Automating Residential Water Filters

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Bachelor of Science Thesis

KTH School of Industrial Engineering and Management Energy Technology EGI-2017

TRITA-ITM-EX 2018:629 SE-100 44 STOCKHOLM

Automating Residential Water Filters

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Bachelor of Science Thesis EGI-2017 TRITA-ITM-EX 2018:629

Automating Residential Water Filters

Oskar Vågerö Approved 2018-08-30 Examiner Andrew Martin Supervisor Andrew Martin

Commissioner Contact person

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-3-Abstract

It is not uncommon to install private water filters in Malaysia, to rid the water of heavy metal contaminants, chlorine and bacteria. The main objective of this study was to redesign the base structure of a commercially available water filter (by Blöndal Water Group) in order to allow for an automated backwashing and rinsing function of the filter. Additional focus was laid on creating an energy efficient mechanism for compatibility with different power sources, including solar energy. The study consists of two parts, firstly a literature study of selected relevant areas necessary to understand the product, the water filter industry and the solar photovoltaic market and secondly a conceptual development where material has been created to support the decision-making for continued research and development of the product.

In order to allow for an energy efficient construction, the focus was laid on changing the shaft from a push- and pull motion into a rotational movement, controlling the direction of the water flow. The shaft was redesigned to accommodate for the rotational movement and was divided into three parts, each third corresponding to 120 degrees of rotation. Once the details of the redesigned shaft and base structure were in place, the power source to supply the rotational mechanism with electricity was investigated and found out to ideally be from a simple stand-alone battery. The idea of using solar panels was not recommended, mainly due to the added complexity to the product and due to the fact that the energy required is considered low, even for a very small 10W solar panel.

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-4-Sammanfattning

Det är inte ovanligt att installera privata vattenfilter i Malaysia, för att rena vattnet från tungmetaller, klorin och bakterier. Det främsta syftet med den här studien var att designa en ny basstruktur för ett kommersiellt tillgängligt vattenfilter (av Blöndal Water Group) som tillåter implementerandet av en automatiserad backspolning och rensning av filtret. Vidare lades fokuserades på att ta fram en energieffektiv mekanism för kompatibilitet med olika kraftkällor, inklusive solenergi. Studien består av två delar, först en litteraturstudie där fakta och information inom utvalda och relevanta områden togs fram för att förstå produkten, vattenfiltersindustrin och även solcellsmarknaden i Malaysia, därefter bestod studien av en konceptuell utveckling där underlag skapades för att stödja beslutsfattandet kring fortsatt forskning och utveckling av produkten.

I syfte att skapa en energisnål konstruktion så lades fokus på att omvandla den existerande push- och pullfunktionen till en roterande rörelse istället som ändrar vattnets flödesriktning. Kolven designades om för att kunna utnyttja rotationen och delades in i tre delar, var och en motsvarade 120 graders rotation. När väl detaljerna av basstrukturen och kolven var på plats undersöktes och kraftkällan som skulle driva denna rotation med hjälp av elektricitet. Det koms fram till att ett ensamt, enkelt batteri var den bästa lösningen. Implementerandet av solceller som kraftkälla rekommenderades inte, dels på grund av komplexiteten i konstruktionen och dels på grund av att det faktum att energin som krävs för att driva rotationen inte var tillräckligt hög för att det skulle löna sig med solceller. Detta till trots att det finns små solceller på enbart 10W.

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Figures

Figure 1 Flow Chart Over the Operation Mode ... 14

Figure 2 Flow Chart Over the Backwash Mode ... 14

Figure 3 Overview of the 90 degrees concept ... 20

Figure 4 Overview of the 120 degrees concept ... 21

Figure 5 New Shaft Design | Operation View ... 21

Figure 6 New Shaft Design | Backwash View ... 21

Figure 7 New Shaft Design | Rinse View ... 21

Figure 8. Section View of the Base Structure Assembled ... 22

Figure 9 Flow Chart Over the Rinse Mode ... 23

Figure 10. Shaft Overview during Operation ... 23

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Tables

Table 1. Filtering Techniques and Their Filtrate Size ... 13

Table 2 TNB Electricity Tariff (TNB, 2018b) ... 15

Table 3. Power Device Comparison ... 25

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Nomenclature

Symbols

Sign Name Unit

A Area [m2_] d Thickness [m] E Energy [Wh] H Solar irradiance [Wh/m2₎ I Moment of Inertia [kgm2_] P Power [W] p Pressure [Pa] PR Performance Ratio [1] Q Flow rate [m3_/s] R Solar yield [W/m2_] r shaft radius [m] T Torque [N/m] t Time [s]

α Angular Acceleration [rad/s2_]

β Angle [1]

 Density [kg/m3_]

σ Yield Stress [Pa]

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-10- Abbreviations

CdTe Cadmium-Telluride

CIGS Copper-Indium-Gallium-Disenlenide c-SI Crystalline Silicon

DoD Depth of Discharge

DoE Department of Energy of the United States

EPA Environmental Protection Agency of the United States GAC Granular Activated Carbon

kWh kilowatt hour

kWp kilowatt peak

Pa Pascal PoE Point of Entry PoU Point of Use

PP Polypropylene psi pound per square inch

PV Photo Voltaic

RM Malaysian Ringgit

RO Reverse Osmosis

SDGs Sustainable Development Goals TNB Tenaga Nasional Berhad

UF Ultra-Filtration

UN United Nations

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1 Introduction

At the UN World Summit in September 2015, world leaders adopted to the 17 Sustainable

(Development Goals (SDGs) of the 2030 Agenda for Sustainable Development, which aims to end

all forms of poverty, fight inequalities and tackle climate change (UN, 2017). The sixth SDG is to ensure access to water sanitation for all. Although this is an absolutely essential part of the world we live in, the UN (2017) estimates that at least 1.8 billion people globally use a source of drinking water that is contaminated.

