Chapter 1 Introduction, Motivations, and the Balance Sheet PDF

GE Course in Sustainable Communities Lecture Note 1 Introduction, Motivations, and the Balance Sheet GTSU2015 Green Energy Innovation for Sustainable City...

GE Course in Sustainable Communities Lecture Note 1 Introduction, Motivations, and the Balance Sheet GTSU2015 Green Energy Innovation for Sustainable City 1 GTSU2015 Green Energy Innovation for Sustainable City Lecture Outline 1) Overview of energy use Introduction to the energy use in a city; Major issue and cause of global energy crisis; Environment impact of the energy problem 2) Solution to the global energy crisis Overview of different types of renewable energy; Examples of a sustainable city looking like 3) Balance Sheet Motivation behind a sustainable city; Approach of the balance sheet; Concept of energy and some working examples 2 GTSU2015 Green Energy Innovation for Sustainable City Lecture Outline 1) Overview of energy use Introduction to the energy use in a city; Major issue and cause of global energy crisis; Environment impact of the energy problem 2) Solution to the global energy crisis Overview of different types of renewable energy; Examples of a sustainable city looking like 3) Balance Sheet Motivation behind a sustainable city; Approach of the balance sheet; Concept of energy and some working examples 3 GTSU2015 Green Energy Innovation for Sustainable City Introduction: Brief History of Energy In ancient times, humans primarily relied on muscular and biomass sources for energy: Labor was powered by human effort. Transportation involved animals like horses and donkeys Cooking and heating were achieved through burning wood. As civilizations progressed, ancestral knowledge included harnessing energy from the sun and wind: Windmills and watermills were used for tasks like pumping water and grinding. The sun was utilized for processes like burning wood, heating, and drying. 4 GTSU2015 Green Energy Innovation for Sustainable City Introduction: Brief History of Energy The overall energy contribution from these sources was limited until the industrial revolution in the 18th century. During the mid-19th century, the industrial revolution marked a significant transition to coal as a primary energy source: Steam engines powered mechanical work. Coal was increasingly used in power plants to generate electricity. Even today, coal remains a predominant energy source for power plants, supplying energy to sustain human activities in urban centers. 5 GTSU2015 Green Energy Innovation for Sustainable City Global Energy Consumption Global Energy Consumption in 2020 Nowadays, electric power (36%) uses the largest share of energy consumption. In a city , electricity is one most use among other sectors, like industry (20%), transportation (30%), and residential & commercial (13%). Coa l 27 % Natural Gas Total energy consumption in 2020 24% is equal to 576 exajoules (×1018 J) 6 GTSU2015 Green Energy Innovation for Sustainable City Electricity Generation in a City What makes electricity in a city? Source of Electricity Generation in the world. 2020 Electricity is created by local power plant by a spinning generator Change of magnetic flux in a circuit to induce electrical current (Faraday’s Law) Types of power plants for energy generation Coal-fired power plant Diesel-fired power plant Source of Fossil fuels Gas-fired power plant Hydroelectric power plant Geothermal power plant Source: from bp (2021) Solar power plant Wind power plant Nuclear power plant 7 GTSU2015 Green Energy Innovation for Sustainable City How it Works: Fossil Fuel Power Plant Process of electricity generation Fossil fuel (coal, oil or gas) is transfer to furnace It is burned to create heat and boil water to produce steam for driving the turbine The turbine rotates to generate electricity The electrical power is step up before leaving the power station The water (from river, ocean or lake) cools down stream back into water These plants generate electricity reliably over long periods of time, and are generally cheap to build. 8 GTSU2015 Green Energy Innovation for Sustainable City Main Impact of Using Fossil Fuels Currently, fossil fuels (coal, oil, and gas) dominate as the main energy source (>60%) for human activities. Burning these fuels releases greenhouse gases (GHGs), especially CO2, leading to the greenhouse effect. To combat climate change, transitioning to alternative energy sources that are carbon-neutral is essential to reduce and stop these environmental impacts. Greenhouse gases (Unwanted) Electricity Chimney (Wanted) (Venting gases) Local power plant City 9 GTSU2015 Green Energy Innovation for Sustainable City More About Greenhouse Gases (GHGs) Carbon Dioxide (CO2) Atom Water (H2O) Methane (CH4) Nitrous Oxide (N2O) Ozone (O3) Greenhouse gases exist naturally in the Earth's atmosphere and play a crucial role in regulating the planet's temperature. However, human activities have significantly increased their concentrations in the atmosphere. 10 GTSU2015 Green Energy Innovation for Sustainable City Human-induced greenhouse gas emissions Data from sources like WRI, Ecofys, Among the GHGs emitted by human activities, and IEA are standardized to express CO2 is the primary contributor emissions as equivalent CO2. 11 GTSU2015 Green Energy Innovation for Sustainable City Historical Greenhouse Gases Emission Linear scale Increasing evidence links fossil fuel combustion to rising greenhouse gas levels. ppm = mg/L There is a clear rise in CO2 levels in the atmosphere and oceans. The accumulation of CO2 began notably during the industrial revolution, when fossil Natural flow in fuels became the dominant energy source. atmosphere Image result for climate change Year Log-scale 12 GTSU2015 Green Energy Innovation for Sustainable City Recent Global CO2 Emissions The changes in global CO2 emissions tend to align with fluctuations in the global economy. During financial crises or global disasters like COVID-19, CO2 emissions tend to decrease due to reduced economic activity and energy consumption. 