Yeang K., Woo L. Dictionary of Ecodesign: An Illustrated Reference
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Figure 47 Mixed-mode design using various generic passive solar systems
well with catalysts made of nickel, which is
much less expensive than platinum. MCFCs
exhibit up to 60% efficiency, and this can rise
to 80% if the waste heat is utilized for
cogeneration.
Two major difficulties with molten carbo-
nate technology put it at a disadvantage com-
pared with solid oxide cells: one is the
complexity of working with a liquid electrolyte
rather than a solid; the other stems from the
chemical reaction inside a molten carbonate
cell. Carbonate ions from the electrolyte are
used up in the reactions at the anode, making it
necessary to compensate by injecting carbon
dioxide at the cathode. In addition, the elec-
trolyte used in MCFCs is highly corrosive,
limiting some of its potential applications.
MCFCs are used for natural gas- and coal-
based power plants for electrical utility, indus-
trial, and military applications. See also:
Fuel
cells
Monitoring Regulatory surveillance to determine
compliance with legal or code requirements.
For example, USEPA monitors toxic levels in
air, water, and soil.
Monoculture Agricultural cultivation of one
crop rather than diverse types of crop. This
often results in crop vulnerability to insect
pests, requiring an increase in the use of pesti-
cides, pollution from which seeps into the
groundwater.
Monoculture ecosystem Design site classifi-
cation measured by the condition of ecosystem
characteristics and features. Ecosystems used for
agricultural purposes, but whose ecological
succession is limited by human controls to
maintain high levels of productivity. See also:
Ecodesign site types
Montmorillonite Main constituent of the vol-
canic ash product bentonite. It is used in oil
drilling as a soil additive to hold water because
of its clay-like water-swelling properties.
Montreal Protocol on Substances that Deplete
the Ozone Layer International agreement
designed to protect the stratospheric ozone
layer by phasing out production of substances
that cause ozone depletion. The Montreal
Protocol, which supplemented the Vienna
Convention for the Protection of the Ozone
Layer (Vienna, 1985), was originally signed in
1987 and became effective on January 1, 1989.
It was signed by 29 countries in Montreal. The
Protocol is designed to regulate the production
and consumption of ozone-depleting sub-
stances. The signatories agreed to reduce pro-
duction and consumption of CFCs by half by
1998 and to freeze production and consump-
tion of halons by 1992. Developing countries
were granted a 10-year grace period to meet
their obligations.
The Protocol has been substantially amended
five times, in 1990 (London), 1992 (Copenhagen),
1995 (Vienna), 1997 (Montreal), and 1999
(Beijing). The London Agreement of 1990 sti-
pulated that the production and consumption
of compounds that deplete ozone in the stra-
tosphere—chlorofluorocarbons (CFCs), halon
(bromofluorocarbons), carbon tetrachloride, and
methyl chloroform—were to be phased out by
2000 (2005 for methyl chloroform). See also:
Ozone-depleting substance
Movable insulation A device that reduces heat
loss at night and during cloudy periods, and redu-
ces heat gain during the day in warm weather.
A movable insulator could be an insulating
shade, shutter panel, or curtain.
MTBE See:
Methyl tertiary butyl ether
Mulch Layer of material, such as wood chips,
straw, or leaves, placed around plants to hold
moisture, prevent weed growth, and enrich the soil.
Mulch 159
Muellerian mimicry Evolution of two species,
both of which are unpalatable and have defen-
sive mechanisms, to resemble each other. See:
Batesian mimicry
Multijunction One of the basic types of pho-
tovoltaic device. See also:
Photovoltaic device
Murocaust Similar to a hypocaust, except that
a massive wall with air channels is used, and
the air flow is vertical instead of horizontal. See
also:
Hypocaust
Mutualism Type of symbiosis in which both
members of the partnership benefit. See also:
Amensalism; Commensalism; Parasitism; Symbiosis
MW See: Megawatt
Mycorrhizal fungi Inhabit the root systems of
trees, and pump soil nutrients into the roots.
These fungi also protect plants from other
harmful fungi; they knit the soil together to pre-
vent erosion; and they influence which plants
will grow in a particular area.
