HVAC Energy Efficiency in Commercial Buildings

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sustainabilityPrepared by Alan RichardsonAugust 22, 2011

1Prepared by Alan Richardson

Stakeholders

HVACImproving energy efficiency in existing non-residential buildings

So where are you at?

August 22, 2011Prepared by Alan Richardson

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Conscious Competent

Unconscious Not Yet Competent

Unconscious Competent

Conscious Not Yet Competent

as an individual?as an organisation?

as an individual?as an organisation?

Quiz

Facts and figures as supplied by Sydney Water and Energy Australia

August 22, 2011

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Prepared by Alan Richardson

One tonne of CO2e emitted by a coal fired power plant is equivalent to how many kWh of electricity?

How many tonnes of CO2e per year does an average sized family car emit?

What is the recommended flow rate of water for a household shower?

How may Litres (L) does an Olympic swimming pool hold when full?

What is the measure of instantaneous electrical load?

When we want to express the amount of electrical energy used over a period of time we express it as kilowatt hours (kWh). How many 20 Watt light bulbs burning for one hour will consume 1,000 kWh of electricity?

Australia’s energy use

August 22, 2011

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Source: Total Environment Centre

Commercial building energy use

HVAC systems account for 30% of energy consumption in Australian commercial buildings

Commercial sector about 300PJ or 8% of final energy use in Australia (ABARES 2011), and 200PJ of electricity use (Langham et al 2010)

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There is always a stick!

Commercial Building Disclosure (CBD) is a national program designed to improve the energy efficiency of Australia’s large office buildings

http://www.cbd.gov.au/default.aspx

Section J of the Building Code of Australia Deals with energy efficiency requirements of

BCA class 3 to 9 buildings National Greenhouse and Energy Reporting

(NGER) Act 200 Building Energy Efficiency Disclosure Act 2010

October 2011 all prospective tenants or buyers must be provided with a Building Energy Efficiency Certificate (BEEC), valid for one year, and summarises the performance of the building, including the efficiency of lighting in the building

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Consumption vs peak demand

What is peak demand?

used in energy demand management describing a period in which electrical power is expected to be provided for a sustained period at a significantly higher than average supply level

‘large electricity customers pay about 13% of their bills to cover peak capacity charges each year, and a further 32% to cover network energy charges. That’s around $150,000 per year in peak demand charges and $350,000 in network energy charges for the largest of CBD buildings. So any peak demand reduction also means lower energy expenditure’Peak demand tackled by Greener Buildings. Green Buildings Alive

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Do you remember the heatwave week 31 January - 4 Feburary 2011?

The analysis shows that if a typical building were to be upgraded from the Sydney average of 2.5 stars to 5 stars, a 57% reduction in electricity consumption would be achieved with a corresponding reduction in peak demand of 26%. This study implies that for every 10% reduction in buildings’ yearly electricity consumption they make a 4.5% reduction in their peak demand.

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Peak demand 12pm – 4pm

Source: www.greenbuildingsalive.com/blog

Breakdown of an electricity bill

Calculating the real cost of energy

Peak charges: 8.72 c/kWh

Off-peak charges: 4.02 c/kWh

Average charge: 7.31 c/kWh

August 22, 2011

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Typical cost

Energy Peak 6 c/kWh

Off peak 3 c/kWh

Network Network peak 2.5 c/kWh

Network off peak 0.8 c/kWh

Network standing charge -

Demand $6/ kW-month

Other E&REC - MRET 0.1 c/kWh

NEMCO ancillary 0.07 c/kWh

NEMCO pool fees 0.05 c/kWh

Meter provision $900 pa

Retail service fee -

Energy costs forecasted

The graph details the cost and escalation rates for retail electricity prices forecasted for the next 15 years

August 22, 2011

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Source: The Road To Green Property by Davis Langdon

Australia’s marginal abatement cost curve

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Low cost

High cost

Source: ClimateWorks

Australian building’s marginal abatement cost curve

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Low cost options

High cost options


What is HVAC?

