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We approve the thesis of Çağlar Selçuk CANBAY Date of Signature .............................................................................. 09.09. Asst. Prof. Dr. Gülden GÖKÇEN Supervisor Department of Mechanical Engineering
............................................................................. 09.09. Assoc. Prof. Dr. Arif HEPBAŞLI Co-Supervisor Department of Mechanical Engineering- Ege University
.............................................................................. 09.09. Prof. Dr. Gürbüz ATAGÜNDÜZ Department of Mechanical Engineering
Prof. Dr. Zafer İLKEN Department of Mechanical Engineering
.............................................................................. 09.09. Assoc. Prof. Dr. Murat GÜNAYDIN Department of Architecture
Prof. Dr. Gürbüz ATAGÜNDÜZ Head of Interdisciplinary Energy Engineering (Energy and Power Systems)
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HVAC systems in buildings must be complemented with a good control scheme to maintain comfort under any load conditions. Efficient HVAC control is often the most cost- effective option to improve the energy efficiency of a building. However, HVAC processes are nonlinear, and characteristics change on a seasonal basis so the effect of changing the control strategy is usually difficult to predict.
Aim of this thesis is to reduce energy consumptions by defining new HVAC control strategies and tuning control loops in Ozdilek Shopping Center “OSC”. To investigate the potential for energy savings and to redefine control scenarios, an energy audit was carried out in OSC. According to these studies new strategies are implemented by the help of existing building management system “BMS” without making any investment. Performance indices were calculated and compared with the accepted standards. Then normalized performance indices are calculated to reach out a better understanding of the buildings’ efficiency.
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Binalarda her türlü iklim koşulunda ısıl konforun sağlanması için ısıtma havalandırma ve iklimlendirme “HVAC” sistemlerinin iyi kontrol edilmesi gerekmektedir. Etkin bir HVAC kontrolü binalarda enerji tasarrufunun en iyi yoludur. Ancak HVAC sistemleri yapısı gereği lineer olmadıkları ve sezonlara göre karakteristikleri değiştikleri için HVAC kontrol stratejilerini ve kontrol parametrelerini belirlemek çoğu zaman oldukça zordur.
Bu tezin amacı Özdilek Alışveriş Merkezinde yapılan deneysel çalışmalar yardımıyla HVAC kontrol stratejilerini belirlemek ve parametreleri yeniden ayarlayarak sistemin konfor şartlarını bozmadan en düşük enerji ile çalıştırılmasıdır. Enerji tasarrufu potansiyelini belirleyebilmek ve kontrol stratejilerini en uygun hale getirmek için enerji bilançosu çalışması yapılmıştır. Bu çalışma sonunda binanın performans değerlendirmesi yapılmış ve kabul görmüş standartlarla karşılaştırılmıştır. Bu çalışmaların ışığında yeni kontrol stratejileri mevcut bina yönetim sistemi “BYS” yardımıyla uygulanmıştır.
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Chapter 1
INTRODUCTION
1.1 General
For human beings, energy as work and heat has great importance for the continuation of life. Energy is the key to industrial development leading to the economic and social well-being of the world population. The growth of the world population, coupled with rising material standard of living, has escalated energy usage since the turn of this century [1].
Modern buildings and their HVAC systems are required to be more energy efficient while adhering to an ever-increasing demand for better indoor air quality and performance. Economical considerations and environmental issues also need to be taken into account.
Maintaining high standards of indoor comfort is an economically sound goal. Research shows that indoor comfort and productivity can be linked [2]. These studies indicate that the economic gain with a small increase in productivity outweighs energy savings obtained by reducing the indoor comfort levels. A balance between energy efficiency and indoor comfort must thus be obtained.
The goal of HVAC design in buildings is to provide comfort to the occupants. Because heating and cooling loads vary with the time of the day and of the year, an HVAC system must be complemented with a good control scheme to maintain comfort under any load conditions. Good control will also reduce energy use by keeping the process variables (temperature, pressure etc.) to their setpoint efficiently
Efficient HVAC control is often the most cost-effective option to improve the energy efficiency of a building. However, the effect of changing the control strategy (i.e. on indoor comfort and energy consumption) is usually difficult to predict. The success of implementing efficient energy management and control is coupled with understanding the performance of mechanical and control systems.
Control is essential feature of almost every engineering system and process. For many years, control was affected by analog means only. The advent of the microprocessor, however, made digital control possible, and cost reduction in their manufacture have led to their wide spread use in a variety of situations. Their adoption for the control of the building services systems has come to be known as energy management, and the terms “Energy Management And Control Systems” (EMCS) in North America and “Building Energy Management Systems” (BEMS) in Europe are used to describe installations of this nature [1].
