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

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(torque) by one of two methods: combustion; or

electrochemical conversion in a fuel cell. In

combustion, the hydrogen is burned in engines

using fundamentally the same method as tradi-

tional gasoline (petrol) cars. In fuel-cell conver-

sion, the hydrogen is reacted with oxygen to

produce water and electricity, the latter being

used to power an electric traction motor.

The hydrogen internal combustion car is a

modiﬁed version of the traditional gasoline internal

combustion engine car. These hydrogen engines

burn fuel in the same manner as gasoline

engines. The ﬁrst hydrogen internal combustion

engine was designed by François Isaac de Rivaz

in 1807.

Some car manufacturers, such as Daimler

Chrysler and General Motors, are investing in

the efﬁcient hydrogen fuel cells; others, such as

Mazda, have developed Wankel engines that

burn hydrogen.

While hydrogen fuel cells themselves are

potentially very energy efﬁcient, there are four

technical obstacles to the development and use

of a fuel cell-powered hydrogen car.

 Fuel cell cost—hydrogen fuel cells are currently

costly to produce, and are fragile. There is

ongoing development of inexpensive fuel

cells that are hardy enough to survive auto-

mobile vibrations. Also, many designs require

rare and costly substances such as platinum

as a catalyst in order to work properly. Such

a catalyst can also become contaminated by

impurities in the hydrogen supply. In the past

few years, however, a nickel–tin catalyst has

been under development, which may lower

the cost of cells.

 Temperature sensitivity—temperatures below

freezing (32 °F or 0 °C) are a major concern

with fuel-cell operations. Operational fuel cells

have an internal vaporous water environment

that could solidify if the fuel cell and con-

tents are not kept above freezing. Most fuel

cell designs are not yet robust enough to

survive in below-freezing environments. This

makes startup of the fuel cell a major con-

cern in cold weather operation. Places where

temperatures can reach –40 °C (–40 °F) at

startup would not be able to use early model

fuel cells. Ballard Power Systems has

announced that it has already hit the US

Department of Energy’s 2010 target for cold-

weather starting, which was 50% power

achieved in 30 seconds at –20 °C.

 Life span of the fuel cell—although service

life is coupled to cost, fuel cells have to be

compared with existing machines with a

service life in excess of 5000 hours for sta-

tionary and light duty. Marine proton-exchange

membrane (PEM) fuel cells reached the target

in 2004. Research is being carried out on

heavy-duty cells for use in buses. The goal is

to have a service life of 30,000 hours.

 Hydrogen production and environmental

concerns—the molecular hydrogen needed

as an on-board fuel for hydrogen vehicles can

be produced through many thermochemical

methods, using natural gas, coal (coal gasiﬁ-

cation), liqueﬁed petroleum gas, or biomass

(biomass gasi

ﬁcation);

by a process called

thermolysis;

or as a microbial waste product

called biohydrogen or biological hydrogen

production. Hydrogen can also be produced

from water by electrolysis, or by chemical

reduction using chemical hydrides or alumi-

num. Current technologies for manufacturing

hydrogen use energy in various forms, total-

ling between 25 and 50% of the higher

heating value of the hydrogen fuel, to pro-

duce, compress or liquefy, and transmit the

hydrogen by pipeline or truck. Electrolysis,

currently the most inefﬁcient method of pro-

ducing hydrogen, uses 65–112% of the higher

heating value on a well-to-tank basis.

Concerns about environmental effects of the

production of hydrogen from fossil energy resour-

ces include the emission of greenhouse gases, a

128 Hydrogen-powered vehicle

consequence that would also proceed from the

on-board re-forming of methanol into hydrogen.

Studies comparing the environmental con-

sequences of hydrogen production and use in

fuel-cell vehicles with the reﬁning of petroleum

and combustion in conventional automobile

engines have found a net reduction of ozone

and greenhouse gases in favor of hydrogen.

Hydrogen production using renewable energy

resources would not create such emissions or,

in the case of biomass, would create near-zero

net emissions.

