ORIGINAL ARTICLE

Optimising energy use in an existing commercial building:a case study of Australia’s Reef HQ Aquarium

Sascha Thyer & Severine Thomas &Craig McClintock & Michael Ridd

Received: 26 September 2016 /Accepted: 4 August 2017 /Published online: 6 September 2017# The Author(s) 2017. This article is an open access publication

Abstract Reef HQ Aquarium is a major tourism attrac-tion in tropical North Queensland, Australia. In 8 years,a 50% reduction in grid electricity was achieved throughtargeted infrastructure investment, whilst growing thebusiness. Initially, grid energy consumption was2438 MWh per annum, with 490-kW peak demandand energy intensity of 1625 MJ m−2 year−1 used ontypical equipment such as HVAC (heating, ventilationand air conditioning), machinery, lighting and cateringequipment. Savings of 13% were achieved in the firstyear by increasing indoor air temperature set-points by1.5 °C with no significant costs or impacts on occupantthermal comfort or worker productivity. Peak demandwas decreased by 46% by upgrading the computerisedbuilding management system (BMS), HVAC, machin-ery and lighting; and by installing a 206-kW photovol-taic (PV) solar power system. This case study illustratesthat (a) significant energy use reductions are possible at

low cost; (b) capital investment in energy-efficient infra-structure can have short payback times and high direct andindirect benefits, particularly where equipment is endingits life. This study is unique as it examines how a com-mercial building with integrated chilled water thermalenergy storage (TES) and a 3.2-ML chilled seawateraquarium system can be controlled by a BMS to optimisesolar power to manage peak energy demand and alsoincrease the utilisation of generated PV power in theabsence of electrical battery storage. An interesting build-ing is used to demonstrate efficiency methods with ele-ments such as HVAC and lighting which usually consumeover half commercial buildings’ energy use.

Keywords Building retrofit . Energy efficiency.

Thermal comfort . HVACwith chilled water TES . SolarPV

Introduction

In developed countries, the buildings sector (residential,commercial, and public) uses between 20 and 40% offinal energy consumption (Perez-Lombard et al. 2008).In Australia, the buildings sector represents approxi-mately 23% of Australia’s total greenhouse gas emis-sions (Australian Sustainable Built EnvironmentCouncil 2008). There is evidence that energy efficiencycan have a positive effect on economic growth (VividEconomics 2013) and reductions in commercial build-ings energy use represent an opportunity to reduce glob-al greenhouse gas emissions (Pitt and Sherry 2014;

Energy Efficiency (2018) 11:147–168DOI 10.1007/s12053-017-9556-x

S. Thyer (*) : S. ThomasReef HQ Aquarium (Great Barrier Reef Marine Park Authority),Townsville, QLD, Australiae-mail: sascha.thyer@gbrmpa.gov.au

S. ThyerCollege of Marine and Environmental Sciences,James Cook University, Townsville, QLD, Australia

C. McClintockMcClintock Engineering Group Pty Ltd, Member of EngineersAustralia, Townsville, Australia

M. RiddCollege of Science and Engineering, James Cook University,Townsville, Australia

Levine et al. 2007). As most energy is consumed inexisting buildings within the buildings sector, rapidenhancement of energy efficiency in existing buildingsis considered essential for a timely reduction in globalenergy use (Ma et al. 2012). Total energy consumptionwithin the Australian economy has been falling since2011–2012 despite a growth in the economy, in part dueto increases in energy efficiency (Department ofIndustry and Science 2015). However, more is achiev-able by focusing on existing infrastructure (AustralianSustainable Built Environment Council 2008; Biswas2014). This work aims to bridge the gap between thedemonstration of new energy efficiency models in sci-entific settings, and energy efficiency retrofit measuresapplied by an owner/manager in a real-world settingwhich takes into account the practicalities of an ageingcommercial building and resourcing for retrofit actions.

This study examines an 8-year refurbishment of theReef HQ Aquarium (‘the Aquarium’) which was built in1987 and is the world’s largest living coral reef aquarium.As theAustralianGovernment’s National EducationCen-tre for the Great Barrier Reef, it is a major tourismattraction of tropical North Queensland, attracting over140,000 visitors annually. The Aquarium is federallyowned and funded and achieves greater than 80% oper-ational cost recovery through ticket sales (and educationalrevenue). A suite of energy saving measures was insti-gated and implemented with the aim of reducing gridenergy use by 50%, from low-cost operational measurestomajor capital investment. Such a target has been shownto be theoretically possible (Ardente et al. 2011), but fewcase studies relate to older commercial facilities signifi-cantly reducing their energy use whilst remaining opera-tional. Despite its specificity, the Aquarium has all majorenergy use categories of most buildings such as HVAC(heating ventilation and air conditioning), machinery,lighting, catering equipment, electronic equipment anddomestic hot water. Worldwide, buildings’ energy con-sumption can be up to 70% for HVAC systems andartificial lighting (Colmenar-Santos et al. 2013). TheAquarium is similar to most buildings in that the largestportion energy consumption can be attributed to HVAC.This study adds to work of others by examining the effectof changes to indoor temperature in a commercial build-ing in a tropical location, on a broad range of subjectssuch as tourists, students and workers. This work isimportant as it has been noted by other authors that morestudies are needed to quantify the impact of thermalcomfort on productivity (Rupp et al. 2015).

Despite the excellent conditions for solar photovol-taic (PV) systems, in 2015, renewable energy genera-tion accounted for only 15% of Australia’s total energygeneration, whilst the electricity supply sectoraccounted for 27% of Australia’s energy consumption(Department of Industry and Science 2015). An in-crease in renewable energy systems throughoutAustralia is expected to reduce grid energy use, lifecycle costs for energy generation, transport and trans-mission (Stoppato 2008; Epstein et al. 2011; Garnaut2011). In 2011, the Aquarium installed the secondlargest (at that time) rooftop solar photovoltaic (PV)system in north Queensland, where conditions aregeographically ideal. This study details the program-ming of a retrofitted building management system(BMS) to not only control lighting, machinery, theinternal building environment and an HVAC systemwith integrated chilled water thermal energy storage(TES), but to also optimise the use of solar PV gener-ation. Since HVAC energy demand in most buildingsrepresents a high proportion of power demand andelectrical battery storage for PV power remains expen-sive, this solution may represent a cost effect way tominimise battery storage.

The objective of this study is to examine theefficacy of the methods used for a comprehensiveenergy efficiency retrofit undertaken over many yearsby a commercial building owner/manager. Specifical-ly, the study aims to answer the following questions:(1) can energy efficiency in an older building beachieved at low cost?; (2) were energy audits aneffective measure to facilitate energy efficiency atthe Aquarium?; (3) what was the impact of theAquarium’s retrofit actions on grid electricity con-sumption and what were the most effective mea-sures?; (4) what was the impact of raising indoortemperature set-points?; (5) can a BMS controllingHVAC with integrated TES be used to optimise theuse of dynamic power generation from a large solarPV system? This case study uses an interesting andunusual existing building (a public aquarium) todetail the technical steps taken for the energy effi-ciency measures undertaken, and it evaluates andcompares a variety of energy conservation methodsthat were implemented, in a real-world setting. Manyof these measures (like HVAC, which uses at leasthalf the power in most commercial buildings) couldbe applied to many commercial buildings, publicswimming facilities, and public aquariums.

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Related work

Although there is a significant body of work in thescientific literature on the benefits of energy-efficientretrofits, many case studies are outside the academicliterature. Thus, more practical case studies are neededto demonstrate significant energy saving potential ofbuilding retrofits undertaken by building owners andmanagers to increase the level of confidence in potentialretrofit benefits (Ma et al. 2012; Ardente et al. 2011).There are numerous theoretical studies focused on theenergy analysis of public buildings (Ardente et al. 2011;Fiaschi et al. 2012; Steinfeld et al. 2011) and models topredict energy savings for buildings (Aljami 2012;Rysanek and Choudhary 2013; Woo and Menassa2014) including those in tropical Australian climates(Rahman et al. 2010). Few studies currently report onother commercial and industrial buildings (Markis andParavantis 2007), and formal targets, guidelines, toolsand government regulation are still lacking for a largebulk of building stock (Australian Government,Department of Climate Change and Energy Efficiency2012; New South Wales Office of Environment andHeritage 2016; Saddler 2015).

