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AUTOMATION &C O N T R O L S

Metered and billed energy consumption for the retrofitted building exceeded that of the older building. To realise energy savings, a full understanding of a building’s energy use through ongoing data collection and analysis of kWh and billing, is required.Globally, buildings are among the main users of energy. The use of energy by buildings is set to increase due to ongoing demand for services such as lighting, heating, cooling, ventilation and operating equipment. Buildings have a high potential for reducing energy consumption. In 2009, the World Business Council for Sustainable Development (WBCSD) said that “to achieve an energy efficient world, governments, businesses and individuals must transform the building sector through a multitude of actions". While it is recognised that energy is wasted as a result of inefficient building design, poor or non use of available energy saving technology is also a significant factor and retrofitting buildings is crucial if a reduction in energy use is to be achieved. The International Energy Agency (IEA) maintains that the lifespan of buildings is such that major retrofitting is justifiable and that buildings should look at replacing roofs, boilers, windows, variation systems and air conditioners. Retrofitting buildings involves installing more efficient lighting systems; wall and roof insulation; modernising heat sources and ventilation; using energy efficient building materials; using renewable energy sources; and the introduction of automation. This study sought to

A comparative study of electricity consumption in two buildings of similar architectural design and floor space, one of which was retrofitted at a cost of R4,3-million, with significant results.

Retrofitting buildings to lower energy consumption

by Takalani Bridget Thovhakale, Tracey Morton McKay and June Meeuwis, University of Johannesburg

determine if retrofitting a building could help reduce energy consumption.

Study area

The buildings are situated in the Simba Office Park in Sandton, Johannesburg. The control building (AB) actually consists of two buildings, building A (2250 m2), and building B (1750 m2). Both have three storeys. Building C is a retrofitted 4000 m2, four-storey building. The buildings are similar in other ways: both are commercial office blocks with a similar number of staff and equipment, save that building C has a canteen. This canteen has a variety of equipment including stoves, dishwashers, a fridge, freezer, microwave ovens, ovens, coffee markers, and kettles. At the time of the study, the electricity consumption for the canteen was not metered. Building C is equipped with video conferencing facilities and other office utilities similar to Building AB. In addition, each floor has a standard kitchen facility with appliances used by staff. Building C is occupied by the Central Energy Fund (CEF) and is known as CEF House. The CEF bought building C off plan and it was retrofitted after the design but during its construction phase. The CEF views the building as a showcase for energy efficiency and green architecture.

Methodology

Interviews were conducted with key personnel such as CEF House executives, the site electrical engineer, developer, and Simba Office Park managers. Data

Energy efficiency interventions

Cost in rand

HVAC 1 500 000

Double glazing to windows and glaze facades

1 112 559

Steel roof trusses (for possible photovoltaic panels)

573 821

Lighting Controls Option C (occupancy and light level sensors) Philips ActiLume

471 400

Insulation (external walls, ground floor and roof slab)

272 234

Generator (130 kVA for partial load excluding air-conditioning)

250 000

Light trays outside windows (east and west facades)

120 000

Labour for air-conditioning and ventilation installation

30 000

Automatic taps 34 000

Automatic urinals 14 000

Total 4 378 014

Table 1: Costs of implementing energy efficiency interventions in building C.

on floor space and building parameters was provided by the architect. Retrofitting measures were documented and associated costs noted. Electricity consumption data and billing for 13 months (April 2009 to April 2010) was collected from the buildings' electricity meter readings and supplemented with data from CEF executives and the developer. Statistical analysis was done

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addition, cavity wall insulation between the exterior and interior brickwork was included. Exterior bricks are red clay to reduce thermal heat gain and loss and external cladding was also installed. The use of a cool roof reduces the roof surface temperatures by reflecting a considerable amount of sunlight and so lowering building cooling loads (see Table 1).

Lighting

Philips ActiLume lights, each fitting of which has three 14 W fluorescent tubes, were installed. Some fittings are master fittings with sensors that detect movement, with 15-minute timers and ambient light sensors. Each master can be linked to and control up to eight slave units. Each individual office has a master unit and some slave units. Typical industry alternative units use between 15 and 20 W/m2, so the 7 W/m2 for the ActiLume fittings is significantly lower. There are virtually no lights with manual switches in the building. Some lighting circuits are on timers and others on photocells. Motion and occupancy sensors in the common areas, basements and ablution sections ensure that lights are switched on only when required. The controlling of lighting through automation in this way is key to energy efficiency.

