Retrofitting Residences
for Energy Efficiency
A Practical Approach
Georges Khoury
PRGR699B – Project
July 29, 2022
PRGR699B – Project
Retrofitting Residences for Energy Efficiency – A Practical Approach
Retrofitting Residences for Energy Efficiency - A Practical Approach
Table of Contents
1. Introduction
2. Step 1 – Where to Start?
2.1. Essential data
2.2. Optional data
2.3. Inspection-generated data
3. Step 2 – How to Treat the Collected Data?
3.1. Energy consumption baseline
3.1.1. Electricity connection and heating equipment physical inspection
3.1.2. Electrical energy consumed
3.1.3. Thermal energy consumed
3.2. The residence electrical load
3.2.1. Lights
3.2.2. Appliances
3.3. The residence cooling and heating load
3.4. The residence backup power
3.4.1. Generating sets
3.4.2. Uninterruptible power supply
3.4.3. Energy storage systems
3.5. The residence renewable power
4. Step 3 – What Can Be Done to Improve Energy Efficiency?
4.1. Improve the electrical load
4.1.1. Lights
4.1.2. Appliances
4.2. Improve the cooling and heating load
4.3. Improve the backup power
4.3.1. Generating sets
4.3.2. Uninterruptible power supply
4.3.3. Energy storage systems
4.4. Improve the renewable power
4.4.1. Solar photovoltaics
4.4.2. Solar water heating
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Retrofitting Residences for Energy Efficiency – A Practical Approach
4.4.3. Wind microturbine
4.4.4. Biomass heating
4.5. Explore potential renewable power
4.5.1. Solar photovoltaics
4.5.2. Energy storage systems
4.5.3. Solar water heating
4.5.4. Wind microturbine
4.5.5. Biomass heating
5. Conclusion
Appendix – Wind Microturbine Data Sheet
Additional Resources
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Retrofitting Residences for Energy Efficiency – A Practical Approach
1. Introduction
The objective of this paper is to define a set of tools for increasing the energy efficiency of
existing residences.
The methodology is based on academic literature and work experience. The rationale of the
process is to accept what cannot be controlled and to assess what can be, using the criteria of
practicality and economics.
The accompanying Excel workbook provides a convenient way of entering the collected data
and performing calculations toward recommending energy efficiency measures.
2. Step One – Where to Start?
The conventional approach would start by conducting an energy audit of the residence using
software, such as EnergyPlus. The software methodology would map out the residence
envelope material, the orientation, the fenestration, the electric and heating loads, the
occupancy parameters and the ventilation/infiltration data. It will then run a simulation for the
full year using localized weather and irradiation data. The output would be the energy
consumed in kWh when taking into account cooling, heating and renewable energy systems.
This is not the approach this paper follows.
This paper starts by examining the empirical evidence, using 3 sets of data.
2.1. Essential data
• The utility bills, having at least a couple of monthly consumption figures, in peak and
off-peak conditions (usually summer and winter months)
• The utility meter readings, preferably showing energy in and out of the residence
• The fuel meter readings for the same months of the utility bills considered
2.2. Optional data
• Logs of renewable energy history, showing energy produced, used and curtailed
• Logs of backup power (generating set, UPS, Energy Storage System, etc.), showing
power loss / time of use shift events, energy produced, fuel consumed, battery state of
charge (at the beginning and the end of the event) and power quality metrics
2.3. Inspection-generated data
• Inspection of the physical space, covering the building envelope specifications (walls,
roof/ceiling, floor/ground, windows/skylights, doors, infiltration/ventilation), the
orientation/exposure, the shading information (internal, architectural and external), the
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Retrofitting Residences for Energy Efficiency – A Practical Approach
space available for equipment to be recommended (solar panels, variable frequency
drives, heat pumps)
• Inventory of the electrical load components, listing the appliances with their power
rating and energy classification (e.g., EPA Energy Star, EU Energy Label) and the
lighting elements and their type (e.g., LED, CFL, incandescent)
• Inventory / running inspection of the HVAC components, checking the type and rating,
the starting and running current characteristics, the type of fuel used, the pumping
system characteristics and the control devices (analog thermostat, digital thermostat,
built-in thermostat)
• Site dwellers’ habit survey, including space occupancy information, time of low and
high usage of power, cooling and heating comfort temperature settings, level of activity
within each zone of the site.
3. Step Two – How to Treat the Collected Data?
The first task is to establish an energy consumption baseline. Reducing this value will be the
main success criterion for the energy efficiency exercise.
3.1. Energy consumption baseline
The values to be used to establish this baseline are the electrical and fuel monthly energy
consumptions. Considering the residence as a black box where energy from different sources
is the input while essential living conditions and comfort are the output.
Electricity from the Grid
Lighting
Electricity from
Renewable Sources
kWhelectrical
Appliances
Electricity from Back-up
Sources
Electrical HVAC
Equipment
Fuel for Back-up
Sources
Cooling / Heating from
HVAC Equipment
Comfortable Indoor
Temperature, airflow
and Relative Humidity
kWhthermal
Fuel for HVAC
Equipment
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Retrofitting Residences for Energy Efficiency – A Practical Approach
3.1.1. Electricity connection and heating equipment physical inspection
The objective of this inspection is to collect information about the equipment specifications,
rather than to survey any potential maintenance issues.
The utility meter is to be checked for the type, connectivity, current readings and Amp rating.
Downstream from it, the main distribution board is to be inspected; the objective is to verify
there are no discernible faults and to sketch up the distribution schemes inside the residence
(number and Amp rating of circuit breakers, main breaker Amp rating, renewable energy
disconnect breakers and contactors/motorized switching breakers, test and monitor LEDs, etc.
As for the boiler, the type and make are to be noted, along with the rating, the general
condition and the overall pipework status.
3.1.2. Electrical energy consumed
The monthly bill issued by the utility company providing grid electricity to the site lists the
kWh consumption. In certain cases, the invoice goes beyond the energy-in quantification to
include the energy-out from the site; this energy-out has its origin from the excess energy
produced by an on-site power generation source.
