1. Design and Operation of a Conditioning Energy Recovery Ventilator (CERV) for Passive Houses
Ben Newell and Ty Newell
January 22, 2009
Newell Instruments home; 3.2kW solar PV = 5000kWhr/year; note hops harvesting; hops provide nice summer shade for buildings
Newell Instruments Inc.
1103 N High Cross Rd
Urbana, IL 61802
Phone:

2. 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.
Newell Instr will be demonstrating these technologies with a demonstration home to be built this year in Urbana

3. Air Conditioning Experience
automotive
refrigerators
military aircraft cooling

4. Presentation Outline House Energy Characteristics
Building Conditioning Requirements
Conditioning Energy Recovery Ventilator Description
CERV Operation and Performance

5. Keeping Comfortable Lots to consider!
Not meant to be read, just indication that many things interact and the house as a whole should be considered rather than the individual design of each appliance and component
Building construction, outside conditions,
Interior components, and activities

6. 2007 Solar Decathlon House
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)
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

7. 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
Range of conditions can be accommodated, and the “optimal” solution is fairly flat…these numbers show a balance between insulation and solar panel costs
Optimal solution is fairly “flat”

8. 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
Efficient houses that are highly sealed have small energy loads, but more variable in moisture conditioning and temperature conditioning….both are important
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

9. 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

10. 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
Typical 2x4 construction with fiberglass (R11) insulation, poor sealing of structure, conventional (non-energy star) appliances, incandescent lights, etc

11. 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, TV, computer, lights, etc)
ICF (insulated concrete form)
home in Urbana IL

12. 2000sq ft Home Daily Capacities
Illinois weather requires significant air conditioning, dehumidification as well as high heating loads

13. 2000sq ft Home Comfort Comfort is a squishy concept 66-76F 30-60%rh
Different people have different preferences for comfort which can be significant
30-60%rh

14. 2000sq ft “Conventional” Home
3 x vent, 3 x UA
100 sqft windows
Conventional home loads….roughly 3x the loads as that of an economically designed efficient house

15. Conditioning Energy Recovery Ventilator
CERV
Conditioning Energy Recovery Ventilator
Not too pretty, but currently very abusive tests to over heat/overcool (totally frozen evaporator) components….so far, the system is performing great!
Low temperature heat pump air conditioning system:
Cold side air
Hot side air
evaporator
compressor
condenser

16. 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

17. *ODP (Ozone Depletion Potential) *GWP (Global Warming Potential)
Refrigerant Overview
Refrigerant
Systems
*ODP (Ozone Depletion Potential)
*GWP (Global Warming Potential)
R12
automotive 1
8100
R22
residential and light commercial air conditioning, refrigerators, and freezers
0.05
1700
R134a
residential and light commercial air conditioning, refrigerators, freezers, and automotive
1300
R410A
residential and light commercial air conditioning replacing R22
1890
R744 (CO2)
In development for automotive
HFO 1234 yf
Preliminary tests as a 134a “drop in” 4
ODP – Ozone depletion potential compared to CFC-11 (1)
GWP – contribution to global warming compared to same mass of CO2 (1)

18. 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

19. 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

20. 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

21. Heating without ventilation:
T cold in = 5.2 C
RH% in = 84.6%
T hot out = 32.2 C
RH% out = 27.5%
outside
CERV
inside
T hot in = 18.1 C
RH% in = 64.5%
T cold out = -1.2 C
RH% out = 90.7%
compressor power = 377 W
total heating capacity = 1165 W
COP = 3.1
EER = 11.1 Btu/W-hr
Energy Efficiency Ratio

22. Winter day just below freezing, air flow ~100cfm
Dec ; Typical winter day; heat side airflow ~100cfm; two defrost periods (ventilation air defrosting) shown; ~300grams of water per defrost
Defrost periods

23. Dec ; Typical winter day; heat side airflow ~100cfm; two defrost periods (ventilation air defrosting) shown; ~300grams of water per defrost

24. Dec ; Typical winter day; COP~3 is EER ~ (note SEER of 20 available….but need to see definition….has higher outdoor than our tests)

25. Very cold day ~2°F, long operation, no defrost needed
Dec 22, 2008; very cold with temperatures down to 2F; long operation with no defrost required; uses “drop-in” control which reduces the sytem’s capacity….we will implement our own control algorithm which will keep the capacity high at low temperature conditions (should be ~400 watts compressor power and 1000 to 1200 watts heating at this conditions)
“drop in” mode lowers comp power

26. Dec 22, 2008; this is about 0F outdoor; system operated at most recent cold ambient (down to -17F) with no problems, but reduced capacity (~700watts heating)
Operation at 0°F, also performed at -17°F with reduced capacity data not shown

27. Dec 22, 2008; note the drop-in mode’s initial startup condition at low speed….also note the higher COP trend at low speed…..with our own algorithm we will control speed to match the load and gain increased efficiency

28. Cooling without ventilation:
T cold out = 22.6 C
RH% out = 64.0%
T hot in = 37.7 C
RH% in = 29.0%
outside
CERV
inside
T cold in = 31.5 C
RH% in = 39.0%
T hot out = 55.4 C
RH% out = 12.7%
compressor power = 450 W
total cooling capacity = 1079 W
COP = 2.4
EER = 8.6 Btu/W-hr
lat. = 133 W
sens. = 947 W

29. Heating with ventilation:
T hot in = 14.1 C
RH% in = 71.5%
T hot out = 32.0 C
RH% out = 28.6%
outside
CERV
inside
T cold in = 20.2 C
RH% in = 58.6%
T cold out = 14.1 C
RH% out = 71.5%
compressor power = 335 W
total heating capacity = 1803 W
COP = 5.4
EER = 19.3 Btu/W-hr

30. Cooling with ventilation:
T cold out = 25.1 C
RH% out = 48.0%
T cold in = 36.7 C
RH% in = 26.7%
inside
outside
CERV
T hot out = 36.7 C
RH% out = 26.7%
T hot in = 21.6 C
RH% in = 61.5%
compressor power = 381 W
total cooling capacity = 1342 W
COP = 3.5
EER = 12.7 Btu/W-hr
lat. = 231 W
sens. = 1110 W

31. Ventilation only: CERV inside air 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

32. 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

33. 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

34. Other Considerations Evaporator Defrosting Condensate removal
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
Cradle-to-cradle concept…..technical and biological nutrients that can be re-used, recycled, or composted

35. Thanks Questions?
Watch for our announcements for the construction of our demonstration house