EC exam 2
A multi-story building with numerous interior thermal zones (not located near the building envelope) is a likely candidate for the application of
a central HVAC system
A "building management system" refers to:
a control system that centrally regulates the HVAC systems in most large buildings
. In the context of climate control systems design, a "tradeoff" is best described as:
accepting less-than-ideal performance in one system to improve performance in another system
Which central HVAC system generally requires the largest distribution tree:
all-air
The four primary classifications of HVAC systems are:
all-air, air and water, all-water, and direct refrigerant
An "induction" HVAC system is an example of
an air and water system
A tall building has deep floorplates and is illuminated primarily by electric light sources. This building is most likely to be:
an internal-load-dominated building
A single-story, open-plan, square office building has only five thermal zones. It would be reasonable to conclude that these five zones correspond to:
the four exposure orientations and the central core
List the four major categories of home energy use.
The four major categories of home energy use is heating and cooling, lighting, cooking and other appliances, refrigerator, and water heating.
List four features of a house using passive solar heating methods and explain each.
The home faces south to capture the greatest amount of solar radiation The south-facing window area is maximized and all others are minimized. Windows have double or triple panels or high-tech design. Roof overhangs or shades block out the high summer sun to cut cooling costs. Deciduous trees on the south side shade and cool the house in the summer.
What is a concept car?
A concept car is designed on paper, but not yet built.
How is active solar heating different from passive solar heating?
Active solar heating different from passive solar heating because passive heating doesn't require outside energy to operate fans or pumps and active solar heating does.
What is a prototype car?
A prototype car is built and being tested, but not sold.
refrigerant
A refrigerant is a substance or mixture, usually a fluid, used in a heat pump and refrigeration cycle. In most cycles it undergoes phase transitions from a liquid to a gas and back again. Many working fluids have been used for such purposes. Fluorocarbons, especially chlorofluorocarbons, became commonplace in the 20th century, but they are being phased out because of their ozone depletion effects. Other common refrigerants used in various applications are ammonia, sulfur dioxide, and non-halogenated hydrocarbons such as propane.[1] The ideal refrigerant would have favorable thermodynamic properties, be noncorrosive to mechanical components, and be safe, including free from toxicity and flammability. It would not cause ozone depletion or climate change. Since different fluids have the desired traits in different degree, choice is a matter of trade-off. The desired thermodynamic properties are a boiling point somewhat below the target temperature, a high heat of vaporization, a moderate density in liquid form, a relatively high density in gaseous form, and a high critical temperature. Since boiling point and gas density are affected by pressure, refrigerants may be made more suitable for a particular application by choice of operating pressures.
A solar cell converts sunlight directly into __________.
A solar cell converts sunlight directly into electricity.
• thermal gradient
A temperature gradient is a physical quantity that describes in which direction and at what rate the temperature changes the most rapidly around a particular location. The temperature gradient is a dimensional quantity expressed in units of degrees (on a particular temperature scale) per unit length. The SI unit is kelvin per meter (K/m)
• thermostat
A thermostat is a component of a control system which senses the temperature of a system so that the system's temperature is maintained near a desired setpoint. The thermostat does this by switching heating or cooling devices on or off, or regulating the flow of a heat transfer fluid as needed, to maintain the correct temperature. A thermostat may be a control unit for a heating or cooling system or a component part of a heater or air conditioner. Thermostats can be constructed in many ways and may use a variety of sensors to measure the temperature. The output of the sensor then controls the heating or cooling apparatus. A thermostat may switch on and off at temperatures either side of the setpoint. This prevents equipment damage from frequent switching.
Why does a well-sealed home need a home ventilation system?
A well-sealed home needs a home ventilation system to exhaust odors and pollutants, and have fresher and more healthful air. Indoor pollutants are why you should open your windows and doors whenever there are nice days to air out the house.
• thermal sailing
Users often must base their sactions of the moment on what will be needed later, by manipulating thermal switches.