13 GTSU2015 Green Energy Innovation for Sustainable City Regional Greenhouse Gases Emission Asia is a faster increase in CO2 emissions compared to other regions. More than half of global CO2 emissions come from Asia, with Europe, South America, and North America contributing ~38% collectively in 2022. Global Carbon Dioxide Emissions by Region, 1900–2022 Data source: OneWorld in Data 14 GTSU2015 Green Energy Innovation for Sustainable City ? Question: Regional Greenhouse Gases Someone mentioned that Asia, including China, has the highest CO2 emissions. Therefore, individuals in this region should take greater responsibility for reducing CO2 emissions. Do you agree Global Carbon Dioxide Emissions by Region, 1900–2022 with this stance? Why or why not? Data source: OneWorld in Data 15 GTSU2015 Green Energy Innovation for Sustainable City Regional Greenhouse Gas Emission It would be more meaningful and fairer to analyze the individual contribution. The highest green gas production (shaded area) is in Asia. But the highest green house gas production per person in North America. Global Carbon Dioxide Emissions by Region (Per person) 16 GTSU2015 Green Energy Innovation for Sustainable City Top Countries for Greenhouse Gas Emission Global Carbon Dioxide Emissions by Country, 1900–2022 Data source: EDGAR - Emissions database for Global Atmospheric Research Data source: OneWorld in Data 17 GTSU2015 Green Energy Innovation for Sustainable City Top Countries for Greenhouse Gas Emission Source: IEA data from IEA The countries with the highest CO2 emissions are oil-producing nations in the Middle East, far exceeding the average individual emissions of 4.3 tons/yr. 18 GTSU2015 Green Energy Innovation for Sustainable City Global Temperature Rise The average global temperature has been risen about 1.2 °C compared to 50 years ago. On land, temperatures have risen about twice as fast as the global average. A prediction on the average temperature change is 3 oC after 50 years. Source: NASA’s Scientific Visualization Studio Source: IPCC AR6 WGI, Source: Hadley Centre HadCM3 climate model 19 GTSU2015 Green Energy Innovation for Sustainable City Impacts of Ocean Warming Rising ocean temperatures Affect marine species and ecosystem Loss of coastal protection Cause more extreme weather events Threatening food security Source: Explaining ocean warming Causes, scale, effects and consequences (Full report), Switzerland IUCN. We need to limit the global average temperature increase to well below 1.5°C above pre-industrial levels, which is crucial to prevent the massive, irreversible impacts of ocean warming on marine ecosystems. (Paris Agreement on climate change) 20 GTSU2015 Green Energy Innovation for Sustainable City How to Deal with the Current Issue Therefore, a shift towards other energy sources that do not release CO2 into the atmosphere At the 2021 Climate Change Conference (COP26), 190 countries agreed to phase out coal-fired power and declared to achieve net carbon zero at 2050. 21 GTSU2015 Green Energy Innovation for Sustainable City Lecture Outline 1) Overview of energy use Introduction to the energy use in a city; Major issue and cause of global energy crisis; Environment impact of the energy problem 2) Solution to the global energy crisis Overview of different types of renewable energy; Examples of a sustainable city looking like 3) Balance Sheet Motivation behind a sustainable city; Approach of the balance sheet; Concept of energy and some working examples 22 GTSU2015 Green Energy Innovation for Sustainable City Renewable Energy Sources R Perez et al., The IEA SHC Solar Update 50 (2) 2009. What is “Renewable Energy”? -Clean and safe energy sources; -Abundantly in nature and sustainably refill themselves; -No green house gases production. Six Major Renewable Energy Sources: (1) Solar Energy; (2) Wind Energy; (3) Geothermal Energy; (4) Hydroelectric Energy; (5) Tide and Wave Energy (6) Biomass Energy 23 GTSU2015 Green Energy Innovation for Sustainable City Solar Energy Solar power is the energy from sun The Sun produces energy by nuclear fusion for 4 billion years and will continue to do so for another 5 billion years. Solar energy is effectively inexhaustible. Energy from the Sun enters Earth’s atmosphere as light and heat. The composition of sunlight at the top of the Earth’s atmosphere is roughly 50% infrared radiation (heat), 40% visible light and 10% ultraviolet radiation (solar spectrum UV-vis-IR). 24 GTSU2015 Green Energy Innovation for Sustainable City Types of the Solar Power System Grid-connected system Standalone system Solar system is connected to the Standalone solar system operates utility grid (on-grid). independently from the power grid Large-scale solar farms (off-grid). Homeowner solar panels under a Rooftop standalone solar panels Feed-in Tariff (FiT) scheme. directly supply electricity to household appliances. 25 GTSU2015 Green Energy Innovation for Sustainable City Global Solar Irradiance Most country is lying in between the global mean solar irradiance >150W/m2. Minimum solar insolation required to generate electricity is 100 -200 W/m2, which sufficient to run at least one light and fan. 26 GTSU2015 Green Energy Innovation for Sustainable City Wind Energy Wind is air in motion. Wind energy is the energy obtained from the force of the wind. Wind Energy (E) and Wind power (P) depend on the wind speed v (e.g. 𝐸 ∝ 𝑣2 and 𝑃 ∝ 𝑣3). Wind energy can be harvested to generate mechanical power or electricity. 27 GTSU2015 Green Energy Innovation for Sustainable City Where Does the Wind Come From? Formation of wind in the earth Solar radiation heats every part of the surface of the earth unevenly because of different formations of the earth’s surface, including land and water and rotation of the earth. Winds are caused by temperature and pressure differences across the Earth’s surface, examples are sea breezes and land breezes. The kinetic energy in the wind comes from the sun (Air density: High) (Air density: Low) 28 GTSU2015 Green Energy Innovation for Sustainable City Harvesting the Wind Energy Wind turbines extract energy from the wind and convert it to electricity. Wind turbine blades are designed in a similar way to an airplane wing to extract as much energy as possible 29 GTSU2015 Green Energy Innovation for Sustainable City Global Wind Speed The global average wind speed (at 10m height) over the ocean and over the land are 6.64 m/s (class 6) and 3.28 m/s (class 1) from measurements, respectively. The calculated average values (at 80m height) are 8.60 m/s (class 6) and 4.54 m/s (class 1) over ocean and land, respectively. Area with wind speed within 5-13 m/s is good for wind harvesting by wind turbine. 30 GTSU2015 Green Energy Innovation for Sustainable City Hydro Energy Kerr Dam (Montana, USA) Hydropower is the renewable energy obtained by water falling from high ground to low ground (potential). 31 GTSU2015 Green Energy Innovation for Sustainable City Harvesting the Hydro Energy The hydro energy can be extracted by the falling or fast-running water via the mechanical turbine to produce electricity. Hydraulic energy depends on the height and flow the 32 GTSU2015 Green Energy Innovation for Sustainable City Where is the Flowing Water Come From? Earth’s water cycle: The sun evaporates water from rivers and the sea. Water vapor rises in the atmosphere and forms clouds, which then cause rain. Rainfall collects at high altitudes and can be used to drive hydraulic turbines as it flows down to the sea. The turbines extract potential energy, which is converted to electricity. The kinetic energy of the flowing water comes from the sun 33 GTSU2015 Green Energy Innovation for Sustainable City Flowing Water for Hydropower 1) All water (The largest sphere) - It represents all of Earth's water, including all of the water in the oceans, ice caps, lakes, rivers, groundwater, atmospheric water, and 1,386,000,000 km3 even the water in you, your dog, and your (Dia: 1384 km) tomato plant etc. 2) Liquid fresh water (The second large sphere) 10,633,450 km3 (Dia: 272.8 km) - It represents groundwater, lakes, and rivers. - 99% of liquid fresh water is groundwater, much of which is not accessible. 