EGEE 102 Lesson 5
An old refrigerator consumes 238 W of power. Assuming that the refrigerator operates for 17 hours everyday, what is the annual operating cost of the refrigerator, if the cost of electricity is $0.05 per kWh?
$73.84
Energy factor (EF) =
(1/M) + W M = sum of the machine electrical energy per cycle W = water heating energy consumption per cycle want high
Features of H-axis washer (3)
1. auto temperature 2. water level settings 3. capacity
Many ENERGY STAR qualified models include what 2 features
1. automatic ice maker 2. through-the-door ice dispensor
5 Components to yellow energy guide labels
1. features, capacity, size 2. manufacturer, model number, appliance type 3. estimate of appliance's annual energy use 4. range of energy ratings for similar models 5. estimate of the annual cost to run the model
Clothes washers and dryers account for ____% of residential energy consumption
10
What is the average life expectancy of a water heater?
13 years
What is the average cycles per year of a dishwasher?
215 used to be 264
Each 10 degree F reduction in water heater temp lowers the water heater energy cost by ___ to ___ %
3 to 5
A water heater heats 154 gal of water from 54 to 122 degrees every day. What is the annual energy requirement of the water heater?
31724924 Btus
Household appliances, cooking, and lighting consumer _____% of the energy at home
33
What is the modified energy factor equation?
= ft^3/KWh/Cycle (capacity/(machine energy comsumption + hot water energy consumption + energy for removal of moisture)
126 gal of water is heated from 57 to 128 degrees everyday by a family. What is the annual energy requirement of the water heater? A) 27101907 Btus B) 8946 Btus C) 74251.8 Btus D) 3265290 Btus
A
155 gal of water is heated in a heater form 63 to 123 degrees everyday by a family. What is the annual energy requirement of the water heater? A) 28174350 B) 77190
A
Calculate the amount of heat energy required to heat 177 lbs of water from 67 to 136 degrees A) 12213 Btus B) 35931 Btus C) 24072 Btus D) 69 Btus
A
Placing your clothes dryer in a cold basement will make the dryer _______. A) less efficient B) more efficient C) work smoothly
A
Thermosiphon systems are most efficient in areas with ___________ levels of solar radiation. A) high B) moderate C) low
A
What does the acronym DOE stand for? A) department of energy B) division of energy C) development of energy D) disasters of energy
A
What kind of washer is most efficient? A) front loading B) side loading C) top loading D) bottom loading
A
the energy guide label must specify the _______ of the particular model A) estimated annual energy consumption B) price C) voltage
A
All major home appliances must meet the :
Appliance Standards Program set by the US Department of Energy
112 gal of water is heated in a heater from 55 to 136 degrees everyday by a family. What is the annual energy requirement of the water heater? A) 75297.6 Btus B) 27483624 Btus C) 9072 Btus D) 3311280 Btus
B
What kind of label do highly energy efficient appliances have? A) energy guide label B) energy star label C) energy efficient lael
B
Buying an expensive energy efficient water heater will most likely save ______ in the long-term A) energy B) money C) both energy and money D) neither
C
Which of the following is the most efficient for heating water? A) on-demand water heater B) storage type water heater C) heat pump
C
refrigerators are heat _____. A) valves B) generators C) movers D) engines
C
which of the following actions is not likely to improve the efficiency of a refrigerator? A) cleaning the coils in the back of the fridge B) checking the seals using the "dollar bill test" C) switching the motor from a DC motor to a more efficient AC motos D) keeping the freezer to its capacity
C
A family of four, each showering for five minutes a day, uses 700 gallons of water every week. Installing a low-flow non-aerating showerhead can cut this consumption by how much? A) 0.1 B) 0.2 C) 0.3 D) 0.5
D
Water heaters are typically set to ________. A) 150 degrees B) 180 degrees C) 90 degrees D) 120 degrees
D
What steps can lead to an energy efficient operation of a dishwasher? A) wash only full loads B) use the no-heat air dry feature C) don't pre-rinse dishes before putting them in the dishwasher D) all of the above E) none of the above
D
calculate the amount of energy required to heat 159 lbs of water from 52 to 138 degrees. A) 86 Btus B) 21942 Btus C) 30210 Btus D) 13674 Btus
D
What appliance requires the hottest water?
Dishwashers
How are efficiencies of clothes washers measured?
Energy factor = 392 * Volume (ft^3)/annual energy use (kWh) want high
What is a downfall of storage tank type water heaters?
STANDBY HEAT LOSS: The water is constantly heated so heat energy can be lost even when no faucet is on 10-20% of household's annual water heating costs
T/F: keep a freezer filled to capacity for most efficient operation
T
T/F: Frost build up reduces the efficiency of freezers
True
How does a gas hot water heater work?
