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SBA Unit 3
Energy and Lighting
| Question | Answer |
|---|---|
| What is energy in the context of building | It is the amalgam of electricity, carbon based organic fuels, and solar radiation to support building and occupant functions |
| IEA | International Energy Agency |
| OECD | Organisation for Economic Devlopment |
| According to the IEA, members of the OECD (North America, Europe, Japan, Korea) the energy consumption is? | OECD members consumed 5 tons of oil per capital and produce 11 tons of CO2 while non OECD members consume less than 1 ton of energy per capita and produced 2 tons of CO@ |
| What is the lifetime of a building | 50-100 years: decisions on how a structure is built can affect three or more generations |
| How much of a buildings energy consumption can be reduced through good design | 5 up to 50% (more through innovative design) |
| What is the goal of good energy system design | Maximize needs of occupants while minimizing environmental impacts. A secondary goal is to use the design for learning and innovating |
| What are the 4 steps of the Building Energy Design Process | 1. Assess human functional and physiological needs; 2. Assess local renewable energy resources; 3. Assess the local climate; 4. Design the buildings energy systems |
| Functional needs | schedules, tasks |
| Physiological needs | Visual, thermal, acoustic,respiratory, physiological |
| Define footcandle | The foot-candle is equal to one lumen per square foot. |
| Light level req'd for stairways | 5 footcandles |
| Light level req'd for reading | 30 footcandles |
| Light level req'd for detailed work | up to 500 footcandles |
| IESNA | Illuminating Enginering Society of North America |
| Other important lighting factors | Light quality - color temprature, spectral distribution, degree of flicker, glare,contrast, variation of depth |
| Factors of thermal comfort | Level of physical activity, clothing, surrounding environment - air temperature, humidity, air velocity, radiant surface temps |
| Factors of acoustic comfort | Generally req'd - no distracting noises and vibration |
| Factors of respiratory health | clean fresh air to occupants |
| Factors of psychological well-being | design systems to be simple and natural - daylight, operable windows |
| Where are the temperate latitudes | Not near the equator or poles |
| Sun path in temperate latitudes | Sunrise in the east then due south at solar noon (may differ from clock noon) then travels in a mirror image of it morning path to the west in the evening |
| Sun location challenges/opportunities | sun low in morning and evening |
| Sun location if the further location is from equator | sun low in the sky and the more pronounced the difference in day length from winter to summer |
| Tilt of the earth on winter solstice | Earth point northern hemisphere away from the sun (summer solstice is the opposite) |
| Earth axis during equinoxes | Earth axis parallel to the sun |
| Sources of climatic variation | Rotation of the earth (night and day) and the earth's tilt (seasons) |
| Key climate indicators | Temperature, precipitation, humidity, insolation (solar radiation), sunshine/cloud cover, wind velocities |
| Define degree days | Degree days are an indication of the aggregated heating or cooling needs of a climate over a time period (usually a month, season or year). Degree days are relative to a base temperature. |
| cont. Degree days | The difference between each day's mean temp and the base temp is summed over the entire time period of interest |
| HDD & CDD | Heating Degree Days & Cooling Degree Days |
| What are the four elements of antiquity and what potential renewable energy flows are they representative of | Fire, air, water, earth are representative of potential energy flows derived from the sun, wind, flowing water, the ground |
| Two most important functions served by solart energy | Heating and lighting, third potential funtion is electric generation |
| Average annual air temperatures in temperate climates are close to what comfort level | Human comfort levels |
| Daylighting benefits | Helps reduce cooling loads. Increase in worker satisfaction and productivity |
| 1998 Pacific Gas and Electric studies on the effect of daylighting shows | Improved test scores in schools by 10-30%, improved retail sales by 40% |
| Benefits of Photovoltaics | Convert incident solar radiation into electric current. More $$ but not dependent on grid and fuel prices |
| Benefits of Wind | Natural ventilation, convective cooling, sometimes power generation |
| Small hydropower defined as | Under 30 MW, microhydro under 100 kW; site to be located near stream or river w/ sufficient head (vertical drop) and flow (water velocity) –hilly mountainous areas |