93,113 km3 3) Water in lakes and rivers (The smallest sphere) (Dia: 56.2 km) - Most of the water people and life of earth need every day comes from these surface-water sources. - 1% of the liquid fresh water, which is accessible to humans. Hydropower uses water in lakes and rivers Source: USGS 34 GTSU2015 Green Energy Innovation for Sustainable City Global Average Precipitation Robert Moses Niagara Dam (New York, US) Sayano-Shushenskaya dam (Russia) The Grand Coulee Dam (Washington, US) The Three Gorges Dam (Hubei, China) Itaipu Dam (Brazil) Location of the world’s largest hydropower plant The site of a hydroelectric power plant should accommodate a large catchment area*, steep gradients for a good potential head, high average annual rainfall throughout the year, a suitable location for the building of storage or reservoir dams. (*Catchment area: the area from which rainfall flows into a river, lake, or reservoir) 35 GTSU2015 Green Energy Innovation for Sustainable City Biomass Energy Biomass energy is the energy generated or produced by living or once-living organisms. The most common biomass materials used for energy are plants, such as corn and soy, etc. The energy from these organisms can be burned to create heat or converted into electricity. 36 GTSU2015 Green Energy Innovation for Sustainable City Why Biomass is renewable? The principle of renewable biomass energy: Biomass absorbs energy from the sun and carbon from the atmosphere Biomass can be used as a fuel for combustion Or can be converted to liquid and gaseous fuels for transportation But it is only renewable if the biomass is regrown in a short time convert carbon dioxide and water into nutrients (carbohydrates) 37 GTSU2015 Green Energy Innovation for Sustainable City Traditional Biomass Traditional biomass provides 6% of the world’s primary energy 1.3 billion people (18% of the world population) have no access to electricity 2.7 billion people (38% of the world population) use traditional biomass for heating and cooking, especially in developing country Traditional biomass is mainly wood, traditional charcoal and animal waste collected by hand 38 GTSU2015 Green Energy Innovation for Sustainable City Modern Biomass Biomass for power generation Energy crops for biofuels 39 GTSU2015 Green Energy Innovation for Sustainable City Fossil Fuels are Renewable Energy? The formation of fossil fuels 40 GTSU2015 Green Energy Innovation for Sustainable City Fossil Fuels vs Sustainable Biomass The difference between fossil fuels and sustainable biomass Fossil fuels Coal, oil and gas formed from biomass over hundreds of millions of years The biomass absorbed carbon from the atmosphere and slowly formed underneath the ground layers High temperatures and pressures gradually transformed the biomass into coal, oil and natural gas The coal we use in one year probably took one million years to form so we are releasing carbon dioxide much faster than it was absorbed Sustainable Biomass Biomass does not contributes with CO2 concentration in the atmosphere, which is considered to neutral The CO2 is taken from the atmospheric air and converted in biomass, then it is returned to the atmospheric air from the combustion, like a cycle. Must be replaced with new growth over the same timescale that it is used 41 GTSU2015 Green Energy Innovation for Sustainable City Ocean Energy (Waves and Tides) Ocean energy refers to all forms of renewable energy derived from the sea. There are three main types of ocean technology: wave, tidal and ocean thermal. 42 GTSU2015 Green Energy Innovation for Sustainable City Formation of Tides in the Earth Interaction between earth, moon and sun Spring tide (Sun and moon in line) Neap tide (Sun and moon at 90 degC) Gravitational forces between the Earth, Moon and Sun raise the sea level on each side of the Earth to form tidal The Earth rotates within the tidal bulge and so we see two high and two low tides per day We can use hydraulic turbines to extract energy from the rise and fall of the tides Video: https://www.youtube.com/watch?v=M3hAhNsyf7k Reference: https://www.nationalgeographic.org/media/earths-tides 43 GTSU2015 Green Energy Innovation for Sustainable City Global Tidal Resources Annual Tidal Range *Note: local effects can produce tides >10m Factors to affect the tidal: 1) Astronomical: Distance and position of Moon and Sun; 2) Local topography: e.g. shape of shoreline, bays and funnel-shaped bays increase tidal magnitude; 3) Weather: Strong Wind / low atmospheric pressure raise sea levels 44 GTSU2015 Green Energy Innovation for Sustainable City Harvesting the Tidal Energy Tidal stream Tides are full of energy due to their motion. This energy is harnessed with the use of special devices, such as tidal turbines to generate electricity or mechanical power. Barrages General types of technology: 1) Tidal streams; 2) Barrages; 3) Tidal lagoons 45 GTSU2015 Green Energy Innovation for Sustainable City Formation of Wave Source: Handbook of Ocean Wave Energy Generally, waves are generated by wind blowing across the surface of the ocean (converted wind energy to wave energy). In some special case, such as earthquakes, that causes tsunamis which could also legitimately be called waves. 46 GTSU2015 Green Energy Innovation for Sustainable City Global Wave Energy Resource In the southern hemisphere, there is the greatest annual resource for the wave energy. Because there is a greater expanse of open water in the southern hemisphere. 47 GTSU2015 Green Energy Innovation for Sustainable City Global Wave Energy Resource Best area for wave energy Wave gather wind energy over vast ocean areas and transport it to the coasts. 