Figure 1. Evaluation of a typical project using Malcolm Well’s “absolutely constant incontestably architectural value scale”. The value focus was wilderness; today it might well be sustainability (1).

        In LEED and BREEM classification systems, some other important aspects such as materials used, carbon footprints, land use, water use as far as the energy performance of the building, have been taken into consideration in sustainability scoring of the building. LEED rating procedures which are used in this building are summarized in table 1.

2.    ESER   Contracting and Industry Co  Inc. Headquarters Building

2.1.        Architectural Characteristics

The building is designed in according to the building and construction codes and regulations, satisfying the utilization purposes and needs and particularly sensitive to the energy economy and environmental and climatic conditions. The building scheme is constituted by the spaces formed around one main core and 2 circulations cores. The building briefly includes;

-        2^nd basement in which a car-park for 51 cars take place. 

-        General services and annexes spaces, conference salon, cafeteria, and 1^st basement which includes various offices and storage spaces,

-        Ground floor which include the entrance, main hall with gallery, protocol entrance, cafe/waiting salon and the offices,

-        1^st floor which include gallery space, small meeting rooms, and offices,

-        2^nd and 3^rd floors which include floor-hole, small meeting rooms, open and private offices,

The roof space includes floor hall, guest rooms, meeting saloons and private office rooms. The building has totally 7 storeys. Total construction area of the building is 6500 m², while heated and cooled areas of the building 5000 m². Either floor of the building has 1 main staircase, 3 elevators, 2 fire escalators, 2 main and 2 auxiliary shafts and chimneys.   

In the outer cover of the building, natural heat and sun control have been provided by using different materials and construction details in east, west, south and north façades.  Particularly in the insulation details, in addition to the national codes, the materials and methods in according to the international standards have been used. In the selection of the building materials, the criteria such as environment, sanitation, hygiene, availability in nearest region, local product utilization and recycling have been taken into account. Various views from the building, putted in service in 2010, are given in Figure 2. 

Figure 2a. Various views of Eser Headquarter Building.

3. Climatic Conditions

For Ankara;

Dry bulb temperature for winter: -12 ºC

Dry-bulb temperature for summer: 33ºC

The building is in service between the hours  8.30/18.30.

Internal comfort temperatures: 22ºC (winter) and 24ºC (summer)

4. Energy Performance of the Building

To increase the energy performance of the building the precautions mentioned below are necessary;

a)    suitability of the projects to the codes and standards,

b)    selecting of high energy performance devices in the building,

c)    following the projects strictly,

d)    establishing automation scenarios and providing the system operations in according to the projects and scenarios.

In addition to the energy efficiency in building performance, the effects of internal air quality, day lighting, and noise are also important issues. For the purposes of increasing energy performance of the building the insulation thicknesses of 80 mm (walls), 120 mm (roof) and 60 mm (floor) have been used. Solar controlled triple-panes fenestration with U=1,8 W/m²K and SGF=0.46 has been selected. The average heat transfer coefficient of the building, fenestration and opaque surfaces included, has been calculated as U=0,85 W/m²K. To minimize the solar heat gains in summer, shading devices and internal curtains are applied. To improve the internal air quality AHU’s (air handling Units) with 100% outside air, frequency control of fan and coils having two way controls. 

In addition, renewable energy resources and trigeneration system also have been used for the purpose of increasing the energy performance of the building. The typical daily heat loads of the building for winter and summer months have been shown in Figure 3a and 3b. These variable loads are satisfied by a base-load CHP and GSHP system, three natural gas (NG) condensing boilers, and TES systems year-round. 100 kW GSHP+CHP combination operates above 7500 hours in a year on a base load both in heating and cooling mode. Boilers are operated in tandem thus permitting to maintain their maximum thermal efficiencies. The same is also true for GSHP+CHP combination.

