Guest Editorial: Advanced trends of control topologies for the integrated pv systems: Development, challenges and opportunities

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Guest Editorial: Situational awareness of integrated energy systems

Dear readers,2016 has a special anniversary coming up for physica status solidi (pss): Its most‐ever‐cited article “Optical Properties and Electronic Structure of Amorphous Germanium” by J. Tauc, R. Grigorovici, and A. Vancu (then Prague and Bucharest) was published half a century ago [1]. Printed about two months after receipt of the manuscript on June 1st 1966, it is a witness of the impressively fast publication times of pss back then. The article went online 40 years later in 2006, when Wiley had the pre‐internet‐era content scanned.Citations (right axis) and cumulative citations (left axis) to “Optical Properties and Electronic Structure of Amorphous Germanium” by J. Tauc et al., pss (1966) [1] versus year (Data from Web of Sci‐ence SCI, Dec 2015).magnified imageCitations (right axis) and cumulative citations (left axis) to “Optical Properties and Electronic Structure of Amorphous Germanium” by J. Tauc et al., pss (1966) [1] versus year (Data from Web of Sci‐ence SCI, Dec 2015).Beyond the reach of contemporary journal‐usage metrics, it has been collecting citations throughout 50 years, and recently we even saw a pronounced acceleration due to renewed interest in amorphous materials, with groups analyzing and developing the method proposed by Tauc et al. further [2]. pss proudly continues to provide, promote, and safeguard this valuable piece of information, and to accompany it through the changing times of its lasting legacy for the solid state physics research community.All the while, we are working with our authors, reviewers, board members, and guest editors to add content to the journal that has the potential for a similarly impressive career in scientific literature. Much of pss ' most interesting content is attracted by specially compiled, topical publications in collaboration with guest editors these days, and we can mention only a few of them here. Prominently in 2015, pss leaned in on the recent physics Nobel Prize topic again with a double issue on Nitride Semiconductors [3], and also the January issue of pss (b) in 2016 is dedicated to the specific challenges of Polarization‐Field Control in Nitride Light Emit‐ters [4]. Regarding long‐lasting topics we should mention the “20 Years of Science for Diamond” issue in pss (a) [5], and on the contemporary device physics line both “Transparent Conductive Oxides – Fundamentals and Applications” [6] and the issue dedicated to “Advanced Materials and Nano‐ technology for Photovoltaics” [7]. Reflecting the intense activity in the field and its impact on the world energy economy, photovoltaics based on inorganic as well as organic electronics have been increasingly prominent throughout the pss journal family, also resulting in the pss (RRL) standing topical section “RRL solar”. pss (b) has a very interesting collection on the physics of low‐dimensional structures, including graphene, nanotubes, and transition‐metal dichalcogenides, in “Electronic Properties of Novel Materials: Molecular Nanostructures” [8]. Venturing into more inter‐ disciplinary areas, pss (b) also published “Auxetics and Other Systems of ‘Negative’ Characteristics” with 32 contributions from physics, mathematics, and engineering perspectives [9] and pss (a) had “Engineering of Functional Interfaces” [10].This year we are looking forward to “Carbononics – Integrating Electronics, Photonics and Spintronics with Graphene Quantum Dots” [11], a Focus Issue in pss (RRL), and many other interesting projects.In 2015, physica status solidi (c) – current topics in solid state physics joined the other pss family journals on the editorial platform Editorial Manager. With system data on a new level of transparency, we may report for the year that pss published 1172 articles, worked with 71 guest editors and received approximately 4400 reviewer reports (including re‐reviews). As is obvious from these numbers, the journal family flourishes due to its lively interaction and the lasting strong support from the solid state researcher community. We would like to convey our sincere gratitude to all board members, guest editors, reviewers, and authors for the time and work they invest. And of course, we remain open for your future suggestions, and we will observe closely which topic may be poised to become the next pss evergreen.With best wishes for a prosperous year 2016,Sabine Bahrs, Nadezda Panarina, and Stefan HildebrandtEditorsphysica status solidi

Presents the guest editorial for this issue of the publication.

