Martinez-Lera S.,LITEC CSIC Spanish Council for Scientific Research |
Ballester J.,University of Zaragoza
Energy | Year: 2010
The design of capacity and operation of CHCP (combined heat, cooling and power) plants applied to HVAC (heating, ventilation and air conditioning) in buildings entails a considerable difficulty, because efficiency and economic aspects frequently interact in a complex way. Due to the strong fluctuations in thermal demands, the evaluation of a given design usually requires detailed simulations and a significant amount of input data. This paper proposes simplified approaches to estimate the main parameters characterising the thermal performance of the plant (ATD e method) as well as to identify optimal designs for a given application under certain encouragement policies (annual PES (primary energy savings) strategy). In the ATD e method, the duration curve of ATD (aggregated thermal demand) is used to estimate, among others, the amount of heat and cooling effectively supplied to the final user for a given design of the plant. This procedure serves to achieve a quick, global evaluation of the thermal performance of CHP (combined heat and power) or CHCP plants with little computational effort. The annual PES strategy searches the optimal values for the engine capacity, the OP (operation period) or both for CHP and CHCP plants in a particular application, defined by its energy demands. Both methods have demonstrated a notably good performance in several test cases with different patterns of the thermal demands. © 2010 Elsevier Ltd.
Martinez-Lera S.,University of Zaragoza |
Ballester J.,University of Zaragoza |
Martinez-Lera J.,LITEC CSIC Spanish Council for Scientific Research
Applied Energy | Year: 2013
Thermal energy storage (TES) can lead to significant energy savings and economic benefits in combined heating, cooling and power plants (CHCPs) for buildings in the tertiary sector. However, their complex interactions with the rest of the CHCP system make their adequate sizing difficult without using extensive and detailed simulations. The authors have developed a new method to evaluate the thermal contribution of TES based on simple procedures. Comparisons with detailed simulations for a range of situations confirm the ability of this method to predict the effect of TES on CHCP systems with good approximation, as well as to find the optimal size in a relatively simple manner and with few required data. The case studies show a strong dependence of the TES contribution on the demands profile and the operation strategy. However, adequately sized TES are proven to bring relevant energy savings as well as economic profit to CHCP plants. In this paper, sizing procedures are provided to find the optimal volume both in terms of thermodynamic efficiency and of economic profit. © 2013 Elsevier Ltd.
Gonzalo-Tirado C.,LITEC CSIC Spanish Council for Scientific Research |
Jimenez S.,LITEC CSIC Spanish Council for Scientific Research |
Ballester J.,University of Zaragoza
Combustion and Flame | Year: 2012
Char gasification by CO2 may play an important role in oxy-fuel applications and affect particle temperature histories and overall reaction rates during combustion. This paper presents the results of a complete set of experiments of char gasification in CO2 performed with a pulverized Indonesian sub-bituminous coal in an entrained flow reactor under realistic conditions; series of burnout curves at different reactor temperatures (1040-1300°C) and CO2 concentrations (0.7-100%) reveal consistent trends in the gasification rates. The study included also devolatilization and oxidation tests with this coal in the same experimental facility. The data are used to derive apparent kinetics for the three processes, in a manner similar to that followed in a previous work for the oxidation of a pulverized coal. The gasification kinetic parameters and reaction rates measured are then compared with values taken or derived from previous works by others, obtained by thermogravimetric analysis or experiments in entrained flow reactors. Finally, the relevance of char gasification in the overall reaction rate under conditions representative of those in an industrial boiler is explored, in particular for the case of oxy-coal combustion. © 2011 The Combustion Institute.