| “Run of the river” system | Simplest small hydropower system |
| In most of US, just under the surface, the earth’ temp | Constant 50-60 degrees F, can be used to heat or cool water or air |
| Geothermal heat pumps | Actively circulate fluid through buried heat tubes. Used in radiant heating/cooling or transfer heat/cool to another fluid in a heat exchanger |
| Biomass | Biomass consists of all non-fossil organic materials that have intrinsic chemical energy content. |
| Non-fossil organic materials | Trees, plants, municipal solid waste, municipal biosolids (sewage), animal wastes (manures), forestry and agricultural residues, certain types of industrial waste |
| Why is biomass renewable | Only a short period of time is needed to replace what is consumed as an energy source |
| What type of fuel can biomass be converted to | Biomass can be combusted directly for heat, converted to gas for combustion, liquified for transportation fuel. |
| Where else can biomass be used | Biomass can be used in turbines and fuel cells at high fuel conversion efficiencies |
| Buildings energy systems | Building envelope, HVAC, lighting, plug loads, domestic hot water |
| What is the general philosophy of building energy systems | 1.Understand occupant needs, 2.meet as many needs as possible thru renewable energy, 3.Satisfy remaining loads with passive solar, 4. Use integrated and high efficiency design |
| What does passive solar design mean | Passive solar design means to use siting and well-designed, static envelope elements to meet a building's energy needs |
| What aspects of the site need to be analyzed in solar design | Understanding of sun paths, cloud cover, wind, humidity, precipitation, solar access, terrain |
| Use of solar heating in different temperatures | Northern temperature-half to more of the year, Southern latitudes-small portion of the year |
| What does a passive solar heating system consist of | Collectors, absorbers, thermal mass, controls, insulation |
| Collectors | windows, skylights, doors, Trombe walls, water walls, rooftop flat plate, vacuum tube, sun spaces |
| Absorbers | dark surfaces integral to thermal mass |
| Thermal mass | example slabs |
| Example of active energy storage system | Collects heat and pump it into a thermal storage reservoir when building in cooling mode. They also take advantage of less-expaensive off-peak energy and distribute stored heat and cool during peak periods |
| Controls | overhangs, low-e coatings, dampers, fans, operable shutters, timers, temperature sensors |
| Insulation | Not technically part of solar gain system but is a crital part of retaining heat collected by passive solar system |
| Passive cooling | During cooling season, minimize solar gain, ventilate, use thermal mass to reduce heating peaks |
| Minimizing solar gain | correct placement of windows, shape orientation for shading, trees, trellises, good insulation, reflective materials |
| Ventilate | cool people not buildings - interaction of interior temperature, humidity, and air flow, cross ventilation, stack effect, flushing building, ceiling fans - comfort at higher ambient air temps |
| Thermal mass | Beneficial for smoothing out diurnal temp variation |
| Integration strategies | Understanding climates of specific locations. ex: Northern climates sun higher in sky in summer than winter. Modeling tools can help with design |
| Heat transfer | Heat transfer is the flow of thermal energy between the building interior and exterior. the interior will always strive to attain thermal equilibrium with the outdoors. Greater temp difference between int/ext, greater rate of heat transfer |
| How is heat transferred | Heat is transferred conductivly thru walls, windows, roof, foundation. Covectively thru ventilation, infiltration,radiantly thru glazing |
| What is conductive heat transfer a function of | Conductive heat transfer isa function of temp difference between indoors an outdoors, the insulating value of bldg envelope elements and area of the interface |
| How is conductive heat transfer calculated | Conductive heat transfer can be calculated by dividing the bldg envelope into subsystems - walls, windows, roof. Calculate thermal energy flow for time period and then sum values |
| Define R-value | R-value = thermal resistance |
| define U-value | U-value = thermal conductance, it is the reciprocal of R-value |
| What is the most important component in the bldg envelopes thermal performance in many climates | Conductive heat transfer |
| Formula for U-value | U=Btu/(ft squared*F*hr) |
| What does a high U-value mean | High U-value means high heat flow, i.e. surface that is not a good thermal insulator |
| Formula for R-value | 1/U |
| What does a high R-value mean | High R-value means low heat flow, i.e. surface that is a an effective thermal insulator |
