Introduction to Solar Power

8/19/2019 Introduction to Solar Power

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Space Based Solar Power An odyssey from Concept to Reality

INTRODUCTION

Electricity is the most versatile and widely used form of energy.The global demand for electricity is continuously

growing. f the total generation worldwide! more than "# percentof energy is generated using coal$fired station resulting

in carbon dio%ide emission threatening the global warming. Tomitigate the conse&uence of the climate change! the

generation systems need to undergo significant changes. Theinstalled capacity over the last century is a clear picture of

growing economy. To satisfy the increasing demand for power andreducing C' emission! the future generation system

must meet the demand! reliability! efficiency and sustainability.This has accelerated the generation using solar! wind!

tidal! and many more. The ob(ective of such initiative is toinvestigate on the feasibility! financing and development of new

plans )*+. According to the ,-oad eneration Balance Report'#*/$'#*01 of 2ndia! the energy re&uirement

registered a growth of ".34 during the year '#*'$'#*/ against the pro(ected growth of 3.*4 )'+. This is due to increasing

population! advancement in living standard of the people!

discovery of new power consuming yet comfort providingdevices5appliances and improvement in the life style of the masses.The conventional methods for generating electrical

power are insufficient for providing the increasing demand ofelectrical power. Thus! there is an urgent need to

supplement the conventional sources. Solar power generation withits associated technologies has advanced few steps

ahead in last several decades. 2t has been believed and investigatedsince last four decades that solar energy in space free

from the weather conditions is &uite different from that on theearth. The SPS system has great potential to harness solar

power using bul6 photovoltaic 7P89 array in space and transmit itto the earth using microwave. The solar energy from

sun while travelling a path to Earth is lost in the atmosphere because of the effects of reflection and absorption.



Therefore! it would be much beneficial to absorb solar energy fromthe geosynchronous orbit. A geosynchronous orbit is

any orbit which has a period e&ual to the earth:s rotational period.Accounting for efficiency! the P8 cells produce 3 to *#

4 times more power at space than at ground )/+. Thus placingsolar cells in space has a competitive advantage over solar

power plants on the Earth. A photovoltaic cell can be placed onsatellite revolving in geosynchronous orbit to absorb the

solar energy. The satellite is called as solar powered satellite. Thegenerated ;C by the photovoltaic cell can be converted

into microwave by using magnetron! 6lystron or solid statedevices. The generated microwave is transferred to the earth

using antenna. The transmitted power is received by a devicecalled rectenna. The received power is converted into ;C

power by filters and schott6y diode. Power transmission usinglaser beam is also possible but! the power efficiency at both

the transmitter and receiver of microwave transmission is more ascompared with laser

<hat is Solar Energy=Every day! the sun radiates 7sends out9 an enormous amount of energy> called solar energy. 2t radiates more energy in one day than the world uses in

one year. This energy comes from within the sun itself. -i6e most stars! thesun is a big gas ball made up mostly of hydrogen and helium gas. The sunma6es energy in its inner core in a process called nuclear fusion. 2t ta6es thesun?s energy (ust a little over eight minutes to travel the @/ million miles toEarth. Solar energy travels at the speed of light! or *"!### miles per second!or /.# % *# meters per second. nly a small part of the visible radiantenergy 7light9 that the sun emits into space ever reaches the Earth! but that ismore than enough to supply all our energy needs. Every hour enough solarenergy reaches the Earth to supply our nation?s energy needs for a yearSolar energy is considered a renewable energy source due to this fact. Today!

people use solar energy to heat buildings and water and to generateelectricity. Solar energy accounts for a very small percentage of .S. energy

>less than one percent. Solar energy is mostly used by residences and to

generate electricity.

Why Solar Energy?While a majority of the world's current electricity supply is generatedfrom fossil fuels such as coal, oil and natural gas, these traditionalenergy sources face a number of challenges including rising prices,security concerns over dependence on imports from a limited number



of countries which have significant fossil fuel supplies, and growingenvironmental concerns over the climate change risks associatedwith power generation using fossil fuels. s a result of these andother challenges facing traditional energy sources, governments,businesses and consumers are increasingly supporting thedevelopment of alternative energy sources and new technologies for

electricity generation. !enewable energy sources such as solar,biomass, geothermal, hydroelectric and windpower generation haveemerged as potential alternatives which address some of theseconcerns. s opposed to fossil fuels, which draw on finite resourcesthat may eventually become too e"pensive to retrieve, renewableenergy sources are generally unlimited in availability.

