Question 9.14: A Modest Household Demand. Estimate the monthly energy deman......

Renewable and Efficient Electric Power Systems [1073600]

A Modest Household Demand. Estimate the monthly energy demand for a cabin with all ac appliances, consisting of a 19-cu. ft refrigerator, six 30-W compact fluorescents (CFLs) used 5 h/day, a 19-in. TV turned on 3 h/day and connected to a satellite, a cordless phone, a 1000-W microwave used 6 min/day, and a 100-ft deep well that supplies 120 gallons/day.

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Using data from Table 9.10, we can put together the following table of power and energy demands. The total is just over 3.11 kWh/day.
Notice how little of the energy for TV/satellite is used during the 3 h that it is actually turned on (255 Wh out of a total of 698 Wh, or 36.5%). This household really needs to provide a power strip to allow manual complete shut off of these electricity vampires.

Appliance	Power (W)	Hours	Watt-hours/day	Percentage
Refrigerator, 19 cu. ft	300		1140	37%
Lights (6 @ 30 W)	180	5	900	29%
TV, 19-in., active mode	68	3	204	7%
TV, 19-in., standby mode	5.1	21	107	3%
Satellite, active mode	17	3	51	2%
Satellite, standby mode	16	21	336	11%
Cordless phone	4	24	96	3%
Microwave	1000	0.1	100	3%
Washing machine	250	0.2	50	2%
Well pump, 100 ft, 1.6 gpm	100	1.25	125	4%
Total			3109	100%

TABLE 9.10 Power Requirements of Typical Loads
Kitchen Appliances		Power
Refrigerator: ac EnergyStar, 14 cu. ft		300 W, 1080 Wh/day
Refrigerator: ac EnergyStar, 19 cu. ft		300 W, 1140 Wh/day
Refrigerator: ac EnergyStar, 22 cu. ft		300 W, 1250 Wh/day
Refrigerator: dc Sun Frost, 12 cu. ft		58 W, 560 Wh/day
Freezer: ac 7.5 cu. ft		300 W, 540 Wh/day
Freezer: dc Sun Frost, 10 cu. ft		88 W, 880 Wh/day
Electric range (small burner)		1250 W
Electric range (large burner)		2100 W
Dishwasher: cool dry		700 W
Dishwasher: hot dry		1450 W
Microwave oven		750–1100 W
Coffeemaker (brewing)		1200 W
Coffeemaker (warming)		600 W
Toaster		800–1400 W
General Household
Clothes washer: vertical axis		500 W
Clothes washer: horizontal axis		250 W
Dryer (gas)		500 W
Vacuum cleaner		1000–1400 W
Furnace fan: 1/4 hp		600 W
Furnace fan: 1/3 hp		700 W
Furnace fan: 1/2 hp		875 W
Ceiling fan		65–175 W
Whole house fan		240–750 W
Air conditioner: window, 10,000 Btu		1200 W
Heater (portable)		1200–1875 W
Compact fluorescent lamp (100-W equivalent)		30 W
Compact fluorescent lamp (60-W equivalent)		16 W
Electric blanket, single/double		60/100 W
Clothes iron		1000–1800 W
Electric clock		4 W
Consumer Electronics
TV: >39-in. (active/standby)		142/3.5 W
TV: 25 to 27-in. color (active/standby)		90/4.9 W
TV: 19 to 20-in. color (active/standby)		68/5.1 W
Analog cable box (active/standby)		12/11 W
Satellite receiver (active/standby)		17/16 W
VCR (active/standby)		17/5.9 W
Component stereo (active/standby)		44/3 W
Compact stereo (active/standby)		22/9.8 W
Cordless phone		4 W
Clock radio (active/standby)		2.0/1.7 W
Computer, desktop (active/idle/standby)		125/80/2.2 W
Laptop computer		20 W
Ink-jet printer		35 W
Dot-matrix printer		200 W
Laser printer		900 W
Shop
Circular saw, 7 ${1}/{4^{\prime \prime}}$		900 W
Table saw, 10-in.		1800 W
Hand drill, ${1}/{4^{\prime \prime}}$		250 W
Water Pumping
Centrifugal pump: 36 Vdc, 50-ft @ 10 gpm		450 W
Submersible pump: 24 Vdc, 100-ft @ 1.6 gpm		100 W
Submersible pump: 48 Vdc, 300-ft @ 1.5 gpm		180 W
DC pump (house pressure system), typical use 1–2 h/day		60 W
Source: Rosen and Meier (2000) and others.