Yeang K., Woo L. Dictionary of Ecodesign: An Illustrated Reference

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Urban and suburban developments and their

accompanying paved roads and surfaces have

increased the probabilities of ﬂooding.

On-peak energy Energy supplied during periods

of relatively high system demand as speciﬁed by

the supplier. See also:

Off peak

Once-through system design strategy One of

four design strategies to manage materials and

energy in the built form and its servicing sys-

tems. Resources are consumed with the belief

that they are unlimited. Once they have fulﬁlled

their usefulness, they are discarded as waste. Uses

the environment as its ultimate sink. See also:

Closed-circuit system design strategy; Combined

open-circuit system design strategy; Open-circuit

system design strategy

Open access The ability to send or wheel

electric power to a customer over a transmission

and distribution system that is not owned by the

power generator (seller).

Open access system Also known as the “tragedy

of the commons”. Commonly held resource for

which there are no management rules. Experience

has shown that common resources are often

exploited or degraded by some of the owners.

Open-circuit system design strategy One of

four design strategies to manage materials and

energy in buildings and their servicing systems.

Like the once-through system, it uses the envir-

onment as a sink to receive waste products, but

in this system the emissions do not exceed the

ability of the ecosystem to absorb them. The

wastes are pretreated before they are discharged.

See also:

Closed-circuit system design strategy;

Combined open-circuit system design strategy;

Once-through system design strategy

Open-loop active system Solar water heating

system. Pumps circulate water through the solar

collectors. These systems are most effective in

geographical areas that do not freeze for long

periods and do not have hard or acidic water.

Open-loop geothermal heat pump system Also

known as a direct system. Circulates water drawn

from a ground or surface water source. Once

the heat has been transferred into or out of the

water, the water is returned to a well or surface

discharge (instead of being recirculated through

the system). This option is practical where there

is an adequate supply of relatively clean water,

and all local codes and regulations regarding

groundwater discharge are met.

Open system Area in which there is a supply

of chemical elements used to support plant

and animal communities in one ecosystem

and a simultaneous loss of biomass and che-

mical elements from the area outside of that

ecosystem.

Operational costs Direct monetary costs of

operating a business or facility.

Organic Contains carbon, and is composed of

living or previously living matter.

Organic agriculture Concept and practice of

agricultural production without the use of syn-

thetic inputs and without allowing the use of

transgenic organisms.

Organic compound Compound containing

carbon chains or rings and hydrogen with or

without oxygen, nitrogen and other elements;

foundation of modern polymer chemistry. See also:

Inorganic compound; Volatile organic compound

Organic cyanides Toxic chemicals. Any chemi-

cal compound containing the combining group

CN. Cyanide is highly toxic and fast-acting: it

inhibits cells’ oxidative processes. Cyanides

occur naturally in certain seeds, such as apple

168 On-peak energy

seeds and wild cherry pits. Cyanides, including

hydrogen cyanide (HCN or hydrocyanic acid),

are used industrially in the production of acrylic

ﬁbers, synthetic rubbers, and plastics as well as

in electroplating, case-hardening of iron and

steel, fumigation, and concentration of ores. See

also:

Toxic chemicals

Organic waste Materials that decompose

naturally.

Organically grown Agricultural crops grown

without the use of synthetic fertilizers or pesticides.

Organism Anything that is living, from bacteria

to plants to animals.

Orientation Orientation of a surface in degrees

away from solar south, towards either east or

west. Solar or true south is distinct from magnetic

south.

Oriented-strand board (OSB) An engineered,

reconstituted mat-formed building material panel

made of strands, ﬂakes, or wafers sliced from

small-diameter, round wood logs and bonded

with an exterior-type binder under heat and pres-

sure. Exterior or surface layers are composed of

strands aligned in the long panel direction;

inner layers consist of cross-aligned or randomly

aligned strands.

Osmotroph Organism that obtains nutrients

through its cell membrane. Examples are fungi

and bacteria, which can’t use particulate matter

as nutrients. See also:

Phagotroph

OTEC See: Ocean thermal energy conversion

Outage A discontinuance of electric power

supply.

Outfall Site where efﬂuent is discharged into

receiving waters.

Outgassing The process by which materials

expel or release gases.

Overhang Building element that shades win-

dows, walls, and doors from direct solar radiation

and protects these elements from precipitation.

Overload To exceed the design capacity of a

device.