48 GTSU2015 Green Energy Innovation for Sustainable City Harvesting the Ocean Wave Power Absorbers Attenuators Oscillation water columns Five main types of technology 1) Absorbers; 2) Attenuators; 3) Oscillation water columns; 4) Overtopping; and 5) Inverted- Pendulum device 49 GTSU2015 Green Energy Innovation for Sustainable City Geothermal energy What is Geothermal Energy? Geothermal energy is harvested from heat sources deep within the Earth. It serves as a primary energy source, directly providing heat or generating electricity. Heat energy sources: The Earth retains a significant amount of heat from its formation Radioactive decay of elements like Uranium and Thorium contributes to a substantial portion of the Earth's internal heat. 50 GTSU2015 Green Energy Innovation for Sustainable City Geothermal Energy near the Earth Surface The heat is concentrated at the edges of tectonic plates. Example: The western United States is a part of the Ring of Fire, so more heat is brought to the Earth’s surface in states like Nevada and California. That is where you will find all of the current geothermal power plants in the U.S. 51 GTSU2015 Green Energy Innovation for Sustainable City Geothermal Energy near the Earth Surface The tectonic plates are pieces of the Earth’s crust that fit together like a jigsaw puzzle. Over time, the plates move and grind up against with each other, leading to volcanic and earthquake activity on their edges, like in California and Japan. Example: New Zealand lies at the edge of both the Australian and Pacific tectonic plates. Tectonic movement brings geothermal close to the surface where it can be used for power generation or heating. 52 GTSU2015 Green Energy Innovation for Sustainable City Harvesting the Geothermal Energy In order to harness the geothermal energy present deep within the Earth, three essential components are required: (1) a heat source, (2) fluid, and (3) permeability. Permeability refers to the capacity of a material to enable the passage of fluids, typically through fractures or interconnected holes within the material, thereby creating pathways through the rock. 53 GTSU2015 Green Energy Innovation for Sustainable City Krafla Geothermal Power Plant in Iceland The largest power station in Iceland Located close to the Krafla Volcano and the lake Mývatn With 33 boreholes to produce 500 GWh of electricity annually 54 GTSU2015 Green Energy Innovation for Sustainable City Nuclear Power Nuclear power is to use of nuclear reactions to produce electricity Doel Nuclear Power Plant (Belgium) Nuclear reactions can be nuclear fission, nuclear decay and nuclear fusion. The majority of nuclear power plant is by nuclear fission of uranium and plutonium 55 GTSU2015 Green Energy Innovation for Sustainable City How the Nuclear Power Works Nuclear reactor is a house to control the nuclear fission of the splitting of uranium atoms. This process generates heat energy to turn water into steam, which triggers the turbine to rotate and generate electricity. Source: U.S. Department of Energy The nuclear power plants do not burn fossil fuels, which has no carbon emissions. It can provide reliable power 24 hours a day, but the safety is still a concern. 56 GTSU2015 Green Energy Innovation for Sustainable City Nuclear Power Plants in China China has the largest program of nuclear power construction in the World. At 2021, the power capacity reaches 49.6GW from 50 reactors while additional 17.1GW under construction. But, even when complete, nuclear power will still supply 5-6% of its electricity. More long-term plans for future capacity is 120-150GW by 2030. 57 GTSU2015 Green Energy Innovation for Sustainable City Daya Bay Nuclear Power Station Start to operate at 1994 Located 50km apart from Hong Kong (Dapeng New Area, Shenzhen) Electricity import which is ~25% to the Hong Kong electricity consumption 58 GTSU2015 Green Energy Innovation for Sustainable City Examples of Sustainable Cities Use of renewable energy sources; Reduce dependence on fossil fuels; Achieve carbon-neutrality… 59 GTSU2015 Green Energy Innovation for Sustainable City Example of Sustainable Cities in the World Reykjavik, Iceland 100% renewable electricity Renewable Energy Sources: Reykjavik is powered almost entirely by renewable energy sources such as geothermal (26.8%) and hydropower (73%). District Heating: Utilizes geothermal energy for district heating, reducing reliance on fossil fuels for heating purposes. Source: https://www.visiticeland.com/article/renewable-energy/ 60 GTSU2015 Green Energy Innovation for Sustainable City Example of Sustainable Cities in the World Adelaide, Australia 100% renewable electricity Renewable Energy Sources: Adelaide has successfully sourced 100% of its power from a blend of wind and solar energy. The city has made substantial investments in renewable energy, especially solar power, leading to a surge in rooftop solar installations. This transition to cleaner energy sources is actively reducing Adelaide's carbon footprint. Source: https://www.cityofadelaide.com.au 61 GTSU2015 Green Energy Innovation for Sustainable City Example of Sustainable Cities in the World Burlington, USA 100% renewable electricity Renewable Energy Sources: Burlington became the first US city to power itself entirely with renewable sources starting in 2014. They use a diverse mix of wind, solar, hydropower, and biomass for electricity generation. Transportation: It also encourages eco-friendly transportation with public transit, bike lanes, and backing for electric vehicles to cut CO2 emissions from transport. Source: https://www.cdp.net/en/articles/cities/burlington-100-renewable-electricity-city 62 GTSU2015 Green Energy Innovation for Sustainable City Other Cities on the way to Sustainable Copenhagen, Denmark Aim to be world’s first carbon-neutral city by 2025 Carbon neutral: GHG emissions are offset by reduction them elsewhere Renewable Energy: Copenhagen has invested significantly in renewable energy sources such as wind power, district heating systems, and biomass. By shifting away from fossil fuels and towards renewables. Carbon Reduction: Encourage public transit, electric vehicles and promotes energy-efficient building designs and renovations to reduce energy consumption. Source: https://carbonneutralcities.org/cities/copenhagen/ 63 GTSU2015 Green Energy Innovation for Sustainable City Lecture Outline 1) Overview of energy use Introduction to the energy use in a city; Major issue and cause of global energy crisis; Environment impact of the energy problem 2) Solution to the global energy crisis Overview of different types of renewable energy; Examples of a sustainable city looking like 3) Balance Sheet Motivation behind a sustainable city; Approach of the balance sheet; Concept of energy and some working examples 64 GTSU2015 Green Energy Innovation for Sustainable City The Balance Sheet Currently, the world heavily relies on unsustainable fossil fuels for energy consumption. This practice is not sustainable. When building sustainable cities, a key question emerges: “Can we shift away from fossil fuels to achieve sustainability?” The subsequent crucial step involves estimating the potential of renewable energy sources available to us. This assessment is vital as we compare it with our current energy consumption derived from fossil fuels from the balance sheet. 