Building Performance Optimization Services in the city of Boras, Sweden. Siemens Building Technologies Johny Hjerpe +46317276103 Johny.hjerpe@siemens.com

Summary In 2002 the Siemens branch office of Gothenburg and representative of Boras started trail project of how the Siemens Building Performance Optimization (BPO) Service model can support the city of Boras to increase energy efficiency in buildings. Subject of the project is a school campus called Erikslund. Siemens was able, in close cooperation with the management and operational staff of the school campus, to reduce energy consumption by more than 30%. These savings where achieved without major investments in equipment or changes on the building itself. The key to the success is the BPO Service model and to make maximal use of the installed Building Management System (BMS) form Siemens. As a result of the trail project Siemens is now taking care for comfort and energy efficiency in total 12 buildings in Boras.

Introduction Siemens Building Technologies of Sweden introduced a new Service in 2002 that reflects the increased interest of the market in energy efficiency, environmental responsibility and increasing energy prices: The so called Building Performance Optimization Service - Concept. The aim of that offering is to develop a tailored service agreement together with the customer to optimize the building’s performance. The offering, which is part of the Advantage Services, include Energy Optimization, Operational and Alarm Management Services. Cost effective implementation of these services is made possible by connecting to Siemens’ Advantage Operational Centre (AOC). To give an example of how the BPO- Service provides value to Siemens customers the school campus Erikslund in Boras was selected. In order to provide a pro active service the branch office of Boras scanned in 2002/ 2003 the consumption figures of the customers with existing Service Agreements to identify customer sites with high consumption. It the case of the school campus Erikslund the deviation between the benchmark for schools and the actual benchmark of the campus indicated a need for a more in depth investigation of how the energy in the buildings is utilized.

The Project The school campus contains three buildings: The oldest building on the campus is Komvux, it was built around 1945 and is dedicated to adult education. In the early 70’s the school was extended by the Erikslund building, a high school, and a gymnasium. Approximately 1’100 students are on the campus with a total heated area of ca. 12’600 m2.

Figure 1: Class Room Figure 2, Komvux Building

All three building are supplied by one central district heat substation. The majority of the heat demand of the building is covered by a radiator system; additional to that most of the space is mechanical ventilated. The whole campus is controlled by a VISONK- System which is connected to DESIGO- Insight management station. This allows Siemens to monitor and control the whole facility remotely. Looking at the specific consumption (kWh/m2) figures of 2002 and comparing it with benchmark figures, it is indicating that the way of how the energy is used on the campus can be improved.

Energy Benchmark for Erikslund - Komvux Campus

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Based on this assessment, the available data and the competence Siemens has in optimizing HVAC- Systems the responsible officials of the Boras community were invited by Siemens to discuss the findings and to introduce the details of the BPO service model. A proposal was presented how Siemens can support the owner to increase energy efficiency of the campus with the result of lower energy costs and less CO2 emission but without effecting comfort levels. The representative of Boras decided to commission Siemens to apply the BPO service model to the school campus.

To understand the BPO service model it is important to understand the idea of it. It’s based on tow phases: Phase 1: A tailor made Solution Build a tailor made solution for the specific needs of the facility and it’ occupants. As described below, Siemens followed together with the customer, a clear roadmap to gather all necessary information, data and requirements.

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Meetings with the headmaster and operational staff gave Siemens insight in the operational sequences of the campus and its special needs. On the other hand these meetings were a good opportunity for the school personal to ask questions and understand what is going to happen. At the end of this first phase both sides had a common goal and understanding. Phase 2: Implementation In this phase Siemens is implementing the solution in close cooperation with site personal by following the process below:

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Before the implementation is actively roll out, the school campus’s Building Management System (BMS) was connect to the Siemens Advanced Operational Center (AOC). This is an important precondition and gives Siemens operational staff access to site 24/7 to monitor and control building operation as well as helping school staff to identify and fix HVAC related problems.

After the successful connection to site Siemens established a metering concept with all available meters in order to monitor consumption figures. This allows a monitoring of the effect that

optimization measures have on the consumption and gives indices for changes of operation. Using the AOC, Siemens staff is setting up diagnostic reports and is analyzing plant operation. In case of the school campus room temperatures, running hours of pumps and air handling units, flow and return temperatures and the actual district heat demand was trended. An Energy Engineer together with the AOC- Operator assessed and analyzed the gathered data. With this information a meeting on site was scheduled with the involved operational personal to share the findings and develop an optimization plan for the campus. In a first step the Energy Engineer, accompanied by a Siemens Service Technician and customer staff went to the different plant rooms all over the campus to become a full picture of the installation and its condition. By sharing know

Figure 6: The AOC

how, the findings from the analyzed data and input from the occupants Siemens and the operational staff agreed on optimization measures written down in an Optimization Plan. The measures which were taken can be split up in three categories:

− BMS related measures (Software)