Heating, ventilation and air conditioning (HVAC)

HVAC systems in commercial buildings add or remove heat and moisture (humidity) to maintain environmental conditions

Also filter and recirculate air to remove odour, dust and other particulates to provide acceptable standards in air quality

A Building Management System (BMS) controls operation of HVAC system components: fans, pumps, chiller heater (boiler) and cooling tower

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Central HVAC

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Air Handling Unit (AHU)AHU

Chiller

HWS

Building Management

System

Cooling tower

Diffuser

Outside air

intake

Pumps with VSDs Heating coilCooling coil

Variable Speed Drive VSD

VSD

AHU

Air Handling Unit (AHU)

Variable Air Valve (VAV)

Central HVAC

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Air Handling Unit (AHU)AHU

Chiller

HWS

Building Management

System

Cooling tower

Diffuser

How the cooling cycle in a central HVAC system

Pumps with VSDs Heating coilCooling coil

Variable Speed Drive VSD

VSD

AHU

AHU

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August 22, 2011

Self contained packaged HVAC

Why energy efficiency in HVAC?

Cooling and heating are major contributors to peak demand for energy, they contribute disproportionately to energy bills, which increasingly include extra charges for high energy demand not only consumption

Cooling requirement is a higher % than heating as a building’s heat requirement is offset by waste heat?

Waste heat: people, computers etc

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What is your approach to energy efficiency?

Avoid Reduce Reuse Renewable

August 22, 2010

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Does this sound similar to how organisations manage OHS

risk?

Does this sound similar to how organisations manage OHS

risk?

Energy efficiency opportunities in HVAC

Recommissioning HVAC system Mixed mode ventilation Upgrades to HVAC control system Reducing electrical loads Enthalpy optimisation Change practices to reduce peak demand Upgrades to fans and pumps Upgrades to cooling and heating plant Maintenance

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Barriers to implementation

High capital cost Implementation can be complex if a

whole HVAC system upgrade is necessary

Upgrading key components i.e. chiller plant in a building will require the partially shut down of that activity for a period of time

Existing leases Re-negotiating leases

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Drivers for energy efficiency decisions in large tenanted commercial buildings

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Decision making

‘By understanding the human psychology of choice and decision-making, the industry can identify the greatest barriers inhibiting change, discover opportunities for improvement; adopt new methods of communication and design programs that are in line with consumer demands’ Source: 2011 IBM Global Utility Consumer Survey

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What to do and when? 34

Source:

Financing options available to fund energy efficiency opportunities

Low Carbon Australia

http://www.lowcarbonaustralia.com.au/page/financial-products-and-services

Low Carbon Australia’s Energy Efficiency Program provides finance and advice to businesses looking to invest in the energy efficiency retrofits of existing non-residential buildings:

Clean Energy Loans – to finance improvements which deliver energy and carbon savings for the benefits of building owners and tenants

Energy Efficiency Leases – to help overcome constraints to businesses of providing up front capital for energy efficiency equipment, offers owners and tenants the flexibility to upgrade as technology evolves and improves and removes from the lessee residual value risk of the asset

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Energy Savings Guarantee On-bill financing – enables businesses to install and upgrade energy efficiency equipment, financed by a utility, with repayments made by the business through their monthly utility bill. This removes the requirement for upfront capital for energy efficiency equipment, with repayments typically equal to or less than the energy cost savings achieved

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Environmental Upgrade Agreements (EUAs) – an agreement between a building owner, a finance provider and a council which allows building owners to access finance for environmental upgrades to their building. Repayments are structured through a council levy on the property, with the council then forwarding on payments to the finance provider. EUA’s overcome difficulties for building owners in providing upfront capital and allow for structured payments that remain with the property if ownership changes. Building owners may also pass on repayment costs to tenants who can benefit from reduced energy costs and a more environmentally efficient workplace

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Funding energy efficiency opportunities

