monitoring technique, evaluation methodology and ...

MONITORING TECHNIQUE, EVALUATION METHODOLOGY AND RESULTS FOR A MULTIFUNCTIONAL BUILDING WITH GEOTHERMAL ENERGY Johannes P. Fuetterer; Ana Constantin, Martin Schmidt, Rita Streblow and Dirk Müller RWTH Aachen University, Institute for Energy Efficient Buildings and Indoor Climate, Mathieustraße 10, 52074 Aachen, Germany, [email protected] ABSTRACT

Higher complexity of energy concepts in modern buildings leads to an increase of the amount of data points within a building automation system. More and more degrees of freedoms for different control strategies and approaches are available and energy efficiency of complex energy systems hardly depends on their operation mode. The authors implemented an extensive monitoring system into a multifunctional 7222 m² building for offices, laboratories and conferences. A complex energy concept with virtually all state-of-the-art building technologies satisfies the building’s energy needs while aiming for high energy efficiency. The paper presents guidelines for sensor placement via introducing four theoretical monitoring layers. Accomplishing sensor equipment at all four monitoring layers leads to a complete system that enables analysis toward technical operation and energy efficiency. They further present a data processing methodology. The paper explains how data is gathered from an OPC data access server and stored into an event-based SQL data base. The data is either processed on demand via different software tools or analysed within automatically generated reports. The authors present their evaluation methodology by introducing the content of their monitoring reports. The four existing report types are: a daily energy report for the building, a daily energy report for the systems of energy conversion, a daily energy report for the systems of distribution and demand, and a monthly energy report. With the presented reports it is possible to assess a complex energy concept and a huge amount of data and derive clear and meaningful statements. Optimization can be relevantly supported by such system. Without ongoing information and system insight optimization can only be hardly conducted. For the monitoring object it is obvious that the energy concept is currently not working according to its expected energy consumption and efficiency. The monitoring system will as such support further work towards control strategy and operation optimization. Keywords: monitoring, data storage, data processing, evaluation, visualization, INTRODUCTION

Higher complexity of energy concepts in modern buildings leads to an increase of the amount of data points within a building automation system. More and more degrees of freedoms for different control strategies and approaches are available and energy efficiency of complex energy systems hardly depends on their operation mode. We implemented a complex energy system with virtually all state-of-the-art building technologies into a multifunctional office building with additional conference and laboratory use. Further we implemented an extensive monitoring system for energetic and operational analysis of the energy system. Via detailed monitoring reports it is possible to get a clear

CISBAT 2013 - September 4-6, 2013 - Lausanne, Switzerland

751

picture of the system’s operation mode and behaviour. It is possible to identify malfunctions and failures. Our monitoring results show that the prior to the building’s construction designed control strategy is not working with satisfying energy efficiency. The actual control strategy has to be improved and research towards new advanced control strategies and approaches has to be done. In this paper, we present how we placed sensors following theoretical monitoring layers which allow for detailed analysis of building energy systems. We introduce our technical data gathering and storage system. From a technical point of view, we present our methodology for data processing, either on demand or by automatic reporting. We present a solution for dealing with huge amounts of data and build monitoring reports in order to support system evaluation and optimization. As results we present an extract of a monitoring report. BUILDING, ENERGY CONCEPT AND MONITORING PRINCIPLE

The object of interest for our monitoring system is the new main building of the E.ON Energy Research Center at the RWTH Aachen University. The building offers facilities for 250 employees. Its energy concept meets the trade-off between fulfilling all demands while maintaining a high energy efficiency. As shown in Figure 1 the concept consists of different energy conversion and distribution units. The system’s heart is a turbo compressor driven heat pump. A glycol cooler and a field of 40 borehole heat exchangers keep the energy balance of the heat pump’s hot and cold side throughout the whole year. A co-generation plant provides electricity, mainly used for the heat pump process, and high temperature heat for integration into a heat-to-cold shifting sorption process, or for direct use in laboratories or for additional heating energy.

Figure 1: Energy concept of the monitored multifunctional office building. We organized the system in conversion, distribution, demand, and process layer. In order to gather data in required detail the sensors of the building automation system it was necessary to install additional sensors. We added sensors to provide a complete energetic and system operation monitoring data within four layers, which are detailed below. The sensor placement guarantees holistic and complete sensor equipment for monitoring purposes towards system optimization and energy efficiency.

