Defining Requirements for Improved Photovoltaic System Reliability

Reliable systems are an essential ingredient of any technology progressing toward commercial maturity and large-scale deployment. This paper defines reliability as meeting system fictional requirements, and then develops a framework to understand and quantify photovoltaic system reliability based on initial and ongoing costs and system value. The core elements necessary to achieve reliable PV systems are reviewed. These include appropriate system design, satisfactory component reliability, and proper installation and servicing. Reliability status, key issues, and present needs in system reliability are summarized for four application sectors

Adaptive and mobile ground sensor array.

The goal of this LDRD was to demonstrate the use of robotic vehicles for deploying and autonomously reconfiguring seismic and acoustic sensor arrays with high (centimeter) accuracy to obtain enhancement of our capability to locate and characterize remote targets. The capability to accurately place sensors and then retrieve and reconfigure them allows sensors to be placed in phased arrays in an initial monitoring configuration and then to be reconfigured in an array tuned to the specific frequencies and directions of the selected target. This report reviews the findings and accomplishments achieved during this three-year project. This project successfully demonstrated autonomous deployment and retrieval of a payload package with an accuracy of a few centimeters using differential global positioning system (GPS) signals. It developed an autonomous, multisensor, temporally aligned, radio-frequency communication and signal processing capability, and an array optimization algorithm, which was implemented on a digital signal processor (DSP). Additionally, the project converted the existing single-threaded, monolithic robotic vehicle control code into a multi-threaded, modular control architecture that enhances the reuse of control code in future projects

Video-assisted thoracic surgery (VATS) for resection of metastatic adenocarcinoma as an acceptable alternative

Adenocarcinomas commonly metastasize to the lungs and can be resected using open thoracotomy or video-assisted thoracic surgery (VATS). This study reviews metastatic resections in primary adenocarcinoma patients, using both thoracotomy and VATS. We aim to compare long-term prognoses to test the efficacy and viability of VATS. A retrospective review of primary adenocarcinoma patients who underwent resection of pulmonary metastases from 1990 to 2006 was carried out. Information was obtained by chart review. Endpoints analyzed were disease-free interval (DFI), survival time, and recurrence-free survival (RFS). In a total of 42 (16 male, 26 female; median age 58.5 years) primary adenocarcinoma patients, 21 patients underwent first pulmonary metastatic resection using VATS (7 male, 14 female; median age 57 years) and 21 using thoracotomy (9 male, 12 female; median age 59 years). Primary adenocarcinomas were mainly 27 colorectal (64%) and 11 breast (26%). Two VATS (10%) and three open patients (14%) had local recurrences of the original cancer. Median postoperative follow was 13.3 months [interquartile range (IQR) 4.5–32.8 months] for VATS and 36.9 months (IQR 19.3–48.6 months) after thoracotomy. Median DFI–1 was 22.3 months (IQR 13.5–40.6 months) for VATS patients and 35.6 months (IQR 26.7–61.3 months) for open patients. Second thoracic occurrences were noted in six VATS patients (median DFI–2 9.2 months), and in seven open patients (median DFI-2 21.5 months). Third thoracic occurrences were noted in one VATS patient (DFI-3 18.7 months) and in one thoracotomy patient (DFI-3 21.8 months). Odds ratio of recurrence showed 12.5% less chance of developing recurrence in VATS patients. Five-year RFS was 53% in VATS and 57% in thoracotomy patients. VATS has become a viable alternative to open thoracotomy for resection of pulmonary metastases. In cases of primary adenocarcinoma, VATS showed no increase in number of thoracic recurrences, and comparable RFS. Short-term follow-up is encouraging; long-term follow-up will be needed to confirm these results

Long-term follow-up of patients with previous myocarditis using radionuclide ventriculography

A prospective long-term follow-up study is reported of 18 of 19 patients who survived a bout of presumed myocarditis 6–136 months (average 54 months) previously. The study included 14 males and four females, ranging from 27 to 63 years of age (mean, 44 years). Chest X-ray, ECG, echocardiogram, and resting and exercise radionuclide ventricular ejection fraction (RNVEF) for assessment of ventricular function were evaluated at follow-up. Resting and exercise RNVEF from seven control subjects were evaluated for comparison. Residual abnormalities were noted in chest X-ray (16%), echocardiogram (30%), and ECG (55%) in these predominantly asymptomatic patients (17/18 or 95%). The resting RNVEF (mean ±SD) for the myocarditis group versus controls were 0.57±0.1 and 0.65±0.1 ( P =NS), respectively. The exercise RNVED for the myocarditis group versus controls were 0.56±0.1 and 0.74±0.05 ( P <0.01), respectively. Abnormal resting RNVEF was noted in six (33%) and exercise RNVEF in 14 (77%) patients in the myocarditis group. Two patients with abnormal exercise RNVEF subsequently developed findings consistent with dilated cardiomyopathy. It is unclear as to whether the abnormal ventricular function may serve as a marker for future development of dilated cardiomyopathy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41583/1/380_2005_Article_BF02072391.pd

