residential energy audit velasco
DESCRIPTION
This is a graduate paper on an energy audit for a residential unit. It is for the course Energy Conservation. The paper relates the consumption of the residents to the average energy consumption of a household per unit area. Several conservation measures are then recommended to lower down the consumption without suffering discomfort.TRANSCRIPT
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Energy Engineering Program
National Graduate School of Engineering
University of the Philippines Diliman
RESIDENTIAL ENERGY AUDIT
The Case of the Madrid Residence
A Paper for the Course:
EgyE 211: Energy Conservation
by
Naason G. Velasco
August, 2013
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Auditors Page
The auditor has a degree in Bachelor of Science in Chemical Engineering from Saint Louis
University. The auditor has experience in quality assurance for food manufacturing
specifically in edible oils. The auditor has also been employed in a trading company
specializing in pharmaceuticals and cosmetics. He was the Product Scientific Communication
Officer where he conducted research and development activities and relaying it to the sales
team. He also headed the Equipment and Medical Devices section of the said company as
Sales and Marketing Development Officer.
The auditor also worked for the national government at the Philippine Council for Industry,
Energy, and Emerging Technology Research and Development of the Department of Science
and Technology. He was a Science Research Specialist I at the Material Science Section of
the Emerging Technology Development Division. He provided research management
assistance to approved projects and provided Technical Panels assistance in evaluating
project proposals. He was also part of the monitoring team of several research projects
mainly based at the National Institute of Physics, University of the Philippines Diliman.
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Executive Summary
The eminent problem in energy and climate change is the primary driver of the energy
conservation activities. The activities aim to identify energy conservation opportunities and
formulate sound policies based on energy audits.
The energy audit is conducted using a standard framework where energy cost centers are
identified and simulated. The computed energy consumption where then compared to actual
consumptions based on electric bills. Cost centers where then rank to identify major
contributors. Energy conservation measures were then identified with these cost centers. The
carbon footprint for each process where also identified. The effectiveness of the conservation
measures where measured by different econometrics.
The house has energy intensity of 3696.3 MJ/person and 169.94 MJ/m2 on annual basis. The
major contributors of energy consumption for the area of the study are air conditioning,
refrigeration, lighting and data processing. The energy conservation measures resulted in
135.5664 kWh avoided energy per year that corresponds to 172.9827 lbs of avoided carbon
dioxide emissions per year and yearly savings of P 1,533.26. All of the energy conservation
measures passed the econometrics.
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Table of Contents
Auditors Page .. 2 Executive Summary . 3 Section 1 Introduction ... 5 Section 2 Methodology . 7 Section 3 Energy Data Gathered . 12 Section 4 Energy and Environmental Analysis ... 16 Section 5 Energy Conservation Measures ... 18 Section 6 Energy Management Plan ... 22 Conclusions and Recommendation 23 References .. 24 Appendix 25
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Section 1 Introduction
The objectives of the audit are as follows:
Identify energy conservation opportunities
Minimize energy consumption without jeopardizing safety and comfort
Minimize carbon footprint
Evaluate economic feasibility of each energy conservation measures
The area of study is the Unit A of Madrid Residences located in the map below
captured via Google Maps.
Figure 1.1: Location of the Madrid residence within Malanday, Marikina City
Unit A of Madrid Residences is located at the most eastern side of the apartment
building shown in Figure 1.2 below.
Figure 1.2: Location of Unit A within the apartment building
Unit G Unit F Unit E
Unit A Area of Study
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The apartment unit has two (2) floors and an attic. The layout of the house is
presented in the figures below.
(a) (b) (c)
Figure 1.3: (a) 1st floor; (b) 2
nd floor; (c) attic
The first floor has 27 square meters in area while the second floor and the attic has 30
square meters in area. It should be noted that the air conditioner has been installed at BR 1.
There are 2 adults and 2 children occupying the said apartment unit. The 2 adults occupy the
air-conditioned bedroom. All of the occupants typically leave the house at 8 a.m. for work or
school and they come back at 4 p.m. They occupied the said unit since late 2010.
The materials of construction are similar with normal concrete apartment buildings.
Table 1.1: Materials of Construction
MOC
Roof galvanized iron
Ceiling plywood
Walls painted concrete
Floor tiled concrete
Windows single glass
Doors wood
All of the energy cost centers are appliances and are listed in Section 3 of the paper.