Tax Breaks for Green Buildings

http://www.thefifthestate.com.au/archives/21194

Green Building Fund

http://www.ausindustry.gov.au/InnovationandRandD/GreenBuildingFund/Pages/GreenBuildingFund.aspx

Tax Breaks for Green Buildings From 1 July 2012, businesses that invest

in eligible assets or capital works to improve the energy efficiency of their existing buildings (from 2 stars or lower to at least 4 stars) may be able to apply for a one-off bonus tax deduction. The incentive will enable businesses to claim a bonus tax deduction of 50% of the cost of the eligible assets or capital works. This initiative is expected to provide a boost of around $1 billion over the life of the scheme to help ‘green up’ existing buildings across the country

Green Building Fund Round 7 of the Green Building Fund closed on 29 March

2011

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Energy efficiency opportunities in HVAC

Recommissioning HVAC system Mixed mode ventilation Upgrades to HVAC control system Reducing electrical loads Enthalpy optimisation Change practices to reduce peak demand Upgrades to fans and pumps Upgrades to cooling and heating plant Maintenance

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Upgrade HVAC control system using Direct Digital Control (DDC)

Controlling a HVAC system involves three distinct steps:

1) Measure a variable and collect data

2) Process the data with other information

3) Cause a control action

The above three functions are met through sensor, controller and the controlled device

Direct Digital Control (DDC) is the automated control of a condition or process by a digital device

The benefit of DDC over past control technologies (pneumatic or distributed electronic) is that it improves the control effectiveness and increases the control efficiency

‘The DDC system is the "brain" of the HVAC system. It dictates the position of every damper and valve in a system. It determines which fans, pumps and chiller run and at what speed or capacity. With this configurable intelligency in this "brain", we are moving to the concept of building automation’ Wikipedia

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Upgrade HVAC control system using Direct Digital Control (DDC)

Controlling a HVAC system involves three distinct steps:

1) Measure a variable and collect data

2) Process the data with other information

3) Cause a control action

The above three functions are met through sensor, controller and the controlled device

Upgrading HVAC control system to DDC has potential to improve energy efficiency by up to 20%

Most subsystems, from Variable Air Valve (VAV) boxes to boilers and chillers, now have an onboard DDC system to optimise the performance of that unit. A communication protocol known as BACNet is a standard protocol that allows control units from different manufacturers to pass data to each other

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Upgrade Building Management System (BMS) to Energy Management System (EMS)

Upgrades to Building Management System (BMS) for increased control and optimisation HVAC system operation

Energy Management System (EMS) is a computer based energy monitoring and optimal control system for building services

Conventional BMS can be upgraded to EMS providing greater and optimal control for: HVAC, chillers, pumps, cooling towers,

boilers and energy demand EMS has potential to improve energy

efficiency between 20-50% for HVAC and chillers

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Mixed mode ventilation

Mixed mode ventilation

Combination of a combination of natural ventilation from operable windows and mechanical HVAC

Key to mixed mode ventilation is that an educated tenant can have big impact on energy use

Study shows individuals are more tolerant of temperatures when they feel they have control

Suggested strategy: 19-26°C temperature band with natural

ventilation A/C off when ambient temperature within band

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Reducing electrical loads


Adjust set points Set thermostats at 25°C for cooling in the

summer and 18°C for heating in the winter Implement a deadband control strategy

Optimal start time of HVAC Normally pre-cooling/heating time is pre-set Can change to be a function of ambient

temperature Hot day: longer pre-cooling time Mild day: shorter pre-cooling time

Turn outside air off during pre-cool/pre-heat

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Players comfort?


‘The static (1oC) setpoint increase produced a 6% reduction in daily HVAC electricity consumption. The dynamic approach produced savings of 1.4%, however it was not operational until autumn 2010. This limited our ability to directly compare the two approaches. It was found that occupant comfort, quantified by frequency of ‘complaints’ registered with a tenant helpdesk, was adversely affected under both strategies.’A preliminary evaluation of two strategies for raising indoor air temperature setpoints in office buildings. By Craig Roussac Jesse Steinfeld and Richard de Dear

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What is a deadband control strategy?


