1. Estimation of Different Loads
1.1 Electric Energy:
1.1.1Cooling Energy:
1.1.2 Equipment Energy
1.1.3 Lighting Energy:
1.2 Air Conditioning Energy:
1.2.1 Internal Loads:
1.2.1.1 Internal load
1.2.1.2 Internal load
1.2.1.3 Internal load
1.2.2 External Load
1.3 Energy Demand of Service Loads:
1.3.1 Elevators load:
1.3.2 Basement load:
1.3.3 Water pump load:
1.3.4 Fire fighting load:
1.3.5 Control & IT system load
1.3.6 Kitchenette load:
2.Renewable Energy Sources
2.1 Wind speed at turbine location
2.2 Turbines' useful power
2.3 Wind energy contribution to building
demand
3.Conclusion
4.Lessons learned
General information on energy saving
The energy consumption of the building has been modeled and compared with that of a hypothetical baseline building that features the same geometry but rather than utilizing similar environmentally beneficial measures relies instead on the more established strategy of using air in place of a waterbased radiant ceiling system to cool the building. As the figure 1 indicates, the Pearl River Tower is expected to consume approximately 58 percent less energy on an annual basis than the hypothetical baseline building.
The same as for any building, the energy requirement of Pearl River Tower being an administrative building can be classified as electric energy, airconditioning energy and energy for service loads. The electric energy includes that for cooling, equipment and lighting. The air conditioning energy is to cover internal and external loads requirements. The internal loads are due to office equipment, office lighting and heat given off by people in the office. The external loads depend greatly on the surface proportion of the glazing as well as the sunprotection tools on the facades of the tower. Thus, the transmitted sun irradiance through the tower façade and associate space heating represent an extra load on the air-conditioning system. The service loads of the tower include power demand for basement, water pump system, fire-fighting system, control & IT system and kitchenettes.
Additional $13 Million to Construction Costs
Earned Back Within 5 Years because of Savings From:
Reduced Electricity Bills
Lower Maintenance costs
Extra Rent from Space Not Used for Air Conditioning Ducts
Will reduce energy consumption by about 60%
Hu Baiju (Chief Engineer) – Cut Carbon Dioxide
Figure 1 Comparison of Pearl River Tower with Hypothetical Baseline Building: Projected Annual Energy Consumption
Figure 2 The payback of energy saving of Pearl River Tower ( American Society of Civil Engineers,2008)
Detailed data analysis on energy consumption (Rasha Mazen&Magdy Radwan,2009):
1. Estimation of Different Loads
1.1 Electric Energy:
Assuming the number of working hours per day is 10 averaged over the week days. The building has total gross area 170,000 m2.
1.1.1Cooling Energy:
The specific energy consumption for cooling is selected at 50 kWhm-2a1. Therefore, the power required to fulfill the building demand of cooling energy is estimated as 50 x 170,000 / (10 x 365) = 2329 kW or 2.3 MW.
1.1.2 Equipment Energy:
The specific energy consumption for equipment is selected at the maximum value which is 110kWhm-2a
1. Therefore, the power required to fulfill the building energy demand for equipment is estimated as 110 x 170,000 / (10 x 365) = 5123 kW or 5.1 MW.
1.1.3 Lighting Energy:
The specific energy consumption for lighting is selected at 60kWhm-2a-1. Therefore, the power required to fulfill the building demand of illumination energy is estimated as 60 x 170,000 / (10 x 365) = 2795 kW or 2.8 MW.
Therefore, the total power to meet the cooling, equipment and lighting energies is equal to 2.3 + 5.1 + 2.8 = 1 0.2 MW.
Figure 3 Projected energy savings from large scale sustainable design strategies( American Society of Civil Engineers,2008)
Figure 4 The interior air conditioning (by group)
Figure 5 The cool radiant system (by group)
1.2.Air Conditioning Energy:
1.2.1 Internal Loads:
As the building has total gross area 170,000 m2, then office area is assumed 0.75 x 170,000 = 127,500 m2 for 75% occupation of offices from the building area.
1.2.1.1 Internal load due to office equipment: The energy consumption for internal load due to office equipment is selected at the maximum value, which is 15 Wm-2. Therefore, the power required to meet the internal load (due to office equipment) on the air-conditioning system is estimated as 15 x 1 27,500 = 1,912,500 W or 1 .9 MW.
1.2.1.2 Internal load due to office lighting:
The energy consumption for internal load due to office lighting is selected at the maximum value which is 20 Wm-2. Therefore, the power required to meet the internal load (due to office lighting) on the air-conditioning system is estimated as 20 x 1 27,500= 2,550,000 W or 2.6 MW.
Figure 6 The interior sensors in the office (by group
Figure 7 The interior fire hydrant (by group)
Figure 8 The security system of Pearly River system( by group)
1.2.1.3 Internal load due to persons in office:
The energy consumption for internal load due to presence of persons in the office is selected at the maximum value which is 7 Wm2. Therefore, the power required to meet the internal load (due to people in the office) on the air-conditioning system is estimated as 7 x 127,500 = 892,500 W or 0.9 MW. Therefore, the total power to meet all internal loads on the air-conditioning system is 1 .9 + 2.6 + 0.9 = 5.4 MW.
1.2.2 External Load
The energy consumption for external load is selected at the maximum value which is 60 Wm-2 of building surface area. As the tower has total gross area 170,000 m2, then the area per story is 170,000 / 71 = 2394 m2 as the Pearl River Tower consists of 71 stories. Assuming the floor area is rectangular in shape with length to breadth ratio equals to 5 : 1. Therefore, the length is 109.4 m and the breadth is 21.9 m. Subsequently, the surface area of the building is expressed as 2 x (length + breadth) x building height. The building height is 310 m and the surface area is 81,406 m2. The power required to meet the external load on the air-conditioning system is estimated as 60 x 81,406 = 4,884,360 W or 4.9 MW.
