| 1. |
- Li, Houpei, et al.
(författare)
-
Matching characteristics and AC performance of the photovoltaic-driven air conditioning system
- 2023
-
Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 264
-
Tidskriftsartikel (refereegranskat)abstract
- Photovoltaic-driven Air Conditioning systems (PVAC) use local electricity generated by distributed Photovoltaic (PV) to drive Air Conditioners (AC). Both the AC cooling load and the PV electricity generation are affected by solar radiation. The PV generation cannot dynamically supply the AC power consumption during the operation. In this study, the matching characteristics of a PVAC were investigated using a case in a 207.34 m2 office room. A coupled simulation model was built, which integrated with a building model, a PV calculation model, an AC model, and a control strategy. More specifically, the AC was modeled with two heat exchangers, a compressor, and a throttling device. Both the building and the PV were simulated in EnergyPlus. The AC compressor speed was controlled so the AC power consumption could match the PV generation when the indoor temperature was within the temperature control zone. The daily matching characteristics of PVAC were strongly affected by the PV capacity. The results showed that the PV factor (PVF) should be set to 1 in order to match the AC and PV power and maximize the AC efficiency. A battery factor of at least 0.7 could ensure the grid flexibility. Finally, the optimized design of PV, battery, and AC capacities was suggested.
|
|
| 2. |
- Wang, Fu, et al.
(författare)
-
Experimental study of solar assisted post-combustion carbon capture
- 2015
-
Ingår i: CLEAN, EFFICIENT AND AFFORDABLE ENERGY FOR A SUSTAINABLE FUTURE. - : Elsevier BV. ; 75, s. 2246-2252
-
Konferensbidrag (refereegranskat)abstract
- Solar-assisted post-combustion carbon capture system is studied to compensate the energy penalty of coal-fired plant due to absorbent regeneration. The system is highly integrated with the amine-based carbon capture process coupled with solar thermal sub-system. The dynamic performance is largely affected by the variations of parameters and the fluctuations in solar collectors. An experimental facility of solar-assisted chemical absorption pilot with two types of collectors (parabolic trough and linear Fresnel) was constructed in this study. The impacts on the absorbent regeneration performance were studied on the dynamic variation of the solar heat and the operating temperature of the reboiler. The results show that an optimum ration of liquid-to-gas of 2.5-3.0 was determined at the lowest of the required regeneration energy. The study suggests that a better understanding of the key parameters associated with both capture process as well as the solar assisted sub-system if of importance for the overall operation and control. (C) 2015 Published by Elsevier Ltd.
|
|
| 3. |
- Bai, Fan, et al.
(författare)
-
Application of similarity theory in modeling the output characteristics of proton exchange membrane fuel cell
- 2021
-
Ingår i: International journal of hydrogen energy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-3199 .- 1879-3487. ; 46:74, s. 36940-36953
-
Tidskriftsartikel (refereegranskat)abstract
- Proton Exchange Membrane Fuel Cell (PEMFC) has attracted widespread interest. In the present work, similarity analysis is adopted for a three-dimensional single-phase isothermal model of PEMFC to derive similarity criteria. Seven kinds of input criteria (Pi(1) similar to Pi(7)) are obtained, relevant to the fluid flow, pressure drop, flow resistance in a porous medium, activity loss, diffusion mass transfer, convective mass transfer and ohmic loss in PEMFC respectively. Dimensionless voltage and dimensionless current density are defined as two output criteria. Numerical verifications show that if the seven criteria keep their individual values with their components vary in a wide range, the dimensionless polarization curves keep the same with a deviation about 1%, showing the validity and feasibility of the present analysis. From the effect on the dimensionless polarization curve, sensibility analysis shows that the seven criteria can be divided into three categories: strong (Pi(4) and Pi(7), -94.9% similar to +349.2%), mild to minor (Pi(5) and Pi(6), -4.5% similar to +5.0%), and negligible (Pi(1), Pi(2) and Pi(3), -1.2% similar to +1.1%). The similarity analysis approach can greatly save computation time in modeling the output characteristics of PEMFC. (C) 2021 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.
|
|
| 4. |
- Jiyang, Xie, et al.
(författare)
-
Analysis of Key Factors in Heat Demand Prediction with Neural Networks
- 2017
-
Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 105, s. 2965-2970
-
Tidskriftsartikel (refereegranskat)abstract
- The development of heat metering has promoted the development of statistic models for the prediction of heat demand, due to the large amount of available data, or big data. Weather data have been commonly used as input in such statistic models. In order to understand the impacts of direct solar radiance and wind speed on the model performance comprehensively, a model based on Elman neural networks (ENN) was adopted, of which the results can help heat producers to optimize their production and thus mitigate costs. Compared with the measured heat demand, the introduction of wind speed and direct solar radiation has opposite impacts on the performance of ENN and the inclusion of wind speed can improve the prediction accuracy of ENN. However, ENN cannot benefit from the introduction of both wind speed and direct solar radiation simultaneously.
|
|
| 5. |
- Liu, Shengchun, et al.
(författare)
-
Alternative positions of internal heat exchanger for CO2 booster refrigeration system : Thermodynamic analysis and annual thermal performance evaluation
- 2021
-
Ingår i: International journal of refrigeration. - : ELSEVIER SCI LTD. - 0140-7007 .- 1879-2081. ; 131, s. 1016-1028
-
Tidskriftsartikel (refereegranskat)abstract
- Refrigeration systems running on transcritical CO2 cycle are considered an alternative to phase-down the use of hydrofluorocarbons (HFCs) in response to the Kigali Amendment. Responding to the need to improve the efficiency of CO2 booster systems and to identify optimum system designs, thermodynamic models of three booster systems are proposed with the use of an internal heat exchanger (IHX). Findings from this study suggest that placing the IHX with a low-temperature fluid side at the suction line of high pressure stage compressor and high-temperature fluid side at the outlet of gas cooler represents the most optimal approach in improving the coefficient of performance (COP) of the booster system. When operating in the transcritical conditions, the COP values can be improved by 6.35% at the IHX thermal effectiveness of 0.8 and by 6.48% at the ratio of medium temperature load to low temperature load of 6. Using IHX can significantly reduce the compressor discharge pressure, which can be reduced by 0.55 MPa at the ambient temperature of 40 degrees C. Furthermore, by adding IHX, the annual performance factor of CO2 system can be improved significantly by 1.68% and the annual total power consumption can be decreased by 6.48% in the tropical climate. It can be concluded that IHX can improve the COP values of a booster system when operating in the subtropical and tropical regions.
|
|
| 6. |
|
|
