Tramo Diego de Almagro – Cumbres

In the 2007 study, New Zealand electric energy efficiency potential, the Electricity Commission of New Zealand (ECNZ) partnered with the energy consultancy company KEMA to better understand the market demand for energy efficiency. The study also estimated the potential savings that could be made throughout New Zealand (KEMA and ECNZ, 2007). The scope of the study was to calculate the consumed energy and predict the potential energy savings within existing residential, commercial, and industrial buildings using commercially available and viable methods. To do this, a sample selection of buildings were monitored to record their energy consumption. The greatest limitation of this study is that it only focused on the electricity use within the buildings, therefore gas or other fuel based equipment are not taken into account. Although only electricity is assessed within the study, it still provides an understanding of how much energy is used in commercial buildings.

In 2006, the annual electricity use for New Zealand was approximately 38,000 GWh (GigaWatt hours) (KEMA and ECNZ, 2007). Out of the total, the commercial building sector accounted for 23% (8,740 GWh); this represents the smallest energy usage for the building sector. Figure 2 illustrates the breakdown of energy consumption for the three building sectors that was calculated.

With a focus on the commercial buildings, the KEMA and ECNZ report illustrate the annually consumed energy for all commercial buildings as a break down for each of the end-uses. This can be seen in Figure 3.

As Figure 3 illustrates, interior lighting consumes the highest proportion of energy used at 32% of the total; this accounts for ~2,800 GWh annually. HVAC equipment represents the second

Figure 2. Calculated annual energy consumption by building sector. Recreated from (KEMA and ECNZ, 2007).

23%

33%

44%

highest proportion, consuming approximately 2,400 GWh of energy annually. The HVAC equipment represents 28% of the energy consumed by commercial buildings. The remaining 40% of energy consumed in commercial buildings is used by a range of different end-uses such as domestic water heating, plug load equipment, and other miscellaneous loads.

Although the KEMA and ECNZ report has identified HVAC equipment to consume ~2,400 GWh of energy annually, this only represents the electricity that is used. To address this limitation of the report and have a comprehensive understanding of the total energy consumed in New Zealand commercial buildings, including gas, the preliminary results of the Building Energy End-use Study were reviewed.

The energy consumption figures for HVAC systems vary between the 2007 KEMA and ECNZ report and the more recent study, the Building Energy End-use Study (BEES). Because the BEES data that is currently published is still specific to individual buildings, an average for the overall building stock has not been determined yet. As a result, the data that is reported upon in the BEES year three report presents a range of different values. The range of values presented identify that the HVAC energy proportion of 28% in the KEMA report is too low. The BEES report identifies that 40-80% can be expected. Gas energy use is also monitored in the BEES which explains why there is a higher proportion of energy consumed by HVAC equipment in comparison to the KEMA report. Because the collected data also contains the gas energy use, it provides a more reliable representation of the total energy consumption and end-uses within commercial buildings.

Figure 3. Commercial building electricity usage by end-use. Recreated from (KEMA and ECNZ, 2007).

0 500 1000 1500 2000 2500 3000 Exterior Lighting Office Equipment Domestic Water Heating Miscellaneous Refrigeration HVAC Interior Lighting GWh of Energy

With current energy monitoring data that has been collected and presented in the BEES year three report, the energy use for HVAC systems is highly variable, “ranging from 1% to 58% of total electricity consumption” (Isaacs et al., 2010). The year three report by Isaacs et al. states that this is a result of monitored data, at the time of analysis, not representing a full year and only in a small sample of monitored buildings. As the study progresses these values may change and become more defined. Because the generalised information currently available is not able to provide representative data, the case study buildings presented are used as a means to determine the total HVAC equipment energy that can be expected in the commercial building stock.

Because the main case study building that is provided in the year three report has a floor area of ~3,000 m2_{, it is not within the classification of strata four or five buildings that are focused}

on in this study. It is therefore not an appropriate example to use when demonstrating the significance that HVAC systems have on the energy performance of buildings in relation to this study. The floor areas of the other case study buildings presented in Table 2 were not provided, however it can be sensibly assumed that the tower block office building would have a floor area greater than 3,500 m2 _{and therefore be representative of the size of buildings}

focused on in this study.

The breakdown of the annual energy load intensities demonstrate the amount of energy (Watts) that are used per floor area, W/m2_{. Table 2 shows that the tower block office building}

uses 39 W/m2 _{for the HVAC system, while equipment uses 15 W/m}2_{, and lighting 16 W/m}2_{. In}

relation to the overall building energy consumption, the HVAC system represents the highest proportion of energy consumed, 56%.

Although the tower block office building uses the least amount of energy per floor area in comparison to the other case study buildings, the same trend of the HVAC system accounting for the highest proportion of energy is illustrated. Ranging from approximately 40 W/m2 _to

80 W/m2_{, the HVAC systems have the highest energy intensity per floor area of the buildings.}

This corresponds to 40-80% of the building’s total energy consumption of various sized commercial buildings. Based on the results from monitored case study buildings, it can be concluded that HVAC systems consume the greatest energy within commercial buildings.

Lighting Plug loads HVAC TOTAL

W/m2 _{% W/m}2 _{% W/m}2 _{% W/m}2

Case study

building 47 27% 54 31% 75 43% 176

Previous case studies Single storey office 14 17% 2 2% 68 81% 84 Tower block office 16 23% 15 21% 39 56% 70 Mixed use office 13 10% 30 24% 81 65% 124

Table 2. Case study building energy intensities. Recreated from (Isaacs et al., 2010).

To put the New Zealand commercial building energy consumption into context, international studies were reviewed. These studies are from the United Kingdom, United States, and Japan as they provide a range of different climate locations, construction methods, and energy efficiency requirements.