Development of a non-invasive water flow meter for a smart geyser

Thesis (MEng)--Stellenbosch University, 2018.ENGLISH ABSTRACT: South Africa has experienced electricity and water shortages in recent years. The use of smart geyser controller units has the potential to decrease the electricity and water consumption associated with the domestic sector. The installation of an in-line, invasive flow meter is the most expensive aspect of the costs associated with smart geyser controllers. The aim of the project is to develop a non-invasive, retrofit water flow meter which is intended to be used for smart geyser controllers in domestic applications. The successful design of such a non-invasive water flow meter would decrease the installation cost and installation inconvenience associated with smart geyser controllers. This means that more individuals can use smart geyser controllers which can result in a greater total decrease in resource consumption. Several non-invasive fluid measurement methods were investigated in the context of domestic hot water flow. Many were found to be too expensive or require complex installation which meant that they would not provide the intended convenience to users. Thermal methods and vibration methods were investigated to design a non-invasive flow meter which required less expensive components and did not require a complex installation. The use of thermal methods only to measure domestic flow was investigated. It was determined to be impractical due to the small temperature differences associated with domestic conditions and the diffcult installation required for accurate temperature measurements using inexpensive sensors. A non-invasive flow estimation algorithm was designed which used the fusion of thermal and vibration data provided using relatively inexpensive sensors which did not require complex installation. The algorithm was able to detect hot water usage events with over 90% accuracy using thermal and vibration data. Event detection was successful for flow events spaced at least 2 minute apart. Flow rate estimation was performed using vibration data. A quadratic relationship between higher industrial flow rates and vibration standard deviation was found in literature, but a linear relationship was found for domestic conditions. Suficiently accurate quantitative flow rate estimation was possible for flow rates above 5 L min -1. The consumption patterns which occurred within these algorithm limitations were found to constitute 60% of measured volumetric consumption for anonymous smart geyser controller units in a field dataset. The use of fixed flow rate approximations for low flow rates (which could be detected but not quantitatively estimated) increased the simulated performance of the system from the mentioned 60% to 90%. The volumetric flow estimation accuracy of the algorithm was sufficient and the same error margins of 10% were achieved which matches the in-line flow meter currently used in installations. The results of this study show a proof of concept that non-invasive flow measurement can be performed for domestic conditions using the combination of thermal and vibration methods. The required consumption data can be gathered with a system that does not require expensive components or a complex installation procedure.AFRIKAANSE OPSOMMING: Suid-Afrika het die afgelope paar jaar elektrisiteit en water tekorte ondervind. Die gebruik van slim waterverhitting-toestel beheerders het die potensiaal om die elektrisiteit en water verbruik van die huishoudelike sektor te verminder. Die installering van 'n interne en indringende vloeimeter is die duurste aspek van die kostes verbonde aan hierdie slim waterverhitting-toestel beheerders. Die doel van hierdie projek, is om 'n nie-indringende watervloeimeter vir slim waterverhitting-toestel beheerders te ontwikkel wat vir huishoudelike toepassing in die sisteem geintegreer kan word. Die suksesvolle ontwikkeling van so 'n nie-indringende watervloeimeter sal die installasiekoste en ongerief verbonde aan die instaleering van slim waterverhitting-toestel beheerders verminder. Dit sal meer individue in staat stel om hierdie slim waterverhitting-toestel beheerders te gebruik, wat kan lei tot 'n groter afname in hulpbron verbruik Verskeie nie-indringende vloeistofmetingsmetodes is ondersoek in die konteks van huishoudelike warmwatervloei. Baie is te duur bevind of vereis komplekse installasie wat beteken dat hulle nie die beoogde gerief aan verbruikers sal verskaf nie. Termiese metodes en vibrasie metodes is ondersoek om 'n nie-indringende vloeimeter te ontwerp wat goedkoper komponente bevat en nie ingewikkelde installasie vereis nie. Die gebruik van termiese metodes alleen vir huishoudelike gebruik, is ondersoek. Dit was vasgestel dat dit onprakties sal wees weens die klein temperatuurverskille wat verband hou met huishoudelike toestande en die moeilike installasie wat benodig word vir akkurate temperatuurmetings deur goedkoop sensors te gebruik. 'n Nie-indringende vloeiskatting-algoritme is ontwerp wat gebruik maak van die samesmelting van termiese- en vibrasiedata en wat ook relatief goedkoop sensors verg met minder komplekse installasie. Die algoritme kon warm waterverbruik met meer as 90% akkuraatheid bepaal. Gebeurlikheid opsporing was suksesvol vir vloeibewegings wat ten minste 2 min uit mekaar uit was. Vloeitempo skatting is uitgevoer met behulp van vibrasie data. 'N Kwadratiese verhouding tussen hoër industriële vloeitempo's en vibrasie-standaardafwyking is in die literatuur aangetref, maar 'n lineêre verhouding is gevind vir huishoudelike toestande. Voldoende akkurate kwantitatiewe vloeitempo skatting was moontlik vir vloeitempo's bo 5 L min-1. Die verbruikspatrone wat binne die algoritme-beperkings plaasgevind het, was 60% van die gemete volumetriese verbruik vir onbekende slim waterverhitting-toestel beheerders in 'n veld datastelsel. Die gebruik van vaste vloeitempo-benaderings vir lae vloeitempo's (wat opgespoor kon word maar nie kwantitatief geskat was nie) het die gesimuleerde prestasie van die stelsel verhoog van die genoemde 60% na 90%. Die volumetriese vloeiberaming se akkuraatheid van die algoritme was voldoende en het dieselfde foutspeling van 10% behaal, wat ooreenstem met die inlyn vloeimeters wat tans in installasies gebruik word. Die resultate van hierdie studie toon 'n konseptuele bewys dat nie-indringende vloeimeting vir huishoudelike toestande uitgevoer kan word deur n kombinasie van termiese en vibrasiemetodes te gebruik. Die vereiste verbruiksdata kan ingesamel word met 'n stelsel wat nie duur komponente of 'n komplekse installasieprosedure benodig nie