Renewable energy sources


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The paper gives an in depth view onrenewable energy sources: Hydroelectric, Wind, Solar, Biomasses

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Renewable energy sources

  1. 1. THE RENEWABLE ENERGY SOURCES Hydroelectric Wind Solar BiomassesRenewable energy sources are called such way as they’re able to regenerate themselves over arelatively short period of time. The main renewables are: solar energy (photovoltaic and thermal),wind energy, hydroelectric energy, geothermal energy, energy derived from biomasses and energygenerated by the motion of sea waves and tides.HYDROELECTRIC ENERGYFor the most part, it is obtained by channeling water into special pipes (penstocks) and dropping itfrom a sufficient height to turn turbines that generate electric power. Depending on the height ofthe drop and the flow rate, different types of turbines can be used to generate electric power.In Italy, the largest hydroelectric power plants were built in the first half of the 20th Century. Thesefacilities, which are still in operation today, are for all intents and purposes the equivalent of anenergy gold mine. Moreover, Edison’s oldest power plants are truly outstanding examples ofindustrial architecture. Today, the growth potential of the hydroelectric segment can be realized byexploiting small/medium-height river drops to power so-called mini-hydro systems. 1
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  3. 3. WIND ENERGYWind energy is contained in the wind’s kinetic energy. It is one of the sources that are attracting themost attention from energy producers, who are making large capital investments in this areathroughout the world.The wind machine is one of the oldest systems for the production of mechanical energy.Following the oil crisis of the 1970s, research of alternative technologies based on renewablesources enjoyed considerable development.Today, wind powered generation is considered one of the most promising green technologies.However, costs continue to be higher than those of fossil-fuel power plants. The cost of respectingthe environment continues to rise, even when the “fuel” is free.Exploiting the wind is not easy: unpredictability of the weather, variability from location to location,variability in intensity, connections with the power grid and noise have been thus far the mainissues in the design of new wind farms.The power that may be derived from an aerogenerator depends on the sweep of the blades. Thebigger the radius of the blades, the more power will be available. Power also depends on the cubeof wind speed, which makes knowledge of anemological conditions at the site where anaerogenerator is to be installed essential.General Configuration of an AerogeneratorThe blades are installed on a hub to form a rotor. The hub is connected to a shaft (the slower shaft)that rotates at the same speed as the rotor. Through a gearbox, which is not always present insome recent aerogenerator models, the slow shaft is connected to a fast shaft equipped with asafety and control brake, downstream of which an electric generator is installed. Thesecomponents are usually placed inside a housing called a nacelle, which is positioned on a yaw ringand can thus be easily oriented according to the wind’s direction.The control system of a wind machine can perform different functions (at the design stage,builders decide which systems to implement, based on the budgeted cost target): • Pitch regulation, • Stall regulation, • Yaw control. 3
  4. 4. Hub with blade pitch Rotor brake actutator Gear box Generator Control system Nacelle Yaw system Rotor Support tower Transformer boxPitch regulation is implemented by rotating the blades on their main axis to increase or reduce thearea exposed to the wind, depending on the wind’s velocity. It is thus possible to optimize theangle of attack at any wind velocity and cut wind velocity at startup. With high wind velocity, thepitch angle is changed to reduce the attack angle and, consequently, reduce stress on the blades.This regulation system thus makes it possible to maintain a constant power output even with highwind velocity.Stall regulation can be achieved, during the design phase, by selecting an appropriateaerodynamic profile for the blades.The purpose of the yaw control system is to orient the nacelle and, thus, the entire rotor assembly,depending on the wind’s direction. When appropriately programmed, it can also be used to controlpower output.The first two of the abovementioned systems are most commonly used in aerogenerators. Whilethe pitch regulation system is the most effective, the stall regulation system is less expensive.In Italy, the best locations are in Sardinia and the southernmost part of Southern Italy. It isimportant that these facilities are appropriately sited, to minimize their impact on local ecosystemsand native fauna. 4