In addition to the inherent losses of energy in

the conversion of feedstock to produce hydrogen,

which makes hydrogen less advantageous as an

energy carrier, there are economic and energy

penalties associated with packaging, distribution,

storage, and transfer of hydrogen.

Researchers in the area of artiﬁcial photo-

synthesis are trying to replicate the process of

splitting water into hydrogen and oxygen using

sunlight energy. If successful, this process could

provide a source of hydrogen as a clean, non-

polluting fuel. The attraction of hydrogen is that

it produces no pollution or greenhouse gases at

the tailpipe. Current methods of producing hydro-

gen from oil and coal produce substantial carbon

dioxide. Unless and until this carbon can be

captured and stored, renewable (wind or solar)

and nuclear power, with their attendant pro-

blems of supply and waste, are the only means

of producing hydrogen without also producing

greenhouse gases.

In addition, setting up a completely new

infrastructure to distribute hydrogen would cost

at least US$5,000 per vehicle. Transporting,

storing, and distributing a gaseous fuel, as

opposed to a liquid, raises many new problems.

It has been estimated that a substantial invest-

ment of many billion dollars will be needed to

develop hydrogen fuel cells that can match

the performance of today’s gasoline engines.

Researchers indicate that improvements to cur-

rent cars and current environmental rules are

more than 100 times cheaper than hydrogen

cars at reducing air pollution. And for several

decades, the most cost-effective method to

reduce oil imports and CO

emissions from cars

will be to increase fuel efﬁciency.

Buses, trains, PHB© bicycles, cargo bikes,

golf carts, motorcycles, wheelchairs, ships, air-

planes, submarines, high-speed cars, and rock-

ets already can run on hydrogen, in various

forms and sometimes at great expense. NASA

uses hydrogen to launch space shuttles. Some

airplane manufacturers are pursuing hydrogen

as fuel for airplanes. Unmanned hydrogen planes

have been tested, and in February 2008 Boeing

tested a manned ﬂight of a small aircraft pow-

ered by a hydrogen fuel cell. Boeing reported

that hydrogen fuel cells were unlikely to power

the engines of larger passenger jets, but could

be used as backup or auxiliary power units

onboard. Rockets use hydrogen because it gives

the highest exhaust velocity as well as providing a

lower net weight of propellant than other fuels.

It is very effective in upper stages, although it

has also been used on lower stages, usually in

conjunction with a dense fuel booster.

The main disadvantage of hydrogen in this

application is its low density and deeply cryogenic

nature, requiring insulation—this makes the

hydrogen tankage relatively heavy, which greatly

offsets many of the otherwise overwhelming

advantages for this application. See also:

Artiﬁcial

photosynthesis

Hydrogen-rich fuel Fuel that contains a sig-

niﬁcant amount of hydrogen, such as gasoline,

diesel fuel, methanol, ethanol, natural gas,

and coal.

Hydrological cycle Process of evaporation and

transport of vapor, condensation, precipitation,

and the ﬂow of water from continents to

oceans. It is a major factor in determining climate

through its inﬂuence on surface vegetation,

clouds, snow and ice, and soil moisture. The

Hydrological cycle 129

hydrological cycle is believed to be responsible

for 25–30% of the mid-latitudes’ heat transport

from the equatorial to polar regions.

Hydrology Science of water, its properties,

distribution, and circulation. Geology of ground-

water, with emphasis on the chemistry and

movement of water.

Hydronic heating system A type of heating

system in which water is heated in a boiler and

either moves by natural convection or is pumped

to heat exchangers or radiators in rooms; radiant

ﬂoor systems have a grid of tubing laid out in the

ﬂoor for distributing heat. The temperature in

each room is controlled by regulating the ﬂow

of hot water through the radiators or tubing.

Hydronic system System of heating or cooling

using forced circulation of liquids or vapors in

pipes.

Hydroponic Method of growing plants in a

nutrient-rich liquid medium rather than soil. It is

an important component of vertical farming. See

also:

Vertical farming

Hydropower See: Hydroelectric power plant

Hydrosphere All the water on Earth; includes

lakes, oceans, seas, glaciers, other liquid surfaces,

subterranean water, and clouds and water vapor.