160 Muellerian mimicry
N
Nanocrystal solar cell A third-generation solar
cell, developed in 2005 at the US Department
of Energy’s Lawrence Berkeley National Labora-
tory in conjunction with University of California
at Berkeley. It is the first ultra-thin solar cell
comprised entirely of inorganic nanocrystals,
and spin-cast from solution. The cost and
manufacture are comparable with solar cells
made from organic polymers. They are more
stable in air because they contain no organic
materials. They combine the properties of
organics with the ability to retain the broadband
absorption and superior transport properties of
traditional photovoltaic semiconductors. They
have the cost-reduction potential that has
made organic cells a viable alternative to
conventional semiconductor counterparts. Rod-
shaped nanometer-sized crystals of two semi-
conductors, cadmium–selenide (CdSe) and
cadmium–telluride (CdTe), are synthesized sepa-
rately and then dissolved in solution and spin-
cast onto a conductive glass substrate. The
resulting films, which are about 1000 times thin-
ner than a human hair, have comparable con-
version efficiencies as the best organic solar cells.
It is still substantially lower than conventional
silicon solar cell thin film.
Unlike conventional semiconductor solar cells,
in which an electrical current flows between
layers of n-type and p-type semiconductor films,
with these new inorganic nanocrystal solar cells,
current flows due to a pair of molecules that
serve as donors and receptors of electrical char-
ges, also known as a donor–acceptor hetero-
junction. This is the same mechanism by which
current flows in plastic solar cells. The two
semiconductor films are electrical insulators in
the dark, but when exposed to sunlight they
undergo a rise in electrical conductivity, as much
as three times more. Sintering the nanocrystals
was found to significantly enhance the perfor-
mance of these films. Unlike plastic solar cells,
performance of which deteriorates over time,
aging seems to improve the performance of
these inorganic nanocrystal solar cells. Accord-
ing to the Energy Foundation, if the available
residential and commercial rooftops in the USA
were to be coated with solar cell thin films, they
could furnish an estimated 710,000 MW of
electricity across the country, which is more
than three-quarters of all the electricity that the
USA is currently able to generate.
Nanoenergy Use of nanomaterials—typically
on the scale of billionths of a meter, or 10,000
times smaller than a human hair—to design
materials with properties tailored to specific
needs, such as strong, lightweight materials,
new lubricants, and more efficient solar energy
cells. By building structures one atom at a time,
the materials may have enhanced mechanical,
optical, electrical, or catalytic properties. See
also:
Nanotechnology
Nanometer Distance measure equivalent to
one billionth of 1 meter.
Nanotechnology Field of applied science that
deals with the control of matter on an atomic
and molecular scale. Generally, nanotechnology
deals with materials or devices approximately
100 nanometers or smaller. Nanotechnology is
a multidisciplinary field, including applied phy-
sics, materials science, interface and colloid
science, device physics, supramolecular chemistry
(referring to the area of chemistry that focuses
on the noncovalent bonding interactions of
molecules), self-replicating machines and robot-
ics, chemical engineering, mechanical engi-
neering, biological engineering, and electrical
engineering. Grouping of the sciences under the
umbrella of “nanotechnology” has been ques-
tioned on the basis that there is little actual
boundary-crossing between the sciences that
operate on the nano-scale. Instrumentation is
the only area of technology common to all dis-
ciplines. There is ongoing research to determine
future applications of various fields of nano-
technology, as well as the health safety of
nanoproducts. See also:
Nanocrystal solar cell
Naphtha jet fuel Common jet fuel used in
civilian aviation. Fuel in naphtha–kerosene is
used to enhance cold-weather performance. It is
known as JET B and has a lighter composition
than an unleaded/paraffin oil-based fuel classi-
fied as JET A-1, which is produced to interna-
tional specifications. JET B’s lighter composition
makes it more dangerous to handle, so it is
restricted only to areas where its cold-weather
characteristics are absolutely necessary. See
also:
Kerosene-type jet fuel; Jet fuel
NAPL See: Nonaqueous-phase liquid
National Electrical Code (NEC) Guidelines for
all types of electrical installation. From 1984,
the NEC has contained Article 690, “Solar Pho-
tovoltaic Systems”, which provides instructions
on installing photovoltaic systems.
National Energy Modeling System Computer-
based model created by the Energy Information
Administration division of the US Department
of Energy. The system is a model of energy
markets through 2025, and projects energy,
economic, environmental, and security impacts
of US energy policies and energy markets. This
model is particularly helpful for long-range
planning, public policy implementation, and
energy legislation.
National Energy Policy Developed in 2001 in
the USA, its three principles are: provide a long-
term, comprehensive energy strategy; advance
new, environmentally friendly technologies to
increase energy supplies and encourage cleaner,
more efficient energy use; and integrate energy,
environmental, and economic policies.
