BREATHE BRICKS FOR SUSTAINABLE AND ENERGY EFFICIENT HOUSING

Introduction

Nowadays air pollution has become a huge problem at some cities which tends for causes such as global warming, heat island effect. The countries closer to equator have inherited the problem of hotter climates. They receive comparatively lesser rainfall. Many of them are developing countries including Sri Lanka. As a result, buildings that help to reduce this problem are all the range. In past few years though, designers and architects have started to move beyond simply reducing building’s emissions and started to work with techniques that actually remove pollutants from the air. However, in most incidents, these new technologies have been effecting air, chemically or physically by comes into contact with them. 

What if buildings could work a little more like a vacuum cleaner? What if they could take a more effective role in pulling in pollutants from the sky? This was exactly the concept of inspiration behind the developing of Breathing Brick.

Breathe Brick is a masonry system which is designed and constructed to constitute and be a part of ventilation system of buildings. It filters polluted outdoor air so that it becomes healthy enough to bring directly into occupied spaces. It acts as a pollution absorbing brick where the design is very similar to a vacuum. The pollution vacuums in bricks were developed by assistant professor Carmen Treadle at Cal Poly College of Architecture and Environmental design. The brief brick sucks pollutants in the air and releases filtered air. The innovative material is designed to be a part of a building standard violation system. In short, it is a technology that can be easily applied to the current construction process by performing wind tunnel tests.

Product / Material

The Breathing Brick is designed to form a part of a building’s regular ventilation system, with a doubled-layered facade of the specialist bricks on the outside, complemented by a standard internal layer providing insulation. At the center of the Breathing Brick’s function is cyclone filtration, an idea borrowed from modern vacuum cleaners, which separates out the heavy pollutant particles from the air and drops them into a removable hopper at the base of the wall.

The system is composed of two key parts: Concrete bricks and Recycled plastic coupler. 

1. Concrete Bricks

Breathe Brick unit is a structural masonry component within which is embedded with a cyclone filter. The concrete brick is featured with a faceted surface which helps to direct airflow into the system, and a separate cavity for inserting steel structure. The brick is designed in a way that it can be replaced some exterior.

2. Recycled Plastic Coupler

It helps to create a path from outside into the brick’s hollow center and to align bricks.

It has a two layer facade system with the specialist bricks on the outside and standard insulation on the inside in the center is a cyclone filtration system that separates out the heavy air particles from the air and collects them in a removable hopper.

How “Breathe Brick” Wall Operates?

By the help of the faceted surface of the Breathe Brick, the air outside the structure is directed into rectangular inlet ports. The air that comes into the system is spinned by cyclone filter winnowing out particles.

The cyclone filter is cast directly into the concrete form. The filtered air that passes into the cavity of the double-Wythe wall system could then supply an HVAC system or an adjacent interior space directly. (Breathe Bricks – Operation Mechanism, Applications, Advantages (online))

The Breathing Brick can function with both mechanical and passive ventilation systems, as the brick simply delivers filtered air into the wall plenum; this air can be delivered to the building interior through mechanical equipment or through trickle vents driven by passive systems such as stack ventilation.

Importance as a sustainable product

• Cheap.

• Sustainable.

   Breathe Brick is a clever way of taking the heavy particulates out of the air as a byproduct of making a building

• Environmentally friendly.

• Low Embodied Energy.

• Ease of handling and construction.

• Low Carbon construction. (using of natural construction material)

• Lightweight. (Technique for modification of breathe brick)   

 By replacing sand in concrete by EPS, the brick can be formed into a lightweight brick. Discussed further under Physical properties of Breathe Brick.

• Help to improve thermal comfort.

• Energy efficient.  Since it operates without electricity and makes part of ventilation system. It works with pressure and temperature differentials

• Passively filter outdoor air prior to introduction to an indoor environment.

• Can operate through existing HVAC system or passive as independent system.

• The design of breath bricks can be configured in a wall with window and the cooling system as well.

• It was proven that the system can filter 30% fine particle pollutants and 100% course particles such as dust.

In wind tunnel tests, the system was found to filter 30% of fine aggregates such as airborne pollutants and 100% of course aggregates such as dust. As the entire system is relatively expansive, the Trudell posits the Breathing Brick is a way to lower the pollution level in developing countries, where rapid expansion of industry and less stringent environmental regulations often cause problems. (Rory Stott, www.archdaily.com)

Applications

• Breathe Brick is optimal for one or two story structures in areas with poor air quality.

