Energy Audits Is about the What, Where, and When energy is used And suggesting how this consumption can be reduced
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Energy Audits Energy Audit will provide: ! financial, ! operational and ! Environmental
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Energy Audits ! Financial Benefits ! Reduced fuel and electricity bills. ! Reduced operation and maintenance costs . ! Reduced capital expenditure.
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Energy Audits ! Operational Benefits ! Improved comfort levels ! Improved efficiency ! Better informed workers on global issues.
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Energy Audits ! Environmental benefits – ! Reduced consumption of finite resources. ! Reduced Pollution levels. ! Improved public image.
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Assessing current building performance Two methods of Energy Audit: ! The Regression Method, and ! The NPI Method.
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Assessing current building performance ! The Regression Method A standard method to assess the energy use in buildings, done by plotting the energy consumption each Month against the Degree days for that month.
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Assessing current building performance ! The Regression Method This will show the trend in Energy consumption, is fitted by a linear relation, from this it is possible to predict future consumption.
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Regression Degree Day Figure
Energy Consumed (GJ)
January
376
185.67
February
359
166.51
March
322
157.56
April
243
124.33
May
162
98.22
June
83
72.6
July
44
56.65
August
48
54.89
September
90
71.66
October
178
103.49
November
275
140.78
December
343
171.62
Month
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150
(kWh)
Energy Consumed
Regression Method
100
50
0 0
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100
200 Degree Day
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300
400
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NPI Method The Normalised Performance Indicator (NPI) comparing the building s energy consumption with similar type buildings.
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Calculating the NPI ! ! ! ! ! ! ! !
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Convert Energy Units to KWh Find the Energy Used for Space Heating Account for Weather Account for Exposure Add Non-Heating Energy Use Account for Hours of Use Factor Find Floor Area (Pool Area) (m2) Calculate the Normalised Performance Indicator (NPI).
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Calculating the NPI ! Step 1 Collate all energy use, Convert Energy Units to KWh 1 therm = 29.31 kWh Natural Gas 1 litre = 10.6 kWh Oil 1 tonne = 7600 kWh Coal
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Calculating the NPI ! Step 2 Find the Energy Used for Space Heating eg a sport centre with a swimming pool 65% of the energy is used in heating on average.
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Calculating the NPI ! Step 3 Account for Weather Weather factor = 2462 / annual degree days
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Calculating the NPI ! Step 4 Account for Exposure Factor = 1 for urban building = 1.1 for Sheltered buildings = 0.9 for Exposed buildings
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Calculating the NPI ! Step 5 Add Non Space heating energy
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Calculating the NPI ! Step 6 Multiply for hours of use Use factor = standard hours / actual hours in use
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Calculating the NPI ! Step 7 Calculate Floor area in square meters
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Calculating the NPI ! Step 8 Calculate NPI = corrected energy used / floor area
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Calculating the NPI ! Step 9 Compare NPI with tabulated values for similar buildings and hence find out in which range of performance does your building lie ?
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Comparisons of performance indicators ! Good - generally have good controls and energy management procedures, but further energy savings are often still possible. ! Fair - reasonable controls and energy management procedures, but significant energy savings should achievable. ! Poor - unnecessarily high consumption and urgent action should be taken to remedy the situation. Substantial energy savings should result from the introduction of energy efficiency measures. 05/04/2011
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Performance Yardsticks For Buildings Good
Fair
Poor
Pub
470
Sports centre with swimming Pool.
840
Theatre
900
Energy Efficiency Rating kWh/m2 per year
Type of Facility
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Savings 1. By altering the physical construction of a building to reduce its heat loss eg double glazing, cavity insulation and loft insulation.
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Savings 2. Replacing/upgrading the equipment and controls to make it more efficient. Time switches, occupancy switches, and Thermostat controls. 05/04/2011
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Savings 3. Shop around for the cheapest tariff.
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Savings 4. Continuous monitoring of Energy consumption.
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Savings 5. Using combined heat and power (CHP) plant to provide electricity and space heating/hot water.
