Products
Rewards 
from HOLOOLY

We are determined to provide the latest solutions related to all subjects FREE of charge!

Please sign up to our reward program to support us in return and take advantage of the incredible listed offers.

Enjoy Limited offers, deals & Discounts by signing up to Holooly Rewards Program

HOLOOLY 
BUSINESS MANAGER

Advertise your business, and reach millions of students around the world.

HOLOOLY 
TABLES

All the data tables that you may search for.

HOLOOLY 
ARABIA

For Arabic Users, find a teacher/tutor in your City or country in the Middle East.

HOLOOLY 
TEXTBOOKS

Find the Source, Textbook, Solution Manual that you are looking for in 1 click.

HOLOOLY 
HELP DESK

Need Help? We got you covered.

Chapter 13

Q. 13.3

Provide a simple payback period analysis for implementing a cogeneration system to be installed in a hospital. Use the following characteristics for the cogeneration system:
• Fuel input rate: 10,000 Btu/kWh
• Heat recovery rate: 5,500 Btu/kWh
• Maintenance cost: $0.02/ kWh
• Maximum electrical output: 200 kW or 300 kW
• Installed equipment cost: $1000/kW
Table 13.10 summarizes the energy usage and cost of the hospital. Assume that the boiler(s) efficiency is 70 percent. For this analysis, assume also that the cogeneration system requires diesel fuel only (the other option is dual fuel). Assume the heating value of diesel fuel is 140,000 Btu/ gal.

TABLE 13.10 Monthly Utility Data for the Hospital Used in Example 13.3

Utility Summary
Fuel Oil Electricity
($) (Gallon) ($) (kW) (kWh) Month
14,911 20,659 2,7020 546 226,400 January
12,639 20,555 28,949 572 273,600 February
9,670 16,713 31,048 564 280,800 March
4,742 10,235 25,251 526 228,000 April
5,347 12,193 28,755 692 246,000 May
9,001 12,352 36,604 884 301,200 June
3,122 20,604 45,031 1,040 346,800 July
5,711 17,276 46,374 944 403,200 August
3,762 10,457 36,541 860 303,600 September
3,726 10,890 33,559 872 276,000 October
5,255 13,478 28,042 662 272,400 November
7,808 17,661 25,041 524 276,000 December
85,694 183,073 393,215 3,434,000 Total

Step-by-Step

Verified Solution

For each month, the energy cost incurred with a cogeneration system is calculated using a stepby-step procedure based on Eqs. (13.3) and (13.4). Table 13.11 summarizes the results of the stepby-step analysis performed for the month of January. Table 13.12 provides the results for all the months with the payback period for each cogeneration size. In this example, the smaller cogeneration system (200 kW) is more cost-effective because there is no option to sell excess generated power to the utility. However, a detailed economic analysis should be carried out to optimize the size of the cogeneration system.

kWh_{cogen}=Min{24.N_{d}.kW_{cogen};kWh_{actual}}                 (13.3)

TE_{cogen}=Min{24.N_{d}.kW_{cogen};TE_{actual}}          (13.4)

TABLE 13.11 Details of Step-by-Step Analysis Performed for the Month of January in Example 13.3

System 300 kW Cogeneration 200 kW Energy/Cost Requirements
226,400 226,400 Electrical energy requirements (kWh)
2,024 2,024 Thermal energy requirements (MMBtu)
223,400 148,808 Cogenerated electrical energy, kWh_{cogen} (kWh)
1,228 808 Cogenerated thermal energy, TE_{cogen} (MMBtu)
3,000 77,600 Electrical energy to be purchased from utility (kWh)
796 1,206 Thermal energy to be directly generated (MMBtu)
15,957 10,628 Fuel use for cogeneration (gal)
5,686 8,614 Fuel energy for direct generation of thermal energy (gal)
21,643 19,242 Total fuel use requirements (gal)
557 9,258 Cost of utility electrical energy ($)
15,627 13,893 Cost of fuel ($)
4,468 2,976 Cost of maintenance ($)
20,450 26,127 Total cost ($)

TABLE 13.12 Cogeneration Cost Savings and Payback Periods

300
Cogen Cost,
Cogen
($/month)
200
Cogen E
Cost
($/month)
Output(kW)
Conventional
E cost
($/month)
20,450 26,127 41,931
27,687 28,920 41,588
21,753 27,108 40,718
14,813 14,527 29,993
14,121 20,178 34,102
26,034 31,658 45,605
24,142 32,167 49,153
31,536 37,815 52,085
20,414 26,388 40,303
16,339 22,687 37,285
16,512 21,581 33,297
17,892 22,097 32,849
251,692 311,251 478,909 Total ($)
300,000 200,000 0 Equipment cost ($)
1.32 1.19 _ Payback period (yr)