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

Подождите немного. Документ загружается.

Passive solar heating Requires two primary

elements: south facing glass, and thermal mass

to absorb, store, and distribute heat. There are

three approaches to passive systems: i) direct

gain; ii) indirect gain; iii) isolated gain. The goal

of all passive solar heating systems is to capture

the Sun’s heat within the building’s elements

and release that heat during periods when the

Sun is not shining. At the same time as the

building’s elements (or materials) are absorbing

heat for later use, solar heat is available for keep-

ing the space comfortable but not overheated.

In this system, the actual living space is a solar

collector, heat absorber, and distribution system.

South-facing glass admits solar energy into the

house, where it strikes thermal mass materials in

the house such as masonry ﬂoors and walls. The

direct gain system will utilize 60—75% of the

Sun’s energy striking the windows.

In a direct gain system, the thermal mass ﬂoors

and walls are functional parts of the house. It is

also possible to use water containers inside the

house to store heat. However, it is more difﬁcult

to integrate water storage containers in the design

of a house. The thermal mass will temper the

intensity of the heat during the day by absorbing

the heat. At night, the thermal mass radiates heat

into the living space. See also:

Direct solar gain;

Indirect solar gain system; Isolated gain

Passive system Uses nonmechanical means

to satisfy space loads. Passive system design is

part of the ecodesign process and is carried out

according to the local environment and pre-

vailing biota. Passive systems do not rely on

electromechanical systems for energy. An exam-

ple is a passive solar system. See also:

Active

system; Solar energy

Passive treatment walls Technology in which

a chemical reaction takes place when con-

taminated groundwater comes into contact with

a barrier such as limestone or a wall containing

iron ﬁlings.

Figure 51 Basic passive solardesign principles (temperate zone)

178 Passive solar heating

Pathogens Disease-causing microorganisms.

Pathogens can cause diseases in humans, plants,

and animals.

Pay as you throw System in which residents pay

for municipal waste management by weight and

volume collected, rather than by a ﬁxed fee.

PBTs See:

Persistent bioaccumulatic toxic pol-

lutants

PCBs See: Polychlorinated biphenyls

PCE See: Perchloroethylene

PCFC See: Protonic ceramic fuel cell

Peak oil Also known as “end of oil”. Refers to

the point in time when the maximum rate of

global petroleum extraction is reached, after

which the rate of production enters terminal

decline. The concept is based on the observed

production rates of individual oil wells and the

combined production rate of a ﬁeld of related

oil wells. The aggregate production rate from an

oil ﬁeld over time appears to grow exponen-

tially until the rate peaks, and then declines

until the ﬁeld is depleted. It has been shown to

be applicable to the sum of a nation’s domestic

production rate, and is similarly applied to the

global rate of petroleum production. Peak oil is

not about running out of oil, but concerns the

peaking and subsequent decline of the production

rate of oil.

Peak power current (Electrical) Amperes pro-

duced by a photovoltaic module or array oper-

ating at the voltage of the current–voltage (I–V)

curve that will produce maximum power from

the module.

PECs See:

Photoelectrochemical cells

Pellet stove A space-heating device that burns

compressed wood or biomass pellets, usually

used in homes. It is more efﬁcient, cleaner-burning,

and easier to operate than conventional cord

wood-burning appliances. Most pellet stoves are

cast iron with stainless steel to encase circuitry

and exhaust areas.

Peltier effect Conversion of heat from the

ﬂow of an electric current, often implemented

as a thermoelectric cooler. When two dissim-

ilar metals or semiconductors form a junction

Figure 52b Passive solar heating: radiates the heat

at night

Figure 52a Passive solar heating: thermal mass in

the interior absorbs the sunlight in the

daytime

Peltier effect 179

with a current ﬂowing through the circuit, heat

moves from one side of the junction to the

other. The thermoelectric cooler construction

uses heavily doped p-type and n-type semi-

conductors to transfer heat from the cooled sur-

face to a hot surface. See also:

Seebeck effect;

Thomson effect

Pelton turbine Also known as a free-jet turbine.

Invented in 1880 by L. A. Pelton. A type of

impulse hydropower turbine in which water

passes through nozzles and strikes cups arranged

on the periphery of a runner, or wheel, which

causes the runner to rotate, producing mechanical

energy. The runner is ﬁxed on a shaft, and the

rotational motion of the turbine is transmitted

by the shaft to a generator.