Ventilation

Building C benefits from the careful use of positioning and orientation, effected to retain as many existing trees as possible. Louvres were also fitted above the top floor balconies to limit heat gain. Shading is considered an important part of design. It decreases the cooling loads of the building and balances the daytime lighting requirements. Building C is equipped with an efficient variable

by using both parametric and non-parametric statistical techniques.

Data collection: shortcomings

Buildings A and B had to be treated as one building (AB) to compare with building C in terms of floor space. Building C has an additional floor and the buildings are not strictly identical to one another. The data collection period was relatively short, when a period of three years would be more appropriate.

The international experience

There is a growing trend internationally towards energy efficient buildings across both the G8 and the BRIC nations. Governments worldwide are committed to employing energy efficient measures in buildings. This includes using advanced building technologies and systems, legislating energy efficient building codes, the promotion of retrofitting and the installation of efficient appliances. In general, however, there is a lack of knowledge on how exactly energy saving technologies will reduce overall building running costs. Critically, the higher cost of installing energy efficient technologies or materials often means that many building owners are reluctant to incur the initial higher expense, especially if they are not going to be owner-occupied.

Measures in building C

Building C was retrofitted in line with the trend in South Africa to adopt energy efficient building measures. This research project sought to determine what these retrofit t ing measures were and what they cost. The project also hoped to establish what the cost/benefit ratio of the installations were by determining if retrofitting had a positive effect on energy consumption. The extent of the retrofitting, the cost of which was R4,3-million and which pushed up the overall cost of the construction by 6,3%, will now be described.

Insulation

To ensure optimum temperature control, high performance thermal double glazing window glass was installed. Glazed windows contribute significantly to a reduction of cooling and heating loads. The glass in CEF House was manufactured locally and used low-electrochromic (E) glass for the inner pane inserted into aluminium frames. External doors were fitted with “door sweeps” to reduce air flow. The building envelope was insulated. Compressed vermiculite sheets seal off the basement from the ground floor. These sheets were also installed under the roof sheeting. In

air volume (VAV) centralised heating, ventilation and air conditioning (HVAC) system using a mounted consol unit instead of the traditional individual split-unit air conditioning system. This allows for better circulation of fresh air, thus reducing CO2 build up. Temperature control is designed between 22 and -2°C. Individual offices have a single temperature control unit while the open plan offices typically have two. There are two chiller units for the server room (one being a backup) to keep the server room at a constant temperature. The operating hours and general temperature settings for the HVAC system are controlled by a central building management system. The basement has no mechanical ventilation.

Elevator, solar panels

The building is equipped with a Kone mono space lift which typically uses 4400 kWh per annum, compared to a hydraulic lift which normally uses about 16 000 kWh per annum. This is partly due to it being 320 kg lighter than a regular lift. In addition, CEF House uses solar panels for hot water requirements. The roof structure was designed to accept a photovoltaic panel array. There are future plans to use 800 m2 of the roof for solar panels. This could provide as much as 20% of the daytime electricity demand once installed.

Generator

Back-up power is provided to the building by a Gentek generator, which automatically adjusts its energy supply to meet the electricity requirement in the case of a power failure. The significant number of power outages in Sandton makes generator ownership essential.

Date AB costs AB kWh C costs C kWh

04/09 R21 008,24 23 066 R28 429,53 42 067

05/09 R21 102,76 23 250 R37 150,59 56 029

06/09 R30 995,05 26 675 R31 809,71 47 471

07/09 R46 720,92 32 098 R70 700,14 55 967

08/09 R57 326,02 40 973 R86 663,36 69 238

09/09 R39 660,19 28 875 R76 275,25 66 960

10/09 R29 659,92 27 033 R70 104,28 83 956

11/09 R31 100,49 28 880 R68 017,44 81 344

12/09 R19 701,87 16 193 R12 651,93 28 232

01/10 R29 357,92 36 365 R32 705,62 86 117

02/10 R25 751,98 28 832 R20 680,16 51 428

03/10 R20 997,67 18 900 R28 429,53 42 067

04/10 R24 303,00 25 805 R28 74066 59 129

Table 2: Summary of energy consumption and costs for building AB and C.