65 GTSU2015 Green Energy Innovation for Sustainable City The Balance Sheet In this course, we will analyze the potential for sustainability using UK cities as examples. Energy Consumption Energy Production (per person) (per person) How much energy we need for our living style? How much energy we could produce if we get off fossil fuel? 66 GTSU2015 Green Energy Innovation for Sustainable City Two Scenarios in Balance Sheet Desirable outcome: Energy Energy Consumption Production The energy consumption is much less than conceivable sustainable production. We can live sustainably by using the renewable energy sources; Then we can start to look into the economic, social, and environmental costs of the using sustainable alternatives. 67 GTSU2015 Green Energy Innovation for Sustainable City Two Scenarios in Balance Sheet Bleak scenario: Energy Energy Consumption Production The energy consumption is much more than conceivable sustainable production. It doesn’t matter economics comes into the equation. There’s simply not enough sustainable power to support our existing lifestyle. We must have a massive change in our lifestyle to suppress our energy consumption. 68 GTSU2015 Green Energy Innovation for Sustainable City Prefix Multipliers Multiplier Kilo (k) × 1,000 (= ×103) Mega (M) × 1,000,000 (= ×106) Giga (G) × 1,000,000,000 (= ×109) Tera (T) × 1,000,000,000,000 (= ×1012) Peta (P) × 1,000,000,000,000,000 (= ×1015) Exa (E) × 1,000,000,000,000,000,000 (= ×1018) For example: 1,000,000,000 g (grams) It can be expressed as 1 Gg (gigagram) or 1,000 Mg (Megagrams) or 1,000,000 kg (kilograms). 69 GTSU2015 Green Energy Innovation for Sustainable City The Units of Energy and Power Energy (How much energy used) In physics, the unit of energy is in joules (J) Commercially, kilowatt-hour (kWh) is used as the unit of energy, e.g. electricity bills The unit “kWh” doesn’t mean that the energy was used in one hour’. It means about how much energy it used, not how fast it used. Power (How fast energy used) Formula: In physics, the unit of power is in Watt (W) Power = Energy ÷ Time In this course, we will use “kWh/day” as a convenient “human” unit For example, a power of 40Watt light bulb can be expressed as 1kWh/d 24h e.g. 40W = 40W × ≈ 1000 Wh/d = 1 kWh/d 1d Both numerator and denominator are multiplied by 1d (= 24h) 70 GTSU2015 Green Energy Innovation for Sustainable City The Units of Energy and Power In this course, we usually quote powers in “kWh/d per person”. It is much easier to compare with a country to other countries. E.g. UK waste incineration delivers a power of 7 TWh per year and Denmark’s waste incineration delivers 10 TWh per year. Does this help us say whether Denmark incinerates “more” waste than the UK? Actually, it just tells the total power consumption. We usually want to know is the waste incineration per person Energy : kWh per person Power : kWh/d per person 71 GTSU2015 Green Energy Innovation for Sustainable City  GE Course in Sustainable Communities Lecture Note 2 Energy Usage and Production I GTSU2015 Green Energy Innovation for Sustainable City 1 GTSU2015 Green Energy Innovation for Sustainable City Lecture Outline 1) Energy Consumption by Vehicles Energy usage in a car Energy consumption in different driving scenario Car vs bicycle Estimation of car energy usage in UK Estimation of transportation energy usage in HK 2) Energy Production by Wind The formation of wind and wind circulation Characteristics of wind Wind Power and wind turbine efficiency Estimation of wind energy production in UK 3) Emerging Wind Turbine Technologies 2 GTSU2015 Green Energy Innovation for Sustainable City Lecture Outline 1) Energy Consumption by Vehicles Energy usage in a car Energy consumption in different driving scenario Car vs bicycle Estimation of car energy usage in UK Estimation of transportation energy usage in HK 2) Energy Production by Wind The formation of wind and wind circulation Characteristics of wind Wind Power and wind turbine efficiency Estimation of wind energy production in UK 3) Emerging Wind Turbine Technologies 3 GTSU2015 Green Energy Innovation for Sustainable City Energy Usage in a Car Petroleum-based fuels (e.g. gasoline, diesel etc.) is major energy source to supply a car when driving Major Energy Consumption: 1. Engine Fuel energy going to wheel is only 20-30%, which is the energy makes the car move. 2. Pedal on (move) and braking (stop) 3. Air resistance 4. Rolling resistance Image result for Rolling Resistance Image result for Pedal on and braking Image result for Air resistance 4 GTSU2015 Green Energy Innovation for Sustainable City How a Car Engine Works Internal Combustion Engine A typical car engine converts energy from the heat (by burning gasoline) into mechanical work (or called torque which applies to make wheels rolling). The Four Strokes in an Engine (1) Intake - Air-fuel mixture to the chamber (2) Compression - Air-fuel mixture is compressed (3) Power - Explosion makes piston down (4) Exhuast - Piston pushes out burned gases ***Most cars are powered by a 4 or 6 cylinder engine, while most trucks have a 6 or 8 cylinder. 5 GTSU2015 Green Energy Innovation for Sustainable City Energy Flow in a Gasoline Vehicle Wheel energy goes to: Pedal on/ braking + Air resistance + Rolling resistance Source: FuelEconomy.gov Engine Losses: Thermal energy losses to the cooling system and exhaust gases. Parasitic Losses: Energy used by power ancillary systems and components (e.g., engine accessories, cooling system, brake system, transmission fluid pump, etc.). Drivetrain Losses: Energy losses from the engine to the wheels through mechanical components (e.g., bearings, driveshafts, axles, gearbox, etc.). Auxiliary Electricity: Power for essential systems like air conditioning, heating, electronics, and engine operation. 6 GTSU2015 Green Energy Innovation for Sustainable City Energy Efficiency in Different Vehicles Apart from Gasoline vehicle, there are two more typical types of vehicles, e.g. sole electric vehicle and hybrid vehicle (operated by both electric motor and gasoline engine). Electric vehicles are much more energy efficient and the need of electricity (replace fossil fuels) in the transportation sector might be important. The typical fuel-energy efficiency of a car ranges from 19% to 34%. For gasoline vehicle, we use an average efficiency of 25% for our calculations during class. Fuel-energy efficiency in different vehicle types Next Gen Technology Current Technology Source: Toyota 7 GTSU2015 Green Energy Innovation for Sustainable City ? Question: Energy Flow in an Electric Vehicle Source: FuelEconomy.gov In an electric vehicle, the efficiency from battery energy to wheel energy is around 90%. Why do car manufacturers typically state that the overall efficiency is only 30-35%, as seen in the Toyota table on the previous page? 8 GTSU2015 Green Energy Innovation for Sustainable City ? Question: Energy Flow in an Electric Vehicle Source: FuelEconomy.gov In fossil fuel power plant Grid-to-wheel efficiency: Fossil fuel → Electricity 