| Types of convective heat transfer | Air infiltration by mechanical means or air leakage |
| % of thermal energy loss by infiltration | 20-40% energy loss |
| What are the thermal effects of infiltration | 1.Total leakage area 2.pressure difference between int/ext. 3.temp difference between int/ext |
| What happens if bldg sealed to tightly to combat infiltration | Poor IAQ |
| Defrine radiant heat transfer | Heat /loss gain thru transparent/translucent elements. Most significant radiant flow is incoming direct solar gain |
| sources of internal heat gain | 100 W sedentary to 1000 W strenuous activities, lighting, other equipment |
| Balance equation | Building will reach natural equilibrium temp based on outdoor temp, solar gain occupant heat production, convective air transfer. Diiference between equilibrium temp and desired indoor temp made up by bldg heat/cool system |
| Physical components of bldg envelope | Walls: greatest area of contact with outdoors, Windows: responsible for conductive, convective, radiant heat flow, ventilation, daylighting, connection to outdoors, very impt design element, Doors |
| bldg components cont. | Roof: heat flow thru upward pressure of warm air, Foundation: Foundation heat flow role in in managing moisture and air quality |
| Window rating terms | U-factor, Solar Heat Gain Coefficient, visible transmission, air leakage |
| Define albedo | reflectivity of roof material. At low Albedo urban heat islands are created, where the ambient temp is higher in the microclimate than elsewhere |
| Green roof benefits | Green roofs provide insulation as well as affecting stormwater runoff. They can also support biodiversity and urban habitat |
| Design and modeling tools | Ensures occupant comfort, minimizes energy consumption, avoids oversized energy systems |
| Building envelope design principles | 1. Understand and minimize loads first, 2. Use passive solar design second, 3. Windows are critical, 4. Use whole bldg energy analysis tools |
| Define plug loads | Plug loads consist of all electric appliances plugged into receptacles, including lighting systems that are not hardwired. Control dependant on occupant behavior |
| What amount of energy is used to heat domestic water incommercial bldg | Water heating 3% of electricity use and 15% of fuel use. In lodging facilities, hospitals, and restaurants may use up to 1/3 or more of energy |
| Types of commercial bldg water heating | Self-heating storage tanks, tanks integrated with the space heating system, tankless coils, point-of-use heaters, solar water heaters |
| Self heating storage tanks | Can heat during off peak hours |
| Tanks integrated with heating system | Efficient during heating season but inefficient during cooling |
| Tankless and point of use | Both avoid stand-by loss but need large capacity to meet peak demand which may mean more expensive electrical system to handle higher current draw |
| Solar water heater | Cost effective in sunny climates and can be used for preheat in conventional systems |
| Solar water heaters cont. | Can heat water itself or with a heat transfer fluid. Can be used for potable water or hydronic radiant heating, or industrial process water |
| HVAC | Heating, Ventilation and Air-Conditioning - vary greatly in size and components |
| HVAC system components | Boilers, chillers, ducted air distribution with fans, air filters, dehumidifiers, temp controls |
| What is the purpose of HVAC system | HVAC systems exist to provid a safe, healthy, comfortable indoor environment |
| Define ASHRAE | The American Society of Heating, Refrigerating and Air-Conditioning Engineers |
| Indoor environment factors impt to occupants | Air temperature, air quality, surface temp, humidity, air pressure, air velocity, acoustics |
| What is the most impt thing to consider when designing an HVAC system | Thermal environment since heating and cooling is the most significant and costly |
| What is the heat balance equation | The heat balance equation is a systems engineering approach to representing the flow of heat in and out of a bldg. |
| What assumption does the heat balance equation make | It assumes that the HVAC is responsible for making up the difference in heat gain or loss due to envelope losses, solar heat gain, internal occupant/equipment heat production, thermal losses from air ventilation |
| Heat balance equation where "Q" = heat | Q(HVAC)= Q(envelope)+Q(solar)+Q(internal)+Qventilation |
| Define sensible heat | Sensible heat is related to perceivable increases/decreases in temp of a given quantity of air. HVAC cooling system must remove sesible heat in order to maintain desired air temp |
| Define latent heat | Latent heat is related to the variable moisture content of a quantity of air. HVAC cooling system removes moisture from air (dehimidification) that comes from incoming supply air, respiration,plants, condensation |
