| 1. |
- Yan, A., et al.
(författare)
-
Hydraulic performance of a new district heating systems with distributed variable speed pumps
- 2013
-
Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 112, s. 876-885
-
Tidskriftsartikel (refereegranskat)abstract
- The application of distributed variable speed pumps (DVSP) in the district heating (DH) network has been considered as a technology improvement that has a potential of saving energy, compared to the conventional central circulating pump (CCCP) DH system. A hydraulic model was developed to simulate the hydraulic performance of such a DVSP DH system, based on Kirchhoff's laws. It was applied to a real DH network in Kuerle, China. In order to improve the model accuracy, a new parameter called resistance ratio was proposed by comparing the measured data and the simulated result. The validation result shows that the model has the ability to predict the hydraulic behavior of the DVSP system. The results show that when the rotational speeds of all substation pumps are synchronously decreased by the same percentage, the pump heads and the flow rates are also reduced synchronously and almost in the same degree in all loops. In addition, two operation cases of DH were investigated, including (I) the flow rate varies in all of the loops simultaneously, and (II) the flow rate varies only in one of the loops. For both cases, the DVSP system has a better performance of saving energy at least 30% than the CCCP system. Compared to the CCCP system, the installed pump capacities can be smaller in the DVSP system. Hence, applying DSVP, especially at a low flow rate, can save quite much electricity. Based on the example network in Kuerle, the DVSP system consumes electricity 71% and 31% less than the CCCP system for Cases I and II respectively.
|
|
| 2. |
- Song, C., et al.
(författare)
-
Alternative pathways for efficient CO2 capture by hybrid processes—A review
- 2018
-
Ingår i: Renewable & sustainable energy reviews. - : Elsevier Ltd. - 1364-0321 .- 1879-0690. ; 82, s. 215-231
-
Tidskriftsartikel (refereegranskat)abstract
- CO2 capture and storage technologies have been recognized as the primary option to mitigate the issue of climate change caused by the utilization of fossil fuels. In the last decades, several CO2 capture approaches have been developed, such as absorption, adsorption, membrane, cryogenic, hydrate and chemical looping combustion etc. However, the energy penalty is a general challenge for each technology. To overcome the disadvantages of standalone technology, the combination of two or more approaches (namely hybrid CO2 capture processes) has been considered as a potential option. In this work, the status and development of hybrid CO2 capture processes is presented in a classification of primary technology as absorption-based, adsorption-based, membrane-based and cryogenic-based. The detail configuration of each hybrid process is introduced. Simultaneously, the characteristics, advantages and potential challenges of each hybrid process are also summarized. Compared to the standalone methods, hybrid processes showed the superiority not only in CO2 recovery and energy penalty, but also in the installation investment. Therefore, hybrid processes can be a promising alternative to conventional CO2 capture technologies in future.
|
|
| 3. |
- Wang, R., et al.
(författare)
-
Multi-resource dynamic coordinated planning of flexible distribution network
- 2024
-
Ingår i: Nature Communications. - : Nature Portfolio. - 2041-1723. ; 15:1
-
Tidskriftsartikel (refereegranskat)abstract
- The flexible distribution network presents a promising architecture to accommodate highly integrated distributed generators and increasing loads in an efficient and cost-effective way. The distribution network is characterised by flexible interconnections and expansions based on soft open points, which enables it to dispatch power flow over the entire system with enhanced controllability and compatibility. Herein, we propose a multi-resource dynamic coordinated planning method of flexible distribution network that allows allocation strategies to be determined over a long-term planning period. Additionally, we establish a probabilistic framework to address source-load uncertainties, which mitigates the security risks of voltage violations and line overloads. A practical distribution network is adopted for flexible upgrading based on soft open points, and its cost benefits are evaluated and compared with that of traditional planning approaches. By adjusting the acceptable violation probability in chance constraints, a trade-off between investment efficiency and operational security can be realised.
|
|
| 4. |
- Zhao, J., et al.
(författare)
-
Reliability evaluation of community integrated energy systems based on fault incidence matrix
- 2022
-
Ingår i: Sustainable cities and society. - : Elsevier Ltd. - 2210-6707. ; 80
-
Tidskriftsartikel (refereegranskat)abstract
- Reliability evaluation is essential for the planning, operation, and analysis of community integrated energy systems (CIESs). However, it is still challenging to quantify the reliability of CIESs accurately and efficiently because of the diverse energy characteristics and energy conversion relationships. In this paper, a reliability evaluation method for CIESs based on fault incidence matrix (FIM) is proposed to analytically demonstrate the impact of equipment failures on system energy supply. The energy-bus-based unified reliability evaluation model of CIESs is presented to describe the energy flows of the system in a unified matrix form. Three types of FIMs are constructed to reveal the different consequences of device failures on energy supply. The reliability indices of a CIES can be directly calculated through simple algebraic and Boolean operations based on the FIMs, improving the calculation efficiency significantly. The FIMs make it easy to identify the vulnerability segments of the system, which is desirable in the practice of device maintenance or upgrade to improve the reliability of the CIES. Case studies are conducted on a typical CIES to verify the effectiveness and feasibility of the proposed method.
|
|
| 5. |
- Zhao, R., et al.