Therefore, the power required to meet the internal and external loads on the air-conditioning system is 5.4 + 4.9 = 1 0.3 MW.
1.3 Energy Demand of Service Loads:
1.3.1 Elevators load:
The Pearl River Tower has 1 escalator, 12 passenger elevators and 4 freight elevators. Assuming the power demand is the same for all elevators and escalator, i.e., = 178 kW. Therefore, the total power for operation of the building elevators and escalators is 178 x 17 = 3026 kW = 3 MW.
1.3.2 Basement load:
The gross area of the 5-story basement is 40,000 m2 and the average power demand is 10 Wm-2. Therefore, the power required for the basement load is 40,000 x 10 = 400,000 W = 0.4 MW.
1.3.3 Water pump load:
The power demand for the pump system is assumed to be proportional to the building height and the floor area. The power demand for a building with 11 -story and floor area of 1350 m2 is 30 kW. Therefore, the power demand for pump system in the pearl tower is 30 x (2394 / 1350) x (71 / 11) = 343 KW = 0.34 MW.
1.3.4 Fire fighting load:
Similar to the water pump load, the power demand for the fire fighting load is 6 x (2394 / 1350) x (71 / 11) = 68 KW = 0.07 MW.
1.3.5 Control & IT system load:
Also, the power demand for the Control & IT system load is 55 x (2394 / 1350) x (71 / 11) = 630 KW = 0.63 MW.
1.3.6 Kitchenette load: In analogy to the control & IT system load, the power demand for the Kitchenette load is 3 x (2394 / 1350) x (71 / 11) = 34 KW = 0.03 MW.
Therefore, the power requirement for all service loads is 3 + 0.4 + 0.34 + o.o7 + o.63 + 0.03 = 4.4 MW
Therefore, the total power demand to serve all the loads as listed above is 1 0.2 + 1 0.3 + 4.4 = 24.9 MW.
2. Renewable Energy Sources
The Pearl River Tower utilizes the wind and solar energy seeking "high performance building". This paper is focused on the utilization of the wind energy in the tower.
2.1 Wind speed at turbine location
The ambient wind speed in Guangzhou at 10 meters height lies in the range 9 – 16 km/hr, i.e., 2.5 - 4.5 m/s. The wind speed increases with height according to Hellman's equation (Hier, 2005):v w (h) = vw(10) (h / 10) α (1) Where vw(h) = speed of wind at height h (m/s), vw(10) = speed of wind at height 10 m and α is Hellman's constant ( = 0.34 for neutral air above human inhabitated areas). The wind turbines are installed at the mechanical floors, which are assumed at heights 100 and 200 m. This assumes that the mechanical floors are located approximately at one-third and two-third of the building height (= 310 m). Based on an ambient wind speed of 3.5 m/s (average value) at height 10 m, the wind speed at height of 100 m is 3.5 x (100 / 10)0.34 = 7.6 m/s and the wind speed at height
of 200 m is 3.5 x (200 / 10)0.34 = 9.7 m/s. Due the funnel shape of the openings where the turbines are located, the wind speed is increased 2.5 times its ambient value. Therefore, the wind speed, where turbines are located at the lower mechanical floor, is 2.5 x 7.6 = 19 m/s, and the wind speed, where
turbines are located at the upper mechanical floor is 2.5 x 9.7 = 24.25 m/s.
2.2 Turbines' useful power
The useful power developed by a wind turbine depends on the turbine radius R, wind speed at turbine location v, air density ρ (= 1.225 kg/m3) and turbine efficiency η as determined by the following equation (Dillon, 2010): P = 0.5π x ρ x R2 x v3 x η (2) The turbines employed in the tower are the Darreius turbines of efficiency 35% compared to 25% for the horizontalaxis turbines. The turbine radius is 5 m to suit the opening dimensions at the mechanical floors (Dillon, 2010).
Therefore, the useful power developed by one turbine at the lower mechanical floor is .5π x 1.225 x 25 x 193 x 0.35 = 115,485 W = 0.12 MW.
The useful power developed by one turbine at the upper mechanical floor is 0.5π x 1.225 x 25 x 24.253 x 0.35 = 240,104 W = 0.24 MW.
The total useful power developed by the eight turbines, four at each mechanical floor is
4 x (0.12 + 0.24) = 1.44 MW.
The above calculations are repeated over the wind speed range from 2.5 to 4.5 m/s in Guangzhou.
2.3 Wind energy contribution to building demand
Figure 9 shows the power generated by turbines and the percentage by which wind contributes to the tower energy for different values of wind speed. The figure indicates that the wind turbines contribute to the building's energy needs by about 2 - 12% which is slightly higher than the published value (Epstein, 2008). This is because the power demand of the podium was not considered as its dimensions are missing in the literature.
Figure 9 Wind power generated and energy contribution for different wind speeds (Rasha Mazen*1, Magdy Radwan2,2009)
3.Conclusion:
• Additional $13 Million to Construction Costs
• Earned Back Within 5 Years because of Savings From:
▫ Reduced Electricity Bills
▫ Lower Maintenance costs
▫ Extra Rent from Space Not Used for Air Conditioning Ducts
• Will reduce energy consumption by about 60%
• Hu Baiju (Chief Engineer) – Cut Carbon Dioxide
4.Lessons Learned
• Understand Uniqueness of Project and Environment to Implement Best Solution
• Sometimes Regulations Prohibit Projects from Achieving Net Zero
• Integrate Architecture, Mechanical, Engineering and Electrical Systems and consider their interaction