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Two Year Boleyn Home Results: Where does all the Energy Go?

Two years ago, my wife, Emily and I moved into our new energy efficient solar home in beautiful Happy Valley. There have been several events over the last couple of years to show its features to the public. However, for those of you who know me, the only valid claims about performance of any low-energy or net zero energy home (including my own!) needs to be shown by the actual measured energy data while the home is occupied.

 

We’ve come to the two year mark in our occupying the home, and this was a good time to report on its performance. But first of all, a little background information about our home:

 

The Boleyn “Morning Sun” Home Description

 

As some of you know, we had previously lived in our first solar powered home for over 30 years. That home was about 2800 square feet and had a solar water heater, a 2.6 kW PV system and a sun-room with extensive south windows. These features along with the  high efficiency heat pump, enabled us to get by with about 9000 kWh per year purchased from the utility company. Our Energy Utilization Index (EUI) was approximately 10 (kBTU/ft2/yr). We wanted the  new house (which we call “Morning Sun”) to have an EUI less than half that, with a design goal EUI of 4.

 

The new home is about the same size at 2836 square foot on a south facing hillside. The lot has 90% solar access with extensive window areas to capture sun and views. The house consists of two levels and an open loft. The walls have R-32 insulation and advanced framing techniques. The roof consists of 14” trus-joist rafters with a combination of two inches of sprayed in foam, supplemented with R-38 fiberglass batt insulation, totaling R-49. The lower level slab floor is completely thermally isolated from the ground and foundation by R-20 foam board insulation.

 

The home consists of 785 square feet of tuned window area (including sliding glass doors), forty-three percent of which faces south for passive solar heating. Carefully designed overhangs prevent summer overheating.

 

The PV system is a 4.725 kW system with a 4800 watt PV Powered inverter. The PV modules are placed flush-mounted on a south-facing (170 degrees) roof at a 4:12 (18.4 degree) tilt. The  PV modules, together with 7 PVT warm air collectors, are mounted in a PV/T system which captures heated warm air from the rear of the modules, and uses it to preheat water and provide supplementary space heating. The PVT system also cools the PV modules by drawing in the outdoor ambient air drawn underneath the modules. In the heating mode, this operation also provides fresh air to the house.

 

The home has 4 isolated heating zones, each with its own high efficiency ductless minisplit heat pump system. Water heating is provided by a tankless Noritz gas water heater. All other uses of energy in the house are electrical, with the sole exception of an occasional use gas fireplace used in the winter.

 

Appliances include higher efficiency Energy Star refrigerator, dishwasher, and clothes washer and an older 7 cubic foot chest-type freezer. Cooking is provided by an electric induction stove and convection oven, and microwave oven. An electric clothes dryer completes the complement of appliances.

 

Lighting is 90% compact fluorescent. Other small, continuous electricity ‘consumers’ include a home office (computer, printer), data monitoring equipment and clocks/displays. Regular uses include televisions, sound system, and PVT blower fan.

 

How we measured all the energy use

 

In order to fully characterize the performance of the house we had to collect energy use data, weather data (temperatures, solar radiation), and indoor temperatures.

 

We settled on four data “monitoring” approaches: 1) Temperature monitoring systems and third party temperature data; 2) On-site electric circuit monitoring systems; 3) Third party solar radiation data; and 4) Natural gas consumption.

 

Indoor and outdoor temperatures, hot water tank, and solar array temperatures were all being recorded by the PVT EchoFirst monitoring system. Verification of indoor and outdoor temperatures was provided by temperature loggers. Daily degree day data was downloaded from the NOAA data base for Portland International Airport.

 

Electric energy use was monitored by three systems: an Egauge system, Ecodog’s FIDO system, and supplemented by some visual kWh meter recording. The Egauge system provided data for solar electricity production, heating/cooling system consumption, refrigerator and freezer consumption, and web/computer monitoring systems consumption (16 months complete data). The Ecodog FIDO system provided data for 16 other individual electrical circuits in the household (12 months complete data). All Egauge data is Web accessible; all Ecodog FIDO data is available locally on the home computer.

