- A utility has the following monthly billing structure for its industrial customers:A power factor clause states that the billing demand, upon which the demand charge is based, shall be the actual
- The utility has added a ratchet clause to the rate structure described in Example 2.1 . Specifically, the ratchet clause states that no billing demand shall be considered as less than the 70 percent
- i. Calculate the utility bill for a facility during one month characterized by the following parameters:• Actual demand: 450 kW • Energy consumption: 85,000 kWh • Average power factor: 70
- The utility has added a ratchet clause to the rate structure described in Example 2.2 . Specifically, the ratchet clause states that no billing demand shall be considered as less than 70 percent of
- The monthly energy consumption and peak demand history of a commercial building is shown below for one year.The commercial building is on the rate structure defined in Table Month Jan Feb Mar Apr May
- The industrial facility of Example 2.1 has an option of owning and operating its own service transformer with the advantage of reduced rate structure as described below:• Customer charge =
- A company consumed about 355,000 kWh of electrical energy during the month of April. The billed demand is estimated to be 600 kW for April. If the sales tax is 7 percent, calculate the electric
- A manufacturing company consumes on average 250,000 kWh per month and has a billed demand of 1,200 kW during each month. The company can select between two rates: Rate-1 and Rate-2 (described below).
- A utility offers the following rates to its commercial customers:The on-peak season includes the months of June through October. The off-season includes the remainder of the months of any year.The
- Using utility rate structure A, calculate the utility bill for a residence during a summer month when the energy use is 800 kWh.
- Using utility rate structure B, calculate the utility bill for a commercial facility during a winter month when the energy use is 70,000 kWh, the billing demand is 400 kW, and the average reactive
- A company is on the utility rate structure defined as level 1 in Problem 2.5 , In auditing a company, you find it averaged as 65 percent power factor over the past year. It is on the rate schedule
- Calculate the utility bills for an industrial customer serviced by OG&E under two rates:i. Conventional rate with the following charges:Customer charge: $150.00 Energy charge: $0.0264/kWh Demand
- Using utility rate structure C, calculate the utility bill for a residence during a summer month when the energy use is 2,000 kWh with 55 percent of the energy consumption occurring during the
- Calculate the cost savings in electric utility bills for an industrial customer serviced by the OG&E RTP rate used in Example 2.8 if the excess electrical load experienced during the curtailment
- Using utility rate structure D, calculate the gas utility bill for a residence during a month when the energy use is 10.4 MMBtu.
- Using utility rate structure E, calculate the gas utility bill for a commercial facility during a month when the energy use is 15,000 MMBtu and the billing demand is 500 MMBtu/day.
- A building owner has $10,000 available and has the option to invest this money in either (i) a bank that has an annual interest rate of 7 percent or (ii) buying a new boiler for the building. If he
- A company is considering the purchase of a new machine that will last eight years and cost $90,000 in the first year, decreasing by $1,000 each year to $2,000 in the eighth year. Determine how much
- You want to buy a new machine that will last 20 years and cost $200,000. Determine how much money you should pay for this machine each year based on equal annual payments:a. If the interest rate is 5
- An energy audit of a residential heating system reveals that the boiler-burner efficiency is only 60 percent. In addition, the energy audit showed that an electric water heater is used. The house
- After finding that the old boiler has an efficiency of only 60 percent, whereas a new boiler would have an efficiency of 85 percent, the building owner in Example 3.1 has decided to invest the
- Find the various compounding factors for N = 10 years and d = 5 percent.
