Photovoltaic Power Production Research Articles

Local and regional photovoltaic power prediction for large scale grid integration: Assessment of a new algorithm for snow detection

ABSTRACTLarge‐scale grid integration of photovoltaic (PV) power requires forecast information on the expected PV power for all levels of electricity supply systems. Regional PV power forecasts provide the basis for grid management and trading of PV power on the energy market. On the local scale, smart grid applications define a sector with increasing need for PV power forecasting. Here, we present and evaluate new and enhanced features of the regional PV power prediction system of the University of Oldenburg and Meteocontrol GmbH. The basic approach to predict regional PV power with an hourly resolution of up to 2 days ahead is based on global model forecasts of the European Centre for Medium‐Range Weather Forecasts (ECMWF) and includes explicit physical modelling steps to convert the predicted solar irradiance into PV power. The proposed new, empirical approach aims at improving PV power predictions during periods of snow cover, where the original forecasts usually show a strong overestimation of the power production. The approach integrates measured PV power production data and additional meteorological forecast parameters. The new approach for power forecasting has been evaluated against the operational forecasts for the control area of the German transmission system operator ‘50Hertz Transmission GmbH’ for a 1‐year period. The root mean square error (rmse) of the forecasts could be reduced from 4.9% to 3.9% for intra‐day forecasts, and from 5.7% to 4.6% for day‐ahead forecasts. The largest improvement was found during January, where the rmse could be reduced by more than half by applying the proposed algorithm for snow detection. Copyright © 2011 John Wiley & Sons, Ltd.

Local Reactive Power Control Methods for Overvoltage Prevention of Distributed Solar Inverters in Low-Voltage Grids

The main objective of this study is to increase the penetration level of photovoltaic (PV) power production in low-voltage (LV) grids by means of solar inverters with reactive power control capability. This paper underlines weak points of standard reactive power strategies which are already imposed by certain grid codes, and then, the study introduces a new reactive power control method that is based on sensitivity analysis. The sensitivity analysis shows that the same amount of reactive power becomes more effective for grid voltage support if the solar inverter is located at the end of a feeder. Based on this fundamental knowledge, a location-dependent power factor set value can be assigned to each inverter, and the grid voltage support can be achieved with less total reactive power consumption. In order to prevent unnecessary reactive power absorption from the grid during admissible voltage range or to increase reactive power contribution from the inverters that are closest to the transformer during grid overvoltage condition, the proposed method combines two droop functions that are inherited from the standard cos φ(P) and Q(U) strategies. Its performance comparison in terms of grid losses and voltage variation with different reactive power strategies is provided by modeling and simulating a real suburban LV network.

Energy Management and Operational Planning of a Microgrid With a PV-Based Active Generator for Smart Grid Applications

The development of energy management tools for next-generation PhotoVoltaic (PV) installations, including storage units, provides flexibility to distribution system operators. In this paper, the aggregation and implementation of these determinist energy management methods for business customers in a microgrid power system are presented. This paper proposes a determinist energy management system for a microgrid, including advanced PV generators with embedded storage units and a gas microturbine. The system is organized according to different functions and is implemented in two parts: a central energy management of the microgrid and a local power management at the customer side. The power planning is designed according to the prediction for PV power production and the load forecasting. The central and local management systems exchange data and order through a communication network. According to received grid power references, additional functions are also designed to manage locally the power flows between the various sources. Application to the case of a hybrid supercapacitor battery-based PV active generator is presented.

The costs and benefits of large-scale solar photovoltaic power production in Abu Dhabi, United Arab Emirates

The potential for a 10 MW photovoltaic power plant in Abu Dhabi is examined in this paper using RETScreen modeling software to predict energy production, financial feasibility and GHG emissions reductions. Initial results show high energy production potential, generating 24 GWh and saving over 10,000 tons of GHG emissions annually, but poor financial prospects yielding a net present value (NPV) of −$51 million. Benefits of reducing GHG and air pollution emissions by replacing natural gas with PV generation are calculated to have a net present value of $47 million, with a large range of possible values. Results show that the high initial costs and low expected price for electricity generated are driving reasons why photovoltaic systems are not being implemented in Abu Dhabi. A feed-in tariff rate of $0.16/kWh is recommended to make large-scale PV systems profitable.