4.1.       Hybrid Tri-Generation System

    The most important parameter in reducing carbon emissions effectively in high-performance buildings is to match the source exergy with the demand exergy of the building. In this respect, the first fold in this quest is to reduce the exergy demand of a building. If this can be achieved, the building becomes a low-exergy building. While the building approaches a low-exergy condition, solar, wind, waste heat and similar sustainable energy resources, which are also low-exergy type, become feasible to match with the building demand. In this case the so-called Rational Exergy Management Model Efficiency increases and consequently the direct and avoidable carbon emissions reduce substantially [2]. In a typical office building heated by a natural-gas boiler system and air-conditioned with a conventional chiller system, this efficiency is not greater than 6% (3). This is due to the fact that the high exergy natural gas and high exergy electric power is used to satisfy low-exergy demanding comfort cooling and cooling functions. A low-exergy building may reduce power and fossil fuel use simply by enabling the alternative energy resources temperature compatible with the building demands. In ESER building, a novel balancing philosophy was employed (2). This balancing act, which relies on temperature cascading of supply and demand is shown in Figure 4. The implementation of this balancing act increased the rational exergy management efficiency from 6% to 55% minimum. This means that the carbon emission reduction potential compared to a conventional system using natural gas both at the boiler (on-site) and at the power plant (off-side) is reduced by a factor of 2.1, that is shown in equation 1 (3). This factor does not include the contribution of ground heat through the heat pump, solar energy and the wind power. Together with heat recovery and all these, the total carbon emissions reduction factor is estimated to be more than 4.

Figure 3a. Load profile of the building-winter. 

Figure 3b. Load profile of the building-summer. 

                                                                                                    Figure 4. Exergy balancing act in ESER Building in terms of temperature cascaded applications.

According to Figure 4, the core of the supply system is a natural-gas CHP unit with a natural gas motor which follows heating demand (4). Electric power produced is complemented by solar and wind energies. Power is mainly used to drive the ground-source heat pump (GSHP). GSHP adds additional heat produced by the CHP unit. In summer GSHP produces cold energy and stores thermal energy obtained while cooling the building in the ground for the next heating season (Seasonal TES). Daily and hourly TES systems help to shave-off the thermal loads of the building. Heat and cold first go the respective TES tanks in the mechanical room. In order to increase the COP of the GSHP, it is operated at moderate temperatures (low-exergy supply mode). CHP unit however provides hot water at higher temperatures (high-exergy). Therefore in the heating mode two different TES tanks are used. One is low-exergy; the other is high-exergy. The similar approach is employed in cooling; while GSHP provides moderate cold (to cold storage); undersized conventional chillers are used on demand to maintain the ice storage tank. In summer the excess heat from the CHP unit is utilized in an absorption chiller. Solar collectors are primarily used to satisfy DHW loads.

4.1.       Annual Energy Consumption

Winter Operation: The average hourly heating energy needed is approximately 200 kWh which can be seen in Figure 3a (3). This valued includes the heating energy of fresh outside air too.  The winter operating hours of an office building in Ankara can be taken as 1200 hours. Therefore the annual total heating energy demand can be calculated as 240.000 kWh. In this connection the energy demand for just heating has been calculated as 165.000 kWh. This value is 50% less than threshold value for Ankara given in national standard TS 825 (3^rd region of Turkey).

Summer Operation: Hourly cooling energy has been accounted as 200 kW from Figure 3b, with a safety factor. This figure includes the cooling energy for cooling the fresh outside air too. The average operation period in summer for an office building in Ankara can be taken as 800 hours. Then, the total annual cooling energy is 160.000 kWh which is included ventilation consumption.  

Study of total energy consumption: The annually total energy consumption of the building, ventilating included, is approximately (240.000+160.000=) 400.000 kWh/year, and the energy demand per square meter (m²) is calculated as (400.000/5000 m²=) 80 kWh/m²year. This figure is 50% less than the similar buildings in Ankara (5). This calculation did not include the reduction by the heat recovery device in the ventilating system.  To meet the heating and cooling loads of the building a high efficiency flow chart has been used (Figure 4). As can be seen from Figure 3a and 3b, the 50 kW portion of base load will be met by heat-pump and for another 50 kW portion, the waste heat from cogeneration unit will be used. The coefficient of performance (COP) of the heat pump is 2,5 and the COP value with pumps and thermal storage included, has been assumed as 1,5.  The 20 kW portion of the electrical energy from cogeneration unit, feeds the compressor of the heat pump (summer and winter). The waste heat of the cogeneration unit is used in absorption chillers in summer, it is used for air-handling units and VRV (Variable Refrigeration Flow) system via thermal storage system. 

