ENERGY MANAGEMENT


between 0.08 and 0.125 person/m2


. All


zones are mechanically cooled on the first two floors and the rest are designed to be partly naturally ventilated and partly mechanically cooled, which is common with Malaysian hospitals. For modelling purposes, the internal floors of the naturally ventilated floors are treated as adiabatic surfaces. Other intermediate floors are not modelled as adiabatic surfaces since they will have different internal load and operation requirement with slightly different occupancy density. Occupants, lights, equipment, outside air infiltration and ventilation are described as internal gains for the zones. The hospital general indoor space temperature setting is typically designed to maintain a dry bulb temperature of range 22˚C to 25˚C with average relative humidity of 65% during occupancy hours. The intended cooling requirement was designed to maximum outdoor dry bulb and wet bulb design conditions of 34.2˚C and 31.2˚C respectively. Input data are obtained from earlier


surveys as-built data, available Malaysian Standard design guidelines,4,5


and from


energy audit data by earlier researches relevant to this work2


. The MVAC model


assumes that all zones are served by the same system, but with different temperature set-points and cooling schedules based on its space use classification. Table 2 shows the breakdown of annual


electrical energy consumption, total design cooling load and annual energy intensity of the reference base-case hospital building model. A calibration procedure is conducted by way of comparison, at the whole building level, the energy usage projected by the model to that of the measured utility data of medium-sized hospitals surveyed. Monthly


300 n BEI n Cooling capacity 250 11,000 10,800 200 10,600 150 10,400 100 10,200 50 10,000 0 Basecase


Improved HVAC


Improved glazing


Improved lights


All measures


Figure 5: Comparison of EEUI/BEI and cooling capacity reduction from selected ESM.


24 9,800


Table 5: Breakdown of annual energy consumption of selected cost-effective ESM in comparison to base-case building.


Parameters Chillers


Lighting and equipment Fans


Total End Uses BEI


BEI reduction


simulated energy consumption and average monthly measured data for the medium size hospital are plotted against each other for every month in the data set, as shown in Figure 4. Measured annual energy use index


of the surveyed hospitals ranges from 72 kWh/m2


/yr to 275 kWh/m2


average of 172 kWh/m2 building, with 253 kWh/m2


/yr, with


/yr. The base-case /yr, is well


within the range, in agreement and comparable to most of the surveyed hospitals of its size. This base-case building model as a whole, has been calibrated to reflect the typical local construction and energy use features for Malaysian hospital building for energy improvement retrofitting study.


Retrofits and energy saving measures A conservative energy saving retrofitting strategy involves the use of efficient lighting for reduced power density, efficient ventilation and air-conditioning systems for reduced running costs, improved glazing construction material for reduced solar heat gain, and improved ventilation control of outside air to the base-case hospital building. Earlier studies have shown that some measures, often advocated in temperate climates, were found to be of little significance in


11,200


Units kWh kWh kWh kWh


kWh/m2 (%)


Base Case


9,144,876.93 8,064,322.72 1,735,641.39 18,944,841 253


All ECM


6,414,456.87 6,800,367.48 242,688.83 13,457,513.18 180.8 28.85


Malaysia’s hot and humid climate. Analysis using a DOE-2 simulation program to examine mechanisms for implementing energy conservation programs in Thailand, showed that roof insulation retrofit on low rise government buildings offers attractive energy consumption improvements, but the use of double glazing is not so in terms of cost effectiveness.2


Simulation


results were analysed from the perspective of energy reduction potential, reduction in cooling load capacity due to reduced heat gains and improved systems efficiency, and cost effectiveness of the proposed measures. Tables 3 and 4 provide comparisons of the selected Energy Saving Measures (ESM) technical and economic potentials. The tables summarise changes to annual energy use breakdown, annual energy use intensity, retrofits cost effectiveness in simple payback periods (the ratio of the incremental cost of retrofit measure and the annual energy cost savings) after each variation of the selected retrofitting is added to the reference base-case model. This is based on a simple energy tariff of RM 0.208 per kWh of electricity and using the Malaysian Public Works Department component cost data for minor works.6 Further analysis of results shows the


most cost effective retrofits are with the double LoE tint spectrally selective glazing, T5 lightings, improved chiller COP and the application of FCU air conditioning system. Table 5 provides output of the Base-case hospital building energy intensity to the one with the selective overall improvement. Simulation results show 661 kW


reduction of design cooling load requirement and a 28.85 % reduction in energy intensity from the viable selected ESM retrofits, providing cost saving of RM 15.18 per m2


of building area. Figure 5


shows an incremental comparison between the best individually selected energy saving measures and the one with all measures put together. This is to illustrate technically, the level of significance of each measure in reducing energy consumption of the base-case building. Individually, improving the MVAC system yields the greatest annual energy savings followed by lightings retrofit. Improvement on MVAC and lighting systems provides the best strategy to


IFHE DIGEST 2017


Cooling capacity (kWh)


kW/m2


/yr


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