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Energy consumption data

The energy consumption data for buildings AB and C was collected from the meter readers and cost data was collected from electricity bills. This monthly data for building AB and C is indicated in Table 2. Block AB's energy consumption ranged from 16 193 kWh to 40 973 kWh while for building C, the energy consumption ranged from 28 232 kWh to 86 117 kWh per month. The total electricity bill for building AB was R397 686,03 for the period, with building C's bill at R592 358,20. The average daily energy costs for Block AB ranged from R624,64 to R1686,06 and for block C from R341,94 to R2630,18. Total consumption for building AB was 356 945 kWh and for building C it was 770 005 kWh. The average daily kWh usage for building AB is 943,20 kWh, compared to a mean of 1984,14 kWh for building C. Building AB therefore consumed less energy (53% lower) and incurs lower costs (33% lower). However, building AB has a much smaller standard deviation (140,98 kWh) than building C (668,924 kWh). Furthermore, the distribution of average daily kWh scores is distributed more "normally" in building C. It may therefore be that the billed kWh for building AB is not be a true reflection of consumption. Figs. 1 and 2, as well as, Table 2 seem to indicate that there may actually be a serious problem with billing and meter readings, as there is a weak correlation between billing and kWh consumption.

Results: billing and meters

Although the overall cost of the retrofitting is small, adding only 6,3% to the total cost of construction at a sum of R4,3-million, it is highly likely that many building owners will baulk at incurring such costs. Such reluctance will only increase if financing costs are

accounted for. However, building C did include some "nice to haves" in this cost, so if buildings only focus on installing glazed windows, energy efficient lights and insulation, the costs can be reduced to roughly R2,2-million.It was a surprise to find that building C had higher electricity bills and consumption than building AB. Upon investigation, it was found that costs and consumption can be attributed to a number of factors. In terms of billing, the buildings were initially charged by the office park management using flat-rate Johannesburg City Power tariffs. Then, at some point, the tariff for building C was switched over to Eskom tariffs, which are both seasonal and time-of-day related. Thus, it seems that when flat rate billing is used there may be less incentive to retrofit because overall costs in building AB are significantly lower. That said, it seems that switching to time-of-day and seasonal tariffs did help keep costs down in building C. The latter paid R1,00 for every 1,3 kWh consumed, compared to building AB which paid R1,00 for every 0,90 kWh. If building C was charged the same rate as building AB, the total electricity bill would have been R693 004,50, registering a saving of R100 646,30. If this is indeed the savings that can be attributed to retrofitting, it will take 42 years and seven months to recoup the retrofitting costs, assuming that there is no escalation in the kWh rate over that period of time.During the tariff switchover, a meter discrepancy between the recordings of the in-house building C meter and the Eskom meter was discovered. It appears that building C was overcharged, although a refund is still not forthcoming. Further to the investigation, block C electricity charges have subsequently been reduced and CEF House executives now actively manage the account. The meter discrepancy can be attributed to a number of factors. Firstly, the main Eskom

meter was not read between March 2009 and October 2009, so readings were actually estimates. Secondly, consumption for buildings C and another building (D) was amalgamated in the absence of a separate meter. Based on these findings, it was found that consumption and billing need to be managed actively. To actively manage energy consumption and overcome meter reading problems, CEF installed additional meters within the building in December 2009: at basement level; ground level; one for each floor; one for the server chiller room, and one feed-in meter. These meters are linked to the Safari (Johannesburg City Power) meter.Despite all the challenges, it was found that, on average, building C is consuming between 150 and 184 kWh/m2 annualised (mean: 170 kWh/m2). So, the building is using less than the standard for new buildings with a central air conditioner (which is 200 kWh/m2), meaning that, at the very least, the passive energy efficient measures are having a positive effect on consumption.

