Energy Conservation
Energy
Management
Role of an energy manager
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Assess
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Analyse
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On technical improvements
Advertise
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Energy requirements
Advise
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Current energy demand
Energy audit
Ways to save energy
Account
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For energy consumption
Assess energy demand
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Keep records
 Consumption
 Time of readings
 Temperature
 Other factors affecting demand
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Weekday/weekend
Special events
Frequency of readings
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Weekly
Daily
Energy Audit
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Feasibility study
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Aim
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Establish and quantify energy flows into and within a
building or organisation
Identify viable and cost effective energy saving
measures
Enhance operating efficiency and reduce
maintenance costs
Establish a baseline energy consumption
Process
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Collect data from energy invoices and meters
Surveys of plant, equipment and buildings
Collect information from managers and other staff
Auditing process
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Identify energy management
opportunities
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Can be ‘no cost’ or ‘low cost’ measures
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Change an energy tariff
Change an energy supplier
Reschedule production activities
• Preferential tariffs
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Adjust existing controls to match requirements
Implement ‘good housekeeping’ policies
Invest in small capital items
• Thermostats & time switches
Who does energy audits?
Can be undertaken internally – energy manager
 Specialist energy consultants
 Energy service companies
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Performance contracts
Guarantee organisations energy cost savings in
return for a fee
Main interest is in installing and managing their
recommended plant
May arrange finance of projects
Vested interest
Why is energy wasted?
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Poorly designed buildings and
installations
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Insufficient insulation
Undersized ventilation ducts
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Inadequate control systems
 Poor control settings
 Inefficient plant operation
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Out of date technology
Poor maintenance
Poor operating and working
practices
Different types of energy audit
 According
to level of detail and depth of
analysis
 Preliminary
 Targeted
 Comprehensive
Preliminary audit
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How much energy is being consumed
 What type of energy
 Performance of facility compared with
similar facilities
 Characteristic performance of building
Preliminary energy audit
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Identification of potential areas of energy
saving
Financial energy audits
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Collect data
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Establish quantity and cost of each form of
energy
Data from energy invoices and meters for
previous year
Analyse data
 Present data
 Establish priorities
 Make recommendations
Targeted energy audit
 Provide
data and analysis on specific
targeted projects
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e.g. heating of one building or lighting
 Detailed
survey of target area
 Analysis of energy flows and costs
 Recommendations for action
Comprehensive energy audits
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Similar to preliminary audits but in far
more detail
 Detailed data on energy flows into
and within organisation or facility
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Often requires use of sub-metering to
accurately determine component energy
flows
Or estimate energy use
(Plant power output (kWh)/efficiency of
plant) *operating hours per year
Use of thermal imaging
May use complex energy simulation
software
Detailed energy survey
Energy project implementation plans
Collect data
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Build up picture of pattern of energy consumption and
cost from energy invoices
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Collect geographic data
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Location, altitude, orientation
Weather data, degree day data
Manufacturing data (if appropriate)
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All invoices for relevant time period
Delivery notes for oil, solid fuel, LPG
Identify estimated meter readings – check with previous years
Inadequate/unavailable invoices – contact utility company/fuel
supplier
Production output
Check data for anomalies
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Small building using more energy than larger one
High energy use at night when unoccupied
Understanding invoices: electricity
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Date of meter reading
Monthly standing charge
Present and previous meter reading
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Charges for each rate
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For every kW of the peak power demand during the month
Penalise users make heavy demands during peak periods
Supply capacity – annual maximum demand
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Some tariffs have a higher unit charge for first 1000 kWh
Monthly maximum demand charge
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Daytime – peak rate
Night time – off-peak rate
Monthly charge
Total cost + VAT
Gas invoices
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Much less complicated than electricity
Date of meter reading or estimate
Calorific value of gas
Present and previous meter readings
Amount of gas used
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ft3, kWh or therms
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Unit price per kWh
 Standing charge
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Monthly or quarterly
Total cost + VAT
Other fuels
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Fuel oil
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Measured by volume
• Varies with temperature corrected to standard condition of
15.50C
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Date of delivery
Unit cost per standard litre
Calorific value (?)