Whilst there is a large body of work describing theuse of TES systems for demand-side management (seereview by Sun et al. 2013), only two recent studies detailthe impact of integrated control of PV and ice thermalenergy storage using energy modelling tools (Wang andDennis 2015; Sehar et al. 2016) and one described theuse of surplus wind energy and thermal storage (Xydisand Mihet-Popa 2016). This study is unique as it exam-ines an end-user-operated direct digital control (DDC)BMS that controls HVAC with integrated chilled waterTES, and the chilling of a large 3.2-ML aquarium tank,in order to optimise solar PV energy generation use inthe absence of electrical battery storage.

The International Performance Measurement andVerification Protocol 2012 (IPMVP®) (EfficiencyValuation Organisation 2012) is used in this study asthe principal method for measurement and verification.Alternative methods are also available such as theASHRAE Guideline 14 (ASHRAE 2014) and ISO17741:2016 General technical rules for measurement,calculation and verification of energy savings of projects(International Organization for Standardization (ISO)2014). The AS/NZS 3598 Energy Audit series(Standards Australia 2014) and ISO 50001:2011 EnergyManagement Systems (International Organization for

Standardization 2011) provide guidance on audits andenergy management systems, respectively.

Methods

Building description

The Aquarium is located in the city of Townsville(19.2577° S, 146.8238° E), which has a meanmaximumsummer temperature of 31.3 °C with an average relativehumidity in summer of about 70% (Bureau ofMeteorology 2015). The entire usable building spacefor the Aquarium, including service and outdoor storageareas, is ca. 5400 m2. Of this space, 2345 m2 is airconditioned and 775 m2 is covered by the two mainAquarium tank systems shown in Fig. 1 (ca. 4 millionlitres of chilled seawater in total). Most aquarium tanksare maintained below 28 °C for optimum marine lifepreservation and coral health.

Main energy use categories

Energy consumption at the Aquarium can be split intofive key categories:

HVAC: (refrigeration and no central heating; thecommon HVAC acronym is used) cools publicand office spaces during opening hours and nightfunctions 365 days every year and cools 4 ML ofaquarium water as required and a 20-kL chilledwater TES.Machinery: filtration pumps that operate continu-ously, compressors running sporadically (for wavemachine and SCUBA diving) and a reverse osmo-sis system operating seasonally.Lighting: standard room lighting, special displaylighting and high-intensity lighting for corals andplants.Café: catering equipment such as refrigerators,freezers, warmers, dish washer and chip fryers.Other: passenger elevator, electronic and audio-visual equipment, computers, photocopiers, lifesupport system monitoring devices, workshoptools, low flow pumps, small aquarium heaters(small winter heating requirement), ozone genera-tors, and other ancillary aquarium tank devices.

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Energy use and costs data analysis

Year 0 (1 July 2005 to 30 June 2006 as per the Austra-lian financial year) is set as the baseline year prior to therefurbishment period and subsequent financial years arenumbered sequentially (year 1 to year 8 of refurbish-ment). All financial costs are in Australian dollars ex-cluding GST (goods and services tax) as the Aquariumis GST exempt. Cost of electricity is the actual amountbilled by the electricity provider (Ergon Energy). Themodelled scenarios (i.e. estimate if no efficiency actionwas taken) are calculated using the energy provider’stariffs in each year.

The IPMVP® (Efficiency Valuation Organisation2012) was used to analyse energy use and savings.IPMVP® Option C, Whole Facility, was used to com-pare the overall energy use between years, using halfhour meter data provided by the grid energy provider.Separate energy-using elements were analysed with acombination IPMVP® Option A and B as describedin detail in the ‘Audits and retrofit process and energyreduction target’ to ‘Integrated rooftop solar PV sys-tem’ sections. The proportional use of the five energyuse categories was compared before and after refur-bishment by taking point-in-time current transformerreadings from electrical distribution boards in De-cember of year 0 and year 8. Energy meters (Cromp-ton Instruments Integra 1630) provided kilowatt hourdata on HVAC and cafe electrical loads. Where equip-ment was at the end of its life, only the additional cost

of the energy-efficient measure against the business-as-usual replacement was factored into the paybacktimes and overall savings (although total replacementcost is also shown in the results). Payback forecastswere calculated using electricity prices from the Aus-tralian Energy Market Operator (Frontier EconomicsPty. Ltd. 2015). Labour rates were calculated usingthe average hourly rate of staff who would normallyundertake the work. All financial costs include 5%discount rate; for future years, electricity and mate-rials costs include a 5% escalation; and labour costsinclude a 3% escalation. A marginal abatement costanalysis was undertaken for five energy use catego-ries and a sub-category ‘Operational’ (part of the‘HVAC and HVAC related’ category) was also shownseparately to examine the impact of measures withminimal cost. The conversion of kilowatt hour tocarbon dioxide equivalent (CO2-e) was calculatedusing the Australian Government National Green-house Account Factors (Depar tment of theEnvironment, Commonwealth of Australia 2014).The emissions factor for ‘scope 2’ (emissions fromdirectly burning fossil fuels) is 0.81 t CO2-e MWh−1

for the Queensland (Australia) end user. If the emis-sions factor for ‘scope 3’ is also included, the value is0.94 t CO2-e MWh−1. This factor is an estimate ofindirect emissions from the extraction, productionand transport and power loss through the distributionnetwork. Both of these methods are applied in the‘Life cycle savings and C02-e avoided’ section.

Fig. 1 Reef HQ Aquarium, viewfrom above showing solarphotovoltaic system and two largeopen-topped aquarium tanks

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Audits and retrofit process and energy reduction target

An internal energy audit was conducted in year 0 by theAquarium’s senior technical staff, with the aim of iden-tifying areas of energy use inefficiencies. Six externalfirms were engaged in years 2 to 4 to investigate oppor-tunities and feasibility of energy conservation proposals.The scope of each varied greatly. Using the combinedaudit reports, a wide range of potential retrofit actionswere considered, cost-benefits were assessed, then thelist of retrofit actions were narrowed and prioritisedbased on a balance of practical considerations such as(a) predicted power use reductions, (b) ease of imple-mentation, (c) cost, payback times and funding arrange-ments, (d) internal versus external expertise and labourrequirement, (e) other benefits aside from energyminimisation and (f) impacts on the visitor experienceor disruptions to the animal life support systems. As-sessment of possible energy use reduction following theinternal audit led a reduction target of 50% over 5 yearsfrom year 1.

The main drivers for energy use reduction initiativesat the Aquarium were a willingness to support the use ofnew high-efficiency equipment that underpin environ-mentally sustainable business practices (Great BarrierReef Marine Park Authority 2007), economic pressure(rising electrical prices) and concerns about the impactsof climate change on the business and the Great BarrierReef. Conversely, prior to 2005, relatively low electricityprices and limited availability of high-efficiency equip-ment fostered a culture of low capital investment andminimal focus on life cycle costs of equipment. A De-mandManagement Pilot Programme offered by the localelectricity supplier Ergon Energy provided an additionalincentive and formalised the focus on reducing peakpower demand. This including a financial incentive forevery kilowatt of peak power demand reduced. The ReefHQ Aquarium agreed to aim to reduce its 490-kW peakpower demand by 230 kW. Ergon Energy engaged aconsultant to measure the peak energy demand savingsfor the demand management programme years, and tookinto account historical weather data and adjusted forchanges in HVAC loads. The Ergon Energy meter datawas analysed by the consultant using the IPMVP® Op-tion C, Whole Facility, Eq. 1B (Efficiency ValuationOrganisation (EVO) 2012). This analysis examined onlythe peak demand only over a 6-month period (peakdemand summer period) from August 2012 to February2013, against the baseline peak energy.

Audit benefits were measured by: (1) whether thereports were of a quality that could be used for fundingproposals; (2) new and innovative content (i.e. not al-ready proposed by Aquarium staff); (3) the volume ofrecommendations taken up by the Aquarium with goodoutcomes and (4) how the models in the reports com-pared to actual outcomes for measures taken up.