Minimally invasive surgery and cancer: controversies part 1

Perhaps there is no more important issue in the care of surgical patients than the appropriate use of minimally invasive surgery (MIS) for patients with cancer. Important advances in surgical technique have an impact on early perioperative morbidity, length of hospital stay, pain management, and quality of life issues, as clearly proved with MIS. However, for oncology patients, historically, the most important clinical questions have been answered in the context of prospective randomized trials. Important considerations for MIS and cancer have been addressed, such as what are the important immunologic consequences of MIS versus open surgery and what is the role of laparoscopy in the staging of gastrointestinal cancers? This review article discusses many of the key controversies in the minimally invasive treatment of cancer using the pro–con debate format

Joint DOE/Industry Photovoltaic System Reliability Program

To achieve the lowest life-cycle cost (LCC), photovoltaic (PV) systems must have the optimum mix of low first cost, low operation and maintenance (O&M) cost, and high availability. Additionally, the long-term health of the photovoltaic (PV) industry requires that PV systems work as expected. Although PV modules now enjoy high reliability due to a significant multi-year effort by both the U.S. Department of Energy (DOE) and industry, the same is not always true of PV systems. Even for systems that do operate reliably, customers, suppliers, and manufacturers can benefit from knowing what O&M expenses to expect. This knowledge will reduce technology risk to the customer and improve likelihood of commitment to PV projects. System integrators and utilities may benefit from O&M cost information to improve system designs, to properly price service agreements and warranties, and to optimize maintenance strategies. The DOE and component manufacturers may benefit from identifying cost drivers to optimally focus research and quality assurance resources to improve product reliability. This paper discusses the first of five tasks identified for this project, quantifying system reliability and life cycle cost by collecting, analyzing and reporting data on PV system reliability and cost. Industry participants collect the necessary O&M data on systems they are monitoring. Sandia provides support in the form of assistance identifying data that needs to be collected, helping develop forms or databases to collect the data, and analyzing the data

Photovoltaic System Reliability

This paper discusses the reliability of several photovoltaic projects including SMUD`s PV Pioneer project, various projects monitored by Ascension Technology, and the Colorado Parks project. System times-to-failure range from 1 to 16 years, and maintenance costs range from 1 to 16 cents per kilowatt-hour. Factors contributing to the reliability of these systems are discussed, and practices are recommended that can be applied to future projects. This paper also discusses the methodology used to collect and analyze PV system reliability data

Solartrak{trademark} Controller Developments for Today's Applications

The SolarTrak{trademark} array tracking controller, originally developed and licensed by Sandia National Laboratories as a low-cost, high-accuracy, reliable controller for photovoltaic (PV) concentrator arrays, has undergone significant development to make tracking accessible to a much broader segment of the PV market. Hardware and software improvements (1) reduce power consumption for PV/battery- powered applications, (2) enable the controller to connect directly with low-cost, off-the-shelf, television satellite dish actuators, (3) enable on-site setup without an additional input board, (4) increase clock accuracy by providing daily and weekly adjustments to the on board clock, and (5) include a low-cost wind stow sensor. The result is a stand-alone tracking system sufficiently low cost and reliable to make 1-kW tracking systems practical for flat plate and concentrating arrays. Results of a year of testing are presented showing clock accuracy better than a minute per year can be maintained

Characterization of Fuel Cell Vehicle Duty Cycle Elements

This report covers research done as part of US Department of Energy contract DE-PS26-99FT14299 with the Fuel Cell Propulsion Institute on the fuel cell RATLER{trademark} vehicle, Lurch, as well as work done on the fuel cells designed for the vehicle. All work contained within this report was conducted at the Robotic Vehicle Range at Sandia National Laboratories in Albuquerque New Mexico. The research conducted includes characterization of the duty cycle of the robotic vehicle. This covers characterization of its various abilities such as hill climbing and descending, spin-turns, and driving on level ground. This was accomplished with the use of current sensors placed in the vehicle in conjunction with a Data Acquisition System (DAS), which was also created at Sandia Labs. Characterization of the two fuel cells was accomplished using various measuring instruments and techniques that will be discussed later in the report. A Statement of Work for this effort is included in Appendix A. This effort was able to complete characterization of vehicle duty cycle elements using battery power, but problems with the fuel cell control systems prevented completion of the characterization of the fuel cell operation on the benchtop and in the vehicle. Some data was obtained characterizing the fuel cell current-voltage performance and thermal rise rate by bypassing elements of the control system