Access to clean water is an absolute necessity for everyone living in this world, which highlights the importance of water filtering systems. With an annual population increase of 1.5 percent in Malaysia (World Bank, 2016), excessive discharge of industrial contaminants and increased pesticide usage for agricultural purposes (Frost & Sullivan, 2014), the availability of qualitative and clean water is imperative. Technological innovation in water treatment has an important role to play and has already evolved to combat the challenge of deteriorating drinking water quality. An increased availability of clean and high-quality tap water can also help reduce the consumption of water through plastic bottles. Although recycling practices have caught up in most parts of the world, The Earth Policy Institute estimates that the energy used in the entire lifecycle of plastic bottles is over 50 million barrels of oil annually (Frost & Sullivan, 2014). Malaysia is, in contrast to most countries, moving towards centralizing their water governance (Chan, 2009). Centralized water treatment implies treating, usually large amounts of, water in central locations at high rates before distributing it through pipes (PennState Collage of Earth and Mineral Sciences, 2018). Decentralized water treatment on the other hand can be considered as stand-alone facilities and part of a permanent infrastructure. This system can be integrated with centralized water treatment (EPA, 2015)

1.1 Water Situation in Malaysia

The water service industry in Malaysia is under reform to ensure proper water supplies for both current and future needs. The growing population, rapid urbanisation and industrialisation of Malaysia are straining the water supply, and in combination with threats of climate change, the future forecasts more frequent shortages of water and severe drought (Teo, 2014).

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efforts towards enabling improved long-term performance of decentralized water purifiers are therefore of interest both to consumers and suppliers.

1.2 Goal and Objectives

The goal of the study is to investigate on how to upgrade a commercially-available Point of Entry (PoE) water filter (“Modular Series”, supplied by Blöndal Water Group) into a more efficient product. The product is to be developed with an automatic backwash and rinsing to clean the filters on a regular basis, instead of the existing manual backwash. The current solution creates insecurity if the user neglects to flush the filters and an automatic solution opens up for a more optimised backwash schedule.

The primary focus of the study will be to redesign the product base’s structure to accommodate the automatic backwash and rinsing mode, where the driving force is from either solar energy, battery power or direct current from the household. In either of the powering mechanisms, the design of the base structure will be of great importance in order to create a power efficient mechanism.

The results of the study will lay the groundwork for a more sustainable product with not too elevated costs, and thus maintained availability, for the consumers. The cost and design of the product is absolutely critical to keep the price of the product low and available for the increasing population of Malaysia. The product also has potential outside of Malaysia in countries with similar accessibility to clean water as in Malaysia. With the finalization of the study, it will act as material for the continuous development of the product.

1.3 Method

The study will consist of three parts, with the first part being a preparatory literature study, the second part field studies and lastly, a conceptual development of the product.

1.3.1 Literature Studies

As preparation for the project, the current state of the product was investigated. How does it function, what technical aspects needs to be covered and what are the current challenges? Only after complete understanding of the product, was it possible to begin to solve the challenges and improve the product.

Furthermore, the geographical conditions were to be evaluated in terms of e.g. PV potential, solar irradiance and water supply. The KTH Primo search engine has been the primary database for scientific reports and studies for the literature studies. The results of the literature studies are shown chapter 1. Introduction.

1.3.2 Field Study

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Once the product was studied and understood in every aspect, a concept of how to develop the product was initialized. The conceptual development included 3D-models, drawings and calculations on the product.

1.4 Modular 1,2,3 Point-of-Entry (PoE) Water Filter

The Blöndal Modular series is a water purification system designed to maximize filtration and purification of various types of water contaminants. The system is capable of eliminating up to 99% of the water contaminants while absorbing chemical compounds such as chlorine to a safe level. The techniques used in the Modular 1, 2 and 3 series are Polypropylene Filter, Granular Activated Carbon (GAC) and an Ultra-Filtration (UF) Membrane (Blöndal, 2016).

Table 1. Filtering Techniques and Their Filtrate Size

The Blöndal Modular series allow for adjustment according to the user’s water conditions. The 1, 2 and 3 series represent the number of cartridges that the water filter consists of.

The Modular Series are constructed as “outside-in” filters, which means that the water flows through the filter from the outside, in through the filter and then from the inside towards the outlet.

1.4.1 Concept of the Water Filter

The product is pressure driven, operating around 2 bar during normal conditions in Malaysia. It has two different modes, operation and backwash, that can be switched between by a manual pedal on the outside of the product. Pushing the pedal down pulls the shaft in the middle of the base structure backwards, changing the flow of direction for the water.

