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Heat prices for public buildings in Tianjin
Boyuan HAO,Zhe TIAN,Yan DING,Peng PENG
Frontiers in Energy. 2016, 10 (3): 249-259.
https://doi.org/10.1007/s11708-016-0412-z
Energy-saving awareness of heat users and heating enterprises can be stimulated by implementing heat metering for public buildings and by establishing scientific and reasonable policies for heat prices in China. In this paper, a two-part heat price for public buildings in Tianjin is introduced, which divides the heat price into a basic part and a metering part. According to the statistical analysis of information collected from two pilot heating enterprises, the specific heat load for public buildings in Tianjin is calculated, and three candidate schemes of heat price are proposed. A simulation of heat cost is also conducted, and the benefits for both heat users and heating enterprises are balanced. Finally, the two-part heat price for public buildings in Tianjin is determined: the basic heat price is recommended to be 20 CNY/m2, and the metering heat price is recommended to be 76.10 CNY/GJ. Such a price could be implemented in the initial stage of heat metering for public buildings in Tianjin.
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Energy shift: decline of easy oil and restructuring of geo-politics
Oliver R. INDERWILDI, David A. KING
Frontiers in Energy. 2016, 10 (3): 260-267.
https://doi.org/10.1007/s11708-016-0416-8
This paper critically assesses the geopolitical and geo-economic impact of novel fuel resources on both resource exporters and importers. Presently, very strong political and economic forces drive the utilisation of domestic, unconventional oil and gas recovery in the West as these enhance energy security and ease balance of payment issues. The additional capacity generated by this trend has, supported by other effects such as Saudi Arabia’s decision to maintain current production, triggered a significant reduction of oil prices. Consequently, it is now oil exporters that struggle with the balance of payment issues and often these countries base their fiscal budget completely on fossil fuel revenues. In fact, these unconventional resources help turn the tide while oil exporters are now politically significantly weakened due to the increased energy sufficiency of the West. The catch is that the extraction of unconventional types of oil has many environmental implications. So, internalising the environmental externalities have to be considered. This paper, therefore, assesses, next to geopolitics and geo-economics, the environmental implications of this trend.
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Prediction of the theoretical and semi-empirical model of ambient temperature
Foued CHABANE,Noureddine MOUMMI,Abdelhafid BRIMA,Abdelhafid MOUMMI
Frontiers in Energy. 2016, 10 (3): 268-276.
https://doi.org/10.1007/s11708-016-0413-y
It is well known that the ambient temperature is a sensitive parameter which has a great effect on biology, technology, geology and even on human behavior. A prediction is a statement about an uncertain event. It is often, but not always, based upon experience or knowledge. Although guaranteed accurate information about the future is in many cases impossible, prediction can be useful to assist in making plans about possible developments. As a result, temperature profiles can be developed which accurately represent the expected ambient temperature exposure that this environment experiences during measurement. The ambient temperature over time is modeled based on the previous Tmin and Tmax data and using a Lagrange interpolation. To observe the comprehensive variation of ambient temperature the profile must be determined numerically. The model proposed in this paper can provide an acceptable way to measure the change in ambient temperature.
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A new method for estimating the longevity and degradation of photovoltaic systems considering weather states
Amir AHADI,Hosein HAYATI,Joydeep MITRA,Reza ABBASI-ASL,Kehinde AWODELE
Frontiers in Energy. 2016, 10 (3): 277-285.
https://doi.org/10.1007/s11708-016-0400-3
The power output of solar photovoltaic (PV) systems is affected by solar radiation and ambient temperature. The commonly used evaluation techniques usually overlook the four weather states which are clear, cloudy, foggy, and rainy. In this paper, an ovel analytical model of the four weather conditions based on the Markov chain is proposed. The Markov method is well suited to estimate the reliability and availability of systems based on a continuous stochastic process. The proposed method is generic enough to be applied to reliability evaluation of PV systems and even other applications. Further aspects investigated include the new degradation model for reliability predication of PV modules. The results indicate that the PV module degradation over years, failures, and solar radiation must be considered in choosing an efficient PV system with an optimal design to achieve the maximum benefit of the PV system. For each aspect, a method is proposed, and the complete focusing methodology is expounded and validated using simulated point targets. The results also demonstrate the feasibility and applicability of the proposed method for effective modeling of the chronological aspects and stochastic characteristics of solar cells as well as the optimal configuration and sizing of large PV plants in terms of cost and reliability.
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Generating capacity adequacy evaluation of large-scale, grid-connected photovoltaic systems
Amir AHADI,Seyed Mohsen MIRYOUSEFI AVAL,Hosein HAYATI
Frontiers in Energy. 2016, 10 (3): 308-318.
https://doi.org/10.1007/s11708-016-0415-9
Large-scale, grid-connected photovoltaic systems have become an essential part of modern electric power distribution systems. In this paper, a novel approach based on the Markov method has been proposed to investigate the effects of large-scale, grid-connected photovoltaic systems on the reliability of bulk power systems. The proposed method serves as an applicable tool to estimate performance (e.g., energy yield and capacity) as well as reliability indices. The Markov method framework has been incorporated with the multi-state models to develop energy states of the photovoltaic systems in order to quantify the effects of the photovoltaic systems on the power system adequacy. Such analysis assists planners to make adequate decisions based on the economical expectations as well as to ensure the recovery of the investment costs over time. The failure states of the components of photovoltaic systems have been considered to evaluate the sensitivity analysis and the adequacy indices including loss of load expectation, and expected energy not supplied. Moreover, the impacts of transitions between failures on the reliability calculations as well as on the long- term operation of the photovoltaic systems have been illustrated. Simulation results on the Roy Billinton test system has been shown to illustrate the procedure of the proposed frame work and evaluate the reliability benefits of using large-scale, grid-connected photovoltaic system on the bulk electric power systems. The proposed method can be easily extended to estimate the operating and maintenance costs for the financial planning of the photovoltaic system projects.
