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Case Study 1 :
injection molding facility
Quick Data:
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Electric usage:
80,000 kWh/month
Suggested system size:
63.3 kW DC
Project Grand Total Cost:
$350,413
Equipment total
cost:
$271,514
Additional structures:
Steel Building
(+ $47,000.00)
Utility Plan:
PG&E A6
(avg 16 cents/kWh '07)
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Description:
This is a medium-sized injection molding facility in the
East Bay area. The facility building is about 30,000 sqft.
However, the condition of the roof, which had been there for 45
years without renovations, did not allow the 5 lbs/sqft pressure exerted
by a non-penetrating ballasted system, while a penetrating system would
also be too much for the roof.
Meanwhile the management of the company wanted to cover
the empty yard at the back of the building. The yard is 20,000 sqft,
but the city only allowed maximum 5,000 sqft to be covered. Thus, a
5000 sqft Steel Building was designed to accomodate the solar panels.
This building would be included in the cost of the solar system and would
be exempt from Property Tax!
The system is to be paid for with a loan at 7%
interest rate and 25 year term.
Detailed Data:
Brand (and number) of panels:
Mitsubishi 170W
(361)
Brand (and number) of inverters:
Sunny Boy 6000US
(9)
Brand of mounting hardware:
ProSolar Fastjack
Annual Electricity Production
per year:
90,428 kWh
PBI Rate:
0.26 ($/kWh)
as of jan. 2008
PBI monitoring fee:
$1,500
for 5 years
Loan amount / term / rate / monthly payment:
$350k /
25 years / 7% / $2,473
Electricity Annual Inflation Rate:
5%
Module degredation
per year:
0.5%
The Power Output:
It could be seen that the power output of the solar
system is way less than the electricity consumption of the facility.
However, the percentage of savings on the utility bill is more than the
percentage of electricity generated from solar. This is the merit of
the type of application called Grid Tied System. The facility will
continue to use PG&E electricity, but the system will supply electricity
back to the grid, which by California Law has to be purchased back by
PG&E. Since the rates are higher during the day when a solar system
generates power, the electricity will be purchased at lower rate from and
sold at higher rate to PG&E.
The power output of
the system was calculated by hour by hour irradiance data obtained from a
special website for the latitude 37:35 N and elevation 35 ft. The
data is quite huge! It could be viewed in the file attached by
clicking here.
It is important to have hourly data, because the utility companies charge
according to the time of the day. Assumptions like 5 hours of
insolation per day, a calculation used by most installers, would lead to
very wrong calculations.
The data may not exactly correlate with the EPBB calculation, so an
irradiance bias factor is used.
Irradiance Bias Factor: 0.90
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The
Results:
Below graph summarizes the annual savings:
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Every detail has been taken into accoount in this analysis, even the
deduction of the interest portion of the monthly loan payment.
The most important column is the 'Cumulative' column, which shows the
total money at hand. As you can see, with a 25 year loan, at the
end of the first year there is a free $100,000 working capital.
At the end of 5 years this becomes $200,000.
Below graph shows the trend of the Annual Cumulative Savings:
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If you have any questions regarding this study, please do not hesitate
to contact us. |
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