Transcript living on renewables ppt

Living On RenewabLES
Views on Sustainability
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Big Corporation
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Oil Company
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Broad Scale
Large Companies
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Sustainability often means staying in business and
continuing to grow.
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It has a financial sense to it.
Oil Companies
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Must have adequate reserves of oil to meet immediate
needs,
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But also have a stake in energy technology that will
replace oil.
“Big Picture”
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Using technology to de-couple GDP from
environmental damage.
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i.e. Don’t subsidize pollution - make the environmental
impact part of the real cost.
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Let GDP grow, and reduce environmental damage,
using market forces such as carbon trading.
Anti-Free Market
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Some think the free market is the CAUSE of the
problem, not the solution.
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i.e. the relentless drive for growth is responsible for the
damage
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Then sustainability means capping or reducing GDP.
Social
System
Sustainable Development
Survival and health
Spatial
of the physical and
Industrial Ecology
Scale
bio-systems
Industrial
Relationship between
System
Design for Environment industrial and
Design for the
environment
natural systems
is the objective
P C & P Intervention to limit
Product
System
and control pollution
Product lifetime
Human lifetime
Time Scale
Civilization lifetime
Natural?
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Natural is a tricky term to use...
•a
: being in accordance with or determined by
nature
•b
: having or constituting a classification based on
features existing in nature
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Are humans natural? If so, are their actions also
natural?
Natural
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For the purposes of this discussion, we will assume
natural means everything on the planet that is NOT
associated with humans or human behavior.
Ecological Metaphor
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Based on observation that natural and industrial
systems have certain features in common:
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Resource transformation
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Waste generation
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Exist in ecosphere
Resource transformation
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Natural and industrial systems transform resources: materials
and energy.
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Nature through growth, industry through manufacturing
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Plants: solar powered, carbon dioxide & minerals as raw
materials
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Animals: fueled by plants (or other animals), raw materials are
plants, minerals or other animals.
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Industrial: fueled by fossil fuels, raw materials from crust,
oceans, and living things.
Waste Generation
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Natural system: metabolism and death;
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Recycled with 100% efficiency, uses solar power
Industrial system: emissions, heat, and obsolesence.
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Recycled at various levels (all <100%), uses nonrenewable energy to do so.
Ecosphere
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The ecosphere provides raw materials, primary resources, is a
reservoir for waste, recycles waste,
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Provides water and air, protection from UV radiation, etc.
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Both systems exist within the ecosphere.
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The natural system has demonstrated the ability to continue
in equilibrium with the ecosphere.
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The modern industrial system appears to be at risk here.
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So, can we learn from the natural systems?
Elements
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Living things require carbon, nitrogen, hydrogen and
oxygen.
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These make carbohydrates, fats, and proteins
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The carbon cycle, nitrogen cycle and hydrological cycle
are important recycling routes for these critical
elements.
Carbon Cycle
CO2 in Atmosphere
photosynthesis
decomposition
Diffusion
decomposition
Animal
metabolism
photosynthesis
Bacterial deposition
Coal
Aquatic biomass
Calcereous deposits
Oil, gas
Limestone
Elements
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Industrial systems require many different elements most of the periodic table, including Carbon.
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As in nature, processes that use carbon (coal, oil,
gas...) return it to the atmosphere. However, the
recovery rates of natural systems are not high enough
to account for this.
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Hence increase in carbon in the atmosphere since
1850.
Carbon Cycle
CO2 in Atmosphere
Coal
Limestone
Oil, gas
Natural Ecosystem
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Uses few elements (mostly C, N, H, and O)
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Is cyclic (materials circulate and transform
continuously)
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Subsystems (have evolved that use “waste” as food)
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Closed Loop (no waste! see subsystems)
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Indicator of wellbeing: Equilibrium
Industrial System
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Uses most of the periodic table
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Is linear (transforms materials in products and waste)
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Lack of subsystems (that use waste as a resource)
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Open Loop (waste destroys sources they require)
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Indicator of well being: Growth
Differences
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Industrial systems don’t have subsystems to handle
waste, or the subsystems cannot handle the volume of
waste produced.
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Equilbrium vs. Growth
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Growth generates increasing waste.
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If growth is required, a method for addressing waste
is also required.
Wait a minute!
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Natural systems in equilibrium?
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There are fluctuations, but it is a stable, resilient
system. Consider the CO2 curve we looked at increases lead to global changes that result in cooling
that result in reduced CO2 that result in warming...
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Cyclical is a form of equilibrium.
Energy
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The average power use in a developed country ranges
between 4 and 14 kW per person.
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This turns out to be about 120-450 GJ/year per person.
Energy Consumption
Sector
Proportion
(%)
Transportatio
n
32
Domestic
29
Industry
35
Other
4
Energy Sources
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Only four sources of energy on earth:
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Sun (wind, wave, hydro, photochemical,
photoelectic)
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Moon (tides)
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Radioactive decay (geothermal heat, nuclear power)
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Hydrocarbon fuel (really sun energy in fossilized
form)
Wind
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Problem is power density (power per unit
area that can be harvested).