• ASHRAE/IESNA Standard 90.1
ASHRAE 90.1 (Energy Standard for Buildings Except Low-Rise Residential Buildings) is a US standard that provides minimum requirements for energy efficient designs for buildings except for low-rise residential buildings.
Explain the operating principle of a flat-plate solar collector.
Between a cover and a black plate, water or air is circulated through the collectors to absorb captured hear and carry it to a storage tank. From the storage tank electric fans are used to distribute the heat throughout the house.
Define bioconversion.
Bioconversion is a general term that refers to the transformation of solar energy to chemical energy during photosynthesis. It is also the conversion of biological material into usable products (especially the conversion of biomass into biofuel).
What is the process of changing coal into liquid fuel called?
Coal liquefaction is the process of changing coal into liquid fuel.
Why are compact fluorescent lamps more efficient than incandescent light bulbs?
Compact fluorescent lamps are more efficient than incandescent light bulbs because compact fluorescent lamps directly produce light without heat.
What is daylight factor?
Indoor illuminance from daylight / outdoor illuminance x 100% ,A prime design concern when designing for reliance on daylighting
What does energy conservation mean?
Energy conservation is to use energy wisely and eliminate waste.
List three examples of biofuels.
Forest products - sawdust, bark, paper pulp, wood shavings, scrap lumber, wood dust, and paper. Agricultural and food-processing waste - fruit pits, walnut sells, rice hulls, corn cobs, manures, and sugar cane residue Municipal sewage and solid waste
What are two important factors to consider with regard to daylighting and fenestration?
How high is the window on the wall , How large is the window or skylight area compared to the floor area for each daylight space, Visible Transmittance of the glazing
What is a hybrid car?
Hybrid car is a vehicle that uses electric motors to power the wheels, but gets its power from a small internal-combustion engine and energy conversion rather than from heavy costly batteries
3. Low-transmission low- ε:
In cooling dominated climates, where the sun is the enemy, low U-factor, low SHGC, and even low VT seem warranted. Again the low-E coating is placed on the outer glazing, where it rejects more of the solar gain. With a tinted exterior glazing, even lower SHGC and VLT could result. - See more at: http://sustainabilityworkshop.autodesk.com/buildings/high-performance-windows#sthash.OLutcSsR.dpuf
1) High-transmission low- ε:
In heating-dominated climates where you want to block heat radiation from inside, the low-E coating should be deposited on the outer surface of the interior pane of glass (surface #3). This is good for passive solar heating applications, where a low U-factor is combined with a high SHGC. In this case the coating traps outgoing infrared radiation that otherwise would be lost. Summer overheating can be avoided with external shading devices.
the stack effect
Is a form of convection , Works when a building has openings at both the top and the bottom , Can be present is stair wells and lift shafts of tall buildings due to significant pressure differences
How does a fuel cell differ from a battery?
It differs from a battery in that the chemicals are not stored in the cells, but they are fed into it as power is needed.
What is geothermal energy?
It is energy originating in the earth's crust, especially volcanic regions and can be used to produce electricity.
List three problems associated with the production of synthetic fuels.
Large quantities of water are consumed, about twice the water requirement of an electric power plant of the same energy output. It takes a lot of energy to process coal and change it to oil or gas. There is evidence that many of the PAHs are cancer-causing.
light-to-solar gain ratio (LSG)
Light-to-solar gain (LSG)is the ratio between the SHGC and VT. It provides a gauge of the relative efficiency of different glass or glazing types in transmitting daylight while blocking heat gains. The higher the number, the more light transmitted without adding excessive amounts of heat. This energy performance rating isn't always provided.
low-ε coating
Low emissivity (low e or low thermal emissivity) refers to a surface condition that emits low levels of radiant thermal (heat) energy. All materials absorb, reflect and emit radiant energy, but here, the primary concern is a special wavelength interval of radiant energy, namely thermal radiation of materials with temperatures approximately between 40 to 60 degrees Celsius. Low-emissivity windows[edit] Window glass is by nature highly thermally emissive, as indicated in the table above. To improve thermal efficiency (insulation properties) thin film coatings are applied to the raw soda-lime glass.
