Hidrofor sistemlerinde kontrol mekanizmasıyla enerji tasarrufu
Energy saving with control mechanism in hydrophor system
Yazar: EREN YILDIZ
Danışman: DOÇ. DR. OSMAN KAAN EROL
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Kontrol ve Otomasyon Mühendisliği Ana Bilim Dalı / Kontrol ve Otomasyon Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2021
Konu: Elektrik ve Elektronik Mühendisliği = Electrical and Electronics Engineering
Dizin: Enerji tasarrufu = Energy saving ; Hidrofor = Hydrophore ; Kayan kipli denetim = Sliding mode control ; Santrifüj pompalar = Centrifugal pumps ; Su pompası = Water pump

Özet:
Günümüzün en önemli araştırma konularından biri enerji kaynaklarının verimli kullanılmasıdır. Hidrofor sistemleri su iletimi için en çok kullanılan sistemlerden biridir. Bu nedenle günlük hayatta harcanan enerjinin azımsanmayacak bir miktarı hidrofor sistemlerinde harcanmaktadır. Hidrofor sistemlerinden yapılacak bir verimlilik çalışması pek çok alandaki enerji tüketimine etki edecektir ve sürdürülebilirlik açısından faydalı olacaktır. Hidrofor sistemleri içerisindeki esas enerji tüketim birimi pompadır. Bu sebeple bu çalışmada pompa üzerinden bir tasarruf sağlanması hedeflenmiştir. 
Literatür taramasında incelenen her bir metodun çeşitli dezavantajları bulunmaktadır. Bu çalışmada mevcut metotların yanı sıra pompa kontrolcüsünde verimlilik sağlayacak bir algoritma araştırılmıştır. Bu çalışmada önerilen algoritma kayan kipli kontrolün bir versiyonu olarak değerlendirilebilir. Sistem basıncı referans basınç değerinin üstünde iken on-off kontrolün kapalı durumu gibi çalışırken, sistem basıncı referans basıncın altına düştüğünde PID kontrolcü gibi çalışmaktadır. Buna ek olarak enerji tasarrufunu arttırmak için ekonomi indeks adında yeni bir parametre tanımlanmıştır. Ekonomi indeks eklenen sistemde, pompanın durma koşulu değişmez iken pompanın çalışmaya başlama noktası referans basınç ile ekonomi indeksin çarpımı olan noktaya kayar. Böylece sistemlerde düşük su talebi veya sızıntı olması halinde pompanın art arda çalışıp durması sebebiyle oluşacak enerji kaybı ve pompanın fiziksel olarak zarar görmesi durumları ortadan kalkacaktır.
Sistemde sağlanacak faydanın analizi için simülasyon çalışması yapılmıştır. Simülasyon çalışması üç farklı senaryo ile gerçekleştirilmiştir. İlk senaryoda su talebi sabit tutulurken ekonomi indeks değeri değiştirilmiş ve ekonomi indeksin enerji tasarrufu üzerindeki etkisi araştırılmıştır. İkinci senaryoda ise ekonomi indeks değer sabit tutulurken su talebi değiştirilmiştir ve ekonomi indeks parametresinin farklı su talepleri görülen sistemlerde tasarruf sağlayıp sağlamadığı kontrol edilmiştir. Son olarak günlük su talebi modellenmiş ve parametrenin günlük kullanımda ne kadar tasarruf sağlayabileceği analiz edilmiştir.
Yapılan testler sonucunda ilk senaryoda yaklaşık yüzde 80 enerji tasarrufu sağlanabildiği görülmüştür. İkinci senaryonun sonucu olarak ekonomi indeksin yüksek su taleplerinde enerji tasarrufu sağlayamadığı görülmüştür. Son senaryoda ise yüzde 40 enerji tasarrufu sağlandığı gözlemlenmiştir.
Bu çalışmada önerilen algoritma verimliliğin yanı sıra pompa ömrünü de gözetmektedir. Bu sayede enerji verimliliğin yanı sıra kaynak kullanımında da iyileşme sağlanması hedeflenmiştir.

Abstract:
Efficient use of energy resources is crucial today. While the energy consumption is getting higher, the sources are faced to run out. Hydrophore systems are one of the most frequently used systems for water transmission. A considerable amount of energy spent in daily life is being used in hydrophore systems. Those systems have a usage share of 2-3 percent of the energy produced in a year overall the world. It is apparent that a possible efficiency improvement on hydrophore systems affects energy consumption in many areas and that would be very beneficial in terms of sustainability. 