33-34.5% (Typically efficiency 38%) 9 GTSU2015 Green Energy Innovation for Sustainable City Energy Usage in a Car Petroleum-based fuels (e.g. gasoline, diesel etc.) is major energy source to supply a car when driving Major Energy Consumption: 1. Engine Fuel energy going to wheel is only 20-30%, which is the energy makes the car move. 2. Pedal on (move) and braking (stop) 3. Air resistance 4. Rolling resistance Image result for Rolling Resistance Image result for Pedal on and braking Image result for Air resistance 10 GTSU2015 Green Energy Innovation for Sustainable City Energy Flow in a Gasoline Vehicle Wheel energy goes to: Pedal on/ braking + Air resistance + Rolling resistance Source: FuelEconomy.gov Let's begin estimating the energy used for accelerating (pedal on) and braking (brake applied) as the car moves and comes to a stop. 11 GTSU2015 Green Energy Innovation for Sustainable City Energy to brake In a simple case, let's assume there is no air resistance or road friction. Speed of an object Basic formula: 1 Kinetic energy = 𝑚𝑣 2 2 Mass of an object (Weight in earth) v=0 v=0 When a vehicle accelerates rapidly from rest (v = 0) to a specific speed v and maintains this speed over a distance d, the car will possess kinetic energy represented as: 1 K.E. of the car = 𝑚𝑐 𝑣 2 2 When the driver applies the brakes, all of the car's kinetic energy is converted into heat within the brakes*. (*This vehicle doesn’t have fancy regenerative braking) 12 GTSU2015 Green Energy Innovation for Sustainable City Power to brake Basic formula: Distance (𝑑) Speed (𝑣) = Time (𝑡) v=0 For each braking event occurring at a distance d between traffic lights, stop signs, or congestion events, the power loss due to braking can be calculated as: 1 1 Energy (Kinetic energy) 2𝑚𝑐 𝑣 2 2𝑚𝑐 𝑣 3 Rate of Energy = = Τ = Time 𝑑 𝑣 𝑑 (Power to brakes) Power in braking is proportional to the mass of the car, the cubic of the speed and inversely proportional to the travel distance. Upon resuming movement, the acceleration restores kinetic energy to the car; braking dissipates that kinetic energy again. 13 GTSU2015 Green Energy Innovation for Sustainable City Air resistance In reality, the atmosphere contains air particles. When a car is moving and maintains a cruising speed v, the air particles also move at the same speed v but in the opposite direction, creating resistance against the car's movement. Consider the car movement generates a tube of air current with: - The cross-sectional area A, or called the effective cross-sectional area A - Swirling at a speed v. v v Air particle Source: https://www.youtube.com/watch?v=HTOl0lTet9A To sustain the car's movement at speed v, some energy from the car is dissipated due to air resistance. 14 GTSU2015 Green Energy Innovation for Sustainable City Effective area of a car front Smaller effective area Larger effective area A = 𝑐𝑑 𝐴𝑐𝑎𝑟 The ratio of the air tube’s effective cross-sectional area A to the frontal car area Acar is called the drag coefficient cd. For a streamlined car, the effective area A is usually smaller and therefore has a smaller air resistance. 15 GTSU2015 Green Energy Innovation for Sustainable City Power to Air Resistance Volume of air tube Basic formula: Volume of V = Avt the tube Mass = Density × Volume (Mass of Air) v Air density ρ Air particle For this distance d traveled, the kinetic energy and the power of the swirling air within the air tube is: 1 1 1 Kinetic energy = 𝑚𝑎 𝑣 = 𝜌𝐴𝑣𝑡 𝑣 = 𝜌𝐴𝑡𝑣 3 2 2 2 2 2 1 Energy (Kinetic energy) 2𝜌𝐴𝑡𝑣 3 1 Rate of Energy = = = 𝜌𝐴𝑣 3 Time 𝑡 2 (Power to air resistance) Power to air resistance is proportional to the density of air, effective area of the car, and the cubic of the speed. 16 GTSU2015 Green Energy Innovation for Sustainable City Car energy usage Rate of energy production by car = 4 × (Rate of energy to brakes + Rate of energy to swirling air) Typical petrol engines are about Power to the brakes: Power to air resistance: 1 1 25% efficient. Three quarters is 𝑚𝑐 𝑣 3 𝜌𝐴𝑣 3 wasted in making the car’s engine 2 2 𝑑 and radiator hot, and just one quarter goes into “useful” energy 1 𝑚𝑐 𝑣 3 1 *Total power consumption by a car = 4 2 + 𝜌𝐴𝑣 3 𝑑 2 The total power consumption of a car depends on the mass of the car mc, the car speed v, the air density 𝜌, the effective front area A and the travel distance d. *We ignore the rolling resistance in the calculation and will discuss it later on. 17 GTSU2015 Green Energy Innovation for Sustainable City Note: Assumptions for this equation 1 𝑚𝑐 𝑣 3 1 *Total power consumption by a car = 4 2 + 𝜌𝐴𝑣 3 𝑑 2 Assumption 1: The car engine efficiency remains constant at different car speeds. ❖ In a real car engine, the efficiency reaches its peak within an optimal speed range. The optimal speed typically ranges from 40 km/h to 100 km/h. If the car speed is too low, for instance, at 20 km/h, the car engine efficiency drops significantly, with large impact to the factor of 4, resulting in increased power consumption. Conversely, if the car speed is too high, the car engine efficiency drops slightly, with no substantial impact on the factor of 4. Assumption 2: The rolling resistance is ignored. In the high-speed range, resistance becomes insignificant. 18 GTSU2015 Green Energy Innovation for Sustainable City Dependence of power on speed 1 𝑚 𝑣3 1 2 𝑐 Total power consumption by a car = 4 + 𝜌𝐴𝑣 3 𝑑 2 Rearranging the formula: 3 𝑚𝑐 Total power consumption by a car = 2𝑣 + 𝜌𝐴 𝑑 Obviously, the formula has the multiplier of cube of speed v3. (Both forms of energy dissipation scale as v3) What does it implies? If a driver who halves his speed v for a same distance journey, it can make the power consumption 8 times smaller. But the journey will take twice as long. 19 GTSU2015 Green Energy Innovation for Sustainable City Dependence of power on speed The figure shows the powers of cars (kW) versus their top speeds (km/h). Both scales are logarithmic. The power increases as the third power of the speed. To go twice as fast requires eight times as much engine power. E.g. Speed: 150km/h → Power: ~25kW Speed: 300km/h → Power: ~200kW Halving your driving speed can reduce fuel consumption (in miles per gallon) to one quarter of current levels 20 GTSU2015 Green Energy Innovation for Sustainable City Dominant power 1 𝑚 𝑣3 1 2 𝑐 Total power consumption by a car = 4 + 𝜌𝐴𝑣 3 𝑑 2 Rearranging the formula: 3 𝑚𝑐 Total power consumption by a car = 2𝑣 + 𝜌𝐴 𝑑 1st term: 2nd term: Power to the brakes Power loss to air resistance Which power loss is dominant? 𝑚𝑐 ൗ𝑑 It depends on the ratio: 𝜌𝐴 If the ratio is larger than 1, then it is braking dominant. If the ratio is smaller than 1, then it is stirring-air dominant (also known as drag-dominant). 21 GTSU2015 Green Energy Innovation for Sustainable City Special distance, d*, between stops We can work out a special distance d∗ between stop signs when the dissipation ratio of power loss in braking to the power loss in air-swirling is equal to 1. 