NaSBAP Unit Questions (at end of each Unit) Unit 3 – Energy

  • 1. What are the potential global repercussions of current energy consumption patterns? (PG: 6)
  • The possible repercussions to these impacts include economic instability, failure of large-scale agricultural systems, destruction of coastal cities as sea levels rise, health impacts from pollution and resources wars.
  • Collectively, industrialization has increased humankinds aggregated energy consumption to the level where it is causing significant resources depletion (using renewable resources faster than they can be created) air and water quality degradation and global climate change.
  • 2. What is the primary goal of a well-designed sustainable building energy system? (PG: 7)
  • A good energy system design process maximizes the probability of creating a building that meets that needs of the occupants while minimizing environmental impacts.

3. What are the four steps of the building energy system design process? (PG: 7)

  1. Assess Human Functional and Physiological Needs – ….of occupants by conducting a Functional Needs Assessment (FNA) and those affected by energy systems. Users needs vary by task and will vary time wise throughout the day, week, month & year. Address the physiological needs of the occupants affected by the energy systems (visual, thermal, acoustical, respiratory, and psychological, etc.)
  2. Assess the Local Climate – by obtaining accurate data about the building’s location, energy systems can be designed appropriately.
  3. Assess Local Renewable Energy Resources – Every building can use solar radiation for heating and daylight. Renewable energy sources can provide clean, reliable, high-quality energy services, including solar, wind, hydropower, geothermal and biomass.
  4. Design the building’s Energy Systems – After understanding human needs and the surrounding environment and resources, the building’s Energy Systems can be designed to meet occupant needs. The passive solar design can be examined as a foundation and review each major energy system of the building in detail, knowing that they are all connected.

4. How do human functional needs differ from physiological needs? Describe key components of each. (PG: 8)

  • Human functional needs – A Functional Needs Assessment (FNA) will determine what kind of occupant is performing what kind of task in what location during specific hours of the days of the week during the year. Different occupant needs 7 schedules influence the design of energy systems (Who, What, & When).
  • For the physiological needs (5 Needs) – energy systems impact the quality of the occupant experience such as through:

o Visual comfort: (biophilia & daylighting). Light levels and quality & connection to the outdoors.
o Thermal comfort :(draft prevention, monitoring humidity levels, air velocity, and maintaining ambient temperature levels and radiant energy transfer)
o Acoustic: (employing energy technologies that minimize indoor and outdoor sound sources)
o Respiratory health ( providing good IAQ)
o Psychological well-being (maintaining overall comfort levels and allowing for maximum level of occupant control over the environment )

5. Describe how a buildings’ geographic location is impacted by the earth-sun system, and how it informs building design. (PG: 11-12)

  • A well designed building is aware and responsive to its local climate. Many climatological factors are indeed opportunities. Features such as free cooling are provided by nature and provides an opportunity to design a building to take advantage of these free energy services.
  • Northern Climates have to deal with the sun being lower in the sky at different times of the year. They also have to deal with day length & seasonal variance. For those near the equator or poles are not impacted as much.

6. What are the key climate indicators? (PG: 12)

  • This is information about a building’s climate and factors that influence it. These are categorized by broad climate type, such as heating, cooling, maritime, arid, etc.
  • The (6) key climate indicators are:

o Temperature (averages, highs, lows, heating (HDD) / cooling degree days(CDD))
o Precipitation
o Humidity
o Insolation (solar radiation)
o Sunshine / cloud cover
o Wind velocities

7. How can solar energy be used in a building? (PG:13)

  • In sustainable building, the two most important functions served by solar energy are heating and interior lighting. A 3rd potential is electrical generation
  • Buildings can be designed to make use of daily solar energy flows to make up some or all of the difference during cold seasons or times a day.
  • Also, the sun can be tapped to heat water using thermal water heating systems.
  • Many buildings can use of daylight to serve most or all interior lighting needs btwn dawn & dusk.
  • PV can be used to generate electricity to offset both current energy costs and future price increases due to fuel increases. PV can also be used for rural buildings in off-grid applications.

8. What is the basic approach to passive solar heating design and passive solar cooling design?(PG: 18)

  • Passive solar design means using siting & well-designed, static envelope elements to meet a bldg’s energy needs
  • Passive solar heating design – the climate dictates the extent to which passive solar heating is desirable. For a northern climate it will range to more than half a year to less in southern latitudes.
  • This can consists of:

o Collectors (Direct- Windows, skyltgs, doors, clerestories) (Indirect – Trombe walls, water walls, rooftop flat plate, vacuum tube collectors, & sun spaces)
o Absorbers (dark surfaces)
o Thermal Mass to passively mitigate daily temperature swings.
o Controls (Static – windows, overhangs, low ‘E’ coatings on windows) (Dynamic – dampers, fans & operable shutters & automated via timers & temp. sensors).
o Insulation – a critical part of retaining the heat that is collected by the passive solar system.

