07 chapter 04 renewable energy options
TRANSCRIPT
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Renewable energy reers to energy that is derived rom sources that are essentially inexhaustible or
rom natural resources such as wind, sunlight, rain, tides and geothermal heat, which are renewable (naturally
replenished), produce ew hazardous emissions or pollutants, and have minimal impact on ecosystems.
Renewable eneRgyOptiOns fOR DOmestic Use
by Riaan Meyer and Graham Gariseb, Centre for Renewable and SustainableEnergy Studies, Stellenbosch University
DefinitiOn Of Renewable
eneRgy
Weve embarked on the beginning o the last days o the age o oil. Embrace the uture and recognize
the growing demand or a wide range o uels or ignore reality and slowlybut surelybe let behind.
Mike Bowlin, chairman and CEO o ARCO (now BP)
chapteR 4
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eneRgy pOlicies
In the apartheid era, energy policy was driven by a need to be sel-sucient, which resulted in a national
dependence on coal the countrys main energy reserve. South Arica continues to be dependent on coal. The
energy sector is dominated by a ew large players and poor communities have inadequate access to aordable
and sae uels. Current policy represents a shit in direction towards improving access to energy, particularly or
previously disadvantaged communities, although sustainability has yet to emerge as a key priority.
Energy White Paper o 1998The aims o this paper are to:
Increaseaccesstoaffordableenergyservices;
Improveenergygovernanceandrestructuregovernmentassets;
Manageenergy-relatedenvironmentalimpacts;
Securesupplythroughdiversityandopenmarkets;
StimulateeconomicdevelopmentcreateSMMEsandexportopportunities;
Assistpreviouslydisadvantagedpeopletogainentrytotheenergysector;
Allowunrestrictedmarketaccesstotheliquidfuelsmarket;
MunicipalSystemsActNo32of2000Section23oftheActrequiresthatmunicipalities:
Produce integrateddevelopmentplansforthemedium-termdevelopmentof theirmunicipalareasto
meettheneedsoftheircommunities;
Providesustainableservicestotheircommunities;
Promoteincreasedcommunityinvolvementintheprovisionofenergyservices.
White Paper on Renewable Energy & Clean Energy Development
(Draft2002)Though this paper does not provide guidance on the use o renewable energy applications, it does provide
the ollowing:
Thispapersetsa10yeartargetof10,000GWh/annumrenewableenergyproductionforSouthAfrica
Thispaperacknowledgestheimportantroleofrenewableenergyinthelong-termenergyplanningand
applications in South Arica
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NationalEnergyRegulatorActof2004ThoughthisActgivesNERSA(NationalEnergyRegulatorofSouthAfrica)themandatetoregulatetheliquid
uel markets in South Arica, to prevent monopolistic control and to promote private sector activities and
participation in the energy sector, little has been achieved in this regard.
PetroleumProductsAmendmentAct2003,Act58of2003This Act was promulgated to:
Promoteefcientmanufacturing,wholesalingandretailinginthepetroleumindustry;
Facilitateanenvironmentconducivetoefcientandcommerciallyjustiableinvestment;
Promotetheadvancementofhistoricallydisadvantagedindividuals;
Createemploymentopportunitiesandsmallbusinessesinthepetroleumsector.
GasActof2001Thegasactof2001providesaregulatoryframeworkforthestorage,transmission,distributionandtrading
o gas, it establishes a gas regulator and promotes access to transmission by third parties.
Manyprovincesandmunicipalitiesaresettingtargetsandgoalsinordertoachieveenergyandelectricity
reduction targets and renewable energy goals. This chapter will also unpack the various techonological
options available, particularly those which can be applied on a neighbourhood level.
technilOgical sOlUtiOns
Solar water heaters
A solar water heater is a device that utilises heat energy rom the sun to heat up water or domestic use.
The picture below shows a fat plate solar water heater. Heat rom the sun is collected in the fat plate solar
panel. The panel consists o copper tubes and aluminium ns that are painted black. The warm water that is
producedisstoredinastoragetankdirectlyabovethecollectorpanel.Mostsolarwaterheatersystemshave
an electric element as backup to allow or water heating during overcast days. Various types and models o
solar water heaters are available on the market. Apart rom the fat plate collector, evacuated tube collectors
are also a popular choice especially in coastal areas, as they are better suited or locations that have a higher
number o overcast days. Currently all evacuated tube collectors are imported, which explains why the locally
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manuactured fat plate collectors are dominating the South Arican market at present. Prices or solar water
heatersrangebetweenapproximatelyR3000fora55LsystemtoaroundR21000fora300Lsystem1.
