Chapter 13 Module 39

On average what percentage of time does a land-based wind turbine generate electricity?

25%

A resistance coil water heater is

99 percent efficient, meaning 99 percent of the energy in the electricity is transferred to the water.

Wind farm

A group of wind turbines that produce electricity. Often placed in rural areas with high winds, or offshore in the ocean where winds are often consistently strong as well. Offshore wind parks, which are clusters of turbines, are often located in the ocean within a few miles of the coastline.

Solar domestic hot water system

A nonfreezing liquid (such as nontoxic antifreeze) is circulated by an electric pump through a closed loop of pipes. This circulating liquid moves from a water storage tank to a solar collector on the roof, where it is heated, and back to the tank, where a heat exchanger transfers the heat to water.

Photovoltaic solar cells

A system of capturing energy from sunlight and converting it directly into electricity

Ground source heat pumps

A technology that transfers heat from the ground to a building. These pumps take advantage of the high thermal mass of the ground. The ground retains the Sun's heat and these pumps tap that heat source to heat and cool residential and commercial buildings. This is often referred to as geothermal energy but the heat source is technically the Sun.

Wind turbine

A turbine that converts wind energy into electricity

Hot water heat pumps

A variation of the ground source heat pump that extracts heat from the air in a garage or basement and transfers it to water in a domestic hot water tank. This waters is then used for household activities such as washing dishes and taking showers.

Fuel cell

An electrical-chemical device that converts fuel, such as hydrogen, into an electrical current.

Currently, most available hydrogen is produced by

An energy-intensive process of burning natural gas in order to extract its hydrogen. Carbon dioxide is a waste product of this combustion.

The amount of solar energy available in a particular place varies based on

Cloudiness, time of day, and season

Disadvantages of wind generated electricity

Currently, most off-grid residential wind energy systems rely on batteries to store electricity. Batteries are expensive to produce and hard to dispose of or recycle. Birds and bats can be killed by wind turbines. Some say they destroy the scenic beauty of landscapes and can be too noisy as well.

Active solar energy

Energy captured from sunlight with advanced technologies

Wind energy

Energy generated from the kinetic energy of moving air

Drawbacks of active solar energy systems

Expensive to manufacture and install. Manufacture requires a great deal of energy, water, and toxic materials that can be released into the environment.

Today, wind energy is the

Fastest-growing major source of electricity in the world

Other ways energy scientists are looking to obtain hydrogen

Harvesting it from certain kinds of algae. Under certain conditions, some photosynthetic algae and bacteria, using sunlight as their energy source, can give off hydrogen gas.

By exchanging heat with the ground, a ground source heat pump can

Heat and cool a building using 30 to 70 percent less energy than traditional furnaces and air conditioners.

Geothermal energy

Heat energy that comes from the natural radioactive decay of elements deep within the earth. Wherever magma comes close to groundwater, that groundwater is heated and the pressure it creates sometimes drives it to the surface.

Harvesting geothermal energy

Hot groundwater can be piped directly into household radiators to heat a home. In other cases, heat exchangers can collect heat by circulating cool liquid underground, where heat from the ground flows to the cool circulating liquid, and then returns to the surface.

Basic hydrogen fuel cell process

Hydrogen gas enters the cell from an external source. Protons from the hydrogen molecules pass through a membrane, while electrons flow around it, producing an electric current. Water is the only waste product of this reaction. In a fuel cell vehicle, hydrogen is the fuel that reacts with oxygen to provide electricity to run the motor.

Geothermal energy has less growth potential because

It is not easily accessible everywhere. Hazardous gases and steam may also escape from geothermal power plants.

Ultimately, the Sun is the source of all winds because

Its solar radiation and ground surface heating drives air circulation which results in wind patterns

Concentrating solar thermal systems (CST)

Large-scale application of solar energy to electricity generation. CST systems use lenses or mirrors and tracking systems to focus the sunlight falling on a large area into a small beam. The heat from this beam is used to evaporate water and produce steam that turns a turbine to generate electricity.

