appendix B a glossary of solar energy terms by qjj20151


									appendix B: a glossary of
   solar energy terms

absorbant—the less volatile of the two       ambient temperature—the natural              British thermal unit (BTU)—a unit of
   working fluids in an absorption cool-       temperature surrounding an object;             heat energy; the quantity needed to
   ing device.                                 it usually refers to outdoor tempera-          raise the temperature of one pound
absorber—the surface in a collector that       ture.                                          of water one degree Fahrenheit.
   absorbs solar radiation and converts      atrium—a closed interior court to which      building envelope—the elements (walls,
   it to heat energy; generally a matte          other rooms open; it is often used for      roof, floors) of a building that enclose
   black metallic surface is best.               passive solar collection.                   conditioned spaces.
absorption chiller—air conditioning          auxiliary energy—auxiliary heat plus the     calorie—amount of heat required to
   device that uses heat at 190°F or            energy required to operate pumps,            raise one gram of water one degree
   higher to generate cooling; it may be        blowers, or other devices.                   centigrade.
   powered by solar-heated water.            auxiliary heat—the heat provided by          clerestory—a window located high in a
absorptivity—the ratio of the energy            a conventional heating system for             wall near the eaves, used for light,
   absorbed by a surface to the energy          periods of cloudiness or intense cold,        heat gain, and ventilation.
   absorbed by a black body at the same         when a solar heating system cannot        coefficient of heat transmission—the
   temperature.                                 provide enough heat.                         rate of heat transmission measured
active solar energy systems—in contrast      azimuth—the angular distance from true          per degree of temperature difference
    to passive solar energy approaches,         south to the point on the horizon            per hour, through a square foot of
    an active solar energy system uses          directly below the sun.                      wall or other building surface. It is
    outside energy to operate the system,    backup energy system—a backup                   usually called the U-value.
    to transfer the collected solar energy      energy system using conventional          collection—the process of trapping solar
    from the collector to storage, and to       fuels should be provided for heating          radiation and converting it to heat.
    distribute it throughout the living         and domestic hot water. This system       collector—a device that collects solar
    unit. Active systems can provide            should be capable of providing all            radiation and converts it to heat.
    space heating and cooling and do-           of the energy demand during any
    mestic hot water.                                                                     collector aperture—the glazed open-
                                                period when the solar energy system
                                                                                              ing in a collector that admits solar
airlock entry—a vestibule enclosed with         is not operating. Components and
    two airtight doors; it reduces heat         subsystems may be used as parts of
    loss by limiting the movement of            both systems where the component or       collector efficiency—the ratio of the heat
    heated air.                                 sub-system is a recognized, acceptable        energy extracted from a collector to
                                                product in the conventional building          the solar energy striking it.
air-type collector—a collector that uses
    air for heat transfer.                      industry.                                 collector tilt—the angle between the
                                             berm—see earth berm.                             horizontal plane and the solar collec-
altitude—the angular distance from the
                                                                                              tor plane, designed to maximize the
    horizon to the sun.
                                                                                              collection of solar radiation.

comfort zone—the range of temperature          damper—a control that permits, pre-         double-glazed—covered by two layers
   and humidity in which most people              vents, or controls the passage of air       of glazing material (commonly glass
   feel comfortable.                              through a duct.                             or plastic).
concentrating collector—a collector with       degree day—a unit of measurement for        double-walled heat exchanger—a heat
   a lens or a reflector that concentrates        outside temperature; it is the differ-      exchanger that separates the collector
   the sun’s rays on a relatively small           ence between a fixed temperature            fluid from the potable water by two
   absorber surface.                              (usually 65°F [18°C]) and the average       surfaces; it is required if the collector
conduction—the flow of heat between a             temperature for the day.                    fluid is nonpotable.
   hotter material and a colder material       design heating load—the total heat          drainback—a type of liquid heating
   that are in direct physical contact.           loss from a building under the most         system that is designed to drain into
conductivity—the property of a material           severe winter conditions likely to          a tank when the pump is off.
   indicating the quantity of heat that           occur.                                   earth berm—a mound of dirt that abuts
   will flow through one foot of a mate-       design outside temperature—the lowest           a building wall to stabilize interior
   rial for each degree of temperature            outdoor temperature expected during          temperature or to deflect the wind.
   difference.                                    a heating season.                        emissivity—the ratio of the energy
convection, forced—commonly, the               diffuse radiation—indirect scattered          radiated by a body to the energy
   transfer of heat by the forced flow of          sunlight that casts no shadow.            radiated by a black body at the same
   air or water.                               direct radiation—sunlight that casts          temperature.
convection, natural—the motion of a gas           shadows, also called beam radia-         energy audit—an accounting of the
   or liquid, caused by temperature or            tion.                                       forms of energy used during a desig-
   density difference, by which heat is        direct solar gain—a type of passive            nated period, such as monthly.
   transported.                                   solar heating system in which solar      eutectic salts—a mixture of two or
cooling pond—a large body of water that           radiation passes through the south-         more pure materials that melts at a
   loses heat from its surface, largely by        facing living space before being            constant temperature; a material that
   evaporation but also by convection             stored in the thermal mass for long-        stores large amounts of latent heat.
   and radiation.                                 term heating.                            evaporative cooling—a method of space
cooling tower—a device for cooling wa-         distribution—the movement of collected         conditioning that requires the addi-
   ter by evaporation.                             heat to the living areas from collec-      tion of bodies of water or of moisture
cover plate—a layer of glass or transpar-          tors or storage.                           for cooling the living spaces.
   ent plastic placed above the absorber       diurnal temperature range—the varia-        fan coil—a unit consisting of a fan and
   plate in a flat-plate collector to reduce      tion in outdoor temperature between         a heat exchanger that transfers heat
   heat losses.                                   day and night.                              from liquid to air (or vice versa); usu-
                                                                                              ally located in a duct.