752

CISBAT 2013 - September 4-6, 2013 - Lausanne, Switzerland

Global consumption layer: This layer consists of all energy and mass flows that enter or leave the building. The electricity, water and gas consumption and the transfer of ambient energy are part of this layer. Energy conversion layer: All energy conversion related energy and mass flows are part of this layer. Inlet and outlet energy flows occur for every energy conversion unit, e.g. for the heat pump these flows are the electrical energy, the absorbed ambient energy and the emitted heat flow. Furthermore, sensors that map and image the conversion and generation process internally, such as temperature, pressure, control parameters, etc. within conversion units belong to this layer Energy distribution layer: Energy flows supplied by the energy conversion system are allocated and distributed within the building. Buildings can be separated in zones, following their use, their energy distribution principle and their geographical orientation. For each distribution system and for each use of the building the energy consumption has to be calculated. The distribution layer monitoring sensors are gathering the energy flows supplied to or extracted out of these different zones. Utilization layer: Each energy or mass flow satisfies a certain goal, within multi-functional buildings e.g. thermal comfort in office rooms or staff facilities, heating for test benches or cooling for server rooms. The evaluation of the goal-satisfaction is the last elementary monitoring layer. Given physical sensor equipment at all four layers, it is possible to conduct variable and complete assessments. Such assessments are orientated towards different key performance indicators (KPI), distinct parts of the equipment, system interaction, user behavior and so on. We used the four theoretical layers to place our sensors as follows: at the global consumption layer electricity flows entering the building from the grid or leaving the building due to cogeneration plant and PV production are measured. The gas consumption and the fresh water amount are observed. Furthermore, the energy exchange with the environment via the geothermal field and via the glycol cooler is included. At the energy conversion layer all energy flows entering and leaving all different conversion units are measured. KPIs of the heat pump, the boilers, the cogeneration plant, the chiller, and the sorption-supported air handling unit can be calculated. Data for other parts of the hydraulic systems, e.g. buffer storages and distribution systems is available. Concerning the energy distribution layer each energy distribution principle, such as concrete core activation, façade ventilation displacement ventilation, active chilled beams, air handling units and circulation air coolers, is separately monitored. Distinctions between different zones, like the east and the west energy supply hydraulic network for façade ventilation units and the four different zones of the concrete core activation are made. The monitoring system gathers data of the ventilation mass flows for each room. All operation data of the façade ventilation units, altogether 40 data points, is logged. At the utilization layer due to the immense sensor amount ten reference rooms have been chosen. These reference rooms are equipped with sensors measuring all supplied and extracted energy flows. In every room of the building, the room temperature, humidity, CO2 and volatile organic compounds (VOC) are monitored. Installed sensors measure the energy transfer for all special demands, such as server cooling. ARCHITECTURE OF THE MONITORING SYSTEM

A common building automation system – field, automation and management layer – was installed in the building during its construction. Programmable logic controllers automate field devices, such as control panels, sensors and actuators. A management server provides a supervisory control and data access system that is able to access all network data points.

CISBAT 2013 - September 4-6, 2013 - Lausanne, Switzerland

753

BACnet integrates BACnet-compatible parts of the technical building equipment directly into the system’s management layer. We connected the institute’s intranet with the building management network and added a cloud server infrastructure. The cloud is connected to the building management network and to the institute’s intranet; see Figure 2 left. We virtualized the building management server, moved it into the cloud and added a monitoring server hosting all necessary services. A service logs every data point occurring in the building automation system and redundantly stores it into two event-based databases. The service uses an OPC (object linking and embedding for process control) data access server to gather data. OPC is a standard and commonly used data access protocol. The OPC server scans PLCs and BACnet devices within the building management network and provides data objects. Two other services include weather forecast, a weather station and a wireless sensor network into the database. Temporary measurements are integrated via a data import tool; see Figure 2 right.

Figure 2: left: Building automation infrastructure with cloud server and link to the institute’s intranet; right: Schematic of the data logging and storage system DATA PROCESSING METHODOLOGY

Basically, different software tools and programming language are able to access SQL data bases and process data. We implemented routines for data processing in Python, Excel, MATLAB and Java in order to be as interoperable as possible and in order to provide flexible data access for data user’spreferences. The data bases are accessible via VPN through the internet. An extensive building data catalogue is available for data users. The data catalogue consist of a description every data point that is available through the system. Every data point is included in a schematic which is linked out of the building catalogue.