When hot water faucet turned on, water pipes draw hot water from the tank. Cold water then enters the bottom of the tank to replace the hot water so the tank is always full. The water is heated by either electrical heating elements or a natural gas burner
What is the expansion valve of a refrigerator?
a liquid refrigerant at high pressure flows through this and moves from a high pressure zone to a low pressure zone decrease in pressure corresponds with decrease in temp
What is the condenser or second heat exchanger coil of a refrigerator?
at back of fridge gives off heat to air of kitchen
Other than a high EF, what else should one look for in a water heater?
at least 1.5 inches of tank insulation and heat trap capacity
Heat is ________ flowing from the tank of the water heater and the pipes to the room
continuously
What is the EF ratio?
efficiency ratio of energy supplied in heated water divided by energy input to the water heater
Electric vs gas Dryer
electric: electrical energy used for both the motor to rotate the drum and heat the air gas: gas used to heat air
What is a heat pump water heater?
extract heat from air and deliver it to water simplest model = ambient air-source unit (removes heat from surrounding air aka cools the space as well)
T/F: On-demand water heaters have a storage tank
false
T/F: natural gas water heaters are cheaper to install than electric water heaters
false
T/F: insulating the cold water pipes will save a lot of energy
false ; hot water pipes
How does indirect water-heating systems work?
freeze-protected fluid is circulated through a closed loop and heat is transferred to potable water through a heat exchanger
How does thermal energy flow?
from high temp to low temp
How should one decide on which water heater to buy?
get an energy-efficient one and spend less money each month to get same amount of hot water
Refrigerators are _______ movers, which move heat from a ______ temp (inside the fridge) to a ____ temp (outside the fridge into the kitchen)
heat, low, high
How does a Thermosiphon system work?
heats water or an antifreeze fluid fluid rises by natural convection from collectors to the storage tank no pumps fluid movement increases with temperature so most efficient in areas with high levels of solar radiation
Do u want a high or low EF ratio?
high
water heaters are always at a (higher/lower) temp than the surroundings
higher
Which version of a washer is most efficient?
horizontal axis
Downfall of demand water heater?
hot water cannot be needed in more than one location at a time
How do dishwashers work?
hot water is spray on to the dishes as jets dirty water passes through a filter and re-circulated until dishes are finished fresh water is sprayed during the rinse cycle to remove the soapy water
How do clothes dryers dry wet clothes?
in a rotating drum through which hot air is circulated heating and aerating clothes
How is water heater efficiency reported?
in terms of the energy factor
Which water heating systems are most appropriate in the US?
indirect air and water systems
How does air systems work?
indirect system collectors heat the air which is moved by a fan through an air-to-water heat exchanger
How does a drain-down system work?
indirect water-heating systems treated or untreated water is circulated through a closed loop, and heat is transferred to potable water through a water exchanger no solar hear = collector fluid drained to avoid freezing and convection loops reduce the temp of stored water
Heat equation: what does each symbol mean? (m, Cp, (T2-T1)
m = mass of water heated Cp = heat capacity of water (usually 1) (T2-T1) = change in temperature
What is a demand water heater?
no storage tank = no standby heat loss water heated only when needed you can never run out of hot water
What is the water factor?
number of gallons per cycle per cubic foot want low (# of gal / tub volume)
What is the compressor of a refrigerator?
pressurizes the warm refrigerant and makes it hot then goes into condensor
What is a desuperheater feature?
provides economical supplemental water heating as a byproduct of air conditioning
How does a direct-circulation system work?
pump water from storage to collectors during sunny hours freeze protection obtained by recirculating hot water from storage tank or by flushing the collectors used only in areas where freezing temps are infrequent
Any reduction in energy consumption for clothes washing application would involve:
reduction in hot water use
What is the evaporator or heat exchanging piped of a refrigerator?
set of coiled tubes carrying the low pressure, expanded refrigerant in evaporator: refrigerant expands and evaporates evaporation takes away heat cold refrigerant flows through coils absorbing heat
Most heaters use a ______________ type
storage tank
How do solar water-heating systems get sunlight?
sunlight strikes and heats an "absorber" surface within a "solar collector"
How is the efficiency of a clothes dryer measured?
the energy factor
How is most energy used by a refridgerator?
to pump heat out of the cabinet
T/F: horizontal axis (front loading) washing machines are more efficient compared to top loading models
true
T/F: leaking faucets can increase your energy costs
true
T/F: solar water heating systems reduce the amount of heat that must be provided by conventional energy sources such as electricity
true
ENERGY STAR models qualification
use at least 15% less energy than required by current federal standards and 40% less than the conventional models sold in 2001
What is the method of agitation?
using heated water gets out a lot more dirt
How is the efficiency of a refrigerator expressed?
volume cooled per unit electric energy per day = Volume cooled (ft^3)/Unit electrical energy per day (kWh)
What is the second largest energy expense after home heating and cooling?
water heating
