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energize - July 2010 - Page 50

The aim of these audits was to make the centres more energy efficient, so as to reduce electricity costs, counteract tariff increases, avoid possible power rationing penalties, increase asset value, and to help alleviate the South African energy crisis. This is achieved by reducing both the total energy consumed (kWh) and the maximum demand (kVA) of the centres though better control and retrofitting to efficient technologies.

Methodology

The energy audits consisted of a full site walkthrough identifying and documenting all energy usage points. The audits begin at the incoming feed and work through to the end points. At every point, the technology and control methodology is analyised to determine any inefficiency, and where identified, business cases for replacing or optimising are investigated.

Logging

The audit begins with the installation of a load logging device at the incoming feed. The device is installed for a period of no less than a week to obtain a normal operating load profile of the site. The logged data is analyised to determine if the centres are on the correct tariff, if the power factor is at acceptable levels and to determine any abnormalities with council metering or expected usage times.

Incoming feed

The next step is an inspection of the main transformers to identify loading percentages and to ensure that the site feed is optimised. Multiple transformers operating at low loads can be shifted to fewer transformers at a higher loads (where possible), and thus higher eff iciency. Vol tage levels are checked at s i tes where low voltage feeds are provided, and if supply is over nominal, corrective measures are investigated.

Lighting

In commercial environments, l ighting contr ibutes s ignif icantly to the total. During each audit, all the light fittings were counted and investigated. Lux levels were

noted, as the point of the audit is not to decrease lighting levels, but to provide the same lighting more efficiently. The national standards (SANS 204-2) also recommend Lux levels for different situations, and these levels were used as guidelines as well. Inefficient fittings were indentified, and alternative technologies can then be identified, and the business cases can be calculated for each retrofit. Changing to more efficient fittings will reduce both energy and demand costs, as commercial lighting is generally on during peak times. This means that these interventions have excellent payback periods.

Better control of the existing lighting fixtures also yielded significant savings. It is not necessary to light up an area unless it is in use or being lit for aesthetic reasons. Modern technology al lows for more detailed control of lighting and eliminates human error. Motion detectors, timers, day/night sensors and BMS systems can all be used to ensure that there is sufficient light for customers, aesthetics and security purposes, but reduce unnecessary usage.

The control of the lighting fixtures resulted mainly in energy savings (kWh), as opposed to kVA, however these interventions were generally easy to implement and very cost effective, making them attractive solutions.

Air conditioning

The air conditioning units of a shopping centre account for a majority of the power consumed. The audit helps identify areas of wastage and poor management. Compressors, circulating pumps and fans are often over sized and poorly managed; this leads to inefficient operation, demand spikes during start up and increased maintenance. During the inspection we investigate various options including VSDs, compressor cycling, air management and BMS control of the entire plant.

Findings

The energy audits of the Retail Africa portfolio were very successful and large energy and financial savings were found to be achievable at all sites. The majority of the sites investigated have 11 kV power suppl ies and the maintenance and

Commercial shopping centre energy audits

Information from Sedgeley Energy

In November 2009, Sedgeley Energy began a series of energy audits on the commercial portfolio of the Retail Africa Property Group. The common area portions of 18 shopping centres around the country were audited.

Site CO2 saving [tons/year] Saving [R/year) Payback [years)

Steenberg 313 R179 793 2,4

Glengarry 371 R215 400 2,8

Honeydew 148 R90 l88 2,8

Total 832 R485 381 2,7

Table 1: Voltage optimisation savings.

Site Demand saving [kVA] Savings [R/year) Payback [years]

L Corro 13 R16 248 1,4

Glengarry 20 R25 003 1,3

Sanridge 80 R99 648 1,23

Featherbrooke 49 R61 488 1,9

Irene 174 R187 980 1,5

Westcoast 126 Rl51 032 1,4

Total 462 R541399 1,5

Table 2: Power factor correction savings.

APPLICATION

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loading of their transformers was found to be acceptable. It was noted however that some smaller sites receive low voltage and in three cases the voltage levels were above nominal. A voltage optimisation device was proposed and the device savings and paybacks can be seen in Table 1.

The load profiles from the logging identified that all sites were on the correct tariff and no abnormalities with the utility metering system were identified. The data did, however, show that six of the sites required power factor correction to be installed, the details of the identified savings and paybacks can be seen in Table 2.

The lighting and load audits revealed that the majority of technologies currently installed were relatively energy efficient and changing to the most efficient fixtures was not feasible. There were a few retrofits required but the main area where savings were identified was in the control of the equipment.

Large energy savings could be achieved by instal l ing occupancy sensors with built in lux level control. Sedgeley Energy worked closely with management to ensure changes did not affect the mall security or aesthetics and that maximum savings could be achieved. The achievable savings through retrofitting and correct control of the lighting and other loads throughout the mall can be seen in Table 3.

Due to the size and current setup of the centres, there were limited savings achievable on the a i r condi t ion ing systems as the majority of the centres are st r ip designed with no common area air conditioning. BMS systems were proposed for the larger indoor centres and the feasibility studies are currently underway.

Conclusions

The results from the audits were very good and large savings were found with short payback periods. The findings showed that even though efficient technologies may already be in place, there are still achievable savings at good paybacks if investigated thoroughly. Apart from saving the shopping centre money, the savings also benefit the centre as a green building has the ability to achieve higher rentals due to:

The abil i ty of a green building to achieve higher rentals.

Faster lease up.

Higher resale value.

Pos s ib le fu tu re i ncen t i ves f rom government.

Greater consumer interest in the efficient building.

Contact Stuart Batchelor, Sedgeley Energy, Tel 082 941-2580, stuart@sedgeley.co.za

Site Retrofit[kW]

Equipment control[kWh / month]

Annual saving[R)

Payback[yearsl

‘L Carro 0,40 0 R 16 579 1,47

Honeydew Village 3,20 158 R 5 969 0,94

Kingfisher Square 2,00 855 R 6096 0,89

Parktown Quarter 2,30 1789 R 18 892 0,77

Steenberg 5,20 3261 R 31 287 1,44

Honey Ridge 0,40 1040 R 6 378 1,80

Clearwater Crossing 1,92 599 R 5 959 0,58

Clearwalet Offlce Partk 2,80 213 R 9 941 1,21

Sandridge Square 1,80 318 R 4 320 2,02

Eden Meadows 0,42 288 R 6 792 0,62

Glengarry 3,80 2830 R 17 881 0,66

Featherbrook Village 4,20 1232 R15 943 1,26

The Village 11,90 1260 R 19 244 0,86

Southdowns 0,80 347 R 3 129 1,60

Irene Village Mall 4,20 141824 R 9 775 1,36

Fountains Mall 9,30 1532 R 11 012 1,44

Westwood Mall 1,90 5571 R 19 052 1,68

Westcoast Mall 0,00 26845 R 168 714 0,37

Total 56,54 62962 R 376 963 0,83

Table 3: Retrofit and control savings.