Residential Solar Power in
Midwest
Patrick Chapman
Associate Professor
University of Illinois at
Urbana-Champaign
February 4, 2008
Example: Illinois Energy Picture
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Dominated by nuclear, coal
Some wind power
Solar power << 1%
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New Illinois Power Agency reportedly:
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Requires 25% of Illinois energy from renewable
sources by 2025
Requires 2% by June 1, 2008
75% of this must be wind
Governs net metering and other aspects of power
Illinois Energy
2006 data:
5th in population
10.37¢/kWh residential
18 GWh of generation
17.3 GWh =coal +
nuke
Illinois Solar Map
~ 4000 Wh/m2 per
day
Source: DOE
More-Detailed Maps
Provided by Angus Rockett, Univ. of Illinois
Growth Internationally
Chart from US Photovoltaic Industry Roadmap (NREL, 2001).
PVWatts (NREL)
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Based on collected solar data (only select
years)
More reliable that clear-sky calculations
Available for certain sites
Specifications
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Tilt = latitude
Azimuth = true south
0.77 derating factor
“Solar Advisor Model” from NREL
PV Economic Viability
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Varies from place to place
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Solar radiation
Cloud cover
Price of electricity
Real-time pricing vs. fixed pricing
Installation costs (labor)
Demand for modules
Availability of installers
Rebates and incentives
Calculations for Select Sites
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For a 1-kW array
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Rockford: 1212 kWh/yr ($0.089/kWh)
Springfield: 1281 kWh/yr
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Long Beach: 1449 kWh/yr ($0.136/kWh)
Tucson: 1617 kWh/yr
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Portland, ME: 1280 kWh/yr ($0.128/kWh)
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Quick multiplier: 1250 kWh/yr/kW-installed
National average in 2007: $0.097/kWh (all
sectors) – Hawaii is about $0.21/kWh
Specifications
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Tilt
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Tilt = latitude good rule of thumb
Slightly shallower is optimal
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Azimuth
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Diffuse and reflected light are significant
True south optimal
+/- 15 degrees OK
Watch out for magnetic south
Derating – 77% typical starting point
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PV module hero numbers (few %, temperature)
Inverter efficiency (94%)
Wires (98%-99%)
Dirt, aging (few %)
Mismatches (few %)
PV Module Efficiency
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Ratio of electrical power out to sunlight power
in
Notice, not included in specifications
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Key figure of merit is $/W or $/Wh
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Somewhat overrated figure of merit
Higher efficiency = smaller space
Higher efficiency = higher cost (usually)
Aesthetics also important
10% to 14% typical for silicon
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22% for SunPower modules
Illinois Rebate Programs
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State rebate program
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Federal tax credit
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30% of project costs
Maxes out at $10,000 <<< Note, taxable grant
Limited budget (ran out of money last FY)
Straightforward application, but takes time/care
30% of project costs
Maxes out at $2,000
Commercial – similar programs
Illinois Clean Energy Community Foundation
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Other, larger scale projects
Case Study in Urbana
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2.87-kW array
Based on Springfield data
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3669 kWh/yr
30-degree tilt (pitch 7’x12’)
15 degrees west of south
0.77 derating (conservative)
SunPower system
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14 205-watt modules
3300-watt inverter
Photos Case Study
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Initial work
More Photos
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Racking
More Photos
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Modules
More Photos (Inverter and Monitor)
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Inverter and Monitor
Finished Project
Connecting to Ameren
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Somewhat complicated, but cooperative
Register with FERC as QF
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Submit schematic and specs to Ameren
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Pay $100
Their engineer will approve drawings
Sign connection agreement
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Qualifying Facility
Self-certify – not difficult, just annoying
Can request waivers on insurance, etc.
Sign QF Rider agreement
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Pick real-time pricing or normal rates ($333 meter)
Example Schematic
Real-Time Pricing
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Price peaks more/less with sun
Pricing
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Smart Power Pricing program
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Recent legislation allows net metering
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Administered by CNT
$2.25 per month participation
Get wholesale price (Ameren providing wires, this is
fair)
Get the retail price
Eliminate Smart Power Pricing?
The Public Utilities Act is amended by adding 5
Section 16-107.5 as follows…
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Ameren to provide free meter… (?)
Sample Billing (9/24-10/23)
Usage (kWh)
PSP Billing (net
energy consumed)
9
8
7
6
5
4
3
2
1
1
26
51
76
101
126
151
176
201
226
251
276
301
326
351
376
401
426
451
476
501
526
551
576
601
626
651
676
0
This is the energy
supply charge.
