Wind Solar Hydroelectric Geothermal Ocean
It has been calculated that massive amounts of renewable energy are available on Earth. The
theoretical potential is > 4 million TW .
The technical potential totals around 240 TW, which is > 10 times the energy we consume in one year
today worldwide. Read more. This number aggrees well with calculations by Greenpeace report
Energy [R]evolution (379 TW)
In addition to tidal and ocean wave energy there is ocean thermal energy, which is at least 2 orders of
magnitude larger than tidal and wave energy.
Technical potential of the different types of renewable energies depends on the
geographical location in the World. See next slide
It has been calculated (Greenpeace Energy Revolution Report) that in 2050 Africa, the
Middle-East and Australia will have the largest relative potential compared to their total
primary energy consumption in 2007 (up to a factor of 50).
China and Europe have a 10 x lower potential, but still largely sufficient to exclusively
rely on renewable energy.
Source: Greenpeace Energy Revolution Report
Absolute energy values are expressed in Etajoules/year
(1 Etajoule = 31.71 GWyear)
RE = renewable energy
Worldwide ~2 TW renewable energy was
available in 2011, which is >10% of total
energy consumption and 20% of electricity
generation. If traditional biomass energy is
included sharing of renewables is 16%.
CSP = concentrating solar power; PV = photovoltaic
Belgium has a 5.7 GW capacity for 2011,
which is 6.3% of its total (90 GW)[1, 2].
Belgium ranks 4th in solar photovoltaic (PV)
panels per capita and is within the world top
15 countries to make biofuel. Energy safety
of Belgium is, however, vulnerable as it
imports 80 % of its energy as fossil energy,
despite it has 2 nuclear power plants (7
Renewable energy capacity
in 2011 - World
Renewable energy capacity
in 2011 - Belgium
Energy from solar radiation is either passive or
active depending on the way capture,
conversion and distribution of sunlight
Active solar techniques use photovoltaic panels
and heat collectors to convert sunlight into
Passive solar techniques include selecting
materials with favorable thermal properties,
designing spaces that naturally circulate air,
and optimizing the position of a building to
Picture from NOAA
How much energy is contained in solar radiation?
The solar radiation on Earth at the top of the atmosphere is roughly 1367 W/m² cross section.Thus,
for the whole Earth, the solar power is 1367 x 127,500,000,000,000 = 174,292 TW (Mean Earth
radius = 6371 km; Earth cross section = 127,500,000 km² )
However, the Earth is a rotating globe and hence the solar energy is distributed across the entire
surface area. Taking into account the angle at which the rays strike and that at any one moment half
the planet does not receive any solar radiation, roughly only about one-fourth of the solar radiation
is recoverable at the top of the atmosphere (approximately 340 W/m² on the average). At the Earth’s
surface this is about 50 % less due to reflection and absorption by the atmosphere and clouds, i.e.
approximately 170 W/m² on the average.
Assuming only energy received over land as usable and land area = 1.481 × 1014 m2, radiative energy
= 170 x 148,100,000,000,000 = 25,177 TW. This capacity, that is continuously present, is roughly
equal to the total capacity of fossil energy resources estimated to be present today (see slide 14).
If we assume that the conversion efficiency of solar energy would be only 10% and that energy
capture would be limited to about 10% of land surface, the solar energy resource would be 250 TW.
This is about 14 x the total world energy consumption today (18 TW).
Thus, theoretically, solar energy alone could be a sustainable energy resource, as world population is
expected to stabilize around 10 billion and primary energy consumption predicted for 2100 is 50 TW.
How long can we survive on earth using solar energy?
Solar radiation will not decrease but grow by 10% over the next 1.1 billion years and by 40% over
the next 3.5 billion years. This will have devastating consequences for life on Earth. The CO2 cycle
will acclerate, reducing CO2 concentration to levels lethally low for plants (10 ppm for
photosynthesis) in approximately 500-900 million years. This will result in the loss of oxygen in the
atmosphere, so animal life will become extinct within several million more years. After another
billion years all surface water will have disappearedand the average global temperature will reach
Solar hot water collectors
are used to heat water. It can provide 60 to
70% of the domestic hot water use with
temperatures up to 60 oC. As of 2010, the
total installed world capacity of solar hot
water systems was approximately 196 GW
(Wiki). China is the world leader with 118 GW
installed as of 2010 and a long term goal of
210 GW by 2020.[58
A photovoltaic cell (PV), is a device that converts
light into electric current using the
photoelectric effect. Germany is the world's
top PV installer, with a solar PV capacity of
more than 32 GW in 2012. World capacity is
Solar energy types
19 MW solar park in Germany
Concentrating Solar Power (CSP)
CSP systems use lenses or mirrors and tracking systems to
focus a large area of sunlight into a small beam. The
concentrated heat is then used as a heat source for a
conventional power plant to generate electricty. World
capacity in 2011 was 2.2 GW. Spain installed 1.9 GW.