At the times in which the electricity demand exist but heating demand inexist, the heat from ground source heat pump and cogeneration unit have been stored and used in case of heat demand. When there is no cooling demand, i.e. at night times, cooling energy is stored. In case of excess thermal energy needs in winter the condensation boilers and in case of excess cooling energy demand in summer the air-cooled condensation units and ice-storage system are being put into operation. The chilled and hot water generated by these systems are transferred to the outside units of  VRV system by plate heat exchangers to meet the heating and cooling loads. While the COP of the VRV system has been assumed as 4,5 and COP of the whole VRV system (pumps included) has been taken 3,5. The heating demand of air-handling-units in winter has been met by the waste heat of the cogeneration device and the boilers. The cooling need in summer has been satisfied by the absorption chiller and air cooled chiller.

5. Operating Performance

5.1. Control of Air Quality

Until the contamination in the space is lowered to an acceptable level, air-handling units are operated in 100% rpm. Then, when the VAV dampers are moved to close position depending on the signals from CO₂ sensors, the rpm’s of the fans are reduced by frequency converters and maximum energy savings are obtained partly closing the 2-way valve of heating and cooling coils. Here, 2-way valves of the air handling units (AHU’s) are positioned in according to the temperature of supply air.

5.2. Energy Monitoring, Measuring And Modeling

These instruments have been used for the purpose defining the progressing of energy savings, understanding the building base load, reducing the operating expenses and cheking the load profile. For this purpose, various points of the installations energy analyzers, temperature and pressure sensors gas and water flowmeters, air quality sensing elements have been placed and linked to the Building  Automation System (BAS). the data obtained from these instruments, the efficiency of the devices and systems; energy consumption per m² and water consumption per capital can be calculated and monitored. In the plant, the saving potentials of these areas can be investigated and if there is, the necessary precautions will be taken.

5.3. Heating and Cooling Systems in Building

As noted above, the in-building installations that the heating and cooling systems served are; a) VRV system), b) heating coils of AHU’s, c) Floor heating circuit, d) domestic hot water system (DHW).

VRV system: This system is operated by its control system. Here, the outside unit has been adjusted between 25-30ºC in winter and 15-20ºC in summer, in the directive of manufacturer. In winter, when the water temperature goes below 25ºC the different stages of heating system (thermal storage, heat-pump, cogeneration unit, and the boilers respectively) are being put into operation.

Air Handling Units (AHU’s): The coils of the air handling units need higher temperatures than that of VRV system needs, depending on the outside temperature. While, in heating the water temperature regime of this system is 80/60ºC, this figure will reduce when the outside temperature rises. The operation regime of these circuits in cooling has been taken as 8/13ºC.

Floor Heating Loop: Hot water regime in the loop is approximately 55/45ºC and it can be fed from the heat pump. Here energy savings will be provided by placing 2-way valves in either floor.

Domestic Hot Water Heating Loop: In summer, there will approximately be 45ºC water in the storage. In addition, for the sake of Legionella occasionally heating will be made up to 70ºC.  The system will be mainly fed from solar collectors and supported by boilers in winter and by the waste heat of absorption chillers or boiler in summer.

5.4. Boiler Plant and Central Cooling Systems

Heating systems: a) Heat pump, b) cogeneration unit, c) boilers, d) thermal storage, e) solar collectors.  

Heat pump:  It will operate to meet the hating base load in all heating period. When there is no heat extraction from VRV and when the thermal storage temperature is higher than 45ºC, the circulation pumps of the heat pump will stop and there will be no generation. At this period, when the return water temperature is higher than 45ºC the heat extraction from storage tank will commence.

Cogeneration: The waste heat of this device will be used supporting the heating needs of VRV outside units and air-handling units.

Boilers: This system will operate to support the heating system (VRV, floor heating, air handling units, DHW) when the heat pump and cogeneration unit is not sufficient to meet the heating demand of the building. In this connection, when the cogeneration unit is not sufficient, the coils of air handling units will be fed by the boilers. Cascade boilers will be put into operation sequentially.

Thermal Storage: When there is no heating demand, the ground source heat pump will storage heat in the low temperature water tank in heating period.  Because of the temperature regime, this system will provide hot water to the outside units of VRV. When the temperature of the storage tank reached to 55ºC, the heat pump will stop. In the periods that there is no heating demand in the building, thermal storage will be implemented from cogeneration device to the tank. This system will feed the heating coils of air handling units.