Generally used for high-head, low-ﬂow appli-

cations. Used in storage power stations with

downward gradients up to 2000 meters (6,561

ft) and can contain up to six nozzles. See also:

Water turbine

PEM See: Proton exchange membrane fuel cell

Perched water Zone of unpressurized water held

above the water table by impermeable rock or

sediment.

Perchloroethylene (perc, PCE) Also known as

tetrachloroethylene or tetrachloroethene. Soil

contaminant. Cl

C = CCl

is a manufactured

chemical used in dry cleaning and degreasing.

It is regulated by the US Safe Drinking Water

Act of 1974, which determines safe levels of

chemicals in drinking water. Ingestion may

increase risks of cancer and liver damage. See

also:

Soil contaminants; Toxic chemicals

Percolation 1. Movement of water downward

and radially through subsurface soil layers,

usually continuing downward to groundwater. It

can also involve upward movement of water.

2. Slow seepage of water through a ﬁlter.

Perﬂuorocarbons (PFCs) Group of human-

made chemicals composed of carbon and ﬂuor-

ine only. These chemicals, predominantly CF

and C

, were introduced as alternatives, along

with hydroﬂuocarbons, to ozone-depleting sub-

stances. PFCs are emitted as by-products of

industrial processes and are also used in manu-

facturing. PFCs do not harm the stratospheric

ozone layer, but they are powerful greenhouse

gases: CF

and C

have global warming

effects.

Perimeter zone Area adjacent to and within

about 15 feet (5 meters) of an exterior wall.

These spaces have heating and cooling loads

that are signiﬁcantly different from internal/core

zone areas because of factors such solar gain

and heat loss through the building envelope.

Peripheral service core Placement of the service

core along the periphery of a building. Its features

include no need for ﬁre protection pressurization

Figure 53 The diagram from Pelton’s original

patent (October 1880)

180 Pelton turbine

ducts, provision of natural ventilation to the ele-

vators, provision of natural sunlight to the ele-

vator and stair lobbies, and more natural light in

the building in the event of power failure.

Perlite Chemically inert natural volcanic mate-

rial; used as insulation either in loose form or as

an aggregate in concrete.

Permaculture From “permanent agriculture”.

Represents a whole-systems approach to agri-

culture through the conscious design and main-

tenance of agriculturally productive ecosystems

that have the diversity, stability, and resilience

of natural ecosystems. The design assembles

conceptual, material, and strategic components

in a biological pattern that focuses on beneﬁting

all life forms.

Permeable Materials that can be penetrated or

passed through, usually by liquids.

Persistent bioaccumulatic toxic pollutants

(PBTs) Chemicals that are toxic, persist in the

environment and bioaccumulate in food chains,

and pose risks to human health and ecosystems.

The biggest concerns about PBTs are that they

transfer easily among air, water, and land, and

span boundaries of programs, geography, and

generations.

Persistent organic pollutants (POPs) Toxic

chemicals that adversely affect human health

and the environment around the world. Because

they can be transported by wind and water,

most POPs generated in one country can affect

people and wildlife far from where they are

used and released. They persist for long periods

in the environment, and can accumulate and

pass from one species to the next through the

food chain. They include organochlorine pesti-

cides, polycholorinated biphenyls, dioxins, and

furans. See also:

Stockholm Convention on Persistent

Organic Pollution

Pervious materials Materials that permit water

to pass through with little restriction because of

their porous nature or large spaces in the material.

Examples include gravel, crushed stone, open

paving blocks, or pervious paving blocks, which

are used for driveways, parking areas, walkways,

and patios. Their use reduces runoff from those

areas, as well as increasing inﬁltration.

Pesticides Any substance or mixture of sub-

stances intended to prevent, destroy, repel, or

mitigate any pests. Pests can be insects, mice,

other animals, unwanted plants, fungi, or micro-

organisms. Applies to herbicides, fungicides, and

other substances used to control pests. In the

USA, a pesticide is also any substance used as a

plant regulator, defoliant, or desiccant.

PET See:

Polyethylene terephthalate

Petrochemical Also known as petroleum che-

mical. Chemical made from petroleum or nat-

ural gas feedstock, such as ethylene, butadiene,

most major plastics, and resins.

