a) Find the energy savings per year (kWhr/yr) that would result from using 10 ga
ID: 2079233 • Letter: A
Question
a) Find the energy savings per year (kWhr/yr) that would result from using
10 ga instead of 12 ga wire.
b) Suppose 12 ga wire costs $25 per 100 ft of “Romex” (2 conductors, each
100-ft long, plus a ground wire in a tough insulating sheath) and 10 ga
costs $35 per 100 ft. What would be the “simple payback” period (simple
payback = extra 1st cost/annual $ savings) when utility electricity
costs $0.10/kWh?
c) An effective way to evaluate energy efficiency projects is by calculating
the annual cost associated with conservation and dividing it by the
48 BASIC ELECTRIC AND MAGNETIC CIRCUITS
annual energy saved. This is the cost of conserved energy CCE = annual cost of saved electricity($/yr)/annual electricity saved (kWhr/yr)
= P · CRF(i, n) / ( kWhr/yr )
where P is the extra cost of the conservation feature (heavier duty
wire in this case), and CRF is the capital recovery factor (which means
your annual loan payment on $1 borrowed for n years at interest rate i.
What would be the “cost of conserved energy” CCE (cents/kWhr) if
the building (and wiring) is being paid for with a 7-%, 20-yr loan with
CRF = 0.0944/yr. How does that compare with the cost of electricity
that you don’t have to purchase from the utility at 10¢ /kWhr?
Explanation / Answer
a) To understand the part of total energy saved by using 10mm gauge wire we must look into the resistance both the wires have to offer as we can observe from the table provided the the resitsnce value in ohs per 100 ft2 value of 12 mm gauge is 0.1588 where as value for 10 mm gauge is 0.0999, so by calculating the power which is flowing through them we can claculate the energy that is wasted through resistance. Now Power=Current2 X Resistance, by using this formula we get to know that using 10mm gauge wire we will consume 39.6 watt power and using 12 mm gauge wire we will consume 63.52 watt power. Now lights are on 2500 hrs a year, multiplying both resistance to the given value we get total energy saving by 10mm gauge=99Kwatthr/year and 12mm Gauge=158.8Kwatthr/year. and as per given question electricity rate is $0.10 per Kwh. We get 10mm gauge=99 X0.10= $9.9 and for 12mm gauge=$15.88, thus total saving by using 10 gauge wire is= 15.88-9.9 =$5.98. This implies we save $5.98/Kwhr by using10mm gauge wire.
(b) Now we know that we are saving $5.98 is saved per year by using 10 mm gauge wire. now taking into consideration the taotal cost both 10 mm gauge wire and 12 mm gauge wire impliments onto the system. 10mm gauge wire costs $35 whereas 12 mm gauge wire costs $25, so total extra cost that we incure by using 10 mm geuge wire is $10. We save $5.98 per year by using 10 mm gauge wire thus monthly saving will be $0.4983 so simple payback will be
Simple payback=10/5.98=1.6722 and simple payback period will be 1 year and 9 monts.
(C) Now as per the given formula and the data we have calculated periously in the given question lets us calculate CCE(Cost of Calculated Energy). Varialbes for the same will be
P=10
CRF=0.0944/yr
i=7%
n=20
CCE= 10 X 0.0944(7X20)/99 = $1.335/Kwhr when cost of electricity is $0.10
Now comparing this to amout of electricity that we dont have to purchase subtracting power consumption by using 10mm gauge wire instead of 12mm gauge wire, as previously we have calculated we save
158.8-99= 59.8Kwatt/year at cost of $0.10
So, total cost saving per year is =59.8 X 0.10 =$5.98.
If we comapre the data we get form above we will understand the importance of CEC as this method takes into the consideration of the CRF (Capital Recovery Factor) and thus provide you the exact amount of saving one can get by using the energy saving methods, by going to the amount of money saved by using energy efficent system we will look into only one side of the picture and will not take into consideration the cost we have incurred for applying the system.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.