Critical evaluation of large-scale gravity energy storage using linear vernier hybrid machine technology

Date
2021-12
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: Energy storage technologies have received increased research attention in recent years. As a result of the wide array of technologies and possible applications, energy storage is predicted to play a critical role in helping countries transition towards zero-emission electricity generation. However, due to the wide range of technologies, it can become difficult and cumbersome to determine the best technology for a certain application. This dissertation proposes and investigates a novel gravity energy storage method. The linear electric machine-based gravity energy storage (LEM-GES) system uses linear electric machines to vertically hoist solid masses, called pistons, to store energy. The use of LEMs allows for multiple pistons to be used in a single shaft, thus increasing the energy storage capacity of the system. The consequent-pole linear Vernier hybrid machine (CP LVHM) was chosen as the LEM topology due to its ability to operate at low velocities with high efficiencies and because of the reduction in required permanent magnet (PM) material. The CP LVHM was thoroughly investigated using finite element (FE) models, the Taguchi method and an analytical air gap flux density model. Equations describing the physical, technical and economic characteristics were devel- oped for the LEM-GES system. From these equations, an optimisation process for the LEM-GES system was proposed. This optimisation process combined the FE model of the CP LVHM with the economic and physical model of the LEM-GES system to determine the CP LVHM design that results in the lowest levelised cost of energy storage. Using this proposed process, it is shown that the LEM-GES system is very cost-competitive for high power applications requiring high annual cycles.
AFRIKAANSE OPSOMMING: Daar is in die afgelope dekade ’n toenemende hoeveelheid navorsingsaandag gegee aan en- ergiestoortegnologie. As gevolg van die verskeidendheid tegnologie en toepassings word dit voorspel dat energiestoor ’n beduidende rol sal speel in die oorgang na skoon elektrisiteits- opwekking. Dit is egter moeilik om die beste tipe tegnologie vir ’n bepaalde gebruik vas te stel. Hierdie verhandeling stel ’n nuwe gravitasie-energiestoormetode voor. Die lineêre elek- triese masjiengebaseerde energiestoor- (LEM-GES) sisteem gebruik lineêre elektriese masjiene om soliede massas vertikaal te beweeg en sodoende energie te berg. Die gebruik van LEM’s beteken dat veelvoudige massas in ’n enkele skag gebruik kan word. Sodoende word die energiestoorkapasiteit van die sisteem verhoog. Die konsekwente-pool lineêre Vernier hibriede masjien (KP LVHM) is gekies as die LEM tegnologie vir sy vermoë om teen lae spoed met ’n hoë benuttingsgraad te werk, asook die verlaagde hoeveelheid permanente magneet (PM) materiaal wat gebruik word. Die KP LVHM is deeglik ondersoek deur die gebruik van eindige element simulasies, die Taguchi-metode en ’n analitiese model van die lugspleet vloeddigtheid. Vergelykings wat die fisiese, tegniese en ekonomiese eienskappe van die LEM-GES sis- teem beskryf, is ontwikkel. Die vergelykings is gebruik om ’n optimeringsproses vir die stelsel voor te stel. Die proses kombineer die eindige element model van die KP LVHM met die ekonomiese en fisiese model van die LEM-GES sisteem om die laagste moontlike sisteemkoste te bepaal. Gevolglik word dit bewys dat die LEM-GES sisteem baie koste- effektief is as dit vir hoë drywingtoepassings gebruik word.
Description
Thesis (PhD)--Stellenbosch University, 2021.
Keywords
Critical evaluation, UCTD, Energy storage technologies, Hybrid power systems, Linear vernier hybrid
Citation