flat-plate collector—a solar collection        heat gain—as applied to heating or          heliostat—an instrument consisting of a
    device in which sunlight is converted         cooling load, that amount of heat            mirror mounted on an axis moved by
    to heat on a flat surface; air or liquid      gained by a space from all sources           clockwork; the heliostat reflects sun-
    flows through the collector to remove         (including people, lights, machines,         beams in one direction, usually to a
    the heat.                                     sunshine, etc.).                             central absorber located in a tower.
flywheel effect—the damping of interior        heat pump—an electrically operated          hybrid solar energy system—a hybrid
    temperature fluctuations by massive           machine for heating and cooling;            system is one incorporating a major
    construction. (See diurnal tempera-           when heating, it transfers heat from        passive aspect, where at least one of
    ture range.)                                  one medium at a lower temperature           the significant thermal energy flows
forced-air heat—a conventional heat-              (called the heat source) to a medium        is by natural means and at least one
    ing distribution system that uses a           at a higher temperature (called the         is by forced means.
    blower to circulate heated air.               heat sink), thereby cooling the source   hydronic system—a conventional heat-
                                                  (outside air) and warming the sink          ing system that circulates hot water,
galvanic corrosion—the deterioration of
                                                  (the house); when cooling, the heat         usually 160°F to 180°F, through base-
   tanks, pipes, or pumps that occurs
                                                  pump functions much like an air             board finned pipes or radiators.
   when a conducting liquid permits
                                                  conditioner— taking unwanted heat
   electrical contact between two differ-                                                  indirect gain solar—a type of passive
                                                  from the heat source (a building)
   ent metals, causing the more active                                                        solar heating system in which the
                                                  and dumping it to the heat sink (the
   metal to corrode.                                                                          storage is interposed between the
Glauber’s salts—a term for sodium                                                             collecting and the distributing sur-
                                               heat sink—a medium (water, earth, or           faces (e.g., Trombe wall, water wall,
   sulfate decahydrate, which melts at
                                                  air) capable of accepting heat.             or roof pond).
   90°F; a component of eutectic salts.
                                               heat source—a medium (water, earth, or      infiltration—the uncontrolled movement
glazing—a material that is translucent or
                                                  air) from which heat is extracted.           of outdoor air into a building through
    transparent to solar radiation.
                                               heat transfer—conduction, convection,           leaks, cracks, windows, and doors.
greenhouse—in passive solar design,
                                                  or radiation (or a combination of        infrared radiation—the invisible rays
   an attached glazed area from which
                                                  these).                                      just beyond the red of the visible
   heat is withdrawn to the living space
   during the day.                             heating load—the rate of heat flow re-          spectrum; their wavelengths are lon-
                                                  quired to maintain indoor comfort;           ger than those of the spectrum colors
heat capacity (specific heat)—the quan-
                                                  measured in BTU per hour.                    (.7 to 400 microns), and they have a
   tity of heat required to raise the
                                               heating season—the period from early            penetrating heating effect.
   temperature of a given mass of a
   substance 1°F.                                 fall to late spring during which heat    insolation—the amount of solar ra-
                                                  is needed to keep a house comfort-          diation (direct, diffuse, or reflected)
heat exchanger—a device that transfers
                                                  able.                                       striking a surface exposed to the sky;
   heat from one fluid to another.