 

Solar radiation data was monitored at a nearby (2 miles west) high school (Clackamas HS, Oregon). This hourly data is downloaded each month to comprise the solar radiation data base.

 

Natural gas consumption data for backup water heating was provided by visual gas meter readings. I collected readings on a daily basis for the first 5 months of operation in 2010, then on a monthly basis thereafter.

 

What we learned from the data

 

Photovoltaic energy production for the first two years was 4185 and 4082 kWh respectively. These were low compared with PVWatts predictions based on TMY3 data because of 4 weeks of downtime in May/June 2010 due to module replacement and an unusually cloudy May/June in 2011. As a result, the performance for the first two years was approximately 200-300 kWh below predicted by PVWatts.

 

Space heating is a function mostly of outdoor temperature. Spring of each year comprised of higher degree day readings relative to average. In 2011, this resulted in a season of unusually high energy consumption for space heating, especially compared to 2010. As luck would have it (for the solar enthusiast) these same months were also unusually cloudy, so the contribution of passive solar heating through south windows and the contribution to space heating from the PVT system were especially low in February and March, 2011. The 800 kWh annual difference (+30%) in space heating (heat pump) energy from 2010 to 2011 is mostly a result of the cool, cloudy Spring of 2011.

 

Space Heating Kilowatthours by Year

 

 

2010

2011

January

656

723

February

224

657

March

214

575

April

137

245

May

64

45

June

0

0

July

0

0

August

0

0

September

5

0

October

89

69

November

574

425*

December

643

727*

TOTALS

2606

3466

 

The tables below summarize the contribution of the space heating sources for each of the calendar years 2010 and 2011. As can be seen, the variation in the combination of solar radiation and degree days between the two years caused significant changes in the relative amounts of energy sources for space heating.

 

2010 Heating Sources

All in kWh(th)

Heating Load

Heat Pump Delivered

PVT

Passive Solar

January

2077

1038

18

153

February

1889

786

133

970

March

1976

749

175

1052

April

1700

485

186

1029

May

1481

238

131

1112

June

0

0

0

0

July

0

0

0

0

August

0

0

0

0

September

0

0

0

0

October

1532

329

32

1171

November

2185

1878

25

282

December

2327

2147

7

174

 

15,167

7,650

706

5,943

2011 Heating Sources

All in kWh(th)

Heating Load

Heat Pump Delivered

PVT

Passive Solar

January

2421

2364

9

72

February

2342

2140

35

249

March

2088

2010

38

94

April

1933

870

186

820

May

1501

171

206

1123

June

0

2

0

0

July

0

0

0

0

August

0

0

0

0

September

0

0

0

0

October

1426

263

115

1048

November

2039

2034

47

390

December

2619

2874

18

62

 

16,374

12,732

655

3,859

 

The next two tables summarize the monthly fuel use for heating water:

 

Therms of Natural Gas Per Month (Water Heating)

 

2010

2011

January

5.4*

5.5*

February

2.7

3.1

March

2.7

3.2

April

2

2.1

May

2

0.9

June

1

1.2

July

0.7

1.1

August

0.8

0.7

September

1

0.9

October

1.6

2.1

November

3.5

4.7*

December

7.1*

8*

TOTALS

30.50

33.50

 

Contribution to Water Heating from PVT System

 

2010 (kWh)

2010 (Therms)

2011 (kWh)

2011 (Therms)

January

12.31

0.42

16.66

0.57

February

55.40

1.90

27.67

0.95

March

69.02

2.36

27.34

0.94

April

65.29

2.24

65.30

2.24

May

87.06

2.98

70.29

2.41

June

94.12

3.22

69.63

2.38

July

139.91

4.76

133.19

4.56

August

118.42

4.06

127.52

4.37

September

92.98

3.18

115.95

3.97

October

59.63

2.04

37.89

1.30

November

18.77

0.64

24.68

0.85

December

11.06

0.38

22.98

0.77

TOTALS

823.97

28.2

739.09

25.31

 

Where does all the Rest of the Electricity Go?

 

Mysterious to many consumers is the electricity used by the myriad of appliances, etc. In the FIDO-monitored circuits, an attempt was made to find out exactly where it all goes. See the table at the end of this section for the results.