The ideal case to have a full picture is to have utility bills covering one full calendar year. If
this is not possible, then 1-2 bills per season (summer and winter) can serve as a basis for an
estimate of the electrical consumption.
If the energy-out kWh reading is available, it cannot be used at face value; it can only be used
in conjunction with the total kWh produced by the renewable or backup power source. As the
objective is to determine the total kWh consumed, the part of renewable / backup energy
consumed by the site needs to be calculated.
The calculations go as follows:
kWhelectrical, total = kWh imported from the grid + kWh generated by alternative source
– kWh exported to the grid
where
Term
kWh imported
from the grid
Definition
consumption billed by the
utility
kWh generated by
alternative source
energy produced by
renewable sources (solar,
wind, etc.) or backup
Notes
minimum requirement: one value
for peak consumption month and
one value for off-peak consumption
month
the values correspond to the months
considered for the grid energy as
per above – these values need to be
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Retrofitting Residences for Energy Efficiency – A Practical Approach
sources (generating set,
energy storage system, etc.)
kWh exported to
the grid
energy credited by the
utility
collected from the
renewable/backup system log or by
reading a meter downstream from
such system
the values correspond to the months
considered for the grid energy as
per above
3.1.3. Thermal energy consumed
This component of energy consumption is only relevant if fuel is used as a primary source for
producing heat. Such fuels include natural gas, diesel, biomass, etc. Cooling via absorption
chillers is not considered, because it is very rare to find it applied to residences.
There are two ways of calculating thermal energy consumption. The direct one is:
kWhthermal, total = kW rating of the boiler x number of hours the boiler is run per month
this result is particularly useful in the case of natural gas since it is usually billed to the
residence per kWh (or the equivalent m3/kWh).
The other, indirect, way is to go by the volume of fuel purchased. The first instinct would be
to go for the boiler fuel consumption figure as specified by the manufacturer; this is only
accurate for brand new equipment. The fuel consumption depends on the age of the boiler and
the regularity of its maintenance. The better option would be to ask the residence tenants for
the fuel supply monthly bill – the volume of the fuel purchased can then be converted into
kWhthermal, total.
3.2. The residence electrical load
To calculate the electrical load, the inventory of lighting and appliances needs to be used,
along with the schedule of the running of said lights and appliances.
3.2.1. Lights
The information collected needs to be tabulated, along with the time of use.
This should resemble something like this:
Item
Lighting
Element
Location
Watt
Rating
Weekdays
Number of
Hours of
Daily
Operation
Number of
Weekdays
in the
Month
Considered
1
LED
Ceiling
Lamp
Living
Room
23
5
23
Weekends
and Holidays
Number of
Hours of
Daily
Operation
7
Number of
Weekends and
Holidays in the
Month
Considered
kWh in the Month
Considered
8
=23x(5x23+7x8)/1000
= 3.93
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3.2.2. Appliances
One would be tempted to use the same methodology used for lighting for other types of
household appliances, including HVAC equipment. This would not be the accurate approach,
especially when motors and compressors are involved. The better way would be to go for the
manufacturer’s kWh calculations (e.g., one washing machine rated at 2000 W would consume
1.5 kWh / wash as per its manufacturer or a fridge rated at 140 W but whose manufacturer
calculates a 358 kWh per year consumption).
The tabulation needs to be modified as follows:
Item
Appliance
Location
Watt
Rating
1
Washing
Machine
Fridge
Bathroom
Kitchen
2
kWh as per
Manufacturer’s
Calculation
Number of Units per
Month
kWh in the Month
Considered
2000
Unit of kWh
used for
Manufacturer’s
Calculation
Wash
1.5
14
=1.5x14=21
140
Year
358
1/12
=358/12 = 29.83
In addition, the phantom loads need to be considered for devices that are always plugged in
and consume standby power. Manufacturers rarely list the standby power rating of appliances;
the following table is derived from empirical measurements:
Appliance
TV
Set-top box
Washing machine
Refrigerator
Mobile phone charger
Split air conditioner
Rice Cooker
Desktop Computer
Electric heating table
Sterilizer
Drinking fountain
Electrical water heater
Induction cooker
Microwave oven
Stereo
Extractor hood
DVD players
Standby Power (W)
Min. Avg. Max.
0.3
4.4
14.0
0.4
4.5
7.4
0.0
1.7
5.4
0.0
3.4
13.0
0.0
0.4
2.9
1.1
6.4
50.0
0.4
13.2
50.5
1.9
3.6
6.6
1.5
2.6
3.7
0.6
1.0
2.4
0.0
2.4
17.0
0.5
1.4
3.0
1.3
2.8
5.6
0.3
0.8
1.4
4.6
10.0
16.7
0.0
1.1
5.1
0.3
4.1
7.8
Standby usage time (hours/day)
Min.
Avg.
Max.
0.0
7.3
24.0
0.0
7.3
24.0
0.0
7.7
24.0
24.0
24.0
24.0
0.0
18.5
24.0
8.0
23.7
24.0
0.0
2.2
24.0
19.0
22.7
24.0
5.0
9.9
13.0
0.0
5.8
24.0
0.0
11.4
24.0
0.0
14.4
24.0
0.0
0.0
0.0
23.8
23.9
24.0
0.0
3.0
12.0
0.0
2.1
21.0
0.0
0.0
0.0
Source: Zhun (Jerry) Yu, Bin Hu, Yongjun Sun, Anbang Li, Jun Li, Guoqiang Zhang, Standby energy use and
saving potentials associated with occupant behavior of Chinese rural homes, Energy and Buildings, Volume 154,
2017, https://doi.org/10.1016/j.enbuild.2017.08.070
3.3. The residence cooling and heating load
The traditional method to calculate the cooling/heating load is to use software, such as
DesignBuilder. This does not conform with the objective of this approach. The most practical
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way to proceed is to assess the installed cooling/heating BTU or kW rating. The electrical
consumption needed to cover the load has already been addressed. What is needed now is to
inspect the cooling/heating load elements that affect the operation of the HVAC equipment,
with an eye on reducing this operation as much as possible.
The sensible and latent parts of the cooling/heating load need to be considered for each
particular zone served by an HVAC piece of equipment. This translates practically, for normal
residences, into individual rooms where HVAC equipment operates.