Figure 3: Schematic of the data access and processing system with online publication A data analytic and report generation system operates on a virtual machine in our cloud infrastructure. It generates detailed daily, weekly and monthly reports on energy consumption and KPIs; from whole building scale down to every single energy conversion unit and

754

CISBAT 2013 - September 4-6, 2013 - Lausanne, Switzerland

distribution system. Reports are generated in HTML format. A cloud-based web server hosts generated reports to the internet. Daily energy report for the building The daily energy report for the building consists of an energy flow diagram, a table with additional information about the system performance and a plot with weather data. The energy flow diagram as shown in Figure 4 gives an overview of the total amounts of heating and cooling energy produced and distributed in the building. Different grey types indicate the temperature levels of the energy flows, starting from cooling energy at 6°C and 17°C on to heating energy at 35°C and 80°C. The systems of energy conversion and distribution are shown together with the related amounts of energy for the day. More information about the systems can be found in the table, which additionally contains information about maximum heat flow, as well as maximum and minimum temperatures of the day. Another diagram shows the outside air temperature and global radiation that we obtain from our own weather data monitoring system. Daily energy report for the systems of energy conversion In order to get a deeper insight in the performance of the most important systems of energy conversion, detailed reports are created daily for the heat pump, the condensing boiler, the central heat and power unit as well as for the geothermal field. A table gives information about total amounts of energy, maximum and minimum values of heat flows and temperatures, the operating mode and operating coefficients. Two plots show the temperatures and heat flows during the day. The report is completed by information about outside air temperature and global solar radiation.

Figure 4: Daily building report’s energy flow diagram Daily energy report for the systems of distribution and demand Reports about the high temperature heating, low temperature heating, and cooling energy distribution show the daily characteristics of how the energy is used in the building. Again a table summarizes information about amounts of energy, maximum and minimum heat flows and temperatures for the day. A plot shows the heat flows going to or coming from

CISBAT 2013 - September 4-6, 2013 - Lausanne, Switzerland

755

the different systems, e.g. for the systems of low temperature heating. Additional plots display the temperatures of the flows over time and the weather conditions at the building for the day. Monthly energy report Once in a month a report is created that summarizes the total energy production and consumption of the building’s systems. Furthermore it shows how these amounts of energy are allocated to the different days of the month. Information about the outside air temperature and the total amount of global radiation in the month completes the report. The monthly energy reports are a basis for long time observation of the overall building performance. RESULTS

As a representative result we present the energy flow diagram from an example building report for a cold day in March 2013. It is shown in Figure 4. On this day with an outside mean temperature of -3.2 °C high amounts of energy are needed for thermal heating. As can be seen in the figure the heating energy is provided by the heat pump, the CHP and the boiler. The CHP produces 617.3 kWh, the Boiler 744.6 kWh of high temperature energy this day. The major part of these amounts (950.3 kWh) is transferred to the low temperature grid where it is used for thermal heating purposes additionally to the energy from the heat pump. A smaller part (248.6 kWh) is used as process heat for the laboratories. The figure gives an overview about how the system operates to satisfy the building’s demand. It shows how the energy conversion units interact. CONCLUSION

We presented four theoretical layers for sensor placement that lead to a complete sensor equipment for analysis towards evaluation and optimization of complex energy concepts. We outlined a solution for gathering data out of a common building automation system, for storing it and for making it accessible for analysis. We presented automated reports that evaluate the energy system from an energetic and operational point of view. They provide a clear insight about what is happening within the system. They enable the identification of malfunctions and disadvantageous operations. Our energy concept is currently not working according to its expected energy consumption and efficiency. The monitoring system will as such support further work towards control strategy and operation optimization. With the presented reports it is possible to assess a complex energy concept and a huge amount of data and derive clear and meaningful statements. Optimization can be relevantly supported by such system. Without ongoing information and system insight optimization can only be hardly conducted. REFERENCES

1. J. Fuetterer, A. Constantin and D. Mueller, "An energy concept for multifunctional buildings with geothermal energy and photovoltaic," in CISBAT international scientific conference 2011 - proceedings Vol. 2., Lausanne, Switzerland, 2011. 2. American Society of Heating, Refrigerating and Air-Conditioning Engineers, „ANSI/ASHRAE 135-2010 Standard 135-2010 - BACnet A Data Communication Protocol for Building Automation and Control Networks (ANSI Approved) SSPC 135 and TC 1.4, Control Theory and Application,“ ASHRAE, 2011.

756

CISBAT 2013 - September 4-6, 2013 - Lausanne, Switzerland