In this study, firstly, the structure of hydrophore system is examined. The elements having high importance in the structure of the hydrophore system are discussed one by one. The elements discussed int this study are tank, controller, pump, and manometer. In a complex hydrophore system, number and variety of the elements can be changing according to purpose of the usage.
The role of each element in the system has been investigated in detail. This examination aims to point out the parts where the highest energy saving amount can be provided. In the light of the investigations, pump is appeared to consume most of the energy in the system. Therefore, pump is determined as the part which has the highest energy saving opportunity. 
According to the literature revived, centrifugal pumps are being used in hydrophore systems commonly. Thus, centrifugal pump design and structure have been researched and main points to consider in controller design has been determined.
After the preliminary research of hydrophore structure and pump design, existing energy saving methods are discussed. The discussed methods are variable speed pump control, on-off control, and parallel pumps usage. Besides saving energy, these methods have some certain drawbacks. These methods shorten the pump life and fail to save energy in general. 
In variable speed pump control, the pump continues to run at a very low speed even when there is no water demand and that working method creates a continuous energy consumption. The energy is wasted when there is no water demand. In addition to this energy loss, continuously working pump is being exposed physical damage. 
In on-off control mechanisms the pump stops and starts too long due to instability occurs at low water demands. Each restart causes extra energy consumption and physically damage the pump which are obvious disadvantages of that method. 
Parallel pump usage is a method combines on-off control mechanism and variable speed pump usage Thus, the abovementioned disadvantages are also valid for this method. Details of those shortcomings are explained in the study thorough. 
After the literature researches, a new control algorithm is developed in this study. The algorithm can be considered as a version of sliding mode control. Sliding mode control consists of a set of subsystems that are supported by suitable switching logic formed by continuous control functions. 
Working mechanism of the sliding mode control, as applied in the hydrophore system is also discussed in the study. When the hydrophore system pressure rises above a reference value, the sliding mode control operates as an on-off control and turn off the system. When the system pressure falls below the reference value, pump operates, and the operation will be controlled by the PID controller. 
Furthermore, a new parameter is defined in the study. This parameter is called as economy index. The economy index can be defined as a coefficient. That coefficient is used to determine the pressure value which regulate the transition process of the pump from standstill to starting state. When the system pressure gets above the reference pressure value the pump is expected to stop, and when the system pressure falls below the reference pressure value, it should operate again. However, in that scenario, the system will stop and start too much in case of low water demands. This process increases energy usage and shortens the pump life. After the usage of economy index, the system will start to work when the system pressure value falls below the reference pressure value multiplied by the economy index, not immediately when it falls below the reference pressure. Using this method, the system will be prevented from running and stopping redundantly in case of low water demand or leaks. That prevention would provide energy saving and pump life will be extended as well.
The new algorithm is tested in a simulation environment. Tests are completed on three different scenarios. To see the effect of the economy index, multiple simulation runs are conducted keeping the water demand constant and changing the economy index. Furthermore, to see whether the economy index can provide additional energy saving in each water demand, new simulation runs are designed with different water demands keeping the economy index constant. Moreover, the daily water consumption is modeled, and the simulations are conducted run in different economic indexes. 
In the first scenario, the pump runs and stops less frequently while using a low economy index. When economy index is high the system tends to run and stop more frequently as expected. When the economy index is low the system pressure varies in a larger range, and it oscillates in a narrower range when the economy index is high.
In the second scenario, the pump runs continuously when there is a high water demand. However, when the water demand is low, the pump runs and stops. The pump never goes to standstill status in high demand conditions since it meets the water demand of the system by working continuously. As result, it cannot be said that the economy index provides a considerable energy saving in high water demand conditions.In the third scenario, the modeled daily water demand caused the pump to display different working characteristics at different times. This differentiation is observed as different slopes in the energy curve. Slope of low water demands is lower when the economy index is also low. The main energy saving is provided here.
According to the data obtained as output of simulations; an energy saving around 80 percent is achieved in the first scenario with the continuous low water demand. In the second scenario, it is observed that the economy index provides savings only in low water demand. In the last scenario an energy saving around 40 percent was achieved with a daily life water demand model. Those results support the claim that a significant amount of energy saving can be achieved with the new controller designed for hydrophore systems. 
As a result of the study, a pump control mechanism is designed for hydrophore systems which are used almost everywhere in daily life and causes a considerable amount of energy consumption. That design provides a more efficient energy usage as well as to extend the service life of hydrophore system. This control mechanism can be customized for each centrifugal pump and it can be applied in currently operating hydrophore systems. With the future extensions of this study, even further improvements can be made and more energy saving amounts can be achieved. This would be very advantageous for sustainability.