Natural Cold Energy Research Articles

Utilizing waste heat from natural gas engine and LNG cold energy to meet heat-electric-cold demands of carbon capture and storage for ship decarbonization: Design, optimization and 4E analysis

The MEPC 80 session has adopted the revised IMO GHG Strategy, in which the stricter decarbonizing targets have been proposed. Carbon capture and storage (CCS) technologies show significantly excellent to reduce carbon emissions for maritime application, of which the high energy demands were neglected in the majority of past studies. Therefore, we propose a novel integration of natural gas engine, CCS, organic Rankine cycle (ORC) and power turbine (PT). Exhaust gas bypassing strategy is used to improve performances of engine at low/medium loads, which enters PT to generate power. The waste heat from engine is fully used for CCS by cold, heat and power. The comparison of different absorbents in CCS system is conducted, including monoethanolamine and piperazine solutions, showing that carbon capture rate can be achieved by 61.40–92.95% at engine load of 110-50% for piperazine solution, while that can be achieved by 84.81–97.64% for monoethanolamine solution. Additionally, the CO2 storage conditions are also compared and analyzed. The remaining power output can reach 98 kW and 108 kW at CO2 compression pressure of 12 bar and 23 bar, respectively. Furthermore, we show the CO2 capture costs of 124.03 $/tCO2 can be achieved at CO2 compression pressure of 12 bar and piperazine solution application. The proposed system can also achieve 57.3% of EEDI drop for a general cargo ship.

Remediation of large-scale model experiment for heavy metal contaminated clayey soil: An optimized mass transfer process strategy of freeze-thaw and washing

To reduce the limitations of the chemical washing method due to soil texture, the freezing technique has been used to enhance the mass transfer efficiency between the eluent and heavy metal contaminants. With the optimized water supplement and cooling conditions, a large-scale model experiment was conducted. Results show that the optimized method is prone to enhancing the eluent intake of clayey soil, leading to an increase in the amount of soil frost heave, which has a feedback effect by breaking the soil structure and enhancing the eluent intake. The synergistic effect of the two is responsible for the improvement of washing efficiency. In addition, after four freeze-thaw and washing cycles, the total removal rates of the metallic elements Pb and Cd reach 58.73% and 69.04%, respectively, satisfying the soil environmental quality standard. The soil bioavailability is effectively reduced by alternating the eluent with ethylenediaminetetraacetic acid (EDTA) and water, thereby reducing the bioavailability of Pb and Cd by 66.01% and 74.18%, respectively. This remediation strategy for heavy metals in clayey soils utilizes alternate freezing and thawing (natural cold energy) in seasonally frozen regions, which is beneficial for constructing an ecological civilization and protecting the environment.

Feasibility study on natural cold energy utilization in negative temperature underground space rock mass in permafrost region of northeast China

This study aims to investigate the possibility of using natural cold energy to establish a negative temperature space in northeast China by combining previous studies on natural cold energy and the ground temperature data obtained in northeast China. The temperature field changes of different rock masses after joining different depths of the subsurface space were simulated and analyzed by the finite element software COMSOL, exploring the feasibility of establishing underground spaces that maintain a temperature below 0 °C. The numerical simulation results show that the maximum melting depths of granite, limestone and basalt rocks are −6.4 m, −7.85 m and −5.34 m after adding underground space in the Genhe area under the proposed conditions. The temperature in the underground space is lower than the initial setting temperature after a year of temperature change influence, this indicates a surplus of cold energy, Therefore, the goal of maintaining negative temperature in the underground space year-round with zero energy consumption in the Genhe region is feasible. This paper provides new ideas for the utilization of cold resources in China and helps to better achieve the goal of sustainable development.

Heat transfer and cold energy capacity properties of crushed-rock layer in cold sandy regions

Addressing the impact of climate warming and anthropic activities, crushed-rock layer (CRL) is a zero-carbon emission technology by using natural cold air to protect infrastructures in permafrost regions. But in cold sandy environment, the issue of its cold energy capacity on account of aeolian sand clogging needs to be solved. Based novel field experiments on Tibet Plateau, the dynamic evolution law and its controlling factors of natural cold energy accumulation of the CRL are quantitatively figured out. Results show that the initially open CRL had a strong forced convection of air in the first two winters, while the cooling effect was failure after the third winter. The filling of aeolian sand caused heat transfer mode of the CRL to change from forced convection to natural convection in cold season, losing the ability of “thermal semiconductor” aimed to mitigate permafrost degradation. The closed CRL represented weak natural convection in cold season and thermal insulation in warm season, which had better long-term cooling effectiveness than other conditions in the aeolian environment. As the thickness of the aeolian sand filling increased, the maximum Rayleigh number and natural convection time of the closed CRL decreased. Accumulation of cooling energy in cold season and thermal insulation in warm season were positive correlation with thickness of porous media layer. It was not recommended to solely adopt crushed rock embankment or crushed rock revetment in aeolian sand environment and regions with higher annual average temperature. The findings solved the scientific evaluation issue of cold energy storage capacity of CRL, and provided constructive engineering implications for its efficient application.

