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CHA Residence

Chungha Cha and his architect, Franziska Amacher, approached the Transformations, Inc. booth in March of 2012, at the Northeast Sustainable Energy Association BuildingEnergy12 Conference in Boston, MA. Discussions shortly began as to how one might renovate a two-family property he recently purchased. His goal was to rebuild the two apartments with energy efficiency in mind and to strive for as close to a “net-zero” annual consumption as possible.

Cha Residence - Apt. #1 PV System

Basics

  • System Size: 6.86 kW STC DC
  • Mounting: Roof
  • Annual Load: 7,638 kWh

Production

  • Estimated Annual Production: 7.25 MWh per Unit
  • Actual first 11 Month Production: 8.08 MWh per Unit

Economics

  • Utility savings over initial 25 year term: $26,644 (assumes 1.5% Utility rate escalator)
  • Average monthly utility savings: $89.00 (over system life)
  • Payback Period: 8-9 years

System Details

  • 28 SunPower 245 W panels
  • 28 Enphase M210 Micro-inverters
  • Enphase Envoy monitor
  • Enphase Enlighten on-line PV system and individual micro-inverter production tracking
  • Locus Energy LGate 101E with 10 year automatic production reporting for SRECs

25 Years of Carbon Offsets

  • 124 tons of C02
  • Small Car: 421,356 miles
  • Medium Car: 220,000 miles
  • SUV: 158,344 miles
  • Air Miles: 256,289
  • Trees Planted: 4,932
  • CO2 from Trash and Waste: 226 Americans

Transformations, Inc. offered a unique perspective. Because Cha and Franziska wanted to derive energy from clean sources and keep the properties fossil fuel free, we recommended a hybrid solar system that would provide both solar thermal and solar photovoltaic energy.

We proposed two identical 6.86 kW Hybrid Solar systems evenly split between two viable roofs. The hybrid solar systems would be composed of SunPower 245 Watt panels with SunDrum Solar Thermal collectors mounted underneath twelve of the PV panels on the main roof. This design allowed the entire main roof to be used to generate PV production by not sacrificing space to traditional Solar Thermal collectors.

To further increase efficiency and address some shading constraints, we designed the PV system with Enphase micro-inverters. They can increase system production by as much as 8 percent.

These micro-inverters come with an Envoy monitoring system that gives virtual real-time access to the production of each individual panel. The web-based Enlighten software provides system owners and installers with detailed performance information and analytics about the solar system, as well as at-a-glance views and automated alerts.

A Locus monitor was also included with each system. It permits the monitoring of both the PV and Thermal systems. It is revenue grade and automatically reports the PV systems’ production for the generation of SRECs.

In the nine months since activation, each system has generated 7.3 MWh and 6 million BTUs. The carbon offset is already the equivalent of 130 trees, or over 5 tons of carbon. This hybrid solar system is on track to exceed all production estimates and achieve a “net-zero” energy status.