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Figure 1 Flow Chart Over the Operation Mode

During the backwash mode, the water flow is, through the adjustment of the shaft, going the reversed direction compared to during the operation mode. The water travels from the inlet, and then goes from the inside of the filter out to unclog any of the filtered particles that the filter has accumulated. The backwash water goes out through a separate outlet to separate it from the drinking water. The purpose of the backwash function is to increase the longevity of the filter.

Figure 2 Flow Chart Over the Backwash Mode

The different flow of directions for the product is illustrated in Figure 1 and Figure 2. The user put their foot on a pedal connected to the shaft in order to push or pull the shaft between the two modes. The manual backwash function requires a high force, which would be problematic when automating the function, since the energy usage would then be very high. In order to be able to make an automated solution with either a battery or solar panels, it is important that the energy requirements are as low as possible.

After the backwash, the inside of the filter is filled with dirty water, and an instant switch from backwash to operation would lead to dirty water for the user. The solution to this was a separate outlet pipe connected after the operation outlet which the user could switch on and off manually. This also needed automatization.

In order to control and power the automated mechanisms, when the power is no longer manual by pressing the pedal, energy is required.

1.5 Rotary Solenoids

Rotary Solenoids converts axial motion into rotary strokes using electrical current running through a coil. Magnetic fields are created when electrical current is supplied into a coil, which in turn leads to a plunger drawn by the magnetic field into an extended position, rotating the solenoid. Typically, rotary solenoids have a relatively high force adjacent to the original position, which declines further from the original position. Step rotary solenoids have multiple magnetic poles to increase the precision and the position control. They are usually durable, high-torque devices with a permanent magnet holding the position even when not in power (IEEE, 2018).

1.6 Solar Energy in Malaysia

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A basic photovoltaic cell transforms direct sunlight into electric energy through a thin wafer of a semiconductor, commonly silicon. When the semiconductor is exposed to direct sunlight, electrons are knocked out of their positions in their atoms. If connected electrical conductors are attached, forming an electrical circuit, the electrons are captured in an electric current. The produced direct current can then be transformed into alternating current for use in appliances(NASA, 2008; Solar Region Skåne, 2016).

Malaysia is located in the equatorial region with a favorable situation for developing solar energy as the average irradiance is 1634 kWh/m2_{per year (Chua & Oh, 2011). For solar energy} applications, the focus will be on photovoltaic technologies, which convert solar radiation into direct current electricity. There are currently 4 kinds of solar panels available in the PV market of Malaysia: Mono-crystalline Silicon, Poly-crystalline Silicon, Copper-Indium-Disenlenide (CIS/CIGS) and Thin Film Silicon. The mono- and poly-crystalline silicon performs best under hot, sunny conditions. For cloudy days, the CIS and thin film silicon perform better (Mekhilef et al, 2012).

1.6.1 Electricity Price

Electricity on the Malaysian Peninsula and in the Sabah region of Borneo is supplied by Tenaga Nasional Berhad (TNB), with the core business to develop, operate and maintain their power generating units. TNBs power generation comes from Thermal Power Plants, powered by either coil, oil or natural gas, or Hydro Plants, utilizing the energy from flowing water and converting potential energy to electrical energy (TNB, 2018a). In the TNB Annual Report of 2017, it is stated that 47,94 % of the generated power was from gas, 30,48 % from coal and 18,29 % from Hydro (TNB, 2017).

Table 2 TNB Electricity Tariff (TNB, 2018b)

TNB fixate their electricity tariff for domestic consumers within different intervals depending on your consumption, as can be seen in Table 2. The Government of Malaysia, together with TNB, continuously discuss the electricity tariff and on the 26th_{of December 2017, fixated the prices for} Peninsular Malaysia until 31st_{December 2020. The tariff was set to remain unchanged from the} last discussion in January 2014, which means that the Government of Malaysia will fund any increased costs in the production and operation of the power generation. Malaysian consumers will not notice any change in their electricity bill (TNB, 2017b).

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Crystalline silicon PV cells are produced from either mono- or polycrystalline silicon and have historically been the dominating choice for commercially available solar panels. c-SI are made of silicon (Si) atoms connected in a form of crystal lattice, that makes conversion of light into electricity more efficient. c-SIs have a higher efficiency than many other mass-produced materials and the modules have a life span of at least 25 years while still producing more than 80 % of the original power. A higher efficiency means that fewer solar cells needs to be installed, thus reducing the cost of the installation (DoE, 2018a).

1.6.3 Thin-Film Silicon

Thin-film solar cells consist of one or more thin layers of PV material on materials such as glass, plastic or metal. The two main types of thin-film solar cells are Copper-Indium-Gallium-Selenide (CIGS) and Cadmium-Telluride (CdTe) (DoE, 2018b). What makes CdTe solar cells excel is that they have a low manufacturing cost, due to the simplicity of the manufacturing process. These solar cells are almost perfect absorbers of sunlight as the wavelengths match very well. The abundance of Cadmium is also beneficial, but the fact that it is considered one of the most toxic materials found is a drawback. Another drawback is that although Cadmium is abundant, Tellurium is not. The CdTe solar cells also have lower efficiency levels than the c-SI (Encyclopedia Britannica, 2015).