1 A list eaturing dierent types o solar water heaters that have been tested by SABS, including prices, is listed on the Eskoms website: www.eskomdsm.co.za/sites/
deault/fles/u1/Accredited_participating_suppliers_list.pd
Flat plate solar water
heater, Lynedoch
Eco Village outside
Stellenbosch
Photo: Riaan Meyer
case stUDy
Solar Water Heaters or Kwanokuthula
Solar water heaters are not only or the high and middle income sector, but can also be a viable solution
forthelowincomesector.InApril2008,184solarwaterheaterswereinstalledinKwanokuthula,alow
income area on the outskirts o Riversdale in the Western Cape.
Solar Water Heater installed in Kwanokuthula, Riversdale (Photo: Graham Gariseb)
AtlanticSolarsystemswereinstalled;eachunitcomprisedan80Ltankanda1.5matplatecollector
panel. The systems were installed without any electric backup, but gave owners the option to add an
electricbackupelementatanadditionalcostofaroundR200.Theperunitcostofthesystemswas
R7000each,andincludedinstallation,pipingandahotwatertapinsideeachhousingunit.Solar
waterheaterscancostaslittleasR300forsimplesystems.
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A wind turbine is a device that rst converts the kinetic energy o wind into mechanical energy, and then
rom mechanical energy to electrical energy. Small horizontal axis, domestic size wind turbines are available
invarioussizesrangingfrom500Wto5000W,andhaverotordiametersrangingbetween1.5mto3m.The
picturebelowshowsa1000Whorizontalaxiswindturbine.Ithasarotordiameterofabout1.5mandisused
to power a stand-alone Trunz water lter at the Sustainability Institute near Stellenbosch.
small winD tURbines
Small 1kW wind turbine
and Trunz water flter at the
Sustainability Institute nearStellenbosch
Photo: Graham Gariseb
Thepoweroutputfromawindturbineistypicallyprovidedataratedwindspeedof12meter/second(m/s).
Mostsmallwindturbineshaveacut-inwindspeedaround2.5m/sto3.5m/s.
The electric output rom a wind turbine does not increase linearly with wind speed, it increases exponentially.
Inotherwords,awindturbinethatproduces1,000Wataratedspeedof12m/s,doesnotprovidehalfthe
ratedelectricpower(600W)athalftheratedwindspeed(6m/s);theoutputathalfthewindspeedwouldbe
lessthanhalftheratedpower,andforthecasementionedaboveitispredictedtobearound200to300W.
Small wind turbines can only produce electricity when the wind blows and batteries are used to store
electricity or later use.
In addition to the common horizontal axis turbines, vertical axis turbines are also available. The key advantage
o this type o arrangement is that the wind turbine does not have to be pointed in the wind direction to beeffective.Verticalaxiswindturbineshavelowerstartupspeeds,typicallyintheorderof1to2.8m/s.
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winD speeD cOnveRsiOn table
Speed in meter/second [m/s] Speed in kilometer/hour [km/h] Comment
1 3.6 Typical cut-in speed or vertical axisturbine
3.5 12.6Typical cut-in speed or horizontal axis
turbine
6 21.6 Hal the typical rated wind speed
12 43.2Typical rated wind speed or small wind
turbines
Localsmallwindturbinesupplier
Kestrel is a South Arican manuacturer o small wind turbines and located in Port Elizabeth. They
produce fourhorizontal axis turbine of600W,800W,1,000W and 3,000W electricaloutput. The
costofa1,000WturbineisaroundR31000,includingtheturbineandcontrollerbox.Acomplete
installationincludingtheturbine,polefortheturbine,batteries,cables,4kWinverterandinstallation
costsaroundR105000.
Omnicon an installation company, have done various installations o this type on arms that have no
Eskom power. They recommend that solar PV panels are installed to supplement the wind power
generation.
picO hyDRO systems
Pico hydro systems utilise fowing water rom a river or stream to generate electricity. Below is an
exampleofa1000WsysteminstalledatafarmnearCeres.TheinstallationofPicohydrosystemsisvery
sitespecic.Theadvantageofasuccessfulinstallationisthatitgenerateselectricity24hoursperdayand
battery storage is optional.
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Pico hydro installation,
Nollie se Kloo, Ceres
district
(Photo: Riaan Meyer)
Picohydrosystemsareavailableinsystemsassmallas200W.TypicallypricesforthePicohydroturbine
andgeneratorrangebetweenR4500(200Wsystem)andR14000(1kWsystem).SomePicoturbinesare
low-headturbinesandonlyrequireaverticalwaterheadof1.8m.A300Wlow-head(1.8m)systemwould
requireawaterowrateof40litres/secondandcostsaroundR5500.
batteRy stORage
Due to the intermittence o renewable electricity generation, batteries are required to store the
generatedenergy.Thebatteryvoltagetypicallyrangesfrom12V-similartoacarbattery-upto48V,at12V
increments. A charge controller and dump load are used as an interace between the renewable energy
source and the batteries. This controls the charging o the batteries and dissipated excess energy in the
dump load. An inverter is typically installed to convert the battery output which is in DC (direct current) into
220VAC(alternatingcurrent)allowingittobeusedinhouseholds.