Hydrothermal ﬂuids These ﬂuids can be either

water or steam trapped in fractured or porous

rocks; they are found from several hundred feet

to several miles below the Earth’s surface. Tem-

peratures vary from about 90 to 680 °F (32 to

360 °C), but roughly two-thirds range in tem-

perature from 150 to 250 °F (66 to 121 °C). The

latter are the easiest to access, and therefore the

only forms being used commercially.

Hypocaust Radiating heat into a room through

the ﬂoor; open space below a ﬂoor that is heated

by gases from a ﬁre or furnace below, which

allows the passage of hot air to heat the room

above. This type of heating was developed by

the Romans. See also:

Murocaust

Hypolimnion The bottom and densest layer of

a stratiﬁed lake. Usually the coldest layer in

summer and warmest in winter. Is isolated from

wind mixing, and too dark for much plant

photosynthesis to occur.

Hypoxia Condition in which the levels of

oxygen in water are too low to sustain most

animal life. It occurs when high concentrations

of nutrients enter the water. Nutrients used in

fertilizer, including nitrogen and phosphorus,

stimulate plant growth in water. The predominant

plants in water, algae, thrive on nitrogen and

phosphorus and consume huge quantities of

oxygen, depriving many aquatic organisms,

including ﬁsh, of the oxygen they need to sur-

vive. The result is massive ﬁsh kills and threats to

commercial ﬁsheries. Landscape changes through

the loss of coastal and freshwater wetlands can

also contribute to hypoxia.

130 Hydrology

IAEA See: International Atomic Energy Agency

IAQ See: Internal air quality

Ice stores Conservation technology that makes

use of off-peak refrigeration energy to charge an

ice store for release of cooling energy during

the day.

ICS Integral collector/storage system. See:

Batch

heater

Impact Environmentally, the effect on either

the environment or people of a speciﬁc action.

See also:

Environmental impact statement

Impervious surface Hard surface that either

prevents or retards the entry of water into the

soil, causing water to run off the surface in

greater quantities or at an increased rate of ﬂow.

Common impervious surfaces include rooftops,

walkways, patios, driveways, parking lots, sto-

rage areas, concrete or asphalt paving, and gravel

roads. High concentrations of impervious sur-

faces increase the probability of ﬂooding from

heavy rains and storms.

Impoundment Body of water conﬁned by a

dam, dike, ﬂoodgate, or other artiﬁcial barrier.

Impoundment power plant One of three types

of hydropower plant. The others are diversion

and pumped storage plants. See also:

Diversion

power plant; Hydroelectric power plant; Pumped

storage plant

Impulse turbine Turbine that is driven by high-

velocity jets of water or steam from a nozzle

directed to vanes or buckets attached to a wheel.

A Pelton turbine or Pelton wheel is an impulse

hydroturbine. See also:

Pelton turbine

Inbreeding depression Accumulation of harm-

ful genetic traits through mutations or natural

selection in a species that lowers the viability and

reproductive success of enough individual mem-

bers to affect the entire species. Pollutants in the

air, soil, and water can result in genetic mutations

and alter the ability of a species to survive.

Incident angle Angle between a ray of light

striking a surface (incident ray) and the normal

(line perpendicular) to that surface. For a mirror,

it is equal to the angle of reﬂection.

Incident light Light that shines on the face of a

solar cell or module.

Incident solar radiation The amount of solar

radiation striking a surface per unit of time and

area.

Incineration Process of burning at high tem-

perature. Properly operated incineration projects

can provide energy in the form of electricity or

processed steam, while reducing the volume of

landﬁll waste. Managed incineration also uses

processes that minimize emissions of airborne

particulate and smoke.

Solid waste incineration is widely used in

Denmark, France, Germany, Japan, Luxembourg,

the Netherlands, Sweden, and the USA. Incin-

eration can emit various levels of arsenic,

nickel, mercury, lead, and calcium, all of which

can be toxic even at low levels.

