Thesis (MScEng)--Stellenbosch University, 2012 / ENGLISH ABSTRACT: A technology that has advanced immeasurably as a result of the necessity for green energy production is the
harnessing of wind energy. One of the most important aspects of a wind turbine is its supporting structure.
The tower of a wind turbine needs to be sufficiently reliable and structurally sound to ensure that the design
life of the wind turbine machine is unaffected. The tower also needs to be of the correct height to ensure that
the full potential of energy capture is realised.
The supporting structure of a wind turbine constitutes up to as much as 30% of the total costs of a wind
turbine. The most common wind turbine supporting structures seen worldwide today are Steel Monopole
Towers. The large cost proportion of the tower compels the industry to investigate the most feasible
alternative supporting tower structures and thus prompted the research developed in this thesis. In this thesis
the focus is on small scale wind turbines (<50kW), more specifically, a 3kW Wind Turbine. The proposed
alternative design the support structures of small scale wind turbines to the presently used Steel Monopole
tower was a Steel Lattice tower.
Both a Steel Lattice and Steel Monopole Tower was designed for a 3kW Wind Turbine using rational design
methods determined from pertinent sections of the South African design codes. The Tower designs needed to
incorporate the details of the element connections, so as to encompass all of the cost parameters accurately.
The foundation design of each of the towers was also required from the point of view of cost analysis
completeness, and ended up playing a critical role in the feasibility analysis.
To validate the design methods, the two towers were modelled in the finite element package Strand7 and a
number of different analyses were performed on the two towers. The analyses included linear static, nonlinear
static, natural frequency and harmonic frequency analyses. The towers were assessed for a number of
different load case combinations and were examined in terms of stress states, mass participation factors and
deflections, to mention a few, for the worst loading combination cases that were encountered.
Once a final design was reached for both the Steel Lattice and Steel Monopole Towers, each element from
which they were made was assessed from a structural viewpoint to determine manufacturing and construction
costs.
The cost analysis was conducted by means of asking a number of leading construction companies for unit
prices for each of the identified elements to be assessed.
The fabrication and construction of each of the Towers was then compared to determine which one was more
feasible, in terms of each design aspect considered as well as looking at the complete end product.
It was found that the Steel Lattice Tower was more feasible from the points of view of fabrication, and
construction, as well as having a far more cost effective foundation. This was a positive conclusion from the
perspective of the proposal for a more feasible alternative to the presently used Steel Monopole Towers.
The outcome of the research conducted here could certainly prove to be worth considering from a wind farm
development perspective, with particular focus on the up and coming Wind Industry developments in South
Africa. / AFRIKAANSE OPSOMMING: As gevolg van die noodsaaklikheid vir die produksie van volhoubare energie is ʼn tegnologie wat met rasse
skrede vooruitgegaan het die vir die benutting van windenergie. Een van die belangrikste aspekte van 'n
windturbine is die ondersteunende struktuur. Die toring van 'n windturbine moet funksioneel en struktureel
betroubaar wees om te verseker dat die ontwerpleeftyd van die windturbine masjien nie nadelig beïnvloed
word nie.
Die toring moet ook die regte hoogte wees om te verseker dat die volle potensiaal van die wind energie in
meganiese energie omgesit word.
Die koste van die ondersteunende struktuur van 'n windturbine verteenwoordig tot 30% van die totale koste
van 'n windturbine. Die mees algemene vorm van ondersteunende strukture vir windturbines wat vandag
wêreldwyd teëgekom word, is die van 'n enkel staal buisvormige toring. Die groot koste‐komponent van die
toring dwing die industrie om ondersoek in te stel na die mees koste effektiewe prakties uitvoerbare
alternatief vir die ondersteunende toring struktuur. Hierdie aspek van die struktuur konseptualisering het gelei
tot die navorsing wat in hierdie tesis onderneem is. Die fokus van die navorsing is op klein skaal windturbines
(<50kW), en meer spesifiek op 'n 3kW windturbine model. Die alternatiewe ontwerp wat ontwikkel is vir klein
skaal wind turbines se ondersteunende structure, is 'n staal vakwerk toring as alternatief vir die staal
buisvormige toring.
Beide 'n staal vakwerk en staal buisvormige toring vir 'n 3kW wind turbine is ontwerp deur rasionele ontwerp
metodes. Die toepaslike gedeeltes van die Suid‐Afrikaanse ontwerp kodes is hiervoor gebruik. Die ontwerp vir
die toring moet die besonderhede van die element verbindings in ag neem en die nodige koste parameters
moet akkuraat bepaal word. Die ontwerp van die fondament van elke toring is ook noodsaaklik vir die
volledigheid van die koste‐ontleding en dit speel ook 'n kritieke rol in die gangbaarheid analise.
Om die ontwerp metodes te bevestig, is die twee tipes torings in die eindige element pakket, Strand7,
gemodelleer en 'n aantal verskillende ontledings vir die twee torings is uitgevoer. Die ontledings sluit lineêr en
nie‐lineêr statiese ontledings asook natuurlike frekwensie en dinamiese ontledings onder harmoniese
belastings in. Die torings is vir 'n aantal verskillende lasgevalkombinasies ondersoek en in die spannings
toestande, massadeelname faktore en defleksies vir die ergste laskombinasie gevalle wat ondervind is, is
geassesseer.
Sodra 'n finale ontwerp vir beide die staal vakwerk en staal buisvormige toring voltooi is, is elke element
beoordeel uit 'n strukturele en materiaal oogpunt om die kostes daarvan te bepaal.
Die koste‐analise is baseer op data wat voorsien is deur 'n aantal vooraanstaande konstruksiemaatskappye op
'n prys per eenheid basis vir elk van die geïdentifiseerde elemente wat geassesseer moes word.
Die vervaardiging en konstruksie van elke toring is dan vergelyk om te bepaal watter een die mees haalbaar is,
in terme van elke toepaslike ontwerpsaspek en deur ook die volledige eindproduk te evalueer.
Daar is bevind dat die staal vakwerk toring uit die oogpunt van vervaardiging en konstruksie, asook as gevolg
van 'n meer koste‐effektiewe fondament, die voorkeur alternatief verteenwoordig het. Dit was 'n positiewe
gevolgtrekking uit die oogpunt van die soeke na 'n ander alternatief as die buisvormige staal torings wat tans
algemeen in gebruik is.
Die uitkoms van hierdie navorsing verdien oorweging uit ʼn windplaas ontwikkelingsperspektief, met ʼn
spesifieke fokus op die opkomende ontwikkelinge in die wind energie industrie in Suid‐Afrika.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/71848 |
| Date | 12 1900 |
| Creators | Nel, Emma |
| Contributors | Strasheim, J. A. v B., Dunaiski, P. E., Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 122 p. : ill. |
| Rights | Stellenbosch University |
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