Petroleum A nonrenewable fossil fuel, petro-

leum means “rock oil” or “oil from the earth”.

Hydrocarbon mixtures, including crude oil,

lease condensate, natural gas, products of nat-

ural gas processing plants, reﬁned products,

semiﬁnished products, and blending materials.

The ﬁ ve countries producing the most crude

oil are Saudi Arabia, Russia, USA, Iran, and

China. Because modern society uses so many

petroleum-based products—including gasoline,

kerosene, fuel oil, mineral oil, and asphalt—

contamination of the environment is potentially

widespread. They are released to the environ-

ment through accidents, as releases from indus-

tries, or as by-products from commercial or

private uses. When released directly to water

through spills or leaks, certain petroleum frac-

tions will ﬂoat in water, whereas others will

accumulate in the sediment at the bottom of the

Petroleum 181

Openmirrors.com

water, affecting bottom-feeding ﬁsh and organ-

isms. When released to the soil, petroleum

compound emissions move through the soil to

the groundwater. Depending on the compound,

some emissions will evaporate, others will dis-

solve in the water, and still others will remain

for a long time. Exposure to petroleum com-

pounds can also affect human health adversely.

The effects will depend on the toxicity of the

compounds, and can range from respiratory

problems to death.

PFCs See:

Perﬂuorocarbons

pH Scale denoting the level of acidity in a

substance. Water, for example, is neutral with a

pH of 7. pH values from 0 to 7 indicate acidity;

values from 7 to 14 indicate alkalinity.

Phagotroph Organism that obtains nutrients

through ingestion of organic matter or other organ-

isms. This class of organism includes all animals,

from single-celled amoeba to larger animals.

See also:

Formaldehyde; Urea formaldehyde

Phenotype Visible and/or measurable char-

acteristics of an organism. As ecobalances

change, organisms may mutate.

Phosphoric acid fuel cell (PAFC) One type of

fuel cell. PAFC, developed in the 1980s, has the

most mature fuel cell technology in terms of

system development and commercialization activ-

ities. The phosphoric acid fuel cell uses liquid

phosphoric acid (H

) as the electrolyte. The

phosphoric acid is contained in a Teﬂon-bonded

silicone carbide matrix. The small pore structure

of this matrix preferentially keeps the acid in

place through capillary action. Some acid may

be entrained in the fuel or oxidant streams, and

addition of acid may be required after many

hours of operation. Platinum-catalyzed, porous

carbon electrodes are used on both the fuel

(anode) and oxidant (cathode) sides of the elec-

trolyte. PAFC power plant designs show elec-

trical efﬁciencies in the range 36–42% (HHV2).

The higher-efﬁciency designs operate with pres-

surized reactants, require more components,

Figure 54 pH levels of some common substances

182 PFCs

and could have a higher cost. A portion of the

thermal energy can be supplied at temperatures

of approximately 250–300 °F (121–149 °C);

however, the majority of the thermal energy is

supplied at about 150 °F (65 °C). A PAFC has a

power density of 160–175 W/ft

(929 cm

)of

active cell area.

PAFCs are less powerful than other fuel cells,

given the same weight and volume. As a result,

they are usually large and heavy, and expensive

as they use platinum catalysts. In 2007, it was

estimated that a typical PAFC costs between US

$4000 and US$4500 per kilowatt to operate.

They are 85% efﬁcient when used for cogen-

eration of electricity and heat, but less efﬁcient

at generating electricity alone (37–42%). This is

only slightly more efﬁcient than combustion-

based power plants. If the source of hydrogen

fuel is reformed gasoline, sulfur must be removed

from the fuel entering the PACF cell, or it will

damage the electrode catalyst. See also:

Fuel cells

Phosphorus (P) Chemical element used as a

dopant in making n-type semiconductor layers.

Photochemical cycle Also known as the pho-

tolytic cycle. A series of chemical reactions that

result in accumulation of ozone or other oxi-

dants in the troposphere. The cycle includes the

absorption of sunlight by NO

, causing conver-

sion of the dioxide into NO and O (atomic

oxygen). The atomic oxygen combines with O

to form ozone (O

Photochemical modeling Computer modeling

of reactions in the atmosphere that produce

ozone from nitrogen oxides and volatile

organic compounds. It can be used to evaluate

the air quality impacts of heat island reduction

strategies.

