Impact of Short-Term Variations in the Generation Output of Geographically Dispersed PV Systems

When viewed in hourly intervals, a solar photovoltaic (PV) system appears to have a more stable output than usual. However, there are short-term rapid variations in its generation output that result from transient cloudiness and weather disturbances in the atmosphere. By using Monte Carlo simulations applied to a Markov model, this study demonstrates the short-term intermittency of the transient weather conditions and estimates the generation of geographically dispersed PV systems with a capacity of ten percent of peak demand of a statewide grid in one-minute intervals. This study found that geographically distributed PV systems evaluated in one-minute intervals could cope with peaks of a statewide power grid because of the smoothing effect caused by the geographical spread. The purpose of the exercise is to create a framework for integration and optimization of multiple generation sources in order to meet the uncertainty of the fast changing PV output under certain weather conditions.

Concomitant multiple anomalies of renal vessels and collecting system

Although anomalies of renal vessels and collecting system are relatively frequent, their concomitant occurrence is a rare event. During dissection of a 75-year-old male formalin-embalmed cadaver, we found multiple variations in the renal vessels and renal collecting system. Both kidneys were normal in size and anteriorly malrotated, with duplex collecting system and duplex ureter. One ureter drained the upper part of the kidney and the second ureter drained the lower part of the kidney. Superior and inferior collecting systems were separated by renal parenchyma. The right kidney had two renal arteries, the first renal artery (main renal artery) originating from the abdominal aorta, passing behind the inferior vena cava (IVC) and entering the kidney through the superior and inferior renal hilum. The second artery was the inferior polar artery. In addition, the right kidney had two renal veins as well. Three renal tributaries emerged from the upper and lower portion of the right renal hilum, and they joined to form the main renal vein which drained into the IVC. The lower renal vein was the inferior polar vein. The left kidney had four renal arteries (two hilar arteries and two polar arteries). The main left renal vein emerged from both superior and inferior left renal hilum, passed in front of the abdominal aorta and drained into the IVC. The left kidney also had the inferior polar vein which was divided behind the aorta (retro aortic vein) into two venous trunks. These venous trunks drained separately into posteromedialaspect of the IVC. Finally, the right testicular vein was formed by two tributaries and drained into the IVC, whereas the two left testicular veins drained separately into the left main renal vein