Sustainable Energy
Homework #5
Solar Energy
1.
From the Wind Energy Homework, Colorado will need 58,668,653 MWh of electricity generation in
2010. How many square kilometers of solar photovoltaic panels would be required to meet that
demand if Colorado switched completely to solar photovoltaic generation?
Assume:
a. 5.5 kWh/m2/day (40o tilt fixed array)
b. 17% efficiency
c. 77% derate factor
Hint: Be careful that you use the correct factors when converting MWh/year to kWh/day and m2 to km2
Answer: (58,668,653 MWh/year x 1,000 kWh/MWh x 1/365 years/day) = 160,736,036 kWh/day
160,736,036 kWh/day/( 5.5 kWh/m2/day x 0.17 x 0.77) = 223,259,999 m2
223,259,999 m2 x 1/1,000,000 km/m2 = 223.3 km2
2.
How many AC kWh/year can a photovoltaic system generate in Boulder using 20 Sanyo HIP-200 solar
modules?. Details on the Sanyo HIP-200 solar panel can be found at
http://www.sanyo.com/industrial/solar/index.cfm?productID=1232
Assume:
a. 5.5 kWh/m2/day (40o tilt fixed array)
b. Use the Sanyo HIP-200 module efficiency
c. 0.77 derate factor
Hint: First find how many m2 of solar panels there are in 20 Sanyo HIP-200 modules
Answer: 20 panels x 1.319 meters x 0.894 meters = 23.58 m2
23.58 m2 x 5.5 kWh/m2/day x 0.17 x 0.77 = 16.98 kWh/day
16.98 kWh/day x 365 days/year = 6198 kWh/year
3.
Using the cost/kWh, rebate/kWh and tax credit values discussed in class, what is the initial cost of this
system after all rebates and credits?
Answer: 4000 watts x $8/watt = $32,000
Rebate = 4000 watts x $4.50/watt = $18,000
Federal Tax Credit = 0.30 x ($32,000 - $18,000) = $4,200 – However maximum is $2,000
Initial Cost = $32,000 - $18,000 - $2,000 = $12,000
4.
Design a solar photovoltaic system for a home in Boulder that uses, on average, 8400 AC kWh/year.
You want a system that is large enough to meet the annual needs of the home. Determine how big a
system is needed, the total initial cost before rebates and incentives, the net initial cost after rebates and
incentives and the simple payback in years.
Assume:
a. 5.5 kWh/m2/day (40o tilt fixed array)
b. Use the Sanyo HIP-200 module efficiency
c. 77% derate factor
d. $0.09/kWh average cost of energy from Xcel
Sustainable Energy
Hint: Along the way you’ll need to determine out how many m2 of solar modules you’ll need, then
determine how many full modules you’ll need (you can’t use a fraction of a module)
Answer: 8400 AC kWh/year x 1/365 years/day = 23.01 AC kWh/day
23.01 kWh/day / (0.17 x 0.77) = 175.78 DC kWh/day
175.78 DC kWh/Day /5.5 kWh/m2/day = 31.96 m2
31.96 m2 / (1.319 m x 0.894 m) = 27.1 Sanyo HIP-200 modules
Need to round to up 28 modules
Initial Cost Before Rebates/Credits = 28 panels x 200 watts/panel x $8/watt = $44,800
Xcel rebate = 28 panels x 200 watts/panel x $4.50/watt = $25,200
Federal Tax Credit = ($44,800 - $25,200) x 0.30 = $5,880 – However maximum is $2,000
Initial Cost After Rebates/Credits = $44,800 - $25,200 - $2,000 = $17,600
Simple Payback = $17,600/($0.09 x 8400) = 23.3 years
5.
Argue the positives and negatives of Amendment 37’s solar provisions. Should all Xcel ratepayers
(e.g. renters, homeowners, the poor, the middle class, the wealthy) pay $6.00/year for the next 10 years
to fund rebates for solar photovoltaic buyers? Argue your position with vigor as if you were debating
the subject on national television.
6.
In 2001, when California increased their rebates by $1.50/watt, photovoltaic retailers captured 50% of
that increase by increasing prices $0.75/watt. Argue the ethics of a business raising prices to partially
capture a government incentive. Is this practice right? Is it the free market in action?