Building automation – impact on energy efficiency - Siemens ...

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4.4.4 Sample calculation for an office building

Application of the BACS efficiency factors when calculating the ong>impactong> of BACS

and TBM on overall energy efficiency of a medium-sized office building (length

70 m, width 16 m, 5 floors). BACS efficiency class C is used as the reference.

Improvements to energy efficiency by changing to BACS efficiency class B

are calculated.

Description

No.

Unit Heating Cooling

Calculation

Ventilation

Lighting

Thermal energy

Energy demand 1

kWh

m 2 • a

100 100

Plant losses

Reference case

2

kWh

m 2 • a

33 28

Energy expense for

reference class C

3 Σ 1 + 2

kWh

m 2 • a

133 128

BACS factor thermal

Reference class C

BACS factor thermal

Actual case (class B)

4 1 1

5 0,80 0,80

Energy expense actual

case (class B)

6

5

3 ×

4

kWh

m 2 • a

106 102

The expense of thermal energy must be distributed among various energy carrier to complete the

calculation.

Electrical energy

Auxiliary energy class C 7a kWh 14 12 21

Lighting energy

7b

m 2 • a 34

BACS factor electrical

8 1 1 1 1

Reference class C

BACS factor electrical

Actual case (class B)

Auxiliary energy

actual case (class B)

9 0,93 0,93 0,93 0,93

10

9

7 ×

8

kWh

m 2 • a

13 11 20 32

Results

After transforming the office building by updating BACS functions from the

BACS efficiency class C to class B, energy consumption per BACS efficiency

factors published in EN 15232 were reduced as follows:

• Heating energy 106 kWh/m 2 • a instead of 133 Reduction to 80 %

• Cooling energy 102 kWh/m 2 • a instead of 128 Reduction to 80 %

• Electrical energy 76 kWh/m 2 • a instead of 81 Reduction to 93 %

These improvements in energy efficiency lead to annual energy savings of

324,800 kWh for the entire building (5,600 m 2 ).

88

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