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The new millennium has witnessed a pervasive shift of trend from AC to DC in the residential load sector. The shift is predominantly due to independent residential solar PV systems at rooftops and escalating electronic loads with better energy saving potential integrated with diminishing prices as well as commercial availability of DC-based appliances. Comprehensive sensitivity analysis considering the real load profile is missing in the present body of knowledge. In order to fill that gap, this paper is an attempt to include a comprehensive sensitivity analysis of the DC distribution system and its simulation-based comparison with its AC counterpart, considering the real load profile. The paper uses the Monte Carlo technique and probabilistic approach to add diversity in residential loads consumption to obtain an instantaneous load profile. Various possible scenarios such as variation of standard deviation from 5% to 20% of mean load value, PV capacity variation from 1000 W to 9000 W, and variation in power electronic converter (PEC) efficiencies are incorporated to make the system realistic as much as possible maintaining a fair comparison between both systems. The paper concludes with the baseline efficiency advantage of 2% to 3% during the day for the case of the DC distribution system as compared to the AC distribution system. [ABSTRACT FROM AUTHOR]

The energy crisis has pushed Pakistan way down the economic rankings. More than 70% the total population resides in rural regions. The energy crisis has crippled the lifestyle of the rural class (RC) in many aspects. For rural Pakistan, the energy scarcity, a hurdle in sustainable development, can be eliminated by biogas. Almost every rural family is associated with agriculture and owns livestock animals, therefore self-sufficient in biogas plant's fuel. Fuel abundance and favourable climatic conditions make energy extraction from biomass facile and fruitful; still there are many reasons that RC is dumped in the energy crisis. In this paper, a survey is conducted in villages of Pakistan to discover the reasons due to which domestic biogas plants have not yet gained their due importance. Institutional, financial, awry planning and social barriers are highlighted at the grass root level in the development of biogas technology in rural Pakistan. In contrast, villages where biogas plants are present, the survey analysis revealed prosperity rendered through savings, reduction in diseases and workload. The paper concludes with an emphasis on the requirement of concrete and comprehensive policy that is capable to deal with the barriers in the route of biogas technology. [ABSTRACT FROM AUTHOR]

The birth of electricity witnessed "the battle of currents" between AC and DC as a medium of power transfer. AC won the battle in the first place because of its ability to transform voltage levels. However, with the development of power electronic converters (PECs), DC is striking back. Most of the electronic loads in our conventional AC-based homes are DC by nature. Moreover, the modern concept of energy-efficient variable speed drive (VSD) based loads, i.e. DC-inverter based air-conditioners and refrigerators, require a DC link for their operation. The driving component of all such loads is the PEC. The operational efficiency of PECs depends on the loading which varies throughout the day. This paper presents a mathematical model based on a bottom-up approach to the comparative efficiency analysis of AC and DC distribution systems considering daily load variation. Two topologies are presented where AC and DC distribution systems are compared in terms of efficiency. The first topology (T1) defines a separate/independent converter for each load, whereas in the second topology (T2) loads of a particular class are lumped and driven by a single converter. The results present DC distribution better than AC distribution with an efficiency advantage of 2.28% and 1.57% for T1 and T2, respectively. [ABSTRACT FROM AUTHOR]

Stability of a system is one of its most crucial yet largely hidden characteristic. Power systems, both ac and dc, face instability; with dc systems facing voltage instability only while ac systems have to confront frequency and rotor angle instability in addition to the voltage irritability. Apparently, this makes dc systems easier to design since there is only one form of instability i.e. voltage instability which needs to be tackled. Yet this has proved a huge challenge and even now, a decade and a half after the beginning of active research for stabilizing a dc distributed power system, research efforts are still in progress. This paper attempts to present and compare some of the latest research techniques for dc distributed power system stability as well as briefly reviews the history of research efforts in this area. A short description of the dc distributed system paradigm along with its applications is also included in this paper. [ABSTRACT FROM AUTHOR]