• It can be used to construct exterior walls (plenum or courtyard, sound walls along freeways, school playground enclosures)

• It is specifically designed for regions with elevated outdoor particulate matter.

Physical properties of Breathe Brick

“Breathing Walls” concept is an innovative construction procedure that can help improve thermal comfort in houses utilizing local materials.

Breathe brick is made up of concrete and plastic couplers made from recycled plastic. The concrete part can be made out of user’s choice. As a technique the brick can be constructed to have light weighted characteristic.  By the introduction of expanded Polystyrene (EPS) which is a replacement for sand, the brick is lightweight and contains various properties of strength and water absorption. EPS has been frequently used in construction industry in production of lightweight building materials such as wall panel and lightweight concrete blocks. Replacement of sand by EPS is based on volume. The replacement percentage of EPS was 0%, 20%, 30%, 40% and 50%. 

Based on experimented results, the density and compressive strength of the brick was decreased as the percentage of the replacement increased. Meanwhile for water absorption properties, it was found that water absorption of the brick was decreased as the percentage of EPS increased. However the properties obtained have been satisfied the requirement where the brick density for lightweight should be less than 1680kg/m3. The strength of load bearing and non-load bearing brick is 11.7MPa and 3.45MPa for each individual unit. Meanwhile, for water absorption, the percentage of water absorption of brick should be less than 12%. From researches it was found that replacement of sand by EPS give significant impact towards strength and water absorption performance of concrete. 

Unfortunately the strength is limited to one or two story buildings. The strength limitation is the major weakness in lightweight breathing brick. But it is more suitable for houses in Sri Lanka.

E. Dilmi D.Z. Abeysekera

Department of Civil Engineering

University of Sri Jayewardenepura  

REFERENCES

• Admin, (17 December  2017), Breathe Brick (online) [Accessed on 25/09/2019],Available at : http://transmaterial.net/breathe-brick

• Madeh Izat Hamakareem, Breathe Bricks – Operation Mechanism, Applications, Advantages (online) [Accessed on 24/09/2019], Available at: https://theconstructor.org/building/breathe-bricks/29216/

• Rory Stott, (12 August  2015), This Innovative Brick Sucks Pollution From the Air Like a Vacuum Cleaner (online) [Accessed on 25 September 2019],Available at: https://www.archdaily.com/771767/this-innovative-brick-sucks-pollution-fromthe-air-like-a-vacuum-cleaner

· 

CIGARETTE BUTT BRICKS AS A SUSTAINABLE CONSTRUCTION MATERIAL FOR SRI LANKA

Cigarette butts

Global warming and the environment pollution are critical issues which occur due to the development activities in the world. Cigarettes also contribute to the environmental pollution mainly not in a direct way, but due to the improper disposal of the remaining part of the cigarette after it is used. Since cigarette butts are made of cellulose acetate (a plastic) [5] they have poor biodegradability and it will take many years to breakdown and also heavy metals such as Arsenic (As), Chromium (Cr), Nickel (Ni), and Cadmium (Cd) which are trapped in the cigarette filters leach into the soil and waterways during that process [4].

Figure 01: prepared cigarette butt for brick production [1]

Companies produce about 6 trillion of cigarettes every year and smokers help to make over 1200 million kilograms of cigarette butts waste. In Sri Lanka tobacco use costs LKR 214 billion per year (according to the statistics of 2018) in economic loss with substantial human development losses [6]. Dr.Abbas Mohajerani who led the research project about the cigarette butt bricks at RMIT University said that these numbers can be increased by more than 50% by 2025 mainly due to an increase in world population .Their research results show that if 2.5% of worlds’ brick production with the addition of 1% of cigarette butt amount can be lead to completely offset the annual worldwide cigarette butt production [4].