𝑚𝑐 ൗ𝑑∗ =1 𝜌𝐴 If the frontal area of the car is 3m2 (2m wide x 1.5m height) and the drag coefficient is cd = 1/3 and the mass is mc = 1000 kg, then the special distance d∗ is: ∗ 𝑚𝑐 1000 kg 𝑑 = = = 750 m 𝜌𝐴 1.3 kg/m3 ×(1ൗ × 3 m2 ) 3 (Typical car in UK: A = cd Acar = 1 m2; mc=1000 kg) 22 GTSU2015 Green Energy Innovation for Sustainable City Urban driving For city driving, it is braking-dominated by kinetic energy and braking if the distance between stops is less than 750m. 𝐶𝑎𝑛 𝑏𝑒 𝑛𝑒𝑔𝑙𝑒𝑐𝑡𝑒𝑑 1 𝑚𝑐 𝑣 3 1 Total power consumption of car = 4 2 + 𝜌𝐴𝑣 3 𝑑 2 For a smart-driving in city, you can save the energy of the car by 1. Reducing the mass of your car; 2. Getting a car with regenerative brakes (which roughly halve the energy lost in braking) Image result for Urban driving traffic lights 3. Driving more slowly. 23 GTSU2015 Green Energy Innovation for Sustainable City Highway driving For highway-driving, it is drag-dominated by air-swirling if the distance between stops is more than 750m. 𝐶𝑎𝑛 𝑏𝑒 𝑛𝑒𝑔𝑙𝑒𝑐𝑡𝑒𝑑 1 𝑚 𝑣3 1 2 𝑐 Total power consumption of car = 4 + 𝜌𝐴𝑣 3 𝑑 2 Under this situation, it doesn’t much matter what your car weighs. Energy dissipation will be much the same whether the car contains one person or six. Energy dissipation can be reduced by 1. Reducing the car’s drag coefficient; Image result for Highway driving 2. Reducing its cross-sectional area; 3. Driving more slowly. * Drive slower on highway only if safety permits. 24 GTSU2015 Green Energy Innovation for Sustainable City Car vs Bicycle What’s the energy consumption of a bicycle, in kWh per 100km in a highway? Consider this is an air-swirling mode in a car first, the power-consumption is: 1 Total power consumption by a car = 4 × 𝜌𝐴𝑣 3 2 Basic formula: Energy (𝐸) Based on the power, the energy consumed by a Power (𝑃) = Time (𝑡) car, per distance travelled is: 1 𝑡 Distance (𝑑) Energy per distance by a car = 4 × 𝜌𝐴𝑣 × 3 Speed (𝑣) = 2 𝑑 Time (𝑡) 1 1 = 4 × 𝜌𝐴𝑣 3 × 2 𝑣 1 = 4 × 𝜌𝐴𝑣 2 2 The “4”came from engine inefficiency; ρ is the density of air; the area A = cdAcar is the effective frontal area of a car; and v is its speed. 25 GTSU2015 Green Energy Innovation for Sustainable City Car vs Bicycle What’s the energy consumption of a bicycle, in kWh per 100km in a highway? No engine is applied in bicycle, We can use a similar way to calculate the power and it is assumed that our muscle efficiency is 100%. consumption on bicycle as: 1 Total power consumption by a bicycle = 𝜌𝐴𝑣 3 2 Basic formula: Energy (𝐸) Based on the power, the energy consumed by a Power (𝑃) = Time (𝑡) bicycle per distance travelled is: 1 3 𝑡 Distance (𝑑) Energy per distance by a bicycle = 𝜌𝐴𝑣 × Speed (𝑣) = 2 𝑑 Time (𝑡) 1 1 = 𝜌𝐴𝑣 3 × 2 𝑣 1 = 𝜌𝐴𝑣 2 2 ρ is the density of air; the area A = cdAbicycle is the effective frontal area of a bicycle; and v is its speed. 26 GTSU2015 Green Energy Innovation for Sustainable City Car vs Bicycle Comparing the drag coefficient, the frontal area and the speed, we get obtain the difference of energy per distance between a car and a bicycle. 1 Energy per distance by a car = 4 × 𝜌𝑐𝑑𝑐𝑎𝑟 𝐴𝑐𝑎𝑟 𝑣𝑐𝑎𝑟 2 2 1 𝑏𝑖𝑐𝑦𝑐𝑙𝑒 2 Energy per distance by a bicycle = 𝜌𝑐𝑑 𝐴𝑏𝑖𝑐𝑦𝑐𝑙𝑒 𝑣𝑏𝑖𝑐𝑦𝑐𝑙𝑒 2 Assume the bike is not very well streamlined: Assume that the area ratio is: Image result for power consumption of bicycle 𝑐𝑑𝑏𝑖𝑘𝑒 1 𝐴𝑏𝑖𝑘𝑒 1 = = 𝑐𝑑𝑐𝑎𝑟 1Τ 𝐴𝑐𝑎𝑟 4 3 Image result for front view of bicycle and car Image result for Air resistance cd is a parameter to describe how stream- lined a car or a bike is. The smaller, the better. 27 GTSU2015 Green Energy Innovation for Sustainable City Car vs Bicycle Comparing the drag coefficient, the frontal area and the speed, we get obtain the difference of energy per distance between a car and a bicycle. 1 Energy per distance by a car = 4 × 𝜌𝑐𝑑𝑐𝑎𝑟 𝐴𝑐𝑎𝑟 𝑣𝑐𝑎𝑟 2 = 2 𝜌𝑐𝑑𝑐𝑎𝑟 𝐴𝑐𝑎𝑟 𝑣𝑐𝑎𝑟 2 2 1 𝑏𝑖𝑐𝑦𝑐𝑙𝑒 3 Energy per distance by a bicycle = 2 𝜌𝑐𝑑 𝐴𝑏𝑖𝑐𝑦𝑐𝑙𝑒 𝑣 2 𝑏𝑖𝑐𝑦𝑐𝑙𝑒 = 𝜌𝑐𝑑𝑐𝑎𝑟 𝐴𝑐𝑎𝑟 𝑣𝑐𝑎𝑟 2 200 Image result for power consumption of bicycle Assume the speed of the bike is 21km/h (13 miles per hour), so: 𝑣𝑏𝑖𝑘𝑒 1 Image result for Air resistance = 𝑣𝑐𝑎𝑟 5 Also, we have 𝑐𝑑𝑏𝑖𝑘𝑒 1 𝐴𝑏𝑖𝑘𝑒 1 = and = 𝑐𝑑𝑐𝑎𝑟 1Τ 3 𝐴𝑐𝑎𝑟 4 So a cyclist at 21 km/h consumes about 1% of the energy per kilometre of a lone car-driver on the motorway – about 2.4 kWh per 100 km. 28 GTSU2015 Green Energy Innovation for Sustainable City Rolling Resistance Rolling resistance in vehicles pertains to the force that acts against the movement of the tires as they roll over a surface, resulting in various forms of energy consumption: Energy consumed in the tires and bearings of the car. Energy expended on the noise generated by the wheels on asphalt. Energy used in wearing rubber off the tires. Energy dedicated to the vibrations transmitted to the ground by vehicles. Image result for Rolling resistance 29 GTSU2015 Green Energy Innovation for Sustainable City Rolling Resistance The force of rolling resistance (Frr) is associated with: The weight of the vehicle (W). The coefficient of rolling resistance (Crr), which varies with different wheel materials. However, Frr remains constant regardless of the car's speed. Gravitational constant (~10m/s2) 𝐹𝑟𝑟 = 𝐶𝑟𝑟 𝑊 = 𝐶𝑟𝑟 𝑚𝑔 Mass of an object (Weight in earth) For a car with a mass 1 ton (~1000kg), the coefficient of rolling resistance is about 0.01. The rolling resistance (Frr) can be calculated as: 𝐹𝑅𝑅 = 𝐶𝑟𝑟 𝑊𝑐𝑎𝑟 = 𝐶𝑟𝑟 𝑚𝑔 = 0.01 1000𝑘𝑔 10𝑚/𝑠 2 = 100 Netwon(𝑁) In simple terms, a force of 100 Newtons is needed to lift an object weighing around 10 kg. 30 GTSU2015 Green Energy Innovation for Sustainable City Energy Consumption (Air vs Rolling) Fuel consumption (energy per distance) (*The calculation is based on the assumption of the car and bike consuming the energy with an efficiency of 0.25) Car Bike - The rolling resistance is constant which is independent of speed v. - At high speed, the fraction of energy required on rolling resistance to the total energy consumption is becoming insignificant. 