Residential Solar Power in Midwest -...
Transcript of Residential Solar Power in Midwest -...
February 4, 2008
Residential Solar Power in Midwest
Patrick ChapmanAssociate ProfessorUniversity of Illinois atUrbana-Champaign
Example: Illinois Energy Picture
Dominated by nuclear, coal Some wind power Solar power << 1%
New Illinois Power Agency reportedly:– 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 population10.37¢/kWh residential18 GWh of generation17.3 GWh =coal + nuke
PVWatts (NREL)
Based on collected solar data (only select years)
More reliable that clear-sky calculations Available for certain sites Specifications
– Tilt = latitude– Azimuth = true south– 0.77 derating factor
“Solar Advisor Model” from NREL
PV Economic Viability
Varies from place to place– 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
For a 1-kW array– Rockford: 1212 kWh/yr ($0.089/kWh)– Springfield: 1281 kWh/yr
Quick multiplier: 1250 kWh/yr/kW-installed
– Long Beach: 1449 kWh/yr ($0.136/kWh)– Tucson: 1617 kWh/yr
– Portland, ME: 1280 kWh/yr ($0.128/kWh)
National average in 2007: $0.097/kWh (all sectors) – Hawaii is about $0.21/kWh
Specifications
Tilt– Tilt = latitude good rule of thumb– Slightly shallower is optimal
Diffuse and reflected light are significant
Azimuth– True south optimal– +/- 15 degrees OK– Watch out for magnetic south
Derating – 77% typical starting point– PV module hero numbers (few %, temperature)– Inverter efficiency (94%)– Wires (98%-99%)– Dirt, aging (few %)– Mismatches (few %)
PV Module Efficiency
Ratio of electrical power out to sunlight power in
Notice, not included in specifications– Somewhat overrated figure of merit– Higher efficiency = smaller space– Higher efficiency = higher cost (usually)
Key figure of merit is $/W or $/Wh– Aesthetics also important
10% to 14% typical for silicon– 22% for SunPower modules
Illinois Rebate Programs
State rebate program– 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
Federal tax credit– 30% of project costs– Maxes out at $2,000
Commercial – similar programs Illinois Clean Energy Community Foundation
– Other, larger scale projects
Case Study in Urbana
2.87-kW array Based on Springfield data
– 3669 kWh/yr– 30-degree tilt (pitch 7’x12’)– 15 degrees west of south– 0.77 derating (conservative)
SunPower system– 14 205-watt modules– 3300-watt inverter
Connecting to Ameren
Somewhat complicated, but cooperative Register with FERC as QF
– Qualifying Facility– Self-certify – not difficult, just annoying
Submit schematic and specs to Ameren– Pay $100– Their engineer will approve drawings
Sign connection agreement– Can request waivers on insurance, etc.
Sign QF Rider agreement– Pick real-time pricing or normal rates ($333 meter)
Pricing
Smart Power Pricing program– Administered by CNT– $2.25 per month participation– Get wholesale price (Ameren providing wires, this is
fair) Recent legislation allows net metering
– Get the retail price– Eliminate Smart Power Pricing?
The Public Utilities Act is amended by adding 5 Section 16-107.5 as follows…– Ameren to provide free meter… (?)
Sample Billing (9/24-10/23)
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Usage (kWh)
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Price ($/kWh)
PSP Billing (net energy consumed)
Total Energy: 861 kWhTotal Price: $51.37= $0.0596/kWh
This is the energy supply charge. Distribution (“the wires”) costs $0.0245/kWh
Total = $0.084/kWh
$0.71 at noon,10/8
Sample Days
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8-Oct
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Saving $20 to $40 per month compared to flat rate
Generated Power
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Generated power
One Day Example (kW-hr vs. hr)
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Oct 8 Prices
Peaks nearly line up, maximizing the benefit
Note this is netgeneration
On “negative load” generation, effectively get the retail price
Economics
Upfront cost, about $27,000
– $9 per peak watt, installed
Breakdown in cost per watt
– $4.50 for PV modules– $1.00 for inverter– $3.50 for installer labor
and markup
Rebates– $8,100 for IL (took eight
months to receive check)– $2,000 for Federal
Net cost: $16,900
“Investment” Analysis
At $0.10/kWh = $366.90/yr yield Simple payback, a mere 46 years!
This is unfair to PV– (PV held to near impossible standard)
Need to look at – Amortized cost (buying all power upfront)– Equity– Increases in electricity prices (real time price?)– Environmental advantages
More Econ
Realtors estimate $1,000 savings = $20,000 equity– $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
As part of home mortgage– 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
– $55/month savings, $49/month interest– Equity is $13,200, not much less than the $16,900
upfront cost
Other “investments”
A 4% CD would have generated $13,536 in income on $16,900 principle– After taxes, this is ~$10,000 yield
15 years of electric savings lost– 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– This is about $44/month average “luxury” price for
the electricity, or about $0.15/kWh– Gets better with more time
For Comparison
Other things that cost $17,000…– BMW 500 over a Toyota Prius– Extra bedroom– One semester out-of-state tuition at Illinois– Etc.
Conservative?– Rates may go up faster– PV costs will go down– Home interest rates lower
Unconversative?– Repairs, maintenance, other risks
Cost Drivers and Trends
Manufacturing costs for PV modules going down– 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
Source: Evergreen Solar
PV Module Costs
2007 Solar Decathlon
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
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
9th overall 1st in
– Comfort Zone (best passive solar and HVAC design)
– Marketability (very affordable, ordinary building materials, expandable)
Homes limited to 800 sq. ft. Multitude of other limitations and rules
Accepted for 2009 competition
Passive Home Design for 2009
Passive heating and cooling is largely feasible in the Midwest
PassivHaus Institute US (PHIUS) is located in Urbana
– Superinsulated homes (1200 sq. ft.)
– No central air conditioning of furnace
– Earth-tube intake– Southern exposure
adequate for PV – a 1-kW system = zero net energy Source: e-colab.org
Summary
PV taking off but still just off the ground– “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– Insulation, sealing– Compact fluorescent lighting– Better HVAC (geothermal, etc)