Operational characteristics of oscillating heat pipe at sub-zero temperature for cold energy storage

This study first suggested a natural cold energy storage based on oscillating heat pipe (OHP) and presented the experimental investigation on the operational characteristics of the OHP at sub-zero temperatures for cold energy production. In the present experiment, the OHP was manufactured using a copper meandering tube with inner diameter of 2 mm and 5-turns, and R-134a was used as the working fluid. The manufactured OHP-based cold energy storage module was put into the temperature-controlled cooling chamber and the cold energy storage performance was evaluated at various low ambient temperature conditions. The thermal resistance of the OHP had a minimum value of 0.18–0.23 K/W regardless of the ambient temperature change. However, the lower ambient temperature caused significant thermal resistance decrease at water-ice temperature of 0 °C and the minimum thermal resistance was 1.18 K/W at the lowest ambient temperature of -20 °C. When the cold energy was stored in the final form of ice, the present OHP module could store the total maximum amount of cold heat of 2,784 kJ, consisting of sensible heat of 662 kJ and latent heat of 2,345 kJ at the lowest ambient temperature of -20 °C. It was concluded that the lower ambient temperature causes the stable and higher thermal performance of the OHP which increases the amount of stored cold heat by sensible heat and makes the OHP module possible to produce the cold heat more quickly.

Experimental Investigation of Heat Transfer and Flow Characteristics of Split Natural Cooling System for Data Center Based on Micro Heat Pipe Array

This paper presents a new type of split natural cooling system that maximizes the use of natural cold energy to significantly reduce the power consumption of the air conditioning system in data centers. A split natural cooling system module, which consisted of indoor and outdoor heat exchanger based on micro heat pipe arrays connected by liquid circulation system, was selected for experimental research. The heat transfer process and flow characteristics were analyzed under different outdoor environment temperatures, air and water flow rates, and different ratios of heat transfer components (N) of indoor and outdoor heat exchangers. To improve the utilization of natural cold energy, two kinds of heat dissipation conditions, namely room and heat channel-based, were proposed. The indoor temperature of two conditions at 28 °C and 38 °C were simulated in the laboratory at constant temperature-humidity, respectively. Results indicated that the air flow rate had a greater influence on the heat transfer performance than the water flow rate. The pressure drop of the air and water sides was at a lower level, and the fitting curve of the pressure drop was obtained to provide a reference for the heat exchanger design and equipment selection. When the ratio of heat transfer components (N) of the indoor and outdoor heat exchanger was approximately 0.75, the split natural cooling system showed optimal comprehensive performance. Under heat channel-based conditions, the maximum heat transfer rate reached 12.4 kW, and the maximum energy efficiency ratio was 17.15; the maximum heat transfer rate and the maximum energy efficiency ratio increased by 42.5% and 22.64% compared with the room-based condition, respectively. The fitting curve of the energy efficiency ratio was calculated under different outdoor temperatures at two heat dissipation conditions.

Performance, applicability, and optimization of a new slope cooling and protection structure for road embankment over warm permafrost

How to deal with the issues that crushed-rock revetment embankments are facing, such as inadequate cooling, sand-filling, and rock-weathering, is of importance for the integrity and safe service of roadways built on warm permafrost (> −1.0 °C) in the Tibet Plateau. In this study, a new slope cooling and protection structure (SCPS) was developed and a field experiment was implemented in the plateau permafrost zone to examine its cooling effect on permafrost stratum. Numerical simulations were then conducted to evaluate its cooling applicability in different road embankments and to optimize the new structure for further application in highway embankments with a wider pavement based on a validated convection heat transfer model. The results indicate that the new SCPS can produce an effective cooling process on the embankment slopes and the underlying permafrost. This caused an evident decrease in permafrost temperature at the subgrade shoulders and a significant elevation of the permafrost table below it. The intensified convection cooling in winter and good thermal insulation in summer generate the excellent cooling of the SCPS. However, the cooling range of SCPS is limited for a wide highway embankment. The highly endothermic asphalt surface makes it difficult for the SCPS to cool the embankment core effectively. To enhance the cooling adaptability, an optimized structure combining insulation and the SCPS proved that it can significantly expand the cooling scope to the embankment core and further raise the permafrost table beneath a wider embankment. This study confirms the application of the new SCPS as a highly efficient technique for maintaining the integrity of narrow railway embankments, examines its possible utilization in wider highway embankments, and promotes the efficient use of the natural cold energy in the plateau permafrost zones.