Ovonic This word, invented by Standford

Ovshinsky, is composed of OVshinsky and

electrONIC. Refers to amorphous glassy semi-

conductors (germanium, tellurium, arsenic) that

change reversibly from an electrically noncon-

ducting state to a conducting state under applica-

tion of an electric ﬁeld of the order of 10.5 V/cm.

Oxidant Also known as an oxidizer agent.

Chemical, such as oxygen, that consumes electrons

in an electrochemical reaction.

Oxidation 1. Mixture of a substance with

oxygen; rust or burning may result.

2. Process in which electrons are removed

from atoms or ions.

Oxidation pond Human-made body of water in

which waste is consumed by bacteria. Used most

frequently with other waste-treatment processes.

Could be a sewage lagoon.

Oxidize 1. Chemically transform a substance

by combining it with oxygen.

2. Remove electrons from atoms or ions.

Oxidizer agent See:

Oxidant

Oxygen cycle Circulation of oxygen through

environmental compartments. It is closely linked

to the carbon cycle.

Oxygenated fuel (oxyfuel) Special type of

gasoline that burns more completely than

Oxygenated fuel (oxyfuel) 169

regular gasoline in cold-start conditions. It pro-

duces reduced carbon dioxide compared with

regular gas.

Oxygenate To treat, combine, or infuse with

oxygen.

Oxygenates Substances which, when added

to gasoline, increase the amount of oxygen in

the gasoline blend. Ethanol, methyl tertiary

butyl ether (MTBE), ethyl tertiary butyl ether

(ETBE), and methanol are common oxygenates.

Additives to gasoline reduce its carbon dioxide

emissions.

Ozone (O

) A major air pollutant, ozone gas is

a triatomic form of oxygen. It is not usually

emitted directly into the air, but at ground level

it is created by a chemical reaction between

oxides of nitrogen (NO

) and volatile organic

compounds (VOC) in the presence of sunlight.

Ozone has the same chemical structure whe-

ther it occurs miles above the Earth or at ground

level. It is produced in two layers: the tropo-

sphere or ground-layer ozone, known as “bad”

ozone; and the stratosphere or upper ozone,

known as “good” ozone.

Ozone is a primary constituent of smog.

Motor vehicle exhaust and industrial emissions,

gasoline vapors, and chemical solvents, as well

as natural sources, emit NO

and VOC that help

form ozone. Sunlight and hot weather cause

ground-level ozone to form in harmful con-

centrations in the air. As a result, it is known as

a summertime air pollutant. Ozone occurs in

both urban and rural areas. It is considered a

signiﬁcant health risk, particularly for children

with asthma. It also damages crops, trees, and

other vegetation.

Ozone is produced naturally in the stratosphere.

“Good” ozone occurs naturally in the strato-

sphere approximately 10–30 miles (16–48 km)

above the Earth’s surface, and forms a layer that

protects life on Earth from the Sun’s harmful

ultraviolet (UV) rays. This natural shield has gradu-

ally been damaged or depleted by human-made

chemicals including chloroﬂuorocarbons (CFCs),

hydrochloroﬂuorocarbons (HCFCs), halons, methyl

bromide, carbon tetrachloride, and methyl chloro-

form, all known as ozone-depleting substances.

Even though there has been a reduction in

the use of many ozone-depleting substances,

their use in the past can still affect the protective

ozone layer. Research indicates that depletion

of the “good” ozone layer is being reduced

worldwide. Thinning of the protective ozone

layer can be observed using satellite measure-

ments, particularly over the polar regions.

Ozone depletion can cause increased amounts

of UV radiation to reach the Earth, which can

lead to more cases of skin cancer, cataracts, and

impaired immune systems. Measures are being

taken to reduce ozone emissions in the USA

through the Clean Air Act, and also in other

countries. See also:

Air pollutants; ozone-depleting

substance

Ozone-depleting substance (ODS) Family of

human-made compounds that have been shown

to deplete stratospheric ozone. ODS include

chloroﬂuorocarbons (CFCs), bromoﬂuorocarbons

(halons), methyl chloroform, carbon tetrachloride,

methyl bromide, and hydrochloroﬂuorocarbons

(HCFCs). Once released into the air, these ozone-

depleting substances degrade very slowly. They

can remain intact for years as they move through

the troposphere until they reach the stratosphere.

There they are broken down by the intensity of

the Sun’s ultraviolet rays and release chlorine

and bromine molecules, which destroy the “good”

ozone. Scientists estimate that one chlorine atom

can destroy 100,000 “good” ozone molecules.

