Chuck Whitaker

Spectral solar radiation data base at SERI

Abstract This article describes the results to date of a cooperative project among the Solar Energy Research Institute (SERI), the Electric Power Research Institute, the Florida Solar Energy Center (FSEC), and the Pacific Gas and Electric Company (PG&E) to build a spectral solar radiation data base. The objective is to build a data base representing a range of air masses and atmospheric conditions (or climates) that is applicable to different photovoltaic (PV) collector types and is accessible by the PV and general scientific community. Approximately 1300 spectra and concurrent broadband solar radiation and meteorological data have been collected at FSEC and PG&E and archived at SERI in the data base as of October 1987.

Photovoltaic module energy rating methodology development

A consensus-based methodology to calculate the energy output of a PV module is described in this paper. The methodology develops a simple measure of PV module performance that provides for a realistic estimate of how a module will perform in specific applications. The approach makes use of the weather data profiles that describe conditions throughout the United States and emphasizes performance differences between various module types. An industry-representative Technical Review Committee has been assembled to provide feedback and guidance on the strawman and final approach used in developing the methodology.

Review of potential problems and utility concerns arising from high penetration levels of photovoltaics in distribution systems

This paper presents the results of a literature search and utility engineer survey on the subject of system-level impacts of high penetration levels of photovoltaics, undertaken by the authors as part of the Department of Energys Renewable Systems Integration (RSI) project in 2007. The primary concerns associated with high PV penetration as described by the body of literature and by currently-practicing utility engineers are presented.

Outdoor meteorological broadband and spectral conditions for evaluating photovoltaic modules

The choice of conditions that should be used for rating photovoltaic modules is revisited to assess how well they represent the real world. One part of this study looks at the meteorological conditions and broadband characteristics of the irradiance when the global irradiance is 1000 W/m/sup 2/. Global normal irradiance on a 2-axis-tracked surface of 1000 W/m/sup 2/ was found to be correlated with a direct normal irradiance of 836 W/m/sup 2/, an ambient temperature of 23.7/spl deg/C, a wind speed of 4.5 m/s, a total water vapor of 1.4 cm, an aerosol optical depth of 0.08, and an air mass of 1.43. The second part of the study investigates the direct normal spectra that are commonly observed and concludes that of the two reference spectra that are commonly used, the global 37/spl deg/ tilt reference spectrum (ASTM E892) better represents observed data. Spectral modeling identifies a set of conditions for which the direct normal spectrum is very similar to ASTM E892.

Photovoltaics for utility-scale applications : project overview and data analysis

Abstract PVUSA, a national cooperative research and development project, is cofunded by the U.S. Department of Energy (DOE), the California Energy Commission (CEC)/State of California, the Electric Power Research Institute (EPRI), Pacific Gas and Electric (PGE and to create a program to transfer PV knowledge between government, the PV industry, and other utilities. Two 20 kW arrays are now installed in Davis, and the completion of three more is expected this year. Award negotiations are now under way to procure additional 20 kW arrays and several Utility Scalable (US) PV systems that will include tracking and fixed structures and use innovative balance of system designs. These US systems will be either 200 or 400 kW. PVUSA has adopted rating criteria that allow array/system peak performance to be described under outdoor operating conditions. This method for describing performance is believed to be more useful to utility users than extrapolation of data from PV modules flash-tested in a laboratory. A simple regression model is used to rate each system at the PVUSA Test Conditions based on about 30 days of measured outdoor data. The resulting equation can be used by other utilities to site a duplicate system hypothetically in their own territory.

Certification of photovoltaic inverters: the initial step toward PV system certification

There is no complete photovoltaic product (component or system) certification program in effect today in the United States. Photovoltaic (PV) modules and inverters are listed for safety (using standards UL1703 and UL1741, respectively), and certification for environmental qualification of PV modules is conducted. However these do not provide critical performance information such as PV module energy rating, inverter performance characteristics, or system performance. Domestic and international standards organizations have begun waiting requirements for photovoltaic system certification that are aimed primarily at small stand-alone applications. The module and balance-of-system industries often provide inconsistent or insufficient specifications and data to designers and customers to allow adequate comparison or a true prediction of performance for installed systems. This paper describes an industry consensus process to establish necessary testing protocols for certification of inverters.

PV module performance outdoors at PG&E

The 1989 performances of 38 PV (photovoltaic) modules installed outdoors at PG&Es PV Test Facility in San Ramon, California, are evaluated. Performance improvements with each generation of PV modules indicate the progress of PV. Efficiencies greater than 12% have been measured. Within each PV technology, module performance tends to follow parallel month-to-month trends. Even after initial degradation, amorphous silicon modules have the greatest month-to-month variations. Monthly averaged efficiency is within +or-10% of annually averaged efficiency for amorphous silicon modules after initial performance degradation and within +or-6% for the single-crystal silicon, polycrystalline silicon, ribbon silicon, bifacial silicon, and concentrating silicon modules evaluated.<<ETX>>

Thin-film PV performance at PG&E

Abstract The outdoor performance of photovoltaic (PV) modules is monitored at PG&Es PV Test Facility in San Ramon, CA. This paper evaluates the performance through mid-1989 of commercially available amorphous silicon (a-Si) PV modules manufactured by ARCO Solar, Chronar, Solarex, Sovonics, and Utility Power Group. All of the modules have exhibited efficiency degradation on initial sun exposure. Module efficiencies are initially 5 – 6% and appear to stabilize around 4% after 1 yr of outdoor exposure. The a-Si modules installed in 1985 which initially operated at 5% efficiency have maintained 4% efficiency for the last 3 yrs.

Inverter Performance Certification: Results from the Sandia Test Protocol

This paper discusses results of the work to develop a test protocol for evaluating PV inverter performance, results obtained by testing to the protocol as required by the California Energy Commission (CEC), and the use of those results to develop and evaluate inverter performance models. This paper presents preliminary results of the modeling effort, comparing the models derived from CEC data with field measurements from sample systems. In addition to predicting system performance, this model may prove equally useful in evaluating the quality of the data generated by performing the test protocol

PG&E experience with a 10-kW commercial rooftop PV system

Pacific Gas and Electric Company (PG&E) is one of eleven electric utilities that participated in the first phase of the US Environmental Protection Agencys Photovoltaic Demand-Side Management (PV-DSM) Program. PG&E participation involved the December 1993 installation and subsequent testing of a 10 kW/sub AC/ PV power system on a PG&E-owned building in San Ramon, California, USA. The performance of the system supports the technical readiness of rooftop-mounted PV systems.