| What is the sum of sensible and latent heat | Total cooling load |
| What is a critical factor in HVAC design | Managing peak loads |
| How can peak loads be minimized | Load reduction, thermal storage, etc. |
| Centralized HVAC system | Heat and cool are produced in a single location then distributed thru pipes/ducts - typ. large bldg system- more $$ first cost, efficient |
| Distributed HVAC system | Individual rooms or zones have their own packed HVAC units - typ for smaller bldg- lower $$f first cost, inefficient |
| Can centralized and distributed HVAC systems be combined | Yes - depending on use of space |
| Air distribution | Air systems heat or cool air in the central plant and use fans and ducts to distribute the air. Advantage-temp easily controlled, ducts don't require as much insulation as pipes, no water leakage |
| Water distribution | Water (hydronic) systems generate hot or cold water and use pumps and pipes to distribute the water to radiators or air handling units. Advantage-pipes use less space, pumps use less energy than fans, fewer energy loss leakage |
| Heating sources | furnaces, boilers, electric heat pumps, geoexchange, solar collectors |
| Furnaces | Combust fuel to produce heat |
| Boilers | Combust fuel to produce hot water or steam |
| Electric heat pump | Uses refrigeration cycle to exchange heat with outdoor air or water source. Can also be used for cooling by reversing the cycle |
| Geoexchange | derives heat from the earth using circulated air, water or heat exchange fluid. supplemental heating by furnace or boiler |
| Solar collectors | uses solar radiation to heat air, water or heat excahnge fluid. used with supplemental combustion or electric heat source |
| Cooling Sources | refrigeration cycle, absorption refrigeration, evaporative coolers, electric heat pumps, geoexchange |
| Refrigeration cycle | Uses pump to compress refrigerant fluid which is expanded through a valve, absorbing heat from the surrounding medium |
| Absorption refrigeration | Uses heat to boil a refrigerant which is condensed and expanded thru a valve similar to refrigeration cycle, difference is heat is used instead of compressor to create expandable fluid |
| Evaporative coolers | Works by passing air thru a permeable, water-soaked pad; the air cools as the moisture in it evaporates. this system only works in dry climates and results in elevated indoor humidity unless a two-stage cooler is used. Fresh water is used for this system. |
| Electric heat pumps | see above |
| Geoexchange | Derives cool from the earth using circulated air, water or heat exchange fluid. Supplemental cooling provided by air conditioning unit |
| HVAC ventilation | Ventilation is the provision of clean air to building spaces by providing a combination of fresh outside air and filtered interior air |
| HVAC distribution | Present in all configurations except 100% distributed systems - responsible for delivering the fresh and conditioned air |
| Heat recovery ventilators | Also known as air-to-air heat exchanger uses a heat exchanger to capture heat or cool in exhaust air and transfer it to incoming supply air. It's possible to recover 85% or more of the energy in the exhaust air therefore significant potential cost savings |
| Thermal energy storage systems | Thermal energy storage systems chill water,produce ice or cool a phase-change material at night and then release the cool during the day. |
| When are thermal energy storage systems economical | Economical under some combination of three conditions - 1. When energy is significantly more expensive during peak hours, 2. Whan spreading the production of cool over a longer period of time allows smaller cooling equipment |
| cont. from above | 3. When the building is subject to high energy demand charges |
| What is the energy savings of thermal energy storage systems | Thermal energy storage systems don't necessarily save energy, they mostly just move energy consumption to a different time. However, they can result in smaller more efficient HVAC |
| HVAC controls | Operable windows, thermostats, fans, adjustable airflow controllers, timers, various sensor based swithches |
| Building Management Systems | Used in large commercial buildings. Better control and lower energy consumption but increased cost and complexity |
| Creating a sustainable HVAC system | "The greatest opportunities for saving costs over the life of a building occur at the beginning of the design process." AIA Energy Design Handbook |
| Waht is the best way to accomplish load reduction | It is often more cost-effestive to reduce the need to condition a space rather than provide mechanical services, i.e. high efficiency lighting, increased insulation, passive solar strategies |