T & B
Terrace
BR 1
BR 2
T & B
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Section 2 Methodology
The audit conducted is functional as it is expected with residential audits. The audit
was conducted on walk-through basis but developed into energy survey and analysis when
the owner of the house became more comfortable on the process. The data gathering however
was still difficult as the owner of the unit was hesitant in giving information. Several
assumptions were then made while doing the audit, which will be discussed in the succeeding
sections.
The building envelope audit was done very conservatively and assumptions such as
desired room temperature and temperature of rooms affected in the computations were also
assumed.
Figure 2.1: Flowchart of the energy audit
The system boundary was defined and the area of study was delineated. The
dimensions of the house, materials of construction, appliance list, hours of operation, and bill
data were gathered. R-values, area and wattage were then identified to be used in modeling.
For modeling, the following equations were utilized:
Set system boundary
Data gathering
Modeling
Validation of model
Implementation
Forecasting
MOC Appliance
Electric bill
R-values Wattage Actual
Consumption Energy Cost
Centers Computed
Consumption
Corrected Computed
Consumption Conservation Policies
Savings
Area of study Energy balance
Computed and actual
Consumption
Current Consumption
Forecasted Consumption
(with or without conservation)
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Computed Monthly Power Consumption
where:
P - calculated monthly power consumption in kWh
Pi - monthly power consumption for each process in kWh
n - number of processes
where:
Pi - monthly power consumption for each process in kWh
pi - monthly power consumption for each appliance in kWh
n - number of appliances for each process
In computing for the monthly power consumption, the power company MERALCO
provides an easy to use appliance calculator that involves inputting the type of appliance,
wattage, number of hours used per day, number of days per week, and number of week per
month. The appliance calculator will give an estimate of monthly consumption for each
appliance.
The formula used by MERALCO appliance calculator in estimating monthly power
consumption for each appliance has been utilized in this energy audit because of its
simplicity and its compatibility with the gathered data.
Air Conditioning
where:
pAC - monthly power consumption for air conditioning in kWh
WAC - power rating of air conditioning unit in watts (W)
HAC - number of hours of air conditioning per month
Refrigeration
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where:
pR - monthly power consumption for refrigeration in kWh
WR - power rating of refrigeration unit in watts (W)
HR - number of hours of refrigeration per month
Other Appliances
where:
pO - monthly power consumption for other appliances in kWh
WO - power rating of other appliances in watts (W)
HO - number of hours the other appliances were used per month
For the computation of cooling load the figure below is considered:
Figure 2.2: Layout of 2
nd floor with adjacent unit
It was assumed that 30 C was the outside temperature and the temperature inside the
house is 27 C while the desired temperature of the room to be air-conditioned is 24 C. The
heat gained by the building envelope was then computed using the standard equation for heat
conduction
. The effects of convective-radiative heat transfer were accounted by
integrating the convective-radiative R-values in the equation. The internal heat gains were
also computed accounting appliances and persons occupying the air-conditioned room.
In determining the carbon footprint, the carbon emissions were computed using the
Philippine Power Mix for 2010 provided by the Department of Energy as basis. After
24 C
27 C
27 C
30 C
27 C
3 m
3 m
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determining the national average carbon emission per MWh of electricity (1276 lbs/MWh),
the carbon emissions of the house was then computed. The same basis was also used in
computing for the avoided carbon emissions for each energy conservation measures.
Table 2.1: Carbon Emissions by Energy Source
Source GWh MWh lbs CO2/MWh CO2, lbs
oil 7101 7101000 1672 11872872000
hydro 7803 7803000 0 0
geothermal 9929 9929000 0 0
coal 23301 23301000 2249 52403949000
other RE 90 90000 0 0
natural gas 19518 19518000 1135 22152930000
Total
67742000
86429751000
The model was validated by comparing to the actual energy consumption, which was
determined by averaging monthly consumptions based on MERALCO metering.
Using Pareto analysis, the major energy consuming centers that consume 80% of the
total consumption were determined. Energy conservation measures were then provided for
each process basing on the cause-effect diagram. Energy avoided, carbon emissions avoided,
and cost savings were then identified for each process. Each energy conservation measures
were evaluated using economic analysis of energy systems. Several equations were used in
the process.