Figure 02 : Trend of smoking in Sri Lanka in Last 10 years by age groups (2009-2018) [6]

Figure 03 : Dr. Abbas Mohajerani [4]

Advantages of Cigarette butt bricks

Conventional fired clay bricks are one of the most common construction materials since the initial ages of the building construction due to their durability, compressive strength, flexural strength and thermal conductivity than other construction materials. Most of the research activities have proved that incorporation of cigarette butts has significant advantages on behalf of construction industry and also a solution for the environmental pollution. Nowadays, engineers and architects encounter some problems such as the thermal comfort and the noise insulation of dwelling areas of buildings. Since they have invented some solutions such as cooling bricks, ventilation systems and alternative materials for concrete and bricks. Since the cigarette butts have good insulation capability, addition of them into bricks reduce household cooling and heating demands [1]. Cigarette butts cause to improve the noise insulation because they improve the porosity of the bricks than the conventional bricks. In addition to that bricks with CBs (cigarette butts) are lighter and cost effective rather than using other raw materials for manufacturing bricks and cuts the energy needed to fire bricks by up to 58% and that leads to reduce the embodied energy [1]. Since the density of the filters are less than the other materials which are used in the bricks production the overall density was reduced up to 30% [3], depending on the percentage of cigarette butts [4]. Durability of these bricks can be increased with the addition of filters because their biodegradability is less than other raw materials which are used in production.

Physical properties of cigarette butt bricks

Cigarette butts have the physical properties as follows,

• Bulk density – 1.80 𝐠𝐜𝐦−𝟑

• Apparent porosity – 30 %vol.

• Apparent density – 2.42 𝐠𝐜𝐦−𝟑

• Water absorption – 16.65 %wt.

Some of the above mentioned properties of cigarette butt bricks such as density are less than other raw materials while properties like water absorption are higher because most of times the filters consist of tobacco residue, sawdust and grass. Therefore, the water absorption of the bricks increases linearly with the increase of cigarette butt content [1].

Figure 04 : Test cigarette butt bricks with different replacement of Cigarette butts [1]

Physical and mechanical properties of cigarette butt bricks were tested with different percentages of CBs (2.5%, 5%, 7.5%, and 10% by weight) and with the three different mixing times to distinguish the results compared to the conventional clay bricks. In 10% CB bricks the dry density was decreased up to 30% and the compressive strength decreased by 88% and the compressive strength of bricks with 1% CB was determined as 19.53 MPa [2] and this is a suitable value for a one or two storey buildings. Influence of the mixing time was observed by using three different times (5, 10 and 15 minutes) for the bricks with 7.5% CB and 15 minutes brick shows 114% increment of strength and 12% increment for density compared to 5 minutes mixing time [7]. Although the values of water absorption, initial rate of absorption and tensile strength decreased by 22%, 29% and 5% respectively.

As a sustainable solution

Heavy metals and other pollutants which are trapped and immobilized in the solid block when the bricks are fired and they cannot leach and mix with the soil and waterways anymore. In addition to that this is a cost effective product because the cigarette butts are very common in our surrounding and it can be supplied without any cost. Therefore, this can be a turning point of construction industry of Sri Lanka as a developing country.

E.M.K.G.A.D.B.Ekanayake

Department of Civil Engineering

Faculty of Engineering

University of Sri Jayewardenepura.

References

1)    Guide, B. and Masonry, B., 2020. Cigarette Butt Bricks - Physical Properties And    Advantages. [online] The Constructor. Available at: <https://theconstructor.org/building/cigarette-butt-bricks/29224/> [Accessed 19 May 2020].

2)      2020. [online] Available at: <https://www.researchgate.net/publication/297892222_A_practical_proposal_for_solving_the_world's_cigarette_butt_problem_Recycling_in_fired_clay_bricks> [Accessed 19 May 2020].

3)    2020. [online] Available at: <https://www.researchgate.net/publication/279577246_Recycling_cigarette_butts_in_lightweight_fired_clay_bricks> [Accessed 19 May 2020].

4)    Engineersaustralia.org.au. 2020. Double Advantage To Using Cigarette Butts To Make Bricks | Engineers Australia. [online] Available at: <https://www.engineersaustralia.org.au/News/double-advantage-using-cigarette-butts-make-bricks> [Accessed 19 May 2020].

 5)    Longwood.edu. 2020. Cigarette Litter --Filters. [online] Available at: <http://www.longwood.edu/cleanva/cigbuttfilters.htm> [Accessed 19 May 2020].

