| 1. |
- Dai, B., et al.
(författare)
-
Evaluation of transcritical CO 2 heat pump system integrated with mechanical subcooling by utilizing energy, exergy and economic methodologies for residential heating
- 2019
-
Ingår i: Energy Conversion and Management. - : Elsevier Ltd. - 0196-8904 .- 1879-2227. ; 192, s. 202-220
-
Tidskriftsartikel (refereegranskat)abstract
- A transcritical CO 2 heat pump (HP) system for residential space heating integrated with direct dedicated mechanical subcooling (DMS) is proposed, and mathematical models are developed to study the annual energetic and economic performances considering the influence of frosting. The operation characteristics by adopting different heating terminals used in five typical cities are also assessed. The results show a maximum coefficient of performance (COP) is achieved at the optimum discharge pressure and subcooling degree. The COP is promoted by 24.4% and the discharge pressure is decreased by 2.093 MPa at the ambient temperature of −10 °C and water supply/return temperature of 45/40 °C. The seasonal performance factor (SPF) is enhanced more noticeably for severe cold region. For the case of Harbin using floor-coil radiator (FCR) or normal fan-coil unit (N-FCU) as heating terminal, SPF is improved by 32.0%. The highest SPF is achieved when small temperature difference fan-coil unit (STD-FCU) is employed. The exergy efficiency can also be apparently improved, especially for the cities located in severe cold region and using FCR or N-FCU as heating terminal due to the reduction in throttling loss of CO 2 system. The purchased equipment cost and electricity cost of the CO 2 HP with DMS are both lower than those of traditional CO 2 heat pump system. The CO 2 HP DMS system using STD-FCU as heating terminal shows superior economical efficiency to traditional system, with levelized annual total cost reduced by 7.51–15.27%.
|
|
| 2. |
- Liu, S., et al.
(författare)
-
Performance analysis of two-stage compression transcritical CO2 refrigeration system with R290 mechanical subcooling unit
- 2019
-
Ingår i: Energy. - : Elsevier Ltd. - 0360-5442 .- 1873-6785. ; 189
-
Tidskriftsartikel (refereegranskat)abstract
- The use of carbon dioxide (CO2) as refrigerant is driven by the need to phase down the traditional synthetic refrigerant so as to mitigate the warming climate. In this study, the thermal performance of a two-stage compression transcritical CO2 refrigeration system with R290 mechanical subcooling unit is conducted. The goal is to obtain the maximum coefficient of performance (COP) of five different mechanical subcooling systems under the optimal subcooling temperature and compressor discharge pressure. The two-throttling and two-stage compression high-pressure mechanical subcooling system is found to have a higher COP. When the evaporation temperature is −30 °C, the COP of the two-throttling and two-stage compression high-pressure mechanical subcooling system is improved by 76.74%. The COP of the two-throttling and two-stage compression high-pressure mechanical subcooling system is 1.52 at an ambient temperature of 40 °C, which is 21.87% higher than that of the two-throttling and two-stage compression low-pressure mechanical subcooling system. The power consumption ratio of one-throttling and two-stage compression low-pressure mechanical subcooling system is significantly higher than that of other systems. From a comprehensive analysis of the proposed four systems, the two-throttling and two-stage compression high-pressure mechanical subcooling system has the best performance over all other systems.
|
|
| 3. |
- Pan, H., et al.
(författare)
-
Kinetic energy harvesting technologies for applications in land transportation : A comprehensive review
- 2021
-
Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 286
-
Tidskriftsartikel (refereegranskat)abstract
- The development of land transportation has effectively contributed to countries’ economic and social development. Roads, rails and vehicles have come into widespread use in transporting things from one location to another on land. However, much energy is dissipated in traditional land transportation, and this energy is worthy of being recovered. Many researchers in recent decades have presented different types of energy harvesting systems to harness this dissipated energy. Regenerative energy harvesting systems can convert dissipated energy into electricity for different applications. This paper is a comprehensive review of energy harvesting technologies for different applications in the land transportation. First, the commonly used energy harvesting technologies in land transportation are summarized. Second, different energy harvesting systems are presented in terms of designs, simulations, and experiments. Third, a common analysis of energy harvesting technologies is conducted to calculate and simulate the performance of these systems. Also, a comparison of the presented energy harvesting systems is conducted in various ways. Then different applications and energy utilizations of the energy harvesting systems are summarized. Moreover, research gaps and technical difficulties that remain unresolved are discussed, and some recommendations are made, which aim to be helpful for further research.
|
|
| 4. |
- Qi, Lingfei, et al.
(författare)
-
A review of vibration energy harvesting in rail transportation field
- 2022
-
Ingår i: iScience. - : Elsevier Inc.. - 2589-0042. ; 25:3
-
Forskningsöversikt (refereegranskat)abstract
- In this paper, we review, compare, and analyze previous studies on vibration energy harvesting and related technologies. First, the paper introduces the basic aspects of vibration energy acquisition in the railway environment, including vibration frequency, train speed, energy flow in the train, and vibration energy harvesting potential. Generally, the methods for scavenging vibration energy caused by passing trains can be divided into four categories: electromagnetic harvesters, piezoelectric harvesters, triboelectric harvesters, and hydraulic harvesters. The structure, output performance, merits, and disadvantages of different energy harvesting strategies are summarized and compared. The application of vibration energy harvesters is explained as supplying power to monitoring sensors on the line side and the vehicle side. Finally, the paper addresses the challenges and difficulties that have not been completely resolved in the current research literature, including system stability, durability, and economy. Some recommendations to fill these research gaps are put forward for further investigation.
|
|
| 5. |
- Song, J., et al.
(författare)
-
Parameter optimization analysis of rotary electromagnetic vibration energy harvester for performance enhancement under free vibration
- 2023
-
Ingår i: iScience. - : Elsevier Inc.. - 2589-0042. ; 26:10
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, three new important aspects of rotary electromagnetic vibration energy harvesting technology (RE-VEH) are concerned and investigated: (i) vibro-electric coupling mechanism of the RE-VEH system is studied through theoretical modeling; (ii) quantitative analysis of system parameters based on numerical simulation method is carried out for the optimal design of RE-VEH; and (iii) dynamic power output performance of the RE-VEH system in free vibration is discussed. The parameter adjusting methods of the RE-VEH system in free vibration mode are obtained through theoretical analysis and numerical simulation. The experimental results show that the power output performance of RE-VEH in free vibration mode matches the numerical simulation results. The simulation and experimental results show that the maximum voltage output and power output of the RE-VEH with different structure parameters under free vibration can be up to the level of 100∼101 V/watt. The above results indicate that RE-VEH in a free vibration environment has significant energy output performance.
|
|
