Commercial Photovoltaic Systems Research Articles

Assessment of Perturb and Observe MPPT Algorithm Implementation Techniques for PV Pumping Applications

The energy utilization efficiency of commercial photovoltaic (PV) pumping systems can be significantly improved by employing simple perturb and observe (P&O) maximum power point tracking algorithms. Two such P&O implementation techniques, reference voltage perturbation and direct duty ratio perturbation, are commonly utilized in the literature but no clear criteria for the suitable choice of method or algorithm parameters have been presented. This paper presents a detailed theoretical and experimental comparison of the two P&O implementation techniques on the basis of system stability, performance characteristics, and energy utilization for standalone PV pumping systems. The influence of algorithm parameters on system behavior is investigated and the various advantages and drawbacks of each technique are identified for different weather conditions. Practical results obtained using a 1080-Wp PV array connected to a 1-kW permanent magnet dc motor-centrifugal pump set show very good agreement with the theoretical analysis and numerical simulations.

The impact of retail rate structures on the economics of commercial photovoltaic systems in California

This article examines the impact of retail electricity rate design on the economic value of grid-connected photovoltaic (PV) systems, focusing on commercial customers in California. Using 15-min interval building load and PV production data from a sample of 24 actual commercial PV installations, we compare the value of the bill savings across 20 commercial-customer retail electricity rates currently offered in the state. Across all combinations of customers and rates, we find that the annual bill savings from PV, per kWh generated, ranges from $0.05 to $0.24/kWh. This sizable range in rate-reduction value reflects differences in rate structures, revenue requirements, the size of the PV system relative to building load, and customer load shape. The most significant rate design issue for the value of commercial PV is found to be the percentage of total utility bills recovered through demand charges, though a variety of other factors are also found to be of importance. The value of net metering is found to be substantial, but only when energy from commercial PV systems represents a sizable portion of annual customer load. Though the analysis presented here is specific to California, our general results demonstrate the fundamental importance of retail rate design for the customer-economics of grid-connected, customer-sited PV.

Emissions from Photovoltaic Life Cycles

Photovoltaic (PV) technologies have shown remarkable progress recently in terms of annual production capacity and life cycle environmental performances, which necessitate timely updates of environmental indicators. Based on PV production data of 2004-2006, this study presents the life-cycle greenhouse gas emissions, criteria pollutant emissions, and heavy metal emissions from four types of major commercial PV systems: multicrystalline silicon, monocrystalline silicon, ribbon silicon, and thin-film cadmium telluride. Life-cycle emissions were determined by employing average electricity mixtures in Europe and the United States during the materials and module production for each PV system. Among the current vintage of PV technologies, thin-film cadmium telluride (CdTe) PV emits the least amount of harmful air emissions as it requires the least amount of energy during the module production. However, the differences in the emissions between different PV technologies are very small in comparison to the emissions from conventional energy technologies that PV could displace. As a part of prospective analysis, the effect of PV breeder was investigated. Overall, all PV technologies generate far less life-cycle air emissions per GWh than conventional fossil-fuel-based electricity generation technologies. At least 89% of air emissions associated with electricity generation could be prevented if electricity from photovoltaics displaces electricity from the grid.

Photovoltaic research and demonstration activities at New England Electric

From 1985 onward, New England Electric has carried out and supported a wide range of research, development and demonstration projects related to the use of solar photovoltaic (PV) energy. This paper describes each project and summarizes performance to date. Several projects embody the concepts of distributed generation (DG) and demand-side management (DSM) as well as utilization of renewable energy. These residential and commercial grid-connected PV systems have reduced electrical demand at each site during the Company's summer peak hour from 1986 through 1993. In addition, during many of the hours around noon the residential systems have provided all of the energy for neighboring homes without PV systems. Transmission and distribution losses associated with the normal supply of energy to these sites was therefore minimized during these hours. On-site production of electricity via photovoltaics may also result in significant environmental benefits, particularly in summer, through displacement of energy from fossil-fueled peaking units. Other types of projects discussed include (1) a solar monitoring network, with simulation of electrical output for three types of PV systems, (2) a unique PV-assisted DC lighting system for a commercial building, (3) a large (100 kW) ground-mounted PV system, (4) a combination solar-PV and solar-thermal system, and (5) development of a single-module inverter.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance of grid-connected photovoltaic systems on residences and commercial buildings in New England

The focus is a detailed examination of energy production, including a discussion of the capacity value of photovoltaic (PV) systems in New England. Data are presented on the customer demand reduction potential of roof-mounted residential PV systems. It is shown that these systems can contribute, on average, 63% of their normalized capacity (1.8 kW) during 6-h peak load periods. The range of output is 34% to 80% during these periods. Reverse energy flow (customer to utility) from residential PV systems has been analyzed. The data indicate nonzero reverse energy flow for almost all participants in summer, and high amounts (approximately 50%) for one group of participants. The commercial and institutional PV systems generally operate in a more hostile electrical environment. In consequence, they have required more attention to maintain operating status and metering accuracy.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>