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.