Total cost + VAT
Solid fuel
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Weight delivered
Date of delivery
Total cost + VAT
No calorific value
Analysing energy records
 Key
variables
 Heating
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External temperature - dominant
Wind speed )
Humidity
) <=10% variation
Solar gain )
 Lighting
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Hours of darkness
Data analysis
Many different ways of analysing data
 Annual energy consumption
 Analysis of heating requirements
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Degree day method
Mean temperature method
Cumulative deviation method
(Details in Keith’s lecture notes)
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Normalised performance indicators (NPI)
(Beggs, 2002)
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Time dependent energy analysis
Linear regression analysis
CUSUM – cumulative sum deviation method
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Annual energy consumption
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Simplest analysis
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Assess overall energy performance of building
Produces a percentage breakdown of annual energy
consumption and cost data
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Convert all energy consumption data into standard units (kWh)
• Standard conversion factors & gross calorific values
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Percentage breakdowns of total consumption and cost of each
energy type
Present data
•
•
•
•
Total annual energy consumption
Cost
Percentage breakdown of each fuel type
Historical trends
Analysis of heating requirements
 Degree
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day method
Quicker
Oil & coal heating difficult – general estimates
of consumption
Mean temperature method
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More accurate
Plot mean consumption against mean
external temperature
Degree day method
Two component parts
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Temperature related
Independent of temperature
• Hot water & cooking if by gas
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E = W + H*degree days*86400
• Where E is total energy consumed
• W energy for hot water + cooking (gas)
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W approx constant for given house – 7-10 GJ/quarter
• H is heat loss rate for the home
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Two unknowns W & H,
Know degree days & energy consumption
Estimate heat loss & steady energy requirement
Degree day method - example
Energy consumption 2 successive quarters
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31.76 & 18.80 GJ
Corresponding degree days
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1100 and 500
E = W + H * degree days*86400
1100 * H * 86400 + W = 31.76 (1)
500 * H * 86400 + W = 18.80 (2)
Simultaneous equations (subtract 2 from 1)
H = (31.76 – 18.80) * 109 = 250 Watts
(1100-500)*86400
Substitute for H in either equation to get W
W = 31.76 * 109 - 1100 * 250 * 86400
= 8 * 109 = 8GJ
H - heat loss
W - hot water
Degree day method
Once H & W have been calculated
 Performance for subsequent quarters can
be estimated
 If degree days for 3rd quarter = 400
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 If
Consumption predicted to be
400 * 250 * 86400 + 8 * 109 = 16.64 GJ
actual consumption is 17.5 GJ then
energy has been wasted
Mean temperature method
(non electrical heating)
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Plot the mean consumption over a specific period
against mean external temperature
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For 1 week or 1 day - less time than previous method
Analysis of lighting
(non-electrically heated house)
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Lighting varies throughout
the year with hours of
darkness
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Need to assess a realistic
time for lighting
There is constant load (A)
from appliances and
refrigeration use and an
increasing amount from
lighting.
Increase in lighting hours
is used to obtain L & A in
same way for H & W in
heating example
Analysis of heating & lighting in an
electrically heated house
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More complex as both H & L are unknown
 Combine A & W to give overall appliance + hot water
load (A)
 E = (degree days * H + lighting hours * L) * 86400 + A
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3 unknowns – H, L & A
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Where E = energy consumption
H = heat loss rate
L = lighting (units of L are Watts per hour)
A = appliance + hot water
If we have data for 3 quarters
Estimate values for H, L & A by solving 3 simultaneous equations
If appliance load is known calculation is easier
Cumulative deviation method
1.
2.
3.
4.
5.
6.