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case stUDy
NollieseKloof
A armer in the Ceres district constructed a guest house in the mountains near a river. He obtained a
quote rom Eskom to extend the existing electric inrastructure to his new guest house and compared
this cost with installing a renewable energy system. Ultimately, the armer installed a hybrid system
consisting o a small wind turbine, solar PV panels, a Pico hydro turbine as well as the necessary
battery and inverter systems.
The 1kW wind turbine was erected in close proximity o the guest house. The area is shaded due
toamountaindirectlynorthoftheguesthouse.Dueto theshade, the720WsolarPVarraywas
erectedabout120mawayfromtheguesthouse,allowingmoredirectsunlighttothePVpanels.A
river fows past the guest house. Upstream o the guest house a small portion o the river is diverted
intoa100mmpipe,andisdirectedtoalocationclosetotheguesthousewherea1000WPicohydro
turbineisinstalled.Thewaterisreturnedtotheriver.Thenetheadavailableattheturbineis26mand
thewaterowratecanbecontrolledthroughamanualvalve.At6.8litres/secondtheoutputfrom
theturbineis360W.Ifthewaterowrateisincreasedtheturbinecandeliveruptoitsratedoutputof
1,000W.
A36Vbatterybankconsistingof18cellsof2Veachisinstalled.Thebatteriesstoretheelectricity
generatedbythevarioussources,andhaveacapacityof27kWhintotal.Alocallymanufactured
inverter,ratedat6kW,convertsthe36VDCfromthebatteriesto220VACwhichisusedintheguest
house. The picture below shows the batteries (bottom), inverter (bottom let corner), dump load (grey
box top right) and other equipment.
Battery backup system and auxilary equipment at Nollie se Kloo
Photo: Riaan Meyer
The system is sucient to supply the guest house (which sleeps 16 people) with the ollowing electric
equipment:electrickettle,fridge,freezer,microwave,TV,HiFiandvariouslights.Waterheatingand
cookingaredonewithbottledgas.ThetotalsysteminitialcostwasR121600,includinginstallation,in
2005.ContactNollieseKloofontelephone/fax:0233121982ortelephone:0233121407formore
inormation.
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sOlaR Ovens anD cOOkeRs
In locations with an abundance o sunlight, solar ovens and solar cookers can be utilised. The gure
belowshowsasolaroven,theSunstove2000,producedinSouthAfrica.Foodisplacedinblackpotsinside
the cooker and the solar oven is placed outside, acing the sun. The ovens can cook most types o ood that
can be prepared on an open re or electric stove, including stews, mielie-pap and bread.
Cooking times with solar ovens are considerably longer compared to conventional cooking but the advantages
o a solar cooker are:
Itneedslittleattentionwhilecooking,leavingthecookfreetoattendtoothermatters
Theriskofbeingburned,especiallychildren,isalmostentirelyeliminated
Nohazardousgassesarereleased
Two dierent
models o the Sunstove 2000
Photo: www.sungravity.com
Solar ovens and cookers are available in all shapes and sizes. They can be classied as either solar ovens
or solar cookers:
Asolarovenisaninsulatedboxwithlimitedreectivesurface.Itproducesrelativelowtemperaturesand
onlyneedstobeadjustedevery3to4hours
Asolarcookerischaracterisedbyhavingalargereectivesurfacefocussingthesolarenergyonapotto
produce a relative high temperature. They must track the sun on a continuous basis
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Localsolarcookermanufacturers
Sunstove2000
The Sunstove is manuactured rom moulded plastic (a portion is rom recycled material), scrap
aluminium plate refectors, o-cut glass-bre insulation and has a durable poly-carbonate lid. The
SunstoveretailsbetweenR300-R490.Seecontactschapterfordetails.
Lazola
TheLazolaisasolarcookerismanufacturedinCalitzdorpbyElnatan.Thisstoveismanufactured
rom stainless steel, has a double glass lid and can reach relatively high temperature. It retails around
R2900.Thisisanewprojectwithmoremodelstofollow.Seecontactschapterfordetails.
biOgas DigesteRs fOR the
pRODUctiOn Of gas fOR cOOking
A biogas digestermanuactures biogas rom organic waste materials e.g. sewage and animal
dung. The gure below presents a biogas digester during the construction phase. Biogas is generated
when bacteria degrades biological material in the absence o oxygen. The process is known as anaerobic
digestion. Biogas mainly consists o methane (CH4) and carbon dioxide (CO2)whichmakeup2/3and1/3
respectively o the gas produced. In small scale biogas digesters, the gas can be used directly or (mainly)
cooking.Typically1mofuncurbedbiogaswillprovide2hoursofcooking.2.5mofuncurbedbiogasis
equivalentto1kgofLPgas.
