBHE can hardly be improved due to poor thermal conductivity of rocks. Here, a single-well enhanced geothermal system (SWEGS) is proposed, which has a larger heat-exchange area of artificial reservoir created by fracturing hydrothermal technology. We find that, due to heat convection between rocks and fluid, the extracted thermal output for SWEGS is 4772.73 kW, which is 10.64 times of that of DBHE. By changing the injection water temperature, volume flow rate, and artificial reservoir volume, it is easy to adjust the extracted thermal output to meet the requirement of building thermal loads varying with outdoor air temperature. Understanding these will enable us to better apply SWEGS technology and solve the fog and haze problem easily and efficiently.

The binary-flashing cycle (BFC) is supposed to be a promising technology for geothermal recovery due to the full use of geofluid. For further performance improvement, the potential of using mixtures of a hydrocarbon and a retardant in the BFC system is investigated. R245fa is selected as a retardant and blended with R600 to form zeotropic mixtures. With the thermal efficiency (ηth), exergy efficiency (ηex), net power output per ton geofluid (PRW), and exergy destruction rate (Ed) as evaluation indexes, the flowsheet modeling and optimization are conducted to explore the optimal compositions and operating parameters. It is revealed the optimal mass fraction of R600/R245fa is 0.44/0.56, at which the flammability of R600 is suppressed, the global warming potential (GWP) of R245fa is reduced. The maximum ηex and PRW are higher than those of component fluids. The maximum Ed occurs in the heat exchanger, which should be optimized. The recommended generation pressures are 1200–1430, 1240–1480, 1220–1460, and 1170–1420 kPa, respectively, for R600 mass fraction of 0.2, 0.4, 0.6, and 0.8. In addition, the flashing temperature is also optimized. Although the mixtures do not always yield superior performance, it is still beneficial to apply the mixtures to the BFC system through systematic consideration of safety and environmental friendliness.

To solve the problem of swelling and agglomeration of CaCl2 during the process of ammonia adsorption and improve the performance of mass transfer, we present a new method for the preparation of adsorbent. The CaCl2 is first immerged into sawdust by soaking method, then the composite adsorbent is prepared by carbonizing the mixture of CaCl2 and sawdust. The SEM image and elements analysis indicated that the new adsorbent has high porosity and uniform distribution of CaCl2 due to carbonization under temperature of 700°C. The performance testing of ammonia adsorption showed that under the conditions of evaporation temperature of −5°C and condensation temperature of 40°C, the ammonia uptake reaches 0.204, 0.253 and 0.285 kg/kg, the specific cooling power (SCP) is 868.96, 540.02 and 405.16 W/kg, and the average adsorption rate is 6.79×10−4, 4.22×10−4 and 3.17×10−4 kg/kg/s when the adsorption time is 5, 10 and 15 min, respectively. The problems of swelling and agglomeration of CaCl2 are solved.

Three kinds of commercial silica gels with pore size of 2–3, 4–7 and 8–10 nm respectively are used for preparing composite adsorbents by soaking them into the aqueous solution of calcium chloride. The test result indicates that both the water uptake and adsorption rate of composite adsorbents prepared from 4–7 and 8–10 nm silica gels improve greatly compared to pure silica gels, but they do not for 2–3 nm silica gels. The silica gel with pore size of 2–3 nm is not suitable for preparing the composite adsorbent by impregnation method due to the pore blockage because of the small pore size. The SCP and COP of the adsorption chiller with sample SA50 are 128.3 Wkg−1 and 0.27 respectively at the hot source temperature of 90 °C, which are largely superior to that of SA0. Hence using the composite adsorbent instead of the pure silica gel can reduce the size of the adsorption chiller.

Process heating constitutes a significant share of final energy consumption in the industrial sector around the world. In this paper, a high-temperature heat pump (HTHP) using flash tank vapor injection technology (FTVI) is proposed to develop low-temperature geothermal source for industrial process heating with temperature above 100°C. With heat sink output temperatures between 120°C and 150°C, the thermo-economic performance of the FTVI HTHP system using R1234ze(Z) as refrigerant is analyzed and also compared to the single-stage vapor compression (SSVC) system by employing the developed mathematical model. The coefficient of performance (COP), exergy efficiency (ηexe), net present value (NPV) and payback period (PBP) are used as performance indicators. The results show that under the typical working conditions, the COP and ηexe of FTVI HTHP system are 3.00 and 59.66%, respectively, and the corresponding NPV and PBP reach 8.13 × 106 CNY and 4.13 years, respectively. Under the high-temperature heating conditions, the thermo-economic performance of the FTVI HTHP system is significantly better than that of the SSVC system, and the larger the temperature lift, the greater the thermo-economic advantage of the FTVI HTHP system. Additionally, the FTVI HTHP system is more capable than the SSVC system in absorbing the financial risks associated with changes of electricity price and natural gas price.