Solar power generation has emerged as one of the most rapidlygrowing renewable sources of electricity. Solar power generation hasseveral advantages over other forms of electricity generation#

Reduced Dependence on Fossil Fuels. Solar energy productiondoes not re$uire fossil fuels and is therefore less dependent on this

limited and e"pensive natural resource. lthough there is variability inthe amount and timing of sunlight over the day, season and year, aproperly si%ed and configured system can be designed to be highlyreliable while providing long&term, fi"ed price electricity supply.

Environmental Advantages. Solar power production generateselectricity with a limited impact on the environment as compared toother forms of electricity production.

Matching Peak Time Output with Peak Time Demand. Solarenergy can effectively supplement electricity supply from an electricitytransmission grid, such as when electricity demand peaks in thesummer

Modularity and Scalaility. s the si%e and generating capacity of a solar system are a function of the number of solar modulesinstalled, applications of solar technology are readily scalable andversatile.

Fle!ile "ocations. Solar power production facilities can beinstalled at the customer site which reduces re$uired investments inproduction and transportation infrastructure.

#overnment $ncentives. growing number of countries haveestablished incentive programs for the development of solar andother renewable energy sources, such as i( net metering laws thatallow on&grid end users to sell electricity back to the grid at retailprices, ii( direct subsidies to end users to offset costs of photovoltaice$uipment and installation charges, iii( low interest loans forfinancing solar power systems and ta" incentives) andiv( government standards that mandate minimum usage levels ofrenewable energy sources.

*espite the cost, an advantage of photovoltaic systems is that theycan be used in remote areas. nywhere a diesel generator is thetechnology of choice, many times a photovoltaic system is a much



better life&cycle cost option.

Stand&alone photovoltaic systems produce power independently ofthe utility grid. +n some off&the&grid locations even one half kilometerfrom power lines, stand&alone photovoltaic systems can be morecost&effective than e"tending power lines. hey are especially

appropriate for remote, environmentally sensitive areas, such asnational parks, cabins, and remote homes.

he solar power market has grown significantly in the past decade. ccording to Solarbu%%, the global solar power market, as measuredby annual solar power system installations, increased from -/ 0Win 11 to 2,/-- 0W in 113, representing a 45! of -.6, whilesolar power industry revenues grew to appro"imately 7S821.3 billionin 113. *espite the rapid growth, solar energy constitutes only asmall fraction of the world's energy output and therefore may havesignificant growth potential. Solarbu%% projects in one of its forecaststhat annual solar power industry revenue could reach 7S892.: billionby 122.

Concept of Space Based SolarPower.he concept of S;S< was theori%ed over -1 years ago by renownedscientist *r. <eter 5laser. Since then, in response to periodic energycrises, the idea has been re&evaluated from time to time by the 7.S.*epartment of Energy, =S, major aerospace companies andcountries such as >apan and +ndia. heir studies generally concludedthat there is no technical barrier to implementing S;S<) rather, theprincipal impediment has been economics && the ability to provideS;S< at a cost that is competitive with other energy sources.Solar power satellites are large arrays of photovoltaic panels

assembled in orbit, which use very low power radio waves to transmitsolar power to large receiving antennas on Earth. he resulting power can either supplement, or be a substitute for, conventional electricitysources. Several of the technologies re$uired to build a workingS;S< satellite have, in principle, already been developed&&&and someof the component technology is already in use across a variety ofsectors.

he advantage of placing solar collectors in geosynchronous Earthorbit 5E(, about 93,111 kilometers above Earth, is that it uses theconstant and unobstructed output of the Sun, unaffected by theEarth's day@night cycle.

;y contrast, ground&based solar power provides a vital and valuableaddition to the Earth's energy needs, but is limited by these factors#

A Weather

A Bariable seasons

A tmospheric blocking of sunlight

A <oor direct sunlight at higher and lower latitudes



A E"pensive and limited storage capacity;ecause none of these factors applies to S;S<, an S;S< cell canprovide an estimated 3&C times more power than a comparable solarcell on the Earth's surface.

long&range wireless power transmission test was conducted in mid&11C, successfully transmitting a microwave beam similar to the kindthat would be used to transmit energy from space to Earth( betweentwo Dawaiian +slands across 2-C kilometers&&&more than the distancefrom the surface of the Earth to the boundary of space. his testdemonstrated the technical feasibility of transmitting S;S< to Earth.

he fre$uency of radio waves sent down from an S;S< satellitewould be comparable to cell phone, wireless +nternet, or cordlessphone signals. ;ased on several studies done by =S, thistransmission is safe to human, animal, and plant life near thereceiving antennas&&&large structures designed to convert the radiowaves into usable electricity.

hese antennas would be placed in areas with limited access tomainline grid power, giving rural and developing areas a much&needed power alternative. hey might also be placed close to mainpower grids to provide a substantial amount of grid power.

