An Example of Residential

Solar RetrofitShawn Fitzpatrick, P.E.

Energy EngineerAdvanced Energy

September 30, 2014

House Before Solar Retrofit

House Description Before Retrofit

• 900 sq.ft. conditioned space, 2 bedroom, 1 bath

• Built in 1949• No floor or wall insulation and poor

R11 ceiling insulation• Single pane windows• Gas heat, Electric AC• Electric tank type water heater• Electric cloths dryer

House After Solar Addition and Renovation

How Bad will PV Shading Be?

The Solar Pathfinder• Hemispherical reflection on dome is

traced on sun chart with grease pencil• Similar new devices are electronic with

digital camera

Solar Pathfinder Shadow Trace

• One trace gives information for every month and hour in the year

• Add up unshaded percentages for each month

• This gives the percentage of solar availability for each month

Solmetric SunEye - Digital Shade Analyzer

Calculation of Shade Factor from Pathfinder

MonthSun Chart % Solar

AvailabilityAvg. Sunhours/Day

(kWh/m2-day)Available Sun Hours

(kWh/m2-day)

Jan 56.0% 3.8 2.13

Feb 61.0% 4.5 2.75

Mar 68.0% 5.2 3.54

Apr 73.0% 5.7 4.16

May 97.0% 5.7 5.53

Jun 95.5% 5.7 5.44

Jul 97.0% 5.6 5.43

Aug 78.5% 5.5 4.32

Sep 70.5% 5.2 3.67

Oct 63.0% 4.9 3.09

Nov 57.0% 4.1 2.34

Dec 51.0% 3.6 1.84

Average   5.0 3.68

    Shade Factor 0.74

How Is the PV Doing?

• PV modules are now 21 years old. They were originally installed on a Duke Energy project in Charlotte, NC in 1993.

• I installed my second-hand PV in February 2006 (~ 8 yrs. ago)

• The average annual solar production for recent 6 years was 2067 kWh/yr.

• Based on PV Watts software, PV was expected to produce 2290 kWh of electricity per year

• PV production over last 6 years is within 10% of expected

PV Generation and House Usage

2007 2008 2009 2010 2011 20120

500

1000

1500

2000

2500

3000

3500

4000

4500

2406

2918 2988

39083718

3583

House kWh Usage Solar PV kWh Generation

Ele

ctri

cal En

erg

y (

kW

h)

How Is the PV Doing?

• PV generation has remained almost constant over 6 years (varied with weather)

• House consumption has increased somewhat during this time but leveled out the last few years

• 2007 PV generation equaled 87% of house consumption

• 2012 PV generation equaled 56% of house consumption

2012 Monthly Solar Generation and House Usage

Jan-

12

Feb-

12

Mar

-12

Apr-1

2

May

-12

Jun-

12

Jul-1

2

Aug-

12

Sep-

12

Oct-1

2

Nov-1

2

Dec-1

20

100

200

300

400

500

600

700

House kWh Usage Solar PV kWh Generation

Ele

ctri

cal En

erg

y (

kW

h)

Shawn Fitzpatrick, P.E.Energy EngineerAdvanced Energy

919 857-9032sfitzpatrick@advancedenergy.org