Question

1. Considering the following data for fluorescent and incandescent bulbs to answer the following questions:

	Fluorescent bulb	Incandescent bulb
Light output (lumens)	985	1000
Life (hours)	10,000	3,000
Energy Use Rate (watt)	13	100
Purchase cost ($/bulb)	3.75	1.55
Energy costs ($/kW-h)	0.12	0.12
Disposal/Recycle cost ($/bulb)	0.98	0.05

Data from several source: Amazon.

1. Estimate the 2018 energy savings potential on a national scale of replacing all incandescent bulbs in home (residential) with the new energy efficient fluorescent bulbs. Consider that in 2018, total US energy consumption was 101.3 quadrillion British thermal units (Btu). Electricity consumption for all applications amounts for 13 quads, and residential is 11.9% of all electricity consumption in US. Assume that all energy consumption for residential lightning is due to incandescent bulbs and that all those are replaced by fluorescent bulbs. How large are energy savings compared to annual US energy and electricity consumption? State your answer on a percentage basis.

(8 points)

2. From a LCA perspective, define a functional unit and equivalence for this comparison of fluorescent and incandescent bulbs. How many incandescent bulbs are needed to equal one fluorescent bulb? Comment your results. (4 points)
3. Develop an inventory of costs over the life cycle for each bulb type. Compare cost over the life cycle for fluorescent bulbs vs. incandescent bulbs. Which stage of the life cycle accounts for the greatest cost to the consumer? (8 points)

(Total: 20 points)

4. NOTE: be careful with unit conversion, purposely the information comes in a mix of units.

Answer 1

(b) A functional unit would be the lumen as the light output should be the same no matter what bulbs we use. One fluorescent bulb gives 985 lumens while one incandescent bulb gives 1000 lumens so, one flurescent bulb is equivalent to 985/1000 = 0.985 incandescent bulbs. That is, 0.985 incandescent bulbs are required to equal one flurescent bulb. This is expected as the light output of a fluorescent bulb is slightly less than that of an incandescent bulb.

(c)

We see that the energy consumption stage (use stage of the bulbs) of the life cycle accounts for the greatest cost to consumer.