31 GTSU2015 Green Energy Innovation for Sustainable City Estimation of Car Energy Usage in UK 32 GTSU2015 Green Energy Innovation for Sustainable City Energy Consumption for Highway-driving Let’s check this theory of cars by plugging in plausible numbers for motorway driving. Let v = 70 miles per hours = 110 km/h = 31 m/s and A = cdAcar = 1m2. The power consumed by the car is estimated to be roughly: Total power consumption of the car 1 𝑚𝑐 𝑣 3 1 =4 2 + 𝜌𝐴𝑣 3 𝑑 2 1 =4 0 + (1.3kg/m2)(1m2)(31m/s)3 2 = ~80 kW Air-swirling dominated (d > 750m) Assuming the car travels a distance of 50 km (30 miles) per day, which requires the time of ~0.5h. Thus, a typical car consumes the energy of: Total energy consumption of the car Basic formula: = 80kW x (~0.5h) = ~40kWh/day Power = Energy / Time (Rate of Energy) 33 GTSU2015 Green Energy Innovation for Sustainable City Double check: car energy consumption We can also calculate from the consumption of the fuels for evaluating the energy consumption by car for driving per day. For example: Distance travelled per day: about 50 km (~30 miles) Distance per unit of fuel : about 33 miles per gallon (~12km/litre) Energy per unit of fuel (say gasoline): ~10kWh/litre How much power a typical car consumes? Distance travelled per day Energy used per day = × Energy per unit of fuel Distance per unit of fuel Image result for car fuel 50 km/day = × 10 kWh /litre 12 km / litre = ~40 kWh / day A typical UK driver uses 40 kWh per day 34 GTSU2015 Green Energy Innovation for Sustainable City Car - Energy per day Distance travelled per day Energy per day = × Energy per unit of fuel Distance per unit of fuel 50 km/day = × 10 kWh /litre 12 km / litre = ~40 kWh / day We’ve made our first estimate of energy consumption. The red box’s height represents 40 kWh per day for a person. 35 GTSU2015 Green Energy Innovation for Sustainable City Estimation of the Transportation Energy Usage in HK 36 GTSU2015 Green Energy Innovation for Sustainable City Energy Consumption for Metro in Hong Kong How much electricity energy for heavy rail consume per day? How much electricity energy for heavy rail consume per day? Daily energy usage by heavy rail = 1559734 MWh/ 365days Next step we need to find out = 4273 MWh/day how many passenger per day 37 GTSU2015 Green Energy Innovation for Sustainable City Energy Consumption for Metro in Hong Kong MTR Data Average energy usage/day-person Assume each passenger goes = 4273 MWh/day ÷ 2,400,000 persons for a round trip per day = 1.8 kWh/day-person 38 GTSU2015 Green Energy Innovation for Sustainable City Lecture Outline 1) Energy Consumption by Vehicles Energy usage in a car Energy consumption in different driving scenario Car vs bicycle Estimation of car energy usage in UK Estimation of transportation energy usage in HK 2) Energy Production by Wind The formation of wind and wind circulation Characteristics of wind Wind Power and wind turbine efficiency Estimation of wind energy production in UK 3) Emerging Wind Turbine Technologies 39 GTSU2015 Green Energy Innovation for Sustainable City Wind Energy Wind is air in motion Wind energy is the energy obtained from the force of the wind Wind Energy (E) and Wind power (P) depend on the wind speed v (e.g. 𝐸 ∝ 𝑣2 and 𝑃 ∝ 𝑣3) Wind energy can be harvested to generate mechanical power or electricity 40 GTSU2015 Green Energy Innovation for Sustainable City Where Does the Wind Come From? Formation of wind in the earth Solar radiation heats unevenly on the earth because of different formations of the earth’s surface, including land, water and mountain etc. Winds are caused by temperature and pressure differences across the Earth’s surface, examples are sea breezes and land breezes. The kinetic energy in the wind comes from the sun (Air density: High) (Air density: Low) Air movement: High atmospheric pressure → Low atmospheric pressure 41 GTSU2015 Green Energy Innovation for Sustainable City Global Wind Circulation Because of the tilt of the Earth, its curvature, area of exposure, our atmosphere, clouds and polar ice and snow etc., different parts of the world heat up differently. This sets up a big temperature difference between the poles and equator. The global circulation provides a natural air conditioning system to If the Earth did not rotate, there would be stop the equator becoming hotter one convection cell in the hemisphere. and hotter, and poles becoming colder and colder. Video: https://www.youtube.com/watch?v=7fd03fBRsuU 42 GTSU2015 Green Energy Innovation for Sustainable City Global Wind Circulation In each hemisphere, there are 60o three convection cells (global wind belts), called Hadley cell, 30o Ferrel cell and Polar cell, in which air circulates through the 0o LP entire depth of the troposphere. HP The troposphere is the name LP HP given to the vertical extent of the atmosphere from the surface, right up to between 10 In reality, the planet is rotating. The situation is more complicated (Coriolis and 15 km high. Effect must be taken into account.). Video: https://www.youtube.com/watch?v=xqM83_og1Fc 43 GTSU2015 Green Energy Innovation for Sustainable City Global Wind Circulation Hadley Cell: The largest cells extend from the 60o equator to between 30 and 40 30o degrees north and south Warm air around the equator is 0 o LP lifted, which creates a low pressure area making the trade HP wind blow towards the equator LP from higher latitude. HP The high-altitude air mass moves either north or south until In reality, the planet is rotating. The air deflect to the left on the ground at the its temperature is low enough North Hadley Cell. for them to “sink” and start to Video: https://www.youtube.com/watch?v=xqM83_og1Fc converge towards the equator. 44 GTSU2015 Green Energy Innovation for Sustainable City Global Wind Circulation Polar Cell: The smallest and weakest cells 60o are the Polar cells, which extend 30o from between 60 and 70 degrees north and south, to the poles. 0o LP Air in these cells sinks over the highest latitudes (high pressure HP region) and flows out towards the LP lower latitudes at the surface (low HP pressure region). The air warms at lower latitude In reality, the planet is rotating. The air deflect to the left on the ground at the and rises up to form the air North Polar Cell. circulation in the cells. Video: https://www.youtube.com/watch?v=xqM83_og1Fc 45 GTSU2015 Green Energy Innovation for Sustainable City Global Wind Circulation Ferrel Cell: The middle cells converges the 60o latitude in between 30 and 60 30o degrees in the north and south. The air on the surface moves 0o LP from high pressure boundary in Hadley Cell to the low pressure HP boundary in Polar Cell. LP HP This results the air current moving in the opposite direction to the two other cells. In reality, the planet is rotating. The air deflect to the right on the ground at the North Ferrel Cell. Video: https://www.youtube.com/watch?v=xqM83_og1Fc 46 GTSU2015 Green Energy Innovation for Sustainable City Localized Wind Circulation Sea breeze Land breeze LP HP HP LP A sea breeze or onshore breeze is the local wind that blows from a large body of water toward or onto a landmass. It develops due to air pressure differences created by the differing heat capacities of water and dry land. Because land heats up much faster than water under solar radiation. As such, sea breezes are more localized than prevailing winds. 47 GTSU2015 Green Energy Innovation for Sustainable City Localized Wind Circulation Sea breeze Land breeze LP HP HP LP A land breeze, a local wind system characterized by a flow from land to water late at the night. Because land cools down much faster than water in the night time. It develops air pressure differences between water and dry land. As such, l