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LEAST COST ANALYSIS FOR SOLAR
PHOTOVOLTAIC MAINTENANCE at the WMU Miller Array
Kelsey PitschelMechanical Engineering Dr. Harold GlasserWestern Michigan University
Thesis Defense Lee Honors College Spring 2016
Agenda
- Background- Problem Statements- Best Practice - Methodology - Results & Analysis - Recommendations
Background - Miller Array at WMU
50 kW DC total
18 ground-mounted poles
One degree of freedom
South facing
Microinverters for each module
Background - Photovoltaics
Directly convert sunlight into DC electricity
More efficient in cooler temperatures
Not as common in the midwest
Problem Statement Adjusting:
Are we currently maximizing WMU’s cost savings (or personnel time) at the Miller Array?
Do we need to adjust the panels?
Do fixed panels produce a competitive amount of annual energy savings?
Cleaning:
Do we need to clean the panels?
Best Practice / Industry Standard
Tilt Angle: Slightly less than latitude
Cleaning occurrence: 1-2 times/year
Annual cost for maintenance: $30/kW-year
Method: Scrub brush with deionized water to remove soiling
Methodology
1. Assess existing procedures / Determine expectations 2. Develop proposed schedules 3. Facilitate proposed schedules / Data collection 4. Determine energy cost savings / Maintenance costs 5. Provide recommendations
Method - Metrics
Energy produced (kWh), per panel
Electricity Costs ($/kWh), based on annual average
Maintenance Rates ($/hr), based on WMU official rates
Net annual savings or costs ($/year)
Method
Cost Savings
energy cost savings ($) = energy produced (kWh) x electricity utility rate ($/kWh)
Net Annual Savings
net annual savings ($) = [energy cost savings ($) - maintenance costs ($)]annual
Typical daily power trends, spring
microinverter
Existing Procedures
Existing - Adjustment Schedule
Existing Tilt Schedule
Season Date Angle (deg from horiz)
Spring Feb 27 40
Summer Apr 20 20
Fall Aug 22 40
Winter I Oct 13 70
Winter II At first snowfall Near vertical
Rates and Costs
Typical Labor Hours and Rates, WMU
Equivalent hours to adjust entire array 3.31 hrs
Typical pay rate, 2013 $58.48/hr
Typical pay rate, 2014-16 $60.83/hr
Annual Electricity Utility Rates
2013 $ 0.1106 /kWh
2014 $ 0.1087 /kWh
2015 $ 0.1005 /kWh
Currently entire array requires 27.2 equivalent personnel hours / year
Existing - Adjusting Results
Existing - Cleaning
Entire array would need to increase its margin of energy generation by
4,000 kWh each year
in order to offset cost for cleaning.
Currently, no cleaning measures for solar panels at WMU.
Proposed Schedule Design
Expectations - Tilt
According to NREL’s PVWATTS Calculator:
Adjustment Schedule Design
Procedure - Adjustments, Proposed
Proposed Tilt Schedule, Group 1
Season Date Angle (deg from horiz)
Spring Feb 15 40
Summer Apr 1 20
Fall Sept 1 40
Winter I Oct 15 60
Winter II Dec 1 Near vertical
Procedure - Adjustments, Proposed
Proposed Tilt Schedule, by Group
Group 1 Group 2 Group 3
Seasonal Industry Standard Fixed Rooftop Fixed
5 times per year* Fixed at 35 degrees Fixed at 20 degrees
Panels 1 - 7 (west) Panels 8 - 14 Panels 15 - 18 (east)
3 panels cleaned 3 panels cleaned 2 panels cleaned
*Refer to Group 1 Seasonal Tilt Schedule
Proposed Array Schematic
EastWest
Note: Perfect day for solar panels
Array Configuration
Group 1
Group 2
Group 3
Procedure - Cleaning
Proposed Cleaning Schedules
For: Group 1 Group 2 Group 3
Panel Number 1, 2, 3 12, 13, 14 15, 16
Dates of Cleaning June 1 / Oct 1
Process
Analysis Adjustments
Tilt Adjustment Results
Annual Energy Production, by group
Analysis Cleaning
Analysis - Cleaning
0.31% increase in annual energy production when cleaned
Cleaning Cost
For WMU, 10 hours of available personnel time each year
Analysis - Cleaning
Difference between clean and dirty net savings = $606
Recommendations
Adjusting:
Are we currently maximizing WMU’s cost savings (or personnel time) at the Miller Array? No.
Do we need to adjust the panels? Not really.
Do fixed panels produce a competitive amount of annual energy savings? Yes.
Cleaning:
Do we need to clean the panels? No.
Without cleaning, we do not require 10 hours of personnel work each year.
$760 $5,400 $6,160+ =
Annual savings without adjusting...
avoided cost of adjusting
energy production for
entire array
total for each future year
or 27 personnel hours
The least cost maintenance solution is no maintenance at all.
$5,400+ annual cost savings from energy production
with 27 personnel hours able to be allocated to other tasks
Acknowledgements
Dr. Harold Glasser, Committee Chair
Chris Caprara, Committee Member
Elijah Lowry, Student
WMU Facilities Management
WMU Office for Sustainability
WMU Lee Honors College
Questions?
Pocket Slides
Future Research Suggestions
Compare performance between Miller, Wood, and Sangren solar arrays
Identify any declines in panel performance over time
Determine trends between EV charging consumption and panel production
Compare performance on microinverters and string tied inverters
Snow is real