Biodigester during construction
Photo: Agama Energy
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case stUDy
StanfordValleyFarmandConferenceCentre
TheStanfordValleyFarmandConferenceCentreislocated10kmoutsideStanfordintheWestern
Cape. A13mbiogasdigesterwas installed byAgamaEnergy inSeptember 2006.Thebiogas
digesterisfedby30toiletconnections,restaurantfoodwasteandanimalmanure.Duringtheprocess,
liquid efuent overfows into the horizontal planted gravel lter, which overfows into a UV polishing
pound, where it is aerobically treated beore being recycled or irrigation. The energy generated by the
biogas digester is used or cooking purposes in the restaurant.
geOtheRmal heating/cOOling
systems
Earth tubes (cooling or heating tubes) utilise the earths near constant subterranean temperature to
warm or cool a building. These systems are also known as ground-coupled heat exchangers. Air can be
moved through these tubes by utilising a an (in an active system) or the air can fow with natural convection
in a passively designed system. Water can also be used as energy carrier instead o air mainly in active
closed-loop systems.
Mostairsystemsareconstructedfroma100mmto600mmdiameter,smooth-walled(toreducemoisture
and mould trapping), plastic-coated metal pipes or plastic pipes coated with inner antimicrobial layers.
Pipesaretypicallyburiedbetween1.5mand3mundergroundwheretheambientearthtemperatureis
almost constant year round in the temperate latitudes where most humans live. This results in an earth
temperature that is lower than the ambient conditions during summer days and higher than ambient
conditions during winter nights.
Pipesrun4to6feetdeep
Open-loop air-tube heating/
cooling system
Figure: www.energybulletin.net
This fgure presents an open-loop air-tube system used
or both cooling and heating.
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720W stand alone solar
PV installation, Nollie se
Kloo, Ceres district
Photo: Riaan Meyer
A solar PV panel is a device that converts solar energy directly into electricity. The photo below
presents a solar PV panel installation on a arm near Ceres. The installation consists o our PV panels o
180Weach,withtheabilitytoproduceapeakelectricpoweroutputof720W.Onaverage,theinstallation
cangenerate3.6kWh(3.6kilo-Watt-hours(units)ofelectricity)perday.
Solar PV is perhaps the most expensive o the listed options, and is not as nancially viable as most o the
solutions listed above. However, with the cost o electricity ever on the increase, this solution will become
more aordable.
PV panels can be stand-alone systems as shown above or may be roo-mounted. In Southern Arica, xed
installations should preerably ace north to harness the optimal amount o sunlight. Shading on the panels
(rom trees and other structures) should be avoided.
PV panels can only produce electricity when the sun is shining. Batteries are used to store electricity, allowing
thistobeusedatalaterstage.SolarPVpanelscurrentlyretailaroundR50/W,hence180Wpanelsarepriced
ataroundR9000.
sOlaR phOtO vOltaic (pv)
panels
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case stUDy
Solar Roo Tiles
Solar PV panels are also available in the orm o roo tiles. The picture below shows a solar roo
tile installation at theDrieGeuwelsGuestHouse, located at theSustainability Instituteoutsideof
Stellenbosch. The PV roo tiles are o a similar shape and size as normal tiles and only make up a
portion o the total roo area, as can be seen rom the picture below. The peak output rom the PV
installation is 1.7kW. The daily energy generated rom this installation is monitored and can be seen at
www.sieckmann.biz/content/ProjectsSustanabilityInstituteReports.htm.The electricity generated by
this installation is ed directly into the guest house through a grid-tied inverter and is used to supplement
theelectricitycurrentlyprovidedbyEskom.Nobatteriesareinstalled.
Solar roo tile installation at the Sustainability
Institute near Stellenbosch.
Photo: Riaan Meyer
cOnclUsiOn
Renewable energy is derived rom natural resources like wind, sunlight, rain, tides and geothermal heat,
which are able to be naturally replenished. Renewable energy sources have a lower environmental impact than
modern non-renewable energy sources like oil and coal, and produce ar ew hazardous emissions. South
Arica has the potential to harvest wind and solar power on a large scale due to its climactic position and wind
availability. Technological solutions including solar water heaters, pico hydro systems, biogas digestors and
geothermal heating and cooling systems can assist in providing energy and in reducing peak load rom theNationalgrid.