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On land, 2 W/m2. Offshore, about 3 W/m2.
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So how does this help in China? 7,012 m2
per person of land area in the whole country.
So 14kW per person.
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India: 2,590 m2 per person, so 5 kW per
person.
So basically we would have to cover the
entire country in windmills to meet energy
needs.
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Solar
Solar energy density varies with distance from
the equator. Temperature regions can get up
to 50 W/m2.
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Solar thermal (50% efficiency) generates low
grade heat (hot water). Useful for home use,
but nothing else
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PV (10-20%) so between 5 and 10 W/m2. Like
wind, would need vast areas to meet human
needs.
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Flora (burn plants or ferment them, or eat
them). Efficiency is about 1%. And we use
extra energy to raise the plants, reducing
effective efficiency to about 0.5%.
Hydro
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Power available depends on altitude and rainfall.
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Mountain regions can provide 0.2 W/m2.
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Not much, but these are generally uninhabited regions.
Norway (66,000 m2/person) gets significant energy
from hydro.
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Waves
Make waves move something (a
barrier with a turbine). Energy is
measured per length, not per area. As
much as 40kW per meter.
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It is difficult to capture the energy estimates are 1/3 efficiency. Need a
long coast line for this to be an option.
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If you have 50 million residents, would
need 3,700 km to generate 1
kW/person.
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Maintenance is a real issue.
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Tidal
Lunar power (tides) can generate about 3 W/m2. This
is similar to wind power, but need coastal areas to
capture.
Geothermal
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Heat conducts from core
of the earth, augmented
by unstable element
decay in the crust.
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To make electricity, we
need at least 200C
temperatures - which
often means drilling 10
km.
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Some places this is
possible - Iceland, New
Zealand, Yosemite...
Conclusions?
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No single renewable will do the job effectively.
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Consider - if you cover a significant fraction of your country with
solar panels, where do you live, grow food, etc.?
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There is a significant cost in both initial construction and in
maintenance. (2% of land based wind mills are destroyed by
lightning each year, e.g.)
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There is opposition from environmentalists about paving the
country with machinery.
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Abundant pollution-free energy is not available yet...
Sustainable Materials
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Sustainable material should be drawn from a source
that is renewable:
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either grows as fast as we use it, or reverts to
original state in an acceptable period of time
It should be part of a cycle (like the natural cycles
around C, N, H and O)
Renewable Materials
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Plants seem like a good choice - trees, bast fibers,
seed hairs...
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However today wood is harvested faster than it grows,
so it is a diminishing resource.
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Also the wood we use is cut, dried, chemically treated,
transported... all with non-renewable resources.
Recyclable Materials
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If we can’t be truly renewable, can we be recyclable?
At least, for all practical purposes...
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Construction uses more materials than any other
sector, so let’s look at that. Much construction happens
in less developed countries where steel, concrete and
brick are not easy to get.
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This could provide us with some interesting ideas.
Rammed
Earth
and
Adobe
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everywhere.
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Mix it with straw or hair,
some lime
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Pressurize it (stomp it
with boards)
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You have rammed
earth.
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Straw bales are a waste product of modern agriculture.
They can be used as building blocks, with a plaster or
wood surface.
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Low thermal conductivity, low heat capacity.
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Reed has been used for thatched roofs
for a long time - resistant to water, has a
life of up to 80 years.
Straw and Reed
Hemp, Flax, Kenaf
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These are fast growing grasses. The fibers (bast
fibers) from the stems are strong and light.
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Textiles can be made from them, as well as reinforced
concrete (e.g. hempcrete). Hempcrete is about 75% by
volume fiber. And it grows as fast as it is harvested.
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Hempcrete sequesters about 0.3 kg carbon/kg
Stone and Lime
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OK, Stone isn’t renewable in any obvious sense. But it
has a huge reserve except the “dressed” stone and
marbles.
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Field stone is readily available in large quantities and
can make non-load bearing boundaries.
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The use of lime mortar can make stone structures
suitable for load carry.
Quasi-Sustainable
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The previous materials are nice, but not diverse
enough to handle all situations.
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Quasi-sustainable materials mean materials that are
drawn from a large resource base, so large that even
with exponential growth there is no risk of exhaustion.
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Let’s look at the composition of the earth’s crust for
guidance.
Elements in the earth’s crust
Element
Weight %
Oxygen
46.7
Silicon
27.7
Aluminum
8.1
Iron
5.1
Calcium
3.6
Sodium
2.8
Potassium
2.6
Magnesium
2.1
Titanium
0.6
Hydrogen
0.14
Phosphorous
0.13
Carbon
0.09
All others
<1
Back to Energy
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We have lots of materials in the crust - but it takes
energy to extract them
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Basically it is all about the energy.
Exercise
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Consider The Netherlands, with a population of about
16.5 million. If their average power draw per person is
6.7 kW, how much of the land would have to be taken
up by wind turbines to meet the country’s energy
needs? (Assume a load factor of 50%)