ECE 499 Wind & Solar Power Systems

Part 1: Overview of renewable energy sources

Instructor: Dr. Ha LeDepartment of Electrical and Computer Engineering

California State Polytechnic University, PomonaFall 2015

2What will be presented?1. Power systems in energy context2. Overview of renewable energy generation

systemsa) Hydro power systemsb) Biomass power systemsc) Fuel cell power systemsd) Geothermal power systemse) Tidal power systemsf) Solar power systems: PV and CSPg) Wind power systems

Reading: Chapters 1 textbooks and online relevant content

3Power systems in energy context (1)What is a power system?

An electrical power system is a network of interconnected components designed to convert non-electrical energy continuously into the electrical form, transport the electrical energy over potentially great distances, and convert the electrical energy into an usable non-electrical forms.

One of the largest and most complex electric circuits we have in reality.

What is a power generation system?

An electrical generator which produces power (electrical energy). Name: Type of energy source + Power system e.g. Hydro power system = hydro power generator

4Power systems in energy context (2) Conventional power system (PS) analysis often neglects

how electric power is produced.

It treats electricity as "unique electric power", irrespective of the type of its generating plants.

Necessary to consider PS in an energy context

The availability of the energy sources decides the availability of electric power and subsequently the operation of the power system.

Power generation systems can be divided into three categories based on the energy sources used: conventional, renewable, hybrid.

5Overview of renewable power generation systems

1) Hydro power systems2) Biomass power systems3) Fuel cell power systems4) Geothermal power systems5) Tidal power systems6) Solar power systems: Solar Photovoltaic (PV)

and Concentrating Solar Power (CSP) system7) Wind power systems

6Hydro power systems

The turbine in turn rotates a three-phase AC generator which is connected directly to its shaft to produce AC electric power. To produce AC constant-frequency power, the rotation of the generator must be kept constant. The efficiency of hydraulic turbines is much higher than that of most rotating machines, usually more than 85%.

A damp is built to create a reservoir to store water.

The water is then channeled through a control gate, passes through the blades of a hydraulic turbine and causes the turbine to rotate.

7A hydro power plant damp

8A hydro generator

A hydro generator with the field (rotor) removed, leaving the stationary part, the stator

9Hydro power in United States (1)

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Hydro power in United States (2) Hydropower accounts for around 6% of US electric power supply.

Over the past century, thousands of important rivers and streams have been dammed to produce hydroelectricity. Dam-building peaked in the 1960s.

In recent decades, the growth of hydroelectric power has slowed greatly.

Hydroelectric dams adversely impact aquatic ecosystems by harming plants, fish, and other wildlife in and near rivers. Environmental laws were enacted,limiting building of hydro power plants.

Most of good sources have been exploited.

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Biomass power systems (1)

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Biomass power systems (2) Fuels: Wood, energy crops, organic wastes etc.; more efficient

to use biofuels.

Challenge: To produce combustible high-energy biofuels in the form of liquid or gas which can be easily stored and transported.

Biofuels production:

Ethanol (C2H5OH) and biodiesel (two liquid fuels) and methane (CH4) (a gaseous fuel) are currently the most promising biofuels.

Ethanol is derived from grains, sugar, herbaceous crops, grasses and wood by fermentation and distillation.

Biodiesel is an ester that can be made from a number of vegetable oils and animal fats.

Methane is obtained by Methanogenesis, the formation of methane by microbes.

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Status of Biomass power 65% of biomass energy used in the U.S. comes from

wood, 23% from biofuels, 12% from waste energy.

Over 80 biomass power plants are operational in 20 states across the U.S.

At present, over 2,200 biomass power plants are operational throughout the world. The total capacity is around 32,000 MW.

Problem: Name top producers of Ethanol (fill in the blank country or region) ???(1) .. (2) .. (3) .. (4) ..

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Biomass and the Carbon Cycle (2)

Biomass energy can help clean up the air, water, and soil and protect wildlife, BUT it can also degrade our lands, forests, and water, threaten biodiversity, and harm public health.

This closed cycle, if organized carefully, adds no carbon dioxide to the atmosphere (Department of Energy).

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Fuel cell power systems (1)

A fuel cell converts chemical energy into electrical energy in a way that is similar to that of a battery. Difference: A fuel cell is continually supplied with chemical reactants from an external source and its electrodes are not depleted as it supplies electricity.

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Fuel cell power systems (2)

The ions also react with excess hydrogen at the anode to produce water. The process creates an electrical potentialacross the fuel cell.

In an oxygen-hydrogen fuel cell, oxygen or air is delivered to the cathode and hydrogen is delivered to the anode of the cell.

Potassium hydroxide (KOH.H2O) is used as electrolyte. In the porous cathode, hydroxyl ions (OH-) are created as a result of the reaction of water and hydrogen.

These ions diffuse towards the anode and the reaction releases electrons.

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Technologies, fuels, and applications (1)

The first oxygen-hydrogen fuel cells are used commercially as auxiliary power sources for the U.S. space vehicles. Being considered as power sources for electric cars, trains, submarines, and military vehicles etc.

