Page 148 - Solar Power in Building Design The Engineer's Complete Design Resource

118 SOLAR POWER GENERATION PROJECT IMPLEMENTATION

Prior to designing the solar power system, the designer must calculate the residen-
tial power consumption demand load. Electrical power-consuming items in a house-
hold must be calculated according to the NEC-recommended procedure outlined in
2
the following steps. The calculation is based on a 2000-ft conventional single resi-
dential unit:

Step 1: Lighting load. Multiply the living space square area by 3 W: 2000 × 3 =
6000 W.

Step 2: Laundry load. Multiply 1500 W for each laundry appliance set, which con-
sists of a clothes washer and dryer: 1500 × 1 = 1500 W.

Step 3: Small appliance load. Multiply kitchen appliance loads rated 1500 W by 2:
1500 W × 2 = 3000 W.

Step 4: Total lighting load. Total the sum of the loads calculated in steps 1 to 3: 6000 +
1500 + 3000 + 10,500 W.

Step 5: Lighting load derating. Use the first 3000 W of the summed-up load (step 4)
and add 35 percent of the balance to it: 3000 + 2625 + 5625 W.

Step 6: Appliance loads. Assign the following load values (in watts) to kitchen
appliances:

Dishwasher 1200

Microwave oven 1200
Refrigerator 1000
Kitchen hood 400

Sink garbage disposer 800
Total kitchen appliance load 4600
If the number of appliances equals 5 or more, then the total load must be multiplied
by 75 percent, which in this case is 3450 W.

Step 7: Miscellaneous loads. Loads that are not subject to power discounts in-
clude air conditioning, Jacuzzi, pool, and sauna and must be totaled as per the
equipment nameplate power ratings. In this example we will assume that the res-
idence is equipped with a single five-tone packaged air-conditioning system rated
at 17,000 W.

When totaling the load, the total energy consumption is 26,075 W:

17,000 (air conditioner) + 3450 (appliances) + 5625 (lighting power) = 26,075