Simple Payback Period
where:
IC initial capital cost AES annual energy savings Pr price of energy
Return on Investment
Cost of Conserved Energy
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where:
CRF capital recovery factor
O&M cost of operations and maintenance
Present Value Savings
where
UPVF uniform present value factor
Net Present Value
Benefit-Cost Ratio
For an energy conservation measure to be acceptable SPP should be lesser than n,
CCE should be lesser than Pr, PVS should be greater than IC, NPV should be greater than
zero, and B/C should be greater than 1.
Section 3 Energy Data Gathered
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Electric Bills
Figure 3.1: Printed bills of Unit A
Figure 3.2: Billing history of Unit A (MERALCO)
Materials of Construction
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Table 3.1: Materials of Construction of Unit A
MOC
Roof galvanized iron
Ceiling plywood
Walls painted concrete
Floor tiled concrete
Windows single glass
Doors wood
Occupancy
Entire house: 4 persons
Air-conditioned room: 2 persons
Energy Cost Centers
Table 3.2: Ventilation and Airconditioning
Energy Cost
Centers Quantity
Brand/
Type/
Model
Power
Rating
(W)
Usage
(hrs/mo)
Consumption
(kWh/mo) Total
VAC
154.326
Aircon 1
Carrier
(window) 855 180 129.276
Electric
fan1 1 Mikata 65 150 9.75
Electric
fan2 1 Mikata 65 180 11.7
Exhaust
fan 2 Standard 30 60 3.6
Table 3.3: Lighting
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Energy Cost
Centers Quantity
Brand/
Type/
Model
Power
Rating
(W)
Usage
(hrs/mo)
Consumption
(kWh/mo) Total
Lighting
36.076
CFL1 5 Philips 5 150 3.75
CFL2 1 Osram 20 360 7.2
LED1 1 Landlite 4 4 0.016
CFL3 1 Osram 23 210 4.83
CFL4 1 Osram 23 60 1.38
CFL5 1 Osram 23 270 6.21
LED2 1 Omni 0.5 180 0.09
CFL6 8 Osram 20 45 7.2
CFL7 1 Osram 20 270 5.4
Table 3.4: Entertainment
Energy Cost
Center Quantity
Brand/
Type/
Model
Power
Rating
(W)
Usage
(hrs/mo)
Consumption
(kWh/mo) Total
Entertainment
21.42
TV1 1
Devant
40" LCD 115 120 13.8
TV2 1 TCL
32" LCD 95 60 5.7
Cable Box 2 Cignal 8 120 1.92
Table 3.5: Communications and Data Processing
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Energy Cost
Center Quantity
Brand/
Type/
Model
Power
Rating
(W)
Usage
(hrs/mo)
Consumption
(kWh/mo) Total
Communications
0.375
mobile
phone 5 assorted 5 15 0.375
Data
Processing 32.7
desktop 1 - 200 150 30
broadband
modem 1 Globe 18 150 2.7
Table 3.6: Laundry and Refrigeration
Energy Cost
Center Quantity
Brand/
Type/
Model
Power
Rating
(W)
Usage
(hrs/mo)
Consumption
(kWh/mo) Total
Laundry
11.62
washing
machine 1 Sharp 380 24 9.12
flat iron 1
Fine
Elements 500 5 2.5
Refrigeration
65.1
ref1 1 National 85 720 35.7
ref2 1 Sanyo 70 720 29.4
Table 3.7: Cooking and Beautification
Energy Cost
Center Quantity
Brand/
Type/
Model
Power
Rating
(W)
Usage
(hrs/mo)
Consumption
(kWh/mo) Total
Cooking
23.775
rice cooker 1 Carribean 700 30 21
electric
kettle 1
Kyowa
1.7L 1850 1.5 2.775
Beautification
12
blow dryer 1
Fuller
Home 1200 10 12
Section 4 Energy and Environmental Analysis
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Current House Profile
Energy Per Occupant: 3696.3 MJ/person (annual basis)
Energy Per Area: 169.94 MJ/m2 (annual basis)
Table 4.1: Actual Energy Consumption and Carbon Emissions
Year Energy, kWh/yr CO2, lbs/yr
2011 3432 4379.232
2012 4019 5128.249
2013 4107 5240.532
The energy consumptions are based on Meralco bill of Unit A. The carbon emissions
were computed for each year using 1,276 lbs/MWh as basis (as per 2010 Philippine Power
Mix).