• National Fenestration Rating Council (NFRC)
NFRC ANS Standards NFRC is an American National Standard Institute (ANSI) Accredited Standards Developer (ASD) and develops and administers comparative energy and related rating programs for fenestration products.
. Trombe walls
Need to be on the south wall of the building , Typically behind a glazed wall , Is a thermally massive element
How much electrical energy is changed into light with an incandescent light bulb? What happens to the rest of the energy?
Only about 10% is changed to light, the rest is lost to heat.
What is passive solar energy?
Passive solar energy is techniques for using solar energy to hear an enclosure that require no nonsolar energy for fans or pumps.
Define R-value.
R-value is the ability of a material to stop heat from passing through.
• superwindows
SUPER WINDOWS are "super-high-performance windows." Our top-of-the-line windows start with three panes of glass with multiple gas-filled insulating spaces. The window units are filled with argon or krypton gas because it's heavier and more dense than air, so it slows down the convection current in the window. Our high-performance windows also have multiple low-E coatings applied to the inner glass surfaces. Features of our SuperWindows Triple pane insulated glass unit (IGU) filled with Argon or Krypton gas provide maximum energy performance up to an R10. Multiple, nearly invisble soft coat Low E coatings block out unwanted heat gain and protect your interior from UV damage. Injected foam-filled frame provides superior insulating performance with an R25. Aluminum reinforced sashes ensure maximum support, strength & security. Insulated glass units with Duraseal™ warm edge spacers reduce unwanted condensation. Virgin vinyl, Purefusion™ welded, frames and sashes provide maximum strength and durability. Unique Windjammer™ sealing system between sashes and main frame ensures an airtight seal and reduces infiltration of dirt, dust and pollen. Nine point locking system provides additional strength and security.
shading coefficient (SC)
Shading coefficient, is a value that determines one type of thermal performance of a glass unit (panel or window) in a building. It is basically the ratio of solar gain (due to direct sunlight) passing through a glass unit to the solar energy which passes through 3mm Clear Float Glass . It is referred to as an indicator to how the glass is thermally insulating (shading) the interior when there is direct sunlight on the panel or window. The shading coefficient (SC) depends on the color of glass and degree of reflectivity. It also depends on the type of reflective metal oxides for the case of reflective glass. Sputter-coated reflective and/or sputter-coated low-emissivity glasses tend to have lower SC compared to the same pyrolitically-coated reflective and/or low-emissivity glass. It is usually a value ranging from 1.00 to 0.00, but experiments[which?] show that the value of the SC is between 0.98~0.10. The lower the rating, the less solar heat is transmitted through the glass, and the greater its shading ability.
• smart windows
Smart glass or switchable glass — also called smart windows or switchable windows in its application to windows or skylights — refers to glass or glazing that changes light transmission properties under the application of voltage, light or heat. Smart glass controls the amount of light (and thereby heat) transmission. When activated, the glass changes from translucent to transparent, changing from blocking some (or all) wavelengths of light to letting light pass through. Smart glass technologies include electrochromic, photochromic, thermochromic, suspended particle, micro-blind and liquid crystal devices.[1]
solar heat gain coefficient (SHGC)
Solar gain (also known as solar heat gain or passive solar gain) refers to the increase in temperature in a space, object or structure that results from solar radiation. The amount of solar gain increases with the strength of the sunlight, and with the ability of any intervening material to transmit or resist the radiation. Objects struck by sunlight absorb the short-wave radiation from the light and reradiate the heat at longer infrared wavelengths. Certain materials and substances, such as glass, are more transparent to the shorter wavelengths than the longer; when the sun shines through such materials, the net result is an increase in temperature — solar gain. This effect, the greenhouse effect, so called due to the solar gain that is experienced behind the glass of a greenhouse, has since become well known in the context of global warming.
How are synthetic fuels produced?
Synthetic fuels produced in the processes of coal gasification and liquefaction, heating of oil shale, and refiing of fuels from tar sands.
What is thermal mass?