No energy conservation
– horizontal line
Winter following
improved insulation
Summer – no savings –
heat conservation only
Winter – parallel to 2
Summer - improved
management of hot
water
Should be (4) + (5) but
less - energy
conservation
performance is reduced
Normalised Performance Indicators (NPIs)
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Provides an indication of the energy performance of a building
Compares actual annual energy consumption and costs with those
achieved by buildings of a similar type and function
Problems
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Correct the building energy consumption data
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allow for variables such as occupancy and weather.
NPIs developed to address these problems. Used to
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Buildings may be different sizes
Locations may have different climates
Locations may have different levels of exposure
Maybe different operating hours
compare with other buildings of a similar type and function
compare with standard energy benchmark for different building types
Benchmarks
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Many countries have national energy benchmarks for different types of
buildings
Usually kWh/m2 of floor area (volume)
Provide guidance, not absolute values to achieve
How to calculate NPIs
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Establish total building energy use in standard units
Calculate the annual energy use for space heating
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Sub-metering, or analytical techniques
Correct space heating energy data for climate & exposure
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Weather coefficient = std annual heating degree days/ annual heating
degree days experienced by building
Exposure coefficients
• Sheltered (city centre) = 1.1
• Normal (urban/rural) = 1.0
• Exposed (coastal/hilly site) = 0.9
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Non-heating energy consumption + corrected space heating = nontime corrected energy consumption
To calculate normalised annual energy consumption need to correct
for ‘hours of use’
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non-time corrected energy consumption * coefficient
Hours of use coefficient = std annual hours of use/actual annual hours
of use
NPI = normalised annual energy consumption/building floor area
Energy Surveys
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Integral part of energy audit
Helps to understand energy flows within a
facility/building
Helps to identify energy wastage
Can be comprehensive or targeted
Objectives
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Determine energy performance of facility/building or specific
plant/equipment
Identify and quantify the principal energy flows & energy cost
savings
Produce costed recommendations to achieve energy cost
savings
Make recommendations on future energy management of
facility
What to include in an energy survey
 Management
and operation characteristics
of a facility or organisation
 Energy supply to an organisations various
facilities
 Energy use within an organisations
facilities
 The plant and equipment within a facility
 The fabric of the organisation’s buildings
Management and operating characteristics
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Management culture
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Can have considerable influence on energy
consumption
Determine management structure and
practices relating to energy procurement
and consumption
Identify cost centres
• Are the managers accountable for operating
costs also responsible for energy consumption?
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Maintenance procedures
• Frequency and quality
• Identify new maintenance measures to improve
energy efficiency
Operating practices: data collection
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Use of particular space or building
Mechanical/electrical services in building
Number & type of occupants e.g. stationary or
active
 Occupancy patterns
 Environmental conditions
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Air temp, humidity, lighting
Operating practices of plant/equipment
Identify where actual practices deviate from that
stated by management
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Overheated rooms, open windows, computers left on
Energy Supply
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Identify tariffs and supply contracts of organisation
Ensure organisation is using correct electricity tariff
to suite its load profile
Calculate load profile
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Regular meter readings – include daytime, night time &
weekends
For large electrical loads
• Need to be more accurate
• Measure every 30 mins, use portable meters if necessary
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Investigate large peaks in load
Plant and equipment
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Survey major items of plant and equipment to determine their
operating efficiency
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Boilers
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Check efficiency
Opening practices
Is heat recovery feasible
Pipework
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‘tune’ to minimise flue gas heat loss
Identify if flue gas heat recovery is feasible
Refrigeration
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Include pipe distribution networks
Insulation & leaks
Planned replacement of old plant
Building fabric
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Identify using U values areas of greatest heat loss
Thermal imaging
Excess ventilation – open doors
Energy management: recommendations
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Recommendations will relate to cost of fuel – more interested in
saving money than energy/carbon
Technical
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Energy management
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Checking performance
Record keeping
Financial
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Insulation, draft exclusion, thermostatic radiator valves, heating control
Low energy lighting, efficient refrigeration
Power factor corrections
Relocation of switches, movement sensors
Make sub-sections responsible for their own energy budget
‘Carrots’ for those who save energy
Other factors
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Change patterns of working
Working practices
Use of space