Jürgen Scheffran Institute of Geography, KlimaCampus

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Other Renewable Energy Sources

Jürgen ScheffranInstitute of Geography, KlimaCampus

Universität Hamburg

“Energy Landscapes and Climate Policy" Lecture 63-951May 21, 2015

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HYDRO POWER

Gordon Dam, TasmaniaHoover Dam, USA

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Development of large dams

Large dam: higher than 15 m

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World hydropower generation (TWh by region)

Adapted from BP 2010

Source: IPCC 2011 SRREN, Special Report on Renewable Energy Sources and Climate Change Mitigation, http://srren.ipcc-wg3.de/report

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Regional hydropower technical potential in 2009

Source: IPCC 2011 SRREN, based on IJHD 2010

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Regional hydropower technical potential (2009)

Source: IPCC 2011 SRREN, based on IJHD 2010

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Major hydroelectricity producer countries

Source: IPCC 2011 SRREN, based on IJHD 2010

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Hydropower plant investment cost as function of plant capacity (for undeveloped sites)

IPCC 2011 SRREN, adapted from Hall et al. (2003)

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Gross hydropower potentials in EU-MENA

adapted from /Lehner et al. 2005

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Total power potential of water energy resources in the 50 states of the USA

Source: http://www1.eere.energy.gov/water/pdfs/doewater-11263.pdf

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Hydropower problems and conflicts

About 45.000 large dams (>15 meter)

Social, ecological and economic problems

Massive change in landscape

Loss of living conditions of population

Enforced resettling (40-80 mio people)

Damage for the environment (river ecology)

Loss of cultural heritage

Unbalanced distribution of benefits and risks

Profits for firms, banks, suppliers and big customers of energy

Disadvantage for small farmers, fishermen, settlers and indigenous people

Impact of the protest movement

Media attention to protest, withdrawal of the World Bank

„Declaration of Curitiba“, World Commission on Dams (WCD)

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Euphrat-Tigris water projects

Impact on environment and society:

•382 villages affected, ca. 200,000 people resettled

•Atatürk Dam affected 55,300 people: compensation insufficient

•Flooding of Lake Assad: forced displacement of ca 4,000 families

•Reduced water from increased evaporation

•Low water quality in Iraqi Euphrates because polluted irrigation water from Turkey and Syria

•Increased salinity of Euphrates in Iraq, lower suitability as drinking water.

•Effect on geologically fragile Mesopotamian Marshes and freshwater fish habitats in Iraq.

•Flooding of many archaeological sites and other places of cultural significance.

State limitsLimits of hydrographic unitIrrigation cultivationPlanned expansion GAPHydro damsBarragesHydro station

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Three Gorges Hydro Project

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Global wind resource map (5 km x 5 km resolution)

Source: IPCC (2011) SRREN

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Physics of wind power

Wind energy is the kinetic energy of air in motion, flowing through an area A during time t:

ρ : density of air; v : wind speed; Avt : volume of air passing through AAvtρ is mass m passing per unit time.

Power is energy per unit time, so the wind power for rotor area A is:

Wind power is proportional to the third power of the wind speed; Power increases eightfold when the wind speed doubles.

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Annual average wind speed in EU-MENA at 80 m above ground level in m/s

Source: Prepared by DLR with data from ECMWF, ISET for /WBGU 2003/

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US wind resources

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Wind energy, electricity demand and instantaneous penetration levels

Data for (a) West Denmark for a week in January 2005, and (b) Ireland for two days in April 2010.Source: IPCC 2011 SRREN: based on (a) www.energinet.dk; (b) www.eirgrid.com

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World wind energy generation

Source: Vital Signs 2011

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Top-10 countries in cumulative wind power capacity

Source: IPCC 2011 SRREN, based on GWEC 2010

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Approximate annual average wind electricity penetration

Source: IPCC 2011 SRREN, based on Wiser and Bolinger 2010

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Growth in size of commercial wind turbines

Source: IPCC (2011) SRREN

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Development of wind-generation costs based on Danish experience

Morthorst, 2004

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Conflict potential of wind power

Change of landscape

Noise emission

Shadow generation, „Disco effect“

Threatening of birds

Substitution potential

Profitableness

Build back

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OCEAN ENERGY

Tidal power plant La Rence, France (www.industcards.com/hydro-wave-tidal.htm)

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Ocean energy

Ocean or marine energy/power: energy carried by ocean waves, tides, currents, salinity, and ocean temperature differences (not off-shore wind power).