    measured in BTU per square foot per       microclimate—the variation in regional            of shading collector areas from
    hour (or in watts per square meter).         climate at a specific site; caused by          exposure to the summer sun and
insulation—a material that increases             topography, vegetation, soil, water            provisions to induce ventilation to
   resistance to heat flow.                      conditions, and construction.                  reduce internal temperatures and
                                              movable insulation—a device that re-              humidity.
isolated solar gain—a type of passive
    solar heating system in which heat          duces heat loss at night or during          payback—the time needed to recover
    is collected in one area to be used         cloudy periods and permits heat gain           the investment in a solar energy
    in another (e.g., greenhouse or attic       in sunny periods (e.g., Beadwall®,             system.
    collector).                                 insulated draperies, automatic shut-        peak load—the maximum instantaneous
                                                ters); it may also be used to reduce           demand for electrical power, which
kilowatt—a measure of power or heat flow
                                                heat gains in summer.                          determines the generating capacity
    rate; it equals 3,413 BTU per hour.
                                              nocturnal cooling—cooling through ra-            required by a public utility.
kilowatt-hour (kwh)—the amount of
                                                 diation of heat from warm surfaces         percent possible sunshine—the amount
    energy equivalent to one kilowatt
                                                 to a night sky.                               of radiation available compared to
    of power being used for one hour;
    3,413 BTU.                                nonpotable—water that is not suitable            the amount that would be present if
                                                 for drinking or cooking purposes.             there were no cloud cover; usually
langley—a measure of solar radiation; it
                                              nonrenewable energy source—a mineral             measured on a monthly basis.
   equals one calorie per square centi-
   meter, or 3.69 BTU per square foot.           energy source that is in limited sup-      phase-change—see latent heat.
                                                 ply, such as fossil (gas, oil, and coal)   photovoltaic cell—a device without
latent heat—the change in heat content
                                                 and nuclear fuels.                            any moving parts that converts light
    that occurs with a change in phase
    and without change in temperature;        passive solar energy systems and                 directly into electricity by the excite-
    the heat stored in the material during       concepts—passive solar heating                ment of electrons.
    melting or vaporization. Latent heat         applications generally involve energy      potable—water that is suitable for drink-
    is recovered by freezing a liquid or         collection through south-facing               ing or cooking purposes.
    by condensing a gas.                         glazed areas; energy storage in the
                                                                                            preheat—the use of solar energy to
                                                 building mass or in special storage
life-cycle cost analysis—the accounting                                                        partially heat a substance, such as
                                                 elements; energy distribution by
    of capital, interest, and operating                                                        domestic potable water, prior to heat-
                                                 natural means such as convection,
    costs over the useful life of the solar                                                    ing it to a higher desired temperature
                                                 conduction, or radiation with only
    system compared to those costs with-                                                       with auxiliary fuel.
                                                 minimal use of low-power fans or
    out the solar system.                                                                   prompt wall—a thin, low-mass wall
                                                 pumps; and a method controlling
liquid-type collector—a collector that           both high and low temperatures                similar to a Trombe wall, but de-
    uses a liquid as the heat transfer           and energy flows. Passive cooling             signed to respond more rapidly to
    fluid.                                       applications usually include methods          solar gain.