Photochemical oxidants The products of

reactions between NO

and a wide variety of

volatile organic compounds. The best known

oxidants are ozone (O

), peroxyacetyle nitrate

and hydrogen peroxide (H

). The main

impact on the natural environment is caused by

elevated ozone. Excessive concentrations of

tropospheric ozone have toxic effects on both

plants and human health.

Photodecomposition See:

Photolysis

Photodissociation See: Photolysis

Photoelectric effect See: Appendix 4: Photo-

voltaics

Photoelectrochemical cells (PECs) 1. Gen-

eric name for solar cells that extract electrical

energy from light, including visible light. Each

cell consists of a semiconducting photoanode

and a metal cathode immersed in an electrolyte.

Some PECs simply produce electrical energy;

others produce hydrogen in a process similar to

the electrolysis of water.

2. Type of photovoltaic device in which the

electricity induced in the cell is used immedi-

ately within the cell to produce a chemical,

such as hydrogen, which can then be withdrawn

for use.

Photolysis Also known as photodissociation

or photodecomposition. Photolysis is the pro-

cess of chemical decomposition of a substance

or material when it is subjected to light. Light

includes both visible light and ultraviolet radiation.

1. The formation of the ozone layer in the

stratosphere is the result of photolysis. Ozone in

the stratosphere is created by ultraviolet light

striking oxygen molecules containing two oxygen

atoms (O

), splitting them into individual oxygen

atoms (atomic oxygen). The atomic oxygen

then combines with the unbroken O

to create

ozone (O

). This ozone is known as “good”

ozone because it serves as a ﬁlter of the middle

and far ultraviolet radiation. Photolysis is also

the process by which toxic chloroﬂuorocarbons

Photolysis 183

(CFCs) are broken down in the upper atmo-

sphere to form ozone-destroying chlorine free

radicals.

2. Photolysis can degrade air pollutants and

contaminants in the water and on the land. Two

toxic pesticides that are decomposed through

photolysis are chlorophenol and diazinon.

3. Photolysis is an important component of the

light-dependent phase of photosynthesis. It uses

light energy (sunlight) to break water molecules

or some other electron donor, to obtain elec-

trons for photosynthesis. The function of these

electrons is to replace electrons lost by the photo-

systems to the electron transport systems. Water

serves as a substrate for photolysis, resulting in

the generation of free oxygen (O

). Water (H

serves as a substrate for photolysis, resulting in

the generation of free oxygen (O

). Photolysis of

water occurs in the thylakoids of cyanobacteria

and the chloroplasts of green algae and plants.

The effectiveness of photons of different

wavelengths depends on the absorption spectra

of the photosynthetic pigments in the organism.

Chlorophylls absorb light in the violet–blue and

red parts of the spectrum, while accessory pig-

ments capture other wavelengths as well. The

phycobilins of red algae absorb blue-green light,

which penetrates more deeply into water than

red light, enabling them to photosynthesize in

deep waters. Each absorbed photon causes the

formation of an exciton (an electron excited to a

higher energy state) in the pigment molecule.

The energy of the exciton is transferred to a

chlorophyll molecule (P

680

, where P stands for

pigment and 680 for its absorption maximum at

680 nm) in the reaction center of photosystem II

via resonance energy transfer. P

680

can also

directly absorb a photon at a suitable wave-

length. Photolysis during photosynthesis occurs

in a series of light-driven oxidation events. The

energized electron (exciton) of P

680

is captured

by a primary electron acceptor of the photo-

synthetic electron transfer chain and thus exits

photosystem II. In order to repeat the reaction,

the electron in the reaction center needs to be

replenished. This occurs by oxidation of water

in the case of oxygenic photosynthesis. The

electron-deﬁcient reaction center of photosystem

II (P

680

*) is the strongest biological oxidizing

agent known on Earth, which allows it to break

apart molecules as stable as water.

Photolytic cycle See:

Photochemical cycle

Photon Under the photon theory of light, a

photon is a discrete bundle (or quantum) of

electromagnetic (or light) energy. Photons are

always in motion and, in a vacuum, have a

constant speed of light to all observers, at the

vacuum speed of light (more commonly just

called the speed of light) of c = 2.998  10

m/s.