IPCC 2011 (SRREN): „Technologies for harnessing ocean energy are probably the least mature of the six principal forms of renewable energy ... but the energy resources contained in the world’s oceans easily exceed present human energy requirements.“

Ocean energy could be used to supply electricity and for potable water production. Some potential ocean energy resources (ocean currents, osmotic power from salinity gradients), are globally distributed, other forms have complementary distribution.Ocean thermal energy is principally distributed in the Tropics around the Equator (0°– 35°), whilst wave energy principally occurs between latitudes of 40° - 60°. Some forms of ocean energy (ocean thermal energy, ocean currents, salinity gradients and wave energy), may generate base load electricity.

With the exception of tidal rise and fall energy, which can be harnessed by the adaptation of river-based hydroelectric dams to estuarine situations, most ocean power technologies are presently immature. None can be truly characterized as commercially competitive with the other lowest cost forms of renewable energy – wind, geothermal and hydroelectric energy.

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Ocean energy

Theoretical global ocean energy resource

Capacity(GW)

Annual gen.(Exajoule EJ) Form

5,000 180 Marine current power20 7,2 Osmotic power1,000 36 Ocean thermal energy90 2,9 Tidal energy1,000—9,000 29—290 Wave energy

Huge amounts of kinetic energy in ocean water: conversion to electricity

International Energy Agency, Implementing Agreement on Ocean Energy Systems (IEA-OES), Annual Report 2007

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Use of tidal power

Tidal energy differs from other energy sources: energy extracted from potential and kinetic energies of earth-moon-sun system.

Ocean tides produce variations in ocean water level along shores.

Water level fluctuations fill and empty natural basins along shoreline, suggesting that the currents flowing in and out of these basins could be used to drive water turbines connected to generators. The technology employed is very similar to that of low-head hydropower.

To enhance efficiency, dam like structures can be built across the mouths of natural basins, with gates or channels to direct the natural flow through turbine locations in sequence with the tides

Turbines designed to convert water flow into electricity.

Intermittent flow limits effective duty factor, about one third as hydroelectric power plant of same peak capacity.

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Tidal ranges globally

Source: Bent Sörensen, Renewable Energy, 3rd Edition,Elsevier Academic Press, 2004, p. 263.

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Tidal range in North Europe

Source: Bent Sörensen, Renewable Energy, 3rd Edition,Elsevier Academic Press, 2004, p. 260.

Measured in meter

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Potential reductions in investment costs for wave and tidal current energy devices

Source: IPCC 2011 SRREN

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Ocean waves

Designs for converting wave energy to electricity.

Floats anchored to bottom or underwater plate,

heaving and pitching floats

oscillating water columns

flexible bag surge devices.

Highest linear power densities of average incident mechanical wave power occur in: NE Atlantic (Norway, Scotland, and England) and Southern Ocean (Australia) regions.

Rough seas locations/designs suffer from high capital and operation cost.

Projected average capacity factors 32%–38%, for highest capital cost with capacity factor 60%.

Commercial wave electric power not bright.

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Global offshore annual wave power level distribution

IPCC 2011: SRREN, based on Cornett 2008

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Regional theoretical wave power

IPCC 2011 SRREN, basedn on Mørk et al. 2010

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Oscillating water column converter

Source: Brown/Skispy 1986

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Surface ocean currentsshowing warm (red) and cold (blue) systems

IPCC 2011 SRREN, based on UCAR 2000

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Worldwide average ocean temperature differences (°C between 20 and 1,000 m water depth)

IPCC 2011 SRREN based on Nihous 2010

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Ocean Thermal Energy

Accessible ocean thermal differences lie between about 10–20 degree Kelvin at warm fluid temperatures of about 290 degrees Kelvin. Thus ideal thermodynamic efficiencies are only a few percent, and real system efficiencies can be as small as 1%.

Since energy source is "free," primary consideration is capital cost per unit capacity and operation and maintenance cost per unit power production (including net cost of environmental impact).

One approach is to use ammonia as a working fluid in a closed system heat exchange loop. The possibility of adverse impact from ammonia spills can be a significant consideration.

Mass of piping and other equipment per unit power production can be quite large.

