# Power Generation

Many nonresidential buildings require backup or standby power, which can be generated by generator sets, paralleled generators, microgrids or some other onsite power source. Safety, maintainability, efficiency, code compliance and economics play crucial roles in determining the topology of a power generation system. Specific requirements for power vary based on building occupancy type, facility use and critical function.

## Generator sizing examples

### When designing generator systems, such as engine-driven generator sets, design engineers must ensure that the generator selection, sizing, and the design of electrical systems are appropriate for the application.

Consider the task of sizing a 277/480 V, 3-phase generator for three different loading and motor-starting methods. All three examples use the following loads:

• One 150-hp motor, Code F, 95% running efficiency, 0.26 starting PF, and 0.86 running PF
• One 200-hp motor, Code G, 95.4% running efficiency, 0.24 starting PF, and 0.87 running PF
• Miscellaneous loads of 75 kVA, 0.84 starting PF, and 0.91 running PF.

Motor load: The following equations are used to calculate SkVA, SkW, RkVA, and RkW:

SkVA = motor hp x locked-rotor kVA/hp

Where locked-rotor, Code F motor = 5.5 kVA/hp; Code G motor = 6 kVA/hp per NEC, Table 430.7(B)

SkW = SkVA x starting motor PF
RkW = motor hp x 0.746-kW/hp/efficiency
RkVA = RkW/running motor PF

Miscellaneous load: The following equations are used to calculate SkW and RkW:

SkW = SkVA x starting PF
RkW = RkVA x starting PF

Where load kVA remains constant: kVA = SkVA = RkVA

Example 1: A 1,000-kW generator with 2,525 SkVA at 20% voltage dip is selected from the manufacturer’s specification sheet to supply a total load of 2,100 SkVA. The total load of 342 RkW is 34% of the 1,000-kW generator rating. The generator is under-loaded in the final running condition because of the required oversized generator capacity to meet the starting kVA.

Example 2: An 800-kW generator with 2,000 SkVA at 20% voltage dip is selected from the manufacturer’s specification sheet to supply a total load of 1,412 SkVA. The total load of 342 RkW is 43% of the 800-kW generator rating. The generator is under-loaded in the final running condition because of the required oversized generator capacity to meet the starting kVA. When loads were stagger-started (step-loading), the generator SkVA was reduced from the SkVA required in the example of starting all loads concurrently.

Example 3: A 400-kW generator with 765 SkVA at 20% voltage dip is selected from the manufacturer’s specification sheet to supply a total load of 710 SkVA. The total load of 342 RkW is 86% of the 400-kW generator rating. The generator is loaded to around 86% of its rating in the final running condition, assuming transients are acceptable. When loads were stagger-started and reduced voltage was used to start motor loads, the required generator SkVA was significantly reduced.

Tarek Tousson is senior electrical engineer at Stanley Consultants. His expertise is motors, generators, and UPS systems, and he has 20 years of experience designing electrical power distribution systems for mission critical facilities and other types of buildings.

References

NFPA 20: Installation of Stationary Pumps for Fire Protection

NFPA 70: National Electrical Code

NFPA 99: Health Care Facilities Code

NFPA 101: Life Safety Code

NFPA 110: Standard for Emergency and Standby Power Systems covers

## Power Generation FAQ

• ### What is meant by power generation?

Power generation refers to the process of producing electricity from various sources of energy. The energy sources used for power generation can be classified as conventional and nonconventional. Conventional sources include fossil fuels such as coal, natural gas and oil, as well as nuclear energy. Nonconventional sources include renewable energy sources such as solar, wind, hydro, geothermal and biomass.

Power generation typically involves three main stages: fuel processing, power generation and power distribution. In the fuel processing stage, the energy source is extracted, refined and transported to the power generation facility. In the power generation stage, the fuel is used to power generators, which convert the chemical energy of the fuel into electrical energy. The generated electricity is then distributed to homes, businesses and other customers via a power grid.

Power generation is a crucial aspect of modern society, as it provides the energy needed to power homes, businesses and industries. It plays a vital role in the economy and it affects the environment as well, depending on the source of energy used. The increase of renewable energy sources in power generation can have a positive impact on the environment, as it reduces the use of fossil fuels and the associated emissions.

• ### What are the seven power generation methods?

There are several methods for power generation and the seven most common methods are:

• Fossil fuel power generation: This is the most traditional method of power generation, in which fuels such as coal, natural gas and oil are burned to generate heat, which is then used to produce steam that turns turbines to generate electricity.
• Nuclear power generation: Nuclear power plants use nuclear reactions to produce heat, which is then used to produce steam that turns turbines to generate electricity.
• Hydroelectric power generation: This method uses the kinetic energy of falling water to turn turbines and generate electricity.
• Solar power generation: This method uses photovoltaic cells or solar thermal systems to convert the energy from the sun into electricity.
• Wind power generation: This method uses wind turbines to capture the kinetic energy of wind and convert it into electricity.
• Geothermal power generation: This method uses the heat from the earth to generate steam and turn turbines to produce electricity.
• Biomass power generation: This method converts the energy from organic matter, such as wood or agricultural waste, into electricity through combustion or fermentation.

All these methods have their own advantages and limitations and the choice of which method to use depends on various factors such as location, environmental impact, cost and availability of resources.

• ### What is the process of power generation?

Power generation refers to the process of producing electricity from various sources, such as coal, natural gas, nuclear energy, solar energy or wind energy. The specific process used to generate power varies depending on the source of energy being used. For example, coal-fired power plants generate electricity by burning coal to heat water into steam, which then drives a turbine connected to a generator. Nuclear power plants generate electricity by using the heat produced by nuclear reactions to create steam, which then drives a turbine and generator. Solar power plants generate electricity by using photovoltaic cells to convert the energy from the sun into electricity and wind power plants generate electricity by using the kinetic energy from wind to drive turbines that are connected to generators.

• ### Why is power generation important?

Power generation is important because it provides the electricity needed to power homes, businesses and industries. Without electricity, modern society would not be able to function as it does today. Electricity powers lights, appliances, heating and cooling systems, transportation, communication systems and many other essential services.

Power generation is also important for economic development and growth. Access to reliable and affordable electricity is necessary for businesses to operate and for industries to thrive. In addition, power generation can provide jobs and stimulate economic growth in communities where power plants and other electricity-generating facilities are located.

Power generation also plays a critical role in reducing dependence on fossil fuels and addressing climate change. By increasing the use of renewable energy sources, such as solar and wind power, power generation can help to reduce greenhouse gas emissions and the overall environmental impact of electricity production.

Some FAQ content was compiled with the assistance of ChatGPT. Due to the limitations of AI tools, all content was edited and reviewed by our content team.