Similar to CdTe, CIGS feature a thin film of copper indium selenide and copper gallium selenide which acts as a direct bandgap semiconductor. CIGS are more versatile than for example c-SI solar cells, which are rigid, and grants are greater opportunity for design variations. They are also much lighter and can be integrated into a greater variety of structures.

1.6.4 Choice of Solar Cell in Malaysia

A practical field study done in Malaysia in 2009 on the performance of c-SI and CIGS, evaluated the average power output, average module efficiency and performance ratio. By studying the output efficiency, and not only the power output of the models, the study could conclude that the CIGS had the best performance ratio and that it is the best performing type of solar cell for use in Malaysia (Amin et al. 2009).

With Malaysia’s tropical climate, the study highlights how the temperature affects the power output of solar cells and promotes the usage of CIGS solar cells.

1.7 Solar Storage

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The capacity of a solar battery is the total amount of electricity that it can store, measured in kilowatt-hours (kWh). The capacity does not take into consideration how much electricity can provided at a given time. For that we need to consider the power rating of the battery, which is measured in kilowatts (kW). These two units interact very closely. A battery with a high capacity and a low power rating would be able to provide a low dose of electricity over a long time, whilst a battery with a low capacity but a high power-rating would be able to provide a lot of electricity over a very short amount of time (EnergyUsage, 2018).

1.7.2 Depth of Discharge

The depth of discharge (DoD) refers to the amount of a battery’s capacity that has already been consumed. A higher percentage of DoD means that you have a longer time to use the solar battery before it needs to be charged. It is also important to most solar batteries to never reach a too low rate of DoD since that can be harmful to the chemical composition of the battery. Many manufacturers specify an optimal DoD for operation (EnergyUsage, 2018; Johansson, 2013). 1.7.3 Round-trip Efficiency

The round-trip efficiency of a solar battery is the difference between input and output of the battery. If you feed five kW into a battery and the output is four, then the round-trip efficiency is 0.8, or 80 % (EnergyUsage, 2018).

1.7.4 Battery Life

For any long-term storage, it is important to take into consideration the battery life, the length of time that you can use a battery before it needs to be exchanged. The solar batteries will charge and drain daily, with each cycle affecting the batteries’ possibility to be recharged the next time. It is not only important to consider the total life-time, but also how much of the capacity that is needed during each cycle. If a battery has an initial capacity of 10kWh and a battery life of 10 years, the capacity will not immediately change from 10 to 0kWhs. After 5 years, the capacity of the battery would be 5kWh, which might impact the life span of a battery (EnergyUsage, 2018).

1.8 Water Processing Techniques

There are a number of different ways of processing contaminated water and the following section gives a brief introduction to a few well-used methods, including polypropylene filtration, granular activated carbon and ultra-filtration membranes which are the basis of Blöndal’s Modular series. 1.8.1 Polypropylene Filtration

Polypropylene filters remove sand, corrosive products and impurities of up to 1 μm through mechanical filtration and are often used in the early stages of the filtration process (Dafi, 2015). 1.8.2 Granular Activated Carbon (GAC)

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are transferred to the chlorine in order to reduce it into non-oxidative chloride ion. The activated carbon acts as the reducing agent but loses its effectiveness as the carbon surface becomes filled up by the electrons (Law, 2005). The difference between Granular Activated Carbon (GAC) and Powdered Activated Carbon (PAC) is primarily the grain size, where GAC has a diameter ranging between 1.2 to 1.6 mm. GAC is made from organic materials such as wood, lignite and coal, that all have high carbon contents (EPA, 2018a). GAC is not cleanable and has a filtering capacity of about 6800 liters and should thus be replaced in intervals of about 6800 liters (Law, 2005). GAC treatment units are commonly placed either post-filtration absorption or as filtration-absorption. In the first example, the GAC unit is located after the conventional filtration process, where the contactor receives the highest quality water. This lets the GAC unit remove only dissolved organic compound and provides flexibility for designing specific absorption conditions. For the second example, on the other hand, some of the filter media is replaced with GAC. In this version, the GAC is also used for turbidity and solids removal. Filter-absorbers however, must be backwashed more frequently than the post-filter absorbers (EPA, 2018a).

1.8.3 Ultra-Filtration Membrane (UF)

Ultra-Filtration (UF) is a pressure driven process which is effective in removing colloids, proteins, and bacteria from the water, while letting salts through. The primary removal mechanism is size exclusion (Law, 2005). UF membranes are sensitive to fouling and plugging and therefore needs some type of pretreatment for the water to reduce the risk, but still requires routine backwashing to remove foulants from the membrane (EPA, 2018b).

1.8.4 RO Membranes

For osmosis systems, water with different concentrations of dissolved solids will be separated by a semi-permeable membrane, through which the water will flow, from the lower concentration to the higher until both sides reach the equilibrium state. Reverse osmosis is exactly what it sounds like, the osmosis process in reverse. This time the flow is reversed mechanically, and the concentrated solution is separated into water and dissolved solids. Dirty water is drained off in a capillary waste water controller. Reverse osmosis is efficient in purifying water from solutions such as heavy metals, chemical toxins, bacteria and viruses (Law, 2005).

