Presentation on the possibilities for Net Zero building using a combination of Grid Tied PV and Ductless Mini Split heat pumps. from Building Energy 2014 Tuesday seminar

1. Building Energy 2014
PV and Heat Pumps:
Net Zero Heating Solutions
Fortunat Mueller PE
Co Owner
ReVision Energy
March, 2014
Professional design, installation and service of renewable energy systems.

2. Heat Pumps and Net
Zero
• Intro
•Why Heat Pumps for Net Zero
•PV Basics
•Heat Pump Basics
•Mini Split details
•Design Processes
•Working Example

3. Who is ReVision Energy?
• Northern New England’s most experienced renewable energy
•
installer—more than 2,500 solar hot water & solar electric systems
in Maine & NH.
Expertly designed systems installed by our certified professional
solar team. Master trade licenses and NABCEP certification
carried in-house, supporting our full service mechanical
contractor approach.

4. Locations :
•Liberty, ME, Portland, ME , Exeter, NH
•Serving all of Maine and New Hampshire and SEVT and
Northern MA
Professional design, installation and service of renewable energy systems.

5. Technical Competence
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Master Electrician’s License
Master Plumber’s License
NABCEP Certification (Thermal & PV)
Maine State Solar Installer Certifications
EPA Refrigerant License
2,500+ Systems Installed to Date
Engineering in-house (P.E.)
Depth of Experience

6. Define Net Zero Building
A zero-energy building, also known as a zero net
energy (ZNE) building, net-zero energy
building (NZEB), or net zero building, is a
building with zero net energy consumption,
meaning the total amount of energy used by the
building on an annual basis is roughly equal to the
amount of renewable energy created on the site.

7. How do you get there?
• NG plus HUGE PV to offset all source
energy
• Biomass + PV (wood or pellets)
• Large Solar Thermal + PV
• Resistive Electric + PV
• Heat Pump + PV

8. Pellets + SHW + PV

9. SHW + PV + Resistive Electric

10. Heat pump as Lever for PV

11. PV + Heat Pumps

12. Mini Splits are all the rage…
• Low(er) Cost?
– Gas by wire for those without access
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No Combustion
Air conditioning as a benefit
Good fit for supplemental heat
Path to net zero with PV

13. Why Heat Pumps
• Part of a strategy to get off oil and lower
heating costs
– http://www.rmi.org/cms/Download.aspx?id=10410&file=2013-05_HeatPumps.pdf

14. Heat Pumps and Net Zero
• Allow you to heat/cool efficiently with electricity which is easily
produced renewably on site
• By taking advantage of net metering, you can easily ‘store’ the
electricity generated in the summer to use for heat in the
winter.

15. Energy Security in Reach
• Consider a very well built new home with an annual heat
demand of 40 Million BTU’s per year
– 2,000 sf ; R40/R60 insulation; Triple Pane windows; HRV
•
•
To provide 40 MMBTU with a Heat Pump at an average COP of 2.8
requires approximately 4,185 kw-hr of electricity.
To generate that amount of electricity in Maine requires about a 3.3 kW
GTPV system.
– ~200 sf of modules
– ~$7,000 Net cost (after incentives)
For that cost you are buying all the ‘fuel’ you’ll ever need to keep your
house warm for life! That is pretty awesome.

16. In one hour enough
solar energy strikes
the earth’s surface
to supply all energy
demand for one
year.
Net Zero home in
Lancaster NH.

17. • Putney School Field House in VT
• Good building practice, GTPV and Air
Source Heat pump combine to make a net
zero building

18. Solar Electric Basics
Proctor Academy, Andover, NH

19. PV System Components
Photovoltaic modules
convert sunlight into Direct
Current (DC) electricity,
which flows through cable
to the inverter.
Inverters accept the DC electricity
produced by PV modules and convert
it into Alternating Current (AC), which
then feeds demand in the building or
if there excess, feeds the utility grid.