6)    Tobaccounmasked.lk. 2020. Tobacco Industry Country Profile – Sri Lanka - Tobaccounmasked. [online] Available at: <http://www.tobaccounmasked.lk/index.php/Tobacco_Industry_Country_Profile_%E2%80%93_Sri_Lanka> [Accessed 19 May 2020].

 7)    2020. [online] Available at: <https://www.researchgate.net/publication/272599892_Properties_Improvement_Of_Fired_Clay_Bricks_Incorporating_With_Cigarette_Butts> [Accessed 19 May 2020].

AURA VIA GADGETS

EPISODE -02 click here

EPISODE 03

He stepped towards the clock and looked at it for a while with no blinking. He started to feel an itching on his right eye and suddenly remembered a thing his grandma has said that itching on right eyes occur when the negative energy field disturbs our Aura. Then he trembled because of the sudden fear popped up inside him a few minutes ago. Ravin screamed louder when Sethu tapped on his shoulders and he tried to exile the fear formed in him. Sethu couldn`t understand anything happened there at that time but he could do only one thing and that was consoling Ravin. Unable of doing anything else that night, he went to bed. He was still confused by the things happened, but he didn`t figure out the exact reason for Ravin’s screaming because he knew that Ravin is a brave person amongst all his peers. Whatever happens, all they needed is the rest. Already it was late to sleep. A little later, both the lights and their eyelids went off peacefully. 

Sethu got up in the dawn, but still he was in bed. His mind was chewing all the consequent events happening at his home nowadays. He decided to send his daughter Meera to a convent school where she can live safely forever till Sethu completes his next research with his friend. A few hours later, he convinced his daughter to stay at the convent ‘till he returns from abroad’. “Sometimes a lie can save our lives too”, he mummed. His plans and arrangements were all done well with the blessing of Christ, but he left the convent with a huge guilt in his heart. A drop of tear shed and made him move away.

On his way home, many doubts arose in his mind about demons and their negative effects on others. Sethu was so keen to learn about the soul science further with the help of an expert in psychiatric science. He planned to postpone the researches on the pendulum clock as it relates to the result of his new originated thoughts about demons. His clear decision about this new idea leads him to talk to his senior mentor, Mr. Adithya who is a retired professor of physics.

He disagreed with him at the start, but he consented after an hour of lecture about science of the soul and its depth. Sethu was warned by his mentor strictly like never before, as it deals with the lives and human nature. He knew that this was more dangerous than the material science all over the world. He really needed to fill the void of grief in his heart instigated when his wife left him, but there was no other choice. He found his way to the destination, but not the destination itself. He would have to do it himself; otherwise others would hire him to fulfill their voids and dreams. He thought that nobody should let others hire them. The car reached home in the speed of light.

Sethu and Ravin had an argument on this new turn of events. Ravin couldn’t tolerate any of Sethu’s ideas and he refused the company of Sethu. Guilts and loneliness chased him as much as they could and he too went along with all of the odd things that followed. He devoted two and a half years in the science of the soul as a bookaholic only yet. Still there was no any progress in practice. Then, he thought of investigating the soul leaving process from a body. For this, he approached a psychiatrist who works in a general hospital for long, as he wanted to look up and move along with all sectors of that hospital. It was risky in the start, but soon he got some opportunities to continue with his researches easily.

Initially he worked as a caretaker to the patients during both day and nights. He could make contact with the patients who suffered from long term diseases as he knew that they can be an asset to his study. His days and nights passed on to patients. After a long time, he did share some love and kind with outer people for the first time in his life. Step by step he moved into the administrative sectors and got the necessary aids for his study. He read many reports about the deaths occurred here and the causes for them. He investigated an important data that shook him like never before. Suddenly he knelt down and prayed. Out of the blue, he felt a sudden tap on his shoulder and he was ready to hear the most precious thing that was going to turn his life upside down…..

To be continued...

Story by:

L.Pirashanthiyah

Department of Electrical Engineering

Faculty of Engineering, University of Moratuwa

Artist:

Achini Fonseka

Department of Textile and clothing technology,
Faculty of Engineering, University of Moratuwa

OZONE LAYER AND INFLUENCE OF COVID-19

Ozone layer, which is also known as ozonosphere can be found in the lower portion of the stratosphere that is 15-35 km above from the Earth. This layer consists of higher concentration of ozone. 90% of ozone in atmosphere presents in the stratosphere and it is referred as the ozone layer [1]. The thickness of the layer varies seasonally and geographically. As an example, ozone layer is thin near the poles. Ozone layer absorbs most of the ultra violet rays (UV rays) including 97-99% [2] of Sun’s medium frequency UV light. In addition, the layer absorbs solar radiations of wave lengths less than 290 nm and some other harmful forms of radiation. Due to the absorption of the solar radiation by the ozone layer, the temperature of the stratosphere is significantly high.   