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Control of peak pressures of an HCCI engine under varying swirl and operating parameters
T. KARTHIKEYA SHARMA,G. AMBA PRASAD RAO,K. MADHU MURTHY
Frontiers in Energy. 2016, 10 (3): 337-346.
https://doi.org/10.1007/s11708-016-0401-2
The major advantages of homogeneous charge compression ignition (HCCI) are high efficiency in combination with low NOx-emissions. However, one of the major challenges with HCCI is the control of higher peak pressures which may damage the engine, limiting the HCCI engine life period. In this paper, an attempt is made to analyze computationally the effect of induction swirl in controlling the peak pressures of an HCCI engine under various operating parameters. A single cylinder 1.6 L reentrant piston bowl diesel engine is chosen. For computational analysis, the ECFM-3Z model of STAR –CD is considered because it is suitable for analyzing the combustion processes in SI and CI engines. As an HCCI engine is a hybrid version of SI and CI engines, the ECFM-3Z model with necessary modifications is used to analyze the peak pressures inside the combustion chamber. The ECFM-3Z model for HCCI mode of combustion is validated with the existing literature to make sure that the results obtained are accurate. Numerical experiments are performed to study the effect of varying properties like speed of the engine, piston bowl geometry, exhaust gas recirculation (EGR) and equivalence ratio under different swirl ratios in controlling the peak pressures inside the combustion chamber. The results show that the swirl ratio has a considerable impact on controlling the peak pressures of HCCI engine. A reduction in peak pressures are observed with a swirl ratio of 4 because of reduced in cylinder temperatures. The combined effect of four operating parameters, i.e., the speed of the engine, piston bowl geometry, EGR, and equivalence ratio with swirl ratios suggest that lower intake temperatures, reentrant piston bowl, higher engine speeds and higher swirl ratios are favorable in controlling the peak pressures.
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A state-of-the-art review of solar passive building system for heating or cooling purpose
Arun Kumar NANDA,C K PANIGRAHI
Frontiers in Energy. 2016, 10 (3): 347-354.
https://doi.org/10.1007/s11708-016-0403-0
The major portion of energy in a building is consumed by heating, ventilating, and air-conditioning (HVAC). The traditional heating and cooling systems contribute greatly to the emission of greenhouse gases, especially carbon dioxide. Four different ways, i.e., Trombe wall, solar chimney, unglazed transpired solar façade, and solar roof, are adopted for solar heating. Similarly, two major ways, i.e., evaporative cooling and building integrated evaporative cooling are adopted for cooling of the building. Therefore, an attempt has been made in this paper to compile the developments of solar heating and cooling technologies in a building.
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Optimal operation of microgrid using hybrid differential evolution and harmony search algorithm
S. SURENDER REDDY,Jae Young PARK,Chan Mook JUNG
Frontiers in Energy. 2016, 10 (3): 355-362.
https://doi.org/10.1007/s11708-016-0414-x
This paper proposes the generation scheduling approach for a microgrid comprised of conventional generators, wind energy generators, solar photovoltaic (PV) systems, battery storage, and electric vehicles. The electrical vehicles (EVs) play two different roles: as load demands during charging, and as storage units to supply energy to remaining load demands in the MG when they are plugged into the microgrid (MG). Wind and solar PV powers are intermittent in nature; hence by including the battery storage and EVs, the MG becomes more stable. Here, the total cost objective is minimized considering the cost of conventional generators, wind generators, solar PV systems and EVs. The proposed optimal scheduling problem is solved using the hybrid differential evolution and harmony search (hybrid DE-HS) algorithm including the wind energy generators and solar PV system along with the battery storage and EVs. Moreover, it requires the least investment.
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A review of cryogenic power generation cycles with liquefied natural gas cold energy utilization
Feier XUE,Yu CHEN,Yonglin JU
Frontiers in Energy. 2016, 10 (3): 363-374.
https://doi.org/10.1007/s11708-016-0397-7
Liquefied natural gas (LNG), an increasingly widely applied clean fuel, releases a large number of cold energy in its regasification process. In the present paper, the existing power generation cycles utilizing LNG cold energy are introduced and summarized. The direction of cycle improvement can be divided into the key factors affecting basic power generation cycles and the structural enhancement of cycles utilizing LNG cold energy. The former includes the effects of LNG-side parameters, working fluids, and inlet and outlet thermodynamic parameters of equipment, while the latter is based on Rankine cycle, Brayton cycle, Kalina cycle and their compound cycles. In the present paper, the diversities of cryogenic power generation cycles utilizing LNG cold energy are discussed and analyzed. It is pointed out that further researches should focus on the selection and component matching of organic mixed working fluids and the combination of process simulation and experimental investigation, etc.
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