An alternative to incineration is anaerobic

decomposition, also known as anaerobic diges-

tion. See also:

Anaerobic decomposition; Solid

waste

Indicator species An organism, often a

microorganism or plant, that serves as a mea-

sure of the environmental conditions that exist

in a speciﬁc locality.

Indigenous Native to a speciﬁc geographical

area.

Indirect heat gain Result of interception and

storage of the Sun’s energy in proximal

storage before it enters a space. Solar masonry

walls and water wall collectors are examples

of indirect gain systems. Trombe walls are ther-

mal collectors that store the Sun’s heat during

the day and emit that heat through conduction

at night. See also:

Indirect solar gain system;

Trombe wall

Indirect solar gain system A passive solar

heating system in which the Sun warms a heat-

storage element, and the heat is distributed to

the interior space by convection, conduction,

and radiation.

Indirect solar water heater These systems

circulate ﬂuids, which can be different from

water (such as diluted antifreeze), through the

collector. The heat collected is used to heat the

household water supply using a heat exchanger.

Figure 38 Indirect solar water heater

132 Indicator species

Also known as closed-loop systems. An indirect

system that exhibits effectiveness, reliability, and

low maintenance is the drainback system, which

uses distilled water as the collector circulating

ﬂuid. See also:

Closed-loop active system; Drainback

system; Heat exchanger

Indoor air pollution Pollutants that adversely

affect internal air quality (IAQ). Pollutants and

sources include asbestos, biological pollutants,

carbon monoxide, formaldehyde, pressed wood

products, household cleaning and maintenance,

lead, nitrogen dioxide, pesticides, radon, respir-

able particles, secondhand smoke, tobacco smoke,

stoves, heaters, ﬁreplaces and chimneys. See also:

Internal air quality

Indoor air quality See: Internal air quality

Indoor environmental quality (IEQ) Quality of

the air and environment inside buildings, based

on pollutant concentrations and conditions that

can affect the health, comfort, and performance

of occupants—including temperature, relative

humidity, light, sound, odors, noise, static elec-

tricity, and other factors. Good IEQ is an essen-

tial component of any building, especially a

green building.

Induction generator A device that converts

the mechanical energy of rotation into elec-

tricity based on electromagnetic induction. An

electric voltage (electromotive force) is induced

in a conducting loop (or coil) when there is a

change in the number of magnetic ﬁeld lines (or

magnetic ﬂux) passing through the loop. When

the loop is closed by connecting the ends through

an external load, the induced voltage will cause

an electric current to ﬂow through the loop and

load. Thus, rotational energy is converted into

electrical energy.

Industrial ecology Based on the principle of

dematerialization, industrial ecology focuses on

particular characteristics of raw materials rather

than resources per se with the objective of using

fewer raw materials and less energy per unit of

output.

Transforms production and consumption from

a linear process to a circular energy efﬁcient

one by inventing, exploring, substituting, and

conserving technologies to expand the potential

resource base.

Industrial sludge Semi liquid residue or slurry

remaining from treatment of industrial water

and wastewater.

Industrial waste Residue material from con-

struction, industrial or manufacturing operations.

Industrial solid waste may be solid, sludge, liquid,

or gas held in container and is classiﬁed as

either hazardous or nonhazardous waste. Hazar-

dous wastes may result from manufacturing or

other industrial processes. Certain commercial

products such as cleaning ﬂuids, paints, or pes-

ticides that are discarded by commercial estab-

lishments or individuals also can be deﬁned as

hazardous wastes. Wastes determined to be hazar-

dous are regulated by hazardous waste rules

regulated by USEPA’s Resource Conservation

Recovery Act’s Subtitle C requirements.

Non hazardous industrial wastes are those

that do not meet the USEPA’sdeﬁnition of

hazardous waste—and are not municipal

wastes. These nonhazardous wastes fall under

USEPA’s solid waste management requirements.

See:

toxic waste

Inert gas A gas that does not react with other

substances, such as argon or krypton; sealed

between two sheets of glazing to decrease the U

value (increase the R value) of windows.

Inert solids or inert waste Category of solid

waste that includes soil and concrete that do not

have as hazardous an effect on the environment

as pollutants.