(författare)
-
Thermodynamic research of adsorbent materials on energy efficiency of vacuum-pressure swing adsorption cycle for CO2 capture
- 2018
-
Ingår i: Applied Thermal Engineering. - : Elsevier Ltd. - 1359-4311 .- 1873-5606. ; 128, s. 818-829
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a comprehensive thermodynamic research on energy efficiency of vacuum-pressure swing adsorption (VPSA). The study examined the influence from four types of typical adsorbent materials on the energy efficiency of VPSA by cycle parameters. The selected adsorbent materials are activated carbons, zeolite 5A, zeolite 13X, silica gels, and metal-organic frameworks (MOFs). The study also analyzes the effects of separation temperature, adsorption pressure, desorption pressure, CO2 concentration and percent of unused bed on the energy-efficiency of VPSA cycle. The examined performance parameters are CO2 working capacity, proportionality factor, energy consumption and second-law efficiency. The results show that the energy consumption is approximately 2.0–4.5 MJ/kg and the second-law efficiencies are 4–7% for VPSA cycles using the five adsorbent materials. The effect of adsorbent materials on the energy efficiency mainly depends on the proportionality factor of CO2 working capacity (β) of VPSA cycle, which is important to screen materials at the fixed cyclic boundary conditions and preliminary calculation of second-law efficiency for VPSA cycles. For existing adsorbent materials which are Type I commonly, the lower values of β would lead to the higher second-law efficiencies. The development of new adsorbents of Type III would be extremely urgent in near future.
|
|
| 6. |
- Gao, Y., et al.
(författare)
-
Cooling pitch cabinets in wind turbines using a pulsating heat pipe : A case study
- 2023
-
Ingår i: Case Studies in Thermal Engineering. - : Elsevier Ltd. - 2214-157X. ; 50
-
Tidskriftsartikel (refereegranskat)abstract
- As the electric capacity of wind turbine increases, heat dissipation in pitch cabinets becomes challenging owing to the limited space and rotating conditions. To cool down the pitch cabinet more effectively and allow heat dissipation, we designed and implemented a pulsating heat pipe (PHP) in this study. We designed PHP parameters and conducted performance tests to compare the cooling performance of the fabricated PHP with that of an air-based cooling system in a 1.5 MW wind turbine. The results demonstrated steady PHP operation under rotating conditions (17.3 rpm). At a heat load of 1000 W, the evaporator outlet temperature was only 76.1 °C. However, increasing the ambient temperature adversely affected PHP operation, resulting in higher temperature and thermal resistance. The heat-pipe-based cooling system lowered the insulated gate bipolar transistor (IGBT) temperature by about 20.4 °C in relation to the air-based cooling system, while being suitable under varied conditions. Additionally, the system could successfully operate when the heat load of IGBT was 2350 W, corresponding to a 7 MW electric capacity of the wind turbine. Reducing the manufacturing cost of the heat pipe would further enhance the applicability of this system for pitch cabinet IGBT cooling, such as decreasing payback period.
|
|
| 7. |
|
|
| 8. |
- Nagaraja, Ch., et al.
(författare)
-
Opening remarks
- 2016
-
Konferensbidrag (refereegranskat)
|
|
| 9. |
- Petropoulos, Fotios, et al.
(författare)
-
Operational Research : methods and applications
- 2024
-
Ingår i: Journal of the Operational Research Society. - : Taylor & Francis Group. - 0160-5682 .- 1476-9360. ; 75:3, s. 423-617
-
Forskningsöversikt (refereegranskat)abstract
- Throughout its history, Operational Research has evolved to include methods, models and algorithms that have been applied to a wide range of contexts. This encyclopedic article consists of two main sections: methods and applications. The first summarises the up-to-date knowledge and provides an overview of the state-of-the-art methods and key developments in the various subdomains of the field. The second offers a wide-ranging list of areas where Operational Research has been applied. The article is meant to be read in a nonlinear fashion and used as a point of reference by a diverse pool of readers: academics, researchers, students, and practitioners. The entries within the methods and applications sections are presented in alphabetical order. The authors dedicate this paper to the 2023 Turkey/Syria earthquake victims. We sincerely hope that advances in OR will play a role towards minimising the pain and suffering caused by this and future catastrophes.
|
|