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Technologies, fuels, and applications (2)

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Cost of transportation fuel cell system

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Fuel cell status and forecast Sales of fuel cells and hydrogen systems: over $1 billion in 2012; over $2 billion in 2013 (forecast). Production costs of low temperature fuel cells for transportation purposes are falling.

However, market penetration for fuel cell vehicles and portable fuel cells is predicted to remain low in the near future.

Environment: The chemical reactions of the fuels generate a large amount of waste water that needs to be safely disposed.

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Geothermal power systems (1) The steam used for geothermal systems is produced using magma as a heat source.

Magma is a molten mass of liquid and gaseous matter which exists under about 20 miles below the crust of the earth

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Geothermal power systems (2)

Before entering the steam turbine, the steam is passed through expansion loops and filters to prevent small pieces of rocks from going into the turbine.

Several wells are drilled deep into the surface of the earth.

Cold water is sent through one well to the extremely hot material under the surface of the earth and is turned into steam there.

Other wells are used to bring the steam back to the surface.

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Geothermal power systems (3)

The steam turbine rotates the electrical generator to produce electric power.

The efficiency of geothermal systems is approximately 20%.

Although their efficiency is lower compared to that of conventional thermal systems, the systems are still viable since they consume no fuel to generate electric power.

The systems also environmentally-friendly.

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Status of Geothermal power World: Installed geothermal generation capacity is 11,224 MW in 24 countries.

US: 3,386 MW (Feb 2013). Estimate by National Renewable Energy Laboratory (NREL, 2006): By 2025 more than 100,000 MW of geothermal electricity could be in production; Direct use and heat pumps could be 70,000 MW.

US undiscovered geothermal systems: 7,917 MWe to 73,286 Mwe.

The implementation of geothermal systems is limited to the areas where the resource is available and mainly depends on deep-drilling techniques.

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US Geothermal power resources (1)

The map shows the temperature beneath the U.S. at a depth of 6 km. The temperature is above boiling at that depth nearly everywhere in the U.S.

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US Geothermal power resources (2)

Most traditional geothermal systems being used for power production in the U.S. are located in the western states, where the natural geothermal reservoirs being formed at shallower depths.

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US Geothermal projects & resource areas

Today, U.S. geothermal resources are being used in more than 30 states.The map shows areas where geothermal energy is being used for power, greenhouses, commercial building heating etc.

Map from the Geo-Heat Center of the Oregon Institute of Technology

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Tidal power systems (1)

Tidal energy is a renewable energy powered by the natural rise and fall of ocean tides and currents.

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Tidal power systems (2)

Some of tidal power technologies include turbines and paddles.

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Status of Tidal power There are very few commercial-sized tidal power

plants operating in the world.

First plant: Rance Tidal Power Station in France (240 MW). Largest plant: Sihwa Lake Tidal Power Station in South Korea (254 MW).

The United States has no tidal plants and only a few sites where tidal energy could be produced at a reasonable price.

China, France, England, Canada, and Russia have much more potential to use this type of energy.

More research and experiment are currently conducted on tidal power systems.

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Solar power systems

Solar energy: Comes from light energy particles called photons. They have no physical mass, but carry large amounts of energy and momentum.

Solar energy: can be solar power or solar heating

Concentrating solar power (CSP) plants: Use mirrors or lenses to concentrate sunlight, creating temperatures high enough to drive traditional steam turbines or engines that in turn create electricity.

Photovoltaic systems (PV): Commonly known as solar panels which produce electricity directly from sunlight.

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Concentrating solar power (1)

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CSP technologies (1)

Parabolic trough systems use curved mirrors to focus the suns energy onto a receiver tube that runs down the center of a trough.

In the receiver tube, a high-temperature heat transfer fluid (e.g., synthetic oil) absorbs the suns energy, reaching around 700F, to heat water and produce steam.

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CSP technologies (2)

These modular reflectors focus the sun's energy onto elevated receivers, through which water flows.

The concentrated sunlight boils the water, generating high-pressure steam to run power generators.

Compact Linear Fresnel Reflector(CLFR)CLFR developers rely on the principles of curved-mirror trough systems, but use long parallel rows of lower-cost flat mirrors.

Advantage: Lower up-front capital costs.

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CSP technologies (3)

Computer-controlled flat mirrors (called heliostats) track the sun and focus solar energy on a receiver at the top of a high tower.

The focused energy is used to heat a transfer fluid (800F to 1,000F) to produce steam and run a central power generator.

Power TowerTo obtain higher operating temperatures for greater efficiencies, other plant designers opt for a central receiver system.

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CSP technologies (4)

A dish-engine system uses a working fluid such as hydrogen that is heated up to 1,200F in the receiver to dri ve an engine.

Each dish rotates along two axes to track the sun.

Dish-EngineMirrors are distributed over a parabolic dish surface to concentrate sunlight on a receiver fixed at the focal point.

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Status of CSP in US California: 9 plants, totaling over 350 MW, have been in

daily operation for over 20 years. Some new plants are:

Crescent Dunes: 110MW, power tower technology, Nevada; Power buyer: Nevada Energy; Online Dec 2014.

