September 9, 2008
Download a PDF of this update here.
Download complete energy and performance data sets here.

Background

In April 2007, EcoGauge data monitoring providers outfitted Solar Harvest with temperature, energy and comfort system sensors that broadcast signals live to the web, enabling Solar Harvest to be one of the first net-zero energy homes to provide performance verification data to the public.  The performance data gathered is be displayed both live on the web (figure 1) and in excel spreadsheets for trending and graphing

The energy side of Solar Harvest’s data monitoring system, featured in this performance update, is centered around a web energy logger that connects to 2 “Watt Node” Pulse Output Meters by Continental Control Systems (figure 2).  These advanced energy-monitoring devices accurately track how much energy the PV system is producing and how much electricity the home is “buying” from or “selling” to the grid.  It is using these numbers that we can most accurately judge whether Solar Harvest has met its net-zero energy goal, as featured in this update.

 

Figure 1: click here to go to the Solar Harvest live monitoring website

Figure 2: WattNodes by Continental Control Systems track energy use in the home

We are proud to announce that data collected over the past year supports what we have known is true: Solar Harvest is a net-energy producer!

For the all plug loads, appliances, HVAC, spa and other electric demands, Solar Harvest used 2.19 kWh per square foot.

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2008 Solar Harvest NZEH Monitored Data Result Summary

Solar Harvest produced 1,165 kWh more electricity than it consumed from September 1, 2007 – August 31, 2008*


*September 1, 2007 - August 31, 2008 was selected as the first year annual energy summary date range because this range accurately tracks energy used when the home is fully all-electric.  Prior to September 1, 2007, natural gas appliances were used for cooking and clothes drying.   Also, as of September 1, 2007, the supplemental 1.9 kWh PV power was fully online & producing energy.

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Solar Harvest Annual Net-Energy Production Summary Table

Key points:

• As a 4,500 sf home, Solar Harvest uses 2.19 kWh/square foot for all of its energy needs including appliances, electronics, fans, and outlets
• Solar Harvest produced a surplus of 1,165 kWh
  

A surplus of 1,165 kWh could have:

• Driven an all-electric car 4,369 miles (at 3.75 mi/kWh)
• Saved Eric Doub & his family 97 gallons of diesel (@ 45 mpg)
• Which means, Eric could have saved $439 worth of diesel last year!

A surplus of 1,165 kWh sent to the grid also means:

• 3,495 kWh not produced at Xcel's power plants for use in other homes
• 2,085 lbs CO2 avoided from being produced for use in other homes

* Add this to the CO2 emissions avoided because Solar Harvest consumed of solar energy for most of its needs throughout the course of the year, and Solar Harvest prevented 17,422 lbs of CO2 from entering the atmosphere!

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2008 Solar Harvest Cooling Season Energy Results
July 2008

During the month of July, 2008 Solar Harvest met the goal of being a net-energy producer.  This data points out the phenomenal thermal performance of the home, and of the Coolerado Cooler, whose installation faced some initial criticism from builders and spectators of the net-zero energy home world.  

Even with the Coolerado air conditioner going full time in July 2008, Solar Harvest used consumed about 660 kWh and produced 1095 kWh, for a net production of 435 kWh.  That is a very powerful metric:  That a 4,500 SF house, cooled to 72F, 24/7, in a heat wave with over 23 days over 90F, used only 660 kWh!  

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NEXT UPDATE: Daily peak energy data

RELATED INFORMATION:
Looking for a complete set of downloadable energy & comfort systems spreadsheets?  Visit our WEL logs page here.