About 17 GW of CSP projects are under development
Other solar systems
Solar distillation to make potable water from saline or
brackish water. Solar water disinfection. Water
stabilization pond to treat waste water without
chemicals or electricity; Solar cooker; Solar pond; Salt
evaporation pond; Solar furnace; Solar chemical and
Solar fuel production from artificial photosynthesis
Aerial view of the ‘Solar Two’ CSP facility in
the Mojave Desert , showing the power
tower (left) surrounded by the sun-tracking
Annual mean insolation at
the top of Earth's
atmosphere (top) and at the
planet's surface in W/m2
Geographical variation in solar power
Earth's geothermal energy originates from radioactive decay of minerals in the Earth's mantle .
It can be used
either as a non-renewable source i.e. the heat in the first 3000 m of the Earth's mantle which contains
enough heat to theoretically supply all of the world's energy for 100,000 years, although only a
small percentage of that is technically extractable
or as a renewable source i.e. the heat used not more than that replenished each year. The latter can
be tapped from deeper Earth layers and would be sustainable for about 2 billion years at the
consumption rate of our present energy use. .
Shallow ground heat energy is mainly of solar energy. Below a depth of 6 m temperature is equal to the
mean local surface temperature.
Geothermal energy is used for home thermoregulation by heat pumps extracting ground heat in the
winter (for heating) and transfering heat back into the ground in the summer (for cooling), for district
heating and for generating electricity in power plants.
A power plant needs the higher temperatures of deep Earth resources.. To tap the heat, holes are
drilled deep in the Earth, water is punped in and, after exchanging the heat (150-270 oC), transports
the heat to a turbine (see Figure in next slide). Depths are usually 4-5 km but drilling as deep as 12 km
is feasible (Read more). To increase heat conductance the procedure of Enhanced Geothermal
Systems is adopted today. Even though geothermal power is renewable, extraction must be monitored
to avoid local depletion. Over the course of decades, individual wells may draw down local
temperatures, but if extraction rates are then decreased the local temperature rises again.
Worldwide, about ~11 GW of geothermal power is deployed in 24 countries (the U.S. being the
world leader) and ~28 GW of direct geothermal heating. ++
Hydroelectricity is electricity generated by hydroturbines
driven by the gravitational force of falling or flowing
water. It is the most widely used renewable energy,
accounting for 16% of global electricity consumption, and
970 GW of electricity production in 2011 (see Ren21)
The Three Gorges Dam in Hubei, China, has the world's largest
capacity (22 GW), with the Itaipu Dam (14 GW) in
Brazil/Paraguay in second place and Guri Dam (10 GW) in
Venezuela as third. Although the Three Gorges Dam
reduces the potential for floods downstream by providing
flood storage space, the dam is criticized as it flooded
archaeological and cultural sites and displaced some
1.3 million people, and is causing significant ecological
changes. The Guri Dam is controversial, because the lake
created by the dam destroyed thousands of km2 of forest
that was renowned for its biodiversity and rare wildlife.
A risk of this power supply is power shortage during
prolonged drought, as water levels become too low to
produce enough electricity.
Wind power is the conversion of wind energy into a
useful form of energy, such as by wind turbines to
make electrical power, windmills for mechanical
power, or wind pumps for water pumping or
drainage. Wind power is proportional to the third
power of the wind speed.
Wind turbine power worldwide in 2012 was 282 GW,
China being number 1 (75 GW) before the U.S. (60
GW). In addition to large turbines, the World Wind
Energy Association (WWEA) reported more than
650,000 small wind turbines globally in 2010.
Wind power depends on the location of the turbines and
has significant variation over short time scales.
Power management techniques can greatly mitigate
these problems, such as installing excess capacity
storage, geographically distributed turbines,
dispatchable backing sources, exporting and
importing power to neighboring areas or reducing
demand when wind production is low. Weather
forecasting permits the electricity network to be
readied for variations in production.
Since wind speed is not constant, a wind
farm's annual energy production is never
maximum of the installed capacity (name
plate). The ratio of actual productivity to the
theoretical maximum is 15–50%[nb
Geographical variation in wind power
Wind speeds (V) at 80 m height in Europe and the U.S. (Source: Archer & Jacobson)
Since solar energy is absent during the night and since wind is not always blowing, it is important that
the captured energy can be stored and later be used if power supply is absent.
