February 4, 2008

Residential Solar Power in Midwest

Patrick Chapman

Associate Professor

University of Illinois at

Urbana-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

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)

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

Photos Case Study

Initial work

More Photos

Racking

More Photos

Modules

More Photos (Inverter and Monitor)

Inverter and Monitor

Finished Project

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)

Example Schematic

Real-Time Pricing

Price peaks more/less with sun

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)

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

Saving $20 to $40 per month compared to flat rate

Generated Power

-133 kWh

One Day Example (kW-hr vs. hr)

Peaks nearly line up, maximizing the benefit

Note this is net generation

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

Final Illinois House on the Mall

($450k)

Source: SD07 photos from solardecathlon.org

Winning Overall House

Darmstadt ($2M)

Other Remarkable Houses

Georgia Tech, Missouri-Rolla

Other Remarkable Houses, cont’d

Santa Clara, Lawrence Tech

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)