Solar Power and Photovoltaics

Solar Energy—Complete Guide to Solar Power and Photovoltaics, Practical Information on Heating, Lighting, and Concentrating—U.S. Department of Energy. 

Wind, solar thermal, and photovoltaic power together accounted in 1998 for only about 1% of U.S. electricity generation from renewable sources and only about 0.1% ofall electricity (DOE/EIA 1999a). 

A different approach is to reconsider the airship as a means of air travel. A first approach to this is considering an airship for high-altitude cruising (or as a stratospheric platform) powered by photovoltaic panels and using a reversible fuel cell system to store surplus solar power and use it when the sim is not visible. In this way, carrying possibly heavy batteries may be avoided. The envisaged relative shares of direct use of solar power, of elec-trolyser operation and of fuel cell power production are shown in Fig. 4.12. So far, testing of the equipment sketched in Fig. 4.12 has been performed on a 1-kW scale in the laboratory and in simulated airship conditions. 

The assumed conditions used in evaluating characteristics of the systems are summarized in Table 2. The total areas of the solar collectors and photovoltaic arrays are assumed to be 10 ha. In the solar thermal and hybrid systems, the type of collector is parabolic trough, the condenser outlet pressure 0.1 kg/cm a, and the capacity (maximum net power output) has been determined so as to minimize the unit cost of generated power energy. In the solar photovaltaic system, the conversion efficiency at the array is assumed to be 15 %. The tracking scheme of the solar collector and photovoltaic array is single north-south axis. 

Capital cost is the major contributor to the cost of solar power. With photovoltaic power systems presently costing about 4 per peak watt, the capital cost of 4000/kW would be equivalent to 8888/kW at 100% capacity, equating to 9 cents/kWh when amortized over 30 years (at 8% interest rate). Obviously, this is well above the nuclear capital cost of nominally 4200/kW with a 90% capacity factor (equivalent to 4667/kW at 100% capacity factor), and an amortized cost of 4.7 cents/kWh. 

A photovoltaic (PV) solar power system is a complete electrical source that uses solar cells to directly convert light energy into electricity. The system can be self-contained and completely autonomous or it can work in tandem with other conventional fuel-based sources of power to offer robust power availabihty. 

Perhaps the most familiar example in the specialty items category is the consumer electronics market which consists primarily of solar-powered calculators and watches. Although volumes are large in terms of units sold, the revenues are relatively small. Further, the competition is fierce for any photovoltaics manufacturer who seeks to sell commodity solar cells to the consumer goods producer. 

The extent to which each technology is poised to advance is described in separate discussions of photovoltaics, solar-thermal power, and wind, biomass, waste-to-energy, geothermal, hydropower, and wave energy. 

Solar Power With improved technology and production methods considerable use is being made of solar power in remote locations. The output of photovoltaic arrays is used to maintain conventional storage batteries in a state of charge. The cathodic protection system is in turn energised from the batteries. It is usual to incorporate sufficient battery storage to accommodate a number of no-sun days. Whilst in theory the capacity of equipment is unlimited, a practical maximum would be ca. SOO W. 

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 price of photovoltaics continues to drop and interest is continues to grow. States such as New York, Arizona, Florida and Washington have joined California in a major effort to allow homes and businesses to use solar power. 

Prices for electricity fluctuate depending on the time of day. England has electricity costs of 22 cents per kilowatt hour and is further north than most inhabited parts of Canada and receives limited solar radiation over much of the year. This makes conventional solar power not very competitive at grid delivered costs. However, kilowatt hour photovoltaic costs have been in an exponential decline for decades, with a 20-fold decrease from 1975 to 2001. 

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