 

Refrigerator/Freezer: The home has two refrigeration devices: a 30+ year old 7 cubic foot chest freezer, and a brand new (2009) Energy Star 22 cf refrigerator. The old freezer uses the most and varies from month to month because of the freezer’s location in the garage (warm in summer, cold in winter). In the coldest months, the consumption is 27 kWh per month, and in the warmest summer month, 51 kWh. The indoor refrigerator, on the other hand, uses a steady 29 kWh per month year around. At 780 kWh per year between these two appliances, they comprise 10% of the home’s gross electricity consumption.

 

Lighting: Lighting consumes the second largest amount of energy by end use with again a seasonal component, being higher in winter. At 400 kWh per year, lighting consumes approximately 5% of total electricity consumption. All lights, with the exception of a dining room chandelier and two dimmable fixtures in the master suite, are all compact fluorescent bulbs.

 

Staying Connected:  Communications systems are an increasingly large load in modern households. With solar (PVT) controller, the web/internet modems and routers, and energy monitoring systems in this home, these devices comprise 573 kWh, or about 7% of annual gross load.

 

Keeping Clean: The clothes dryer and dishwasher are thr two most consumptive “cleaning” devices. In a household of two working adults, the clothes dryer was used for 2-3 loads per week resulting in 329 kWh per year, about 2.5 kWh per load; the dishwasher was used 4-5 times per week and consumes 247 kWh per year, about 1 kwh per load. Around the holidays, dishwasher usage goes way up with parties, guests, etc.

 

Cooking: The range/cooktop/oven only consumed 185 kWh per year, or about 2.5% of loads. The household uses a highly efficient induction cooktop daily for at least two meals each day; the oven is used lightly, about twice per week except during holidays.

 

Christmas Lighting: The occupants celebrate the Christmas season with both indoor and outdoor Christmas lights. The home consumed 141 kWh per year in Christmas lighting which includes multiple outdoor mini-light strings, a large well-lit Christmas tree, and assorted colored lights throughout the house.

 

Miscellaneous small appliances: With monitoring, small uses, such as clocks, TV and appliances are made visible. The only identifiable loads not monitored during this period were: washing machine, central vacuum cleaner, garage door opener, irrigation pump, and some outdoor lighting.

 

Heat Recovery Ventilator: Being a tight LEED Platinum house, an HRV is a required piece of equipment. This device, as used in this home, is turned on for 30 minutes every day, and at the rate of 165 watts, the HRV uses just 30 kwh per year.

 

PVT System Fans/Controls: The workhorse of the Photovoltaic Thermal system that extracts heat from the PV modules and heats water and supplementary space heating, is the PVT system blower fan. This fan consumes about 300 watts when on. Its annual usage is slightly larger than 300 kWh per year, or about 3.75% of annual load. This device leveraged approximately 1400-1500 kWh of useful thermal energy and contributed to keeping the solar PV modules more efficient.

 

Monitored Miscellaneous Electricity Uses

 

Energy Use

kWh per year

Freezer

432.51

Electric Lights

406.0

Modem/Router

363.5

Refrigerator

349.78

Clothes Dryer

329.69

PVT Blower

305.69

Dishwasher

247.63

PVT Controller

210.2

Cable TV Box

201.5

Range/Oven

184.9

Christmas Lights

141.1

Stereo Amp

131.5

Smoke Detectors

122.6

Computer

107.5

Bedroom clock & phone charger

60.4

Electric Blanket

42.6

HRV

30.1

TV

17.0

Small appliances

9.4

Total Monitored Miscellaneous Use

3694.0

Unmonitored Miscellaneous Use

548.1

Total Annual Miscellaneous Use

4242

Misc Use Per Day (avg)

11.62

 

Will the Boleyn’s Ever Get to Net Zero?

 

The total gross energy consumption of the home for the first two years averaged 8000 kilowatthours per year in the form of electricity, and another 60 Therms (6 MMBtu) of thermal energy for water heating.