National Environmental Policy Act Passed by
US Congress in 1970, the Act seeks to protect
the environment, and requires that environmental
factors are considered when federal agencies
make decisions.
Native Indigenous to a specific area or region.
Natural Indigenous or untouched by civilization.
Natural cooling Space cooling achieved by
shading, natural (unassisted, as opposed to
forced) ventilation, conduction control, radia-
tion, and evaporation. See also:
Passive cooling
systems
Natural draft Draft (air movement) caused by
temperature differences in the air.
Natural gas Underground deposits of gases.
Mixture of hydrocarbons and small quantities
of various nonhydrocarbons in the gaseous
phase or in solution with crude oil in natural
underground reservoirs. Natural gas consists of
50–90% methane (CH
4
) and small amounts of
heavier gaseous hydrocarbon compounds such
as propane (C
3
H
8
) and butane (C
4
H
10
). Natural
gas is clean-burning and produces fewer
162 Naphtha jet fuel
harmful emissions than reformulated gasoline or
diesel. See also:
Compressed natural gas; Liquefied
natural gas
Natural gas car Automobile powered by nat-
ural gas or propane; does not emit carcinogenic
particles and produces fewer emissions that are
harmful to the environment. See also:
Compressed
natural gas; Liquefied natural gas
Natural resource Resource that occurs in nature,
which can be used to meet human needs.
Natural ventilation Ventilation that is created
by the differences in the distribution of air pres-
sures around a building. Air moves from areas
of high pressure to areas of low pressure, with
gravity and wind pressure affecting the airflow.
The placement and control of doors and windows
alters natural ventilation patterns.
Near-neat fuel Fuel that is virtually free from
admixture or dilution. The usual additives to fuel
include detergents and corrosion inhibitors.
Neat alcohol fuel Straight or 100% alcohol,
usually in the form of ethanol or methanol.
Neat fuel Fuel that is free from admixture or
dilution with other fuels.
NEC See:
National Electrical Code
Neritic 1. Pertains to the shallow area around
a lake or ocean that border the land.
2. Also used to describe the species that live
along the water’s border.
Net building load Energy required to satisfy
needs of a specific building and its occupants.
New town Planning model that combines devel-
oped urban living and a natural environment.
Most of the planned communities create cluster
residential and commercial development and
extensive green areas.
New urbanism Movement, begun in the USA,
that opposes suburban sprawl, advocating
instead the reintroduction of the concept of
community in urban planning.
Niche In ecology, the effect an environment
has on an organism, and the effect an organism
has on the ecosystem.
Niche diversity Relates to both species and
habitat diversity. Relationships between organisms
and their habitat.
NIMBY See:
Not in my back yard
Nitric acid (HNO
3
) A highly corrosive and
toxic strong acid. It is a source of nitrous oxide
(N
2
O), a powerful greenhouse gas.
Nitrogen cycle Nitrogen circulation through
plants and animals and back to the atmo-
sphere. A disruption of the cycle may alter the
ecobalance.
Nitrogen dioxide (NO
2
) Poisonous gas used in
making nitric acid and as a rocket-fuel oxidizer.
Also formed from automobile exhausts.
Nitrogen dioxide-absorbing cement See:
Pollution-absorbing cement
Nitrogen fixation Conversion by bacteria of bio-
logically unusable nitrogen gas (N
2
) into biologi-
cally usable ammonia (NH
3
) and nitrates (NO
3
).
Nitrogen oxides (NO
x
) Major air pollutants
and toxic chemicals. Group of highly reactive
gases that contain nitrogen and oxygen in vary-
ing amounts. Most of the nitrogen oxides are
colorless and odorless, but nitrogen dioxide
(NO
2
) is reddish brown. Fossil fuels such as coal
Nitrogen oxides (NO
x
) 163
and gasoline release NO
x
into the atmosphere
when burned. NO
x
can also be formed naturally.
NO
x
reacts with the Sun’s radiation and other
chemical compounds, such as hydrocarbons, to
form ground-level ozone. It contributes to the
formation of acid rain and smog; eutrophication
of lakes, streams, coastal waters, and rivers; and
global warming. NO
x
and the pollutants formed
from them can be transported over long distances,
following the pattern of prevailing winds. This
means that problems associated with NO
x
are
not confined to areas where NO
x
are emitted.
See also:
Air pollutants; Toxic chemicals
Nitrous oxide (N
2
O) Powerful greenhouse gas
with global warming potential 296 times more
than that of carbon dioxide (CO
2
). It has an
atmospheric lifetime of approximately 120 years.