21. Residential PV Systems

22. Ground Mounting Options

23. Inverter Replaces Batteries

24. Basic Solar Facts
• 1000-1300 kwhr/kw in New England
• 50-70 sf of modules per kW

25. Heat Pumps Basics
•
A heat pump is a machine or device that moves heat from one location (the 'source')
at a lower temperature to another location (the 'sink' or 'heat sink') at a higher
temperature using mechanical work or a high-temperature heat source

26. Thermodynamics 101

27. Temperature vs Heat
•Temperature is a number. That number is related to energy, but it is not energy itself.
•Temperature is a number that is related to the average kinetic energy of the molecules of a
substance.
•Temperature is a measure of the average kinetic energy of the molecules of a substance. An
increase in temperature results in an increase in the kinetic energy of the molecules and an
increase in thermal energy. It is fair to say that temperature and thermal energy vary directly, but
they are not the same thing.
•Heat, on the other hand, is actual energy measured in Joules or BTUs or other energy units.
Heat is a measurement of some of the energy in a substance. When you add heat to a
substance, you are adding energy to the substance. This added heat (energy) is usually
expressed as an increase in the kinetic energies of the molecules of the substance.

28. Sensible vs Latent Heat
•Sensible heat
When an object is heated, its temperature rises as heat is added. The increase in
heat is called sensible heat. Similarly, when heat is removed from an object and its
temperature falls, the heat removed is also called sensible heat. Heat that causes
a change in temperature in an object is called sensible heat.
•Latent heat
All pure substances in nature are able to change their state. Solids can become
liquids (ice to water) and liquids can become gases (water to vapor) but changes
such as these require the addition or removal of heat. The heat that causes these
changes is called latent heat. Latent heat however, does not affect the
temperature of a substance - for example, water remains at 100°C while boiling.
The heat added to keep the water boiling is latent heat. Heat that causes a change
of state with no change in temperature is called latent heat.

29. Sensible and Latent heating of
water from ice to steam
Adding Heat

30. 2nd Law of Thermodynamics
•
Says basically that physical systems tend towards
equilibrium in terms of pressure, temp, chemical
reactions.
•
Clausius statement : No process is possible whose sole
result is the transfer of heat from a body of lower
temperature to a body of higher temperature.
Commonly:
“Heat flows from Hot to Cold”

31. Except when it doesn’t
• Spontaneously, heat cannot flow from cold
regions to hot regions without external work being
performed on the system, which is evident from
ordinary experience of refrigeration, for example. In
a refrigerator, heat flows from cold to hot, but only
when forced by an external agent, a compressor.
•This is accomplished by the use of a Refrigeration
cycle

32. Refrigeration cycle
Takes advantage of the face that boiling point changes with pressure…and remember
that phase change requires/stores lots of energy (latent heat).
The Steps of a Refrigeration cycle:
(1-2) we boil a refrigerant at low pressure
(and so at low temperature too).
(2-3) we run it through a compressor to
increase the pressure
(3-4) then we condense the refrigerant at
high pressure (recapturing the
latent heat, but at a higher temperature)
(4-1) we drop the pressure through an expansion valve
and start again

33. Types of Heat Pumps

34. Cold Climate Air Source Heat
Pumps
• Multi Stage
• Made by:
Inverter Compressor (ductless
mini split)
– Hallowell (Acadia) • Made by:
– Nyle
– Mitsubishi
– Carrier
– Daikin
– LG
– Fujitsu

35. Air to Water Heat pump

36. Ductless Mini Splits
• Driving high efficiency and low
temperature performance with:
– Inverter Driven Variable speed
compressor
– Scroll Compressors
– High efficiency ECM motors
– R410 A refrigerant
• Single or Multi Split options
• Various terminal unit options
More than 50% of the air conditioning and heat pump market
worldwide is mini splits. In North America is it 2%…
…but growing

37. Single vs multi split
• Single Split
• Multi Split

38. Applications
• Supplemental Heat
• Whole house supplemental heat
• Bonus Room heating and cooling
• Central Heat Replacement
• In new construction
• Open concept
• What about backup?