pyranometer—an instrument for mea-               measured over an entire heating           solar furnace—a solar concentrator used
   suring direct and diffuse solar radia-        season.                                       to produce very high temperatures;
   tion.                                      selective surface—a surface that is a            also a trade name for a modular
pyrheliometer—an instrument that                  good absorber of sunlight but a poor         air heating system, usually ground
   measures the intensity of the direct           emitter of thermal radiation, used as        mounted, with rock storage.
   radiation from the sun; the diffuse            a coating for absorbers to increase      solar gain—the part of a building’s heat-
   component is not measured.                     collector efficiency.                        ing or an additional cooling load that
radiation—the process by which energy         sensible heat—heat which, when gained            is provided by solar radiation strik-
   flows from one body to another when           or lost, results in a change in tem-          ing the building or passing into the
   the bodies are separated by a space,          perature.                                     building through windows.
   even when a vacuum exists between          shading coefficient—the ratio of the         solar noon—the time of day when the
   them.                                         amount of sunlight transmitted                sun is due south; halfway between
refrigerant—fluid, such as Freon®, that          through a window under specific               sunrise and sunset.
    is used in heating or cooling devices,       conditions to the amount of sunlight      solar radiation—energy radiated from
    such as heat pumps, air conditioners,        transmitted through a single layer            the sun in the electromagnetic spec-
    or solar collectors.                         of common window glass under the              trum; visible light and infrared light
renewable energy source—solar energy             same conditions.                              are used by solar energy systems.
   and certain forms derived from it,         solar access or solar rights—the abil-       solar thermal electric power—the indi-
   such as wind, biomass, and hydro.              ity to receive direct sunlight that          rect conversion of solar energy into
reradiation—the emission of previously            has passed over land located to the          electricity by solar collectors, a heat
    absorbed radiation.                           south; the protection of solar access        engine, and electrical generators.
                                                  is a legal issue.                        solarium—a living space enclosed by
retrofit—to modify an existing building
    by adding a solar heating system or       solar cell—see photovoltaic cell.                glazing; a greenhouse.
    insulation.                               solar collector—a device that collects so-   specific heat capacity—the quantity of
rock bin or rock bed—a heat storage con-          lar radiation and converts it to heat.      heat needed to change the tempera-
   tainer filled with rocks or pebbles,       solar constant—the average intensity            ture of one pound of a material by
   used in air-type solar heating/cool-          of solar radiation reaching the earth        one degree Fahrenheit (or one ki-
   ing systems.                                  outside the atmosphere; 429.2 BTU            logram of a material by one degree
                                                 per square foot per hour (or 1,354           centigrade).
R-value—see thermal resistance.
                                                 watts per square meter).                  stack effect—the rising of heated air over
seasonal efficiency—the ratio of the                                                           a dark surface by natural convection
   solar energy collected and used to         solar fraction—the percentage of a build-
                                                  ing’s seasonal heating requirement           to create a draft, used to provide
   the solar energy striking the collector,
                                                  provided by a solar system.

   summer ventilation in some passive        thermal radiation—see infrared radia-             “tromped” wall (Trombe + prompt =
   houses.                                      tion.                                          tromped) was coined.
stagnation—a high-temperature con-           thermal resistance (R-value)—the ten-          U-value—see coefficient of heat trans-
   dition obtained in a solar collector         dency of a material to retard the flow         mission.
   when the sun is shining and no fluid         of heat; the reciprocal of the coeffi-      vapor barrier—a waterproof liner used
   is flowing through the collector; tem-       cient of heat trans-mission.                   to prevent passage of moisture
   peratures range from 250°F to 400°F,      thermosiphoning—heat transfer through             through the building structure. Vapor
   depending on collector design. Any            a fluid (such as air or liquid) by cur-       barriers in walls and ceilings should
   condition under which a collector is          rents resulting from the natural fall of      be located on the heated side of the
   losing as much heat as it gains.              heavier, cool fluid and rise of lighter,      building.
storage—the device or medium that ab-            warm fluid.                                wet-bulb temperature—the lowest
    sorbs collected solar heat and stores    tilt angle—see collector tilt.                   temperature attainable by evaporat-
    it for later use.                                                                         ing water in the air; a measure of
                                             tracking—for a collector, a device that
storage capacity—the quantity of heat            causes the panel to follow the sun.          humidity.
    that can be contained in a storage                                                      zoned heating—the control of the
                                             transfer medium—the substance that
    device.                                                                                    temperature in a room or a group
                                                 carries heat from the solar collector
sunspace—a living space enclosed by              to storage or from storage to the liv-        of rooms independently of other
   glazing; a solarium or greenhouse.            ing areas.                                    rooms.
sun tempering—a method that involves         trickle-type collector—a collector in
   a significant daytime solar gain and          which the heat transfer fluid flows in
   an effective distribution system but          open channels on the absorber.
   generally lacks a storage system.
                                             Trombe wall—masonry, typically 8 to 16
therm—a quantity of heat equal to               inches thick, blackened and exposed
   100,000 BTU; approximately 100 cu-           to the sun behind glazing; a pas-
   bic feet of natural gas.                     sive solar heating system in which
thermal lag—in an indirect gain system,         a masonry wall collects, stores, and
   the time delay for heat to move from         distributes heat.
   the outer collecting surface to the in-   tromped wall—a fanciful name for a
   ner radiating surface.                       hybrid low-mass wall that is useful
thermal mass—the heat capacity of a             as a convector of solar heating. It is
   building material (brick, concrete,          similar in effect to a prompt wall yet
   adobe, or water containers).                 it has more mass and is conceptually
                                                similar to a Trombe wall, so the term


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