Table 4.2: Computed Energy Consumption per Process
Process Consumption
(kWh/mo)
VAC 154.326
Refrigeration 65.100
Lighting 36.076
Data Processing 32.700
Cooking 23.775
Entertainment 21.420
Beautification 12.000
Laundry 11.620
Communications 0.375
Total 357.392
The computed monthly energy consumption is 4.424% overestimation of the actual
monthly energy consumption. Since the difference between estimated and actual
consumption is less than 5%, the computed consumption was then accepted.
Table 4.3: Building Envelope Heat Gain
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Area,
ft2
MOC R-value,
h.ft2.F/Btu
Toutside, F Tinside, F Q, Btu/h Q, W
north
wall 100.98
painted
concrete 1.96 86.00 75.2 556.42 163.07
south
wall 112.98
painted
concrete 1.96 80.60 75.2 311.27 91.23
east
wall 91.98
painted
concrete 1.96 80.60 75.2 253.41 74.27
west
wall 112.98
painted
concrete 1.96 80.60 75.2 311.27 91.23
floor
(2nd) 96.84
tiled
concrete 2.01 80.60 75.2 260.17 76.25
floor
(attic) 96.84
tiled
concrete 2.01 80.60 75.2 260.17 76.25
window 12.00 single
glass 0.91 86.00 75.2 142.42 41.74
door 21.00 wood 2.17 80.60 75.2 52.26 15.32
Total 2147.39 629.34
It should be noted that most of the heat gained through the building envelope was
from the north wall because it is the only wall exposed to the outside environment. The
window is also located on the north wall.
Table 4.4: Internal Heat Gains
Appliances
Q, W
light bulbs 2.50
TV 7.92
Occupants
2 adults 47.62
Total
58.04
The cooling load is 687.39 W.
Section 5 Energy Conservation Measures
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Pareto Analysis
Figure 5.1: Pareto diagram
The processes that encompassed the 20%-80% criterion were air-conditioning,
refrigeration, lighting, and data processing.
Cause and Effect Analysis
Figure 5.2: Ishikawa diagram for air-conditioning
0
10
20
30
40
50
60
70
80
90
100
0
50
100
150
200
250
300
350
kW
h
Monthly Consumption
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Figure 5.3: Ishikawa diagram for refrigeration
Figure 5.4: Ishikawa diagram for lighting
Figure 5.5: Ishikawa diagram for data processing
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Energy Conservation Measures
Air-conditioning
As it is imperative that the construction materials and layout of the room that is
affected should not be altered, the easiest way to conserve energy when using air-conditioned
is to install blinds on windows. Blinds add insulation (R-value = 0.29 h.ft2.F/Btu) to the
building envelope decreasing energy consumption.
Conservation Measure: Install blinds
Current: 41.74 W (Qwindow)
After conservation measure: 31.65 W (Qwindow)
Energy avoided: 1.8162 kWh per month
CO2 avoided: 2.3175 lbs per month (Basis: 1276 lbs per MWh national average) Cost Savings: P 20.54 per month (Basis: P 11.31 - Meralco rate)
Refrigeration
Clean the condenser coils at the back or underneath the fridge or freezer 2-3 times a
year as dust and dirt causes the fridge to work harder and run for longer cycles. The energy
consumption can be reduced by 6% per year.
Conservation Measure: Clean condenser coils thrice a year.
Current: 65.1 kWh per month = 781.2 kWh per year
After conservation measure: 734.328 kWh per year
Energy avoided: 3.906 kWh per month
CO2 avoided: 4.9841 lbs per month (Basis: 1276 lbs per MWh national average) Cost Savings: P 44.18 per month (Basis: P 11.31 - Meralco rate)
Lighting
Most exhaustive: CFL6 (20 W) = 7.2 kWh w/ 1100 lm
Conservation Measure: Replace CFL6 with 25 W LED (1800 lm)
8 CFL6 = 5 LED
Energy avoided: 1.575 kWh per month
CO2 avoided: 2.0097 lbs per month (Basis: 1276 lbs per MWh national average) Cost savings: P 17.81 per month (Basis: P 11.31 - Meralco rate)
Data Processing
There is a power surge when turning on computer but this is very minimal as
compared to running computer when not needed. It should also be noted that screen savers
are not energy savers. It is recommended then to do the following:
Turn off the monitor if not using PC for more than 20 minutes.
Turn off both the CPU and monitor if not using PC for more than 2 hours.