RO membranes are usually divided into three different subgroups; tubular membrane, spiral wound membrane and hollow fiber membrane. The three membranes vary in their design and functionality. The spiral wound membrane can reject bacteria and 85 to 95 % of inorganic solids but it allows dissolved solids to pass through. The hollow fiber membrane on the other hand rejects dissolved solids but is susceptible to fouling and needs the feed water to be treated before passing through the hollow fiber (Law, 2005).

1.8.5 Nano Membranes

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2 Results and Discussion

The results of the project touch upon a wide variety of subjects, all necessary to consider when doing research and development of an already existing product. The result of the study is based upon factors such as manufacturing costs and techniques, the economic advantages and disadvantages, solid mechanics and durability, water flow rate and fluid mechanics to mention a few.

The maximum water pressure, 10 bar, that the product is designed for will be used for all of the calculations although it is about 5 times as high as the normal operating pressure.

2.1 Redesign of Base Structure

To avoid the high energy requirements of a push and pull motion, the focus was laid on introducing a rotating motion. The requirements for the rotating shaft was that it had to reduce the force needed to perform the action, and also to cope with changing the water flow between the different modes.

2.1.1 Shaft Design and Overview

From an economical and manufacturing perspective, the idea is to the changes on the base structure and instead redesign the shaft completely. The starting-point is a solid cylinder with a diameter of 36mm and a length of 180mm. To allow the water to flow from one point to another, volumes will be carved out of the shaft creating pathways for the water to travel. Two different designs of the shaft were considered. In the first design version, the shaft is divided into 4 parts, each representing a quarter of the volume. This concept would revolve around 3 modes or locations for the shaft, with either 90 degrees or 180 degrees rotation.

Figure 3 Overview of the 90 degrees concept

Figure 3 illustrates both the 4 quarters in which the shaft would be divided into and how they would be placed in the three different modes; operation, backwash and rinse. The rotation goes 180 degrees clockwise from operation to backwash and continues with two 90 degrees steps from backwash to rinse and from rinse back to operation.

With this concept, changes would have to be made both to the inlet and the location of the top holes, to the space where the water filter is located.

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Figure 4 Overview of the 120 degrees concept

Figure 5 New Shaft Design | Operation View

Figure 6 New Shaft Design | Backwash View

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Figure 8. Section View of the Base Structure Assembled

For the choice of material, ABS-plastic was chosen partly due to the simplicity of producing and manufacturing, which in turn reduces the cost of the product. ABS-plastic has a tensile strength to yield at 6 100 psi (42 MPa) and an E-Modulus at 310 000 psi (2.1 GPa) (Plastics International, 2018).

With a design in accordance to Figure 4 it is shown that the rotation of the shaft needs to be either 120 degrees clockwise or 240 degrees counter-clockwise. Figure 5, 6 and 7 gives an indication to the construction behind the reasoning. As seen in Figure 4, the 120 degrees construction does not allow for the water to simply travel out as the inlet and outlet are aligned horizontally. This was solved by utilizing a small portion of the backwash-third, as seen in Figure 5. During neither the backwash or the rinsing mode, the water travels through the outlet as it does during the operation mode. However, the space is occupied in the rinsing-third, which forces the usage of the backwash-third.

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Figure 9 Flow Chart Over the Rinse Mode

The two rinse/backwash outlets are placed as extensions to each end of the base structure and will be connected to the shaft, as seen in Figure 2 and Figure 9. In order to allow these two outlets to remain in a fixed position, a plain bearing will be placed between the outlet and the shaft to allow the shaft to rotate by the help of the motor, without also rotating the outlets. 2.1.2 O-Rings and Sealing Mechanism

To prevent the water from flowing in between the different hollows of the shaft, some sort of sealing mechanism was necessary for the construction.

An O-ring is a doughnut shaped object, commonly made from elastomers, used for closing off pathways and preventing leakage of fluids. By either mechanical or surrounding pressure, the O-ring is pressed into the small open pathway, completely closing it of for all other fluids operating in the system.

Nitrile Rubber is the most popular O-ring material and can operate between -30C to 100C. It is generally used in low pressure applications and has a high tensile strength (EPM, 2004).

Figure 10. Shaft Overview during Operation

Difficulties with the design arose as each third of the shaft is different and simply adding an O-ring to the structure leaves the O-O-ring hanging loose and not fixated. As illustrated in Figure 10, a thin outer ring with a path was added on to the structure in order to support the O-ring. The durability of the outer ring is verified in through the hoop stress equation (Sundström, 1998)

  pr

d , (1)

and through computation in MATLAB (see Appendix 6).

2.2 Power Requirements

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will be used to determine what kind of powering device can be used for the product as well as the choice of power source.

2.2.1 Rotational Inertia

For an object to rotate around an axis, a torque dependent on the mass and the distribution of the mass around the axis of rotation is required. In the case of this study, a cylinder is rotating around its center axis, which results in a moment of inertia, I according to equation (2)

I 1

2mr 2

(2)

(Khan Academy, 2018; Apazidis, 2012), with m being the mass and r being the radius of the shaft. Applying Newton’s 2nd_{law to equation (2) results in}

T I



. (3) With the use of the computational program MATLAB, the torque needed can be calculated into 6.4 mNm (see Appendix 6 for data input).