Simulation study on performance of data center air-conditioning system with novel evaporative condenser

Maximizing utilization of natural cold energy has become the key to reduce the energy consumption of data center air-conditioning system. A new type of evaporative condenser with water-cooled condensation is proposed and used in the data center composite air conditioning system. The model of air conditioning system is established and verified by the experimental platform. The simulation results show that although the coefficient of performance (COP) of the evaporative cooling heat pipe mode is reduced by 0.88% on average by the proposed evaporative condenser, the upper limit of temperature operation of this mode is raised from the original 15 °C to 17 °C. The heat pipe mode has been extended throughout the year, and the advantages of energy saving have been fully utilized. For the evaporative cooling vapor compression mode. The proposed evaporative condenser can reduce the energy of the composite system, and the COP is increased by 9.82% on average, showing high operating performance.

Thermal Performance and Energy Saving Analysis of Indoor Air–Water Heat Exchanger Based on Micro Heat Pipe Array for Data Center

According to the temperature regulations and high energy consumption of air conditioning (AC) system in data centers (DCs), natural cold energy becomes the focus of energy saving in data center in winter and transition season. A new type of air–water heat exchanger (AWHE) for the indoor side of DCs was designed to use natural cold energy in order to reduce the power consumption of AC. The AWHE applied micro-heat pipe arrays (MHPAs) with serrated fins on its surface to enhance heat transfer. The performance of MHPA-AWHE for different inlet water temperatures, water and air flow rates was investigated, respectively. The results showed that the maximum efficiency of the heat exchanger was 81.4% by using the effectiveness number of transfer units (ε-NTU) method. When the max air flow rate was 3000 m3/h and the water inlet temperature was 5 °C, the maximum heat transfer rate was 9.29 kW. The maximum pressure drop of the air side and water side were 339.8 Pa and 8.86 kPa, respectively. The comprehensive evaluation index j/f1/2 of the MHPA-AWHE increased by 10.8% compared to the plate–fin heat exchanger with louvered fins. The energy saving characteristics of an example DCs in Beijing was analyzed, and when the air flow rate was 2500 m3/h and the number of MHPA-AWHE modules was five, the minimum payback period of the MHPA-AWHE system was 2.3 years, which was the shortest and the most economical recorded. The maximum comprehensive energy efficiency ratio (EER) of the system after the transformation was 21.8, the electric power reduced by 28.3% compared to the system before the transformation, and the control strategy was carried out. The comprehensive performance provides a reference for MHPA-AWHE application in data centers.

Experimental study on the thermal characteristics of micro channel separate heat pipe respect to different filling ratio

A micro channel separate heat pipe (MCSHP) that can use natural cold energy was developed to reduce the cooling energy consumptions of telecommunications stations (TSs). Experimental investigations of exploring the optimal refrigerant filling ratio of MCSHP under different outdoor conditions and flow rates were presented. R22 was used as the working fluid. Various refrigerant filling ratios were tested in an enthalpy difference laboratory (EDL) in order to determine the optimal thermal performance for the exterior space temperature range from 8°C to 23°C and the air volume flow rate range from 1712m3/h to 2980m3/h. In addition, transient and steady-state performance under the optimal refrigerant filling ratio of the MCSHP was studied. As a result of experiments, the optimal refrigerant filling ratio was found in the range from 88% to 101% for different exterior conditions and airflow rates. For the optimal refrigerant filling ratio, the startup time was about 1100s and then the refrigerant pressures entered a steady state. The cooling capacity and energy efficiency ratio (EER) increased with increasing temperature difference between the indoor and the outdoor; these values were high to 7440W and 23, respectively, at temperature difference 20°C. The results are useful for the design and operational control of the MCSHP for TSs.