The Labour Department of Hong Kong recommends taking 15-minute breaks
between 1-2 hours of continuous computer work to avoid eyestrain. It is therefore assumed
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that the user of computer in the household takes 20-30 minute breaks for every 2 hours in the
span of his/her usage.
Conservation Measure: Turn off monitor when not using for 20 minutes or above.
Current: 30 kWh per month
After conservation measure: 26 kWh per month
Energy avoided: 4 kWh per month
CO2 avoided: 5.1040 lbs per month (Basis: 1276 lbs per MWh national average) Cost Savings: P 45.24 per month (Basis: P 11.31 - Meralco rate)
Econometrics
Table 5.1: Econometrics
Process IC,
Php
O&M,
Php
AESxPr,
Php/yr
SPP,
yr ROI CRF
CCE,
Php/kWh UPVF PVS NPV B/C Remarks
Airconditioning 750.00 0.00 246.49 3.04 32.87 0.15 5.13 6.71 1653.97 903.97 2.21 ok
Refrigeration 0.00 0.00 530.12 0.00 infinite 0.15 0.00 6.71 3557.15 3557.15 infinite very ok
Lighting 1000.00 0.00 213.76 4.68 21.38 0.15 7.89 6.71 1434.35 434.35 1.43 ok
Data
Processing 0.00 0.00 542.88 0.00 infinite 0.15 0.00 6.71 3642.77 3642.77 infinite very ok
Projection
Figure 5.6: Projected monthly average consumption on or before conservation
To establish baseline, the annual average monthly consumption for the 3 succeeding
years were projected using two period moving average method.
0
50
100
150
200
250
300
350
400
2010 2011 2012 2013 2014 2015 2016 2017
kW
h
Projected Average Monthly Consumption
Baseline
After Conservation
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Section 6 Energy Management Plan
The energy conservation measures were drafted with the consideration that no
changes on the structure of the house will be made. The resulting energy conservation
measures can be implemented immediately. The blinds can be purchased and installed within
a day so as replacing the concerned light bulbs to LED. Cleaning of refrigeration should be
scheduled every 4 months. The energy conservation measure for data processing is a
behavioral change.
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Conclusions and Recommendation
The area of study is a apartment unit with 4 occupants. Their average monthly
consumption is 342.25 kWh per month. The biggest contributor to energy consumption is air-
conditioning. The energy savings per process is presented in the table below:
per month per year
Process
Energy
avoided,
kWh
CO2
avoided,
lbs
Cost
Savings,
Php
Energy
avoided,
kWh
CO2
avoided,
lbs
Cost
Savings,
Php
Airconditioning 1.8162 2.3175 20.54 21.7944 27.8097 246.49
Refrigeration 3.9060 4.9841 44.18 46.8720 59.8087 530.12
Lighting 1.5750 2.0097 17.81 18.9000 24.1164 213.76
Data Processing 4.0000 5.1040 45.24 48.0000 61.2480 542.88
Total 11.2972 14.4152 127.77 135.5664 172.9827 1533.26
All of the energy conservation measures are cost effective.
For future studies, it is recommended to use survey equipment e.g. lux meter,
wattmeter if it is permissible. The predicted model would be more accurate and energy
conservation measures can be easily drafted and energy savings can be easily computed.
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References
Occupational Safety and Health Branch (2010). A Guide to Work with Computers. Labour
Department, Hong Kong.
Randolph, J. and Masters, G. M. (2008). Energy for Sustainability: Technology, Planning,
Policy. USA: Island Press.
Websites:
https://e-services.meralco.com.ph/cmsweb/billing/billslist.jsp
http://energy.gov/energysaver/articles/energy-efficient-computer-use
http://energy.gov/energysaver/articles/tips-kitchen-appliances
http://www.allwallsystem.com/design/RValueTable.html
http://www.horizonservicesinc.com/reference/tips-articles/refrigerator-maintenance-save-
energy
http://www.meralco.com.ph/appcal/formula.html
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Appendix Sample Computations
Heat Transfer through North Wall
Outside temperature = 86 Inside temperature = 75.2
Cost of Conserved Energy for Air-conditioning
d = 8%
n = 10 years
IC = P 750.00
O&M = P 0.00
AES = 21.7944 kWh
Since 5.13 Php/kWh is lesser than current energy price (11.31 Php/kWh), energy
conservation measure is cost effective.