Question

g Replacing incandescent lights with energy-efficient fluorescent lights can reduce the lighting energy consumption to one-fourth of what it was before. The energy consumed by the lamps is eventually converted to heat, and thus switching to energy-efficient lighting also reduces the cooling load in summer but increases the heating load in winter. Consider a building that is heated by a natural gas furnace with an efficiency of 80 percent and cooled by an air conditioner with a COP of 3.5. The electricity costs $0.12/kWh and natural gas costs $1.40/therm (1 therm = 105,500 kJ).

Answer 1

Answer:

For a 1 kWh, heat supplied for the cost of furnace is = $1.66 *1 0^-5 /kJ * 3600 =$0.06/kWh.

Therefore, supplied heat for natural gas furnace is $0.06/kWh which is lower than $0.12/kWh cost of electricity of refrigerator.

Explanation:

Solution

Given that:

The thermal efficiency of furnace = 0.8 or 80%

The cop of refrigerant COP = 3.5

The unit cost of electricity for refrigerant is =$ 0.12kWh

The unit cost of natural gas of furnace is = $1.40/therm

1 therm = 105,500 kJ

Now,

In the summer the usage or utilization of lightening in the house will be lesser than winter, hence the total cost of energy used in the household will be decreased.

Thus,

In winter, the utilization of lightening will be higher with regards to electricity

For a natural gas furnace it is given below:

The unit cost =$1.40/ηth (I therm/105,500)

= 1.40/0.8 (I therm/105,500)

= $1.66 *1 0^-5 /kJ

For a 1 kWh, heat supplied for the cost of furnace is = $1.66 *1 0^-5 /kJ * 3600 =$0.06/kWh.

So,for the heat supplied for natural gas furnace is $0.06/kWh which is less er than $0.12/kWh cost of electricity of refrigerator.

Therefore, the efficiency of energy lightning will reduce the total energy cost of the building both in winter and summer.