Indoor temperature changes and thermal comfort survey

In year 0, all AHUs were set to cool the Aquarium spacedown to 23.0 °C throughout the year, at 60% relativehumidity and 0.12 to 0.26 m s−1 air flow 3 m away fromducted air vents. Early in year 1, the indoor temperatureset-points were raised by 0.2 °C increments over3 months until all air-handlers were set at 24.5 °C. Halfhour energy use was measured for the year before andafter the change and routine visitor surveys were col-lected and reviewed for the year preceding (670 sur-veys) and following (970 surveys) the set-point change.No questions related directly to thermal comfort, butcomments relating to infrastructure and different aspectsof comfort in the facility were routinely received in anopen field in the survey. Visitation during the yearbefore and after the change was measured through ticketsales and data retrieved from a computerised point ofsale system (SwiftPOS™ software). Aquarium facilitiesstaff reported that they had received some complaintsfrom staff about indoor temperature initially, but thesecomplaints diminished over time (anecdotal evidence).The suggestion was that occupants may have adapted toa higher temperature over time. For this study, theanecdotal evidence that the impact of the change wasminimal was tested in May 2016, by examining theimpact of an indoor temperature change on comfortand productivity using a thermal comfort survey. Thesurvey simulated the 1.5 °C temperature change under-taken in year 1, and recorded the thermal comfort re-sponse on all categories of human occupants (visitors,Aquarium staff and volunteers and staff from the adja-cent Great Barrier Reef Marine Park Authority(GBRMPA) offices). For worker occupants, self-assessed productivity whilst in the Aquarium was alsoexamined. The indoor set-point was set at 23 and24.5 °C on alternate days for 2 weeks (14 days) and allstaff and volunteers were encouraged to complete thesurvey twice on two different set-point days, whichwerearbitrarily identified as a ‘green day’ and a ‘yellow day’to avoid potential bias. The questionnaire asked: (i)

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one’s clothing level (light, moderate and high); (ii) ther-mal sensation (cold, cool, neutral, warm, hot); (iii) andthermal comfort (very uncomfortable, moderately un-comfortable, slightly uncomfortable, slightly comfort-able, moderately comfortable, very comfortable).

The statistical interpretation of the survey results wasundertaken using the Statistica 13 package (StataCorp2013), and scales of comfort and productivity wereconverted to a numerical scale. An assessment ofworkers’ productivity was obtained by workers self-assessing their efficiency at the time of the survey inrelation to their average efficiency (clearly above, slight-ly above, at my average efficiency, slightly below, clear-ly below) (Kekäläinen et al. 2010). An independentsamples t test was used to assess the statistical differencein responses at the two different temperature set-points,using a significant level of p < 0.05. For data that wasnot normally distributed, and could not be transformedto achieve normality, a non-parametric Mann-WhitneyU test was undertaken. A factorial ANOVAwas under-taken on the comfort responses with the two factorsbeing temperature (either 23 or 24.5 °C) and respondenttype (Reef HQ staff, volunteer, GBRMPA staff andvisitor) followed by Tukey HDS test. Air temperaturewas logged during the survey period by the BMS (usingReliable Controls™ SPACE-Sensor Temperature), av-eraging temperature from three sensors for each AHUarea. Outside humidity and temperature were alsologged by the BMS. The airflows through the AHU airvents were checked to ensure they were consistent withthe commissioned data for the HVAC system.

HVAC, TES and BMS

HVAC consumed about 50% of energy use in year 0 andwas highlighted in the internal audit and a technicalaudit as having significant opportunity for efficiencygains. The original HVAC system consisted of two air-cooled chillers (total 600-kWr power) and two alternat-ing 30-kW pumps running continuously. The technicalaudit reported poor circulation around the air-cooledchillers, maintenance issues, inefficient and unbalancedhydronic system configuration, inefficient air side sys-tems (deviating up to 30% from design values) and anegative building pressure, drawing excessive hot out-side air into the air-conditioned space; the chillers wereinefficient with an average system coefficient of perfor-mance (COP) of 2.4, and excessive start and stop of thechillers (20 times per night). Although the system was

only 9 years old with a usual lifespan of 12–15 years, thehot, humid and corrosive aquarium environment com-bined with a high-load and inefficient design had left itin poor condition, leading to a replacement of the chill-ing plant itself. A state-of-the-art, modular, high-efficiency water-cooled multi-chiller solution wasinstalled with a long predicted lifespan. Three Hitachitwin screw-type chillers (RCUP67WUZ model; contin-uous digital control between 15 and 100%; capacity236 kWr; 4.55–5.86 efficiency at 100% load) andmulti-pump system were chosen to allow for redundan-cy and adjustment to a minimum load and for peakpower demand management. A base load 20 kL chilledwater TES tank was installed to decouple the primaryand secondary pumping groups and prevent excessivechiller starts. The TES operating range is 6–15 °Cwith atemperature differential of 9 °C. Previously, the chilledwater systemwould cool the building as well as 4ML ofseawater in the exhibits simultaneously day and night.The energy use efficiency achieved by the upgrade ofthe HVAC and addition of the TES tank was assessed byquantifying the increase in chillers average COP, theaverage number of chiller starts per night, the reductionof HVAC power consumption and effect on peakdemand.

Heat load on the HVAC system was reduced with (a)replacement of lights and pumps with more energy-efficient versions; (b) a reflective roof coating appliedto the corrugated roof and (c) replacement of ca. 88 m2

of single glazing with deteriorated low-quality windowtint with double-insulated argon-filled low-e glazing(Viridian Glass argon-filled insulated glass unit withEVantage™ tint). The measures could not be isolatedfrom each other, so they were consolidated into thecategory ‘HVAC and HVAC related’ whose consump-tion could accurately be measured through HVAC ener-gy metering in the BMS.

Prior to refurbishment, the HVAC was controlled bya simple direct digital control (DDC) system that wasunderutilised to only control time schedules, the propor-tional flow of chilled water to the air handling units(AHUs) and stop/start two air-cooled chillers and twochilled water pumps. Amore sophisticated but end-user-friendly DDC system was installed using ASHRAE™standard BACnet™ protocol, incorporating fully pro-grammable peer-to-peer building controls allowing so-phisticated control of chillers and associated equipment,AHUs, the internal environment, the integrated TES,aquarium tank chilling and peak power demand from

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the grid through load shedding. The BMS also monitorsoverall power use and power use of selected systemsand equipment and can control and schedule powerloads of other power using systems such as aquariumlife support systems. No export of power back to thegrid is allowed by the energy provider and as an addi-tional precaution they imposed (see the ‘Integrated roof-top solar PV system’ section) that a mandatory gridprotection device (Woodward MC4A grid protectionrelay) must shut down inverters to prevent grid demandless than 8 kW. Due to the high cost of finer control, theprotection device shuts down in 50-kW sections. Toprevent inverter shutdown and potential wastage of solarPV power, more complex algorithms were added to theBMS to manage the uncertainty of solar PV generationwithin user-defined thresholds, by limiting chilling or byautomatically designating chilling priorities between theAHUs, aquarium tanks and TES. Within user-definedthresholds, it can bring forward a chilling requirementbeyond the optimal aquarium tank set-points to maxi-mise the use of solar power or delay the chilling require-ment when the chilling requirement is not critical tomanage peak demand. The aim is to reduce the chillingrequirement in peak energy demand periods when thePV generation drops off, and ensure minimal wastage ofPV generation. The system uses classic local-loop con-trol techniques that consist of on-off control of pumpsand chillers and proportional-integral-derivative (PID)feedback control of chilled water through valves andwith rule-based algorithms with ‘If-Then rules’ and‘Fuzzy-logic control’ to prioritise chilling and energymanagement (see Yu et al. 2015 for a review anddescription of control strategies for buildings with TES).

Using the solar power inverter data, which is collect-ed in 15-min intervals, the PV generation wastage wasestimated by totalling the estimated lost power fromeach grid protection event (i.e. the amount of surpluspower generated) for 1 year from September 2015. Thedata is not a direct measure of surplus power (rather anestimate of likely output in the absence of grid protec-tion event) as the wasted power could not be preciselycalculated for this study.

An algorithm to delay discharge of the TES wasintroduced in 2016 and analysed for 7 days in Septem-ber 2016 to determine if the chilling load could bemaintained above the threshold that would trigger thegrid protection device. The savings in power were com-pared to the cost of storage of electrical power using anelectrical battery storage solution.

Machinery and lighting energy efficiencyimprovements

Aquarium pumps and compressors rated up to 37 kWused approximately 40% of the power in year 0. Energyuse audits reported that purchasing of machinery washistorically based on capital cost, quality and durabilityin the corrosive Aquarium environment, but not onpower consumption, resulting in many pumps beingover-sized for their application. The filtration systemswere reviewed by Aquarium staff and an external tech-nical audit. Subsequently, filtration piping wasredesigned to maximise efficiency and pumps and asso-ciated motors were replaced with more efficient models.The reverse osmosis machine used to remove freshwaterfrom the Coral Reef Exhibit during heavy monsoonalrains used high-pressure, high-energy use pumps. Sincethis systemwas at the end of its life, it was replaced witha high efficiency model. For static load equipment suchas pumps, point-in-time load readings from distributionboards were recorded by an electrician before and afterthe retrofit actions. The kilowatt - hour energy use ofindividual equipment and systems was then calculatedusing average duration of operation per day (mostpumps run continuously).