See also:

Ozone

Ozone hole Thin place in the ozone layer in

the stratosphere. Thinning of the stratospheric

ozone has been linked to the destruction of stra-

tospheric ozone by chloroﬂuorocarbons (CFCs)

170 Oxygenate

and related chemicals. Reductions in ozone levels

will lead to higher levels of ultraviolet B (UVB)

reaching the Earth’s surface. The Sun’s output of

UVB does not change; rather, less ozone means

less protection, and hence more UVB reaches the

Earth. Studies have shown that in the Antarctic,

the amount of UVB measured at the surface can

double during the annual ozone hole. Another

study conﬁrmed the relationship between reduced

ozone and increased UVB levels in Canada

during the past several years.

Ozone layer The layer of ozone that begins

approximately 15 km (9.3 miles) above Earth

and thins to an almost negligible amount at

about 50 km (31 miles), and shields the Earth

from harmful ultraviolet radiation from the Sun.

The highest natural concentration of ozone

(approximately 10 parts per million by volume)

occurs in the stratosphere at approximately 25

km (15.5miles) above Earth. The stratospheric

ozone concentration changes throughout the

year as stratospheric circulation changes with

the seasons. Natural events such as volcanoes

and solar ﬂares can produce changes in ozone

concentration, but human-made changes are of

the greatest concern. The ozone layer protects

the Earth against most ultraviolet (UV) radiation

coming from the Sun. UVB is a type of ultra-

violet light from the Sun (and sunlamps) that

has several harmful effects, particularly in

damaging DNA. It is a cause of melanoma and

other types of skin cancer. Studies have found

adverse effects on plants, materials, and marine

organisms from excessive exposure to UV.

Solar UVB radiation has been found to cause

damage to early developmental stages of ﬁsh,

shrimp, crab, amphibians, and other animals.

The most severe effects are decreased repro-

ductive capacity and impaired larval develop-

ment. Even at current levels, solar UVB

radiation is a limiting factor, and small increases

in UVB exposure could result in signiﬁcant

reduction in the size of the population of ani-

mals that eat these smaller creatures. See also:

Stratosphere, Ultraviolet radiation

Ozone precursors Chemical compounds, such

as carbon monoxide, methane, nonmethane

hydrocarbons, and nitrogen oxides, which react

with the Sun’s radiation and other chemical

compounds to form ozone. See also:

Troposphere

Ozone precursors 171

Packaging Wrappers for products; wrappers

may be made of a variety of materials: plastic,

cardboard, paper, metal, glass, wood, and

ceramics.

Packed tower Also known as packer tower

scrubber. Air pollution control device. Con-

taminated air is circulated through a tower

containing materials that have a large surface

area. The contaminants are absorbed into a liquid

ﬂowing over the tower materials. The liquid falls

downward and the air is forced upward through

the tower. The vapors or particulates contained

in the air go up through the surface area. The

fumes come into contact with the surface and

take up the material releasing the air and

cleaning it. See also:

Absorption process; Scrubbers;

Ventury scrubber

Packed tower aeration Process to remove

organic contaminants from groundwater. Ground-

water ﬂows downward in a tower ﬁlled with

material over a large surface. Air is introduced at

the bottom of the tower and is forced upward past

the falling groundwater. Organic contaminants

are transferred from the water to the air.

Packer tower scrubber See:

Packed tower

PAFC See: Phosphoric acid fuel cell

Panemone A type of vertical-axis wind turbine.

It has a rotating axis positioned at 90° to the

direction of the wind, while the wind-catching

blades move parallel to the wind. By contrast,

the shaft of a horizontal-axis wind turbine points

into the wind while its blades move at right-angles

to the wind’s thrust. A panemone primarily uses

drag, whereas the blades of a horizontal-axis

wind turbine use lift. The panemone windmill

dates from ancient Persia, where it was used as

a power source to grind wheat. It is drag-type

wind machine that can react to wind from any

direction.

Paper Product made from tree pulp in a process

that produces acid rain and dioxin.

Parabolic aluminized reﬂector lamp A type of

lamp with a lens of heavy, durable glass that

focuses the light. They have longer lifetimes

with less lumen depreciation than standard

incandescent lamps.

Parabolic dish solar collector A solar energy

conversion device that has a bowl-shaped dish

covered with a highly reﬂective surface that

tracks the Sun and concentrates sunlight on a

ﬁxed absorber, thereby achieving high tempera-

tures: for process heating, or to operate a heat

(Stirling) engine to produce power or electricity.