- An electrical energy audit indicates that the motor control center consumption is 8 × 106 kWh/year. By using high-efficiency motors, a savings of 15 percent can be achieved. The additional cost for
- An electrical energy audit indicates that lighting consumes 12.5 × 106 kWh/year. By using more efficient lighting fixtures, electrical energy savings of 8 percent can be achieved. The additional
- The building owner in Example 3.5 has three options to invest his money, as briefly described below.A. Replace the entire old boiler (including burner) with more efficient heating system. The old
- A residential building is heated with a 78 percent efficient gas-fired furnace (costing $1,600). The annual heating load is estimated at 160 MMBtu. The cost of gas is $6.00/MMBtu. For the discount
- A chiller consumes 9.5 × 105 kWh annually with an overall efficiency of 0.90 kW/ton. If this chiller is replaced by a more energy-efficient chiller (0.75 kW/ton) at a cost of $95,000, determine the
- Two chillers are proposed to cool an office space. Each chiller has a rated capacity of 300 tons and is expected to operate 650 full-load equivalent hours per year. Chiller A has a standard
- In most buildings and industrial facilities, electrical systems consume a significant
- Consider a building with a total real power demand of 500 kW with a power factor of pfe = 0.70 . Determine the required size of a set of capacitors to be installed in parallel with the building
- Provide a simple payback period analysis of lighting controls in a 10,000-ft2 office area comprised of 7,200 ft2 of open landscaped office space and 20 enclosed perimeter offices (2,800 ft2). The
- Determine the cost-effectiveness of replacing a 10-hp motor with an efficiency of 85 percent with a premium-efficiency motor with a rated full-load efficiency of 91.70 percent. Assume that:• The
- Two motors operate 5,000 h/hr at full load. One is 40 hp with an efficiency of 0.75 and a power factor of 0.65, and the other is 100 hp with an efficiency of 0.935 and a power factor of 0.85.
- Consider a building with total 500 luminaires of four 40-W lamps/luminaire.Determine the energy saving after replacing those with two 40-W high-efficiency lamps/luminaire. This building is operated 8
- Consider an aluminum fabrication plant with 400 employees that runs on three shifts for a total of 8,760 hours per year. The company spent $1.1 million in electric energy bills last year. The plant
- Determine the capacitor ratings (in kVAR) to add to an 80 hp motor with an efficiency of 0.85 to increase its power factor from 0.80 to 0.85, 0.90, and 0.95, respectively.
- Consider a three-story office building 50 m × 30 m located in Denver, Colorado, with a window-to-wall ratio (WWR) of 0.25 with low-E glazing, which has a visible transmittance of 0.41 . The building
- Determine the cost-effectiveness of selecting a unit with an efficiency of 99.95 percent rather than 99.90 percent for a 500-kVA rated transformer. Assume that:• The cost of electricity is
- For the case of a balance temperature of 65°F, compare your results with the heating degree-days for the three cities directly computed from hourly weather data (these degree-days are widely
- A daylighting system using dimming controls is being considered for a five-story office building located in Denver, Colorado. A typical floor is 200 ft × 50 ft with perimeter offices extending 12 ft
- Assess the impact of two devices on the current THD of a building: a 13-W compact fluorescent lamp (CFL) with electronic ballasts and a laser printer while printing.Use the data provided in Table
- Determine if it is economically feasible to install number 10 (AWG) copper conductors instead of number 12 (AWG) on a 400-ft branch circuit that feeds a load of 16 amperes. Assume that:• The load
- The nameplate of a motor provides the following information:a. Calculate the following parameters: the slip RPM and the power factor of the motor.b. Determine if it is cost-effective to replace this
- Determine the cost-effectiveness of adding a dimming daylighting control system to a thin two-story office building (each floor is 24 ft × 1,000 ft) with a window-to-floor area ratio of 30 percent.
- A blower door test has been performed in a house located in Evergreen, Colorado. The results of the pressurization and depressurization tests are summarized in Figure 6.4 based on the results of the
- Estimate the heating and cooling degree-days for the base temperature, Ttb = 60°F, for Denver, Colorado, for the month of May. Use the data provided in Appendix B.Appendix B Country Albania Algeria
- Consider a three-phase 1,500 kVA transformer to step down the voltage from 13.8 kV to 480Y/277 V. The transformer is old and needs to be replaced. Two options are available: (i) replace it by the
- Repeat Problem 6.1 using the simplified calculation method of Schoenau and Kehrig. Use the required statistical data for the various US locations provided in the appendix. In addition to the heating
- Determine the heating base-load, the balance temperature, and the BLC of a house located in Boulder, Colorado, based on the monthly utility bills provided in the following table. For the analysis