Inert solids or inert waste 133

Inﬁll development Term used to describe build-

ing and developing in vacant lots and areas in

urban neighborhoods and city centers. This type

of development was originally designed to build

new homes in coveted older neighborhoods. As the

practice increased, it has beneﬁted neighborhoods

and downtown areas of cities. City centers have

been revitalized, trafﬁc congestion has been

reduced, more liveable and vital downtown com-

munities have resurged, and more rural areas and

open spaces are saved. Inﬁll development is clo-

sely related in principle to smart growth. One

possible negative effect of inﬁll development may

be the increased cost of upgrading and increasing

utilities and energy. See:

urban renewal

Inﬁltration Uncontrolled air leakage through

cracks and holes in any building element,

especially windows and doors.

Infrared radiation (IR) Heat energy emitted

from a material. The term refers to energy in the

region of the electromagnetic radiation spec-

trum at wavelengths longer than those of visible

light but shorter than those of radio waves. The

electromagnetic spectrum includes all types of

radiation, from x-rays to radio waves to the micro-

waves used in cooking. IR radiation is invisible

to the eye, but it can be detected as a sensation

of warmth on the skin. Radiant heat felt from an

oven or ﬁre is IR radiation. Everything emits IR

radiation, although some of the emissions cannot

be felt because they are too weak.

Greenhouse gases in the atmosphere, espe-

cially water vapor, trap some of this IR radia-

tion, and keep the earth habitable for life.

Clouds also trap some of this radiation. The

reason why the air cools so quickly on a clear,

dry evening is because the lack of humidity and

clouds allows large amounts of IR radiation to

escape rapidly to outer space.

Infrastructure Large structures of a society

which members of the society cannot provide

for themselves and on which society depends to

link members to each other. Infrastructure includes

public utilities, roads, water systems, communica-

tion networks, airports, schools, and hospitals.

Inherently low emission vehicle (ILEV)

Inherently low-emission vehicle is a government

designation that includes limits on both exhaust

pollution and the fuel-cycle (fuel manufacture,

distribution, and dispensing) emissions. Unlike

other (non-zero) emissions standards like low

emission vehicles (LEV), this one can’t be met

by gasoline vehicles because of the fuel-cycle

emission limits. At present, the US standard only

indicates that the vehicle meets environmental

protection exhaust emissions standards and

produces very few or no evaporative emissions.

USEPA manages overall emissions standards

unless state restrictions are more stringent, like

California. The California Air Resources Board

initiated the designations for low emission

vehicles in 1990.

Injection well Constructed well into which trea-

ted water is injected directly into the ground.

The well is generally drilled into aquifers that do

not supply drinking water, are unused aquifers,

or below freshwater levels. Wastewater is pumped

into the well for dispersal or storage into a

designated aquifer.

Inland wetlands Wetlands that include marshes,

wet meadows, and swamps. These areas are often

dry during one or more seasons every year.

Inorganic Term to describe minerals and non-

carbon based compounds.

Inorganic compound Noncarbon-based che-

mical compound. See also:

Organic compound

Inorganic cyanides Toxic chemicals found in

gas hydrogen cyanide. Cyanide salts are mainly

used in electroplating, metallurgy, the production

134 Inﬁll development

of organic chemicals (acrylonitrile, methyl

methacrylate, adiponitrile), photographic devel-

opment, the extraction of gold and silver from

ores, tanning leather and in the making of plas-

tics and ﬁbers. They are also used to manu-

facture fumigation chemicals, insecticides, and

rodenticides. They are released into the water

and soil during the production of the above

products.

Cyanide in surface water will form hydrogen

cyanide and evaporate. It takes years for cyanide

to break down from the air. They settle into the

soil and can contaminate groundwater. Cya-

nides have high acute (short-term) toxicity to

aquatic life, birds, and animals. Cyanides have

high chronic (long-term) toxicity to aquatic life.

Insufﬁcient data are available to evaluate the

chronic toxicity to plants, birds, or land animals.

Cyanides are not expected to bioaccumulate.