Energy Conservation
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Transcript Energy Conservation
Energy Conservation
Energy
Management
Role of an energy manager
Assess
Analyse
On technical improvements
Advertise
Energy requirements
Advise
Current energy demand
Energy audit
Ways to save energy
Account
For energy consumption
Assess energy demand
Keep records
Consumption
Time of readings
Temperature
Other factors affecting demand
Weekday/weekend
Special events
Frequency of readings
Weekly
Daily
Energy Audit
Feasibility study
Aim
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
Collect data from energy invoices and meters
Surveys of plant, equipment and buildings
Collect information from managers and other staff
Auditing process
Identify energy management
opportunities
Can be ‘no cost’ or ‘low cost’ measures
Change an energy tariff
Change an energy supplier
Reschedule production activities
• Preferential tariffs
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
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?
Poorly designed buildings and
installations
Insufficient insulation
Undersized ventilation ducts
Inadequate control systems
Poor control settings
Inefficient plant operation
Out of date technology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
How much energy is being consumed
What type of energy
Performance of facility compared with
similar facilities
Characteristic performance of building
Preliminary energy audit
Identification of potential areas of energy
saving
Financial energy audits
Collect data
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
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
Similar to preliminary audits but in far
more detail
Detailed data on energy flows into
and within organisation or facility
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
Build up picture of pattern of energy consumption and
cost from energy invoices
Collect geographic data
Location, altitude, orientation
Weather data, degree day data
Manufacturing data (if appropriate)
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
Small building using more energy than larger one
High energy use at night when unoccupied
Understanding invoices: electricity
Date of meter reading
Monthly standing charge
Present and previous meter reading
Charges for each rate
For every kW of the peak power demand during the month
Penalise users make heavy demands during peak periods
Supply capacity – annual maximum demand
Some tariffs have a higher unit charge for first 1000 kWh
Monthly maximum demand charge
Daytime – peak rate
Night time – off-peak rate
Monthly charge
Total cost + VAT
Gas invoices
Much less complicated than electricity
Date of meter reading or estimate
Calorific value of gas
Present and previous meter readings
Amount of gas used
ft3, kWh or therms
Unit price per kWh
Standing charge
Monthly or quarterly
Total cost + VAT
Other fuels
Fuel oil
Measured by volume
• Varies with temperature corrected to standard condition of
15.50C
Date of delivery
Unit cost per standard litre
Calorific value (?)
Total cost + VAT
Solid fuel
Weight delivered
Date of delivery
Total cost + VAT
No calorific value
Analysing energy records
Key
variables
Heating
External temperature - dominant
Wind speed )
Humidity
) <=10% variation
Solar gain )
Lighting
Hours of darkness
Data analysis
Many different ways of analysing data
Annual energy consumption
Analysis of heating requirements
Degree day method
Mean temperature method
Cumulative deviation method
(Details in Keith’s lecture notes)
Normalised performance indicators (NPI)
(Beggs, 2002)
Time dependent energy analysis
Linear regression analysis
CUSUM – cumulative sum deviation method
Annual energy consumption
Simplest analysis
Assess overall energy performance of building
Produces a percentage breakdown of annual energy
consumption and cost data
Convert all energy consumption data into standard units (kWh)
• Standard conversion factors & gross calorific values
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
day method
Quicker
Oil & coal heating difficult – general estimates
of consumption
Mean temperature method
More accurate
Plot mean consumption against mean
external temperature
Degree day method
Two component parts
Temperature related
Independent of temperature
• Hot water & cooking if by gas
E = W + H*degree days*86400
• Where E is total energy consumed
• W energy for hot water + cooking (gas)
W approx constant for given house – 7-10 GJ/quarter
• H is heat loss rate for the home
Two unknowns W & H,
Know degree days & energy consumption
Estimate heat loss & steady energy requirement
Degree day method - example
Energy consumption 2 successive quarters
31.76 & 18.80 GJ
Corresponding degree days
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
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)
Plot the mean consumption over a specific period
against mean external temperature
For 1 week or 1 day - less time than previous method
Analysis of lighting
(non-electrically heated house)
Lighting varies throughout
the year with hours of
darkness
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
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
3 unknowns – H, L & A
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)
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
Correct the building energy consumption data
allow for variables such as occupancy and weather.
NPIs developed to address these problems. Used to
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
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
Establish total building energy use in standard units
Calculate the annual energy use for space heating
Sub-metering, or analytical techniques
Correct space heating energy data for climate & exposure
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
Non-heating energy consumption + corrected space heating = nontime corrected energy consumption
To calculate normalised annual energy consumption need to correct
for ‘hours of use’
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
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
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
Management culture
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?
Maintenance procedures
• Frequency and quality
• Identify new maintenance measures to improve
energy efficiency
Operating practices: data collection
Use of particular space or building
Mechanical/electrical services in building
Number & type of occupants e.g. stationary or
active
Occupancy patterns
Environmental conditions
Air temp, humidity, lighting
Operating practices of plant/equipment
Identify where actual practices deviate from that
stated by management
Overheated rooms, open windows, computers left on
Energy Supply
Identify tariffs and supply contracts of organisation
Ensure organisation is using correct electricity tariff
to suite its load profile
Calculate load profile
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
Investigate large peaks in load
Plant and equipment
Survey major items of plant and equipment to determine their
operating efficiency
Boilers
Check efficiency
Opening practices
Is heat recovery feasible
Pipework
‘tune’ to minimise flue gas heat loss
Identify if flue gas heat recovery is feasible
Refrigeration
Include pipe distribution networks
Insulation & leaks
Planned replacement of old plant
Building fabric
Identify using U values areas of greatest heat loss
Thermal imaging
Excess ventilation – open doors
Energy management: recommendations
Recommendations will relate to cost of fuel – more interested in
saving money than energy/carbon
Technical
Energy management
Checking performance
Record keeping
Financial
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
Change patterns of working
Working practices
Use of space