Abstract

With the increase in the heat flux density of data centers, liquid cooling of data centers is becoming increasingly important. A cooling tower is typically employed in liquid cooling systems and its cooling performance is affected by ambient temperature and relative humidity. In this study, we analyze the effects of these factors on cooling performance as well as power consumption, which have previously not been studied in detail. For this purpose, we built a 4.8 kW data server cold-water system and used a fin-type water-cooled radiator for heat dissipation. The energy consumption of the cooling system under different ambient temperature and relative humidity conditions was simulated and analyzed using TRNSYS simulation software. Assuming that the chip operating temperature is 70 °C, when the ambient temperature increases from 5 °C to 30 °C, and the ambient relative humidity increases from 40 % to 80 %, the optimal primary cooling water flow and the secondary cooling water flow increase accordingly, and the corresponding energy consumption of the cooling system increases. By considering the optimal flow rates, we found that the power usage effectiveness (PUE) is in the range 1.14–1.21.

Abstract

The building energy system faces uncertainties from renewable energy power generation and energy demand, and the design using deterministic method will introduce the risk of suboptimal decisions. In this paper, a stochastic programming model is formulated for the building energy system planning problem under source and load uncertainties. Facing the computational burden caused by massive stochastic annual scenarios, a two-level scenario reduction method of typical annual scenario reduction and typical daily scenario reduction is proposed, which ensures the solvability of the stochastic programming model and takes into account the uncertainty of design boundary. To illustrate the model’s application, the design of an integrated energy system for an industrial park is investigated. The results show that the stochastic planning method can maximize the life-cycle economic benefit of the integrated energy system under uncertain design boundaries comparing with the deterministic planning method. In addition, the flexibility of the energy storage system can resist a certain degree of load forecasting deviation and improve energy supply reliability of the system.

Abstract

In this study, the denitrification performance of steel slag modified by manganese slag was studied. Different proportions of steel slag and electrolytic manganese anode mud mixtures were configured. The different proportions of the mixture would have varied physical and chemical properties. SS1+EMAM2 catalyst showed the nearly 100% NOx removal efficiency at 175°C. The specific surface area of steel slag is enhanced dramatically after modification by EMAM. Adding EMAM enhanced the weak acid sites and Brønsted-acid sites on the catalyst surface, resulting in a higher low-temperature SCR activity.

Abstract

To reduce CO2 emissions in response to global climate change, depleted shale reservoirs are ideal for long-term carbon storage. However, hydraulic fracturing measures and large injections of carbon dioxide can cause faults and fractures to reactivate, causing gas migration and leakage. In this paper, a partially permeable boundary is introduced to characterize the region where CO2 leakage occurs. This study proposes a model for predicting CO2 sequestration potential in novel depleted shale gas reservoirs considering gas adsorption, diffusion, and gas leakage. Furthermore, the multi-scale transport model is solved using Laplace transformation and potential energy superposition and is verified using numerical simulations based on the field data from the Marcellus Shale. The results show that the analytical solutions of the proposed model are in good agreement with the results of conventional numerical simulations. Moreover, shale reservoirs with high Langmuir volume and low Langmuir pressure are ideal for CO2 storage, with larger CO2 storage capacity and minor gas leakage. The findings have tremendous significance for the potential utilization of depleted shale gas reservoirs, considering the leakage of CO2.

Abstract

Lithium-ion batteries generate a lot of heat during discharge, which can cause the risk of excessive temperature and accelerate the capacity fading rate. Cooling the battery through the latent heat storage of hydrated salt is a good choice. In this study, hydrated salts mixed with sodium acetate trihydrate and disodium hydrogen phosphate dodecahydrate were modified to change the phase change temperature and enthalpy, and then the battery cooling modules were prepared by using modified composite phase change material as a filler and copper foam as a support matrix. The thermal performance of the modified composite phase change material was tested and analyzed by differential scanning calorimetry (DSC) test. The DSC analysis showed that the composite phase change material with 5wt% sodium acetate trihydrate had the best performance, the enthalpy was 278.9 kJ/kg and its phase change temperature was 46.9 ℃. The results of the surface temperature measurement experiments of the cooling module on the battery showed that the cooling module can effectively reduce the temperature in the discharge process and the maximum temperature reduction can be up to 9 ℃. The lowest temperature was 55 ℃ with the battery cooling module on the discharge at 1.5C.