• Deployment of solar power to energy grids
• Thermal mass applications
• Seasonal thermal energy storage
• Grid energy storage
• Vehicle-to-grid systems
Left: The 150 MW Andasol solar power station is a commercial parabolic trough
solar thermal power plant, located in Spain. The Andasol plant uses tanks of
molten salt to store solar energy so that it can continue generating electricity even
when the sun isn't shining.
Wind power complements very well with hydroelectricity power. When the wind is blowing strongly, nearby
hydroelectric plants can temporarily hold back their water, and when the wind drops they can rapidly increase
production again giving a very even power supply.
Pumped-storage hydroelectricity or other forms of grid energy storage can store energy developed by high-
wind periods and release it when needed .Belgium is planning to build a Pumped-storage hydroelectricity
in the North Sea.
Solar and wind energy storage
Biomass energy is energy from the sun that has been
stored in plants through photosynthesis.
Traditional biomass includes firewood, charcoal,
manure and crop residues, the natural energy
source that humans used since the discovery of
making fire. It is still widely used in developing
countries for cooking and heating.
Modern biomass includes
either dead forest residues, yard clippings, wood
chips, municipal rotting garbage, agricultural
and human waste
or plants grown on purpose (such as switchgrass,
hemp, corn, sugarcane, bamboo, eucalyptus
and oil palm) that can be converted into
methane, hydrogen or transportation biofuels,
like bioethanol and biodiesel. Ethanol is made
from sugars, biodiesel from oils.
Biomass production from algae is a promising future
source of biofuels. It has the great
advantage that it can use waste water and even sea
water as nutrients and sequester CO2 when joined
to a fossil power plant. Read more
Biomass is used either to generate electricity
(via steam turbines or gasifiers), or to produce
heat via direct combustion. Often both energy
conversions are combined in the same power
plant. Biomass is also used to produce biofuels
for transportation (2.7% of the world's transport
fuel in 2010), either in pure form or (usually) as
an additive (see slide 81b). Bioethanol (from corn
or sugar cane) is primarily used in the US and
Brazil, biodiesel (from rapeseed) in Europe.
Collection and chipping of crop for bioenergy use and
Traditional biomass capacity worldwide
was ~1 TW in 2010. Its share in
residential energy use is high in
Modern biomass capacity was ~0.35 TW
• Little or no impact on health and environmental except biomass
• Little or no greenhouse gas emissions - except for biomass - once the energy device is
constructed and therefore a convincing mitigation method for climate change.
• Minimal land and freshwater requirements. Geothermal and wind power use 3.5 km2 and
12 km2 per GW electric energy produced, respectively vs 32 km2 for coal. Geothermal
plants use 20 l of water per MWh vs over 1,000 l per MWh for nuclear, coal, or oil.
• Supply safety provided there is back-up installation (e.g. in case of no wind), local energy
security and reduced import dependency
• Short construction periods compared to conventional energy generation
• Relatively low operational complexity compared to other energy generation. Onshore wind
and solar PV projects have well established operational track records.
• Predictable cash flows as it is not subject to fuel price volatility because the primary energy
resource is generally freely available.
• Job creation: According to the Renewables 2012 global status report, renewable energy
investments created 5 million jobs worldwide, of which more than 1 million in the European
Union, 1.6 million in China and almost a million in Brazil.
• Biofuels may attenuate the increase of oil price and delay ‘peak oil’
• Renewable energy is sustainable, but the
machinery to generate this energy needs
numerous critical materials. The table on the
right overviews these materials.
• The availablity of these materials is limited
which may become a problem. These materials
are unevenly distributed over the World, which
can become an issue during economical
competition, increasing demands of these
materials or conflicts. Prices may increase when
resources are declining.
• Decision makings as to a transition to a
renewable energy-driven economy has to
seriously take these issues into consideration.
For many of these elements, we have
historically devoted almost no effort in
discovery and recovery after use. Thus
renewable energy deployment will require
efforts for reuse, recovery and recycling of
• Wind and solar power
Wind and solar devices may have land, visual and noice impacts.
• Geothermal power plants
Like nuclear power plants, geothermal plants are heat pollutants as they add heat energy
to the biosphere that would not otherwise be released. This is not the case for wind, solar,
tidal and hydroelectric power generation.
Fluids drawn from the deep Earth carry a mixture of greenhouse gases (CO2, hydrogen
sulfide, methane and ammonia), but it is 8 times less than a coal power plant . If pumps
are driven by conventional power plant electricity, considerable greenhouse gas is emitted.