The sensible part of the cooling/heating load is influenced by the following (already
inspected):
•
Construction specifications of walls, ceilings/roofs and floors/grounds – while this
aspect has a big impact, it is the most difficult to change/improve
•
Windows specifications – this is not limited to the windows themselves, but extends to
the shading measures employed (e.g., curtains, shutters, overhangs, fins). This is easier
to change/improve, but it is costly in most cases
•
Lighting and appliance load – which adds to the sensible heat component, but is
already addressed elsewhere.
The latent part of the cooling/heating load is influenced by the following (already inspected):
•
Ventilation/infiltration – this is fairly simple to change/improve, but it is restricted by
code in many jurisdictions
•
Occupant number and level of activity – this is not a factor that can be changed by
recommendation. It needs to be included as an immutable effect on the cooling/heating
load.
A tabulation of the information collected about the cooling/heating load in one room can go as
follows:
Location
Envelope Information
Bedroom 1
Ceiling / Roof
Dimensions (m)
3x4
Floor / Ground
3x4
Wall 1 Specifications
Wall 2 Specifications
Wall 3 Specifications
Wall 4 Specifications
Window 1 Specifications
3x3
4x3
4x3
3x3
2x2
Window 2 Specifications
Window 3 Specifications
Window 4 Specifications
-
Construction
Concrete, 30 cm thick, plaster, 5 cm rock wool
insulation
Concrete, 30 cm thick, plaster, 1 cm thick parquet, 5 cm
rock wool insulation
CMU, 20 cm thick, plaster, 5 cm air gap, no insulation
CMU, 15 cm thick, plaster, no air gap, no insulation
CMU, 15 cm thick, plaster, no air gap, no insulation
CMU, 15 cm thick, plaster, no air gap, no insulation
Double glazing, 6 mm clear glass, 12 mm air gap
Remarks
Indoor curtains, no shutters, no
overhang, no fins, no obstacles
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HVAC Equipment
Type
Wall Mounted
Split A/C
Make
Model
Cooling
Rating
(kW)
Heating
Rating
(kW)
EER
Rated
Capacity
(BTU/h)
Calculate
d kWh
Carrier
42QHA012VS
3.51
3.5
9.8
10,600
1.08
Ventilation/Infiltration
Estimation
ASHRAE Recommended Air Changes per
(m3/h)
Hour
25
0.5
Occupant Information
Regular Occupancy
Level of Activity
2
Sleeping / Seated, quiet
ASHRAE ACH
Equivalent in m3/h for
Location
=3x4x3x0.5=18
Preferred Thermostat
Summer Setting (ºC)
18
Thermost
at Setting
ºC
(Cooling)
18
Thermost
at Setting
ºC
(Heating)
27
Remarks
Preferred Thermostat
Winter Setting (ºC)
27
Remarks
3.4. The residence backup power
While not present at all residences, backup power is popular in areas with high exposure to
extreme weather events (hurricanes, earthquakes, floods, forest fires) and areas with an
unstable grid. The most common type of backup power is generating sets (either gas or diesel
fired). Where there are critical loads (medical in-house equipment, communication devices),
there could also be an uninterruptible power supply. And, bridging the gap between backup
and renewable power are energy storage systems; these can be used to complement a solar
photovoltaic installation, for instance, they can be used for load management (shifting
consumption in case the utility has a “time of use” tariff in effect) or they can serve as backup as an alternative to generating sets.
3.4.1. Generating sets
The only aspect of operating generating sets to optimize is their fuel consumption. Records of
fuel purchase and control panel logs should provide enough information about historical
operations from the energy produced to the amount of fuel burnt. The generating sets’
electrical connection points need to be inspected for the following:
•
Suitability and condition of the installed cabling and circuit breakers
•
Location of the connection bus and its potential for expansion
•
Location of control cabling and its potential for repurposing/replacement.
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3.4.2. Uninterruptible power supply
As with generating sets, the opportunities for optimization when it comes to UPS are limited
to the electrical energy used to recharge the batteries. This, of course, supposes that the UPS
is fairly efficient (>95% in most modern equipment). The UPS’s electrical connection points
need to be inspected for the following:
•
Suitability and condition of the installed A/C cabling and circuit breakers
•
Suitability and condition of the installed D/C cabling and fuse holders/circuit breakers
•
Condition of the battery bank (battery age, number of discharge/recharge cycles,
voltage at the entry to the inverter) and the interconnecting D/C wiring.
3.4.3. Energy storage systems
The most common type of ESS is grid-connected lithium-ion battery banks. As for UPS, the
only possible improvement in terms of energy efficiency is when the battery recharges. As the
ESS is usually a self-contained system, the only inspection possible is for the battery age and
the number of discharge/recharge cycles. The voltage level at the entry to the inverter is also
important to check for any possible failure in the battery blocks.
3.5. The residence renewable power
There are lots of possible variations of renewable power sources that could be installed at
residences. The most practical ones are:
•
Solar photovoltaics
•
Solar water heating
•
Wind microturbines
•
Biomass heating.
Carrying out an inspection to improve the efficiency of renewable power sources depends on
the source:
•
Solar photovoltaics:
o Positioning inspection: azimuth and tilt of the photovoltaic panels, external
shading or panel inter-row shading, albedo conditions, cleaning regime
o Electrical inspection: A/C and D/C cabling and breaker suitability, inverter
rating, battery bank condition (if present), control cabling suitability
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•
Solar water heating:
o Positioning inspection: azimuth and tilt of the thermal panels, external shading
or panel inter-row shading, albedo conditions, cleaning regime
o Mechanical inspection: water piping condition, water tank and pipe insulation
condition, pump condition (if present)
•
Wind microturbine:
o Positioning inspection: tower height, external obstacles
o Electrical inspection: A/C and D/C cabling and breaker suitability, inverter
rating, battery bank condition (if present), control cabling suitability
•
Biomass heating:
o Boiler inspection: rating, biomass type, maintenance condition
o Mechanical inspection: pipe insulation, radiator blockage, water tank
insulation, heat exchanger condition.
