Comprehensive Evaluation of Biomass Energy Technologies in China
Pages 85-93
Qing Yang, Fei Han, Xudong Wu, Deyuan Wang, Xianhua Wang, Haiping Yang, Shihong Zhang and Hanping Chen

DOI: http://dx.doi.org/10.6000/1929-6002.2014.03.03.1

Published: 29 August 2014

Abstract: Based on a comprehensive review of the different biomass energy technologies in China, a hybrid evaluation model founding on Analytic Hierarchy Process(AHP) is proposed to offer a comprehensive evaluation of a variety of biomass energy technologies in China. In this model, three evaluation criteria, including the applicability of technology, economic viability and environment-friendly, are defined and nine indicators, including resources supply, equipment and technology, energy efficiency, energy grade,production cost, economic benefit, ecological impact, environmental pollution and social benefit,are devised. Priorities are established in this study based on pairwise comparisons of the elements. In addition, the model has been validated byvarious utilization technologies reported in literatures. Results show that environmental pollution, social benefit, ecological impact and resources supply greatly impact on the application of biomass technologies, followed by economic benefit. Besides, it is demonstrated that integrated technologies of biomass energy, which is closely related with residential daily life and compatible with local ecological environment, possess evident superiority. Furthermore, the outcome can be supportive for guidingfuture development of biomass energy in China.

Performance of Clay Wood Cook Stove: An Analysis of Cost and Fuel Savings
Pages 94-98

A. Kuhe, H. A. Iortyer and A. Iortsor

DOI: http://dx.doi.org/10.6000/1929-6002.2014.03.03.2

Published: 29 August 2014

Abstract: The assessment of cooking energy cost and efficiency of improved woodfuel clay cookstoves in Nigeria have been considered in this study. Two improved wood burning clay cookstove models were compared to the 3-stone fire stove using the water boiling test and controlled cookingtest. The following parameters: specific fuel consumption (SFC), thermal efficiency, ebulution time and cooking energy cost were considere as key indicators for comparison. The results show that the fire power for the cold starts phases were 7.72KW, 8.59KW and 9.78KW for the stove with grate, modified stove without grate and the 3-stone open fire (TFS) respectively. The thermal efficiencies ranges between 19-35%, 13.8-26.8% and 11.7-22.8% for the cold start, hot start and simmer phases for mud stove with grate (MSWG), mud stove no grate (MSNG) and three stone open fire (TFS) respectively. MSWG, showed the highest savings potential on wood fuel consumption with the lowest total wood cost of N127.80 and sfc of 1.632Kg of fuel/kg of food cooked. While MSNG and TFS, have a total wood fuel cost and SFCof N207.70 , N269.20, and 2.141, 1.632kg of fuel/kg of food cooked respectively.

Generation Scheduling in Power Systems with Hydro Electric Plants
Pages 99-106
S. Palamarchuk

DOI: http://dx.doi.org/10.6000/1929-6002.2014.03.03.3

Published: 29 August 2014

Abstract: Medium-term generation scheduling is an important component of power systems operation and management. The traditional problem statement aimed at reducing the total production cost can hardly correspond to the market environment. The paper considers specific features of the problem statement for a wholesale electricity market environment. An approach is suggested to solve the problem on the basis of bi-level optimization models. Such models take into account possible distortion of economic and technical parameters of generating units. The proposed technique obtains equilibrium of the generation company’s interests to simulate the competitive behavior under the oligopoly electricity market. A mathematical statement of the problem supposes the application of a dynamic programming method. An algorithm for the stochastic dynamic programming application is developed. A numerical example is presented to demonstrate the applicability of the method and algorithm. The efficiency of the proposed approach is shown in comparison with the traditional generation scheduling technique.

Potential Performance Enhancement of a Solar Combisystem with an Intelligent Controller
Pages 107-119
Martin F. Pichler, Hermann Schranzhofer, Andreas Heinz and Richard Heimrath

DOI: http://dx.doi.org/10.6000/1929-6002.2014.03.03.4

Published: 29 August 2014

Abstract: Solar thermal systems in residential buildings are generally controlled by two-level controllers, which activate solar thermal or at times with low solar radiation auxiliary energy supply into a thermal storage. Simple controllers do not have any information on actual or expected solar radiation. This leads to interference of auxiliary- and solar heat supply, which reduces the share of solar thermal energy fed into the thermal storage. Increasing accuracy of weather forecast data suggests incorporation of this information in the control algorithm. This work analyzes the maximum potential performance enhancement when applying such an intelligent predictive control. Two solar thermal systems with one auxiliary source respectively are designed in TRNSYS – these systems represent the base case. Further, a number of simulations are conducted with minor variations for the plant parameters – this gives generic results for different system configurations. In addition, each system configuration is altered to mimic the behavior of a plant with intelligent predictive control. Comparison of results indicates an improvement potential up to 10% for annual solar fractions and up to 30% for monthly solar fractions. The performance bound with respect to the annual auxiliary energy savings is approximately 8%.

Enhancement of Biogas Production in Two-Phase Anaerobic Fermentation System for Lower-Temperature Applications
Pages 120-128

Hongqiong Zhang, Wenzhe Li, Yong Sun and Xiangyou Wang

DOI: http://dx.doi.org/10.6000/1929-6002.2014.03.03.5

Published: 29 August 2014

Abstract: For the purpose of enhancing the biogas production and operation stability of system at low temperature, atwo-phase anaerobic fermentation facility for rural household energy generation was proposed. Inthis facility, the quantity of the fermented materials could be balanced by controlling the hydraulic retention time, which based on pH of the acidification tank and the fermentation tank. In addition, a portion of the biogas generated could be used to heat the acidification tank and the fermentation tank. Results shows that the optimal daily production rate of biogas for 1m³ fermentation liquid was about 1.47 L/L d^-1at a mixing ratio of cow:swine:chicken manure was 3: 1: 0.5. The production rate obtained in this study was more than four times higher than that from traditional single-phase processes (0.35 L/L d^-1). About 5.43m³ biogas can be produced daily per household with an average CH₄ content of 76.8%. The two-phase process developed in this work will also reduce environmental pollution and increase energy production efficiencies.