Plant construction can adversely affect land stability.
Enhanced geothermal systems can trigger earthquakes as part of hydraulic fracturing. The
project in Basel, Switzerland was suspended because more than 10,000 seismic events
measuring up to 3.4 on the Richter Scale occurred over the first 6 days of water injection.
• Hydropower stations
Since they often generate electricity for large areas, power failures can cause serious
discomfort. Moreover, there are quite numerous examples of hydropower station failures and of
dam failures, that caused large damage to humans and land. Very large hydropower installations
have also been criticized for having forced people to move and damage ecosystems.
o Large-scale production of biomass entails heavy demand for land, water, and labor. Biomass
cropland is competitive with cropland for food, causes deforestation, soil erosion, loss of
biodiversity and has a negative impact on water resources as a consequence of artificial
irrigation necessary for its cultivation. Deforestation causes a decrease of ~150 tonnes carbon
sequestration/ha (IPCC, 2006)
o Biofuels display lower greenhouse gas (GHG) emissions (CO2, nitrogen oxides) than fossil fuels
(10-90% less) but can replace fossil liquid fuels only for 10-15% in the transport sector due to
lack of adequate land and sustainability constraints.
o If GHG emissions due to the industrial processes needed for production and transport of the
crops, and refining of the fuel are included in evaluating its greenhouse gas emissions (life
cycle assesment, LCA), the GHG balance can be negative. There are LCA studies showing that
CO2 emission is lower than CO2 squestration by photosynthesis during crop growth, other
studies show the opposite (see table in next slide).
o LCA has shown that it would take between 75 and 93 years for the CO2 emissions saved
through replacing fossil fuel with biofuel to compensate for the loss in CO2 sequestration
through deforestation. If the original habitat was peatland, it would take more than 600 years.
o A metaanalysis LCA study showed that, with the exception of a few studies, oil-palm biodiesel
is a net emitter of GHG. Today, oil-palm plantations cover over 130,000 km2, primarily in
Southeast Asia, where they have directly or indirectly replaced tropical rainforest.
o The table below shows greenhouse gas (GHG) fluxes from biofuels in megagrams
(kilotonnes) per hectare per year, showing the inconsistency between studies:
o Negative values indicate a net uptake of GHG by the crops (i.e. removal from the
atmosphere) and positive values indicating a net emission of GHG (i.e. added to
o In a number of countries (e.g. European Union) planting of biomass crops is mandated by
law, which resulted in large quantities of biomass being transported from Africa, Asia,
Canada, USA, Brazil and other regions). The GHG emitted by these continuous
transportations is substantial and is counterproductive in terms of GHG mitigation strategies.
o In addition to GHG biomass as a fuel produces air pollution: CO, formaldehyde,
acetaldehyde and particulates (in some cases at levels above those from traditional coal).
• When alcohols are oxidized, formaldehyde, acetaldehyde and other aldehydes are
produced. When only a 10% mixture of ethanol is added to gasoline (as is common
in American E10 gasohol and elsewhere), aldehyde emissions increase 40%.
• The energy balance (EROEI) (the amount of energy put into the manufacturing of the
fuel compared to the amount of energy released when it is burned in a vehicle) of
biofuel is low (1-2 in most studies) and in some studies negative (<1) when the
industrial processes needed to grow the plants (fertilizers and irrigation), extract, refine
and transport the fuel from the plants is taken into account.
In developing countries biomass fuel is used inefficiently for heating and cooking, causing
smoke indoors and possibly fatal intoxication, particularly in children.
Friends of the Earth state that "the current rush to develop biofuels on a large scale is ill-
conceived and will contribute to an already unsustainable trade whilst not solving the
problems of climate change or energy security".
• Renewable energy facilities are rapidly growing worldwide with a 60% increase
between 2009 and 2011. Investments rose from 39 billion dollars equivants in 2004 to
257 billion in 2011. Growth is highest in wind and solar sector. More than 200 million
households use solar hot water collectors today, 80 % of which are in China. In 2011, the
International Energy Agency said that solar energy technologies could provide a third of
the world’s energy by 2060 if politicians commit to limiting climate change.
• At least 118 countries, more than half of which are developing countries, had renewable
energy targets in place by early 2012.
• Thousands of cities and local governments around the world also have active policies, or
targets for renewable energy and climate change mitigation.
