Chapter 5 pv systems april 11 2011

    A material or device that is capable of converting the energy contained in photons of light into an electrical voltage and current is said to be photovoltaic A photon with short enough wavelength and high enough energy can cause an electron in a photovoltaic material to break free of the atom that holds it If a nearby electric field is provided, those electrons can be swept toward a metallic contact where they can emerge as an electric current The driving force to power photovoltaics comes from the sun, and it is interesting to note that the surface of the earth receives something like 6000 times as much solar energy as our total energy demand   Spurred on by the emerging energy crises of the 1970s, the development work supported by the space program began to pay off back on the ground By the late 1980s, higher efficiencies (Fig 8.1) and lower costs (Fig 8.2) brought PVs closer to reality, and they began to find application in many offgrid terrestrial applications such as pocket calculators, off-shore buoys, highway lights, signs and emergency call boxes, rural water pumping, and small home systems • While the amortized cost of photovoltaic power did drop dramatically in the 1990s, a decade later it is still about double what it needs to be to compete without subsidies in more general situations Figure 8.1 Best laboratory PV cell efficiencies for various technologies (From National Center for Photovoltaics, www.nrel.gov/ncpv 2003 Figure 8.2 Possible evolution of turn-key PV system prices  By 2002, worldwide production of photovoltaics had approached 600 MW per year and was increasing by over 40% per year (by comparison, global wind power sales were 10 times greater) Figure 8.3 World production of photovoltaics is growing rapidly, but the U.S share of the market is decreasing Based on data from Maycock (2004) Critics of this decline point to the government’s lack of enthusiasm to fund PV R&D By comparison, Japan’s R&D budget is almost an order of magnitude greater       Before we can talk about solar power, we need to talk about the sun Need to know how much sunlight is available Can predict where the sun is at any time Insolation : incident solar radiation Want to determine the average daily insolation at a site Want to be able to chose effective locations and panel tilts of solar panels  The sun ◦ 1.4 million km in diameter ◦ 3.8 x 1020 MW of radiated electromagnetic energy  Blackbodies ◦ Both a perfect emitter and a perfect absorber ◦ Perfect emitter – radiates more energy per unit of surface area than a real object of the same temperature ◦ Perfect absorber – absorbs all radiation, none is reflected  Plank’s law – wavelengths emitted by a blackbody depend on temperature 3.74 108 E   14400     exp    1  T    (7.1) • λ = wavelength (μm) • Eλ = emissive power per unit area of blackbody (W/m2-μm) • T = absolute temperature (K) Visible light has a wavelength of between 0.4 and 0.7 μm, with ultraviolet values immediately shorter, and infrared immediately longer Source: en.wikipedia.org/wiki/Electromagnetic_radiation The earth as a blackbody Figure 7.1 Area under curve is the total radiant power emitted We can see: - Rural area: very high demand on solar photovoltaics, but because of high price poor people can not dream of getting it - Urban area: good electricity supply from the national grid But, if the price is good enough, solar photovoltaics can also attract the attention of the people living in the urban area to prevent unexpected power shortage (It is quite often in Vietnam, especially in the dry season) 571 - Currently, there is general macroscopic energy policy But, there are so far no concrete policies such as tax exemption and financial supports,… - Solar panels and corresponding parts are mainly imported There is nearly no industry referring to solar photovoltaics in Vietnam, except one factory named RED SUN in Long An – near Ho Chi Minh City 572  Price reduction: In-country fabrication by local and foreign investment Detailed policies focusing on tax exemption, or tax reduction, or financial supports … 573  Development strategy: Two steps: 1.To promote the application of solar photovoltaics in Vietnam, we should firstly set up the new projects, it means we should not wait for the personal demands paid by personal budgets The new projects must be totally different from the previous ones, which have been often funded by international or national organizations and have been installed mainly for demonstration purpose 574 The new projects should be invested by people who are intending to business in this field Under this point of view, the new projects should not be decentralized and should be connected to the grid… In order to set up the projects, it must be repeated that we need good financial policies, hopefully, which would be published in the first quarter of the next year 575 Following the success of the first step, the solar photovoltaics together with its low price can get the attention of the community After this step, hopefully personal budgets can be expended to buy solar panels 576 ―SOLAR ROOF should be considered as one of main strategic approaches parallel with the new projects (step 1) to promote photovoltaic application in Vietnam, especially at NEW URBAN AREAS‖ There is high potential to develop the notion SOLAR CITY at NEW URBAN AREAS 577 578  Nearly blank market and blank area in terms of solar photovoltaics are awaiting you 579   ―Vietnam Needs Investors To Promote Use Of Renewable Energy Technologies‖ ―The Government of Vietnam has been exploring more and more the possibilities for investment in the country as they recognize the toll that electricity shortages nationwide are causing‖ 580  ―The climate of Vietnam is conducive to positive impacts from solar energy use, and the sun is a priceless commodity in both summer and winter Research information shows that sunshine is available between 1,800 hours and 2,700 hours annually‖ 581  ―Experts agree that solar energy is a great way to fill off-grid electricity needs, especially in areas of a higher concentration of pollution where mini-grids are not a good idea‖ Sherry Irvin on behalf of the BascoTec Internet Limited Technologie Park 13 33100 Paderborn Germany 582   The draft of the decree on the means supporting the development of renewable energy has just been submitted to the government by the ministry of industry and commerce (Tuoi Tre daily newspaper, Sept 8, 2009) Main contents of the draft of the decree: - The government commits to exempt those who invest to develop the electric generation by renewable energy from taxes - The price of electricity produced by renewable energy would be discussed to guarantee the investor’s rational benefit 583  It’s time to invest and to business referring to solar photovoltaics in Vietnam 584 THANK YOU FOR YOUR ATTENTION 585 ... 15? ??  H     -3 h    45? ??  h  sin   cos 40cos 23.45cos   45? ??  sin 40sin 23. 45  0. 752 7   sin 1  0. 752 7   48.8  The sin of the azimuth angle is found from (7.9)  cos 23. 45? ??... rise and sun set   One revolution every 3 65. 25 days Distance of the earth from the sun   360( n  93)   d  1 .5 10 1  0.017sin   km (7 .5)  3 65       n = day number (Jan is day... 81)  99.89 364 364 E = 9.87sin  2B   7 .53 cos  B   1.5sin  B  =  3 .5   The local time meridian for Boston is 75? ?, so the difference is 75 ˚-71.7 ˚, and we know that each degree corresponds