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Abstract: This paper describes the development of a simple hybrid desalination system of a Multi-Effect Distillation (MED) and an adsorption (AD) cycle operating at sub-atmospheric pressures and temperatures. By hybridizing the conventional MED with an AD cycle, there is a symbiotic enhancement of performances of both cycles. The performance enhancement is attributed to (i) the cascade of adsorbent’s regeneration temperature and this extended the usage of thermal energy emanating from the brine heater and (ii) the vapor extraction from the last MED stage by AD cycle which provides the effect of lowering saturation temperatures of all MED stages to the extent of 5°C, resulting in scavenging of heat leaks into the MED stages from the ambient. The combined effects of the hybrid cycles increase the water production capacity of the desalination plant by nearly twofolds. In this paper, we demonstrate a hybrid cycle by simulating an 8-stage MED cycle which is coupled to an adsorption cycle for direct vapor extraction from the last MED stage. The sorption properties of silica gel is utilized (acting as a mechanical vapor compressor) to reduce the saturation temperatures of MED stages. The modeling utilizes the adsorption isotherms and kinetics of the adsorbent+adsorbate (silica-gel+water) pair along with the governing equations of mass, energy and concentration. For a 8-stage MED and AD cycles operating at assorted temperatures of 65–90°C, the results show that the water production rate increases from 60% to twofolds when compared to the MED alone. The performance ratio (PR) and gain output ratio (GOR) also improve significantly. [Copyright &y& Elsevier]

This paper develops and assesses the performance of a short-term demand response (DR) model for utility load control with applications to resource planning and control design. Long term response models tend to underestimate short-term demand response when induced by prices. This has two important consequences. First, planning studies tend to undervalue DR and often overlook its benefits in utility demand management program development. Second, when DR is not overlooked, the open-loop DR control gain estimate may be too low. This can result in overuse of load resources, control instability and excessive price volatility. Our objective is therefore to develop a more accurate and better performing short-term demand response model. We construct the model from first principles about the nature of thermostatic load control and show that the resulting formulation corresponds exactly to the Random Utility Model employed in economics to study consumer choice. The model is tested against empirical data collected from field demonstration projects and is shown to perform better than alternative models commonly used to forecast demand in normal operating conditions. The results suggest that (1) existing utility tariffs appear to be inadequate to incentivize demand response, particularly in the presence of high renewables, and (2) existing load control systems run the risk of becoming unstable if utilities close the loop on real-time prices. [ABSTRACT FROM AUTHOR]

Highlights: [•] This paper presents a novel methodology for modeling building energy performance. [•] The novelty lies in the use of lead-lag dynamics to present building energy system. [•] The developed model is simple and accurate with minimal physical parameters. [•] Comparison with benchmarks and measurements shows good results. [Copyright &y& Elsevier]

Abstract: Development and deployment of low-carbon energy technologies has been a national strategy of both the UK and China for a number of years, including the use of renewable generation technologies and the improvement of energy efficiency of operations and activities. The paper addresses several issues of generic importance to a residential microgrid system such as network modelling, advanced control and integration of intelligent monitoring techniques. The system, comprising representative distributed generation technologies of photovoltaics, wind turbines and combined heat and power, has been simulated by PSCAD/EMTDC under different operational scenarios. Studies include the effect of environmental condition changes, control systems and power electronics on wind turbines and PV cells, and the mixture of wind/solar/CHP energy generation under dominance of each technology. The performance and dynamics of the system are examined against symmetrical and asymmetrical electrical faults to seek an optimal isolation and restoration of the distributed generation unit from the connected grid system. Modelling these system interactions has demonstrated the feasibility of the proposed residential microgrid system. [Copyright &y& Elsevier]

Abstract: As a representative of many emerging economies, BRICS’ economies have been greatly developed in recent years. Meanwhile, the proportion of energy consumption of BRICS to the whole world consumption has increased. Therefore, it is significant to analyze and compare the energy efficiency among them. This paper firstly utilizes a Super-SBM model to measure and calculate the energy efficiency of BRICS, then analyzes their present status and development trend. Further, Bootstrap is applied to modify the values based on DEA derived from small sample data, and finally the relationship between energy efficiency and carbon emissions is measured. Results show that energy efficiency of BRICS as a whole is low but has a quickly increasing trend. Also, the relationship between energy efficiency and carbon emissions vary from country to country because of their different energy structures. The governments of BRICS should make some relevant energy policies according to their own conditions. [Copyright &y& Elsevier]

Abstract: Occupants of dwellings with grid-connected photovoltaic (PV) systems can often benefit financially from exporting electricity to the grid. When export prices are lower than import prices, however, occupants are incentivised to time-shift demand in order to avoid exports and reduce imports. To maximise this potential financial benefit, the addition of batteries to the PV system has been proposed to take advantage of the specific commercial opportunity presented to the occupant of trading exported power during the day for imported power during the evening. This paper therefore assesses the economic and environmental impact of the use of lead-acid batteries in grid-connected PV systems under current feed-in tariff arrangements in the UK. The development of a lead-acid battery model is described, which is used to simulate hypothetical power flows using measured data on domestic PV systems in the UK. The simulation results indicate that the net benefit of the battery is negative, even when considering an idealised lossless battery. When realistic energy losses and lifetimes are accounted for, the financial loss for the systems considered here can approach £1000/year. The environmental impact of the use and production of the lead-acid battery is also described, and also found to be negative, further strengthening the argument against the use of lead-acid batteries in domestic grid-connected PV systems. [Copyright &y& Elsevier]

Abstract: This paper proposes two general procedures to develop wind speed models based on stochastic differential equations. Models are intended to generate wind speed trajectories with statistical properties similar to those observed in the wind speed historical data available for a particular location. The developed models are parsimonious in the sense that they only use the information about the marginal distribution and the autocorrelation observed in the wind speed data. Since these models are continuous, they can be used to simulate wind speed trajectories at different time scales. However, their ability to reproduce the statistical properties of the wind speed is limited to a time frame of hours since diurnal and seasonal effects are not considered. The developed models can be embedded into dynamic wind turbine models to perform dynamic studies. Statistical properties of wind speed data from two real-world locations with significantly different characteristics are used to test the developed models. [Copyright &y& Elsevier]

Abstract: Similar to many other countries, all nations in the Greater Mekong Subregion (GMS) have planned or are planning to develop strong national biofuel programs. The overall goal of this paper is to better understand the impacts of global and regional biofuels on agriculture and the rest of the economy, with a specific focus on the GMS. Based on a modified multi-country, multi-sector computable general equilibrium model, this study reveals that global biofuel development will significantly increase agricultural prices and production and change trade in agricultural commodities in the GMS and the rest of world. While biofuel in the GMS will have little impacts on global prices, it will have significant effects on domestic agricultural production, land use, trade, and food security. The results also show that the extent of impacts from biofuel is highly dependent on international oil prices and the degree of substitution between biofuel and gasoline. The findings of this study have important policy implications for the GMS countries and the rest of world. [Copyright &y& Elsevier]