Dilapidated skylights and some high-intensity floodlights were replaced with engineered skylights(Solatube™) which minimise infrared light. Plasmaflood lights and high-intensity LED lights replaced in-efficient metal halide lights and general lights werereplaced with LED lights. The fixed electrical consump-tion of lights was calculated using the manufacturer’sspecified power consumption multiplied by the timeschedule or average hours per day the equipment wasin operation.

Two of the energy-efficient audit reports suggestedthat air leaks on systems using compressed air wereleading to energy wastage, and subsequently, the wavemachine compressor system (part of the life supportsystem for the main Coral Reef Exhibit) was adjustedto address inefficiencies and leaks. The energy con-sumption of the wave machine was monitored in theBMS.

Integrated rooftop solar PV system

A 206-kW rooftop solar PV power system (shown inFig. 1) was built to minimise peak power demand,overall grid power use and switch to a sustainable

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source of power generation. The system was sizedwithin the limitations of available roof space, budgetand the Aquarium’s daytime power needs. A feasi-bility study of a large solar power system at theAquarium predicted a 4.6 kWh per day per kilowattof solar power installed (it modelled a 148-kWpsystem). The solar PV feasibility models were com-pared to actual cost benefit data, and the actualperformance and output of the system. Solar gener-ation data is logged automatically using energy dataloggers (SMA Solar Technology WebBox™). Forthe purpose of calculating the energy saving of thesolar PV system, a scenario without the solar PVwas modelled, by adding the solar generation to thegrid energy use, to determine the peak energy loadin this scenario.

Results

The 50% target was almost achieved by the end ofyear 7 (46%), and exceeded in year 8 (52%), shownin Fig. 2. The sequence of implementation was basedon the prioritisation criteria described in the ‘Auditsand re t rof i t p rocess and energy reduc t iontarget’section and is shown in Table 1 and Fig. 2.

Total energy consumption

Figure 2 shows the impact on power use of the mainretrofit elements. For year 0, the overall baseline gridenergy consumption for the whole site was 2438 MWhand peak demand was 490 kW (551 kVAwith an aver-age power factor of 0.89). Baseline energy was22 kWh visitor−1 year−1 (energy use per visitor) and1625 MJ m−2 (451 kWh m−2 year −1) at a cost of$211,725 year−1 (2006 tariffs). The cost of adopting noenergy-efficient measures is illustrated by the point‘Adjusted baseline power use at 2015 price’ in Fig. 2.I t shows the actual base l ine power use of2348 MWh year−1 plus 286 MWh year −1 associatedwith growth of Aquarium assets and animal life supportsystems. This includes 14 MWh year −1 for extra airconditioning split systems and new exhibit cooling,211 MWh year −1 for additional pumps and61 MWh year −1 for chilling the main aquariums by anextra 1.5 °C in the hotter months. Other factors probablyadded to energy consumption including increased visi-tation, a new 60-person conference facility, additional

lighting and new electronic equipment for new exhibitsand any increase in ambient air or sea surface tempera-tures. It was not possible to obtain precise data for thesefactors so they are not included in the baseline poweradjustment. In 2015, the adjusted energy use wouldhave cost $500,808 year −1 (the unadjusted baselineenergy use would cost $471,610 year −1). Overall gridenergy consumption was reduced to 1160 MWh by year8 representing an energy intensity of 773 MJ m −2 or9 kWh visitor −1 year −1.

Total cost versus total savings and distribution of energyuse categories

Table 1 summarises the efficiency actions and cap-ital investment that led to a 52% reduction in gridsupplied power use by year 8 (that was maintainedat 50% in the following year). The $374,646 savedin electricity and maintenance costs in year 8 repre-sents 10% of the total Aquarium operating expendi-ture for that year. Between years 0 and 8, $1.7M wasspent on energy efficiency measures and $1.25Mwas saved. These savings are significant given thatthe majority of the capital investment was expendedin years 6, 7 and 8 on the two largest initiatives:HVAC upgrade and solar power station. Completepayback for all measures should be achieved in2017. The saving calculations include the following:avoided electricity costs; solar power generation;large-scale generation certificates (LGCs) createdwith the Australian Clean Energy Regulator (usingLGC market price of $75/MWh in February 2016(Green Energy Markets 2016)); decreased labourcost due to reduced maintenance; and the avoidedcost of spare parts and replacement pumps.

Figure 3 shows the shift in the distribution ofpower use between the main categories betweenyears 0 and 8. HVAC and machinery represented atotal of 95% of the energy use prior to the refur-bishment period. The HVAC upgrade and adjust-ments significantly reduced its energy use relativeto other categories. The dramatic reduction inpumping energy made for existing equipment wassomewhat offset by new pumps and enhanced lifesupport systems. The category ‘Other’ increasednoticeably due the increase in digital displays, pro-jectors, ozone generators, UV sterilisers and com-puters (see the ‘Discussion’ section).

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Audits and minimal cost operational changes

The internal audit highlighted some energy inefficien-cies that were addressed immediately (shown inTable 2), leading to a 13% reduction in energy usefor a cost of $6500 in year 1. Of the seven externalaudits, two were funded from the Aquarium’s opera-tional funding, two from other GBRMPA sections partof wider audits and three associated with the DemandManagement Pilot Programme (so only the exact costthe reports funded by the Aquarium could be reportedin Table 1). Three of the reports focused on workshopswith Aquarium staff to synthesise and documentexisting in-house information. Four audits providedhighly specialised advice on technology, budget plan-ning, modelling and key long-term strategies andM&V with enough detail and quality to be used in

future asset life cycle planning. The most expensivereports did not lead to the most significant benefits.

HVAC upgrade and control

Indoor temperature adjustmentIn year 1, the indoor temperature was raised by

1.5 °C and the energy savings are included in the 13%reduction shown in Table 1. General satisfaction surveysof the Aquarium collected in years 0 and 1 reflected nochange in the number of comments on visitors’ thermalcomfort and there was a steady rise in visitation from109,000 in year 0 to 140,000 in year 9.

The year 9 thermal comfort survey supports the an-ecdotal evidence that there was no significant differencein thermal comfort of occupants as a result of the indoortemperature change. During this survey period, indoor

$0

$100,000

$200,000

$300,000

$400,000

$500,000

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

0 1 2 3 4 5 6 7 8 9

MW

h gr

id e

lect

ricity

use

d

Retrofit Action by year

Electricity use

Electricity cost

2014/15Down 50%

Operat

ional

chan

ges

Lighti

ng

Compre

ssors

/ solar

hot w

ater

Heat e

xcha

ngers

/ pum

ps

Solatub

e sky

lights

HVAC / sola

r

Solar p

hase

2

Solar p

hase

2 / dou

ble gl

azing

MWh usedTarget MWh

Adjusted baselinepower use at2015 price*

Cos

t of e

lect

ricity

Fig. 2 Power use (primary y-axis) and power cost (secondary y-axis) per year (x-axis), and showing the main retrofit actions byyear (x-axis).The asterisk indicates calculation included the

baseline power adjustment for additional power use of additionalequipment. See the ‘Total energy consumption’ section for moredetail

Energy Efficiency (2018) 11:147–168 155

Tab

le1

Listo

fenergy

conservatio

nmeasurestakenbetweenyears0and8,costandeffecton

electricity

use

Financialy

ear

06/07

07/08

08/09

09/10

10/11

11/12

12/13

13/14

Cost$

1000s

Com

ments

Savingsfrom

baselin

ein

year

8Projectyear

12

34

56

78

Operatio

nal

1Operatio

nalchanges

00

00

00

00

Nil

Shut

doors,disabled

plant

319MWH/yearitems1–7lead

to13%

kWhsavingstotalfor

year

12

Indoor

airset-pointchanges

0Nil

From

23up

to24.5°C

3Im

proveHVACmaintenance

0Nil

Contractorsupervision

4Sk

ylights,windowtin

tingb

6.5

6.5

Windowtin

tingFeb2007

5Rectifyairleaks

0Nil

Includingdoor

curtains

6BasicBMS

0Nil

Algorith

msto

controlloads

7Walk-in

freezercurtain

0.5

0.5

910MWh/year.

