Thesis (MEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Solar Assisted Power Generation (SAPG) can be seen as a synergy of solar and fossil
plants – combining the environmental benefits of the former and the scale, efficiency
and reliability of the latter. SAPG offers great potential for cost effective utilization
of solar energy on utility scale and could accelerate the adoption of solar thermal
energy technologies in the short and medium term, especially in countries with a
significant coal base and a good solar resource such as Australia, China, United
States, India and South Africa.
SAPG is the replacement of bled-off steam in a Regenerative Rankine power cycle.
Power plant simulations were performed using weather data for Lephalale, South
Africa (Matimba power station). With an increase in the solar field outlet
temperature, an increase in overall solar to electric efficiency was observed, superior
to a stand-alone Solar Thermal Power Plant(s) (STPP) at similar temperatures.
The performance of four solar collector technologies was compared: flat plate,
evacuated tube, Linear Fresnel (LF) and Parabolic Trough (PT). This comparison
was limited to the normal incidence angles of irradiation. For this application, nonconcentrating
technologies are not competitive.
For non-normal incidence angles, annual simulations were limited to PT and LF at
final feedwater heater temperatures. The actual aperture area of around 80 000 m2
was used (50 MW thermal based on LF). On an equal aperture area basis, PT
outperforms LF significantly. For the conventional North-South arrangement, LF
needs to be around 53% of the specific installation cost (in $/m2 aperture area) of PT
to be cost competitive. A SAPG plant at Lephalale was compared to a stand-alone Solar Thermal Power
Plant STPP in a good solar resource area, namely Upington, South Africa –
Parabolic Trough solar collector fields of equal size were considered for both
configurations. It was found that the annual electricity generated with a SAPG plant
is more than 25% greater than a stand-alone STPP. If the cost of SAPG is taken as
72% of the cost of a stand-alone STPP, this translates into SAPG being 1.8 times
more cost effective than stand-alone STPP. Furthermore, SAPG performs better in
high electricity demand months (South African winter – May to August).
Stand-alone STPP have been adopted in South Africa and are currently being built.
This was achieved by the government creating an attractive environment for
Independent Power Producers (IPP). Eskom, the national power supplier, is currently
investigating solar boosting at existing Eskom sites. This report argues that on a
national level, SAPG, specifically solar preheating of feedwater, is a more viable
solution for South Africa, with both its significant coal base and good solar resource. / AFRIKAANSE OPSOMMING: Son ondersteunde krag generasie (SOKG) kan gesien word as sinergie van sonkrag en
fossiele brandstof aanlegte – dit voeg die omgewings voordele van die eersgenoemde
en die grote, effektiwiteit en betroubaarheid van die laasgenoemde by mekaar. SOKG
opper groot potensiaal vir koste effektiewe gebruik van son energie op
nutsmaatskappyskaal en kan die aanvaarding van sontermiese energietegnologieë in
die kort en medium termyn versnel, veral in lande met beduidende kool reserwes en
goeie sonkrag voorkoms soos Australië, China, Verenigde State van Amerika, Indië
en Suid-Afrika.
SOKG impliseer die vervanging van aftap stoom in die regeneratiewe Rankine krag
kringloop. Kragstasie simulasies was gedoen met die gebruik van weer data van
Lephalale, Suid-Afrika (Matimba kragstasie). Met die toename van die sonveld
uitlaat temperatuur kon oorhoofse son-na-elektrisiteit effektiwiteit vasgestel word,
wat hoër is as die van alleenstaande sontermiese krag stasie (STKS) by soortgelyke
temperature.
Die effektiwiteit van vier son kollekteerder tegnologieë was vergelyk: plat plaat,
vakuum buis, lineêre Fresnel (LF) en paraboliese trog (PT). Die vergelyking was
beperk tot normale inval van bestraling. Vir hierdie toepassing is nie-konsentreerende
tegnologie nie mededingend nie.
Vir nie-normale inval hoeke was jaarlange simulasies beperk tot PT en LF by finale
voedingswater temperatuur. Die werklike opening area van omtrent 80 000 m2 was
gebruik (50 MW termies gebaseer op LF). By gelyke opening area, uitpresteer PT LF
beduidend. Vir die gebruiklike Noord-Suid rankskikking benodig LF omtrent
53% van die spesifieke installasie kostes (in $/m2 opening area) van PT om kostes
mededingend te kan wees. ‘n SOKG aanleg by Lephalale was vergelyk met alleenstaande STKS in die goeie son
voorkoms gebied van Upington, Suid-Afrika – Paraboliese trog kollekteerder velde
van gelyke grote was oorweeg vir al twee konfigurasies. Dit was gevind dat die
jaarlikse elektrisiteit gegenereer vanaf SOKG meer as 25% is as die van alleenstaande
STKS. Indien SOKG oorweeg word met 72% van die kostes van alleenstaande STKS,
dan beteken dit dat SOKG 1.8 keer meer koste effektief is as alleenstade STKS.
Verder, SOKG presteer beter in die hoer elektrisiteitsnavraag maande (Suid-
Afrikaanse winter – May tot Augustus).
Alleenstaande STKS is gekies vir Suid-Afrika en word tans gebou. Dit is bereik deur
dat die regering ‘n aantreklike omgewing geskep het vir onafhanglike krag
produsente. Eskom ondersoek tans SOKG by bestaande Eskom persele. Hierdie
verslag beweer dat op nasionale/Eskom vlak, SOKG, besonders son voorverhitting
van voedingswater, meer haalbare oplossing is vir Suid-Afrika met sy beduidende
koolreserwes en goeie son voorkoms.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/80139 |
| Date | 03 1900 |
| Creators | Pierce, Warrick Tait |
| Contributors | Gauche, P., Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | xi, 44 p. : ill. |
| Rights | Stellenbosch University |
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