A deadband is a range where no action occurs (the system is dead)

The larger the deadband the less the major energy consuming elements of the HVAC need to work (chillers, hot water service)

The big advantage of a wide range is that it stops the conflicting systems ‘hunting’ ie. heating up, then cooling, then heating, then cooling, etc

a widening of temperature dead bands has been more effective than pretty much every other HVAC strategy (apart from turning it off)

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What are the energy savings from a deadband control strategy?


A standard approximate for energy savings would be something like the figures below:

Bottom of range – actual set point – top of range

•22o - 22.5o – 23o (0.5 degree) normal 0% energy saving

•21o - 22.5o – 24o (1.5 degree either side) 10% energy saving

•20o - 22.5o – 25o (2.5 degree either side) 20% energy saving

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What is the best deadband range?


Generally accepted practice is to have a deadband of between 21 - 24oC where in summer system will keep temp at 24oC but not try to push down below 22.5oC and in winter keep temperature at 21oC and not try to push past 22.5oC

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Economy cycle and free cooling

Enthalpy optimisation

There are energy savings if the cooling coil is presented with the air having the lower enthalpy whether this is return air or outside air

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Source: www.energystar.gov

Return air, damper closed, becomes

exhaust air

Air Handling Unit(AHU)

100% outside air

No heating or cooling of outside air


The economy cycle operation uses fresh air for building cooling, instead of the chiller when outside conditions permit. In addition to providing free cooling, when outside conditions are suitable, economy cycle operation increases the amount of fresh air in the conditioned space

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Source: www.energystar.gov

Return air, damper closed, becomes

exhaust air

Air Handling Unit(AHU)

100% outside air

No heating or cooling of outside air



There are energy savings if the cooling coil is presented with the air having the lower enthalpy whether this is return air or outside air

More info:

Retro-fitting an economy cycle depends on: Capacity of Air Handling Units (AHUs) Fresh air supply duct size Type of HVAC control system – at

minimum use DDC and enthalpy based control

There are two types of economy cycles: temperature OR enthalpy based

Enthalpy based economy cycle provides better control = greater energy savings

Cost $POA

August 22, 2011

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More info:http://www.seav.vic.gov.au/manufacturing/sustainable_manufacturing/resource.asp?action=show_resource&resourcetype=2&resourceid=32

Enthalpy is determined by a combination of temperature and relative humidity

If economy cycle fitted then check the operation as follows: Is the controller functional? Is the controller calibrated?

There are two types of economy cycles: Temperature based Enthalpy based

Enthalpy based economy cycle provides greater control = greater energy savings

August 22, 2011

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Economiser


There are energy savings if the cooling coil is presented with the air having the lower enthalpy, whether this is return air or outside air

In simple terms, an economiser is a heat exchanger

An air-to-air heat exchanger, inside AHU, uses cooler or warmer return air (summer/winter), to pre-cool or pre-heat the incoming outside air

There is no cross contamination of air paths Economisers perform best in cold temperate

climates but not hot and humid climates Can be retrofitted to ducted a/c systems Packaged systems must be purchased with

economiser option

August 22, 2011

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Economiser

When temperatures are hot or cold outside with high occupancy inside, 100% outside air passes through the heat exchanger which reduces the fresh air energy load through pre-conditioning the outdoor air

Used to cool the fresh air by exhaust air with an air-to-air heat exchanger

August 22, 2011

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Source: http://www.airchange.com.au/

Demand control ventilation

CO2 sensors monitor the space and provide minimum Outside Air in times of low occupancy to conserve energy

August 22, 2011

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Source: http://www.airchange.com.au/

Night purge

Reduce electrical loads

During the cooling season, if the inside temperature is considerably greater than the outside air temperature, then the air handling units may be turned ON during the night, to purge the warm air out of the building. This is called a Night Purge Cycle. This type of free cooling reduces the amount of mechanical cooling that has to take place the following morning.