It is 310 times more effective in trapping heat in
the atmosphere than CO
2
over a 100-year period.
Major sources of N
2
O include chemically altered
agricultural soil, agricultural residue, animal
manure, sewage treatment, fuel combustion,
adipic acid production, and nitric acid produc-
tion. N
2
O is also emitted naturally from a wide
variety of biological sources. See also:
Adipic
acid; Nitric acid
Nocturnal cooling The effect of cooling by the
radiation of heat from a building to the night sky.
Noise pollution Ambient noise at high levels
from various sources; can have adverse effects
on human health and other fauna. See also:
Decibel
Nonaqueous-phase liquid (NAPL) Contaminants
that remain undiluted as the original bulk liquid
in the subsurface, such as spilled oil. See also:
Dense nonaqueous-phase liquid; Light nonaqueous-
phase liquid
Nonattainment area Geographical area in which
the level of criteria air pollutant is higher than
the level allowed by government standards. See
also:
Attainment area
Nonbiodegradable Matter that will not decom-
pose under normal atmospheric conditions.
Nonimaging optics In solar thermal energy,
energy collection can be improved by using
reflectors designed to be nonimaging in order to
concentrate the radiation over an area uni-
formly. Imaging optics focus the radiation and
create “hot spots” on the collectors.
Nonpoint-source pollution Pollution discharged
over a wide area. This diffused pollution is
caused by sediment, nutrients, and organic and
toxic substances resulting from land-use activ-
ities, and is carried to and deposited into rivers,
lakes, streams, coastal waters, or groundwater.
Includes sediments, nutrients, pesticides, patho-
gens (bacteria and viruses), toxic chemicals, and
heavy metals that run off from agricultural land,
urban development, or roads. See also:
Point-
source pollution
Nonrecyclable Not able to be recycled and
used again.
Nonrenewable energy Irreplaceable sources of
energy: coal, oil, and natural gas. These sources
are considered nonrenewable because it takes
eons to produce them, and they cannot be
replaced once they have been consumed. See
also:
Renewable energy
Nonrenewable resource Resource that cannot
be replaced as it is used. Fossil fuels, such as
coal and oil, form at such a slow rate that they
are considered nonrenewable.
North True north is a navigational term refer-
ring to the direction of the north pole relative to
the navigator’s position. Magnetic north refers to
the direction of the magnetic north pole.
164 Nitrous oxide (N
2
O)
Not in my back yard (NIMBY) Position of resi-
dents who oppose local unwanted land uses,
such as toxic waste dumps, landfills, incinerators,
airports, or freeways close to their homes. See
also:
Locally unwanted land uses
Nuclear energy Energy produced from split-
ting atoms of radioactive materials, such as
uranium, which produces radioactive wastes. It
should be noted that fusion also provides energy
from lighter element nuclides.
Nuclear fusion plant Because a fusion reactor
releases far less radioactive pollution than an
ordinary fission nuclear plant, active research is
being conducted to determine its feasibility.
According to the International Thermonuclear
Experimental Rector consortium, fusion power
offers the potential of “environmentally benign,
widely applicable and essentially inexhaustible”
electricity, properties that will be needed as world
energy demands increase while simultaneously
greenhouse gas emissions must be reduced; but
a fusion power plant is still decades away
despite US$20 billion of extensive research
done so far. Researchers remain skeptical about
results that will lead to anything practical or
useful in producing electricity through fusion
power. Engineering problems still exist, along
with prohibitive costs of building and difficulties
of repairing and maintaining the reaction vessel.
In addition, a massive “blanket ” of lithium and
rare metals—which must surround the fusion-
generating plasma in order to absorb its emitted
neutrons—will degrade and become radioactive
over time, requiring regular dismantling and
replacement. See also:
Nuclear power plant
Nuclear power plant Power plant that relies
on the process of nuclear fission. In this process,
the nucleus of a heavy element, such as uranium,
splits when bombarded by a free neutron in a
nuclear reactor. The fission process for uranium
atoms yields two smaller atoms, one to three free
neutrons, plus an amount of energy. Because
more free neutrons are released from a uranium
fission event than are required to initiate the
event, the reaction can become self-sustaining—
a chain reaction—under controlled conditions,
thus producing a tremendous amount of energy.