Ivanpah Solar: 392 MW, power tower technology, California; Power buyers: PG&E, SCE; Online Feb 2014.

Mojave Solar One: 250 MW, trough technology, California; Power buyer: PG&E; Online late 2014.

Production potential is largest in the U.S. Southwest.

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Photovoltaic systems (1)

Photovoltaic systems (PV), commonly called solar panels, produce electricity from sunlight.

Two layers of a semi-conducting material are combined to form a solar cell. One layer has to have a depleted number of electrons. When exposed to sunlight, the layers of material absorb the photons.

This excites the electrons, causing some of them to move from one layer to the other, generating an electrical charge.

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Photovoltaic systems (2)

When a photon hits a solar cell, it can be absorbed by the cell, reflected off the cell, or pass straight through the cell. Only when a photon is absorbed by the solar cell, an electrical current is generated.

Individual solar cells typically only generate tiny amounts of electrical energy. These cells are connected together to make a solar module (solar panel, shown in right photo).

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Utility-scale PV power plant

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Residential grid-connected PV systems

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Stand-alone home PV

PV as stand-alone generator

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World PV capacity

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Top five countries (Early 2013) United States 5026 MW China 4,345 MW Germany 3,423 MW Spain 1,688 MW India 1,587 MW

Average growth for 2009-2012: 56.5%

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US PV capacity

US total PV capacity: 13,395 MW (Q1, 2014) 482,000 individual PV systems are connected to the grid

(Q1, 2014).

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Role of PV in power systems Solar is increasingly important power source.

PV work as utility scale generators (grid-connected). Work as distributed generators (those of smaller sizes

compared to utility-scale PV) or stand-alone generators. Examples: home PV, power supply for stand-alone

lighting systems, for communication systems etc.

Can couple with other generator such as a wind turbine to form a hybrid system.

Outlook: Solar power sector will continues to grow. The current cost for solar power is still high (12-30 cents/kWh), but the cost will decrease.

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Wind power systems (1) Modern wind turbines harness wind

kinetic energy and convert it into electricity.

Most wind turbines have three blades and sit atop a steel tubular tower (from 80 feet to over 370 feet tall).

A wind turbine consists of a steel tubular tower, which supports both a "hub" securing WT blades and the "nacelle" which houses the turbine's shaft, gearbox, generator and controls.

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Wind power systems (2)

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Major types of wind power systemThe major types of wind power are:

Utility-scale wind: Wind turbines larger than 100 kW, which are connected together to form a generation station called a wind farm that is then connected to the utility power grid.

Distributed or small wind: Uses turbines of 100 kW or smaller to directly power a home, farm or small business.

Offshore wind: Wind turbines installed in bodies of water around the world (soon be built in the United States Cape Wind)

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Utility wind power systems

Land-based wind farm

Offshore wind farm

Utility wind power systems are big wind farms (tens to hundreds of MW) which are connected to power grid.

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Residential grid-connected WT

Wind turbines of 100 kW or smaller to directly power a home, farm or small business as it primary use.

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Stand-alone wind power systems

Wind-diesel system: To provide power to island or remote areas.

Wind-PHEV (Plug-in hybrid electric vehicle): Wind turbine generates power to charge PHEV.

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Hybrid wind turbine & PV

PV couples with a wind turbine to form a stand-alone power system

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Trend in wind turbine size

As wind power technology improves, wind turbine size keeps increasing

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How loud is a wind turbine?

A-weighted decibels, abbreviated dBA, or dBa, or dB(a), are an expression of the relative loudness of sounds in air as perceived by the human ear.

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World wind power capacity

Average growth (2010-2014):18.4%

Top five countries (2014)

China (114,763 MW) United States (65,879 MW) Germany (40,468 MW) Spain (22,987 MW) India (22,465 MW)

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US wind generation capacity61,091

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Average growth rate (2009-2013): 20%

Top five states (Early 2013) Texas 12,355 MW California 5,830 MW Iowa 5,178 MW Illinois 3,568 MW Oregon 3,153 MW

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US wind power: some facts & figures Penetration level (2013): 10% - 24.5% in ten states; Iowa:

24.5%, Texas: 7.4%, California: 4.9%.

Emission reduction: In 2009 US wind generation fleet produced >74 million kWh, reduced >44 million tons of CO2 equivalent to taking 7.5 million cars off the road.

Benefit for farmers: Land lease payment is around $2,000 to $5,000 per year for each wind turbine, depending on its size.

Wind power targets: Renewable Portfolio Standard (RPS)a) 20% of electricity from wind by 2030 (target by

Department of Energy)b) California RPS: 25% of electricity from renewable

sources by 2016, 33% by 2030.

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Role of wind power in US power sector American wind power topped 4% of the U.S. grid power by

the end of 2013 (the 5th largest electricity source). Delivered 30% of all new generating capacity for the last five

years ($25 billion investment in 2012). The price of wind under long-term power purchase contracts

signed in 2011 and 2012 averaged 4 cents per kWh, making wind competitive with a range of wholesale electricity prices seen in 2012.

By the end of 2012, more than 150,000 distributed (small) wind turbines were installed in the country.

Outlook: Wind power will have significant impact on many facets of the future power system.