HVAC-related

66%

less

HVACMWh(includes

behavioural)

8Efficient

heatexchangersb

100

100

Fortank

water

cooling

9High-efficiency

HVACb

136

136

Total$

791,500

10Reflectivecool

roof

paint

5656

Metalroof

undersolarPV

11Doubleglazingb

6060

June

2014

(total$143,300)

Machinery

12Wavemachine

efficiencies

0.3

0.3

Airleaks,plantadjustm

ent

Unknown

13New

dive

compressorb

1717

Highefficiency

601kW

h/year

475MWh/year

total3

7%less

machinery

MWh

14Efficient

reverseosmosisb

8.4

08.4

6-kW

saving

(total$91,600)

15New

pumpmodels—

small

57103

Dec

2009

New

pumpmodels—

large

46Feb2009

16Filtrationsystem

changes

2.0

2.0

53labour

hat$38/h

Lighting

17Naturallig

hting(solatubes)

4.3

9.3

5.5

19Replacing

metalhalid

es34

MWh/year

40%

less

lightingMWh

18Energy-efficientL

EDs

245.1

1.9

31MostL

EDinstalled2009/2010

19Plasmalig

hting

3.1

3.1

Aquarium

lighting

Powergeneratio

n

20So

larPV

523

571

331127

Installedyears7and8

300MWh/year

Other

21Energyaudits

3737

5auditsfrom

fundingoutside

theAquarium

22So

larhotw

ater

system

b5.4

5.4

Dec

2008

Unknown

23Audio-visual

Nodata

New

low-pow

erLEDTVs

156 Energy Efficiency (2018) 11:147–168

air temperature remained relatively stable for surveyareas at the two set-points: between 23.0 and 23.6 °Cfor the 23 °C set-point, and between 24.5 and 25.1 °Cfor the 24.5 °C set-point. Indoor relative humidity variedbetween 55 and 65% (outdoor relative humidity 77–92%), due to large volume of evaporation from open-topped aquariums. Fixed airflows were confirmed at0.12 to 0.26 m s−1 at 3 m from the ducted air vents.For the 552 surveys collected, 88% stated clothing aslight and more than 80% rated thermal comfort as com-fortable under both set-point conditions, consistent withASHRAE 55 Standard Predicted Mean Vote and Pre-dicted Persons Dissatisfied (PMV-PPD) for five param-eters (clothing level, activity, humidity, temperature,airspeed) at each set-point using the ASHRAE Standard55-2010 Thermal Comfort Tool (Huizanga 2010).

For all statistical tests applied to the data in Figs. 4and 5, the significance thresholdwas set at 0.05. Figure 4shows the mean comfort score declined from 4.91(SD = 1.13, n = 286) to 4.74 (SD = 1.19, n = 266) astemperature increased. An independent samples t test ofthese data showed no significant difference in the com-fort data for the two set-points (t(550) = 1.74, p = 0.082).Since the data was not normally distributed nor could betransformed to achieve normality, a non-parametricMann-Whitney U test was undertaken. This test con-firmed that the comfort rating at 23 °C (median = 5) wasnot significantly different to that at 24.5 ºC (median = 5),U = 34,864, p = 0.076, r = 0.08.

Figure 5 shows data for the 233 respondents whowere in Reef HQ for the purpose of work. It was foundthat the mean productivity score increased marginallyfrom 3.127 (SD = 0.686, n = 118) to 3139 (SD = 0.634,n = 115) which was confirmed to be statistically insig-nificant by a t test of the normally distributed dataset(t(231) = 0.139, p = 0.89). A Mann-Whitney test con-firmed that the productivity rating at 23 °C (median = 3)was not significantly different to that at 24.5 °C (medi-an = 3), U = 6717, p = 0.86, r = 0.04. A factorialANOVA undertaken on the comfort responses with thetwo factors being temperature (either 23 or 24.5 °C) andrespondent type (Reef HQ, Volunteer, GBRMPA andvisitor) showed the main effect of temperature yieldedan F ratio of F(1544) = 0.86, p = 0.35 confirming thatthe effect of temperature was not significant. The maineffect for respondent type yielded an F ratio ofF(3544) = 4.51, p = 0.0039 showing that responsesbetween respondent types were significantly different.The interaction effect was non-significant, with an FT

able1

(contin

ued)

Financialy

ear

06/07

07/08

08/09

09/10

10/11

11/12

12/13

13/14

Cost$

1000s

Com

ments

Savingsfrom

baselin

ein

year

8Projectyear

12

34

56

78

Operatio

nal

Gridpower

savingsfrom

year

0—%

1314

11a

2125

2746

5250%

in2014/2015

Totalg

ridelectricity

used

inMWh

2120

2092

2179

1918

1826

1774

1304

1160

Baseline—

2438

MWh,year

0

SolarPVsystem

generation(M

Wh)

152

260

301MWhfor2014/2015

Totalcapitalspending1000sAU$

6.5

2423

254

9.3

720

573

931712

$1.7M

forallretrofitactions

Totalcosto

fprojectisincluded

inbracketsin

thecommentscolumn

aThisdrop-backcanlargelybe

attributed

toadditio

nof

newmachinery

(63MWh)

andsplit

airconditioners(added

2007)

bEquipmentatend

oflifeandonly

additio

nalfunds

forenergy-efficient

optio

nareincluded

inthecostcolumn

Energy Efficiency (2018) 11:147–168 157

ratio of F(3544) = 0.45, p = 0.716. A Tukey HSD testshowed that the GBRMPA staff and the visitors, whoreside in the Aquarium for a relatively short period oftime, showed the greater change in comfort perceptionto Reef HQ and volunteers who generally reside in theAquarium all day. No clear conclusions could be drawnfrom this result.

Major upgrade of the HVAC system including TESand BMS

The TES tank provides up to 4 h of thermal storageand it minimised chiller starts from ca. 20 per 24 hday all year, to 3–6 per 24 h day (depending on theseason). The system also has significantly greaterefficiency, with an average 4.8 COP for the newchillers and variable speed drives on the pumps thatallow for the most efficient use of pumping power.

The system is able to run on only one of the threechillers for approximately 7 months of the year. TheBMS control of the TES tank allows the load to bespread more efficiently by prioritising cooling to thebuilding and then redirecting any spare cooling ca-pacity into the TES tank and to aquarium tanks. Itshifts and delays chilling loads which compensatefor unpredictable energy generation. User-definedtrigger points for the process allowed trial and errordetermination of the correct set-points that allow forfast changes in PV generation (e.g. on a partlycloudy day) and slower valve response times. Themethod of chilling of the large 4-ML aquariums(timing and degree of chilling) has a significanteffect on the peak demand. Tests showed that with-out intervention of the BMS algorithms, chilling ofthe Reef Tank alone leads to a 100-kW higher peakdemand, under minimal PV generation conditions.

Table 2 Issues identified by the internal audit in year 1 and subsequent operational measures taken

Auditreference

Quality acceptable tofunding applications

New measures ortechnical detailsuggested (%)

New measuresadopted (%)

Report modelsaccurate against actual

Outcomes for newmeasures adopted

Audit cost(all but D paidfor by others)

Internal No 100 100 n/a Good $0

A No 20 10 Partly Poor $10,000

B No 0 0 n/a None $28,000

C No 0 0 No None $42,000

D Yes 30 30 Mostly Good $27,000

E Yes 100 100 Yes Good $10,000

F Yes 100 100 Yes Good $10,000

Year 0 (2006)

Machinery, 1,086HVAC related, 1,212

Other, 24Café, 31

Lighting, 86

HVAC related Machinery Lighting Café Other Power use Savings

Year 8 (2014)

Machinery, 696

HVAC related, 416

Other, 217

Café, 40

Lighting, 52

Power use Savings, 1,303†

Fig. 3 Distribution of electricity consuming categories before(left) and after (right) the refurbishment period, shown in MWh.The baseline in 2006 is the actual baseline (2438 MWh). The totalenergy used in 2014 (1421 MWh) includes the grid energy

(1160 MWh) and solar power (260 MWh). Dagger indicates thatsavings in 2014 take into account the adjusted baseline (‘Totalenergy consumption’ section)

158 Energy Efficiency (2018) 11:147–168

When the energy supplier’s mandatory grid protec-tion trigger point is reached (8 kW), the grid protectiondevice shuts down the solar power system in sections toprevent any export of power to the grid. PV inverter datashowed these events occurred frequently (numeroustimes a week or up to three times a day) and the powerwasted is estimated ca.25,000 kWh/year or approxi-mately 7.6% of the total yearly yield. In the absence ofthe algorithm to directly prevent discharge of the TES(as previously described), the algorithm to prioritiseReef Tank cooling during peak PV generation periods(the ‘HVAC, TES and BMS’section) was observed (inthe hotter period between October and April 2016). The

algorithm was regularly activated (2 to 6 times perweek) and showed that the occurrence and duration ofthe TES discharge could be minimised with only occa-sional discharges during PV generation hours leading togrid protection device activation. The PV wastage andwastage avoided could not be precisely quantified, but itwas observed that the algorithm was activated 4–6 timesper week during the months that Reef Tank cooling wasrequired, indicating that the algorithm was regularlystoring cooling energy that would otherwise be wasted.