Advantages of wind energy

Nondepletable, clean, free energy resource. The amount available tomorrow does not depend on how much we use today. Furthermore, once a wind turbine has been manufactured and installed, the only fossil fuel output is from the fuel workers need to travel to and from the turbine location. Wind farms can also share the land with other uses, such as cattle grazing.

Basic process of a fuel cell

Operates much like a battery. In a battery, electricity is generated by a reaction between two chemical reactants. This reaction happens in a closed container to which no additional materials can be added. Eventually the reactants are used up. In a fuel cell though, the reactants are added continuously to the cell, so the cell produces electricity for as long as it continues to receive fuel.

Solar ovens

Ovens that focus sunlight with mirrors or reflective materials and concentrate it on food, therefore cooking it. Sometimes referred to as a "box cooker"

Photovoltaic solar energy

Solar panels on a roof can be used to supply electricity for use in the house. Most photovoltaic systems are tied to the electrical grid, meaning that any extra electricity generated and not needed is sent to the electric utility, which buys it or gives the customer credit toward the cost of future electricity use.

The viability of hydrogen

Some policy makers consider hydrogen fuel cells to be the future of energy and the solution to many of the world's energy problems. Hydrogen is also an energy carrier, which means it can store energy for later use, unlike renewable energy sources like the Sun and wind. Hydrogen fuel cells are also 80 percent efficient in converting the potential energy of hydrogen and oxygen into electricity, with water as the only byproduct.

Electrolysis

The application of an electric current to water molecules to split them into hydrogen and oxygen. An alternative and less energy-intensive way to produce the hydrogen needed in a hydrogen fuel cell.

Sustainability of geothermal energy

The heat released by decaying radioactive elements in the Earth is essentially nondepletable in the span of human time. However, the groundwater that often carries that heat to the surface can be depleted if not used sustainably. Returning the water to the ground to be reheated is one way to use geothermal energy sustainably.

In a fuel cell, electricity is generated by

The reaction of hydrogen with oxygen, which forms the byproduct of water.

Passive solar heating

The use of sunlight to heat buildings directly. This can be done through positioning windows on south-facing walls to admit solar radiation in winter, converting buildings with dark roofing material in order to absorb the maximum amount of heat, and building homes into the side of a hill.

Benefits of active solar energy systems

They can generate hot water or electricity without producing CO2 or polluting the air or water during operation. They can produce electricity when it is in high demand, particularly on hot sunny days for air conditioning. By producing electricity during peak demand hours, these systems can help reduce the need to build new fossil-fuel power plants. Many governments, including the US and Germany, have given tax breaks and other financial assistance to the solar industry.

Disadvantages of hydrogen as a fuel

We still have to learn how to obtain hydrogen without expending more fossil fuel energy than we would save. We also still need to establish a safe and efficient distribution network. Vehicles would also need much larger gas tanks, and there would be risk of a rupture in which the hydrogen gas could explode.

Generating electricity from wind

Wind turns the blades of the wind turbine and the blades transfer energy to the gear box that in turn transfers energy to the generator that generates electricity.

A hydrogen fuel cell is most similar to

a battery

Which is NOT true about geothermal energy a. it is only available in limited areas b. it cannot be used for cooling c. it can be locally depleted due to heavy use d. ground source heat pumps require an additional source of energy

b. it cannot be used for cooling

In a hot water heat pump

between 200 and 250 percent of the amount of energy in the electricity used to run the hot water heat pump is transferred to the water in the tank. This is possible because the technology uses the energy in the electricity and also extracts heat energy from the surrounding air.

Which is NOT a benefit of solar energy systems? a. they typically produce electricity during peak demand b. they require very little maintenance c. they produce electricity continuously d. they do not produce pollution while generating electricity

c. they produce electricity continuously

Which is an application of passive solar technology a. concentrating solar thermal b. photovoltaic cells c. solar water heating d. solar ovens

d. solar ovens