A seasonal cold storage system based on separate type heat pipe for sustainable building cooling

Seasonal cold storage is a high-efficient and environmental-friendly technique that uses the stored natural cold energy in winter (e.g., snow, ice or cold ambient air) for free-cooling in summer. This paper presents a seasonal cold storage system that uses separate type heat pipes to charge the cold energy from ambient air in winter automatically, without consuming any energy. The charged cold energy is stored in the form of ice in an insulated tank and is extracted as chilled water for cooling supply in summer, which help to reduce the chiller running time and reduce the associated electricity consumption and greenhouse gas emission significantly. A quasi-steady two-dimensional mathematical model of the system is developed for characterizing the dynamic performance of ice growth (i.e., cold charging). The model is validated using the field measurement data from an ice charging experiment conducted in Beijing. The impacts of various affecting factors, including the weather data and the key parameters of heat pipes, on the charging performance of the cold storage system are analyzed. The effectiveness and sustainability of the proposed system for cooling are demonstrated through a case study of a kindergarten building in Beijing.

Effects of Different Storage on Qualities of Adzuki and Red Kidney Beans

<p>This is the first study to report the effects of frozen soil storage on adzuki and red kidney beans. Adzuki and red kidney beans were stored for 15 months in polyethylene or paper bags under three different conditions: natural cold energy storage in frozen soil, storage in a freezer at -20 °C, and storage at a constant temperature of 25 °C. Samples were collected from every treatment group every 3 months, and qualities related to processing (bean paste yield and cooked bean hardness), seed moisture content, one-hundred seed weight, seed density, and sample physical properties (electrical conductivity and soluble solid content) were evaluated. Frozen soil storage resulted in the least deterioration of important qualities in adzuki and red kidney beans. We also showed that the electrical conductivity value and soluble solid content of the liquid used for soaking beans can be used to evaluate the processing suitability of cooked beans.<strong> </strong></p>

Energy-efficient air conditioning system with combination of radiant cooling and periodic total heat exchanger

The main thrust of this paper is directed toward a novel air conditioning system that can maintain a healthy indoor environment and be energy-efficient. This system consists of a low-temperature regenerative periodic total heat exchanger, radiant ceiling-cooling coil, and conventional air conditioner. The natural cold energy of the tap water in the cooling coil provides comfortable and uniform cooling, and the desiccant-packed bed in the total heat exchanger recovers the indoor energy to handle the fresh air. The performance of each component is discussed, and the actual performance of the whole system is investigated in an office at the Taipei Water Department. The results indicate that using a radiant ceiling-cooling coil to precool the indoor environment enables the traditional window-type air conditioner to reduce two-thirds of the original operating time. In addition, the test of the whole system was conducted in the same office, and it was observed that using this system to handle the incoming air could save 13%–19% of the energy consumption per month during a year-round operation compared to directly introducing untreated fresh air.

Seasonal underground cold energy storage conception and its experimental study

AbstractA novel concept for energy use is presented, namely, the natural cold energy in the air in winter in cold climates is stored in ground and then extracted in summer directly for air conditioning. To verify this concept an experimental system for storing natural cold energy in ground was set up. The characteristics of using the ground to store natural cold energy in winter are investigated, and the operating modes of the system are discussed. During the whole cold storage experiment, the cold capacity stored in ground was 16 025·6 MJ and an energy efficiency ratio of 13·1 was gained. The temperatures of the soil in the cold storage wells (boreholes) and around them both decreased very markedly. These results show that in cold climates the concept of using ground to store the natural cold energy from the winter air is feasible.

Characteristics of Heat Balance in a Building for Farm Product Storage using the Latent Heat of Ice as Natural Cold Energy

Characteristics of Heat Balance in a Building for Farm Product Storage using the Latent Heat of Ice as Natural Cold Energy

Distribution and Regional Classification of Meteorological Resources Concerning Natural Cold Energy in Hokkaido, Japan.

To clarify the distribution of natural cold energy such as the resources of snow, ice, and frozen soil, we analyzed the meteorological data, and made regional classifications in Hokkaido. From the results, we considered each region’s potential for effective use of cold energy resources. Principal Component Analysis (PCA) was performed using the parameters of the meteorological resources related to cold energy, and Cluster Analysis (CA) was performed using the principal score (PS) to define regional classification. Consequently, the first principal component (PC1) which showed cold and continuous-snow-cover duration, and the second principal component (PC2) which showed snowfall and sunshine duration were obtained. From the results of CA, we could classify Hokkaido into 16 regions. In general, the cold resources such as snow and ice are kept in storages until early summer and used as cold energy in summer. Therefore high summer temperatures negatively affect cold energy utilization. So we executed the PCA and CA using the parameters of the meteorological resources in summer. As a result, PC1, PC2, and PC3 showed the information of temperature, wind speed and temperature rise in the daytime, and precipitation, respectively. From results of CA, we could classify Hokkaido into 19 regions. From these results, it was considered that the utilization of snow, ice, and frozen soil was advantageous in the Japan Sea side region, inland area, and eastern Pacific Ocean side region, respectively.

