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Chapter 9: Problem 11

A financial services company has a computer server facility that requires very reliable electric power. The power demand is \(3000 \mathrm{~kW}\). The company has hired you as a consultant to study the feasibility of using 250-W microturbines for this application. Write a report discussing the pros and cons of such an arrangement compared to purchasing power from the local utility.

Short Answer

Expert verified
12000 microturbines are needed. Evaluating microturbines versus utility power involves considering costs, reliability, space, maintenance, and environmental impact.

Step by step solution

01

Calculate the Total Power Demand

The total power demand for the facility is given as 3000 kW.
02

Determine Number of Microturbines Required

Each microturbine produces 250 W of power. Convert this to kW by dividing by 1000:\[ 250 \text{ W} = 0.25 \text{ kW} \]Next, calculate the number of microturbines required to meet the 3000 kW demand:\[ \text{Number of microturbines} = \frac{3000 \text{ kW}}{0.25 \text{ kW/microturbine}} = 12000 \]
03

Analyze the Cost and Space Requirements

Consider the cost and space needed for 12000 microturbines. Compare this with the cost and logistics of getting power from the utility. Research cost per microturbine and required space for installation.
04

Evaluate Reliability and Maintenance

Assess the reliability of microturbines versus utility power. Microturbines may have maintenance and operational considerations. Consider the redundancy and failure rates of microturbines.
05

Consider Environmental Impact

Review the environmental footprint of using microturbines, including emissions, versus the utility's power generation methods which might include a mix of renewable and non-renewable sources.
06

Summarize Pros and Cons

Summarize the pros and cons: Pros of microturbines can include independence from the grid, potential for lower long-term costs, and redundancy. Cons can include high initial setup cost, maintenance complexity, and environmental impact.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Power Demand Calculation
Calculating power demand is the first step in understanding the feasibility of any energy solution. For the financial services company's server facility, the power demand totals 3000 kW.
Microturbines can help provide this power. Each microturbine generates 250 W, equivalent to 0.25 kW (since 1 kW = 1000 W).
To meet the facility's power demand using 250-W microturbines:
  • Convert 250 W to kW: \( 250 \text{ W} = 0.25 \text{ kW} \)
  • Calculate the number of microturbines required: \[ \text{Number of microturbines} = \frac{3000 \text{ kW}}{0.25 \text{ kW/microturbine}} = 12000 \]

Thus, you'll need 12000 microturbines to generate 3000 kW of power.
Cost Analysis
Understanding the costs is crucial to deciding whether microturbines are a feasible option for the company's power needs. Begin by considering:
  • Initial setup costs: Calculate the cost of purchasing 12000 microturbines. Research shows that each microturbine can be expensive.
  • Space requirements: Figure out how much space these 12000 microturbines will occupy and what that space will cost.

Compare these costs against the price of purchasing electricity from the local utility. Include considerations like installation, infrastructure, and potential subsidies for renewable energy.
Reliability Assessment
Reliability is a vital factor for facilities requiring consistent power, such as a server facility. With microturbines, assess these points:
  • Redundancy: Having 12000 microturbines provides redundancy. Even if some units fail, the remaining ones can still provide power.
  • Failure Rates: Regularly analyze the failure rates of microturbines compared to the established reliability of the local utility.
  • Operational Stability: Unlike the grid, microturbines need regular maintenance, which can affect their reliability.

A thorough assessment will show whether microturbines can meet the reliability required.
Environmental Impact
Environmental considerations are essential when choosing a power source. Compare the environmental footprints:
  • Microturbine Emissions: Microturbines may emit pollutants like NOx and CO2, depending on the fuel used.
  • Renewable Sources: Microturbines can use renewable fuels, reducing their environmental impact.
  • Grid Power: Evaluate the local utility's power mix, which can include various sources like coal, natural gas, nuclear, and renewables.

Overall, consider how each option aligns with environmental regulations and the company's sustainability goals.
Maintenance Requirements
Maintenance is a critical factor, especially for a facility that needs reliable power at all times. Review the following aspects of maintenance for microturbines:
  • Regular Servicing: Microturbines require routine maintenance, including checking and replacing parts.
  • Downtime: Plan for potential downtime during maintenance and have backup systems in place.
  • Skill Requirements: Ensure that the staff is trained to handle microturbine maintenance or budget for hiring specialized technicians.