2.2.2 Friction Torque

The second torque is based upon the friction force between the O-ring and the base structure, in our case Nitrile Rubber against ABS-Plastic. Finding the friction coefficient between two materials is difficult and depends on factors such as, but not limited to, contact geometry, temperature and fluid properties (Blau, 2001). According to Parker Hannifin’s friction estimation, (2018), an estimation can be received from the following equation

F_f fci Lp fhi Ap , (4)

where Ff is the total friction, fc is the friction due to O-ring compression, Lp the length of seal

rubbing surface, fh the friction due to fluid pressure and Ap is the projected area of seal. The values are generated through Figure A6-5 and Figure A6-6 in Appendix 3 and together with

T F i r , (5)

results in a torque of 6.6mNm. 2.2.3 Water Pressure

Additionally, a force is applied from the water onto the shaft from the incoming water. The force that the water exerts is defined according to Karlsson, (2007) as

F 



V2

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2.3 Power Device for the New Concept

The total torque from equation (3), (5) and (6) is 33mNm and is what will be required for operating the rotational movement.

To perform such a movement, either a rotary solenoid or a stepper motor can be used. Both types of powering mechanisms can be found providing the necessary torque for rotating the shaft between its different modes. Rotary solenoids have the advantage of being less power consuming that its typical competitor. Some rotary solenoids are able to rotate both ways, which is often considered difficult for other low-power mechanisms (WiseGeek, 2018). Rotary solenoids are high speed devices with long life, often used within industrial automatization (Johnson Electric, 2018). Rotary stepper motors on the other hand are usually of easier constructions.

Table 3. Power Device Comparison

Rotary Solenoid Takano RSS14/10-CAB0 Appendix 5 Stepper Motor CNC 42 Stepper Motor Appendix 6 Torque 20mNm 220mNm Current 1,3 Voltage 12V 12-24V Power 12W 15,6W

Depending on local conditions and water quality, the backwash and rinsing mode each takes about one to two minutes of time. The power device will therefore not be running for more than 4 minutes per day. The power requirements for the power devices are equal to

E Pi t , (7)

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2.4 Power Source for the New Concept

No matter the design of the structure and the choice of powering device, the new product will need an input of power in order to power the new automated functions. As power supply for the product, the choices are either connecting the product straight to the household’s electrical grid, to utilize a changeable battery or to connect the product with solar panels and a solar battery.

Table 4. Advantages and Disadvantages of Power Sources

Power Source Advantages Disadvantages Household Electricity  No investment cost

 High power output

 Continuous energy costs  Dependent on energy grid  Sensitive to power disruptions Stand-Alone Battery  Low investment costs

 No continuous energy cost

 Simple

 Needs to be changed regularly, costly

Solar Panels  Continuous free energy supply

 High investment costs  More complex

 Design complications

Table 3 shows an overview of the advantages and disadvantages of the three different power sources.

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When automating this function, the need for energy is introduced, compared to the original product. Depending on the powering mechanism for the automated function, different power sources is preferred and possible. As illustrated in Figure 11, three alternatives are addressed, connecting to the grid (household energy), solar panels or stand-alone batteries.

2.4.1 Connection to the Household

Connecting the product directly to the household would allow for high power output and simplicity in the term of power source, and no true investment cost if the product is located close to a power source. However, PoE water filtration systems might not necessarily be installed close to power sources and might require the drawing of cords to the product. It also puts an additional burden on to the household’s power grid, which could have an effect on other functions of the household. The solution would also result in a continuous energy cost for the consumer, which would be added onto their electricity bill.

Furthermore, in the case of power outages, the system would not function and could interfere with the backwashing schedule, leaving the consumer without access to clean drinking water during such circumstances.

2.4.2 Stand-Alone Battery

Using a stand-alone battery as the power supply would mean simplicity in the design of the product and it does not require any huge modifications to maintain the current design. The downside however, would be that the battery will need to be changed from time to time, adding an extra task for service technicians. It would therefore be of great importance to match the life span of the battery to the life span of the filters, to ensure that the service technicians do not need to make additional trips in order to change the battery of the product. Some other benefits of the battery-solution are that all of the disadvantages of the direct connection to a household are removed. There is no longer a cost related to the energy supply of the product, no dependency on the energy grid for availability.

2.4.3 Solar Panels

Adding solar panels to the product as a power source requires further changes to the design of the product. Decisions need to be made as to where the panels need to be located, how to draw the cords to the solar battery and onto power the device. Malaysia does however have a favorable position, being located in the equatorial region with a high solar irradiance. If the power requirements are low however, the payback time for the solar panel investment will be longer, as little energy will be used and saved.

The energy provided by a solar panel can be calculated through

E Ai r i H i PR , (8)

(Labouret & Villoz, 2010) with the in data of a 10W Solar Panel (see Appendix 3 for details), and would in this case result in a daily energy generation of 33 Wh.

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For storing the energy from the solar panel, a 12Ah solar battery running on 12V can store 144 Wh of energy. Smaller battery packs tend to not have the same life span and have thus been disregarded to a higher extent.