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Ocean thermal energy conversion (OTEC)

Source: Wikipedia

Ocean thermal energy conversion (OTEC) uses ocean thermal gradient caused by solar heating of surface water which is strongest in tropics. In a few remote island locations physical and economic conditions make OTEC potentially interesting as energy source.

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OTEC in Hawaii

Source: Wikipedia

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GEOTHERMAL ENERGY

Nesjavellir Geothermal Power Plant in Iceland

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Temperature in the Earth

From: Alyssa Kagel, Diana Bates, Karl Gawell, A Guide to Geothermal Energy and the Environment, Geothermal Energy Association, Washington, D.C., 2005, www.geo-energy.org.

4000 deg.

5000 deg.

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Geothermal energy flow

Overall flow of energy into, around, and throughout the Earth’s layers

Most geothermal energy reaching the earth's surface comes from radioactive decay energy coming up from the mantle

Temperature differences between one spot on Earth and another spot can be used to turn a heat engine, or to transfer thermal energy.

Two points of temperature difference must be in close proximity, and the difference in temperature must be large in magnitude.

Average geothermal flows useless for economic electrical power generation.

Temperature gradient in top layers of oceans is larger and in reverse direction of geothermal gradient in lithosphere.

While total flow of geothermal energy to earth's surface is only 1/2,400 of solar flux on the surface on average, geothermal flow is still quite large at ca.1000 exajoules per year.

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Energy flow across Earth's

surfaceThe flow diagram depicts energy flows across the earth's surface. The units are joules per calender year.Adapted from Energy Resources: Geology, Supply and Demand, Edited by Brown, G. C. and Skispy, E. Open University Press, Philadelphia © 1986

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Geothermal energy

Heat is extracted from geothermal reservoirs using wells or other means.

Hydrothermal reservoirs are naturally sufficiently hot & permeable.

Enhanced geothermal systems (EGS) are sufficiently hot but are improved with hydraulic stimulation.

At surface, fluids of various temperatures can be used to generate electricity or can be used more directly for applications that require thermal energy, including district heating or the use of lower-temperature heat from shallow wells for geothermal heat pumpsused in heating or cooling applications.

Hydrothermal power plants and thermal applications of geothermal energy are mature technologies, whereas EGS projects are in the demonstration and pilot phase while also undergoing R&D.

When used to generate electricity, geothermal power plants typically offer constant output. (IPCC 2011 SRREN)

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Geothermal reservoirs

Source: Geothermal Today, 1999 Geothermal Energy Program Highlights, U.S. DoE, http://www.nrel.gov/docs/fy00osti/27820.pdf

Geothermal resources usable for energy production are vapor-dominated sources that can be used directly to drive turbine.

If vapor contains noxious gases exhaust may be reinjected into ground.

Pressurized hot water with dissolved minerals (brine) for electricity generation by flashing brine to steam and using steam to drive turbine. Hot water may also be used for heating swimming pool in resort area.

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Geothermal energy

Geothermal brine system: includes steam generator and direct use of hot waste water.

Geothermal electricity generating plant: largest structures may be cooling towers for condensing steam from turbine exhaust.

Economics of geothermal energy use for electricity generation requires extraction of geothermal energy faster than replaced by heat transfer from below; more like extraction of mineral fuel.

Globally, geothermal potential concentrates in tectonically active regions; minimal in Europe outside of Iceland, Italy, and Greece.

Most of world capacity is likely to be economic only at substantially higher than currently prevailing energy prices.

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Geothermal energy system

From Renewable Resources in the U.S. Electricity Supply, Energy Information Administration, © February, 1993.

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Growth of the globally installed capacity of geothermal power production

Source: Global Energy Assessment, based on Bertani, 2010

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Geothermal heat flow and installed electric capacity (by country in 2009)

Worldwide average heat flow in mW/m2 and tectonic plates boundaries

IPCC 2011 SRREN, adapted from Hamza et al. 2008

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Mapping of the 10.7 GW installed geothermal electric capacity in 2009

Source: Global Energy Assessment, based on Bertani, 2010

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Regional installed capacity for geothermal power and direct uses (current and 2015)

IPCC 2011 SRREN

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Global solar irradiance at Earth’s surface (W/m2)

(a) December, January, February (b) June, July, August

Source: ISCCP Data Products 2006

averaged over the period 1983 to 2006

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Annual global solar irradiation on surfaces tilted South with latitude angle in kWh/m²/year