4. Step Three – What Can Be Done to Improve Energy Efficiency?
Now that the site data has been collected and analyzed, it is time to formulate
recommendations to improve energy efficiency.
The general approach will be as follows:
•
Describe the relevant measure
•
Rate the measure on a scale from “Easy” to “Impractical”
•
Rate the measure on a scale from “Cheap” to “Uneconomical”.
4.1. Improve the electrical load
The electrical load in a typical residence is made up of lighting and appliances. The
appliances, in this case, include HVAC equipment, as it is concerned with how to reduce
electric consumption when this equipment is run, as opposed to reducing the reasons for this
equipment is run, which is tackled in the cooling/heating load reduction section.
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4.1.1. Lights
Proposed Measure 1
Implementing the Measure
Practicality
Affordability
Replace all light fixtures
The easier approach would be to gradually
with LED bulbs
replace burnt-out light bulbs with LED ones
Remarks
1- A wholesale replacement of all lighting fixtures with LED lights yields the
best result in lowering lighting energy consumption. It is, however, neither
practical nor affordable.
2- An alternative approach would be to proceed by zone, with the highest
occupancy ones throughout the day being prioritized with the LED
replacement effort.
3- When selecting the LED lighting, it is important to match the lumen value
and light color of the light being replaced, so as not to cause any
inconvenience to the occupants.
4- For any economic evaluation, it is important to take into account the
lifespan of the LED bulbs (up to 25,000 hours) to get to the yearly energy
savings to offset the capital expenditure of the measure.
Proposed Measure 2
Implementing the Measure
Use smart instead of
At the time of replacement, it would be
conventional LED lighting
interesting to consider investing in smart LED
Practicality
Affordability
bulbs
Remarks
1- Going for smart LED gives the occupants control over the intensity of the
light (and its color) and allows for timing / remote switching of the lights.
2- Although it could fit in a wider strategy of making the home “automated”,
smart LED lights are available off the shelf and can function as a discrete
system.
4.1.2. Appliances
Proposed Measure 1
Implementing the Measure
Replace old appliances
The easier approach would be to gradually
with ones having a class A
replace end-of-life appliances with energy-
energy label (EU) or
efficiency labeled ones
Practicality
Affordability
Energy Star (USA)
Remarks
1- A wholesale replacement of all appliances with energy-certified ones yields
the best result in lowering their energy consumption. It is, however, neither
practical nor affordable.
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2- An alternative approach would be to proceed by prioritizing the replacement
of the most energy consumption first such as washing machines and electric
water heaters.
Proposed Measure 2
Implementing the Measure
Practicality
Affordability
Replace air conditioners
The air conditioner inverter or VSD (Variable
with ones using “inverter”
Speed Drive) has a lower energy consumption
technology
than traditional ones.
Remarks
1- There could be an economic argument to warrant the wholesale replacement
of air conditioners with inverter-type ones. It does imply, however, major
installation works and high capital expenditure.
Proposed Measure 3
Implementing the Measure
Use a smart power strip to
The easier way is to group the appliances (e.g.
curb phantom loads
audio-visual equipment, computing equipment,
Practicality
Affordability
etc.) to limit the number of power strips
Remarks
1- Smart power strips come with different configurations and price points. The
simplest ones come with a timer that will make sure it turns off all connected
loads after a certain time; this could be enough in most cases.
4.2. Improve the cooling and heating load
The objective is to reduce the cooling and heating loads while keeping the residence within
the ASHRAE recommended comfort zones (24ºC and 50% relative humidity during summer /
21ºC and 30% relative humidity during winter).
By examining cooling and heating loads as per the below diagrams (from: Strategy guideline:
Accurate heating and cooling load calculations), it becomes apparent that the aspects to
address are:
•
Heat gain/loss through the walls, ceilings/roofs and floors/grounds
•
Solar heat gain/loss through the windows and skylights
•
Infiltration/ventilation heat gain/loss through the building envelope
•
Latent heat gain caused by the occupants and their activities – trying to change this
implies a change of habits of the occupants, which is not something energy efficiency
improvement should prioritize
•
Internal heat gain caused by electrical lighting and appliances – this has already been
addressed in the electrical load improvement section.
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Heat Gain Locations
Heat Loss Locations
No major intervention can be made on the envelope without high expenditure and occupant
inconvenience. The following measures are the most practical:
Measures related to the walls, ceilings/roofs and floors/grounds
Proposed Measure 1
Implementing the Measure
Insulate the walls
The easiest material to work with is rockwool /
internally
recycled fiber in rolls. It is applied to the
Practicality
Affordability
internal surface of the walls and covered with a
gypsum board that can be painted any color.
Remarks
1- The operation is lengthy and messy. It is also recommended the occupants
leave the residence while it is being carried out, because of dust and fumes
2- A relatively thin insulation layer (6 – 8 cm) and a 1.5 cm thick gypsum
board will increase the wall R-value by 0.38 m2.K/W
Proposed Measure 2
Implementing the Measure
Insulate the ceiling if there
The easiest material to work with is rockwool /
is an attic
recycled fiber in rolls. It is applied to the upper
Practicality
Affordability
surface of the ceilings and is covered with
plywood.
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Remarks
1- The operation is lengthy and messy. It is also recommended the occupants
leave the residence while it is being carried out, because of dust and fumes
2- A relatively thin insulation layer (6 – 8 cm) and a 2 cm thick plywood board
will increase the ceiling R-value by 0.38 m2.K/W
3- Alternative insulation material includes polyurethane or polystyrene and
tiling.
Proposed Measure 3
Implementing the Measure
Insulate the roof if
The easiest material to work with is
applicable
polyurethane / polystyrene in boards. It is
Practicality
Affordability
applied to the exterior of the roof and tiled
over.
Remarks
1- The operation is lengthy and messy. As the work is done outside the
residence, it is safe for the occupants to stay.
2- A relatively thin insulation layer (6 – 8 cm) and a 2 cm thick tile will
increase the roof R-value by 0.45 m2.K/W.
Proposed Measure 4
Implementing the Measure
Insulate the floor
The easiest material to work with is
internally
polyurethane / polystyrene in boards. It is
Practicality
Affordability
applied to the exterior of the roof and is
covered with tile or wood flooring.
Remarks
1- The operation is lengthy and messy. It is also recommended the occupants
leave the residence while it is being carried out, because of dust and fumes
2- A relatively thin insulation layer (6 – 8 cm) and a 2 cm thick tile or 1 cm
thick wood flooring will increase the floor R-value by 0.45 m2.K/W.
Measures related to the windows and skylights
Proposed Measure 1
Implementing the Measure
Replace
This measure is only applicable if the current
windows/skylights with
windows/skylights are single-glazed. It
triple or double-glazed
involves dismounting the existing
types
window/skylight panes and replacing them
Practicality
Affordability
with higher-efficiency ones.
Remarks
1- The operation is very expensive. It should not take a long time to complete,
as most of the work is done off-site and the actual on-site work consists of
replacing window/skylight panes.
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2- The measure can be done while the occupants are on site. They would have
to put up with dust and construction noise.
Proposed Measure 2
Implementing the Measure
Use blackout curtains on
This measure consists of installing new /
windows/skylights
replacing existing curtains hanging in front of
Practicality
Affordability
windows/rolling under skylights.
Remarks
1- The operation is moderately expensive, depending on the material and brand
of the curtains chosen. It should not take a long time to complete, as most of
the work is done off-site and the actual on-site work consists of taking out the
old curtains and installing the new ones
2- There might be an issue with the amount of light the curtains would block.
To get the best results, the curtains needs always to be drawn, which might
force a lengthier use of indoor lighting.
Measures related to Infiltration/ventilation
Proposed Measure 1
Implementing the Measure
Seal any air leak around
This measure consists of sealing any air leak in
the residence outer
the horizontal and vertical joints of walls,
perimeter
ceilings/roofs, floors/grounds, in the openings
Practicality
Affordability
around windows/skylights and doors and
in/around any exhaust ducting (kitchen hob,
fireplace).
Remarks
1- It is imperative to conduct an air leak test for the entire residence before
deciding the economic feasibility and extent of this measure. Air leak tests
need to be carried out by professionals and might be expensive, depending on
the size of the residence
2- The choice of material to use depends on the size of the air leak and its
location/nature. It can range from caulk to foaming agents, with different price
points and the extent of labor involved.
Proposed Measure 2
Implementing the Measure
Controlling the relative
This consists in controlling the extent of time
humidity brought on by
the ventilation system is run and by using
ventilation
smart dehumidifiers to be placed in each zone
Practicality
Affordability
of the residence.
Remarks
1- This measure becomes necessary in the event air tightness of the residence
is achieved. For the comfort of the occupants, a certain number of air changes
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per hour needs to happen (this is governed by local building standards).
Mechanical ventilation might need to be implemented, with the negative
impact of higher relative humidity, depending on the outside air conditions.
2- A thermostat with humidity sensors can control the running time of the
mechanical ventilation. It can also turn on and off any local smart
dehumidifiers, which could provide comfortable conditions, without the need
to run energy-intensive air conditioning.
4.3. Improve the backup power
As previously discussed, backup power is called upon when the main sources of steady power
falter; this is slightly nuanced when it comes to energy storage systems, as they can be used to
complement the renewable power sources and/or to shift electricity consumption to a time of
day where the utility tariffs are more advantageous (usually evenings on weekdays and
weekends). Improvement is, however, restricted to proper maintenance and, more
importantly, to a reduction in fuel consumption (generating sets) or utility electricity (UPS
and ESS).
4.3.1. Generating sets
To make generating sets more energy efficient, it is important to limit their running time and
to reduce the consumption of fuel (diesel or natural gas usually) when they do have to run.
Proposed Measure 1
Implementing the Measure
Limit the runtime of
By design, the generating sets turn on when
generating sets (if there is
there is a loss of utility power. Connecting
renewable power present)
them in sync with the renewable power
Practicality
Affordability
inverters would stop them from running when
there is enough renewable power to sustain the
load.
Remarks
1- In practice, an external control board (such as the DEIF ASC-4 https://www.deif.com/products/asc-4-solar/) needs to be installed and
connected by control wiring to the renewable inverter and the generating set
2- While the capital expenditure for the equipment/material is not large, the
installation work might prove to be difficult and expensive, depending on the
site conditions.
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Proposed Measure 2
Implementing the Measure
Conduct maintenance on
The generating set needs to be serviced
the generating set
regularly (every 6 months or 250 hours of
Practicality
Affordability
operation, whichever occurs first). This
includes oil and filter changes. In addition, it is
recommended to clean the carbon deposits and
ensure the water / coolant are at the right
temperature and mixture level
Remarks
1- This is a regular exercise. Having the right service agreement in place will
reduce breakdowns and improve the performance of the generating set.
Proposed Measure 3
Implementing the Measure
Reduce the load connected
Running through the load connected to the
to the generating set
generating set might lead to some of it being
Practicality
Affordability
disconnected. With a reduced load, the
generating set will operate more efficiently.
Remarks
1- This is an exercise in identifying which loads are critical to warrant being
backed up. If loads are not deemed sensitive enough, they can be excluded
from the generating set distribution panel.
4.3.2. Uninterruptible power supply
The only measure of energy efficiency to be conducted with UPS (besides the replacement of
the UPS equipment with more efficient hardware) is to reduce the electricity used to recharge
the batteries.
Proposed Measure 1
Implementing the Measure
Practicality
Affordability
Charge the batteries only
Battery charging cables need to be connected
from renewable power (if
to the renewable power inverter distribution
present)
board.
Remarks
1- There is no major capital expenditure involved. The cable rerouting work
might, however, prove to be difficult and expensive, depending on the site
conditions.
Proposed Measure 2
Implementing the Measure
Charge the batteries from
Battery charging is to be permitted only when
the utility only during off-
the off-peak utility tariff is in force.
Practicality
Affordability
peak tariff
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Remarks
1- The way to make sure the batteries are only charged during a certain time
interval is the replace the circuit breaker feeding the charger with a smart
circuit breaker, which can be programmed to close during the specified
window.
4.3.3. Energy storage systems
To make the ESS more energy efficient, the same logic applied to the UPS needs to be
followed: reduce the electricity used to recharge the batteries.
Proposed Measure 1
Implementing the Measure
Practicality
Affordability
Charge the batteries only
Battery charging cables need to be connected
from renewable power (if
to the renewable power inverter distribution
present)
board.
Remarks
1- There is no major capital expenditure involved. The cable rerouting work
might, however, prove to be difficult and expensive, depending on the site
conditions.
Proposed Measure 2
Implementing the Measure
Charge the batteries from
Battery charging is to be permitted only when
the utility only during off-
the off-peak utility tariff is in force.
Practicality
Affordability
peak tariff
Remarks
1- The way to make sure the batteries are only charged during a certain time
interval is the replace the circuit breaker feeding the charger with a smart
circuit breaker, which can be programmed to close during the specified
window.
4.4. Improve the renewable power
For solar photovoltaics / water heating and wind microturbines, the goal is to maximize the
capture of the energy source (solar radiation and wind). As for biomass, the higher the
calorific value of the fuel, the better the output is.
4.4.1. Solar photovoltaics
4.4.2. Solar water heating
The yield of any solar system (photovoltaic or thermal) is affected by the positioning of the
solar panels and the shading they are subject to.
When checking the mounting of the solar panels, two figures need to be inspected:
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•
The solar panel elevation angle (vertical tilt). The optimal value for year-round yield is
for the elevation angle to be set at the site latitude (e.g., for Beirut this would be
33.88º)
•
The solar panel azimuth angle (horizontal orientation in relation to the equator). The
optimal value is 180º for Northern Hemisphere sites and 0º for Southern Hemisphere
ones.
Shading on solar panels originates from two sources:
•
External obstacles: nearby terrain higher than the site, trees, antennas or poles
•
Self-shading from other photovoltaic panel rows.
Proposed Measure 1
Implementing the Measure
Change the elevation and
If the panel existing angles depart significantly
azimuth angles of the
from the optimal values, then they need to be
solar photovoltaic panels
shifted towards the optimal by modifying the
Practicality
Affordability
location and height of their supporting metallic
structure.
Remarks
1- This is a very delicate operation: the panels need to be dismounted first
without damaging them; the metallic structure needs then to be relocated to the
new azimuth direction, which implies its legs being dislodged and then affixed
to the horizontal surface (roof, ground) again. As for the elevation, if the
vertical part of the structure is welded, it needs to be replaced to accommodate
the new position
2- This measure is only to be carried out by professionals, which means
incurring moderate to high labor costs.
Proposed Measure 2
Implementing the Measure
Remove external obstacles
The only external obstacles that can be
Practicality
Affordability
controlled are ones on the site: trees that can be
trimmed, antennas/poles that can be moved,
etc.
Remarks
1- If measure 1 needs to be taken, then the external obstacles to be cleared are
the ones affecting the panels in their new position.
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Proposed Measure 3
Implementing the Measure
Eliminate inter-row
If the solar panels are installed in more than
shading
one row, then the higher rows might cast a
Practicality
Affordability
shade on the ones below them. The solution is
to increase the space between the metallic
structures holding each row of panels.
Remarks
1- The minimum inter-row distance between rows can be determined
empirically by observing the shades at different times of a solar day.
Alternatively, there are online calculators to facilitate the task (e.g.,
https://www.renvu.com/Inter-row-Spacing-Calculator)
2- The ease of this operation depends on the construction of the existing
metallic structures. If the two structures are welded, then the horizontal beams
holding the two structures together need to be replaced.
3- In any case, all panels must be dismounted with care before attempting any
work on this measure. This is only to be carried out by professionals, which
means incurring moderate to high labor costs.
Proposed Measure 4
Implementing the Measure
Cleaning the solar panels
The solar panels need to be cleaned regularly
Practicality
Affordability
to improve their yield.
Remarks
1- The cleaning frequency depends on the local climate. The dustier it gets, the
more frequent cleaning must be carried out. This can range from once per
season to once per day, depending on the site conditions
2- The best results are achieved by using distilled water. Depending on the
dirtiness, a soft sponge and a mild detergent might be needed.
Proposed Measure 5
Implementing the Measure
Practicality
Affordability
For solar water heating
The water system needs to be descaled, the
systems, check the water
tank and pipe insulation checked for wear and
tank, pump and piping
tear and the pump inspected for a proper run.
Remarks
1- This should be carried out at least once a year, before the winter season
2- There could be an expenditure element if the pump and tank need to be
replaced, as opposed to the pump shaft being repaired or the leaking water tank
being welded.
4.4.3. Wind microturbine
Improving the energy yield of a wind microturbine is limited to clearing any obstruction and
to placing it at the appropriate height.
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The minimum clearance required for the microturbine to function properly is 8 to 11 m above
all surrounding obstructions that are within a 90 m radius from the microturbine position.
As for elevation, the best results are achieved when the microturbine is placed between 1.51
and 1.79 times above the original height of the building at its front face.
Proposed Measure 1
Implementing the Measure
Remove external obstacles
The only external obstacles that can be
Practicality
Affordability
controlled are ones on the site: trees that can be
trimmed, antennas/poles that can be moved,
etc.
Remarks
1- If the obstacle cannot be moved then, alternatively, the microturbine tower
can be relocated to have a clearer horizon. This is an expensive affair that
requires dismounting the microturbine and relocating the tower structure. It is
also a job for professionals, so labor costs need to be considered.
Proposed Measure 2
Implementing the Measure
Install the microturbine at
If the height of the existing tower is
a higher level
significantly below the recommended value,
Practicality
Affordability
then a new higher tower must be installed.
Remarks
1- This is a drastic measure and should only be taken when the original height
prevents the microturbine from yielding energy well below the design yield as
determined by consulting the global wind atlas (https://globalwindatlas.info/).