Photoperiod response Relates plant and tree

response to frequencies and intensities of light

that regulate the development and ﬂowering of

plants and trees.

Photosynthesis The process of acquiring and

using light energy to produce food. It provides

the energy and reduced carbon essential for the

survival of almost all life on Earth. It also pro-

vides molecular oxygen needed by oxygen-

consuming organisms. Plants take in CO

from

the air or from bicarbonate in water to build

carbohydrates, releasing O

in the process. The

key initial step in the growth of biomass, its

equation is: CO

O + light + chlorophyll

! (CH

O) + O

. The various pathways of pho-

tosynthesis produce different responses to atmo-

spheric CO

concentrations. Photosynthesis is the

basis for food production in plants, algae, and

certain bacteria, and thus the beginning of the

food chain. See also:

Artiﬁcial photosynthesis;

Food chain; Sun

Photovoltaic (PV) Pertaining to the direct

conversion of light into electricity. See:

Appendix

4: Photovoltaics

184 Photolytic cycle

Photovoltaic (PV) array A linked collection of

PV modules, which in turn are made of inter-

connected solar cells. The cells convert solar

energy into direct current (DC) electricity via the

PV effect. The power that one module can pro-

duce is usually not sufﬁcient to meet require-

ments of a home or a business, so the modules

are linked together to form an array. Most PV

arrays use an inverter to convert the DC power

produced by the modules into alternating cur-

rent (AC) that can plug into the existing infra-

structure to power lights, motors, and other loads.

The modules in a PV array are usually ﬁrst

connected in series to obtain the desired vol-

tage; the individual strings are then connected

in parallel to allow the system to produce more

current. Solar arrays are typically measured by

the electrical power they produce in watts,

kilowatts, or megawatts. Interconnected systems

of PV modules function as a single electricity-

producing unit. The modules are assembled as a

discrete structure, with common support or

mounting. In smaller systems, an array can con-

sist of a single module. Individual PV modules

can be connected in series, in parallel, or both,

to increase either output voltage or current. This

also increases the output power. See:

Appendix

4: Photovoltaics; Photovoltaic module

Photovoltaic automobile Automobile that is

Solar

electric-powered vehicle

Photovoltaic cell Treated semiconductor mate-

rial that converts solar irradiance to electricity.

Also known as a solar cell, as it converts sun-

light directly into electricity. Smallest semi-

conductor element within a photovoltaic (PV)

module to perform the immediate conversion of

light into electrical energy. PV is a specialized

form of semiconductor anode that converts

visible light, or infrared or ultraviolet radiation,

directly into electricity. The conversion process

is based on the photoelectric effect discovered

by Alexander Bequerel in 1839. The photo-

electric effect describes the release of positive

and negative charge carriers in a solid state

when light strikes its surface.

Solar cells are composed of various semi-

conducting materials, about 95% of which are

made of silicon. One side of the semiconductor

material has a positive charge; the other side is

negatively charged. Sunlight hitting the positive

side will activate the electrons on the negative

side and produce an electrical current.

There are three types of PV cell: mono-

crystalline, polycrystalline, and amorphous. i)

Monocrystalline rods are extracted from melted

silicon and then sawn into thin plates. This

production process guarantees a relatively

high level of efﬁciency. ii) Polycrystalline cells

are more cost-efﬁcient to produce, but less efﬁ-

cient than the monocrystalline cell. iii) Amor-

phous or thin-layer cells form a silicon ﬁlm

which adheres to glass or another material. This

is the least expensive and least efﬁcient of the

three types of cell. Because of this, they are pri-

marily used in low-power equipment (watches,

pocket calculators) or as façade elements.

Their efﬁciency is half that of crystalline cells,

and they degrade with use. See:

Appendix 4:

Photovoltaics

Photovoltaic device Solid-state electrical device

that converts light directly into direct current

electricity. The electricity produced has voltage-

current characteristics that are determined by

the light source, and the materials and design of

the device. Solar PV devices are made of var-

ious semiconductor materials, including silicon,

cadmium, sulﬁde, cadmium telluride, and gal-

lium arsenide; and may be in single crystalline,

multicrystalline, or amorphous form. The struc-

ture of a PV device depends on the limitations of

the material used in the PV cells. There are four

basic device designs: i) homojunction, ii) het-

erojunction, iii) p-i-n/n-i-p, and iv) multijunction.