Guest Editorial – The Middle Palaeolithic in the Desert II

The papers in this special issue have been selected from the systems and balance-of- systems sessions at the 1998 Photovoltaic Performance and Reliability Workshop. The workshop was held November 3-5, 1998 and hosted by the Florida Solar Energy Center, Cocoa Beach, Florida under sponsorship of the US National Center for Photovoltaics (National Renewable Energy Laboratory and Sandia National Laboratories). The topics and issues addressed by these papers were identified in an invited review paper on PV systems by the guest editors. Their work was published earlier this year in Volume 7, Number 1 of Progress in Photovoltaics ('Photovoltaic Systems: An End-of-Millennium Review'). Experts in the PV community were asked to make presentations on these topics at the workshop. The papers that follow are the results of that effort. The papers are organized by topic: (1) codes and standards; (2) reliability; (3) design issues; and (4) commercialization.

Recent advancements in renewable energy technologies including dramatic improvement in cost-effectiveness and reliability have driven wide deployment of renewable energy sources in the modern electric grid across the globe. Among the renewable energy sources, solar photovoltaic (PV) is the most widely used. For the solar PV system, the dc input of a PV cell, module, string, or array, ranging from sub-1 V to 1500 V, in general, needs to be converted to an intermediate dc voltage by a dc–dc converter(s), for conditioning reliable dc power for grid interface. Thus, the dc–dc conversion greatly affects the entire PV system performance, such as efficiency and reliability among other crucial aspects. To address the critical aspects, many research and development efforts have conducted studies on the dc–dc converters for PV system such as converters with high conversion ratios and high power density and multiport converters to incorporate multiple sources including storage.

The integration of distributed energy resources (DERs), such as solar photovoltaic systems, as well as other synergistic assets, including electric vehicles, energy storage, and smart appliances, in electric power systems has been dramatically increasing in the past few years. These assets have the capability to provide much-needed flexibility to electric power systems for improved grid reliability, resilience, and economic efficiency; however, most of these resources are located behind the meter (BTM) on customer premises, and their flexibility is not fully used in current grid operations. Grid-edge computing plays an important role in unlocking the great benefits and potential that BTM resources could provide to electric power systems by enhancing visibility and controllability at the grid edge.

Soft computing applications in the field of industrial and environmental enterprises

The field of photovoltaics has undergone dramatic growth over the past few years. This growth has been accompanied by two significant changes in the commercial photovoltaic (PV) market. 1.The major PV market has shifted from the residential and commercial building markets to central station utility power markets. With this switch has come a new focus on the long-term reliability and durability of PV modules and systems. If you are installing tens or even hundreds of megawatts of PV modules, it is absolutely necessary to ensure that they will continue to perform adequately throughout their expected lifetime of at least 25 years. 2.Selling prices for PV modules have decreased from more than $4 per watt to less than $1 per watt in the last 5 years. This reduction in selling process has been driven by low-cost production in the developing world. This means that most of today's PV modules are being manufactured by companies that did not exist 10 or, in many cases, even 5 years ago. Yet the modules must carry 25-year warranties and are expected to survive at least that long without having the benefit of long-term field experience.

This special issue of JSEE is part of the efforts by the ASME Task Force on Integrated/Sustainable Building Equipment and Systems (ISBES) to identify and evaluate challenges and opportunities for integrating sustainable equipment and systems in individual buildings and within the built environment.Specifically, the ISBES Task Force is primarily interested in fostering new technologies and strategies to enhance building energy efficiency and reduce building energy use.This new approach is proceeding on three different but very important tracks:

Guest editorial: Application of cloud energy storage systems in power systems

The last two years have seen a tremendous increase in the number of installed solar energy systems. In 2010, annual grid-connected photovoltaic (PV) installations in the United States and worldwide were expected to be about 0.8 GW and 16–18 GW, respectively. At the end of 2010, the cumulative installed base of grid-connected PVs in the United States and worldwide was about 2 GW and about 40 GW, respectively. One of the areas that has been receiving much attention recently is large utility-scale solar systems.

Guest editorial: Modelling, methodologies and control techniques of DC/AC power conversion topologies for small‐ and large‐scale photovoltaic power systems