Spatiotemporal Analysis of Irradiance Data using Kriging

Solar power variability is a concern to grid operators as unanticipated changes in photovoltaic (PV) plant power output can strain the electric grid. The main cause of solar variability is clouds passing over PV modules. However, geographic diversity across a region leads to a reduction in cloud-induced variability, but the reduction depends on cloud speed. To illustrate the magnitude of solar variability, irradiance and PV power output datasets are first evaluated, validated and applied to detect the largest aggregate ramp rates in California. Afterwards, spatiotemporal correlations of irradiance data are analyzed and cloud motion is estimated using two different methods; the cross-correlation method (CCM) applied to two or a few consecutive time steps and cross-spectral analysis (CSA) where the cloud speed and direction are estimated by cross-spectral analysis of a longer timeseries. CSA is modified to estimate the cloud motion direction as the case with least variation for all the velocities in the cloud motion direction. To ensure reliable cloud motion estimation, quality control (QC) is added to the CSA and CCM. The results show 33% (52°) and 21% (6°) improvement in the cloud motion speed (direction) estimation using the modified CSA and CCM over the original methods (without QC), respectively.Spatial and spatiotemporal ordinary Kriging methods are applied to model irradiation at an arbitrary point. The correlations among the irradiances at observed locations are modeled by general parametric covariance functions. Besides the isotropic covariance function (which is independent of direction), a new non-separable anisotropic parametric covariance function is proposed to model the transient clouds. Also, a new approach is proposed to estimate the spatial and temporal decorrelation distances analytically using the applied parametric covariance functions, which reduced the size of the computations without loss in accuracy (parameter shrinkage). Results confirm that the non-separable anisotropic parametric covariance function is most accurate with an average normalized root mean squared error (nRMSE) of 7.92% representing a 66% relative improvement over the persistence model.The results confirm the accuracy and reliability of the Kriging method for estimating irradiation at an arbitrary point even in more challenging real applications where cloud motion is unknown

Innovative and sustainable membrane technology for wastewater treatment and desalination application

This chapter provides an overview on the innovative and sustainable development of membrane technology in wastewater treatment and desalination. The membrane processes based on hydraulic pressure and osmotic pressure are first outlined. The development and recent progresses made in the design and fabrication of high-performance membranes are discussed. The applications of membrane technologies in wastewater treatment, desalination, and energy generation are reviewed. Finally, the future outlook is briefly highlighted and the conclusion is drawn

Solar Resource Variability

International audienc

Antibacterial Envelope to Prevent Cardiac Implantable Device Infection

Background Infections after placement of cardiac implantable electronic devices (CIEDs) are associated with substantial morbidity and mortality. There is limited evidence on prophylactic strategies, other than the use of preoperative antibiotics, to prevent such infections. Methods We conducted a randomized, controlled clinical trial to assess the safety and efficacy of an absorbable, antibiotic-eluting envelope in reducing the incidence of infection associated with CIED implantations. Patients who were undergoing a CIED pocket revision, generator replacement, or system upgrade or an initial implantation of a cardiac resynchronization therapy defibrillator were randomly assigned, in a 1:1 ratio, to receive the envelope or not. Standard-of-care strategies to prevent infection were used in all patients. The primary end point was infection resulting in system extraction or revision, long-term antibiotic therapy with infection recurrence, or death, within 12 months after the CIED implantation procedure. The secondary end point for safety was procedure-related or system-related complications within 12 months. Results A total of 6983 patients underwent randomization: 3495 to the envelope group and 3488 to the control group. The primary end point occurred in 25 patients in the envelope group and 42 patients in the control group (12-month Kaplan-Meier estimated event rate, 0.7% and 1.2%, respectively; hazard ratio, 0.60; 95% confidence interval [CI], 0.36 to 0.98; P=0.04). The safety end point occurred in 201 patients in the envelope group and 236 patients in the control group (12-month Kaplan-Meier estimated event rate, 6.0% and 6.9%, respectively; hazard ratio, 0.87; 95% CI, 0.72 to 1.06; P<0.001 for noninferiority). The mean (+/- SD) duration of follow-up was 20.7 +/- 8.5 months. Major CIED-related infections through the entire follow-up period occurred in 32 patients in the envelope group and 51 patients in the control group (hazard ratio, 0.63; 95% CI, 0.40 to 0.98). Conclusions Adjunctive use of an antibacterial envelope resulted in a significantly lower incidence of major CIED infections than standard-of-care infection-prevention strategies alone, without a higher incidence of complications