In most of the world’s nuclear power plants, heat
energy generated by burning uranium fuel is col-
lected in ordinary water and carried away from
the reactor’s core either as steam in boiling-water
reactors, or as superheated water in pressurized-
water reactors. In a pressurized-water reactor, the
superheated water in the primary cooling loop is
used to transfer heat energy to a secondary loop
for the creation of steam. In either a boiling-water
or pressurized-water installation, steam under
high pressure is the medium used to transfer the
nuclear reactor’s heat energy to a turbine that
mechanically turns a dynamo-electric machine, or
electric generator. Boiling-water and pressurized-
water reactors are called light-water reactors,
because they use ordinary water to transfer the
heat energy from reactor to turbine in the electricity
generation process. In other reactor designs, the
heat energy is transferred by pressurized heavy
water, gas, or another cooling substance.
A current concern in the nuclear power field is
the safe disposal and isolation of either spent fuel
from reactors or, if the reprocessing option is used,
wastes from reprocessing plants. These materials
must be isolated from the biosphere until the
radioactivity contained in them has diminished
to a safe level. Under the Nuclear Waste Policy
Act of 1982, as amended, the US Department of
Energy has responsibility for development of the
waste disposal system for spent nuclear fuel and
high-level radioactive waste. Current plans call for
the ultimate disposal of the wastes in solid form
in licensed deep, stable geological structures.
Nuclear waste facility Facility to dispose of
nuclear waste in which the waste is sealed in a
ceramic material. The ceramic material is then
placed in corrosion-resistant containers and buried
Nuclear waste facility 165
in deep earth chambers. The facility must last
up to 10,000 years or longer.
Nutrient Substance that an organism gets from
the environment to use as a source of energy or
growth. Usually associated with substances used
for plant growth.
Nutrient cycling Natural process of cycles and
recycles of decomposition of plant and organic
matter to provide soil nutrients for new generations
of plants and animals.
Nylon Generic designation for a family of syn-
thetic polymers first produced in 1935. Plastic is
made from petrol, and petrol cannot degrade
very easily. Nylon can also be made from plas-
tic. Most nylon products take a long time to
degrade and are classified as nonbiodegradable.
Research continues to develop biodegradable
nylon.
Nylon 6 One of the newly developed biode-
gradable nylons. It is a recyclable polymer; used
for textiles.
166 Nutrient
O
Occupational Safety and Health Administration
(OSHA) Division of the US Department of Labor.
Enforces safety and protection of employees in
their workplace.
Occupied space The space within a building
or structure that is normally occupied by people
and that may be conditioned (heated, cooled,
and/or ventilated).
Ocean energy systems Energy-conversion tech-
nologies that harness the energy in tides, waves,
and thermal gradients in the oceans.
Ocean thermal energy conversion (OTEC)
Process or technologies for producing energy by
harnessing the temperature differences (thermal
gradients) between ocean surface waters and
ocean depths. Warm surface water is pumped
through an evaporator containing a working
fluid in a closed Rankine-cycle system. The
vaporized fluid drives a turbine/generator. Cold
water from deep below the surface is used to
condense the working fluid. Open-cycle OTEC
technologies use ocean water itself as the work-
ing fluid. Closed-cycle OTEC systems circulate
a working fluid in a closed loop. A working 10
kilowatt, closed-cycle prototype was developed by
the Pacific International Center for High Tech-
nology Research in Hawaii with US Department
of Energy funding, but was not commercialized.
Octane An alkane with the chemical formula
CH
3
(CH
2
)
6
CH
3
. It has 18 isomers. Flammable
liquid hydrocarbon found in petroleum. Used as
a standard to measure the anti-knock properties
of motor fuel.
Octane rating Indicates how much fuel can be
compressed before it spontaneously ignites. If
gas ignites by compression, rather than because
of the spark from the spark plug, it causes
knocking in the engine, which can damage an
engine.
Offgassing Release of gas or vapor into the air.
Off peak The period (time of day) of low energy
system demand, as opposed to maximum, or
peak, demand. See also:
On-peak energy
Offset allowances See: Emissions trading
Ohm Measure of the electrical resistance of a
material, equal to the resistance of a circuit in
which the potential difference of 1 volt produces
a current of 1 ampere.
Ohm’s law In an electrical circuit, a current (I)
through a resistor (R) produces a voltage (V) drop
according to the following equation: V = I R.
Oligotrophic Pertaining to a lake or other body
of water characterized by extremely low nutri-
ent concentrations, often with very limited plant
growth, but with high dissolved oxygen levels.
See also:
Eutrophic; Mesotrophic
One-hundred-year floodplain Area that has a
1% chance of being flooded in a given year.