• Almost two-thirds of the world’s largest cities had adopted climate change action plans
by the end of 2011, with more than half of them planning to increase their uptake of
renewable energy. There is increasing co-operation among cities, including the EU
Covenant of Mayors (with over 3,000 member cities) and some 100 demonstration cities
• Next slides show various diagrams of the fast growth of the renewable energy facitities
The figure to the right
shows the evolution of the
different power plant
between 1970 and 2010
either with China included
(top) or without China
(bottom) . For each year the
capacity added in that year
It is clear that there is a
steady increase in the
added capacity of
renewable energy plants
during the last 10 years.
The rise in coal plants
added is mainly due to the
expansion of coal plants in
China. Excluding the data
from China, the added
capacity of renewables in
2010 was higher than the
added capacity of
traditional power plants,
whereas coal is phasing
The figure below shows a similar evolution of the different power plant markets in the European
Union (EU27) between 1970 and 2010. There is a steady increase in the added capacity of
renewable energy plants during the last 10 years, and, in addition, coal plant additions are much
lower than is seen mundially. Gas remains the largest power plant market, but gas is emitting 50%
less CO2 than coal and oil. The EU is therefore an example for the World.
As shown in the figure to the right,
there are large differences in
renewable energy development
among the different countries in
the European Union. Sweden uses
nenewable energy for > 45% of its
energy consumption, while
Belgium only 6 %. The best score
in Europe goes to Norway, where
60 % of energy consumption is
shared by renewables (see
• Different scenarios (from IEA and Greenpeace) of further growth of renewable energy have been
advanced up to 2030. Solar and wind energy are the most promising. Wind energy is predicted to
grow from 238 GW to 1300-2900 GW, solar photovoltaics from 70 GW to 700-1700 GW and
concentrating solar power from 2 to 140-700 GW.
• An independent study estimated that in 2030 the world can be fully powered by electricity and
electrolytic hydrogen using only a mix of the following facilities:
3,800,000 5 MW wind turbines,
49,000 300 MW concentrated solar plants,
40,000 300 MW solar photovoltaic power plants,
1.7 billion 3 kW rooftop photovoltaic systems,
5350 100 MW geothermal powerplants,
270 new 1300 MW hydroelectric power plants,
720,000 0.75 MW ocean wave devices,
490,000 1 MW tidal turbines
These facilities would have a total capacity of 53 TW and would require only 0.41% and 0.59% more
of the world’s land for footprint and spacing, respectively. Energy costs with this system mix are
expected to be similar to today's fossil and nuclear energy costs
• A 2009 paper in the Proceedings of the National Academy of Sciences shows that a global network of
windmills operating at 20% of capacity could produce 83 TW — about five times the current energy
consumption worldwide (~17 TW). The latter estimate is much higher than a previous evaluation of
global wind power (Archer and Jacobson 2005), which estimated a similar network’s output at 14 TW.
Wind and solar energy devices for electricity generation can be deployed in a decentralized way, favoring
energy safety. This is an important advantage over fossil energy-based power stations that not
infrequently suffer of blackouts. See list of power failures in reference1 and 2.
Sector share of energy consumption by energy
In the industrial, residential and commercial
sector fossil energy supply can be replaced by
a mix of renewable energy sources by 2030
(see previous slides).
Coal in power plants for electricity generation,
can be replaced by renewable energy and
backed up by nuclear energy generated by fast
A major challenge for the near future will be
replacement of oil used in transportation. As
of 2011 there were more than one billion cars
in use in the world,and these are on the
average only in use for 1 hour/24 with 1.6
people/car. Only around 70 million use
alternative fuel and advanced technology (<
7%). A switch to alternatives will take
time but is actually in progress (read
more). Leading countries are Brazil and
Alternatives to petroleum-based vehicles are:
– Vehicles that use natural gas (temporarily), bioethanol, flexible-fuel, biodiesel or hydrogen.
– Electric vehicles: battery electric vehicles, plug-in hybrid electric vehicles, hybrid electric
vehicles, and hydrogen fuel cell vehicles.
For large distance and heavy truck traffic or if speed is mandatory, present electric vehicles are not
suited. A switch from road to rail (electric) seems imperative, and is currently developed in
Synthetic fuel and biofuels are also alternatives of kerosene as jet fuel, several companies already
flying with this fuel.
Biofuels can replace fossil liquid fuels only for 10-15% due to lack of adequate land and
The most difficult change that will be necessary is our change in behavior. The era of easy point-
to-point transportation, with easily obtainable oil, at high speed, as single driver, at whatever
time, and as often as we like, has ended. We, in developed countries, should realize that people
in developing countries have the same right to drive cars as we. China built > 14 million new cars
in 2011, India 3 million (as many as the U.S.) [Ref]