The Reef Tank cooling algorithm is only used in thesummer months when the tank temperature rises beyondthe 27 °C set-point. Consequently, analysis of the data for

Fig. 4 Mean comfort rating as afunction of indoor temperature.Numerical scale in brackets (x-axis)

Fig. 5 Mean self-assessedproductivity rating as a functionof indoor temperature. Numericalscale in brackets (x-axis)

Energy Efficiency (2018) 11:147–168 159

August 2016 (cold month with no tank chilling) with noBMS intervention indicated ca. 2700 kWh power wastedwith 25 occurrences for the month. The algorithm todelay discharge of the TES was introduced and analysisof 7 days in September 2016 showed that the algorithmwas able to maintain the load above the threshold thatwould trigger the grid protection device. The algorithm toprevent discharge of the TESwas triggered every day thatweek, and no activation of the grid protection device wasrecorded.Whilst more data is required to quantify the fullimpact of this measure through the seasons, we canconclude that it is possible to directly prevent the TESfrom discharging at its usual temperature set-points toavoid activation of the grid protection device, whichavoids wastage of surplus PV generation and optimisesHVAC use. No data is yet available for the combinationof the Reef Tank cooling algorithm and the delay of TESdischarge algorithm. This combination may avoid all PVgeneration wastage.

A budget estimate for supply and installation 91-kWh bi-directional UPS (ininterruptable power supply)battery system using lithium batteries, all componentsincluded is ca. $200,000. This could accommodate25,000 kWh per year of energy storage.

For the glazing, only manufacturer’s data was avail-able that states the double glazing u value is 2.7 W m−2

compared to 5.8 W m −2 for the single-glazed panels (nodirect impact data available).

Lighting and machinery energy efficiencyimprovements

Total lighting power use was reduced by 40% from thebaseline power use (Table 1), representing 34MWh year−1. In total, power use for machinery (all pumps exceptHVAC pumps) was reduced by 37% from the baseline,

and a total of 475 MWh year −1. Table 3 shows com-parative life cycle costs of the existing relatively cheappump model used for the small aquarium tankssubstituted with a very high quality and efficiency mod-el (overall 3.5% reduction in electricity consumption).Further, a total of six 37-kW pumps were modified orreplaced, and associated piping systems designed tooptimise efficiency. In one example, a 37-kW pumpmotor (on a variable speed drive, but running veryinefficiently) was replaced with a 4-kW motor for thesame flow resulting in overall power savings of 3.5%from the baseline at a cost of $1500 ($9840 saved on theelectricity bill in the first year, payback time of2 months). Prior to 2010, 15 metal submersible pumps(240 V) used for water circulation in the 3.2-ML CoralReef Exhibit were inefficient and had maintenance is-sues and safety concerns. A replacement low-voltage,carbon-fibre plastic composite pump model saved34 MWh year −1 (1.5% of baseline power) and$10,000 per year in spare parts, labour and anodes toavoid pump corrosion. The overall energy savings for‘special machinery’ were minimal and highly seasonal.

Integrated rooftop solar PV system

The solar feasibility study projected a 4.6 kWh per dayper kilowatt peak, slightly lower than the 4.34 kWh perday per kilowatt peak measured for 2015. This is prob-ably due to a larger solar PV system than originallyplanned being installed (206 kW and not 145 kW),resulting in the suboptimal location of some panels(resulting in occasional shading) and the effect of thegrid protection device. The overall system performanceexceeded expectations and performed equal to commis-sioning 3 years later and no maintenance costs in thefirst 4 years. The predicted system cost was $5.50 per

Table 3 Comparative life cyclecost of small aquarium pumps.Figures have been validated withthe actual costs for 7 years

Replacement of 46 small aquarium pumps with 33 higherquality pumps

‘Cheap’model

Energy-efficientmodel

Capital expenditure over 10-year life $42,262 $87,960

Total labour cost for breakdown maintenance for 10-year life $162,602 $17,293

Total life cost of replacement parts/pumps for 10-year life $33,070 $4480

Total life energy cost over 10-year life $309,316 $210,352

Total life cycle cost over 10 years $547,250 $320,085

Total MWh savings over life cycle for the energy efficientpump model

607 MWh

Payback time 2.2 years

160 Energy Efficiency (2018) 11:147–168

kilowatt peak installed. The installation of additionalhigh-durability canopies to hold extra solar panels,changes electricity tariffs (see the ‘Electricity cost andtariffs’ section), and new government imposed no exportand grid protection requirement resulted in an actualcost of $5.83 per kilowatt peak installed. This combinedwith changes in the electricity tariff structure resulted inan increased modelled predicted payback time from 6 to14 years. However, the large-scale renewable energycertificates (LGCs) have doubled in price from $35 permegawatt hour in 2010 to $75 per megawatt hour in2015, which increases revenue and payback will de-crease if all power generation wastage is eliminated.Regardless, the predicted financial savings for a 25-year life of the solar PV system are still highly signifi-cant at $1.8M over the life of the system (Fig. 6).

Electricity cost and tariffs

The combined energy savings measured graduallylowered the peak power demand from the electricitygrid by 46% between years 0 and 8, and the Aquar-ium moved to a lower cost electricity tariff in year 7.A huge increase of the grid connection fee, from0.005% of the energy bill in year 0 to 26.5% in year9, offsets this benefit, increasing the expected pay-back period for the solar power system and (to alesser extent) the HVAC system. The Aquarium paidmore in electricity for half the power use in year 8than in year 0 and the power cost would be doubledwhat it is today without the retrofit actions, wellbeyond affordability within current funding arrange-ments (Fig. 2).

Life cycle savings and C02-e avoided

Figure 6 shows the cost of the main energy consumingelements against the carbon dioxide equivalent (CO2-e)abatement for the life of the equipment. All groups except‘special machinery’ are predicted to have significant finan-cial benefits and CO2-e abatement over the life of theequipment, and the total CO2-e abatement for all measuresis 1390 tonnes of CO2-e (excluding ‘operational’ groupwhose data is also included in the HVAC-related group) ifthe ‘scope 2’ emission factors are is used. If ‘scope 2’ and‘scope 3’ emission factors are used, then the CO2-e abate-ment increases to 1614 tonnes of CO2-e (see the ‘Energyuse and costs data analysis’ section). The baseline wasadjusted by 286 MWh to reflect additional pumping

requirement for new or enhanced aquarium life support(see the ‘Total energy consumption’ section).

Non-financial and other benefits

The Aquarium exceeded the 230-kW peak demand sav-ing target that was part of the Ergon Demand Manage-ment Pilot Project (with 259 kW saved). In return, theAquarium received a one off payment of $67,160($259.30/kW) by Ergon Energy in 2013 and was grantedsustainability awards, positioning the Aquarium as anexample for environmentally sustainable business prac-tices (Queensland Tourism Awards 2012) (EcotourismAustralia 2012). The energy minimisation project helpedto communicate conservation messages through educa-tion programmes and validated benefits and businesscases for further initiatives.

Discussion

Relevance of energy use savings resultsfor the buildings sector

The Aquarium reduced its energy intensity from1625MJm−2 in year 0 to 773MJm−2 in year 8 (973MJm−2 excluding solar generation). Using the 2011–2012 fi-nancial years, this compares with 2298 MJ m−2 for theAustralian Institute of Marine Science (AIMS) in Towns-ville (Australian Government, Department of ClimateChange and Energy Efficiency 2012); 3800 MJ m −2 forthe average regional Queensland supermarket; and1684 MJ m−2 for an average Australian hospital (Pitt andSherry 2012). The National Australian Built EnvironmentRating System (NABERS) provides energy ratings andtools for commercial buildings to predict energy savings,but only for four types of commercial buildings: offices,shopping centres, data centres and hotels (New SouthWales Office of Environment and Heritage 2016). A sim-ilar tool would have helped the Aquarium identify areas ofpoor performance, benchmark baselines and monitorprogress.