Thermal mass is a mass of material, such as rock or water, that can absorb solar radiation in the daytime and then radiate away heat at night. Inside a building, thermal mass tends to moderate indoor temperatures.
List two advantages of a heat pump.
They are more efficient than electrical resistance heating and somewhat more efficient than gas furnaces. They are clean and don't need a chimney.
visible transmittance (VT)
Visible transmittance (VT) is a fraction of the visible spectrum of sunlight (380 to 720 nanometers), weighted by the sensitivity of the human eye, that is transmitted through the glazing of a window, door, or skylight. A product with a higher VT transmits more visible light. VT is expressed as a number between 0 and 1. The VT you need for a window, door, or skylight should be determined by your home's daylighting requirements and/or whether you need to reduce interior glare in a space.
What would be released into the atmosphere by a car that runs on hydrogen?
Water would be released.
2. Selective-transmission low- ε:
Where winter heating and summer cooling are both important, requiring low U-factor and low SHGC, but with a relatively high VT for day lighting. The coating is on the outer glazing, where it blocks incoming infrared radiation, which as heat is then convected away by outdoor air. - See more at: http://sustainabilityworkshop.autodesk.com/buildings/high-performance-windows#sthash.OLutcSsR.dpuf
Explain why wind power and water power are considered indirect forms of solar power.
Wind power is considered indirect forms of solar power because the wind's energy originates in the uneven heating of the Earth. Water power is considered indirect solar energy because water is evaporated by solar hear, lifted and carried by the winds. Also the sun's heating of water (difference between surface waters and ocean depths OTEC) is used to produce electricity.
A "cooling tower" handles which of the following:
condenser water for heat rejection
Which (choose one or more) of the following ratios are actually reasonably important to appropriate performance of the noted system:
cross ventilation: the ratio of inlet opening area to outlet opening area ,direct gain solar heating: the ratio of building heat loss to area of solar collector,conventional cooling: the ratio of sensible heat gain to latent heat gain
. The following benefit is a characteristic of local HVAC systems:
distribution trees are minimized and the control system is simplified
• thermal properties
emittance absorptance k-value (conductivity) C-value (conductance) U-factor (transmittance) R-value (resistance) density specific heat thermal capacity time lag
A boiler flue economizer and a runaround coil are examples of:
energy conservation equipment
Local HVAC systems are most likely to be applied in which types of large buildings:
hotels, motels, and apartments
Which of the following best describes a general trend seen in large building HVAC approaches
improved building automation has made the combination of active and passive strategies a more manageable practice
Energy storage equipment for an HVAC system is most likely to be found:
in the form of water and ice storage tanks
. A Trombe wall is an example of which of the following passive solar heating system types:
indirect gain
• insulator
inorganic, organic, and reflective insulations board, batt, loose-fill, and formed-in-place insulations radiant barrier
The following is NOT a factor when zoning a building for optimal thermal and lighting performance:
room dimensions
The primary difference between sensible and latent heat is:
sensible heat affects dry-bulb temperature, while latent heat affects moisture content
• fenestration
solar heat gain coefficient (SHGC) shading coefficient (SC) visible transmittance (VT) light-to-solar gain ratio (LSG) low-ε coating selective transmission
. A "phase-change" material would normally be used to:
store heat in a passive cooling or heating system
Solar savings fraction (SSF) is best defined as:
the annual purchased energy saved by a passive heating system compared to a building heated by a conventional heating system
. Thermal mass is a critical aspect of passive solar heating systems because:
the mass provides heat storage that tempers potentially large fluctuations in space temperature
Daylight factor (DF) is best defined as
the ratio of daylight intensity between an interior point and an exterior reference point
Cogeneration refers to:
the simultaneous generation of electricity and thermal energy for use in a building
. Prescribed standards for fenestration tend to be small and based on conventional designs
true
Heat flows from areas of higher temperature to areas of lower temperature
true
An all-air HVAC system:
uses only air to deliver heating/cooling effect to conditioned spaces
The acronym "VAV" stands for
variable air volume