BMSs centralize the monitoring, operations, and management of a building to achieve more efficient operations. BMSs have become an essential part of a modern building that contributes significant saving potential and function feasibility. However, the actual achievement of BMS relies on well-developed and commissioned BMS hardware and software, well-trained BMS users, and system designers of adequate knowledge and experience on BMS and dynamic performance of HVAC systems [3].
1.2 Present Study
The aim of the present study is to understand HVAC control principles and their applications, investigating the potential for energy savings and then reducing the energy consumptions by the help of BMS within a case study. Quite amount of money is invested to HVAC and its control systems which need to pay back in a short period. In HVAC automation sector, lack of knowledge brings long pay back times, high energy consumption and customer dissatisfaction.
In Chapter 1 the importance of efficient HVAC control and comfort in buildings are focused, then brief information is given about present study and literature survey. In Chapter 2 energy consumptions in buildings in Turkey is investigated. Then energy conservation activities and legislative studies in buildings are focused. Chapter 3 gives general idea on BMSs and its applications. Chapter 4 is theoretical study which aims to understand the automatic control principles in HVAC systems. Chapter 5 focuses the main idea of this thesis. This chapter explains the HVAC control principles and their applications. In Chapter 6 a case study which was carried out in OSC to investigate the
Zaheer-uddin et al. [9] explored the problem of computing optimal control strategies for time-scheduled operation of HVAC systems. The optimization problem that takes into consideration the building operation schedules consisting of night-setback, start-up, occupied modes and energy price discounts is formulated and solved for a given predicted weather profile. Results showing the optimal mass flow rates to the zones, air and water supply temperatures, energy input to the heat pump and the resulting zone temperatures are given.
Also some studies have been done on the optimization of supervisory control [10,11]. House et al. [10] investigated the problem of optimal control of the HVAC and building by using a systems approach.
Shengwei Wang et al. [3] developed dynamic and real-time simulation models to simulate the thermal, hydraulic, mechanical, environmental and energy performance of building a variable air volume VAV air-conditioning system and its BMS. A window-based user’s interface is developed to simulate the man–machine interface of a BMS, through which users can monitor the on-line operation, tune the local control loops, and reset the supervisory control strategies.
Mathews et al. (2002) [12] developed a simulation tool, QUICK control to predict effect of changing control strategies (i.e. on indoor comfort and energy consumption) more easily. This tool was then used to investigate the energy savings potential in a Conference Center. The influences of fan scheduling, setpoint setback, economizer cycle, new setpoints, fan control, heating plant control, lighting control and various combinations thereof was investigated. The simulation models were firstly verified with measurements obtained from the existing system to confirm their accuracy for realistic control retrofit simulations. With the aid of the integrated simulation tool it was possible to predict savings of 744 MWh per year (32% building energy saving and 58% HVAC system energy saving) by implementing these control strategies. These control strategies can be implemented in the building with a direct payback period of less than 6 months.
Chapter 2
ENERGY CONSUMPTIONS AND ENERGY CONSERVATION ACTIVITIES IN BUILDINGS IN TURKEY
2.1 Overview
To be able to understand the importance of energy conservation in buildings, energy consumptions shall be compared by sectors. Figure 2.1 shows the energy consumptions (average values from year 1980 to 2001) ratios by sectors in Turkey. This graph proves how important to carry on energy conservation studies in buildings and in industry. 36% of the energy is consumed by residential and commercial buildings [13].
Figure 0.1. Energy consumption ratios by sectors in Turkey
Besides the technological improvement, Turkey has a great potential to make new and modern buildings either in residential or in commercial sector. This means energy consumption in buildings in Turkey is increasing. Figure 2.2 explains the fluctuations of energy consumption values in buildings between 1980 and 2001. Highest energy consumption was 19,830,000 [TEP] in the year of 2000. Energy consumption in buildings tends to increase by recent years. Energy consumption ratios in the buildings comparing with the other sectors are shown in Figure 2.3. The rate of energy consumption is share of energy used in buildings in total and this rate fluctuates between 32.8% and 46.5% between 1980 and 2001 in Turkey. In 1998 energy consumption ratio in buildings made a peak then decreased to its average value.
2.2 Energy Conservation Activities In Buildings In Turkey
In Turkey, the energy conservation and efficiency studies have been mainly coordinated by The Ministry of Energy and Natural Resources (MENR). MENR have tried to establish the major objectives including energy efficiency and conservation in Turkey. There are two major energy conservation center called as the Energy Conservation Co- ordination Board (ECCB) and National Energy Conservation Center (NECC) of the Electrical Power Resources Survey and Development Administration (EIEI) which reports to MENR about studies on energy efficiency and renewable energy sources since 1981.