- An energy audit of the roof indicates the following:It is proposed to add R-19 insulation in the roof.a. Comment on the potential energy savings of adding insulation.b. If the insulation costs
- A machine shop has a 500-m2 metal frame roof that is uninsulated. Determine the payback period of adding insulation (R = 2.0 °C·m2/W). The building is electrically heated. The cost of electricity
- A window upgrade is considered for an apartment building from double-pane metal frame windows (UE = 4.61 W/m2·°C) to double-pane with low-e film and wooden frame windows (UR = 2.02 W/m2·°C). The
- Determine the annual energy savings due to replacement of a single-pane window (R-1) by a double-pane window (R-2). The total area of the glazing is 200 ft2. Assume the following: Heating degree-days
- Consider a heated manufacturing shop with a total conditioned volume of 1,000 m3. A measurement of the air leakage characteristics of the shop showed an infiltration rate of 1.5 ACH. Determine the
- Consider a house in Denver, Colorado, has the following building characteristics:• Exterior walls with a total R-value of 19 (i.e., R = 19 hr·°F·ft2/Btu = 3.35 °C·m2/W) insulation and total
- Do you recommend adding R-20 insulation to a 25,000 ft2 uninsulated roof (R-5) when you consider a 25-year life cycle with a rate of return of 8 percent? Assume the following: Heating degree-days
- A 50-hp constant-volume fan is to be retrofitted to a variable-volume fan. Three options are considered:The fan is operated 5,500 hours per year. If the cost of electricity is $0.08/kWh and the
- A thermal process within a facility rejects 10,000 lbm/hr of hot water (Tout = 190°F). An energy audit of the facility revealed that instead of using an open water system, which feeds fresh cold
- A 50,000-cfm CV AHU is to be converted to a VAV system. The motor for the existing supply fan is rated at 35 hp with 90 percent efficiency. The fan is operated for 3,500 hours/year according to the
- An office building has a two-level enclosed parking garage with a total capacity of 450 cars, a total floor area of 8,300 m2 (89,290 ft2), and an average height of 2.75 m (9.0 ft). The total length
- A heat exchanger is considered to recover heat from the exhaust air of a 5,000-cfm laboratory makeup air system located in Denver, Colorado. The indoor temperature within the laboratory is kept at
- Consider a 200,000-ft2 enclosed parking garage that can hold 1,000 cars.a. Determine the size of the supply/exhaust fans to ventilate this garage if 1.5 cfm/ft2 are required. Assume a fan pressure of
- It is proposed to retrofit the supply fan of a 60,000-cfm AHU. The fan has a 25-hp motor with a total efficiency of 85.5 percent. If the fan is operating 5,500 hours per year and if the cost of
- Consider a 80,000-ft2 two-story building. A 60,000-cfm AHU services the building. The building is occupied 50 hours per week. The fuel cost is $5.00 per 106 Btu and electricity cost is $0.09 per kWh.
- An 80,000-ft2 office building located in Chicago has a dual-duct air-conditioning system with a 60,000-cfm air-handling capacity (60 hp). Determine the annual energy and cost savings that could be
- A thermal wheel is considered to recover heat from the exhaust air of 20,000 AHU operating in a hospital in Denver, Colorado. The indoor temperature within the hospital is kept at Tin = 68°F during
- Estimate the fuel savings obtained by using low-leakage dampers for a 40,000-cfm AHU that serves an office building located in Chicago, Illinois. The office is conditioned during the entire heating
- Consider a building in Denver, Colorado, with 70,000 cfm single-duct CV AHU. The building is occupied 60 hours per week with 500 people. The indoor temperature is always maintained at 73°F. Fuel
- Estimate the fuel savings obtained by resetting the hot deck of a 60,000 cfm dual duct system by 2°F during the winter and 1°F during the summer. The HVAC system is operated 80 hours per week and
- Consider a building in Denver with a 90,000-cfm single-duct CV AHU. The building is occupied 60 hours per week with 600 people. The indoor temperature is always maintained at 72°F. Fuel cost is
- Use the data provided in Problem 14.1. Determine the critical cost of fuel, diesel, and natural gas (assuming the cost of electricity remains constant); when using the heat wheel is not economical if
- Estimate the heating and cooling energy and cost savings incurred by converting a 20,000-cfm single duct reheat system to a VAV system in an office building located in Chicago, Illinois. For the CV
- Provide a simple payback period of installing a heat wheel system in a 80,000-cfm constant-volume AHU. During the winter, air is exhausted at 72°F, and during the summer at 76°F. The heat recovery
- Determine the simple payback period of installing a heat recovery system at a cost of $1.25/cfm for a 10,000-cfm makeup air system in a laboratory located in Chicago, Illinois. The indoor temperature
- Determine the simple payback period of installing a heat recovery system at a cost of $0.15/L/s for a 7,000/L/s makeup air system in a laboratory located in New York, New York. The indoor temperature
- A flue gas analysis of an oil fuel-fired boiler indicates that the CO2 content is 11 percent, with a gas flue temperature of 343°C (650°F). Determine the overall thermal efficiency of the boiler.