Whole of life costs, impact of audits and accessto knowledge in decision making

Major renovations rarely occur over the life of commer-cial buildings, and they are usually triggered by theequipment end of life or change to fitness of purpose.

Energy Efficiency (2018) 11:147–168 161

This represents 10% of all building construction (Pittand Sherry 2014) but the buildings retrofit rate is only2.2% per year (Ma et al. 2012). At the Aquarium, theend of life of infrastructure triggered the improvementof the building’s energy performance, but only due to in-house awareness of energy efficiency potential andwhole of life costs gained through audits and network-ing. Prior to year 1, in-house knowledge on the connec-tion between energy use and building design,

maintenance and operation was lacking to drive therequired strategic decisions. Pitt and Sherry (2014) doc-ument that stakeholders show little awareness of orinterest in energy efficiency when considering retrofits.They also report large gaps in the quality, scope andaccessibility of information on how sustainability relatesto the built environment, leading to a low willingness topay for energy-efficient options (Pitt and Sherry 2012),despite evidence that very low-energy retrofits of

Lighting

OperationalHVAC Related

Machinery Solar

Special Machinery

204 408 611 815 1,019 1,223 1,427 1,630 1,834 2,038

-600

-500

-400

-300

-200

-100

0

100

200

300

$ p

er M

Wh

pe

r y

ea

r

Cumulative MWh per year

The wider the block, the

greater the electricity (MWh)

1 MWh electricity = 0.81 CO2-e

Cost

Saving

Capital

Cost ($)

Payback

(years)

Life cycle

savings ($)

MWh per year

avoided

CO2-e per year

abated

Lighting 52,800 2.5 129,414 33 27

Machinery 106,300 3 1,720,008 471 382

Solar 1,127,000 14 1,781,088 299 242

Operational 6,500 0.3 2,339,757 319 258

HVAC related † 359,000 2 5,961,638 910 737

Special Machinery 25,400 n/a -141 (cost) 4 3

Total Capital Cost: $1,671,000 (this excludes items 21-23 in Table 1 whose energy savings could not be quantified,

and minus Operational Capital Cost which is included also in the HVAC related category); 5% discount rate

Fig. 6 Marginal abatement cost analysis comparing energy usereduction measures with cost or saving per unit (MWh) of gridelectricity use over the life of the category (y-axis). Accumulativegrid electricity use avoided (or tonnes of carbon dioxide equivalentabated) is shown on the x-axis. Special machinery is SCUBAcompressor and reverse osmosis machine; dagger indicates re-placement of HVAC with a like-for-like air-cooled system wouldhave required increased efficiency by 14% to meet Australian

standards for performance; HVAC figures compare savings overexisting equipment in year 6; total replacement cost of HVACwould have a payback time of 6 years; baseline was adjusted(286 MWh added) to reflect additional machinery and load onthe HVAC systems since year 1 (see the ‘Total energy consump-tion’ section for details). Data was generated and adapted fromMACC BuilderPro™ software

162 Energy Efficiency (2018) 11:147–168

buildings can be economically attractive, sometimeseven at net negative costs (Levine et al. 2007).

For the Aquarium, audits (despite their varying qual-ities against cost) were a fundamental stepping stone toachieve the desired outcomes. In this case study, themost expensive audits did not result in the most helpfuloutcomes, which emphasises the need for consumers tohave access to detailed technical knowledge or assis-tance from accreditation schemes to assess energy-efficient retrofit possibilities and audit providers(Department of Industry, Innovation and Science2015). Redmond and Walker (2016) also found thateconomic returns can vary significantly for energy au-dits in Australia. The Aquarium case study may helpother stakeholders invest with confidence in energy-efficient infrastructure and consumers may maximisethe benefits by specifying a detailed scope and desiredoutcomes, requiring supplier to specify standard auditmethods and obtaining references from suppliers fortheir previous projects.

Maintenance of equipment, shift from designspecifications and building heat loads

In this study, HVAC-related retrofit actions resulted inthe greatest energy use savings, including actions toaddress poor maintenance. For buildings withcentralised HVAC, there is no requirement to ensurethat buildings are properly commissioned and main-tained to guarantee design efficiency (Pitt and Sherry2014), leading to significant yet avoidable energy inef-ficiencies. The Aquarium ensured that energy efficien-cies were maximised by refining the BMS settings andoperational processes, in collaboration with thedesigner, the installer and an independent qualitycontroller. Pitt and Sherry (2014) report that the differ-ence between good and poor commissioning of HVACmay represent up to double the rate of energyconsumption.

The direct impact of glazing retrofits was not quan-tified in this study; however, other studies quote signif-icant savings, with double insulated low-e glazing re-ducing HVAC electricity by 180–288 MJ m−2year−1 (Liet al. 2015), or ‘cool paints’ on external walls and roofsreducing indoor cooling by 60% (Marino et al. 2015).Prior to year 1, air leaks caused significant wastage ofenergy, mainly through doors left open in summer forpublic movement. Once identified and addressed, sub-sequent savings were achieved but are still strongly

influenced by staff behaviour and operational processeswhich is consistent with other studies (Azar andMenassa 2015).

Thermal comfort, HVAC and BMS

In this study, a 1.5 °C rise in indoor temperature signif-icantly reduced power consumption (by 13% in year 1)with no significant change in survey respondent’s as-sessment of comfort and no significant change inworker’s assessment of their own productivity. This iscomparable to studies of Sydney, Melbourne and Bris-bane offices where an average of 6% power use wassaved for every 1 °C increase in indoor temperature insummer (Roussac et al. 2011). Another study found anaverage thermal comfort level of 26.4 °C for two Indiancities, which is warmer than the current Indian standardupper limit of 26 °C (Indraganti et al. 2014).

Prior to 2007, the Aquarium was maintained at arelatively low temperature (23 °C) which did not takeinto account visitors’ adaptation to the tropical condi-tions outside (which may be more than 10 °C higher)and modern thermal comfort expectations for the indoorenvironment. Nicol (2004) argues that thermal comfortis affected by outdoor temperature, and takes into ac-count the adaptive thermal comfort model, and otherauthors report that expectations appear to be based onrecent experiences (Luo et al. 2016). Therefore, it isimportant to periodically review indoor temperatureset-points against current standards and models. Theefficacy of an Ergon Energy initiative encouraging theuse of higher indoor set-point (25 °C) or similar com-munity campaigns in North Queensland remainsunquantified. ‘Energy cost saving’ is considered animportant driver to tolerate high indoor temperatures ifthose enduring the higher temperatures can see costbenefits flow on to them, and can be a more importantfactor than occupant thermal comfort and productivitywhen deciding on indoor temperature set-points(Lakeridou et al. 2014; Boldero 2013). It would beuseful to undertake further tests at the Aquarium todetermine whether the indoor temperature set-pointscould be further increased (and determine comfortthresholds) up to the current applicable Australian stan-dards (26 °C). Since HVAC is responsible for around50–70% of energy use in buildings, this measure repre-sents a high potential for energy use reductions withminimal cost. Further case studies are needed to deter-mine if expectation management can help to foster

Energy Efficiency (2018) 11:147–168 163

thermal comfort adaptability in the tropics, and maxi-mise the potential energy saving for HVAC use.

Innovative and site-specific BMS control of HVACwith integrated TES and solar PV power can producesignificant efficiencies with minimal cost, to the extentthat it delayed the need for electrical battery powerstorage at the Aquarium. The Aquarium uses the ReefTank to store chilled water. Although chilled waterenergy is not discharged to a different system, like atraditional TES system, the cooling requirement isbrought forward by chilling the tank lower than theoptimal set-point. Thus, the cooling capacity is effec-tively stored in the system which maintains the temper-ature below or at the optimal set-point for longer therebynegating the need for the capacity later. Not only doesthis help to minimise PV generation wastage, it alsohelps to minimise peak demand. The methods in thisstudy could be similarly applied to hotels with heatedswimming pools, public swimming pools and otheraquariums. A larger TES system used specifically tostore energy from surplus solar PV may provide a lowercost option against electrical battery storage. Historical-ly, TES systems have been used only to manage peakdemand to minimise the cost of power, where there aretime of use and demand tariffs.

