A review on the complementarity of renewable energy sources: concept, metrics, application and future research directions

It is expected, and regionally observed, that energy demand will soon be covered by a widespread deployment of renewable energy sources. However, the weather and climate driven energy sources are characterized by a significant spatial and temporal variability. One of the commonly mentioned solutions to overcome the mismatch between demand and supply provided by renewable generation is a hybridization of two or more energy sources in a single power station (like wind-solar, solar-hydro or solar-wind-hydro). The operation of hybrid energy sources is based on the complementary nature of renewable sources. Considering the growing importance of such systems and increasing number of research activities in this area this paper presents a comprehensive review of studies which investigated, analyzed, quantified and utilized the effect of temporal, spatial and spatio-temporal complementarity between renewable energy sources. The review starts with a brief overview of available research papers, formulates detailed definition of major concepts, summarizes current research directions and ends with prospective future research activities. The review provides a chronological and spatial information with regard to the studies on the complementarity concept.Comment: 34 pages 7 figures 3 table

A Doctor Facing Turbulent Times: Antoni Tomasz Jurasz, Citizen of the World

The eponymous of the Jurasz procedure is Antoni Tomasz Jurasz (1882–1961). The procedure is a standard approach to treating mature pancreatic pseudocysts that are in contact with the stomach, although recent advances in instrumentation have empowered surgeons to perform pseudocystogastrostomy laparoscopically for this problem. Dr. Jurasz was born in Germany but felt himself as Polish as his ancestors. He graduated from Heidelberg with a degree in medicine. Over the following years, he developed a German surgery school, especially helping with the achievements of Erich Lexer and Erwin Payr. During the period between World Wars I and II, Jurasz chaired and led the Surgery Clinic of Poznan University in Poland; and he gave lectures and performed public operations abroad. These activities, together with articles published in German-, French-, and English-language medical journals, made him a world-renowned figure in the field of abdominal and thyroid surgery. During World War II, he revealed exceptional traits, taking part in the September Campaign in Poland as a surgeon. He then organized the Polish School of Medicine and the Paderewski Hospital in Edinburgh. Despite his outstanding mind, generosity, and merits, A. T. Jurasz became persona non grata in Communist Poland, which ultimately persuaded him to emigrate to the United States

Economic analysis and optimization of a renewable energy based power supply system with different energy storages for a remote island

This study investigates and compares the various combinations of renewable energies (solar, wind) and storage technologies (battery, pumped hydro storage, hybrid storage) for an off-grid power supply system. Four configurations (i.e., single RE source system, double RE source system, single storage, and double storage system) based on two scenarios (self-discharge equal to 0% and 1%) are considered, and their operational performance is compared and analyzed. The energy management strategy created for the hybrid pumped battery storage (HPBS) considers that batteries cover low energy surplus/shortages while pumped hydro storage (PHS) is the primary energy storage device for serving high-energy generations/deficits. The developed mathematical model is optimized using Particle Swarm Optimization and the performance and results of the optimizer are discussed in particular detail. The results evidence that self-discharge has a significant impact on the cost of energy (13%–50%) for all configurations due to the substantial increase in renewable energy (RE) generators size compared to the energy storage capacity. Even though solar-wind-PHS is the cost-optimal arrangement, it exhibits lower reliability when compared to solar-wind-HPBS. The study reveals the significance of HPBS in the off-grid RE environment, allowing more flexible energy management, enabling to guarantee a 100% power supply with minimum cost and reducing energy curtailment. Additionally, this study presents and discuss the results of a sensitivity analysis conducted by varying load demand and energy balance of all considered configurations is performed, which reveals the effectiveness of the supplementary functionality of both storages in hybrid mode. Overall, the role of energy storage in hybrid mode improved, and the total energy covered by hybrid storage increased (48%), which reduced the direct dependency on variable RE generation

Complementarity of wind and solar power in North Africa: Potential for alleviating energy droughts and impacts of the North Atlantic Oscillation