Operating Principles of Heating System: VRV and floor heating system will be fed by ground source heat pump basically. When the heat pump are operating in full capacity, if the return water temperature drops below 43ºC for a definite time duration the cogeneration unit will start operating.  During night times, the heat pump will feed the storage tanks. At the moment at which the temperature exceeds 55ºC, this feeding process will terminate. In addition when the return temperature of the system drop below 50ºC for definite time duration the capacity of the heat pump system will be reduced or it will be stopped. When the 2-way valves of air handling units is fully-closed in an adjusted duration, the waste heat will be used in thermal storage. When the 2-way valves of AHU’s are fully open, the return water temperature is remained below 55ºC for an adjusted time duration and the blowing air temperature to the spaces cannot reach the set value, the boilers will be put into the operation sequentially.

Cooling Systems: a) Heat pump, b) cogeneration unit, c) absorption chiller, d) air-cooled chiller, e) thermal storage (ice and chilled water).

Heat Pump: It will meet the basic cooling load in cooling season. During the night times, when there is no cooling demand it will operate for thermal storage. When the temperature of the water in the tank rises to 9ºC, water will directly be sent to the system.   

Cogeneration unit: The waste heat of this device will be used to support the heat demand needs by absorption chiller. In night times, when there is no cooling demand it will operate to store cooling energy via absorption chiller.

Absorption Chiller: This unit chiller will be used for the utilization of the waste heat of cogeneration device (for VRV and AHU’s). When there is no sufficient solar energy domestic hot water system will be fed. In case of insufficient waste heat of cogeneration, the boiler support will be provided. The operating regime of the chiller circuit of cooling machine is 8/13ºC.

Air-cooled chiller: This unit will operate to support the load (VRV and AHU’s), when the cogeneration unit and heat pump is not sufficient to meet the load. The operating regime of the chiller is 8/13ºC. This unit will also be used to store ice in hot summer days.

Thermal Storage:

Cooled water storage: During the night times, when there is no cooling demand, cogeneration device and the ground source heat pump will store cooling energy (together with absorption chiller). During the daytimes primarily these storage will be used. When the temperature in the storage tank rises higher than 10ºC (setting is available for the value), cooling energy will be extract from ice-storage tank (if any) and/or the heat pump will be put into operation.   

Ice storage: During the daytimes, when the temperature is high, the system will operate from ice storage system. And during the night times, taking the advantage of lower electricity price the system will operate to store ice (cooling energy).

6. Plumbing Systems

    The solar collectors have been used to generate domestic hot water and the boilers have been designed to support the system. Rain water has been collected and used in gardening activities.  In addition, the grey waters from the lavatories have been purified and used in the reservoirs.

7.  Lightening and Electricity

High efficiency bulbs and apparatus have been used in artificial lightening. The type of the electric motors are high efficient type (EFF1).  The BAS and the electrical installation have been designed so that the air conditioning system can be operated efficiently.

8.  Renewable Energy

For the purposes of taking advantage of the natural lightening, day-lighting shafts have been constructed in the building. PV units and wind turbine are installed to meet electrical needs of the building partly. All these systems are shown in Figure 2.

9. Conclusion

The systems described above have increased the initial investment cost by 15%. On the other hands, improvements in the façades of the building, heat recovery systems, renewable energy technologies, combined heat and power (CHP) systems and efficient HVAC utilizations and efficient operation of these systems has reduced the fossil fuel consumption, CO₂ emissions and life cycle cost of the systems.

Acknowledgement

We would like to mention our special thanks to the personnel of OSTIM Investing Corp. who shared their experiences with us and Mr. Prof. Dr. Birol Kilkis, who is a member of High Performance Metrics of ASHRAE and the academic member of Başkent University.

References

[1]   Stein B., Reynolds, J. S.. Grondzik, T. W., Kwok, G. A., 2006, Mechanical and Electrical    Equipment   for Buildings, John Wiley and Sons Inc., Canada.

[2]    Kılkış, Ş. 2009. Kılkış Ş. “A Rational Exergy Management Model for Sustainable Buildings to   Reduce Compound CO₂ Emissions” Proc/e 40th Congress on HVAC&R – KGH, pp. 391-412.

  [3]   Kılkış, B., 2009, “What is a High Performance Building and What is not? Description,  Definitions and Basic Functions”, TTMD Journal, March-April 2009.

[4]  Jalalzadeh, A., 2007, “A Comparison of Electrical and Thermal Load Following CHP System”,  TTMD Journal, March-April 2007.

[5]  Çakmnaus, I., 2007, “Natural ventilation of existing buildings regarding to energy efficiency: An example in Ankara- Turkey”, REHVA World Climate Congress, Helsinki.