"夏の雪"雪氷冷熱エネルギー資源(再生可能エネルギー,<メカライフ特集>エネルギー)

"夏の雪"雪氷冷熱エネルギー資源(再生可能エネルギー,<メカライフ特集>エネルギー)

The application of auto-temperature-controlled ventilation embankment in Qinghai-Tibet Railway

Auto-temperature-controlled ventilation embankment is an effective engineering measure for “cooling roadbed”. Practice proves that this new method can sufficiently make use of natural cold energy. It has the advantages of higher efficiency, better cooling effect and feasibility in engineering practice, and wider application in various environment, etc. And also, it is comparatively cheap in project cost. Through practice in the field for half a year, the testing results show that, with the application of auto-temperature-controlled system, the artificial permafrost table has been raised by 65 cm. The artificial permafrost table was basically at the embankment bottom, and the action of freeze-thaw circle on engineering stability was effectively avoided. In the month with highest ground temperature, in the scope with 1–4 m in depth, including the majority of the embankment and the upper part in the original seasonal layer, the ground temperature decreased by 0.7°C. Through thermal flux calculation in the original seasonal layer, in the month with the maximum thermal flux coming into permafrost, it is found that the thermal flux reduces nearly by half. Coming into the cooling period for nearly a month, the ground temperature in entire auto-temperature-controlled embankment is close to zero, and the foundation is at negative temperature. But in a large region in the embankment and foundation the ground temperature was over 0°C and varied from 0°C to0.39°C in ordinary ventilation embankment.

Thermal characteristics of manganese (II) nitrate hexahydrate as a phase change material for cooling systems

The imbalance of electrical demand in summer due to cooling system demand is a big problem in many countries. One promising solution is shifting peak demand from early afternoon to night by utilizing natural cold energy resources such as cool outside air during night or running a refrigerator driven by midnight power. In these cases, using the thermal energy storage (TES) of phase change material (PCM) which has a melting point from 15 to 25 °C is one of the most effective ideas. However, few suitable PCMs for this temperature range are at present commercially available. This study aims to evaluate the potential of Mn(NO 3) 2 · 6H 2O (manganese (II) nitrate hexahydrate) as a new PCM for the TES of cooling systems. First, experiments on the modulation of the melting point of Mn(NO 3) 2 · 6H 2O and reduction of supercooling were made by dissolving small amounts of salts in the material. Consequently, MnCl 2 · 4H 2O was found to have good performance with regard to both modulation of the melting temperature and the heat of fusion. Next, a thermal response test was carried out by using a small cylindrical vessel. Results showed that the required temperature levels for charging and discharging the heat of this mixture were clarified. In addition, the price and safety of this material as a PCM are discussed.

The Study of Heat Exchange between Air and Snow Block with a Vertical Hole. The Effect of Air Flow Rate on Heat Exchange Characteristic.

It is very important to use many kinds of natural energy resources to keep environment clean and to reduce the energy consumption. Many simple and skilful methods to utilize the natural energy have to be developed. The authors have been proposing to utilize snow stored till summer as one of the natural cold and clean energy resources. In this study, the authors investigated the characteristics of direct heat exchange between hot air and snow block with a vertical hole. This heat transfer model, so called as the snow cooling system, may be applied to various air-conditioning systems of conventional living room and so on. As the heat transfer process of this model is very complicated because the shape of the snow block changes by the progress of melting, the characteristics of the direct heat exchange were investigated by the experiment with a model of practical scale. The outlet air temperature through the snow hole and snow melting process were measured for various air flow rates at constant inlet air temperature 30°C. Experimental results show that the outlet air temperature from the snow cooling system was almost constant and enough lower to use for the actual air conditioning situations. Heat transfer coefficients on the snow surfaces of top plane, bottom plane and side wall of the snow hole were clear by those experimental results, and the correlative equations between the overall Nusselt number and the Reynolds number are presented for three surfaces mentioned above.