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Night purge

Reduce electrical loads

However, caution should be taken concerning the humidity of the outside air. To address this concern, an enthalpy optimisation program

Whether or not to use the night purge cycle is determined by comparing the cost of running the air handling units at night versus the cost of running the mechanical cooling in the morning

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Other change practices to reduce peak demand

Other change practices to reduce peak demand

Demand limiting switch off equipment as the electrical use approaches

the peak load time. BMS programmed with a priority list of non-critical items to be turned off, simply follows the list until the energy use curve is levelled off and the peak load passes

Load levelling Operating times of other energy using activities shifted

outside peak demand period of HVAC operation

Peak load shifting E.g.run the chillers during the night to chill water that is

stored in large tanks on the premises. During the peak building load the following day the chillers are turned off and the ready-made chilled water is circulated to the building loop

August 22, 2011

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Variable speed drives (VSDs)

Upgrades to fans and pumps

More info:

http://www.seav.vic.gov.au/manufacturing/sustainable_manufacturing/resource.asp?action=show_resource&resourcetype=2&resourceid=31

http://www05.abb.com/global/scot/scot201.nsf/veritydisplay/cd6d14453239c791c125750800332bd2/$file/Energy_efficiency_makes_difference_191108.pdf

August 22, 2011

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Prepared Alan Richardson

Variable speed drives (VSDs)


More info:



HVAC components such as fans and pumps have traditionally used constant speed drives (motors)

Variable speed drives allow fans and pumps to modify the speed they operate to match the load that is put on them

Require less maintenance Variable speed drives are one of the biggest

and most economically viable energy saving opportunities in HVAC systems for supply and return air fans, chilled and condenser water pumps and chiller compressors

August 22, 2011

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What are the energy savings from VSDs?


More info:



VSDs on fans and pumps Supply and return air fans Chilled and condenser water pumps Chiller compressors

Variable-speed motor drives: $3,000 to $5,000 each (installed)

Savings vary – EPA study on VSDs showed average annual energy savings of 52% of pump/fan energy and 2.5 year simple payback

August 22, 2011

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Maintenance

Maintenance Check for and repair leaks in ductwork Check insulation of heating and cooling pipework

and ductwork Check for faulty/frozen dampers

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August 22, 2011Prepared Alan Richardson

Chiller upgrade

Efficient chillers

http://www.powerpax.com.au/casestudies

Refurbishment relevance: Especially for ~1980s buildings due for upgrade

Life service of chiller: 20-25 years Operating costs over lifetime greatly

exceed initial cost Can double or more the efficiency from old

chiller to new high-efficiency chiller, plus improved part load performance

Require existing chiller load profile to estimate potential savings from new chiller, also maintenance costs should be factored

August 22, 2011

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Chiller upgrade case study

Efficient chillers

http://www.powerpax.com.au/casestudies

Upgrade to Powerpax chillers

August 22, 2011

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References

ABARES 2011, Energy Update 2011, Accessed at < http://adl.brs.gov.au/data/warehouse/pe_abares99010610/EnergyUpdate_2011_REPORT.pdf>.

Department of Climate Change and Energy Efficiency 2010, Report of the Prime Minister’s Task Group on Energy Efficiency, Accessed at <http://www.climatechange.gov.au/~/media/submissions/pm-taskforce/report-prime-minister-task-group-energy-efficiency.pdf>.

Langham, E., Dunstan, C., Walgenwitz, G., Denvir, P., Lederwasch, A., and Landler, J. 2010, Reduced Infrastructure Costs from Improving Building Energy Efficiency. Prepared for the Department of Climate Change and Energy Efficiency by the Institute for Sustainable Futures, University of Technology Sydney and Energetics. Accessed at <http://www.climatechange.gov.au/what-you-need-to-know/~/media/publications/buildings/building_our_savings-pdf.pdf>.

August 22, 2011

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HVAC Energy Efficiency in Commercial Buildings

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