NECC has expenditures on studies, energy audits, publications and professional training. NECC benefits from international loans and expertise. ECCB is in charge of public campaigns on energy savings.
2.3 Legislative Studies
In the residential / commercial sector, more than 80% of the energy consumed is for heating. According to an EIE study carried out in 1997 based on questionnaires, energy use per unit building area could be reduced by nearly half by applying to all existing buildings the new heat insulation standards (TS 825) on building envelopes, issued in 1999 and effective since June 2000. In 1985, Turkey adopted mandatory standards for heat insulation in new buildings. However, heat losses in new buildings have been estimated at over 200 kWh/m^2 /year which is a high level compared to average losses in Europe [14]. Revision of the standard for heat insulation in buildings was finalized in April 1998 and issued by the Turkish Standards Institute (TSE). This new insulation standard (TS-825) and supporting regulation introduced in June 2000 makes it mandatory to reduce heating requirements by 100-150 kWh/m^2 /year. The existing building stock is increasing at an average rate of 5% annually. It is expected that a 50% improvement in energy efficiency in new buildings will be achieved by TS-825.
2.4 Governmental Buildings Energy Conservation Monitoring Programme
In accordance with the circular entitled measures to be taken by Governmental Organizations and Institutions in order to reduce their energy consumption issued by the Prime Minister, all governmental organizations have prepared annual reports on energy consumption in their buildings. These reports were sent to EIE/NECC by the ministry and evaluated by ECC. In 1999, information concerning 2,037 governmental buildings was evaluated [15]. According to the evaluation results, the energy consumption of these buildings was very high (more than 250 kWh/m^2 /year); only 48% of them have double- glazing and 40% have roof insulation.
Another project named “Application of Energy Efficiency Studies in Buildings in Erzurum” has been initiated in co-operation with the German technical organization (GTZ), the Erzurum Municipality and EIE/NECC in November, 2002. The duration of this project will be three years. Its aim is to enable municipal authorities as well as users of public and private buildings to take measures designed to reduce the use of energy in buildings. Implementation of the project will be realized in Erzurum and studies related to standards, regulations and training will be carried out in Ankara.
2.5 Statistical Studies
At the end of 1997, in co-operation with the State Institute of Statistics (SIS), a statistical study for the analysis of energy consumption of residential buildings, which covered the whole country, was launched. In this project, the analysis of the energy consumption in terms of fuel and electricity, the insulation status, heating systems, and the structural properties of the residential buildings have been realized on the basis of geographical regions.
2.6 Energy Labeling / Standards
Under the co-ordination and supervision of EIE/NECC, and with the participation of representatives of the related manufacturers and public organizations, working groups have been set up on energy efficiency of household appliances, air conditioners and lightning.
Chapter 3
BUILDING MANAGEMENT SYSTEMS (BMSs)
3.1 Introduction
The objective of BMSs is to centralize and simplify the monitoring, operation, and management of a building or buildings. This is done to achieve more efficient building operation at reduced labor and energy costs and provide a safe and more comfortable working environment for building occupants. In the process of meeting these objectives, the BMS has evolved from simple supervisory control to totally integrated computerized control. Some of the advantages of BMSs are as follows:
When minicomputers and mainframes were the only computers available, the BMS was only used on larger office buildings and college campuses. With the shift to microprocessor-based controllers for DDC, the cost of integrating BMS functions into the
controller is so small that a BMS is a good investment for commercial buildings of all types and sizes.
Some other benefits of BMSs shall be expressed as follows: [16]
A. MONITORING: Constant monitoring of the plant, and ability to recall the monitored data at a later time. This has enables engineers and technicians to achieve a better understanding of their buildings and plant and has often led to plant improvements and energy saving as a result. Energy efficiency can be checked as a BMS can monitor and log data from fuel & electricity meters.
B. COMMUNICATION: Developments on personal computers and internet technology led BMS to communicate from anywhere. By web server function operator can reach to site from anywhere in the world.
C. MANPOWER SAVINGS & MAINTENANCE: The local boilerman, caretaker or plant operator can often be replaced by communicating BMS outstation, or one operator can cover more buildings. Especially maintenance contractors and energy management bureaus offer to run clients’ buildings and plant for them using outstations communicating regularly with the central station at the organizations headquarters.
D. COMMISSIONING: BMSs are becoming used in aiding the commissioning of plant in newly constructed buildings. This is rather used in large air conditioned office blocks with many small outstations on the air conditioning units around the building.
Some problems with BMSs shall be expressed as follows:
