Design and Operation of a Conditioning
Energy Recovery Ventilator (CERV) for
Passive Houses
Ben Newell and Ty Newell
January 22, 2009
Newell Instruments Inc.
1103 N High Cross Rd
Urbana, IL 61802
Phone: 217-344-4526
www.newellinstruments.com
Motivation and Objectives
Combine our knowledge of HVAC systems with interest in
energy efficient homes to create a niche product.
Coupled with highly efficient house construction (e.g.,
Passive House standards), efficient house conditioning
systems lead to the ability to provide all home energy
needs with solar energy in a cost effective manner.
The “CERV” is a primary component for efficient heating,
cooling, and dehumidification of an energy efficient home.
Development of energy efficient house conditioning
systems with the goal of constructing a “net zero energy”
home for central Illinois and beyond.
Air Conditioning Experience
automotive
refrigerators
military aircraft cooling
Presentation Outline
• House Energy Characteristics
• Building Conditioning Requirements
• Conditioning Energy Recovery Ventilator
Description
• CERV Operation and Performance
Keeping Comfortable
1500.0
Wall/Roof
Insulation
Windows (heat)
Thermal Energy (kW-hr)
1000.0
Windows (Solar)
Air Ventilation
500.0
Refrigerator
Freezer
0.0
Heat Pump
Water Heater
People (heat)
-500.0
Other heat
Lots to consider!
-1000.0
-1500.0
0
2
4
6
8
10
12
Month (Jan = 1)
Building construction, outside conditions,
Interior components, and activities
Net Thermal
Load
Windows Gain
(Total)
Total latent loads
14
Sensible Loads
2007 Solar Decathlon House
o The 2007 University of Illinois Solar
Decathlon “elementhouse” is a “Net
Zero” house in which all house
energy is supplied by solar energy
(solar electric with PV panels)
o The UI 2007 Solar Decathlon House
is also designed to supply up to
10,000 miles of electric vehicle
transportation per year
•Zero energy house design significantly reduces the capacity
requirements of its comfort conditioning system
•Ventilation and moisture management become very important
•While smaller, the comfort system must be more nimble and smarter
than conventional systems
2000sq ft Home LifeCycleCost
Simple LifeCycleCost ~ $242,000
with 12 cm insulation = $20,500
and 27 m2 PV = $20,200
Or,
10cm insulation = $17,100
and 29.5 m2 PV = $22,100
Or,
5 cm insulation = $8,500
and 45 m2 PV = $33,800
Optimal solution is fairly “flat”
Sensible and Latent Heat
“Sensible” heat and “latent” heat refer to the transfer of energy into or
out of a conditioned space where:
•Sensible refers to an energy transfer that you can “sense”
•Temperature change of air
•Latent refers to an energy transfer that is hidden or not sensed
•Moisture change of air
60%rh
40%rh
The energy needed to drop 70F air from 60%rh to 40%rh
is the same as the energy to heat air from 70F to 85F
70F
85F
Conventional vs. Efficient
• Conventional homes are dominated by the exterior conditions
– Leaky envelope means unwanted ventilation
– Larger capacity required because of free air movement
– Free exchange of conditioned/unconditioned air without
recovery of energy
– Little moisture control
• Efficient homes balanced more towards interior loads
– Ventilation and moisture are controlled
– Small energy loads make energy recovery significant
Typical House Conditioning System
Illinois Weather
• Conventional home air conditioner ~3 “tons” (36,000
Btu/hr ~ 10,000 watts)
– Designed for ~2/3 sensible and ~1/3 latent loads
• Conventional gas furnace ~80,000 Btu/hr ~ 22,000 watts
• Efficient capacity control of conventional systems difficult
– Conventional construction requires large span of
capacity control
Base Case House
So, what capacity is needed to keep a high efficiency
residence comfortable?
How many tons, BTUH, watts, liters per day…..?
• 2000 sq ft, single story house (~45’ x 45’)
• 50 sq ft, south facing windows,
U=0.5W/m2-K
– High performance, triple/quadruple
glazed
• UAwall + UAroof = 65W/K (~R22 wall,
R44 roof)
• Ventilation = 50 cfm (0.2 ACH) =>
ASHRAE 62.2 standard
• 4 people (75W/person heat; 75W/person
moisture)
• 200W internal generation (refrigerator,
ICF (insulated concrete form)
TV, computer, lights, etc)
home in Urbana IL
1200
2000sq ft Home Daily Capacities
cooling and
dehumidification
1000
Dec
Jan
800
Qlatent (watts)
Nov
Feb
Mar
600
Apr
400
heating and
dehumidification
May
June
200
July
0
Aug
-200
-400
-4000
cooling and
humidification
heating and
humidification
-3000
-2000
-1000
Qsensible (watts)
0
1000
Sept
Oct
2000
2000sq ft Home Comfort
1200
1000
Nov
cooling and
dehumidification
Comfort is a
squishy concept
Dec
Jan
800
Feb
Qlatent (watts)
66-76F
Mar
600
Apr
heating and
dehumidification
400
May
June
200
July
0
30-60%rh
Aug
-200
-400
-4000
cooling and
humidification
heating and
humidification
-3000
-2000
-1000
Qsensible (watts)
0
1000
Sept
Oct
2000
2000sq ft “Conventional” Home
Nov
3000
cooling and
dehumidification
2500
2000
Qlatent (watts)
1500
1000
Dec
3 x vent, 3 x UA
100 sqft windows
Jan
Feb
heating and
dehumidification
Mar
500
Apr
0
May
heating and
-500
humidification
cooling and
humidification
-1000
June
July
-1500
-10000
-8000
-6000
-4000
-2000
0
Qsensible (watts)
2000
4000
6000
Aug
Sept
CERV
Conditioning Energy Recovery Ventilator
Low temperature heat pump air conditioning system:
Cold side air
evaporator
Hot side air
compressor
condenser
CERV Features
• Small capacity, self-contained, modular
system
• Plug and play modules are added to reach
required building capacity
• Air source heat pump with a variable
speed compressor to adjust to load
• Provides heating, cooling,
dehumidification, and ventilation
Refrigerant Overview
Refrigerant
Systems
*ODP (Ozone
Depletion
Potential)
*GWP (Global
Warming
Potential)
1
8100
R12
automotive
R22
residential and light commercial air
conditioning, refrigerators, and
freezers
0.05
1700
R134a
residential and light commercial air
conditioning, refrigerators, freezers,
and automotive
0
1300
R410A
residential and light commercial air
conditioning replacing R22
0
1890
R744 (CO2)
In development for automotive
0
1
HFO 1234 yf
Preliminary tests as a 134a “drop in”
0
4
•ODP – Ozone depletion potential compared to CFC-11 (1)
•GWP – contribution to global warming compared to same mass of CO2 (1)
Refrigerant and Regulations
• R12 banned in 1994 – replaced with R134a
• Montreal Protocol – international treaty to phase
out ozone depleting substances – eliminates
sale of R22 equipment starting in 2010,
allocation of acceptable producers for service
use of existing equipment
• European Union 2007 MAC (Mobile Air
Conditioning) Directive: bans refrigerants with
GWP > 150 from new vehicles in 2011 and all
vehicles in 2017 – displacement of R134a
CERV Refrigeration System
• Use 134a phase into 1234 yf as it
becomes available
– no ozone depletion
– very low global warming potential
• Hermetically sealed system
– small refrigerant charge
– eliminates onsite charging, line sets, fittings
– sealed for lifetime of unit
– refrigerant can be recovered
CERV Modes of Operation and
Test Results
•
•
•
•
•
heating
cooling
heating with ventilation
cooling with ventilation
ventilation only
integrated controls to determine most efficient conditioning
mode
Heating without ventilation:
T hot out = 32.2 C
RH% out = 27.5%
T cold in = 5.2 C
RH% in = 84.6%
outside
T hot in = 18.1 C
RH% in = 64.5%
T cold out = -1.2 C
RH% out = 90.7%
compressor power = 377 W
COP = 3.1
inside
CERV
total heating capacity = 1165 W
EER = 11.1 Btu/W-hr
Energy Efficiency Ratio
1400
Winter day just below freezing, air flow ~100cfm
Compressor Power and Heat (Watts)
1200
1000
800
Compressor (W)
600
Home Heat (W)
400
200
Defrost periods
0
0
2000
4000
6000
8000
10000
Time (seconds)
12000
14000
16000
18000
50
40
Temperature ( C)
30
20
10
0
-10
-20
Toutside_in ( C)
Toutside_out ( C)
Tinside_in ( C)
Tinside_out ( C)
-30
0
2000
4000
6000
8000
10000
Time (seconds)
12000
14000
16000
18000
Coefficient of Performance (heat mode)
5.00
4.00
3.00
2.00
COP heating
1.00
0.00
0
2000
4000
6000
8000
Time (seconds)
10000
12000
14000
16000
18000
800.0
Very cold day ~2°F, long operation, no defrost needed
Compressor Power and Heat (Watts)
700.0
600.0
500.0
Compressor (W)
400.0
Home Heat (W)
300.0
200.0
“drop in” mode lowers comp power
100.0
0.0
0.0
1000.0
2000.0
3000.0
4000.0
Time (seconds)
5000.0
6000.0
7000.0
30.0
20.0
Temperature (C)
10.0
Toutside_in ( C)
Toutside_out ( C)
0.0
Tinside_in ( C)
Tinside_out ( C)
-10.0
-20.0
Operation at 0°F, also performed at -17°F with reduced capacity data not shown
-30.0
0.0
1000.0
2000.0
3000.0
4000.0
Time (seconds)
5000.0
6000.0
7000.0
Coefficient of Performance (heat mode)
3
2.5
2
COP heating
1.5
1
0.5
0
0.0
1000.0
2000.0
3000.0
Time (seconds)
4000.0
5000.0
6000.0
7000.0
Cooling without ventilation:
T cold out = 22.6 C
RH% out = 64.0%
T hot in = 37.7 C
RH% in = 29.0%
outside
T cold in = 31.5 C
RH% in = 39.0%
T hot out = 55.4 C
RH% out = 12.7%
compressor power = 450 W
COP = 2.4
inside
CERV
total cooling capacity = 1079 W
EER = 8.6 Btu/W-hr
lat. = 133 W
sens. = 947 W
Heating with ventilation:
T hot out = 32.0 C
RH% out = 28.6%
T hot in = 14.1 C
RH% in = 71.5%
T cold in = 20.2 C
RH% in = 58.6%
T cold out = 14.1 C
RH% out = 71.5%
compressor power = 335 W
COP = 5.4
inside
CERV
outside
total heating capacity = 1803 W
EER = 19.3 Btu/W-hr
Cooling with ventilation:
T cold out = 25.1 C
RH% out = 48.0%
T cold in = 36.7 C
RH% in = 26.7%
outside
CERV
T hot in = 21.6 C
RH% in = 61.5%
T hot out = 36.7 C
RH% out = 26.7%
compressor power = 381 W
COP = 3.5
inside
total cooling capacity = 1342 W
EER = 12.7 Btu/W-hr
lat. = 231 W
sens. = 1110 W
Ventilation only:
CERV in dehumidification mode
- tests show water removal rate of 0.5 liters/hr
- with compressor power of 300 W gives 1.5 l/kW-hr
- EnergyStar dehumidifier standard for this size is >1.0 l/kW-hr
-could be coupled with a ventless clothes drier
CERV
inside air
Future Testing
Many initial tests have been performed,
but ...many remain.
Test matrices quickly expand!
4 temperatures x 4 air flows x 4 humidities x 4 compressor
speeds
= 256 points
results look promising so far
Additional Future Options:
CERV with heat pump water heater
- heats water with a COP of 2-3 (electric water heater COP is 1
- added benefit of cooling and dehumidifying house
- with COP of 3 and 15% efficient PV panels = 45% efficiency
equivalent to solar thermal without added complexity
hot water
inside air
Other Considerations
• Evaporator Defrosting
– Frost buildup on air source heat pump when
heating in cold weather
• Condensate removal
– can possibly be used to improve condenser
efficiency
• moisture/mold/odor prevention
• end of life recycle ability
Thanks
Questions?