As seen previously, the energy requirements from equation (7) for the two different power devices (rotary solenoid and stepper motor) are much lower than what can be stored by even the smallest solar panel battery. The energy requirement together with the energy tariff can be used to calculate the potential savings, S, from energy cost in accordance with

S Ei RM i t. (9)

Here, E is the energy requirement from equation (7), RM is the electricity tariff from Table 2 and

t is the time period that is observed, in this case one year. With such energy requirements from

the power devices, the savings would be about 0.15RM per year for the solar panel option compared to the direct connection to the household.

2.5 Sensitivity Analysis

It is important to note that the calculations of the study are based upon a lot of assumptions and estimations, which will affect the end result of the study. The result of the study should be viewed upon as a pre-study, giving clear indications in the decision making on how to further develop the existing product.

2.5.1 Torque Assumptions

Some of the assumptions made are the ones for the torque calculations. When calculating the torque dependent on the moment of inertia and angular acceleration, it shall be mentioned that the shaft is not actually one solid cylinder, but rather several small cylinders with minor defects such as the walls supporting the O-rings. Another source of error is the angular acceleration, which has been approximated as no clear answer to how fast the rotation of the shaft needs to be. The current value of dt = 0.1s can affect the first torque greatly.

As previously mentioned, the actual friction between materials are very dependent on local conditions and should be looked upon as not very accurate. Difficulties with the in data and reading the graphs are also sources of error for the friction torque estimation.

Lastly, for the force from the water pressure it is assumed that it is evenly distributed over the surface area, which is likely not the case as the inlet is not perfectly aligned with the entire area. An uneven distribution also affects the lever arm that transforms the force into a torque.

It is however not the details of the study that are important, but rather the concept. Estimations do their part to illustrate and give indications as to what decision is the right one.

2.5.2 Irradiance in Malaysia

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3 Conclusion and Future Work

The goal of the study was to investigate on how to further develop the Modular Series, incorporating an automatic backwash and rinsing mode of the product while still maintaining the exterior design aesthetics and without the price escalating. The conclusion can be divided into two parts, one for the redesign of the base structure and one for the powering of the automated mechanism. Additional sub-goals were to expand the smallest cross-sectional areas in order to increase the water flow rate of the product.

3.1 Conclusion and Future Work of the Base Structure

The main idea behind the redesign of the base structure is to move from a linear push- and pull motion into a rotational movement in order to reduce the energy requirements. Blöndal had before the beginning of the study already tried an automatization with the already existing push- and pull motion and had discovered that it was to energy requiring, escalating the price of the product into non-sustainable levels. Figure 4 to Figure 7 illustrates the recommended design for the new rotational movement, while Figure 1, 2 and 9 illustrates the flow of the three different modes in the new design.

The shaft was designed in a way that minimized the changes onto the base structure and the primary modifications that was made onto the base structure were enlargement of the cross-sectional areas that the water flow through. This was made in order to increase the flow rate within the entire system.

One large obstacle was how to successfully include the rinsing mode into the structure, due to the limitation in available space. One major modification is thus the added separate outlet for the rinsing water, which separates the rinsing water from the filtrate water.

3.2 Conclusion and Future Work of the Powering Mechanism

The primary advantages and disadvantages of different power sources are listed in Table 3 and all options are sufficient to supply either the rotary solenoid or the stepper motor as a power device. Deciding amongst them depends on the situation and direction that Blöndal is heading. The overall simplest direction would be to go for stand-alone batteries as a power source for the automated functions of the filter. The results of equation (7) shows that the energy requirements for a single system is very low in comparison to what, for example, a solar panel system can provide. As the energy requirements and energy consumption from the product will be very low, the payback time between the investment cost and the savings in energy cost is very long.

Connecting the product to the household’s electricity grid have more disadvantages than advantages with the sensitivity and added stress to the system. The results of the energy requirement are also that a small-scale solution should be enough to power the mechanism, and that connecting to the household’s electricity would be overdoing it.

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Going for the stand-alone battery option at first does not exclude future possibilities to add-on the additional components that are necessary for a solar panel system. The solar battery simply takes the place of the stand-alone battery and the product can be developed further.

Out of a sustainability perspective, it is not unlikely that the environmental stress of producing and shipping a solar panel system is greater than the ease of harvesting solar energy into electricity. However, a complete lifecycle analysis of the different options would be necessary in order to verify such a thing. Adding on solar panels and extra complexity also adds on an additional cost in the production stage, which in turn will increase the retail cost of the product, making it less available to the Malaysian population.

The decision between the two different powering mechanisms need further research before any definite decision can be made. In this area there are a lot of loose ends that need tidying up, such as how the transmission is to happen between the motor / solenoid and the shaft, how to integrate and extend the base structure for the mechanism to be covered and secured, and how to program the mechanism to follow the predefined backwash/rinsing schedule.