Most significant actions and indirect benefits

The benefits of one conservation measure against theothers are not always quantifiable due to (a) simulta-neous changes and absence of separate power use log-ging on all components and (b) the significant andcomplex non-financial factors involved. A HVAC retro-fit is a highly effective action to realise large reductionsin energy consumption consistent with the findings ofothers (Carbon Trust Australia 2010). Optimization ofenergy use using a BMS is a low-cost and flexible toolto minimise wastage of power use and power genera-tion, and operational changes stand out as a highlyefficient measure to reduce energy use, with an imme-diate outcome and no financial cost, and should beconsidered seriously alongside hi-tech measures.

As they are difficult to quantify or predict for thepurpose of a business case, many retrofit actions hadindirect benefits that were either underestimated or notcontemplated at the outset. For instance, the energy-efficient items tended to be of higher quality and dura-bility than non-energy efficient equipment (lower main-tenance requirement), reduced transport costs, waste

disposal and administration for replacement equipment.The new ability to always maintain an optimum tem-perature in the Aquarium’s Coral Reef Exhibit (theworld’s largest living coral reef aquarium and principalasset of the Aquarium) was a highly significant benefit.Prior to year 6, the temperature would frequently dropbelow a critical threshold in the hot summer months. Asa consequence, corals would sporadically experiencethe potentially lethal ‘coral bleaching’ due to heat stress.The massive reduction in power consumption alsoallowed the entire site to be linked to the emergencystandby diesel generators, where previously only limiteditems could be connected.

Renewable energy

Despite non-advantageous site-specific factors andchanges to the electricity tariff structure since year 0,the whole of life financial benefits for the Aquarium’ssolar PV system is predicted to be significant. Othersites may not have these costs, and hence payback timesmay be much lower also considering the falling cost ofsolar systems and emerging storage technologies. De-spite these proven advantages and excellent geograph-ical conditions for solar power technology, the numberof large commercial rooftop systems in Queenslandremains small (Garnaut 2011) which provides signifi-cant potential for new solar energy installations. It isimportant to consider the entire life cycle and environ-mental costs of PV power compared to electricity pro-duced from coal. The environmental cost of PV systemsover their entire lifecycle is an order of magnitudelower than a coal power station in terms of greenhousegas emissions (Peng et al. 2013; Epstein et al. 2011) andother reduced environmental and human impacts asso-ciated with non-renewable energy sources (Spath et al.1999). The successful application of the BMS com-bined with the solar PV has highlighted the opportunityto expand the PV system at the Aquarium if a largerTES is added, delaying the need for electrical batterystorage.

Investment patterns and business growth

Substantial reductions in global carbon dioxide emis-sions will require large changes in investment patterns(Levine et al. 2007). The energy reductions achieved bythe Aquariumwere only possible through amajor shift ininvestment patterns and procurement strategies. With

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limited evidence to support business models and predic-tions, considerable negotiations within the procurementprocess were required due to perceived risk. Thus, a lackof energy efficiency regulations, knowledge, time andconfidence to pursue the energy efficient options mayeasily result in lost opportunities for savings. Even with-in the Australian government, operations which use 22million GJ year −1 of energy (Australian Government,Department of Climate Change and Energy Efficiency2012) and occupies 32% of Australian commercialbuildings stock (Energy Efficiency Council 2011) furtherintegrating environmental sustainability in the procure-ment process could generate significant savings (TheAuditor-General 2015). An average energy efficiencyimprovement in buildings of less than 3% would freeup $10 million a week to be invested in other parts of theAustralian economy, and reduce the negative and socialcosts of greenhouse gas emissions in the process (Pittand Sherry 2014). The results achieved at the Aquariumshow the potential benefits if similar energy saving ini-tiatives were undertaken on a national scale, if facilitatedby a clear mandate, clear process and timely access tofunding (Energy Efficiency Council 2011).

The Aquarium was able to grow its business despitethe disruptions that the refurbishments created, and vis-itor numbers to the Aquarium were at their highest in15 years in 2012 (year 7) and continue to rise. Part of themove towards a more sustainable business model hasbeen to place education at the centre of all energyconservation actions, which appears to foster tolerancefor the difficult aspects of the changes and maximise thebenefits of the changes.

Future actions

Energy consumption increased significantly in the cate-gory ‘other’ from year 0 to year 8 (Fig. 3). This categorywill be targeted to reduce and manage energy use.Additional energy use reduction measures include (a)additional solar PV combined with additional TES andother energy storage solutions; (b) further increases intemperature set-points with a targeted communicationcampaign; (c) further measures to reduce heat load onthe building such as the use of hi-tech material to shadethe large outside aquariums; (d) computerised control ofthe compressor driven ‘wave machine’ to maximiseefficiency; (e) investigation of non-solar renewable en-ergies such as tidal and wind; (f) energy recovery sys-tems; (g) further modifications to filtration system to

maximise efficiency; and (i) further utilisation of theBMS to maximise efficient use of power.

Conclusions

This case study shows that it is possible to adopt verylow-cost energy saving measures (such as indoor tem-perature adjustments and better maintenance of HVAC)in a commercial building with no significant negativeeffects on comfort or employee productivity. If similarmeasures were adopted nationwide, millions of dollarsmay be liberated for the Australian economy. This casestudy also shows that capital investment in energy-efficient critical infrastructure such as HVAC (particu-larly where equipment and infrastructure nears the endof its life) can have short payback times and high directand indirect benefits relative to costs. Here, the mosteffective measures were as follows: manipulation ofindoor temperature and energy wasting behaviours, in-vestment in high-quality and low-energy equipment(pumps and lights), upgrade and fine-tuning of theBMS-controlled HVAC system with integrated TES,modification of the building envelope (double glazing,reflective roof coating and minimisation of buildingleaks) and generation of renewable energy. This studyis important as it demonstrates that a BMS can be usedto control HVAC with integrated TES to optimise andstore solar PVand also avoid PVenergywastage therebyavoiding or delaying the need for electrical battery stor-age. These measures are relevant to many medium tolarge commercial buildings.

The experience of Reef HQ Aquarium described inthis study illustrates the positive impacts of reducinggreenhouse gas emissions and simple ways to achievea more environmentally responsible business model,through an energy-efficient building retrofit. An in-creased knowledge of the effect of building design,maintenance, equipment efficiency, whole of life cyclesand equipment quality on annual energy costs may alsoincrease a willingness to pay for high-quality energy-efficient products.

Acknowledgments The data collection in this case study wasfunded by the GBRMPA with two exceptions: Ergon Energyfunded two energy audits and an M&V report for the DemandManagement Pilot programme. The authors would like to thankFred Nucifora, Reef HQ Aquarium Director, for his inspiringleadership, GBRMPA senior management for their support in

Energy Efficiency (2018) 11:147–168 165

decision making and Reef HQ Aquarium staff for their commit-ment to energy minimisation programs. Thanks also go to AdamSmith, Mike Tarrant, Tyrone Ridgway and Ashley Frisch for theirvaluable comments on the paper. Thanks to Marcus Thyer fromCave Image Manipulation for assistance with figures. Thanks tothe following individuals and organisations who took a keeninterest in helping Reef HQ Aquarium to achieve the best possibleresults: Townsville City Council, Peak ARE Pty Ltd., NQ ControlServices, Tropical Energy Solutions Pty Ltd., Stowe Australia PtyLtd. and Warren Applegate, Ian McGregor and Neil Horsley(Ergon Energy).

Author contributions S.Thy. (Reef HQ Aquarium TechnicalOperations Manager and capital projects manager) designed thestudy and implemented the projects, and collected and analysedthe data. C.M. designed the TES, HVAC and BMS and wasengaged by Ergon Energy to carry out the M&V study for theErgon Energy DemandManagement Pilot Programme. S.Thy. andS. Tho. drafted the manuscript. M.R. carried out the statisticalanalysis and contributed to the design for the thermal comfortstudy. All authors edited the manuscript and gave final approvalfor publication.

Compliance with ethical standards

Conflict of interest The authors declare that they have no con-flict of interest.

Open Access This article is distributed under the terms of theCreative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestrict-ed use, distribution, and reproduction in any medium, providedyou give appropriate credit to the original author(s) and the source,provide a link to the Creative Commons license, and indicate ifchanges were made.

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