| Integrated HVAC | Integrate system with natural energy flows-sun, wind, local earth and water temperature reservoirs |
| Optimized HVAC | Meets engr. req., economic and environmental req. - Accurate life cycle analysis |
| Basic HVAC engineering principles | Natural assests, Don't throw it away, The Fan Law. Big, straight, short pipes, tiny pumps, Incredible Synergies |
| Natural assets | Free: sunshine, natural cooling, temperture reservoir in the soil. Municipal water, groundwater |
| Don't throw it away | Investigate all thermal processes for potentially useful heating or cooling by-products e.g. co-generation |
| The fan law | Reducing airflow velocity by a factor of two reduces power needs by a factor of eight |
| Big, straight, short pipes = Tiny pumps | Good design up front can reduce initial equipment costs and lifetime energy bills |
| Incredible Synergies | "Tunneling throught the cost barriers" |
| ACT2 houses | Utility bills 60% less than standard houses |
| Commisioning HVAC | It means ensuring prior to occupancy that the HVAC system is designed and installed correctly, and that the occupant has sufficient training and documentation to operate the system |
| Maintenance of HVAC | Design fro ease of maintenance and provide good documentation for operation |
| Physics of light and electromagnetic spectrum | Light is a frequency range of the electromagnetic spectrum |
| What happens when light strikes an object | It is transmited, absorbed or reflected. We see what is refdlected |
| Characteristics of human vision | Our eyes adapt to the overall light level so that we see contrast or luminance ratios rather than absolute levels. Ahigh contrast ratio creates drama and emphasis |
| How can the contrast ratio be increased | It can be increaed by increasing the focal lighting or decreasing the background lighting which is more energy efficient |
| Good qulity lighting design- what must be considered | Issues of glare, contrast and balance of light around the space, the color content and rendering of light sourcrs in addition to surface light levels |
| Building's daytime lighting needs in perimeter spaces | Natural daylighting can meet almost all needs |
| Costs of using daylight | It saves both lighting and (in some cases) cooling energy: as much as 50% reduction in lighting energy is possible, more if windows/skylights are sized and oriented properly |
| Dayighting benefits | Highest possible quality, provides connection to outdoors, natural variation. Need to understand seasonal and daily movement of sun |
| How does daylighting meet human biological needs | View, Environmental information, improved sprectral quality, variability, higher light levels, biological benefits - vitamin D, sleep/wake cycle, SAD |
| Daylighting design approach | 1.Understand sun and its movement, 2.Understand site and daylight potential, 3.Shape building to provide daylight where needed, 4.Design apertures to deliver needed daylight w/o overheating space. |
| What is the key to good daylighting design | Size and position the apertures to introduce the right quantity and quality of light while minimizing the energy use of HVAC system |
| Toplighting guidelines | To balance energy efficiency and useable daylight, skylight glazing area should be 3-8% of floor area and spaced a distance apart about 1.5 times the room's floor to ceiling height |
| Sidelighting guidelines | Put daylight windows high in the wall to allow deeper daylight penetration. Rough rule of thumb - daylight penetration will extend 2 times the window head height into the space. |
| cont. | Minimize glare, use light colored surfaces around window and skylight openings, curved or splayed surfaces adj. to skylt and wndw, provide operable blinds or shades |
| How can daylight be modeled | Architectural models, computer software |
| Guidelines for intrgrating daylighting into electric lighting schemes | Layered lighting (task/accent/ambient) and provide personal controls for each layer. Align ambient electric light parallel to daylight (isolux) contours. Establish elec. lighting zones representing uniform daylight. |
| cont. | Use automated photocells for switch/dim relative to available daylight. Make choice of dimming and switching available. Provide convenient manual controls. Commission control system and regular mainterance |
| What is the goal of electric lighting in sustainable scheme | To provide supplemental light |
| Lighting system overview | Lamp, ballast, controls, fixture |
| What other factors along with energy efficiency needs to be considered in lighting design | Functional and physiological needs of occupants |
| How is light quality measured | The color rendering index and color temperature |
| Define color rendering index | CRI is a scale of 0-100 that indicates how accurately the light reflects color. Daylight and incandescent provide the standard of 100. |
