Solar power photovoltaics efficiency

Fig. 5.65 Dependence of the solar conversion efficiency (CE) on the threshold wavelength (Ag) for a quantum converter at AM 1.2. Curve 1 Fraction of the total solar power convertible by an ideal equilibrium converter with no thermodynamic and kinetic losses. Curve 2 As 1 but the inherent thermodynamic losses (detailed balance and entropy production) are considered. Continuous line Efficiency of a regenerative photovoltaic cell, where the thermodynamic and kinetic losses are considered. The values of Ag for some semiconductors are also shown (according to J. R. Bolton et al.)... 

Cells made from GaAs are more costly than silicon cells, because the production process is not as well developed, and gallium and arsenic are not abundant materials. GaAs cells have been used when very high efficiency is needed regardless of cost such as required in space applications. They were also used in the Sunraycer, a photovoltaic-powered electric car, which won the Pentax World Solar Challenge race for solar-powered vehicles in 1987. It ran the 3000-km from Darwin to Adelaide, Australia at an average day time speed of 66-km per hour. The 1990 race was won by a... 

The solar to electric power conversion efficiency of dye-sensitized solar cells of laboratory scale (0.158 cm2), validated by an accredited photovoltaic calibration laboratory, has reached 11.1% under standard reporting conditions, i.e., air mass 1.5 global sunlight at 1000 Wm-2 intensity and 298 K temperature, rendering it a credible alternative to conventional p-n junction photovoltaic devices [68]. Photovoltaic performance data obtained with a sandwich cell under illumination by simulated AM 1.5 solar light using complex 26 are shown in Fig. 16. At 1 sun the 26-sensitized solar cell exhibited 17.73 =b 0.5 mA current, 846 mV potential, and a fill factor of 0.75 yielding an overall conversion efficiency of 11.18%. 

Calculate the area of solar collection necessary to power a 300-kW lighter-than-air vehicle by means of photovoltaic cells (20% efficient), electrolyzing onboard water. Assume a 200-m-long dirigible (as an approximation, take its shape as cylindrical with a radius of 20 m). Could a hydrogen-lifted vehicle be solar powered but fly during darkness (Bockris)... 

Moore compared the technological branch of solar energy conversion, essentially photovoltaics, with the biological branch. He explained how a standard fuel cell that operates on oxygen and hydrogen produces water and electromotive force. A typical human-engineered fuel cell operates at 50-60 percent power conversion efficiency and uses platinum or other noble metals as catalysts. 

Power conversion efficiency (ri). Photovoltaic devices should be used for the direct conversion of sunlight to electricity. The intensity of solar radiation on the earth s surface when the sun s rays form an angle of 60° is about 691 W/m2 (AM2). The power conversion efficiency (ri) is... 

Rectification and photovoltaic effects in organic p-n junctions were first reported by Kearns and Calvin [101] and by Meier [3]. The combination of rhodamines or triphenylmethane dyes (both n-type) with merocyanines or phthalocyanines (both p-type) generated photovoltages up to 200 mV and photocurrents of about 10 8 A at low light intensity, with power conversion efficiency much less than 1%. More recent studies have been performed on merocyanine and malachite green [89,90] and on phthalocyanines and TPyP (a porphyrin derivative) [102,103]. These devices showed stronger spectral sensitization and better spectral match to a solar spectrum than those of Schottky barrier cells using only one component. 

In a regenerative solar energy conversion system, the device efficiency (r ) is simply given by the ratio of the power delivered by the photovoltaic converter and the incident solar power (Ps in W/m2 or mW/cm2). However, we are concerned here with devices producing a fuel (H2) and several expressions exist for the device efficiency. Thus, this efficiency can be expressed in kinetic terms 70192... 

Photovoltaic solar power conversion was the first major application proposed for a-Si H and to date is the largest in production. The first devices were reported by Carlson and Wronski in 1976 and had an efficiency of only 2-3%. Some of the early devices were Schottky barrier cells, but were quickly discarded in favour of p-i-n cells. Since the first report, there has been a remarkable increase in the efficiency of the cells, increasing by roughly 1 % conversion efficiency per year, to a present value of 14%, as is shown in Fig. 10.17. The increase has resulted from a variety of innovations in the design, materials, and structure of the cells. The electronic properties of the solar cell are described next and then these innovations are outlined more or less in the order in which they occurred. 

Physical incorporatiem of phthalocyanines and porphyrins in polymers was mentioned in Chap. 2.1.1 and 2.1.2. Moreover, photovoltaic properties of Schottky bavier solar cells were checked by dispersing metal free Pc in a polymer binder At peak solar power (135 mW/cm ) a power conversion efficiency of 1,2% has been obtained. 

Discovered in 1993, the photovoltaic performance of N3 has been unmatched for eight years by virtually hundreds of other complexes that have been synthesised and tested. However, in 2001 the black dye tri(cyanato)-2,2 2"-terpyridyl-4,4 4"-tricarboxylate)Ru(II) achieved 10.4% AM 1.5 solar-to-power conversion efficiency in full sunlight (Nazeeruddin et al, 2001). Conversion efficiencies have meanwhile been improved further, the current record validated by an accredited laboratory being 11.1% (Chiba et al, 2006). 

Discovery of amorphous silicon and its dopability has already had a tremendous impact on industrial applications of amorphous materials. Amorphous Si is now used fairly extensively as a photovoltaic material. In photovoltaic applications, solar photons excite the electrons across the gap and the resulting electron-hole pairs, are driven towards the respective electrodes in order to prevent their recombination. Electron is driven through an external resistance to generate the electrical power. The efficiency of conversion of solar energy to electrical power is characterized by an efficiency factor, r, which is given by. 

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