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Case study
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Natural Gas (Therm)
Electricity (kWh)
January
1578
5325
February
1400
5220
March
1309
5400
April
1000
5225
May
750
5300
June
503
5425
July
355
5330
August
350
4990
September
500
5250
October
800
5300
November
1150
5400
December
1460
4880
11,155
63,045
Month
TOTALS
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Gas Data Month
Gas (Therm)
Gas (GJ)
Cost
% Cost
January
1578
166.5
760.44
14.1
February
1400
147.72
675
12.6
March
1309
138.12
631.32
11.7
April
1000
105.52
483
9
May
750
79.14
363
6.7
June
503
53.07
244.44
4.5
July
355
37.46
173.4
3.2
August
350
36.93
171
3.1
September
500
52.76
243
4.5
October
800
84.41
387
7.2
November
1150
121.34
555
10.3
December
1460
154.05
703.8
13.1
11,155
1177.03
5390.4
100
Totals
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Electricity Data Month
Elec. (kWh)
Cost
% Cost
January
5325
429.17
8.4
February
5220
420.77
8.3
March
5400
435.77
8.6
April
5225
42.17
8.3
May
5300
427.17
8.4
June
5425
437.17
8.6
July
5330
429.57
8.5
August
4990
402.37
7.9
September
5250
423.17
8.3
October
5300
427.17
8.4
November
5400
435.17
8.6
December
4880
393.57
7.7
Totals
63,045
5081.6
100
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Energy C onsum ption
16%
N atural G as Electricity
84%
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Energy C ost
49%
51%
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N atural G as Electricity
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Energy C onsum ption 200 150 G as (G J) Electricity (G J)
100 50 0 J an Feb Mar Apr May J un
J ul Aug Sep O ct N ov Dec
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Energy C ost 1000 800 600
G as (£) Electricity (£)
400 200 0 J an Feb Mar Apr May J un
J ul Aug Sep O ct N ov Dec
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Regression Degree Day Figure
Energy Consumed (GJ)
January
376
185.67
February
359
166.51
March
322
157.56
April
243
124.33
May
162
98.22
June
83
72.6
July
44
56.65
August
48
54.89
September
90
71.66
October
178
103.49
November
275
140.78
December
343
171.62
1403.99
1228.83
Month
Regression data
Totals
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The equation is given by : E = 0.365(DD) + 38
Energy Consumed (GJ)
Regression Equation Graph 150
100 50
0 0
100
200
300
400
Regression Degree Day Figure
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1.
Convert your energy use into kWh units
Add your quarterly or monthly use over one year for each fuel and enter below Natural gas Electricity Total energy use for the year
{ Therms x 29.31 kWh x 1
= 11155 x 29.31 =326953 = 63045 =389998
kWh kWh kWh
A
kWh
B
kWh kWh kWh
C D E
2.Find your space heating energy use If you can identify any of the fuels above used only for space heating, enter the total energy use in kWh Add these to give total
0
If you cannot identify these then choose one of the following factors applied to the total energy used. For light industrial factory building Annual space heating energy Annual non-space heating energy
Space heating factor = 0.80 A x 0.80 = 389998x0.80 = 311998 B or C = 311998 A-D = 389998- 311998= 77999
3. Adjust the space heating energy to account for weather • • •
Find the Degree Days for the energy data year = 2523 The weather correction factor = 2462/2523 = 0.976 Adjust the space heating energy to standard conditions
kWh
F G H
= D x G =311998x0.976=304455
4. Adjust the space heating energy to account for exposure •
Obtain the exposure factor from this chapter to suit the location of the building = 1
•
Adjusted space heating energy = H x J =
304455 x 1
=
304455
5. Find normalised annual energy use = E + K = 77999 + 304455 = 382454
J kWh
K
kWh
L
6. Correct for hours of use of building •
Obtain standard hours of use = 2000
M
•
Calculate the annual hours of use for your building -= 9x5x48
•
Hours of use factor
•
Annual energy use for standard hours
M / N =2000/2160
= =
2160 0.926
P x L = 0.926x 382454 = 354152
7. Find floor area = 25 x 25 = 625 m2 8. Find the Normalised Performance Indicator (NPI) = Q / R = 354152/ 625 = 566 9. Compare with yardstick - [ 180 to 240 kWh/m2 ] Excessive Energy consumption
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N P kWh
Q
m2
R
kWh/m2 POOR
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Calculation of Heat Losses width
height
D
W
W
depth
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Element
U-value W/m2K
Area m2
Temp. Difference (oC)
Heat loss W
Door
2
18
12.5
450
Windows
5.3
42
12.5
2782
Walls
2.3
360
12.5
10350
Roof
2.6
900
12.5
29250
Floor
0.26
900
12.5
2925
Fabric heat loss = TOTAL ( Doors, Windows, Walls, Roof & Floor) 45757 Ventilation Heat Loss
= 0.335 N V ΔT 15600 N=1.2 0
Heat gains from occupants Heat gains from lights 0 Heat gains from machines 0 Net heat transfer for the building 61357