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Appendix 1

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Appendix 2

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Appendix 3

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Appendix 4

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Appendix 5

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Appendix 6

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Appendix 7

MATLAB Calculations

% MJ146X Bachelor's Thesis

% Author: Oskar Vagero (vagero@kth.se) % Supervisor: Andrew Martin

clc format long %% Constants at T = 273,15K % Atmospherical Pressure Patm = 101325; % [Pa] % Acceleration of Gravity g = 9.81; % [m/s2] % Water's Density rho = 1000; % [kg/m3] % Water's Dynamic viscosity

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%% Operation

% Active for the most time of the lifetime. Area = 0.5*Rshaft^2*(alfa/360); OPLengthInlet = 0.0380; OPLengthOutlet = 0.031; OPVolumeInlet = Area*OPLengthInlet; OPVolumeOutlet = Area*OPLengthOutlet; %% Backwash

% 1-2 minutes long process occuring ~ every 24h BWLengthInlet = 0.04018;

BWLengthOutlet = 0.031;

BWVolumeInlet = Area*BWLengthInlet; BWVolumeOutlet = Area*BWLengthOutlet;

%% Rinse

% 1-2 minutes long process occuring immediately after the backwash % in order to clean out the remaining dirty water of the backwash.

RILengthInlet = 0.0365; RILengthOutlet = 0.1165;

RIVolumeInlet = Area*RILengthInlet; RIVolumeOutlet = Area*RILengthOutlet;

Volumes = [OPVolumeInlet BWVolumeInlet RIVolumeInlet OPVolumeOutlet BWVolumeOutlet RIVolumeOutlet];

%% Friction Force SurfaceArea = pi*DSurface*Length; OperationSurface = OPLengthInlet*pi*DSurface/3 + ... OPLengthOutlet*pi*DSurface/3; BackwashSurface = BWLengthInlet*pi*DSurface/3 + ... BWLengthOutlet*pi*DSurface/3; RinseSurface = RILengthInlet*pi*DSurface/3 + ... RILengthOutlet*pi*DSurface/3;

CutoutSurfaceArea = OperationSurface + BackwashSurface + ... RinseSurface;

FrictionSurface = SurfaceArea - CutoutSurfaceArea; % [m2] DensityShaft = 2712; % [kg/m3] massShaft = 0.190; % [kg] % Moment of Inertia MoIS = ((0.5*massShaft*Rshaft^2)); % [kgm^2] time = 0.1;

angularVelocity = (2*pi/3)/time; % |rad/s] angularAcceleration = angularVelocity/time; % [rad/s^2] Torque1 = MoIS * angularAcceleration

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-46- FrictionCoefficient = 0.8;

%Torque2 = FrictionCoefficient*massShaft*g*Rshaft

% Water flow Torque

a = 0.038; b = 0.015;

P = 100000; % V = sqrt(5)*Q/Area34Inch;

V = sqrt(5)*Q/(a*b); % Maximum pressure [m/s]

F = (rho*(V^2)*(a*b))*-cosd(alfa); Torque3 = F*b

TotalTorque = Torque1 + Torque2 + Torque3 % [Nm] %% Interchange d2 = 0.036; M2 = TotalTorque; d1 = 0.005; i = d2/d1; M1 = M2/i; %% Solid Mechanics

% Calculations on the thin walls between different chapters thickness P = 10; % [bar] P = P*100000; % [Pa] AreaShaft = Dshaft^(2)*pi/12; F = P*AreaShaft; h = 0.002; % [m] % ABS-Plast % [Pa] EModulusABS = 2.1*10^9; SigmaS = 40*10^6; Stress = P*Rshaft/h;

%% Solar Energy Calculations clear all

clc

%% Constants

% H is the annual average solar radiation on tilted panels [kWh/m2] H = 1624; P = H*1000/(365*24); Hday = H/365; %% Rotary Solenoids Time = (4*60)/(3600); U1 = 12; I1 = 1.5; Power1 = 12 PowerRequirement1 = Power1*Time % [Wh] %% Stepper Motor

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% Ryton Lead Acid Battery Load = PowerRequirement1;

Voltage1 = 12; % [V] BatteryCapacity1 = 17; % [Ah] StoredEnergy1 = Voltage1*BatteryCapacity1 % [Wh]

% Yabopower 18650 Li-Io Rechargable Battery Pack Voltage2 = 12; % [V] BatteryCapacity2 = 12; % [Ah] StoredEnergy2 = Voltage2*BatteryCapacity2 % [Wh] %% Solar Panel

% Polycrystalline 10Wp Solar Panel

% https://www.ebay.com/itm/10W-Solar-Panel % -10-20-30A-12v-24v-LCD-Battery-Charger- % Controller-4m-cable/282885297097?var=&hash=item41dd4713c9 WP = 10; % [W] A = 0.380*0.220; % [m2] r = WP/A; % [W/m2]

PR = 0.75; % Default Value [Labouret, Villoz (2010)]

% Annual Energy [kWh]

AnnualEnergy = A * r * H * PR;

% Energy per day [Wh]

SolarPanelEnergy = AnnualEnergy/365 EnergyPrice = 0.516*10^-3; % [RM/Wh] Consumption = PowerRequirement1 TimePeriod = 365; MoneySaved = EnergyPrice*Consumption*TimePeriod

Appendix 8

CAD-files over the new base structure

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Appendix 9

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Automating Residential Water Filters

Automating Residential Water Filters

-3-Abstract

-4-Sammanfattning

Table of Contents

Figures

Tables

Nomenclature

1 Introduction

2 Results and Discussion





3 Conclusion and Future Work

References

Appendix 1

Appendix 2

Appendix 3

Appendix 4

Appendix 5

Appendix 6

Appendix 7

Appendix 8

Appendix 9