  • Passive solar cooling design – in the cooling season (i.e. when it’s hot outside), the basic approach is to minimize solar gain, ventilate, and use thermal mass to reduce heating peaks.

o This can involve correct window placement.
o Bldg shape & orientation, i.e. wing walls, overhangs, vegetation for shade.
o Operable windows to introduce cross-ventilation, use of the stack effect to circulate air, Flushing the bldg with cool night air, ceiling fans for constant air flow
o Thermal mass to smooth out the ‘diurnal (reoccurring daily patterns) temperature variations.

9. Explain the difference between conductive, convective and radiant heat transfer. (PG: 22-24)

  • Conductive: (touch) the process by which heat travels from one substance to another, or within a substance, by direct molecular interaction (through walls, windows, the roof & foundation). It is a function of the temperaturedifference between the indoors and outdoors, the insulating value of the building envelope elements, and the area of the interface.

o Conductive Heat transfer can be determined by dividing the building envelope into subsystems, e.g. walls, windows, roof, etc. and calculating the thermal energy flow through each over a certain time period, then summing the system to determine a value for the whole building.

  • Convective: (gas) the process by which heat is transferred via the mass movement of molecules stimulated by temperature, pressure, or differences into a space.

o Re: air infiltration or leakage, such as imperfect seals around building components, defects in structural materials, ingress/egress.
o 20-40% of thermal energy losses in buildings are due to infiltration (ASHRAE 1992 Fundamentals)

  • Radiant Heat transfer: (waves) the process by whereby heat or light is sent through space via solar rays from atoms and molecules as they undergo internal change.

o Direct solar gain is the most significant radiant flow.

10. What are “R” and “U” values, and how are they calculated and used in building applications? (PG: 23)

  • ‘U’ value: (thermal conductivity for a 2D surface) are Btu per square-foot of interface area per degree F temperature difference per hour.

o U = Btu / Ft2 x °F x Hour. A high ‘U’ value means high heat flow or the surface is NOT a good thermal insulator.

  • ‘R’ value: the reciprocal of ‘U’ value = (thermal conductivity for a 2D surface) are Btu per square-foot of interface area per degree F temperature difference per hour.

o R = Ft2 x °F x Hour / Btu. A high ‘R’ value indicates low heat flow, i.e., a surface is a GOOD thermal insulator.

11. Describe the elements of the building envelope / enclosure. (PG: 24-26)

  • (4) Building Envelope Design Principles: (PG: 26)

o Understand minimize loads first.
o Use passive solar design second.
o Windows are critical to energy systems.
o Use whole-building energy analysis tools to optimize envelope performance.

  • (5) Building Envelope Design Elements: (PG: 24-26)

o Walls: source of infiltration; usually has greatest contact with outdoors; studs in wood framed wall break up insulation and can act as thermal bridges; Requires air/vapor barriers
o Windows: responsible for conductive, convective and radiant heat flow as well as ventilation, daylighting and connection to outdoors.

  • Glazing (glass, plastic, multiple panes)
  • Frames (wood, fiberglass, aluminum, vinyl)
  • Films, coatings and fill can alter performance of windows
  • Interior and exterior shading devices
  • Fenestration systems (i.e. envelope penetration for daylight through windows, skylights, etc.
  • Skylights and solar tubes

o Doors: allow for conductive heat flow, infiltration and heat transfer via ingress / egress
o Roof: subject to significant heat flow through upward pressure of warm air; roof material with low albedo (a measure of the reflectivity) can create heat island effect, which results in microclimate (allows heat to concentrate).
o Foundation: foundation heat flows play an important role in managing interior moisture & air quality.

12. Describe the Heat Balance Equation. (PG: 29)

  • The Heat Balance Equation is a systems-engineering approach to representing the flow of heat in and out of a building. It assumes that the HVAC system is responsible for making up the difference in heat gain or loss due to envelope losses, solar heat gain through windows, internal occupant equipment, heat production and thermal losses due to air ventilation.

o Equation w/ “Q” as heat – Q (HVAC) = Q (envelope) + Q (solar) + Q (internal) + Q (ventilation)

  • When considering HVAC cooling (in particular), two kinds of heat must be distinguished for the purposes of calculation the heat transfer load:

o Sensible heat: related to perceivable increases & decreases in the temp of a given quantity of air.
o Latent heat: related to the variable moisture content of a quantity of air.

  • The sum of the sensible & latent heat loads is the total cooling load.

13. What are the common functions of a commercial HVAC system, and what are common HVAC components that meet these functions? (PG: 30)

  • (7) HVAC system common functions:

o Heating
o Cooling
o Ventilation
o Humidification
o Dehumidification
o Air cleaning
o A combination of these functions.

  • (3) HVAC system common components:

o A heating source
o A cooling sources
o A distribution system
o Controls
o Other components, i.e., heat recovery ventilators and thermal energy storage systems.