Figure 01: The position of ozone layer in the atmosphere [3]

The ozone layer was discovered by the French scientists Charles Fabry and Henri Buisson in 1913.

Production of ozone in stratosphere

At the lower portion of stratosphere, chemical bonds of the oxygen molecules (O₂) break due to high energy solar photons. This phenomenon cause to occur single oxygen atoms.

O₂ + UV => O + O

Then these single atoms combine with remaining oxygen molecules and form ozone (O₃).

O+ O₂ => O₃

Most of the ozone in the stratosphere formed where the solar radiation level is high (equatorial belt).

Depletion of ozone layer

Now, the depletion of the ozone layer is becoming a global problem. It is due to the emission of manufactured chemicals mainly CFC gases (Chlorofluorocarbon) and halons. This problem was firstly described in a paper published by a Dutch Chemist Paul Crutzen in 1969. In his researches it was shown that the depletion was done by nitrogen oxides. Later in 1974, American chemists Mario Molina and F. Sherwood Rowland discovered that the ozone layer is mainly depleted by CFC [4]. CFC and halon cause chemical reactions to break the ozone molecules. It causes to reduce the solar radiation absorbing capacity of ozone layer. CFC is mainly released by the applications such as air-conditioning, refrigeration, blowing agents in foams etc. Halons released by the applications such as combustion.

Figure 02: Ozone depletion process [5]

The high emission of those ozone depleting substances by human cause to occur holes in the ozone layer. For the past few decades, the chemical reaction with the involvement of Chlorine and Bromine, cause the ozone layer deplete rapidly. Ozone depletion is greatly happened in South Pole. This depleted area is known as the ozone hole. This ozone hole was occurred in the spring over Antarctica.

Figure 03: ozone hole [6]

This ozone hole was grown for years. Though the maximum size of the ozone hole is decreasing as shown in the figure below.

Figure 04: Maximum ozone hole area [7]

Ozone depletion cause to have cancer risks (i.e.: skin cancer), eye damages (i.e.: permanent blindness, cataracts), sunburn, etc. [8]

How to protect ozone layer?

By avoiding the processes of emission of the manufactured gases such as CFC and halon, the ozone layer depletion can be reduced. As an example, minimizing the usage of motor vehicles reduce the halon percentage of atmosphere. Maintenance of air-conditioners properly or reducing the usage of air-conditioners can reduce the percentage of CFC in atmosphere. The global authorities (i.e.: The Montreal Protocol) also have taken some legal actions to protect ozone layer by banning the damaging chemicals [9]. And also, it was designated “September 16” as the international day for the preservation of the ozone layer.

Due to the lockdowns in most countries, for COVID-19, it has led to a significant reduction of air pollution due to the limited operation of industries as well as the motor vehicles. Nitrogen Dioxide dropped up to 60% in northern China, Western Europe and the U.S. in 2020 compared to 2019 [10]. And also, particulate matter pollution has gone down by 35% over northern China [10].  The reduction of the emission of CFC gases and halon in these days also likely protecting the ozone layer. Though, the reduction of air pollution due to lockdown is not the reason to close the ozone hole [11]. Main reasons are polar vortex, high-altitude currents that are responsible for bringing cold air to polar regions [11].

Polar vortex is a large area of low pressure and cold air surround the Earth poles. This effect is decreasing during summer season. Polar vortex is typically weaker in the Arctic region due to the presence of nearby land and the mountain ranges that disturb the weather. In this season, the ozone layer is healing mainly due to the unusual strong and long-lived polar vortex, and it is not mainly due to the air quality changes [12]

D.M.T.S. Rathnayake,

Faculty of Engineering,

University of Sri Jayewardenepura.