39. Heat Pump Performance: COP
•
The coefficient of performance or COP of a heat pump is the ratio of the heat supplied divided
by the supplied electrical energy.
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By definition, a resistive electric heater has a COP = 1
Higher COP results in lower electric usage for the same amount of heat generated
COP depends on temperature of both source and sink

40. Mini Split Performance
• Low temperature Operation
– Heat pump keeps operating down to – 13 deg F
including 100% of rated power down to 5 deg F
• COP: = 4.1 @ 47 deg F
= 2.8 @ 17 deg F
=1.7 at -13 deg F
…and you get a super efficient air conditioner too

41. Mini Split Operating cost
comparison

42. Temperature BIN data

43. Heat Pump Performance:
HSPF: Heating Seasonal Performance Factor. (BTU/whr)
Effectively an attempt to annualize COP.
(HSPF * 0.293 = annual average COP)
Must be =/> 8 for Energy Star (tax credit)
Must be =/> 10.0 for EM HESP incentive
EER: Energy Efficiency Ratio (BTU/whr)
Cooling performance at one operating point (95 deg, 80 deg 50% RH)
SEER: Seasonal Energy Efficiency Ratio (BTU/whr)
An attempt to annualize EER.
All new AC > 13
Energy Star > 14
Typical mini split: 20-26

44. Ecotype reports

46. Design Considerations
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Sizing
Wiring
Refrigerant piping
Condensate
Noise
Snow
Need for Backup heat?
Need for Supplemental heat?

49. Need for backup heat
Depends on system location. Other than extreme cold weather areas,
many New England locations no longer need backup with the newest
generation of heat pump.

50. Need for supplemental heat
• Heat loss = Heat Gain
• With no heat source in a
room Heat Gain depends
on dT
• dT can be uncomfortable

51. Need for supplemental heat
• Heat losses: (15 BTU/hr/deg F)
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Ext Walls: 200 sq ft @R40
Ext Windows: 24 sq ft@R7
Ceiling: 160 sq ft at R60
Infiltration: 4 cfm
• Heat Gains: (228 BTU/hr/deg F)
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Interior Walls: 200 sq ft @ R3
Floor: 160 sq ft @ R3
Air Flow from open door: 100 cfm
Internal Gains: ?

52. Rule of Thumb, from Marc Rosenbaum:
“My guideline is that if people will tolerate 4°F lower than the heated space
(which in my mind means 72°F heated space, 68°F bedroom) and they
leave the doors mostly open, then a point-source heater is viable when the
heat loss is 1,000 BTU/hour and the room is occupied; 1,500 BTU/hr is
kind of my soft cut-off for considering it. Beyond that, I’ll provide some
electric resistance backup in those rooms.”
(www.greenbuildingadvisor.com)
Our rule:
“Better to have it and not need it, than to need it and not have it. Electric
resistance backup heat is cheap, and even cheaper to rough in for”

53. Converting ‘design day’ loads to
annual loads

54. Converting ‘design day’ loads to
annual loads
If not in your modeling software, you can estimate
it from ‘Design’ load:
Annual load (BTU) = ‘Design Load’* 24 * Cd * HDD /
(Design Load dT)
Where:
– ‘Design load’ (BTU/hr)
–‘Cd’ = building envelope factor (0.85)
– HDD = Heating Degree Days (deg F day) (7,770 for southern Maine)
– Design load dT = Temperature difference used in Manual J calcs (deg F)

57. Discussion/Questions
Contact us:
Fortunat Mueller
fortunat@revisionenergy.com
(207) 221-6342
Contact us:
Fortunat Mueller
fortunat@revisionenergy.com
(207) 221-6342
Professional design, installation and service of renewable energy systems.