− Organizational measures and

− Structural measures Measures based on the BMS like adjust control parameters, optimize set points and change of time schedules to actual needed values. The basic to be able to do such changes is a detailed understanding of the requirements of the specific space during a specific time. To be always up to date of these requirements, regular meetings with the headmaster are taking place to discuss needed adjustments of the control strategy. Additional to that Siemens Engineers applied latest control strategies to heating circuits and air handling units, e.g. the so called HEAT ECO function, Optimum Start Stop Control or the ECONOMIZER function based on the outside air enthalpy. As examples for organizational measures the following tow are mentioned:

1. The gymnastic building is supplied by a district heating connection of some hundred meters form the main substation of the campus to cover the energy demand for heating and domestic hot water of the showers through out the entire year. By using the existing electric heater in the DHW tanks it was possible to switch of the district heat connection during the summer period. This resulted in saved pumping energy and heat losses of the pipes.

2. As usual for district heat supplied sites, the customer of the utility has to pay a demand charge additional to the consumed kWh. This demand charge is depending on the highest value of heat that the site consumed during a certain period of time (e.g. 1h). Siemens optimized the programming of each heat consumer on site in a way that the maximum demand of heat has decreased significantly and the customer pays now less demand charge to the utility.

Measures where smaller structural actions were needed had been done as well. The Siemens BPO service model is not taking care only of optimizing BMS related equipment, a major contribution to the success of this project was the ability to look at the whole picture. Most of the class rooms in the newer building of the campus are heated by single independent ventilation units which are installed beneath the windows. A room temperature sensor controls the heating coil inside the unit and a damper the amount of outside air. During the night the damper to the outside is closed and the room set points are set back. By trending the consumption figures and after asking questions to the operational staff, Siemens started to check the function of the dampers. It turned out that a high percentage of the dampers were not working well, with the result that too much outside air infiltrated the space and this caused high energy consumption. The air handling unit in the gymnastic building for example was controlled by a room temperature sensor and schedule. As it is in the nature of these kind of building that the occupancy rate varies during the day heavily, with the effect that more outside air is provided to the space than it is needed to keep comfort level. Even in cases of very short term changes of the planed building schedule the air handling unit was not able to react on this changed conditions. Siemens applied CO2 and occupation sensors in order to control the air handling units based on demand rather than on a fixed set point or schedule. A close monitoring of the plant operation after adding the sensors and changing the control strategy by the AOC ensured the high performance of this measure. After implementing the measures of the Optimization Plan the necessary data points get trended in the AOC. Each deviation form the pre calculated budgets is generating alarms, which are carefully handled by the AOC Operator. Consumption reports generated on a regular base and discussed with site personal and the headmaster of the campus ensures the long term success and give the opportunity to extend the savings year by year. The following chart shows the development of the yearly heat consumption figures.

Discussion of the consumption figures The monthly consumption figures for heat of 2002 (Base year) and 2006 are showing the savings achieved for Erikslund school campus. The weather adjusted heat consumption 2006 is reduced by 707’000 kWh or 32%.

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The chart below is showing the heat consumption on a yearly base split up in a weather independent (domestic hot water) portion and in one for space heating.

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The figures are showing an interesting detail: The weather independent consumption is reduced by 60%. This is the result of changed heat supply of the gym during summer (less heat losses for district heat piping), the HEAT ECO control function that is reducing heat consumption especially in between seasons, the ECOMOMIZER function of the air handling units and the adjustments of heating set points. (The additional electricity consumption for preparing DHW in the gym is not taken in to account for that graph)

Heat Consumption Erikslund 2002 & 2006

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The chart of the heat consumption development is showing the continuing approach of the BPO Service Model. 2002 compared to 2003 shows a big reduction in heat consumption and during the following years it was possible to prevent an increase. Due to consequent optimizing plant operation it was even possible to enlarge the savings.

Figure 9 It can be assumed that a stop of monitoring and controlling the site closely the consumption tends to increase again. Like every process it is necessary to feed some amount of energy to keep it alive. The development of electricity shows a similar impressing picture than the heating. Even the consumption is more depending on the actual amount of students. Komvux student figures are quite varying, however the high school student are nearly constant throughout the year.

Development of electricity consumption from 2002 to 2006

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The savings are based on adjusted time schedules and reduced run hours of secondary equipment like pumps and fans because of a more on demand based control strategy. Important to mention is that Siemens and the headmaster of the campus meet at the beginning of each semester to adjust the time schedules to the new class schedules. The daily tracking of the schedules through the AOC is another important factor to keep the run hours at a minimum.

Development of heat consumption form 2002 to 2006

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References

1. Anders Thelin Boras Stad 2. Johny Hjerpe, Siemens Sweden, Responsible Energy Services 3. Christoph Glockengiesser, Siemens Switzerland AG, Energy Optimization Hankbook 4. Jean-Pierre Morelli, Siemens Switzerland AG, Sales Manuel Building Performance

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