References

[1]	D. Wuebbles, "ozone layer, Atmosheric science," BRITANNICA, 17 April 2020. [Online]. Available: https://www.britannica.com/science/ozone-layer. [Accessed 14 May 2020].
[2]	B. Sparling, "The Ozone Layer," NASA Official, 30 May 2001. [Online]. Available: https://www.nas.nasa.gov/About/Education/Ozone/ozonelayer.html. [Accessed 14 May 2020].
[3]	"Biology Review of the Ozone Hole and Global Warming," School Tutoring Academy, 28 June 2015. [Online]. Available: https://schooltutoring.com/help/biology-review-of-the-ozone-hole-and-global-warming/. [Accessed 14 May 2020].
[4]	D. Wuebbles, "Ozone layer atmospheric science," BRITANNICA, 17 April 2020. [Online]. Available: https://www.britannica.com/science/ozone-layer. [Accessed 15 May 2020].
[5]	"What is Ozone Depletion?," eSchool Today, [Online]. Available: eschooltoday.com/ozone-depletion/what-is-ozone-depletion.html. [Accessed 14 May 2020].
[6]	E. Gray and T. Stein, "2019 Ozone Hole is the Smallest on Record Since Its Discovery," NASA TV, 21 October 2019. [Online]. Available: https://www.nasa.gov/feature/goddard/2019/2019-ozone-hole-is-the-smallest-on-record-since-its-discovery. [Accessed 14 May 2020].
[7]	EU, "Protection of the ozone layer," European Commission, [Online]. Available: https://ec.europa.eu/clima/policies/ozone_en. [Accessed 14 May 2020].

AURA VIA GADGETS

EPISODE -01 click here

EPISODE 02

Unimagined things happened day by day at home. He couldn’t distinguish them from the earlier one, but kept a watchful eye on them. His days passed in a rush to get the legal approval for his invention from the International Court for intellectual matters. They approved it with legal rules and regulations after reviewing the design by some related professionals.

He wished to celebrate this great success with his peers and relations. Everything went well as the way he expected, but the unexpected chiming he heard the other night kept ringing inside him. So many questions and doubts rose in his mind, but none of them were answered in anyway. Sethu was quite frustrated about the things happening at home. Of course, he collected the history of his house and the land to get a clear idea of the nature of his house. Anyway, he couldn’t find anything wrong with the house also.

Meera came to him and suddenly asked about angels and demons. She asked him more about distinguishing them separately. Now the dad was also confused, but managed to make up some answers for the questions that he didn’t even know answer for. Actually, he didn’t have any idea either about angels or demons. Then he answered his daughter while she was sitting on his lap. “Darling, your mother is a charm angel now. She is a soul filled with full of well-wishing thought” with a sigh of thinking his old and lovely days. He held his sorrow and tears back behind his amazing smile as always. ‘Every one of this world nowadays lives as same as me’ he murmured to himself.

Now, Meera put a question to him “Dad, What about demons? Are they opposite to angels?” He sank in his wife’s memories while she was asking this and couldn`t return back immediately. His daughter repeated. He replied to her, agreeing about demons saying “of course. They are opposite to angels and always disturb others as their souls are filled with bad thoughts” Meera listened to him carefully. Her father couldn’t understand why his daughter was in so much eager to know such things. Their day went finely.

He disliked stopping working with his peers. So, he called Ravi, one of his friends in private the next day. Their conversation was about the next research on how the thoughts of souls affect the aura, in a living body which causes their transformation into angels and demons later. His friend had neither an idea, nor the knowledge about Human Science. Although disagreed earlier, he convinced himself to help Sethu in all other ways. He had a doubt on his friend and did ask directly too. Still, Ravi was confused about why his friend Sethu turned his field into a human science. Sethu humbly and simply replied “soul is everything which generates both constructive and destructive energies all over the universe”. Ravi sighed after listening carefully. Sethu twisted Ravi by pointing his pendulum clock and said “You know Ravi, this clock chimes only once at midnight, though it’s a ticking one. We are going to work on it from this midnight.” Ravi didn’t get him, but he looked at him with an awkward broadened forehead …….

Again, they waited in the yard under the starred night sky with glasses of red wine. It was 11.45 pm. Suddenly Ravi felt the rough walk of a dark man by his side towards the clock. He also stood up holding the wine glass……

           

To be continued...