4.4.4. Biomass heating
The efficiency is bettered by using biomass with the highest possible calorific value. The
following is a list of energy density values by volume for different biomass fuels:
Fuel
kWh/m3
Wood chips (30% moisture content)
870
Logwood (stacked – air dry: 20% moisture content)
1,400 – 2,000
Wood (solid – oven dry)
2,100 – 3,200
Wood pellets (10% moisture content)
3,100
Miscanthus (bale – 25% moisture content)
500 – 650
Source: https://www.forestresearch.gov.uk
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In addition, the boiler system efficiency can be improved by:
Proposed Measure 1
Implementing the Measure
Perform maintenance on
As 1 millimeter of scale build-up can increase
the boiler
fuel consumption by 2%, it is important to
Practicality
Affordability
clean the boiler.
Remarks
1- Preventive maintenance includes the cleaning of airways, cleaning the heat
exchanger and combustion chamber, testing of safety equipment and flue gas
analysis to check combustion efficiency
Proposed Measure 2
Implementing the Measure
Perform maintenance on
This concerns the hot and cold water piping,
the rest of the system
the piping insulation, the pump, the heating
Practicality
Affordability
elements and the domestic hot water tank.
Remarks
1- This kind of preventive maintenance starts with a visual inspection: leaks
(from the pipes, the pump, the heating elements and the water tank) and wear
and tear of the insulation. Descaling the piping can also be carried out easily.
2- If leaks are detected, then it becomes a plumbing job and could imply
medium to high labor costs, depending on the extent of the damage.
4.5. Explore potential renewable power
The objective is to determine the site appropriateness and readiness for renewable power.
Once this is proven, then proper design and installation work needs to be carried out. This is
beyond the scope of this document, but the additional resources listed give a good indication
of the process needed to acquire renewable power.
4.5.1. Solar photovoltaics
The first task is to ascertain the existence of enough space to install solar panels. This
calculation starts by determining the electrical load that needs to be covered by the solar
photovoltaic system. The kW required is then divided by the kW peak value of a generic solar
photovoltaic panel (in this case, it is the Longi Hi-MO5 module, with a 550 kWp rating and
dimensions of 2.26 m x 1.13 m). 10% additional space needs to be taken into consideration
for maintenance and access. As an example, for a 3 kW load:
Area for solar panels = Load W / module Wp x module area x 1.1
= 3000 / 550 x 2.26 x 1.13 x 1.1
= 15.32 m2
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If this space is available, then the next task is to determine the average energy yield per month
of the site location.
The College Hall at the American University of Beirut has the following coordinates:
Latitude: 33.900745
Longitude: 35.482203
Assuming the same 3 kW load is located at the College Hall, then the system would consist of
6 panels with a rating of 3300 Wp. To determine the yield, a free online resource developed
by the European Union can be used.
Entering the site coordinates, the kWp rating and an estimate of losses (14% is an industry
convention), the EU Photovoltaic Geographical Information System can then be accessed via
the following link:
https://re.jrc.ec.europa.eu/api/v5_2/PVcalc?lat=33.900745&lon=35.482203&peakpow
er=3&loss=14&optimalangles=1&outputformat=json&browser=1
The resulting json file has the following values:
Month
Average daily energy
Average monthly energy
production (kWh)
production (kWh)
January
9.36
290.12
February
11.31
316.76
March
13.96
432.76
April
15.68
470.51
May
16.91
524.28
June
17.79
533.82
July
17.74
550.08
August
17.33
537.14
September
16.54
496.22
October
14.26
442.16
November
11.82
354.58
December
9.48
293.78
If these values are deemed acceptable, then the next step would be to proceed with the proper
design and execution of the solar photovoltaic system.
To help with that, a site survey needs to be conducted:
•
accessibility of the solar panel space for future maintenance
•
shading from outside sources
•
cable routing
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•
electronic equipment location
•
connection to the residence electric panel
•
in case batteries are part of the system, a well-ventilated indoor or shaded outdoor
space needs to be found.
4.5.2. Energy storage systems
Energy storage systems (ESS) sit at the intersection of backup and renewable power.
An energy storage system, most likely consisting of a lithium-ion battery bank, can run in
conjunction with a solar photovoltaic installation or as a stand-alone system.
In either case, the system size depends on the autonomy it provides, as expressed in kWh of
energy. The battery depth of discharge needs also to be taken into consideration (it rarely
should exceed 80%). As most systems can operate in parallel, adding to the system’s
autonomy is accomplished by adding a new battery bank (preferably of the same rating).
The most appropriate configuration is the “hybrid” one, which can be connected to a solar
photovoltaic panel array (and replace the existing inverter, if applicable) or that can supply
A/C power to the load (in a similar topology to a standby UPS).
The space required for an ESS is not large and there are outdoor type ones, making their
installation more flexible. It is best to keep the ESS at 25ºC and away from a direct source of
heat, to ensure optimum efficiency.
4.5.3. Solar water heating
A more empirical approach is used to determine the area required for solar water heating
panels. All tables and figures come from the solar domestic water heating handbook (cited in
the additional resources section).
To use the same example of the College Hall location, and assuming the need to heat 200
liters of water per day and a temperature differential of 45ºC, the daily energy required would
be:
Q = ρ x V̇ x Cp x (THot – TCold)
where ρ is the water density
and Cp is the water specific heat capacity
Q = 1 x 200 x 4.18 x 45 = 37620 kJ = 10.45 kWh
The yearly required energy is then:
Q = 365 x 10.45 = 3814 kWh
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The reference classifies Lebanon as a tropical / sunbelt country.
This puts a limit of 70% on the energy to be derived from the sun (known as the solar
fraction). The remaining 30% of the energy needed has to come from electrical sources.
The energy from the solar system is then 0.7 x 3814 = 2670 kWh.
The reference gives Lebanon irradiation for a collector at 30% tilt and facing South equal to:
1,800 kWh/m2 x 97% = 1,746 kWh/m2
For a collector efficiency of 35%, the usable irradiation is then:
1,746 kWh/m2 x 35% = 611 kWh/m2
The collector area can then be calculated as follows:
Collector area = 2670 / 611 = 4.37 m2
If this area is available, then the next step is to make sure it is practical to install the solar
water heating system:
•
accessibility of solar panel space for future maintenance
•
shading from outside sources
•
connection to the residence water supply
•
water tank location
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•
place for pumps (if needed) and pipe routing
•
control panels and cable routing.
If all the conditions are favorable, a solar water heating system should not be complicated to
install.