Source: Prepared by DLR with data from ECMWF 2002 for WBGU 2003

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Solar resources in the USA

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Annual total technical potential of solar energy for various regions of the world

IPCC 2011 SRREN Rogner et al., 2000

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Solar power technologies

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Direct energy from the Sun

• Abundant energy resource, as electromagnetic radiation

• Sun emits energy rate 3.86 x 1026 watts, at earth's orbit of 1.496 x 108 km gives average insolation at top of earth's atmosphere of 1.373 kW/m2

• Fuels most types of our renewable energy resources

• Place something in the path of sunlight to increase its temperature

• Passive heating effect can be used successfully and economically

• Amount of energy available per unit area is small compared to advanced fossil or nuclear energy source

• Solar energy will be likely available for another five billion years.

• Solar power can be decentral (solar home systems) or central (concentrated solar power), Impact on landscape can be small or large, Environmental impact at production

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Direct solar energy technologies

Energy of solar irradiance

to produce electricity using photovoltaics (PV) and concentrating solar power (CSP),

to produce thermal energy (heating or cooling, either through passive or active means),

to meet direct lighting needs

and, potentially, to produce fuels that might be used for transport and other purposes.

The technology maturity of solar applications ranges from R&D (e.g., fuels produced from solar energy), to relatively mature (e.g., CSP), to mature (e.g. passive and active solar heating, and wafer-based silicon PV).

Many but not all of the technologies are modular in nature, allowing their use in both centralized and decentralized energy systems.

Solar energy is variable and, to some degree, unpredictable, though the temporal profile of solar energy output in some circumstances correlates relatively well with energy demands.

Thermal energy storage offers the option to improve output control for some technologies such as CSP and direct solar heating.(IPCC 2011, SRREN)

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Installed and planned concentrated solar thermal electricity plants by country

IPCC 2011 SRREN, adapted from Bloem et al. 2010

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Worldwide photovoltaic (PV) production

IPCC 2011 SRREN, adapted from Jäger-Waldau 2010b

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PV production and installation

Vital Signs 2011

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Solar price experience or learning curve for silicon PV modules

Data source: Maycock (1976-2003); Bloomberg (2010).

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Trends in conversion efficiencies for various laboratory solar cell technologies

Source: Global Energy Assessment 2012, based on Kazmerski 2011

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State of the art and possible development of commercial PV module efficiencies

Source: IEA 2010

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Schematic cross-section of a solar cell

Source: Global Environmental Assessment 2012

1. Photons in sunlight hit the solar panel and are absorbed by semi-conducting materials, such as silicon.2. Electrons (negatively charged) are excited from molecular/atomic orbital and either return to its orbital or travel through the cell until it reaches an electrode. 3. An array of solar cells converts solar energy into a usable amount of direct current (DC) electricity.

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Microenergy and rural development:Solar Home Systems in Bangladesh

Cumulative sales of solar home systems (SHS) by Grameen Energy in Bangladesh(Source: http://www.gshakti.org/#)

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Basic concentrated solar power configurations

parabolic trough linear Fresnel reflector

central receiver/power tower dish systems

Richter et al. 2009

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Concentrated solar collectors

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Solar Thermal Towers

PS10

PS20

Planta Solar 20 (PS20) solar thermal energy plant in Sanlucar la Mayor in Andalusia, Spain (Wikipedia)

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Solar central receiver or power tower

Large array of two-axes tracking mirrors (heliostats) reflect direct solar radiation onto a fixed receiver located on top of a tower.

When hundreds of heliostats concentrate radiation at one point, the solar furnace, the tremendous amount of heat generated can produce high-temperature steam or other gas which expands through a turbine to produce electricity.

Within the receiver, a fluid (water, air, liquid metal and molten salt) transfers the absorbed solar heat to the power block, where it is used to heat a steam generator.

Advanced high-temperature power tower concepts: heat pressurized air to over 1000oC and feed to gas turbines or modern combined cycles.

The plant cycle, complete with turbine, condenser, and pump, is similar to plants which use fossil fuels or nuclear fission for their original energy source.

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Renewable energy network between Europe and Africa?

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Constraints to widespread market applications

Sun shines only part of the day

Cells can degrade or break

Cells are costly to make compared to the power they produce

Weather in upper latitude climates more detrimental to cells

Sunlight's energy density is low compared to the burning of a fossil fuel

Physical complexity can be drawback for applications.