07 Chapter 04 Renewable Energy Options

8/8/2019 07 Chapter 04 Renewable Energy Options

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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.

Documents

07 Chapter 04 Renewable Energy Options