  5. 5. EDISON’S WIND FARMS Number of Power of MW Year when aerogenerators aerogenerators installed commissioned MWEMILIA ROMAGNASan Benedetto Val di Sambro 10 0.35 3.50 1999(BO) - Monte del GallettolocationTUSCANYMontemignaio (AR) 3 0.60 1.80 2001ABRUZZOCastiglione Messer Marino 44 0.60 26.40 2001(CH)Castiglione Messer Marino 24 0.66 15.84 2004Expansion (CH)Fraine (CH) 15 0.60 9.00 2002Monteferrante (CH) 41 0.60 24.60 2001Montazzoli (CH) 16 0.60 9.60 2001Roccaspinalveti (CH) 23 0.60 13.80 2001Roio del Sangro (CH) 10 0.60 6.00 2001Schiavi d’Abruzzo (CH) 15 0.60 9.00 2002MOLISERipabottoni (CB) 24 0.66 15.84 2005Lucito (CB) 17 2.00 34.00 2008 CAMPANIACastelnuovo di Conza (SA) 8 0.60 4.80 (*) 2000Castelnuovo Conza (SA) 6 1.67 10.02 2007Foiano (BN) - Monte Barbato 11 0.60 6.60 2001and Toppo Grosso locationsFoiano (BN) - Piano del 16 0.60 9.60 2001Casino locationSan Giorgio la Molara (BN) – 20 0.50 10.00 1999Polero locationAPULIACastelnuovo della Daunia 10 0.25 and 0.35 2.60 1995(FG) - Casone RomanolocationCelle San Vito 1 (FG) - La 9 0.35 3.15 1999Montagna location.Celle San Vito 2 (FG) 7 0.60 4.20 2001Faeto (FG) 44 0.60 26.40 2002 5
  6. 6. Orsara la Montagna (FG) 30 0.60 18.00 2001Rocchetta S. Antonio (FG) 15 0.35 5.25 2000Volturara Appula anf Motta 19 0.60 11.40 2001Montecorvino (FG)Volturino (FG) 20 0.66 and 0.60 13.08 2004BASILICATAVaglio di Basilicata (PZ) 20 0.60 12.00 2003CALABRIAMelissa (KR), Strongoli (KR) 25 2.00 50.0 2009Parco Eolico San 13 2.00 26.00 UnderFrancesco constructionSICILYMistretta (ME) 15 2.00 30.00 2010(*): 50% with PE CastelnuovoSOLAR ENERGYSolar energy is the energy produced by solar radiation. It can be divided into two mainclassifications: Thermal solar energy, which involves producing heat by exposing to sunlight piping systems where water reaches a high temperature and is then used heat homes or produce electric power. Photovoltaic solar energy, which involves the use of special photovoltaic panels to transform the sun’s energy into electric power.Photovoltaic technology makes it possible to transform the sun’s rays into a continuous electriccurrent without using any moving parts.After finding widespread applications to produce electric power on satellites, it now seems to havereached a turning point, becoming suitable for installation in homes or industrial facilities or atlarge-scale power plants, thanks to improved conversion efficiency, lower costs and modulardesign. Undoubtedly, photovoltaic technology’s immediate application is in distributed powergeneration.Technology DescriptionPhotovoltaic cells, which are the building blocks of solar energy conversion systems, are made ofsemiconducting materials. Semiconductors allow the concurrent occurrence of two processes: theabsorption of light and the separation of the electrical charges created by the excitement of theelectrons reached by the light radiation. The semiconducting material must be extremely pure andfree of defects, and, consequently, expensive, in order to avoid that a portion of these free chargesrecombine (i.e., return to their original state). 6
  7. 7. The solar-to-power conversion efficiency of photovoltaic modules currently commercially availableis 14%-15% for crystalline silicon panels and reaches 19% for monocrystalline silicon systems.Thin-film modules, which have an efficiency of up to 11%, are made with materials that can mimicthe behavior of semiconductors (e.g., cadmium telluride – CdTe, or copper indium gallium(di)selenide – CIGS).Because solar cells produce a continuous electric current, the overall conversion efficiency isreduced by a few percentage points due to the use of power electronics (inverter, powerconditioning and maximum power point tracker) for conversion to alternate current. polysilicon ingots wafers photovoltaic photovoltaic cell moduleEDISON’S SOLAR PLANTS1. ALTOMONTEAltomonte (Italy) Solar FacilityIn 2009, Edison made its debut in the Italian photovoltaic market, completing construction of afacility with a peak capacity of 3.3 MW and panels covering a surface area of more than one millionsquare feet. Located in Altomonte, this facility is adjacent to a combined-cycle power plant firedwith natural gas. The system is comprised of about 16,500 crystalline silicone panels for anaverage production of 4.4 GWh a year. This facility will help save about 2,000 tons of CO2emissions a year.2. EDISON’S HEADQUARTERSSolar Facility at Edison’s Milan Headquarters 7
  8. 8. In addition, a photovoltaic unit installed on the roof of Edison’s Foro Buonaparte headquarters, inMilan, was commissioned in January 2009. This system, which has a capacity of 20 kW, wasdesigned using the most modern technologies available. Its crystal silicone panels deliver anefficiency of 17%. This facility will help save about 10.3 tons of CO2 emissions a year.ENERGY FROM BIOMASSESThis type of energy is obtained by the combustion of various types of organic materials that areused as fuel either directly or after treatment.These materials consist mainly of logging waste, industrial scrap, solid urban waste, effluents formlivestock farms and certain vegetable species that are farmed for energy production purposes(mainly sugar cane, beets, corn, soy, poplar, etc.).Biomasses can be used in different systems, including, by way of example, the following: small home systems for the production of thermal energy (system widely used in the mountain regions with mini-boilers); large facilities for the production of electric power using internal combustion engines, originally designed for marine applications, that are fueled with liquid vegetable oil; larger facilities that use solid biomasses (e.g., wood chips) to produce both electric power and heat and serve multiple users and/or district heating systems; farming operations that generate effluents from livestock breeding and use them to produce biogas from anaerobic fermentation suitable for electric power generation; automobiles (with biofuel used as a percentage of conventional fuel). 8