4.5.4. Wind microturbine
To determine the suitability of installing a wind microturbine, the site mean wind speed needs
to be investigated.
Another free web resource, the Global Wind Atlas (https://globalwindatlas.info/) can be used
to get the wind mean speed for a specific location.
This can be used with a typical microturbine performance curve to estimate the yearly energy
yield for the site.
Taking again the College Hall, the website returns the following mean wind speed at 10 m
height:
From the chart, the wind mind speed at 50% is 3.19 m/s.
The yearly energy yield is then calculated by interpolation in the yield table included in the
microturbine datasheet (3 kW microturbine by Ryse Energy, included in the Appendix). It is
1525 kWh.
If this value is deemed acceptable, then the next step would be to check for the space to erect
the tower for mounting the microturbine. The height of this structure, along with the
combined weight of the microturbine and the metal / concrete, need to undergo a structural
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analysis to take into account the various forces affecting the structural integrity and,
ultimately, the operation of the microturbine.
Only then can one proceed to make the proper design and execution of the wind power
system.
To facilitate this, the following needs to be inspected:
•
accessibility of the microturbine space for future maintenance
•
obstructions from outside sources
•
electronic equipment location
•
cable routing
•
connection to the residence electric panel.
4.5.5. Biomass heating
Installing biomass heating can be a relatively simple (but not cheap) procedure or it can be
complicated and expensive. This depends on the existence or not of a fossil fuel burning
boiler (natural gas or diesel fired).
If it is a matter of replacing an existing boiler, then the job is to dismantle the old boiler,
install the biomass boiler and connect it to the pipe/pump system and the exhaust system.
New controls are to be installed. The only constraint caused by the new system is that a
storage room for the biomass fuel is needed, with a way to be filled from outside the
residence.
If no heating system exists, then the first step is to calculate the residence heating load.
Specialized software exists but is often expensive. A free online resource, the Hunt Heating
Heat Load Calculator (https://www.huntheat.com.au/support/heat-load-calculator/) can be
used for the planning and budgeting phase.
Once the heating load is calculated, the boiler can be selected. The rest of the plant needs to
be designed as well: heating elements in each room (radiator, underfloor heating), hot water
tank for domestic hot water, pump, piping connections, controls, exhaust flues, etc.
The space constraint is compounded as well: enough room for the boiler, the pumps and fuel
storage need to be available (usually 10 m2 is the minimum area needed).
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Other elements to consider are:
•
accessibility of the boiler room for future maintenance
•
way to unload the biomass fuel safely and quickly (large diameter pipe from the truck
position to the storage room, ramp to roll fuel unto when it is unloaded from the
truck).
5. Conclusion
Two important issues need to be considered when performing any energy efficiency
improvement measure:
•
the economic feasibility of the endeavor
•
and the decision to install an overarching building management system or not.
Economic feasibility
The easiest method to determine the economic feasibility of any energy efficiency measure is
to calculate its Net Present Value (NPV).
The inputs for this calculation are:
•
Investment amount: capital expenditure required to implement the measure (including
equipment, material and labor); any tax incentives, grants or subsidies need to be taken
into account
•
Measure duration (t): time in years where the original measure can still yield positive
effects (e.g., solar PV panels have a useful life of 25 years, which means any measure
involving these panels has a 25-year duration)
•
Yearly savings: difference between the baseline scenario and the improved scenario,
in terms of money per year (e.g., if the initial yearly energy bill is USD 1200 and the
bill becomes USD 900 after implementing the measure, then the savings are USD 300
per year)
•
Discount rate (i): interest rate applicable if the investment amount is to be borrowed;
in the case of a residential type of loan, it is most practical to use the interest rate a
bank can offer (minus any subsidies).
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The NPV is then calculated using the formula:
𝑛
𝑁𝑃𝑉 = ∑
𝑡=1
𝑌𝑒𝑎𝑟𝑙𝑦 𝑆𝑎𝑣𝑖𝑛𝑔𝑠 𝑎𝑡 𝑦𝑒𝑎𝑟 𝑡
(1 + 𝑖)𝑡
The accompanying Excel file calculates the NPV automatically when all values are entered.
Any positive NPV indicates that the measure is economically feasible.
Building management system
The discussion has so far been about discrete measures, with the effect of each being
evaluated locally to where the measure is applied. An alternative would be is to group the
impact of all measures in one centralized location, where the residence occupants can see the
improvements in real-time. The information would be collected via sensors and meters and
fed into an algorithm that will enhance monitoring by sending alarms, alerts and notifications
and by stopping any harmful event automatically.
An example of such a system would be the Johnson Controls OpenBlue building management
system:
While the benefit of a building management system is mostly about the convenience of the
occupants, integrating all measures might lead to synergistic savings. In this case, the NPV of
such a system can be calculated to justify its purchase.
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Appendix – Wind Microturbine Data Sheet
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Additional Resources
•
Office of Energy Efficiency & Renewable Energy, US Department of Energy
https://www.energy.gov/eere/energy-efficiency
•
Energy Star (USA)
https://www.energystar.gov/
•
European Product Registry for Energy Labelling
https://eprel.ec.europa.eu
•
The Energy Saving Trust (UK)
https://energysavingtrust.org.uk/
•
National Renewable Energy Lab (USA)
https://www.nrel.gov/
•
ASHRAE Consumer Center
https://www.ashrae.org/technical-resources/free-resources/consumer-center
•
Burdick, A., Strategy guideline: Accurate heating and cooling load calculations
(2011). Washington, D.C.; U.S. Dept. of Energy, Energy Efficiency & Renewable
Energy, Building Technologies Program
•
TIWARI, G. N., SHYAM, & TIWARI, A. (2016). Handbook of Solar Energy:
Theory, analysis and applications. Springer.
•
Qiang Wang, Jianwen Wang, Yali Hou, Renyu Yuan, Kun Luo, Jianren Fan,
Micrositing of roof mounting wind turbine in urban environment: CFD simulations
and lidar measurements, Renewable Energy, Volume 115, 2018
•
Laughton, C. (2010). Solar domestic water heating: The Earthscan expert handbook
for planning, design, and installation. Washington, DC: Earthscan.
34