- A recent analysis of your gas-fired boiler showed that you have 30 percent excess combustion air. Discussion with the local gas company has revealed that you could use 10 percent excess air if the
- A crude but effective approach to estimate steam leak (in lb/hr) from an orifice is to use the following expression:Estimate the hourly, monthly, and annual costs of steam leaks from a 300-psig pipe.
- The boiler in Example 8.1 uses 1,500,000 L of fuel oil per year. An instrumentation kit is purchased at a cost of $10,000 and is used to adjust the boiler operation so that the excess O2 is only 3
- Consider the water distribution system with only one primary pump as depicted in Figure Ex 8.1 . Determine the horsepower of the primary pump and check the settings of the valves for various
- An existing chiller with a capacity of 800 kW and with an average seasonal COP of 3.5 is to be replaced by a new chiller with the same capacity but with an average seasonal COP of 4.5 . Determine the
- A centrifugal chiller with a capacity of 500 kW and with an average seasonal COP of 4.0 operates with a leaving chilled temperature of 4.5 °C. Determine the cost savings incurred by installing an
- An efficiency test of a boiler fired by fuel No. 2 indicated a flue gas temperature of 700°F and excess air of 40 percent. The annual fuel consumption of the boiler is 85,000 gallons/year. The cost
- A boiler has an annual fuel oil No. 2 consumption of 325,000 gallons. The cost of fuel is $1.50/gallon. A combustion efficiency test done on the boiler indicated that the stack temperature is 650°F
- A combustion efficiency test done on a gas-fired boiler indicated that the stack temperature is 750°F and the CO2 content is 7 percent.a. Determine the excess combustion air and the boiler
- A combustion efficiency test done on a boiler indicated that the stack temperature is 350°C and the CO2 content is 10 percent.a. Determine the excess combustion air and the boiler efficiency if the
- A combustion efficiency test performed on a boiler using fuel oil has indicated that the stack temperature is 700°F and the CO2 content is 15 percent.a. Determine the excess combustion air and the
- Consider an 800-ton chiller operating for 1,600 equivalent full-load hours per year. The chiller is a centrifugal chiller that is rated at 0.72 kW/ton. Determine the energy and cost savings when the
- Consider the water distribution system given in Figure Example 8.1. Assume the pump efficiency of 0.70.a. Determine the primary pump size (in hp) and the valve settings to balance the system.b.
- Redo Problem 8.8 for an 800-ton absorption chiller using 10 lb of steam per ton. The cost of steam is $10/1,000 lb.Problem 8.8Consider an 800-ton chiller operating for 1,600 equivalent full-load
- Provide a simple payback analysis for implementing a cogeneration system in a hospital. Assume the following characteristics for the cogeneration system:• Fuel input rate: 8,000 Btu/kWh• Heat
- Consider a 20-MW cogeneration power plant in a campus complex. An energy balance analysis indicates the following energy fluxes for the power plant:It is estimated that all the condenser losses but
- Same as Problem 9.1. Assuming that the electric cost varies from $0.05/kWh to $0.15/kWh (including demand charge), determine the variation of the cogeneration system payback period versus electricity
- A 300-ton chiller with 1.2 kW/ton average seasonal efficiency is operated 3,500 hours per year with an average load factor of 70 percent. This chiller needs to be replaced by either chiller A or
- A building with a peak load of 2,000 tons and equivalent full load hours of 2,500 hr/year, determine the most economical option to deliver cooling needs between the two design alternatives.Use LCC
- Same as Problem 9.1. If the life of the cogeneration system is 40 years, provide the optimal size of the cogeneration system for the hospital when the average interest rate is 8 percent and the
- Consider the cooling load profile for an office building shown in Figure 9.17 . The cooling is provided by a chiller having a capacity of 1,000 kW and with an average seasonal COP of 3.5 . The
- Consider a 60-kW cogeneration system that produces electricity and hot water with the following efficiencies:(a) 26 percent for the electricity generation, and(b) 83 percent for the combined heat and
- Consider a 5-kW rooftop PV system that can be installed at a cost of $3000/kW and maintained at a cost of $0.10/kWh. The building is connected to the grid, which provides electricity at $0.10/kWh.