Distribution (“the
wires”) costs
$0.0245/kWh
Total Energy: 861
kWh
Total Price: $51.37
= $0.0596/kWh
Price ($/kWh)
0.8
0.7
0.6
0.5
0.4
$0.71 at noon,
10/8
0.3
0.2
0.1
-0.1
1
26
51
76
101
126
151
176
201
226
251
276
301
326
351
376
401
426
451
476
501
526
551
576
601
626
651
676
Total = $0.084/kWh
0
Sample Days
0.8
0.7
0.6
0.5
0.4
8-Oct
1-Oct
0.3
0.2
0.1
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Saving $20 to $40 per month compared to flat rate
1
17
33
49
65
81
97
113
129
145
161
177
193
209
225
241
257
273
289
305
321
337
353
369
385
401
417
433
449
465
481
497
513
529
545
561
577
593
609
625
641
657
673
689
Generated Power
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-133 kWh
0
-0.5
-1
-1.5
-2
-2.5
Generated power
One Day Example (kW-hr vs. hr)
8-Oct
0
-0.1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
-0.2
Peaks nearly line up,
maximizing the benefit
-0.3
-0.4
Note this is net
generation
-0.5
-0.6
-0.7
-0.8
Oct 8 Prices
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
On “negative load”
generation, effectively
get the retail price
Economics
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Upfront cost, about
$27,000
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Breakdown in cost per
watt
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$4.50 for PV modules
$1.00 for inverter
$3.50 for installer labor
and markup
Rebates
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$9 per peak watt, installed
$8,100 for IL (took eight
months to receive check)
$2,000 for Federal
Net cost: $16,900
“Investment” Analysis
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At $0.10/kWh = $366.90/yr yield
Simple payback, a mere 46 years!
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This is unfair to PV
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(PV held to near impossible standard)
Need to look at
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Amortized cost (buying all power upfront)
Equity
Increases in electricity prices (real time price?)
Environmental advantages
More Econ
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Realtors estimate $1,000 savings = $20,000
equity
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$366.90  $7,338 in equity, and rising
Net out-of-pocket = $9,562
Assumes there is a willing buyer
4% rise in rates = 50% increase in prices in 10
years – effects payback and equity
More Econ
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As part of home mortgage
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6.75% (30-yr) mortgage, interest is initially
$95/month ($66.50 after taxes)
$33.58 in energy per month – about $33 per month
deficit
Year 15, prices go up, interest is down
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$55/month savings, $49/month interest
Equity is $13,200, not much less than the $16,900
upfront cost
Other “investments”
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A 4% CD would have generated $13,536 in
income on $16,900 principle
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15 years of electric savings lost
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After taxes, this is ~$10,000 yield
About $500 per year on average
~$6,000 in 15 years of savings lost
Net yield on the (CD – electricity) is $4,000
This is about an $8,000 deficit
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This is about $44/month average “luxury” price for
the electricity, or about $0.15/kWh
Gets better with more time
For Comparison
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Other things that cost $17,000…
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Conservative?
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BMW 500 over a Toyota Prius
Extra bedroom
One semester out-of-state tuition at Illinois
Etc.
Rates may go up faster
PV costs will go down
Home interest rates lower
Unconversative?
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Repairs, maintenance, other risks
Cost Drivers and Trends
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Manufacturing costs for PV modules going down
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Prices still high due to shortage
Competition in China coming fast
Must achieve $3/Wp installed cost and 25 year warranty to have
grid parity
PV Module Costs
Source: Evergreen Solar
2007 Solar Decathlon
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Dept. of Energy Sponsored Event
Large national media attention – National Mall
Draw awareness to solar power
20 universities to build solar houses
10 events (with overall prizes)
Contests
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Architecture (200 pts)
Engineering (150 pts)
Marketability (150 pts)
Communications (100 pts)
Comfort Zone, Getting Around, Hot Water,
Lighting, Appliances (100 pts)
Energy Balance (100 pts)
Univ. of Illinois Finish
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9th overall
1st in
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Comfort Zone (best passive solar and HVAC
design)
Marketability (very affordable, ordinary building
materials, expandable)
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Homes limited to 800 sq. ft.
Multitude of other limitations and rules
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Accepted for 2009 competition
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Final Illinois House on the Mall
($450k)
Source: SD07 photos from solardecathlon.org
Winning Overall House
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Darmstadt ($2M)
Other Remarkable Houses
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Georgia Tech, Missouri-Rolla
Other Remarkable Houses, cont’d
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Santa Clara, Lawrence Tech
Passive Home Design for 2009
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Passive heating and
cooling is largely
feasible in the Midwest
PassivHaus Institute
US (PHIUS) is located
in Urbana
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Superinsulated homes
(1200 sq. ft.)
No central air
conditioning of furnace
Earth-tube intake
Southern exposure
adequate for PV – a 1kW system = zero net
energy
Source: e-colab.org
Summary
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PV taking off but still just off the ground
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“normal” people now taking notice
Midwest is a poor economic case
Environmental improvement is worth?
Still makes most sense to do conventional
efficiency improvements first
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Insulation, sealing
Compact fluorescent lighting
Better HVAC (geothermal, etc)