See:

Appendix 4: Photovoltaics

Photovoltaic device 185

Photovoltaic generator All PV strings of a PV

power supply system, which are electrically

connected. See:

Appendix 4: Photovoltaics

Photovoltaic module Single solar cells are

interconnected to form larger units to generate

electricity for different uses. Cells connected in

series have a higher voltage, while those con-

nected in parallel produce more electric cur-

rent. The interconnected solar cells are usually

embedded in transparent ethyl vinyl acetate,

ﬁtted with an aluminum or stainless steel frame

and covered with transparent glass on the front.

A junction box on the underside of the module

is used to allow for connecting the module

circuit conductors to external conductors.

Photovoltaic module tilt angle For proper

operation, PV modules must be oriented as clo-

sely as possible toward the equator. In the

northern hemisphere, the direction is true south:

in most areas this varies from the magnetic

south given by a compass. A simple connection

must be made. First, ﬁnd the magnetic variation

from the isogonic map. This is given in degrees

east or west from magnetic south.

The modules should be installed within 200°

of true south. In areas with morning fog, the

array can be oriented up to 200° toward the

west to compensate. Conversely, arrays in areas

with a high incidence of afternoon storms can

be oriented toward the east.

Table 4 Photovoltaic module tilt angles

When system most used Recommended tilt

angle

All year Latitude

Mostly winter Latitude +15°

Mostly summer Latitude -15°

Mostly autumn or spring Latitude

Figure 55 Isogonic map of the USA

186 Photovoltaic generator

If the array is located in the Southern Hemi-

sphere, the array must face true north. Small,

portable arrays are usually just pointed at the

Sun, and moved every hour or so to follow the Sun

across the sky. See:

Appendix 4: Photovoltaics

Photovoltaic productive mode system Use of

photovoltaic cells to convert sunlight directly

into electricity. See:

Appendix 4: Photovoltaics

Photovoltaic Roadmap Industry-led effort to

help countries guide their domestic PV research,

technology, manufacturing, applications and stan-

dards. The goal of the European Union’sPV

Roadmap is for the EU to be one of the top

three in the development of PV systems; to

achieve energy independence from fossil fuels;

and to multiply the use of PV by 30 times by

2010. Members of the EU share research results.

Other countries, including the USA, Japan, and

Australia, also have a PV Roadmap.

Photovoltaic system Complete set of compo-

nents for converting sunlight into electricity by

the photovoltaic (PV) process, including the array

and balance of system components. A complete PV

energy system is composed of three subsystems.

 On the power-generation side, a subsystem

of PV devices (cells, modules, arrays) converts

sunlight to direct-current (DC) electricity.

 On the power-use side, the subsystem consists

mainly of the load, which is the application

of the PV electricity.

 Between these two, a third subsystem enables

the PV-generated electricity to be properly

applied to the load. This third subsystem is

often called the balance of system (BOS).

Figure 57 shows the elements needed to get

the power created by a PV system to the load

(in this example, a house). The stand-alone PV

system (a) uses battery storage to provide

dependable DC electricity day and night. Even

for a home connected to the utility grid (b), PV

can produce electricity (converted to AC by a

power conditioner) during the day. The extra

electricity can then be sold to the utility during

the day, and the utility can in turn provide

electricity at night or during poor weather. See:

Appendix 4: Photovoltaics; Balance of system

Photovoltaic tracking array Photovoltaic (PV)

array that follows the path of the Sun to maximize

the solar radiation incident on the PV surface.

The ability to follow the Sun produces signiﬁcantly

greater amounts of energy when the Sun’s energy

is predominantly direct. Two common orienta-

tions are i) one-axis tracking, where the array

tracks the Sun east to west; and ii) two-axis

tracking, where the array points directly at the

Sun at all times. Tracking arrays use both direct

and diffuse sunlight. Two-axis tracking captures

the maximum possible daily energy from the

Sun. See:

Appendix 4: Photovoltaics

Phthalates Toxic chemicals. Also known as

phthalate esters. Group of chemical compounds

that are mainly added to plastics to increase

Figure 56 Directions on a compass at 20° east

magnetic variation

Phthalates 187