Energy Management Chapter 9: Alternative Energy Sources

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Questions and Answers

What is the approximate rate at which solar energy arrives at the earth’s atmosphere?

1000 W/m2

1353 W/m2 (correct)

2000 W/m2

1500 W/m2

What is the equivalent solar irradiance in Btu/hr ft2 based on the given rate?

300 Btu/hr ft2

850 Btu/hr ft2

600 Btu/hr ft2

428 Btu/hr ft2 (correct)

Which of the following statements is true regarding solar irradiance?

It is primarily affected by temperature.

It varies depending on geographical location. (correct)

It is measured in Joules per cubic meter.

It is constant throughout the day.

In solar irradiance measurements, what unit is used to express power per unit area?

Watts per square meter Signup and view all the answers

If solar energy arrives at a rate of 1353 W/m2, how much energy is that in terms of energy per hour for one square meter?

$1353 imes 3600$ J/hr Signup and view all the answers

What is the full name of the individual mentioned in the content?

Dr. Essam Abou Yehia Signup and view all the answers

What is the numerical code associated with Essam Abou Yehia?

50225245 Signup and view all the answers

Which of the following best describes Essam Abou Yehia's title?

Doctor Signup and view all the answers

Which of the following statements is accurate regarding the format presented?

The content is presented in a structured manner. Signup and view all the answers

What can be inferred about the purpose of this content?

To document a professional credential. Signup and view all the answers

What is one possible use of removing moisture from a material?

To improve the efficiency of cooling devices Signup and view all the answers

Which of the following scenarios might require operating a cooling device?

To maintain a constant temperature in a freezer Signup and view all the answers

What could be a consequence of excessive space heat?

Increased moisture levels in a controlled environment Signup and view all the answers

What is the primary function of a cooling device?

To reduce the temperature of a specific area Signup and view all the answers

Why is it important to control moisture levels in materials?

To prevent degradation and improve performance Signup and view all the answers

What is one application of solar thermal systems?

Heating water for residential use Signup and view all the answers

Which system utilizes solar energy to produce electricity directly?

Photovoltaic systems Signup and view all the answers

What is a key advantage of wind power?

Has low operational costs after installation Signup and view all the answers

Which statement is true regarding photovoltaic systems?

They have no moving parts Signup and view all the answers

What is the primary energy source for wind power?

Atmospheric movement Signup and view all the answers

What is the primary function of evacuated tubes in solar applications?

To trap heat and prevent loss through convection Signup and view all the answers

How does the design of evacuated tubes help prevent heat loss?

By creating a vacuum that reduces convection Signup and view all the answers

In what way is the concept of evacuated tubes similar to flat plate collectors?

Both allow solar radiation to penetrate and heat a space Signup and view all the answers

What does the term 'vacuum' refer to in the context of evacuated tubes?

The absence of air that minimizes heat transfer Signup and view all the answers

What is a significant benefit of using evacuated tubes over other solar heating methods?

They can maintain higher temperatures and efficiency in various conditions Signup and view all the answers

What type of wind turbines are predominantly in use today?

Horizontal-axis turbines Signup and view all the answers

Which statement accurately describes the characteristic of the majority of modern wind turbines?

They are primarily horizontal-axis. Signup and view all the answers

What is a key feature of horizontal-axis wind turbines compared to other types?

They typically have higher energy output. Signup and view all the answers

Which of the following is NOT a benefit associated with horizontal-axis wind turbines?

Higher noise levels Signup and view all the answers

What mainly determines the type of wind turbines utilized in current applications?

Suitability for wind conditions Signup and view all the answers

Study Notes

Energy Management 1 AU 2nd Term Spring 2024

Chapter 9 is about alternative energy sources
Alternative energy sources are non-depleting or renewable
Examples include solar, wind, and others that replace traditional fossil fuels
Government funding and tax incentives for alternative energy reduced in the 1980s and 1990s
The MENA region receives high solar irradiance globally

Solar Thermal Systems

Introduction to the topic
Solar Irradiance details
Solar Thermal Collectors
Thermal Storage Systems
Surface temperature (Tsurface) = 5778 K (5505°C)
Core temperature (Tcore) = 15.6 × 10⁶ K
Power = 3.85 × 10²⁶ Watts
Energy = 3.37 × 10²⁷ KW⋅hr/yr
Annual Energy Intercepted on Earth: 1.5 × 10¹⁸ KW⋅hr/year (0.000000045%)
World Energy Demand: 1.4 × 10¹⁴ KW⋅hr/yr (0.0093%) - Total: 4.2 × 10⁻¹² %

Solar Irradiance (Distribution)

The MENA region receives the highest solar irradiance globally

Solar Irradiance (Orientation)

Designers should estimate the solar radiation angle to remain perpendicular to it for maximum energy collection

Solar Thermal Collectors (Non-Concentrating)

Flat plate collectors
Evacuated tube collectors
Volumetric air collectors
The flat-plate collector typically faces south in the Northern Hemisphere
These collectors bring the temperature of a liquid or air up from ambient conditions
Tracking-type collectors used when high temperatures (over 120°C) are required

Solar Thermal Collectors (Concentrating)

Parabolic Trough collectors
CSP collectors
Fresnel collectors
Solar Power Tower
Solar Dish Sterling Engine

Solar Irradiance (Numerical Facts)

Solar energy arrives at the Earth's atmosphere at a rate of approximately 1353 W/m² (428 Btu/hr ft²)
This value is the solar constant
Part of this is reflected, absorbed and scattered in the atmosphere
When at 40° North Latitude, the noontime radiation rate on a flat surface normal to the sun's rays around 946 W/m² (300 Btu/hr ft²) on a clear day
A solar collector should track the sun to remain normal to the incoming rays at all times
A perfect collector may only capture 70% of the energy
The realistic area to generate 293 kWh(16 million Btu) of energy per day is around 53 m²(567 ft²)

Volumetric Air Collector

An alternative to liquid solar systems
Freezing is not a concern with volumetric air collectors
Leaks are less detrimental than with liquid systems
Corrosion is less likely to occur

Parabolic Trough

Temperature range: 250-450°C
Concentrating collectors for high temperatures (like power generation)
Cannot use diffuse or scattered radiation, must track the direct sun

Compound Parabolic Concentrator (CPC)

Used in residential and commercial heating applications

Fresnel

Composed of multiple smaller flat mirrors to concentrate radiation like parabolic troughs, but simpler and cheaper

Solar Power Tower

Uses a set of two-axis tracking mirrors (heliostats) to reflect sunlight to a central tower
Uses molten salt (Sodium Nitrate NaNO₃) as a coolant

Thermal Storage Systems

Energy demand isn't always tied to solar availability, so storage is needed
Water is the most common storage, often in tanks, but water freezes and therefore antifreeze may be required.
Rock-bed storage is used with air-type collectors.

Solar Cells (Photovoltaics)

The electronic properties of a semiconductor converts sunlight to electricity
Most solar cells are p-n junction diodes (composed of p-type and n-type materials)
p-n junctions have electronic asymmetry
N-type regions have high electron densities and low hole densities. Electrons move easily; holes move with difficulty
P-type materials are the opposite
Excess electron-hole pairs are generated when illuminated
Electrons move from p-type to n-type, and holes move in the opposite direction

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Description

Explore Chapter 9 of Energy Management, focusing on alternative energy sources such as solar and wind power. Learn about the benefits of renewable energy and the impact of historical government funding in this sector. Additionally, discover the significance of solar irradiance, particularly in the MENA region.