   

Story by:

L.Pirashanthiyah

Department of Electrical Engineering

Faculty of Engineering, University of Moratuwa

Artist:

Achini Fonseka

Department of Textile and clothing technology,
Faculty of Engineering, University of Moratuwa

SCADA FOR POWER SYSTEM OPERATION, AUTOMATION AND SECURITY

Currently, electricity in the sense is one of the basic necessity for the smooth functioning of day to day life of the world. Thus, continuity supply of electrical energy to the consumers is a must and it is irrespective of the operating conditions of the power system to which the consumers are connected. Power systems, being the largest and the most complex dynamic systems [1] are often exposed to numerous physical disturbances and resulted in the conditions of instability. 

Stability of a power system

The ability of a power system to retain in its state of operation in equilibrium after being subjected to physical disturbances is known as the stability of a power system. [1]

1. Rotor angle stability; defines the ability of maintaining synchronism through torque balance of a synchronous machine. [1]
2. Frequency stability; defines the ability of maintaining the frequency in a specified range according to the demand and generated active power balance. [1]
3. Voltage stability; defines the ability of maintaining steady acceptable voltage through reactive power balance. [1]

Reliability of a power system

To ensure the continuity of supply, the power system must be designed so as to resist any disturbance. (E.g.; short circuit followed by a line tripping, tripping of any element without a fault etc.) [1]

The reliability of a power system is, its potentiality of delivering an uninterrupted power supply to any consumer maintaining the quality standards, and according to the demanded amount, during normal conditions as well as the disturbed conditions. The degree of Reliability is measured by the frequency, duration and magnitude of adverse effect on consumer service. [1]

Security of a power system

The power system security can be defined as the ability to resist any kind of disturbance without interruption to the power supply service. [1]

A power system is said to be fully reliable if it is secure all the time. [1]

Security of a power system has two aspects.

1. Physical security; refers to the operation at normal parameters of the primary and secondary circuits of an electrical network on one side and generator and loads on the other side. [1]
2. Cyber security; refers to the precise operation of the cyber system. (Cyber system includes, all the computer communication and digital control devices installed in control centers, power plants and in substations.) [1],[2]

TCP / IP (Transmission Control Protocol/Internet Protocol) based cyber infrastructure has been developed and broaden significantly in the previous decade. However, the main infrastructure which we used today in power systems is the SCADA. [1]

Figure 1: SCADA in distribution network. (Picture courtesy: www.electricaltechnology.org)

SCADA- Supervisory Control and Data Acquisition

SCADA, is a large scale control system utilized in automated industrial processes. (E.g.: Power systems, steel manufacturing, municipal water supplies and etc.) Such a system is heavily capable of monitoring and controlling those processes, in real time by acquiring data from sensors at a remote station and then transferring it to a central computer system or the host that manages the operations using that information. [3]

          Components of a typical SCADA system; [4]

1. Remote Terminal Units (RTUs)- Real time PLCs (Programmable logic controls ),
2. Master Terminal Units (MTUs)- Central Host/ SCADA center
3. Communication System- Cable, radio, satellite, telephone (PABX)
4. Computer Workstations-HMI, Human Machine Interface.

Figure 2: Components of a SCADA system. (Picture courtesy: www.electricaltechnology.org)

SCADA in Automation of the Power System

Figure 3: Automation of a power system at a glance. (Picture courtesy: www.electricaltechnology.org )

Role of the SCADA in automation of a power system is outstanding. At generating stations, it does a major role to control the input flow rate to the turbine and at every time it monitors the speed and the frequency. Also it detects the current flow and line voltages and monitors the circuit breakers. [5]

SCADA system is the foundation of the concept of Smart grid. The SCADA upgrades the performance and efficiency of the entire power system by providing the special features like real time monitoring, coordinating, controlling and operating, data trending & logging, maintaining desired voltages, current and power factor, generating alarms and etc. This eliminates the need for site visit for personnel inspection at many cases. Remote Terminal Units (RTUs) are used to perform the automatic monitoring task, protecting and controlling of various equipment.  [4]

The major functions of SCADA can be categorized into following types.  [4]

1. Substation Control
2. Feeder Control
3. End User Load Control

Substation Automation Systems (SAS) using SCADA

Operations performed; [4]

●       Bus voltage control

●       Bus load balancing

●       Circulating current control

●       Over current protection

●       Transformer thermal, earth leakage and differential protection

●       Bus earth leakage and differential protection

●       Line earth leakage, distance and differential protection

●       Gas Insulated Substation (GIS) distance control and monitoring

●       Continuous monitoring of the status of equipment

●       Collection of historical data of the substation

●       Alarm generation during electrical accidents and faults.

