Howard J. Wenger

Distributed generation: An alternative to electric utility investments in system capacity

Distributed generation technologies offer electric utilities an alternative to large system capacity investments. This paper presents a simplified method to determine the value of deferring electric utility capacity investments using distributed generation. Consideration is given to both economic and technical factors, including uncertainty in the price of distributed generation. The technical evaluation is based on measured data from a 500 kW distributed generation PV plant in Kerman, California. Results indicate that the cost savings associated with deferring capacity investments can be accurately estimated using only seven economic parameters and one days worth of distributed generation output and utility system data.

Decline of the Carrisa Plains PV power plant: the impact of concentrating sunlight on flat plates

The Carrisa Plains photovoltaic (PV) power plant located in central California has steadily degraded in performance since 1986 at a rate of approximately 10% per year. Originally rated at 5.2 MW, the plant routinely produced less than 3 MW as of 1990. The plant is composed of two-axis trackers with single-crystalline flat plate modules, and over 90% of the trackers have V-trough mirrors to concentrate sunlight. This low-concentration design has caused an accelerated browning of the modules and is the cause of the plants decline. Electrical testing was performed to investigate the ramifications of module browning. The results indicate that ethylene-vinyl acetate (EVA) browning is an important concern for the PV industry and that low-concentration designs should not be used for one-sun flat plate modules until the issue has been resolved.<<ETX>>

Carrisa Plains PV power plant performance

The authors summarize the performance of the worlds largest PV (photovoltaic) power plant (the one at Carrisa Plains, California) for 1984-1989. Although the plant has high availability, energy production efficiency has declined at the rate of 8-12% per year since 1986. Based on the data, it is difficult to provide a thorough explanation for the steady decline in Carrisa Plains PV performance. The core problem has largely been attributed to the thermal oxidation of ethylene vinyl acetate PV cell encapsulant caused by elevated temperatures of the mirrored segments. The PV modules, originally dark blue in color, are now brown. A number of possibilities exist which may contribute to the plants decline in power output, such as mismatching, leakage currents, inappropriate inverter operating point, and changes in maintenance. Performance results of the mirrored and nonmirrored segments are presented These results indicate that the nonmirrored segment is performing well with minimal efficiency degradation and low operation and maintenance costs.<<ETX>>

PVUSA-the first decade of experience

Photovoltaics for Utility Scale Applications (PVUSA) is a national cooperative research and development project with a mission to acquire information through field installation and testing of grid-connected photovoltaic (PV) technologies and to provide the information to utilities and other participants. This paper updates the projects progress and summarizes performance, cost, and value results obtained in the 10 years since project inception.

Economic determination of optimal plant design for photovoltaics in the utility distribution system

A simplified value analysis tool which is to be used in optimizing the design of a distributed grid-connected photovoltaic (PV) plant is presented. The resulting distributed value information may be combined with cost information to determine the most optimal plant design. The methodology and the data necessary to apply this methodology to a specific case are presented.<<ETX>>

Electrical Degradation of the Carrisa Plains Power Plant

The Carrisa Plains photovoltaic power plant located in central California has shown steady degradation in electrical performance since 1986. Originally rated at 5.2 MW ac, the plant routinely produced less than 3 MW as of 1990. Degradation is apparently due to so-called “brown cell,” a misnomer because the brown color of the modules is in fact due to discoloration of the EVA encapsulant between the cover glass and the cells, and not discoloration of the cells. This paper describes the plant’s design; performance since 1984; testing performed in 1990; physical and electrical characteristics of modules, panels, and trackers; and the 1991 status of the plant. The paper concludes with lessons applicable to future power plant designs.

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.

PV-DSM: policy actions to speed commercialization

Pacific Gas and Electric Company (PG&E) recently applied demand-side management (DSM) evaluation techniques to photovoltaic (PV) technology to develop the concept of photovoltaics as a demand-side management option (PV-DSM). The analysis demonstrated that PV-DSM has the potential to be economically attractive. Two criticisms in response to that analysis are that the assumptions of 25 year financing and a 25 year evaluation period are unrealistic. This paper responds to those criticisms and documents the mathematical relationships to calculate the value of PV-DSM from a customers perspective. It demonstrates how regulatory and government agencies could implement policies to resolve both issues and speed PV commercialization.<<ETX>>

Photovoltaic research at Pacific Gas and Electric Company

Cost-effective photovoltaic (PV) use by utilities is anticipated to extend beyond todays small, stand-alone installations to grid support, villages and islands, and customer-sited applications before PV enters peaking and bulk power markets. PV research at Pacific Gas and Electric Company has evolved since 1980 to demonstrate the technology and stimulate utility consideration and acceptance of PV.<<ETX>>

Reduce, reuse and renew: one possible approach to cut carbon emissions

Global climate change has become an increasingly important issue over the last several years. This issue reached a climax at the Kyoto Conference in December, 1997 where the US agreed to reduce its greenhouse gas emissions to 7% under its 1990 levels by 2010. This paper describes how distributed resources could be part of an overall solution towards achieving these reductions. It illustrates how a system composed of energy efficiency, distributed cogeneration, and distributed photovoltaics could reduce fuel consumption by 70% in the residential and commercial sectors. This could be a solution that makes economic sense independent of the climate change debate if implemented over the next 30 to 50 years, a timeframe which is not much worse for the climate system than achieving them in ten years, according to most analyses.