Chapter 13 Achieving Energy Sustainability What is renewable

Chapter 13 Achieving Energy Sustainability

What is renewable energy? • • • Renewable energy can be rapidly regenerated, and some can never be depleted, no matter how much of them we use. Potentially renewable energy can be regenerated as long as we do not consume them more quickly than they can be replenished. An example is biomass: trees and sugarcane. Nondepletable energy is solar, wind, geothermal, hydroelectric, and tidal energy which cannot be depleted within a human life span.

What is renewable energy? • Figure 13. 1 shows both renewable and nonrenewable energy resources. Fossil fuels and nuclear fuels are nonrenewable energy resources. Renewable energy resources include potentially renewable energy sources such as biomass and nondepletable energy sources such as solar radiation and wind.

What is renewable energy? • Figure 13. 2 shows global energy use as of 2007. Renewable energy resources provide about 13% of energy worldwide.

What is renewable energy? • Figure 13. 3 shows energy use in the U. S in 2008. Only 7% of the energy used in the U. S. comes from renewable energy resources.

How can we use less energy? • • • Energy conservation- finding ways to use less energy. For example, lowering your thermostat during the winter or driving fewer miles. Energy efficiency- getting the same result from using a smaller amount of energy. Some electric companies bill customers with a tiered rate system: customers pay a low rate for the first increment of electricity they use and pay higher rates as their use goes up.

How can we use less energy? • Figure 13. 4 shows different ways individuals can reduce their energy use in and outside the home. One example is to purchase Energy Star appliances that use less electricity (but do cost a little more).

Benefits of Conservation and Efficiency • • Many energy companies have an extra backup source of energy available to meet the peak demand, the greatest quantity of energy used at any one time. Variable price structure- utility customers can pay less to use energy when demand is lowest and more during peak demand.

Sustainable Design • • Improving the efficiency of the buildings we live and work in. Building houses close to where residents work reduces reliance on fossil fuels for transportation, which in turn reduces the amount of pollution and carbon dioxide released into the atmosphere.

Passive Solar Energy • Thermal inertia is the ability of a material to retain heat or cold. Materials with high thermal inertia stay hot once they have been heated or cooled. • Figure 13. 6 shows an example of thermal inertia being the “Heatabsorbing floor” made of concrete, stone, brick etc…

Sustainable Design • Figure 13. 7 shows the California Academy of Sciences. The sustainable design of this San Francisco research institution maximizes the use of natural light and ventilation. The building generates much of its own electricity with solar panels on its roof and captures water in its rooftop garden.

Biomass is energy from the Sun • Figure 13. 8 shows the sources of energy types. The sun is the ultimate source of almost all types of energy.

Biomass is energy from the Sun • • • Biomass energy resources encompass a large class of fuel types that include wood and charcoal, animal products and manure, plant remains, and municipal solid waste (MSW), as well as liquid fuels such as ethanol and biodiesel. Wood, Charcoal and Manure- used to heat homes throughout the world. Biofuels are when biomass are processed or refined into a liquid fuels such as ethanol and biodiesel. (Chevy cars and trucks are know to be flex-fuels cars because they can run on gasoline or biofuels like E 85. )

Modern Carbon vs. Fossil Carbon • • • Many people are confused how burning biomass such as wood is better than burning coal. The carbon found in biomass was in the atmosphere as carbon dioxide, taken in by the tree, and by burning it we put it back into the atmosphere. Burning coal is carbon that has been buried for millions of years and was out of circulation until we began to use it. This results in a rapid increase in the concentration of carbon dioxide in the atmosphere.

Solid Biomass: Wood, Charcoal, and Manure • Figure 13. 9 shows a picture of a charcoal market in the Philippines. Many people in developing countries rely on charcoal for cooking and heating. • Charcoal is lighter than wood and contains approximately twice as much energy per unit weight. A charcoal fire produces much less smoke than wood and does not need the constant tending of a wood fire.

Biofuels: Ethanol and Biodiesel • • Ethanol is an alcohol, the same one found in alcoholic beverages. It is made by converting starches and sugars from plant material into alcohol and carbon dioxide. 90% of the ethanol produces in the U. S. are corn-based, some other crops used are sugarcane, soybean and switchgrass. Flex-fuel vehicles can run on either gasoline or E-85. Biodiesel is a direct substitute for petroleum based diesel fuel. Biodiesel is typically diluted to “B-20, ” a mixture of 80% petroleum diesel and 20% biodiesel. B-20 is available at some gas stations scattered around the United States and can be used in any diesel engine.

The kinetic energy of water can generate electricity • Hydroelectricity generated by the kinetic energy of moving water. This is the second most common form of renewable energy in the world. • Figure 13. 12 shows a water impoundment hydroelectric dam. Arrows indicate the path of water flow.

Types of hydroelectric power systems • • • Run-of-the-river systems- water is held behind a dam and runs through a channel before returning to the river. Water impoundment- water is stored behind a dam and the gates of the dam are opened and closed controlling the flow of water. Tidal systems- the movement of water is driven by the gravitational pull of the Moon.