When comparing with utility power, consider that the local utility handles most of the maintenance, potentially reducing the company's operational complexity.

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Most popular questions from this chapter

An engine working on the air-standard Otto cycle is supplied with air at \(0.1 \mathrm{MPa}, 27^{\circ} \mathrm{C}\). The compression ratio is 8 . The heat supplied is \(1400 \mathrm{~kJ} / \mathrm{kg}\). Calculate the maximum pressure and temperature of the cycle, the cycle efficiency, and the mean effective pressure. For air, take \(c_{p}=1.005 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K}, c_{v}=0.718\) \(\mathrm{kJ} / \mathrm{kg} \cdot \mathrm{K}\) and \(k=1.4\)

Air at \(3.5\) bar, \(520 \mathrm{~K}\), and a Mach number of \(0.3\) enters a converging-diverging nozzle operating at steady state. A normal shock stands in the diverging section at a location where the Mach number is \(M_{x}=1.7\). The flow is isentropic, except where the shock stands. If the air behaves as an ideal gas with \(k=1.4\), determine (a) the stagnation temperature \(T_{\mathrm{ox}}\), in \(\mathrm{K}\). (b) the stagnation pressure \(p_{\mathrm{ox}}\), in bar. (c) the pressure \(p_{x}\), in bar. (d) the pressure \(p_{\mathrm{y}}\) in bar. (e) the stagnation pressure \(p_{\mathrm{oy}}\), in bar. (f) the stagnation temperature \(T_{\mathrm{oy}}\), in \(\mathrm{K}\). If the throat area is \(7.5 \times 10^{-4} \mathrm{~m}^{2}\), and the exit plane pressure is \(2.5\) bar, determine the mass flow rate, in \(\mathrm{kg} / \mathrm{s}\), and the exit area, in \(\mathrm{m}^{2}\).

Air enters the first compressor stage of a cold air-standard Brayton cycle with regeneration and intercooling at \(100 \mathrm{kPa}\), \(300 \mathrm{~K}\), with a mass flow rate of \(6 \mathrm{~kg} / \mathrm{s}\). The overall compressor pressure ratio is 10 , and the pressure ratios are the same across each compressor stage. The temperature at the inlet to the second compressor stage is \(300 \mathrm{~K}\). The compressor stages and turbine each have isentropic efficiencies of \(80 \%\) and the regenerator effectiveness is \(80 \%\). For \(k=1.4\), calculate (a) the thermal efficiency of the cycle. (b) the back work ratio. (c) the net power developed, in \(\mathrm{kW}\). (d) the rates of exergy destruction in each compressor stage and the turbine stage as well as the regenerator, in \(\mathrm{kW}\), for \(T_{0}=300 \mathrm{~K}\)

Air enters the diffuser of a ramjet engine at \(45 \mathrm{kPa}, 240 \mathrm{~K}\), with a velocity of \(450 \mathrm{~m} / \mathrm{s}\), and decelerates essentially to zero velocity. After combustion, the gases reach a temperature of \(1120 \mathrm{~K}\) before being discharged through the nozzle at \(45 \mathrm{kPa}\). On the basis of an air-standard analysis, determine (a) the pressure at the diffuser exit, in \(\mathrm{kPa}\). (b) the velocity at the nozzle exit, in \(\mathrm{m} / \mathrm{s}\). Neglect kinetic energy except at the diffuser inlet and the nozzle exit.

A two-stage air compressor operates at steady state, compressing \(0.15 \mathrm{~m}^{3} / \mathrm{s}\) of air from \(100 \mathrm{kPa}, 300 \mathrm{~K}\), to \(1100 \mathrm{kPa}\). An intercooler between the two stages cools the air to \(300 \mathrm{~K}\) at a constant pressure of \(325 \mathrm{kPa}\). Each compressor stage has an isentropic efficiency of \(80 \%\). Calculate the power required to run the compressor, in \(\mathrm{kW}\), and compare the result to the power required for a single stage compression from the same inlet state to the same final pressure, if the isentropic efficiency of the single stage compressor is \(80 \%\).
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