See also:

Stirling engine

Parabolic trough A type of solar thermal col-

lector. A solar energy conversion device that

uses a trough covered with a highly reﬂective

surface of either coated silver or polished alu-

minum to focus sunlight onto a linear absorber,

usually a Dewar tube, containing a working

ﬂuid that absorbs the concentrated sunlight. The

heat-transfer ﬂuid, usually oil, is used to heat

steam in a standard turbine generator. Estimates

of its economic and thermal efﬁciency range

from 60 to 80%. See also:

Solar thermal electric

systems

At present, all parabolic troughs are hybrids.

They include a fossil fuel system to supplement

the solar energy at night or when it is cloudy.

The fossil fuel is usually natural gas.

Parasitism Form of symbiosis in which one

species beneﬁts and the other is harmed. See

also:

Amensalism; Commensalism; Mutualism;

Symbiosis

Partial zero-emission vehicle (PZEV)

Designation by the California Air Resources Board

for a vehicle that has zero evaporative emissions

from its fuel system, has a 15 year (or at least

150,000 mile) warranty, and meets super-ultra-

low-emission vehicle (SULEV) tailpipe emissions

standards. A PZEV falls into the SULEV category.

See also:

Emissions standards, designations

Particulate matter Also known as particle

pollution or PM. Common air pollutant, toxic

chemical, and health threat. A complex mix-

ture of extremely small particles and liquid

droplets. Particle pollution is made up of a

number of components, including acids (such

as nitrates and sulfates), organic chemicals,

metals, and soil or dust particles. Particulate

pollution can cause health problems, especially

Figure 49 A parabolic trough collector

Source: US Department of Energy

Figure 48 A panemone—wind-catching panels turn edge-on to the wind when moving against the wind’s

thrust and side-on when moving downwind

Particulate matter 173

to the respiratory system. See also: Air pollutants;

Toxic chemicals

Particulates Small particles that are suspended

in air, such as soot, ash, dust, or other air emissions.

See also:

Air emissions

Partitioned matrix (LP) Developed by ecode-

signers to depict the interactions between a

designed system and the environment. Using 1

for the designed system, 2 for the environment,

and L for the interdependencies within a given

framework, the matrix is:

= processes that occur within the system

(internal interdependencies); L

= activities in

the environment (external interdependencies);

and L

= system/environment and environment

system exchanges.

Passive cooling systems Various simple cool-

ing techniques designed to lower indoor tem-

perature through the use of natural energy

sources. Design considerations include layout

of building, orientation, number, size, location,

and details of windows, shading devices, ther-

mal resistance, and heat capacity of the build-

ing envelope. The designs involve minimizing

heat gain by the building, minimizing solar

heat build-up of the building envelope and

solar penetration through windows, and provid-

ing natural ventilation. Minimizing heat gain

has not traditionally been regarded as a cooling

technology. Passive cooling systems typically

involve deep sky cooling or other cooling with-

out using motors to move a ﬂuid to transport the

heat (or cool) liquids. See also:

Passive solar

cooling

Passive daylight device Nonmechanical device

used to project daylight into the interior of a

structure. See also:

Light pipe; Light shelf; Tubular

skylight

Passive diffuser Air supply outlet, without a

fan, that relies on pressurized plenum or duct

air to deliver air into the conditioned space of a

building.

Passive mode design Also known as bioclimatic

design. An ecodesign strategy that speciﬁes low-

energy consumption systems by taking advan-

tage of the ambient climate of the locality. Pas-

sive mode ecodesign emphasizes three main

design considerations: i) low-energy design; ii)

the climate of the locality and the site ’s natural

features; iii) the appropriate shape of a building

and its ratio of volume to surface. In design

terms, passive mode design strategies include

appropriate built form conﬁguration and orien-

tation, internal spatial disposition, façade design,

such as solid to glass ratio, insulation, and color,

use of building mass, use of vegetation, natural

ventilation, and even color. Passive mode

design as low-energy design seeks to maximize

natural and ambient energy sources and mini-

mize the use of nonrenewable energy resources.

This can be achieved through the use of radia-

tion, conduction, and convection instead of

electromechanical heating and cooling systems

that require external sources of energy.