  • (7) common components of HVAC that meet these functions :

o Heating Sources: Furnaces, Boilers, Electric Heat pumps, Geo Exchange, Solar Collectors
o Cooling Sources: Refrigeration cycle (compresses refrigerant fluid then expanded through a valve, absorbing heat from surrounding medium); Absorption Refrigeration (uses heat to boil a refrigerant which is condensed and expanded through a valve. Heat rather than a compressor, creates an expandable fluid).
o Ventilation & Distribution: Ventilation puts a combination of fresh outside air and filtered interior air into a building space, whereas Distributed air is fresh and conditioned air to a building space.
o Heat- Recovery ventilators: use a heat exchanger to capture the heat or cool in exhaust air and transfer it to incoming supply air.
o Thermal-Energy Storage systems: for buildings with substantial cooling needs, thermal energy storage can generate cool during off-peak periods, and distribute it during the day. Thermal energy storage systems chill water, produce ice, or cool a phase-change material at night and then release the cool during the day.
o HVAC Controls: include operable windows, thermostats, fans, adjustable airflow controllers, timers, various sensor-based switches & EMS (energy mgmt systems).

14. Describe the (7) key practices of sustainable HVAC design. (PG: 34-35)

  • Design Process strategy – ensure an effective design process in the beginning; good design process will result in accurate understanding of occupant needs, which can eliminate the need to oversize the HVAC system.
  • Load Reduction – Also known as passive HVAC; can be more cost-effective to reduce the need to condition a space rather than provide mechanical services to accomplish this. (this can be investing in high-efficiency lighting or increasing wall insulation, or incorporate passive solar design, to reduce space heating and cooling needs)
  • Integration – Design HVAC systems with maximum integration of components and with natural energy flows (e.g. the sun, wind, local earth / water temperatures reservoirs).
  • Design Optimization – an optimized design process balances (3) economic, engineering, and environmental requirement. 1st, an optimized design process will balance all 3 objectives by using an accurate system life-cycle analysis or LCA. 2nd, the technical design of the system can be optimized through an accurate understanding of the dynamic occupant load, and by computer modeling the operation of the system.
  • Engineering Opportunities – Utilize basic engineering principles, e.g. natural assets (free sunshine, free natural cooling, free temperature reservoir in the soil, municipal and ground water; don’t throw it away (production of effectively using waste-heat from industrial process (cogeneration) or use of steam from electrical power); create big and short pipes to create small pumps (good upfront design can reduce initial equipment cost & lifetime energy bills); incredible synergies (tunnel through the cost barrier to allow for additional long-term savings and reduced 1st cost in other areas of a project).
  • Commissioning (Cx)– this means you are checking the HVAC for maximum efficiency; means that you are ensuring prior to occupancy that the HVAC system is designed and installed correctly and that occupant has sufficient training to operate the system.
  • Maintenance –be sure there are well documented procedures for ensuring the effective operation of the system as designed.

15. What are the human biological benefits provided by daylight? (PG. 39)

  • Important for synthesis of Vitamin D and regulation of human sleep / wake cycle and offsetting Seasonal Affective Disorder (SAD).
  • Daylight is associated with increased performance, reduction in absenteeism, quicker illness recovery rates.

16. Describe the guidelines for effectively integrating daylighting strategies with electric lighting (6). (PG:42)

  • Energy savings potential cannot be realized unless the electric lighting system is designed to work with the available daylight, and automatically dimmed or switched in response to varying daylight levels.
  • (6) Daylighting & electric lighting integration strategies

o Design layered electric lighting approach (i.e. task, accent, ambient, etc.) and provide individual control of each lighting layer.
o Align ambient electric lights parallel to the daylight contours (isolux)
o Establish electric lighting control zones representing uniform daylight levels.
o Use automated photocells to switch or dim electric lighting zones relative to the available daylight.
o Choose between switching & dimming wisely. Switching is generally less expensive, but produces abrupt light level changes that may not be appropriate for some concentrated work areas. Dimming is less expensive, yet its gradual adjustment of electric lighting levels is not usually noticeable.
o Provide manual lighting controls to allow occupants to select even lower electric lighting levels.

17. What is green power, and what are some examples of how green power is implemented? (PG: 48)

  • Green power is electricity generated from renewable energy or other clean sources which can come from a utility or can be generated on-site. (Case Study: Seattle City Light’s (SCL))

o Energy portfolios include different mixes of electricity sources, e.g. a mixture of wind, hydropower, or natural gas.
o When green power is purchased, it does not mean that the electricity used by the purchaser is generated by the renewable energy sources or clean energy technologies. Instead, the utility is promising to use the green power revenue to invest in renewable / clean energy technologies, so the relationship between paying for green power and the environmental benefit is indirect, but real.
o Green power can be certified by “Green-e”.

18. Describe the different accounting methodologies for calculating the value of investments of energy efficiency. (PG: 52)

  • Simple payback period – “….how many years’s worth of savings it will take to recover the higher first cost of an energy-efficiency or renewable energy investment. The discounted payback period is more accurate, as it incorporates the the changing value of money over time(Time Value of Money – TVM).
  • Internal Rate of Return – represents the net present value of the annual savings stream expressed as a percentage of the additional initial investment.
  • Life Cycle Cost Analysis (LCCA) – implies a long-term perspective.

Other Important Energy Concepts

  • The philosophy of the design of building energy systems is to:

 

  1. Understand occupant needs
  2. Meet as many needs as possible through renewable energy resources
  3. Satisfy remaining loads with passive solar design elements
  4. Use Intg. Design strategies & high – efficiency tech. to provide the balance.

 

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