With growing gas and oil prices, electricity generation based on these fossil fuels is becoming increasingly expensive. Furthermore, the vision of natural gas as a transition fuel is subject to many constraints and uncertainties of economic, environmental, and geopolitical nature. Consequently, renewable energies such as solar and wind power are expected to reach new records of installed capacity over the upcoming years. Considering the above, North Africa is one of the regions with the largest renewable resource potential globally. While extensively studied in the literature, these resources remain underutilized. Thus, to contribute to their future successful deployment and integration with the power system, this study presents a spatial and temporal analysis of the nature of solar and wind resources over North Africa from the perspective of energy droughts. Both the frequency and maximal duration of energy droughts are addressed. Both aspects of renewables’ variable nature have been evaluated in the North Atlantic Oscillation (NAO) context. The analysis considers the period between 1960 and 2020 based on hourly reanalysis data (i.e., near-surface shortwave irradiation, wind speed, and air temperature) and the Hurrel NAO index. The findings show an in-phase relationship between solar power and winter NAO index, particularly over the coastal regions in western North Africa and opposite patterns in its eastern part. For wind energy, the connection with NAO has a more zonal pattern, with negative correlations in the north and positive correlations in the south. Solar energy droughts dominate northern Tunisia, Algeria, and Morocco, while wind energy droughts mainly occur in the Atlas Mountains range. On average, solar energy droughts tend not to exceed 2–3 consecutive days, with the longest extending for five days. Wind energy droughts can be as prolonged as 80 days (Atlas Mountains). Hybridizing solar and wind energy reduces the potential for energy droughts significantly. At the same time, the correlation between their occurrence and the NAO index remains low. These findings show the potential for substantial resilience to inter-annual climate variability, which could benefit the future stability of renewables-dominated power systems.Graphical abstrac

Source levels of social sounds in migrating humpback whales (Megaptera novaeangliae)

The source level of an animal sound is important in communication, since it affects the distance over which the sound is audible. Several measurements of source levels of whale sounds have been reported, but the accuracy of many is limited because the distance to the source and the acoustic transmission loss were estimated rather than measured. This paper presents measurements of source levels of social sounds (surface-generated and vocal sounds) of humpback whales from a sample of 998 sounds recorded from 49 migrating humpback whale groups. Sources were localized using a wide baseline five hydrophone array and transmission loss was measured for the site. Social vocalization source levels were found to range from 123 to 183 dB re 1 mu Pa @ 1 m with a median of 158 dB re 1 mu Pa @ 1 m. Source levels of surface-generated social sounds ("breaches" and "slaps") were narrower in range (133 to 171 dB re 1 mu Pa @ 1 m) but slightly higher in level (median of 162 dB re 1 mu Pa @ 1 m) compared to vocalizations. The data suggest that group composition has an effect on group vocalization source levels in that singletons and mother-calf-singing escort groups tend to vocalize at higher levels compared to other group compositions. VC 2013 Acoustical Society of America

Concurrent chemoradiotherapy for squamous cell carcinoma of the anus using a shrinking field radiotherapy technique without a boost

Chemoradiotherapy (CRT) is now widely accepted as the primary treatment modality for squamous cell cancer of the anus. While randomised trials have clearly shown CRT to be more effective than radiotherapy alone, there remains uncertainty over the optimal integration of chemotherapy and radiation. We describe a series of 50 patients treated by a site specialist gastrointestinal nonsurgical oncologist with CRT at a single UK centre. Chemotherapy comprised mitomycin C (MMC) (day 1) and 5-fluorouracil (5-FU) (days 1–4, and 29–32), concurrent with 50 Gy in 25 fractions radiation, using a two-phase shrinking field technique. A radiation boost was not planned. At a median follow-up of 48 months, 11 (22%) of the patients have failed locally, of which three have been surgically salvaged. Nine (18%) have died of anal cancer. These results are comparable with those from large randomised studies, and suggest that a two-phase shrinking field radiotherapy technique with no boost, concurrent with MMC/5-FU chemotherapy, is an effective regimen for this disease. The CRT regimen described here provides the basis for the ‘control arm’ of the current UK-randomised CRT trial in anal cancer (ACT2)

Lift Energy Storage Technology: A solution for decentralized urban energy storage

The world is undergoing a rapid energy transformation dominated by growing capacities of renewable energy sources, such as wind and solar power. The intrinsic variable nature of such renewable energy sources calls for affordable energy storage solutions. This paper proposes using lifts and empty apartments in tall buildings to store energy. Lift Energy Storage Technology (LEST) is a gravitational-based storage solution. Energy is stored by lifting wet sand containers or other high-density materials, transported remotely in and out of the lift with autonomous trailer devices. The system requires empty spaces on the top and bottom of the building. An existing lift can be used to transport the containers from the lower apartments to the upper apartments to store energy and from the upper apartments to the lower apartments to generate electricity. The installed storage capacity cost is estimated at 21 to 128 USD/kWh, depending on the height of the building. LEST is particularly interesting for providing decentralized ancillary and energy storage services with daily to weekly energy storage cycles. The global potential for the technology is focused on large cities with high-rise buildings and is estimated to be around 30 to 300 GWh