Results: air conditioning

The impact of air conditioning on energy consumption cannot be ignored. The difference between consumption in buildings C and AB can be ascribed largely to the air conditioner. The HVAC in CEF House was found to be responsible for almost half of total energy consumption, as energy consumption collapses when the HVAC is non operational (which occurs during the somewhat regular Sandton power outages). The control building, building AB, does not have a central HVAC system. Significantly, higher energy consumption is recorded in summer, as more energy is required to cool the building than heat it in winter.Real-time data collection demonstrated that the HVAC must both heat and cool the building at the same time. This is

Fig. 1: Comparing energy consumption in the two buildings in kWh.

Fig. 2: Comparing costs based on billing data for the two buildings.

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due in part to the temperature difference between the north and south facing offices. North facing offices are hotter than the rest of the building, and the HVAC settings have to be adjusted to regulate the difference. Furthermore, it is possible to switch on the west side HVAC later in summer, compared to the east side due to early morning passive solar heating on the eastern side. In addition, different people function optimally at different temperatures; some like their offices to be cooler/hotter than others and so adjust the HVAC manually.Human comfort results in simultaneous heating and cooling of the building, which is energy intensive. However, although the HVAC's automatic settings are based on actual experiences in the building, it is not a perfect system. Public holidays are sometimes omitted from the programmed HVAC schedule unintentionally. From time to time, the air conditioner is not switched back on after a general power failure. Inexplicable failure to manage the system also occurs sometimes. For example, in December 2009, the HVAC was operating 24 hours a day for the first two weeks and then switched off for the rest of the time.

Background, base level, consumption

It was also found that there is a level to which energy consumption cannot be managed down in a modern computer-based office. For building C, this included the server (at around 12 kW, about 33% of night use and 6% of peak demand) fridges and plugs (with items such as printers on stand-by mode), as well as security units.

Discussion

It is clear that retrofitting is costly. Therefore, it is recommended that the South African government consider using tax incentives to encourage owners to adopt them. It is also hoped that, as many more buildings install energy saving technology, the overall prices will come down. However, we found that installing passive energy efficient measures alone may not generate energy savings automatically. The management of the technology and of users is crucial. For building C, the installation of a realtime energy consumption meter reader to capture daily consumption, proved to be invaluable for capturing daily consumption. It is clear that without accurate knowledge of how energy is used (on each floor and for what purpose), consumption will not come down automatically.Another crucial issue is that of billing and tariffs. If South Africa is to encourage building owners to retrofit, then billing

must be by time-of-day and seasonal tariffs. In this regard, building owners are encouraged to install their own meters to verify consumption. However, when selecting meters, attention should be paid to levels of acceptable meter accuracy, with meter error margin not be more than 1%. In building C, the cumulative error margin was occasionally as high as 10% at times prior to electronic metering.Finally, buildings may require "energy champions", individuals who are prepared to do the necessary research and monitoring and to take action to ensure that energy is used efficiently. To achieve energy savings, more emphasis should be placed on developing and operating a building management system to keep track of progress of the energy efficiency interventions and technologies. The suggestion is to start with the highest consuming systems, such as the HVAC. Champions must identify what needs to be metered, get it metered, and then analyse the trends and rectify problems.Energy management resembles an action research project. Installing passive, automated technologies without monitoring and adjusting may not render sufficient efficiencies. Energy building management, therefore, becomes a skilled activity.

Conclusion

We found that to realise energy savings,

a full understanding of a building's energy use is required. Therefore, data collection and analysis of kWh and billing must be ongoing. Computer based energy management systems and accurate meter readings play a major rule in energy efficiency. Passive installations alone may not work. The energy management system must be fully operational in real time, otherwise data is incomplete, hindering the achievement of energy efficiencies. The impact of power outages on the energy management system also needs to be investigated further, as does the relationship between billing and energy consumption. Importantly, if there is a weak relationship between billing and consumption, this will be a disincentive for the adoption of energy saving measures. It is recommended that any building wishing to effect energy savings should focus on developing human resource capacity to manage installations, equipment and implement changes (in real time) when necessary. Metering is essential in this regard.

Acknowledgement

This paper was presented at the AMEU conference, 2011, and is republished here with permission.Contact Takalani Bridget Thovhakale, University of Johannesburg, Tel 082 555-7956, bthovhakale@gmail.com