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Case Study 2 :
hotel
Quick Data:
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Electric usage:
30,000 kWh/month
Suggested system size:
72.6 kW
DC
Project Grand Total Cost:
$442,968.19
Equipment
total cost: $391,656
Additional structures:
None
Utility Plan:
PG&E E16
(avg 14 cents/kWh)
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Description:
This branch of a well-known hotel chain is located in
the Peninsula near SFO airport. It is three stories high, and has a
nice wide flat roof. Hotels always have a lot of electricity usage
(customers generally don't pay attention to energy savings as they would
at their homes), especially in summer time when the air-conditioners are
on.
The E16 plan for this hotel is set up such that the
demand charge is about 25% of the kWh usage charge. A solar system
would also make it possible to switch to an A6 plan and significantly reduce the demand charge that would result from
the air-conditioning kicking off in the late morning.
The building is from cement and very sturdy.
Its roof could handle several trucks parked on it. Thus, a
non-penetrating system would not be an issue. We designed a system
with Sunlink ballasted system. The Sunlink system is composed of
frames each holding one panel. The frames are held in place by
pavers with a system average weight of 5 lbs/sqft.
The panels are alligned parallel to the walls of the
building. The building is facing SouthWest, which is an optimal
direction for TOU. The surrounding of the building is pretty open,
except for a tall building 0.7 miles away in the South, and a mountain 4
miles on the West. It can be considered with 95% open.
The Sunlink system allignment is as follows:
We also did a wiring diagram for this design. This
is required for the City Permit as well as for the optimal selection of
the inverters:
The above picture shows how many series and how many
parallel groups there are. As a result, there are 11 series of 12
panels and 28 series of 11 panels. It is important that the series
are clustered with the same numbers. That is to say, 12s are grouped
together and 11s are grouped together, so that each cluster will have a
specific voltage.
It is also important to decide on the locations of the
junction boxes. This is done with an MC-cable diagram:
This diagram tells us what sizes of MC-cables we will
need, so that we will order the optimum lengths and save money.
The following cable diagram is to determine what total length of
cable we will be using. The customer will be charged on this optimal
length of cable and nothing will go to waste.
Below is a clearer picture of the cable diagram:
After all these calculations, we obtain the following
quote with all the necessary parts:
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Sale Item Part No. |
Description |
Qty |
Unit Price |
Ext. Price |
|
TDB125x125-72-P 165W |
Sun-Earth (Ningbo) Monocrstalline Solar Panels 165W PTC 145.3 |
440 |
643.50 |
283,140.00 |
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SB7000US |
SMA SunnyBoy 7000 Inverter w/ AC/DC Disconnect |
2 |
3,400.00 |
6,800.00 |
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SB6000US |
SMA SunnyBoy 6000 Inverter w/ AC/DC Disconnect |
7 |
3,200.00 |
22,400.00 |
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SB5000US |
SMA SunnyBoy 5000 Inverter w/ AC/DC Disconnect |
1 |
3,000.00 |
3,000.00 |
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SC1090ML-A |
7.5' Cable w/ male MC connector |
7 |
8.25 |
57.75 |
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SC10156ML-A |
13' Cable w/ male MC connector |
10 |
9.50 |
95.00 |
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SC10192ML-A |
16' Cable w/ male MC connector |
10 |
11.00 |
110.00 |
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SC10264ML-A |
22' Cable w/ male MC connector |
8 |
15.06 |
120.48 |
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SC10360ML-A |
30' Cable w/ male MC connector |
4 |
18.95 |
75.80 |
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SC1090FL-A |
7.5' Cable w/ female MC connector |
2 |
8.50 |
17.00 |
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SC10156FL-A |
13' Cable w/ female MC connector |
8 |
11.50 |
92.00 |
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SC10192FL-A |
16' Cable w/ female MC connector |
12 |
16.75 |
201.00 |
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SC10264FL-A |
22' Cable w/ female MC connector |
12 |
19.50 |
234.00 |
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SC10360FL-A |
30' Cable w/ female MC connector |
1 |
21.40 |
21.40 |
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SC10540FL-A |
45' Cable w/ female MC connector |
3 |
35.60 |
106.80 |
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SC10768FL-A |
64' Cable w/ female MC connector |
1 |
47.30 |
47.30 |
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THWN2-6-500-G |
THWN-2 cable 500' roll, AWG 6, Green |
6 |
650.00 |
3,900.00 |
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THWN2-6-500-R |
THWN-2 cable 500' roll, AWG 6, Red |
6 |
650.00 |
3,900.00 |
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THWN2-8-500-W |
THWN-2 cable 500' roll, AWG 8, White |
2 |
180.00 |
360.00 |
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DC-Disco0102 |
DC Disconnect Switch, 3 poles, fused |
8 |
89.00 |
712.00 |
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JB-20001 |
Water proof junction box 4" x 4 " |
28 |
5.50 |
154.00 |
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SL2-440-R3-2007 |
Sunlink ballasted, 440 panel system |
1 |
62,920.00 |
62,920.00 |
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SL-BP-1001 |
Each 24 lbs 12"x12" pavers for pans |
1064 |
3.00 |
3,192.00 |
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Sub Total |
Equipment sub-total |
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391,656.53 |
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Tax |
8.25% tax Menlo Park, CA |
1 |
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32,311.66 |
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Shipping |
Shipping of all items to installation site |
1 |
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4,000.00 |
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Installation |
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1 |
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15,000.00 |
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Total |
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442,968.19 |
Detailed Data:
System Power Output (CEC AC): 114,497 kWh per year
Cumulative System Savings on Utility (with 5% annual electricity inflation):
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Year |
Cumulative Savings ($) |
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1 |
17,205 |
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2 |
35,271 |
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3 |
54,240 |
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4 |
74,157 |
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5 |
95,071 |
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6 |
117,030 |
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7 |
140,087 |
|
8 |
164,296 |
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9 |
189,717 |
Incentives:
Federal Tax Credit: $126,890.46
Cumulative PBI Gains (PBI @ $0.26/kWh):
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Year |
Cumulative PBI Gains ($) |
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1 |
29,769.00 |
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2 |
59,538.00 |
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3 |
89,307.00 |
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4 |
119,076.00 |
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5 |
148,845.00 |
Five Years Advance Depreciation (MACRS): 110,207.79
The power output was calculated with an hourly irradiance database,
which could be viewed
here.
Results:
According to this
calculation, the system would pay itself back in 3 years.
The incentives pay 89% of
the grand total cost:
$442,968.19 - 126,890.46 -
110,207.79 - 154,801.00 = 51,068.94
The rest is paid off in no
time as seen from the Cumulative Savings table above.
Clearly, solar in
current conditions is a great investment!
If you have any questions
regarding this study, please do not hesitate to contact us.
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