| Define color temperature | Color temp. describes how "warm" (reddish) or "cool" (bluish) the light source appears to the eye. It's represented by a temperature level that's based on what color of light is radiated when an incandescent material is heated to that temp |
| Sample color temps | Candlelight = 1500 Kelvin, incandscent lamp=3000 K, Bright sunny sky=5500 K, Bluesky=9000-12000 K |
| What made old flourescent lamps unappealing | Low CRI and very cool, caused eye strain with flicker and hum of ballast |
| Define ballasts | Ballasts provide the correct operating current and voltage for starting and operation of lamp |
| Define controls in respect to lighting | Controls are manual or automated - occupancy sensors, dimmers, photocells, timers |
| Define lighting fixtures | The fixture (or luminaire) is the entire lighting unit consisting of the lamp, the physical housing to orient and protect lamp, the socket(s), hardware for install, ballast (if applicable), optional reflectors, diffusers,other light directing elements |
| Incandescent lamps | Conventional lightbulb extremely inefficient - ~5% input energy to visible light, produces waste heat, excellent light quality, short operating lifetime 750-1000 hr |
| Halogen lamp | slightly more efficient than standard incandescent, but not much |
| Fluorescent lamp | approx. 20% efficacy (input energy to visible light), requires ballast |
| Compact fluorrescent lamp | Similar to but slightly lower efficacythan tube fluorescent |
| HID lamps | Includes mercury vapor, high and low pressure sodium, metal halide, and othe high intensity lamps. Industrial or large scale use. Requires ballasts. Long start/restrike |
| LED's | Miniaturized semi conductor lamps. Used for info. not space lighting. Most energy efficient for signage. Long lifetime -decades |
| According to LBL Lighting Systems Group how much light cana fixture tranmit | Most fixtures transmit only 50-70% of lamps output. 80-90% is possible |
| What is the problem with older diffusers - milky white globes, fluorescent lamp covers | They can block 50% or more of light output from age/dirty |
| What is the efficiency of modern lens and diffuser systems | 90% efficient |
| Controls | Conventional toggle switches, dimmers, motion or occupancy detectors, simple timers, photosensors (can provide constant level of illumination), bldg management systems |
| Lighting system design strategies | Understand occupant needs, flexible lighting design for changing needs, maximize daylight use, high quality light at sufficient levels, design separately for ambient and task lighting, provide user control, energy-efficient lamps and fixtures |
| cont. | Use effective design,use design/modeling tools |
| What is green power | Green power is electricity generated from renewable energy or other clean sources and can come from a utility or generated on site |
| Utility green power | Can include wind, hydropower, natural gas. The utility is promising to use the green power revenue to invest inrenewable/clean energy. |
| Green power certification | Green-e |
| Onsite green power | PV or wind. Many onsite renewable energy systems are tied into the grid using the utility as an energy storage system. Net metering or net billing allow the customer to be credited or paid for excess power fed to the grid |
| cont. | when local generating capacity exceeds the load |
| Modeling and Design Tools | Energy 10, DOE 2, BLAST (Building Loads Analysis and SystemThermodynamics), EnergyPlus |
| Benefits of Energy Effective Building Design | Lower operating costs from decreased energy use. Potentially lower first cost, if energy efficiency savings allow energy equipment to be downsized or eliminated. Improved IEQ and occupant experience, possibly increased productivity. Increased stability. |
| cont. | Risk reduction -simpler energy systems |
| How does energy use impact the environment | Energy related climate change, acid rain, loss of biodiversity, diminished natural capital |
| Financial incentives | subsidies, tax credits |
| Accounting methodologies | Simple payback period, discounted payback period, Internal rate of return, Life cycle cost analysis, Life cycle assessment |
| Life cycle assessment | LCA is the most comprehensive and ambitious accounting scheme, wherein the economics and environmental impacts of the extended lifetime of a bldg (predesign-demo and reuse) are analyzed. It's the longest term perspective, the most detailed and difficult |
| cont. | to complete, and generally the most accurate |
| Building energy codes and standards | They are established at state level |
| What is the min. baseline standard for state energy codes as mandated by the fed. govt. | ASHRAE 90.1 |
Created by:
lrpasco
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