The climate and locality and the site’s natural

features inﬂuence the kind of design for the

built form, but do not determine the design. The

design is a response to the prevailing climate

and seasons over the year. Designs for tempe-

rate and cold climates are necessarily different,

for example, just as the speciﬁc site’s topo-

graphy and neighbors inﬂuence the design. The

appropriate shaping of the building and its

orientation are determined by the locality’s Sun

path, use of natural ventilation, use of vegeta-

tion, appropriate façade design, and Sun shad-

ing and other similar considerations. Passive

mode design relates to the climatic conditions

174 Particulates

of the locality and results in built forms that are

more adapted to a speciﬁc region.

Passive solar cooling Use of natural ventila-

tion is a primary strategy for cooling buildings

without mechanical assistance in hot humid

climates. Methods to increase the effectiveness

of natural ventilation include the following:

 operable windows—should be placed on the

south exposure

 wing walls—vertical solid panels placed

alongside windows perpendicular to the wall

on the windward side of the house

 thermal chimneys

 sunrooms.

Sunrooms can be designed to perform this func-

tion by venting at the top any excessive heat

generated in a south-facing sunroom during

the summer. With the connecting lower vents to

the living space open along with windows on the

north side, air is drawn through the living space

to be exhausted through the sunroom upper

vents. (The upper vents from the sunroom to the

living space and any side operable windows

must be closed and the thermal mass wall in the

sunroom must be shaded.) Thermal mass indirect

gain walls can be made to function similarly,

except that the mass wall should be insulated

on the inside when performing this function.

Thermal chimneys can be constructed in a narrow

conﬁguration (like a chimney) with an easily

heated black metal absorber on the inside behind

a glazed front that can reach high temperatures

and be insulated from the house. The chimney

must terminate above the roof level. A rotating

metal scoop at the top, which opens opposite

the wind, will allow heated air to exhaust with-

out being overcome by the prevailing wind.

Thermal chimney effects can be integrated into

houses with open stairwells and atria.

Other ventilation strategies include making

the outlet openings slightly larger than the inlet

openings; and placing inlets at low-to-medium

heights to provide airﬂow at occupant levels in

the room. Inlets close to a wall result in air

“washing” along the wall; it is important to have

centrally located inlets for air movement in the

center areas of the room. Window insect

screens decrease the velocity of slow breezes

more than stronger breezes (60% decrease at

1.5 mph (2.4 km/ph), 28% decrease at 6 mph

(9.6 km/ph)). Screening a porch will not reduce

air speeds as much as screening the windows.

Night ventilation of a home should be done at a

Figure 50b Passive solar cooling

Figure 50a Passive solar cooling

Passive solar cooling 175

Figure 50d Passive solar cooling

Figure 50c Passive solar cooling

176 Passive solar cooling

ventilation rate of 30 air changes per hour or

greater. Mechanical ventilation will be required

to achieve this. High-mass houses can be cooled

with night ventilation provided fabric furnish-

ings are minimized in the house. Keep a high-

mass house closed during the day and opened at

night. See also:

Passive cooling systems; Thermal

chimney; Wing wall

Passive solar design Design that uses the Sun’s

energy for heating and cooling of living spaces.

In this approach, the building itself or some

element of it takes advantage of natural energy

characteristics in materials and air created by

exposure to the Sun to heat and cool the building

without use of mechanical equipment. Passive

systems are simple, have few moving parts, and

require no mechanical systems and minimal

maintenance.

Principal design elements include proper

building orientation, window sizing, placement

and design of window overhangs to reduce

summer heat gain and ensure winter heat gain,

and proper sizing of thermal energy storage mass

such as a Trombe wall or masonry tiles. The

heat is distributed primarily by natural convec-

tion and radiation, although fans can also be used

to circulate room air or ensure proper ventila-

tion. Operable windows, thermal mass, thermal

chimneys, and wing walls are common elements

found in passive design. Wing walls are vertical

exterior wall partitions placed perpendicular to

adjoining windows to enhance ventilation through

windows. See also:

Thermal chimney; Thermal

mass; Trombe wall; Wing wall

Passive solar energy system General term

used to designate solar heating or cooling that

uses natural energy ﬂows to transfer heat.

Passive solar heater A solar water or space-

heating system in which solar energy is collected,

and/or moved by natural convection without

using pumps or fans. Passive systems are usually

integral collector/storage or batch collectors, or

thermosiphon systems. These systems do not use

controls, pumps, sensors, or other mechanical

parts, so little or no maintenance is required

over the lifetime of the system. See also:

Batch

heater; Thermosiphon

Figure 50e Passive solar cooling

Passive solar heater 177

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