Process; [4]

1. Input/output (I/O) modules gather field parameters data.
• Status of switches, circuit breakers, transformers, capacitors and batteries
• Voltage and current magnitudes
2. RTUs collect I/O data and transfer to the master unit (central computer system) via network interface module.
3. The master unit receives and logs the data.
4. The master unit displays data on HMI, Human Machine Interface and generate control actions.

This master unit also responsible for generating trend analysis, centralized alarming, and reporting.  [4]

Figure 4: Substation control using SCADA (Picture courtesy: www.electricaltechnology.org)  

Advantage:

●       Enhance the reliability of the network and minimizes the failures with high speed transfer of data and control commands. [4]

Feeder Control using SCADA

Operations performed; [4]

●     Feeder voltage (VAR) control: - voltage regulation and capacitor placement operations.

●     Feeder automatic switching: -

o   remote switching of feeders

o   detection of faults

o   identifying fault location

o   isolating operation

o   restoration of service

Further, it provides the facility to gather historical data of feeder parameters and their status.  [4]

Figure 5: Feeder automation using SCADA (Picture Courtesy: www.electricaltechnology.org)

Feeders (underground and overhead networks) are automated through modular and integrated equipment to reduce the duration of the failures and number of failures as well. Measures can be taken to reduce the repeatability of the fault.

Ring main units and Remote Control Units (RTUs) of underground and overhead network are responsible for maintenance and operation tasks, such as remote load switching, capacitor bank insertion and voltage regulation. The entire network is connected to the communication medium to facilitate remote energy management at the central monitoring station.  [4]

End User Load Control using SCADA

Operations performed; (User end side) [4]

●       Remote load control

●       Automatic meter reading and billing

Figure 6: Centralized meter data-management system using SCADA (Picture courtesy: www.electicaltechnology.org)

Process; [4]

1. Smart meters extract the energy consumption data and store those in a local storage unit as well as transfer to central control.
2. At the central control room, AMR (Automated Meter Reading) control unit automatically fetches, stores and converts all meter data.

Modems at each meter ensure the secure two-way communication between the central control room and remote sites.  [4]

Advantage of the Centralized data management system using SCADA;

●      Easy and cost effective method for automating the energy meter data and billing.  [4]

Advantages of implementing SCADA for power systems as a whole

●     SCADA systems are equipped to make immediate corrections in the operational system, so they can increase the life-period of the equipment and save on the need for costly repairs.  [4]

●     Equipment damages can be avoided as timely fault identification is done.

●     Minimization of labor cost due to less human introversion as the system is automated.

●    The auto-generated reporting system ensures compliance with regulatory principles.  [4]

●    Automatically improvement of the voltage profile by power factor correction through VAR control.  [4]

●    Improves the reliability, security so the continuity of supply.  [4]

References

[1]	Venkata, S.s and Eremia, Mircea and Toma, Lucian, "Background of Power System Stability," Handbook of Electrical Power System Dynamics: Modeling, Stability, and Control, pp. 453-475, 2013.
[2]	E. G.N, "Cyber Security and Power System Communication," Essential Parts of a Smart Grid Infrastructure, IEEE Trans. on Power Delivery, vol. 25, no. 3, p. 1501–1507, 2010.
[3]	V. Beal, "SCADA - supervisory control and data acquisition," webopedia, 2020. [Online]. Available: https://www.webopedia.com/TERM/S/SCADA.html. [Accessed 03 May 2020].
[4]	E. Technology, "SCADA Systems for Electrical Distribution," ELECTRICAL TECHNOLOGY, 2018. [Online]. Available: https://www.electricaltechnology.org/2015/09/scada-systems-for-electrical-distribution.html. [Accessed 3 May 2020].
[5]	Introduction to SCADA System | Supervisory Control and Data Acquisition System. [Film]. USA: Automation design and development, 2017.

Nipuni Anuththara Herath

Department of Electrical and Electronic Engineering

Faculty of Engineering

University of Sri Jayewardenepura