Forecasting photovoltaic array power production subject to mismatch losses

The development of photovoltaic (PV) energy throughout the world this last decade has brought to light the presence of module mismatch losses in most PV applications. Such power losses, mainly occasioned by partial shading of arrays and differences in PV modules, can be reduced by changing module interconnections of a solar array. This paper presents a novel method to forecast existing PV array production in diverse environmental conditions. In this approach, field measurement data is used to identify module parameters once and for all. The proposed method simulates PV arrays with adaptable module interconnection schemes in order to reduce mismatch losses. The model has been validated by experimental results taken on a 2.2 kWp plant, with three different interconnection schemes, which show reliable power production forecast precision in both partially shaded and normal operating conditions. Field measurements show interest in using alternative plant configurations in PV systems for decreasing module mismatch losses. 2010 Elsevier Ltd. All rights reserved.

Laser processing of multicrystalline silicon for texturization of solar cells

Abstract The subject of the present paper is to design the technique of laser texturization for solar cells made of multicrystalline silicon and improve understanding of the interaction between laser light and workpiece. We explore how different transverse modes influence laser surface treatment and examine some details related to laser multimodal operation. Since constant increase in global production of photovoltaic power can be observed the new technologies for manufacturing solar cells of improved efficiency are developed. One of the most important factors influencing cells performance is reflectivity of its front side. Consequently, new methods for efficient reduction of reflectance are searched. One of the crucial stages which is carried out to increase solar radiation absorption is surface texturization. It is brought under well control for solar cells made of monocrystalline silicon. However, from the market point of view the reduction of production costs has essential meaning. As a result, the market share of multicrystalline cells systematically grows since the base material is approximately twice cheaper compared to monocrystalline silicon. But on the other hand, texturization methods used for monocrystalline silicon are ineffective in the case of multicrystalline silicon. Thus, it seems to be very interesting to investigate new alternative methods for effective texturization of multicrystalline silicon. One of the promising technologies is laser processing which is the subject of present paper.

New helio-photocatalytic–photovoltaic hybrid system for simultaneous water decontamination and solar energy conversion

Test results for a designed and installed hybrid photocatalytic–photovoltaic system (HPPS) are presented in this paper. The HPPS consists of one device with dual functions: The photocatalytic system uses UV radiation to promote degradation of organic pollutants, and beside it absorbs the IR radiation. The photovoltaic (PV) system converts the visible radiation into electricity, which can either be used directly by the recirculation pump or stored in a battery for other purposes. The suggested design aims to achieve an autonomous, environmentally friendly method for the treatment of biorecalcitrant pollutants. Two prototypes were erected: HPPS P , using Plexiglas and HPPS G using commercial glass. Both were tested outdoors to determine their impact on photovoltaic power production. Test results showed that PV power diminished to 14% and 22% for HPPS G and HPPS P respectively, compared to a PV panel alone.

Photovoltaics in the Swedish power system?

SYNOPSIS The Swedish Dower system is today based on hydro power (production 65 TWh/year) and nuclear power (production 55 TWh/year from 1986). Small amount of oil and gas is used for power production during peak periods. The Swedish Parliament decided in 1980, after a consultative referendum, that all nuclear reactors will be closed between 1997 and 2010. In that perspective several new technologies are possible to use for power production. One interesting possibility is photovoltaic power production. The objective of the paper is to analyse conditions for the use of photovoltaics in the Swedish power system. The cost for electricity from photovoltaic power plants is calculated from cost goals in the United States photovoltaic development programme. Different costs during construction and operation are added. The capital costs are calculated for a real discount rate of 4% and the lifetime for the plant is assumed to be 30 years. The receipts for photovoltaics are calculated from long run marginal revenues (power values) at year 2010. The calculations give following results. If the lower cost goal for late 1990s is achieved, then electricity from photovoltaic power plants in Sweden will cost 3.6 pence/kwh (40 öre/kwh). The higher cost goal for 1990s results in an energy cost of 4.6 pence/kwh (51 öre/kWh). The cost for electricity from photovoltaic power plants will be the same as the cost for electricity from coal-fired power plants if the coal price rises from UK £ l.3/GJ during 1983 to UK £3.4–4.5/GJ around the decade 2000–2010.

Concentrator cost bound for high-efficiency photovoltaic power production

An upper bound on the cost per unit aperture area of a solar concentrator is obtained which is completely model independent. The result relates the maximum cost of a concentrator system (if it is to be competitive with low efficiency, low cost solar cell arrays) to the efficiency of photocells comprising an array. (SPH)