!ecently, as efficiencies of solar cells and other core systems haveincreased, and the price of and demand for( energy has risen, S;S<has become more commercially viable. actors that have contributedto this development include#

A Efficiency and mass of photovoltaic cells becoming moreefficient and lighter, as well as cheaper(

A Wholesale electricity cost increasesA *emand for electricity increasing rapidly(

A he availability and cost of commercial space lift transportationbecoming cheaper, faster, and more reliable, with billions ofdevelopment dollars now being invested(

A he identification of additional, easily accessible revenuestreams for S;S<

With these new efficiencies and price points, the cost of a viableS;S< solution is substantially lower than just a few years ago.

One of the major hurdles holding solar power back is theinherent intermittency issues that come with having anatmosphere over your head. Solar cells on the Earthssurface can only generate electricity when the sun is in thesky! and for many countries! especially those in the "orthernhemisphere! constant cloud cover can put a damper on asolar economy. But what if you could bypass the atmospherealtogether! what if you could harness solar energy directly



from the sun! in space. #n $%&$ science 'ction writer #ssac(ssimov spoke of space stations that could transport energygathered from the sun to various planets with the microwavebeams in his short story )*eason.) +oday! science 'ctioncould become science fact within the ne,t -uarter of a

century! at least according to r. Susumu Sasaki of the /apan(erospace E,ploration (gency 0/(1(2. #n (pril of 34$& /(1(released a proposal for a series of ground and orbitale,periments that could lead to the development of afunctioning space based solar power system by the 3454s.

History of Space Based SolarPower

+he idea of collecting solar power in space is nothing new. #t

did not take long after the invention of the 'rst silicon6basedsolar cells and the advent of space e,ploration for someoneto reali7e that the two technologies would make a happymarriage. (merican aerospace engineer Peter 8laser pennedthe 'rst formal proposal for a space based solar powersystem in $%9:! just a year shy of "eil (rmstrongs strollacross the moon. ;e was granted patent number 5!<:$!9&<for a satellite solar6power system 0SSPS2 in $%<5 for amethod of transporting solar power over long distances bybeaming microwaves from an antenna in space onto a muchlarger one on the ground. +he ground receiver would later be

called a rectenna. 8laser! who was vice president of (rthur. =ittle! #nc. landed a contract with "(S( to lead a morecomprehensive study in $%<&. +he initial report was enoughto make "(S( fund research and development into theproject during the <4s and :4s. ( change in administrationswould ultimately put a hiatus on further development of theidea. +he O>ce of +echnology (ssessment concluded thatthere were too many unknowns regarding the technical andeconomic aspects of a space based solar power system.

"(S( would not take another serious look at Space BasedSolar Power until $%%%! with its Space Solar PowerE,ploratory *esearch and +echnology 0SE*+2 program. +heylaid some of the groundwork for solar power satellite 0SPS2concept! using a geosynchronous orbit! and establishedgeneral feasibility and design re-uirements. +heir SPSconcept entailed a gigawatt space power system within?atable photovoltaic gossamer structure! which utili7essolar heat engines to generate electricity. ( key lesson thatcame out of this study was that launch costs for low earth



orbit would have to fall to the @$44 6 344 AS per kilogramrange for the construction of an SPS to become feasible. astforward to ay! 34$& and /(1( is picking up where they leftoD.

The Goal

Every roadmap needs a destination! and for space basedsolar power! /(1( has proposed a commercially viable $gigawatt space based solar power system.

+he system would consist of a geosynchronous orbitingsatellite out'tted with state of the art silicon based solarcells. Orbital mirrors ensure that sunlight is always

concentrated onto the satellites solar panels as it orbits withthe Earths rotation! even when it resides on the side of Earthopposite the sun. On the surface a 5 kilometer long man6made island out'tted with billion miniature rectifyingantennas receives the microwaves beamed down from asatellite 59!444 kilometers above! converting them back intoC current. (n on6island substation routes electricity throughan undersea cable directly to +okyos bustling electrical grid.(n ambitious project! r. Sasaki highlights si, areas ofdevelopmentF wireless power transmission! spacetransportation! space construction! satellite control! power

generation and power management.

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Introduction to Solar Power