Advantages and Disadvantages of hydroelectric power. Advantages Nondepletable resources Low cost to run and operate Disadvantages Limited amount can be installed in any given area High construction costs Helps reduce flooding down stream. Threats to river ecosystem (dams block natural migration of fish) Recreational use such as boating, fishing, camping. Loss of habitat, agricultural land cultural heritage, can displace large numbers of people Can cause silt to build up above the dam

Passive Solar Heating • • Using passive solar energy can lower your electricity bill without the need for pumps or other mechanical devices. The sun can also be used to cook food. Figure 13. 16 shows a passive solar cooker. Residents of this refugee camp in Chad use solar cookers to conserve firewood and reduce the need to travel outside of camp.

Active Solar Energy Technologies • • Active solar energy- capturing the energy of sunlight with the use of a pump or photovoltaic cell and generating electricity. Figure 13. 17 shows a solar domestic hot water system. A nonfreezing liquid (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 sent back to the tank. Then the heat exchanger transfers the heat to water.

Active Solar Energy Technologies • Photovoltaic Systems capture energy from the Sun as light, not heat, and convert it directly into electricity. • Figure 13. 18 (a) shows a domestic photovoltaic system, photovoltaic solar panels convert sunlight into direct current (DC). An inverter converts DC into alternating current (AC), which supplies electricity to the house.

Active Solar Energy Technologies • • Concentrating Solar Thermal Electricity Generation. Concentrating solar thermal (CST) systems are a large-scale application of solar energy to electricity generation. Figure 13. 19 shows how a CST uses mirrors and reflectors to concentrate the Sun’s energy onto a “power tower, ” which uses the sunlight to heat water and make steam for electricity generation.

Advantages and Disadvantages of solar power. Advantages Disadvantages Nondepletable resources Manufacturing materials requires high input of metals and water After initial investment, no cost to harvest energy. Geographically limited and the sun doesn’t always shine Can be used to offset many applications in your home (heating space, heating water, electricity, ) High initial costs are often associated No plan in place to recycle old solar panels

• • Earth’s internal heat produces geothermal energy Geothermal energy- using the heat from natural radioactive decay of elements deep within Earth as well as heat coming from Earth. Largest geothermal producers are U. S. , China, and Iceland is on a divergent plate boundary which gives them access to molten rock near the surface. Iceland has vast amounts of geothermal resources and heats 87% of its homes this way.

• Earth’s internal heat produces geothermal energy Figure 13. 20 shows a ground source heat pump. By exchanging heat with the ground, a ground source heat pump can heat and cool a building using 30 to 70 % less energy than a traditional furnaces and air conditioners.

Advantages and Disadvantages of geothermal system. Advantages Disadvantages Nondepletable resources Emits hazardous gases and steam (depends on location) After initial investment, no cost to harvest energy. Geographically limited (Geothermal systems used to make electricity such as Iceland) Can be installed anywhere (ground source heat pumps) High initial costs are often associated

Wind energy is the most rapidly growing source of electricity • • Wind energy- using a wind turbine to convert kinetic energy into electrical energy. Figure 13. 22 shows how a wind turbine generates electricity. The wind turns the blade, which is connected to the generator, which generates electricity.

Wind energy is the most rapidly growing source of electricity • • Figure 13. 24 shows global growth of installed wind energy capacity. Worldwide, installed wind energy capacity is now almost 160 gigawatts (GW). Some of the most rapidly growing wind projects are offshore wind parks, clusters of wind turbines located in the ocean within a few miles of the coastline.

Advantages and Disadvantages of wind system. Advantages Disadvantages Nondepletable resources Turbines can be very noisy, wind doesn’t always blow. After initial investment, no cost to harvest energy. Deaths of birds and bats in migratory path Wind has a low up-front start up Geographically limited to windy cost areas near transmission lines Aesthetically displeasing to some people Storage batteries required for off-grid systems.

• • Hydrogen fuel cells have many potential applications Fuel cell- a device that operates like a common battery where electricity is generated by a reaction between two chemicals. The reaction happens in a closed container to which no additional materials can be added. Eventually the reactants are used up, and the battery goes dead. Supplying hydrogen is a challenge because free hydrogen gas is rare on Earth. Hydrogen tends to bond with other molecules. Producing hydrogen gas requires separating it from other molecules like water or natural gas. Electrolysis is when a electric current is applied to water to “split” it into hydrogen and oxygen.

Hydrogen fuel cells have many potential applications • Figure 13. 25 shows how a hydrogen fuel cell works. 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.

Advantages and Disadvantages of hydrogen fuel cells. Advantages Disadvantages Efficient Producing hydrogen is an energy-intensive process. Zero air emissions besides water vapor Lack of distribution network Hydrogen storage challenges

How can we plan our energy future? • • • A sustainable energy strategy must combine energy efficiency, energy conservation and the development of renewable and nonrenewable energy resources, taking into account the costs, benefits, and limitations of each one. In addition to investing in new energy sources, the U. S. will have to upgrade its existing electrical infrastructure – power plants, storage capacity, and distribution networks. Smart grid is an efficient, self regulating electricity distribution network that accepts any source of electricity and distributes it to end users.

How can we plan our energy future? • Figure 13. 26 shows a smart house. A smart grid optimizes the use of energy in the home by continuously coordinating energy use with energy availability.