 

Of these approximate 8000 kilowatthours of  electricity consumption, about 3000 kWh is consumed for space heating (heat pumps), and the remainder for all “miscellaneous” uses. Of this 8000 kwh in the form of electricity, about half (~4,000+ kWh) was provided by the solar photovoltaic system, and the remaining ~4000 kWh purchased from the utility. Of the 60 Therms of energy required to heat water, about half is provided by solar heating via the PVT system (~30 Therms/3MMBtu).

 

Can we ever think to reach a “net zero” status? It’s possible through four approaches: 1) Getting rid of the “true waste” and removing appliances; 2) Expanding the photovoltaic system; 3) Waiting for an “average” year!; and 4) Expanding the occupants’ comfort zone.

 

Getting rid of waste: “True waste” came in the form of cable TV boxes consuming 10-25 watts continuously when no one was watching TV, stereo amplifiers that consume 25 watts when no music was turned on, and the parasitic energy consumed when the heating/cooling system is idle and not providing either heating or cooling (thermostat, control circuit energy).

 

This identified “true waste” could result in a possible 500 kWh per year savings, or 6.25% savings. These items could be controlled by simply turning off at a power strip, or in the case of the heating system, turning off at the breaker for the 6 months of non-use.

 

The removal of the old freezer in the garage would result in another 400+ kwh annual savings, or approximately 5% of annual use. To this point, the occupants have found the freezer very useful. It’s yet to be investigated as to whether a new small freezer would save enough energy to make a swap practical.

 

Expanding the photovoltaic system:  Adding another 2-3 kW, bringing the system up to 6.75 to 7.75 kW, of photovoltaic modules would enable the home to approach “net zero”. The home has some constraints with roof area, however, that could make this addition challenging, but it could be done.

 

How about just waiting for an “average” year? Since the first energy predictions were made when the home was first occupied, the two years of 2010 and 2011 had a combination of below average solar radiation and high degree days which increases heating useage. With the home being dependent on solar radiation to reach energy savings goals, low radiation has a large effect on purchased energy consumption in numerous ways: 1) Less passive solar heating in winte; 2) PV electricity production is down; 3) PVT Thermal energy for space heating is less; and 4) PVT Thermal energy for water heating is less.

 

Here’s a table of actual energy use versus predicted use based on “normal” weather years:

 

 

TABLE 9:  MORNING SUN PREDICTED PERFORMANCE (TMY3) vs ACTUAL

 

Month

PredictedNet Utility Electric Use (kWh)

Actual 2010

Actual 2011

 

 

 

 

January

665

1016

972

February

345

373

806

March

52

232

704

April

50

70

175

May

-198

113

-122

June

-202

-29

-112

July

-172

-205

-232

August

-98

-120

-171

September

16

-4

-3

October

148

132

227

November

453

870

860

December

788

1084

1341

TOTAL

1848

3532

4445

Est cost:

$185.00

$353.00

$445.00

 

Expanding the “comfort zone”: We are now in our retirement years, and maintaining comfort temperatures between 68° and 78° is very important. Indeed, the true value of a low energy home is to provide delightful levels of comfort with very low purchased energy consumption.

 

Therefore, allowing temperatures to drop below 68° in the winter or climb above 78° in the summer in order to save energy, is something we’re not too keen on.

 

In Summary…

 

The Boleyn home is an energy efficient home producing high levels of comfort, high levels of natural and beneficial daylighting, all while significantly minimizing the use of purchased and fossil fuels.

 

With an annual electric bill of ~$400 and an annual natural gas bill of ~$35, the home approaches “net zero”, but is not there. Nevertheless, it feels good to have such a use in a neighborhood where some homeowners pay $400 per month for energy.

 

2012 is half over, and is turning out to be a better (lower energy use) than both 2010 and 2011, but that’s a story for another time…

 

What’s next?

 

We need to present and publicize many more examples (with real data) of low energy use homes, with different styles and energy efficiency approaches. The Passiv Haus model and other approaches have been successfully built by Oregon builders and occupied by Oregon homeowners. We just need to show them off!

 

If you have built a home, or are living in a “low-energy use” home, make sure someone at Solar Oregon knows. And if you need help or advice in getting your energy use measured, let me know, and I’ll see if I can point you in the right direction!

 
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