Tuts

Question 1

What is the difference between energy conservation and energy efficiency?

Answer 1

Energy conservation is anything that saves energy, that simply uses less energy.

Energy efficiency is specifically using
less energy to provide the same services

Question 2

What might be a “structural” change to the economy that may make Australia’s energy usage do down, but not reduce global energy use?

Answer 2

Exportation of energy intensive production, such as manufacturing.

Manufacture, and heavy industry (like mining) require more energy than other
industries, such as tourism, and retail. If these activities leave Australia due to rising
costs, and move to somewhere that is cheaper (eg a developing country), then
Australia might use less energy, but this energy is still being consumed somewhere.

Question 3

People often talk about the “non-energy” benefits of energy efficiency
programs, what is meant by this? Name 3 non-energy gains that could come
from energy efficiency programs.

Answer 3

• SAVE MONEY
• Less maintenance (smaller systems)
• Noise
• Less GHG emissions
• Longer battery life

Question 4

What other benefits arise by using CFLs that have not been considered (Ie economic)?

Answer 4

• Reduced electricity demand and need for T&D ( Transmission and Distribution) upgrades, reduced need for new power generation plants.
• Reduced GHG emissions particularly CO2
• Reduced HVAC loads in summer due to reduced incandescent heating.
• Reduced product transportation and distribution costs due to fewer number required over time.
• Reduced packaging and storage requirements for similar reasons.
• Reduced maintenance and repair costs
• Drawbacks include higher embodied energy in CFL and disposal
  issues (mercury content).

Question 5

What is the IRR

Answer 5

The Internal Rate of Return (IRR) is defined as the discount rate that would result in a
zero NPV over the period. It is where the future discounted savings match the initial
investment and describes the rate of return (in present dollars) on the initial
investment to pay it back.

Question 6

Name 2 potential additional benefits of installing power factor correction system excluding economic.

Answer 6

• You could significantly reduce the size of the generator needed (usually rated
  in kVA, not kW), therefore less total capital cost
• You could possibly reduce the size of cable needed, as less current is being
  carried, therefore less capital cost
• Less power required in kVA, therefore less dependence on diesel being
  brought in

Question 7

Draw a picture of a thermosiphon solar hot water system and explain how
thermosiphoning transfers the fluid around the system without requiring any energy
input.

Answer 7

Basically uses the difference in density of the water to move hot water into the storage tank above the collector and lets the more dense cold water run to the collector.

Question 8

Name 2 advantages and disadvantages of EV and ICE drivetrains. Discuss how they
come together in hybrid powertrains.

Answer 8

Electric Good:

• Easily Fuel switchable (as in the fuel that produces the electricity)
• Energy is cheap (ish)
• Motors are simple and lightweight - High power density.
• Good at stop/start - no need to idle
• Torque and power across a broad RPM range -> limits need for a gearbox
• Regenerative braking.

Electric Bad:

• Batteries are heavy - long range a challenge.
• Batteries are expensive - long range a challenge.

ICE Good:

• Lot’s of experience with the technology.
• Extremely energy dense fuel.

ICE Bad:

• Difficult to find renewable fuel
• Relatively complex mechanical systems.
• Relatively narrow power and efficiency band, needs a gearbox, and generally stays on at idle.

Question 9

How many different Australian Standards specifically address Energy
Audits? What do they cover?

Answer 9

3 separate standards AS/NZS3598.1.2014, 3598.2.2014, 3598.3.2014. AS3598.1.2014
is the standard referred to in your first assignment. These cover commercial, industrial, and transport efficiency audits.

Question 10

What are the differences between Type 1,2 and 3 Audits?

Answer 10

Type 1 Audits are very broad, and give a quick overview of energy usage.

Type 2 audits are more detailed and involve taking actual measurements over some
time period. Most common but expensive

Type 3 Audits go into great detail of a particular subsystem

Question 11

When completing a Type 1 Audit on a building, do you need to make
recommendations about improvements?

Answer 11

Yes

Question 12

Which of the building rating schemes have a design rating? (This is
they are rated pre construction)

Answer 12

LEED, NatHERS, Green Star and BASIX.

Question 13

Which of the building rating schemes have a performance rating?
(That is looking at how the building ​actually​ performs - not just what
they think will happen)

Answer 13

LEED, NABERS, Green Star, BASIX

Question 14

Transport is a category in which standards? What does this category
refer to specifically?

Answer 14

LEED and Green Star.

Transport of occupants that use the building after it is constructed (eg. work there). It looks at the ways that the buildings has incentives or facilities that encourage occupants to use greener modes of transport - eg bike racks, showers, accessibility to public transport etc.

Question 15

What rating scheme is it compulsory to have on advertisements
when selling or leasing large commercial spaces greater than
1,000m​
2​?

Answer 15

NABERS

Question 16

What does the Community rating scheme encompass? Use either the
LEED or Green Star rating scheme

Answer 16

Green star: Liveability, the promotion of active lifestyles, health and
inclusive spaces, mixed use space (residential and commercial together),
leadership and transparency of building practices, training and community
skill development through the construction process. Local environmental
impacts as well as reducing overall ecological footprint.

Question 17

Which rating scheme(s) would you use for a large renovation on your own home in NSW

Answer 17

BASIX/NatHERS - is compulsory. LEED could also be used if

desired.

Question 18

Which rating scheme(s) would you use for showcasing the benefits of a building that wasn’t rated before construction, but is a very green building at a university?

Answer 18

LEED, Green Star, NABERS (NABERS being the main one

recognised as a performance only rating).

Question 19

Which rating scheme(s) would you use for your current home for which you have made no changes to?

Answer 19

NatHERS

Question 20

You have a highly water efficient existing building, but don’t
care about energy?

Answer 20

In NABERS each category is rated separately - you can chose to
have all of water, energy, waste rated - but each is given a
separate star rating

Question 21

What are MEPS? How are they different to Star Ratings?

Answer 21

Minimum Energy Performance Standards.- They specify the poorest energy efficiency of number of products (fridges, motors etc)
that anyone is allowed to sell (new) in Australia. They are an important safeguard
against really terrible appliances being sold.

Star ratings describe the energy efficiency of a particular appliance compared with other
appliances of the same type and similar size. These provide consumers with easy to
understand information about the energy usage of their appliances.

Question 22

In what situation(s) would you consider installing power factor correction?

How could this save money?

Answer 22

Most commonly Power Factor correction would be installed by commercial and industrial
electricity users with a demand charge. Peak demand charges are generally in KVA or
total/apparent power. This means that improving power factor can reduce the peak demand
charge. Peak demand charges are paid over a period (for example month, quarter, year) based
on the peak demand during that period. Something like $/KVA (peak)/day.

If you ran your own generator and transmission line (such as in a microgrid) there may also be
efficiency and capacity savings of installing power factor correction. Or if you had electrical switchboards/wires/components that are reaching maximum capacity,
improving power factor could give you better utilisation of these components.

Question 23

Why there is a difference in COP for heating and coolling?

Answer 23

The Coefficient of Performance (COP) is defined as the ratio of the useful work out to the work in. Heat pumps transfer heat energy from a low temperature to a higher temperature and so the input of work is
required (this is the opposite of natural heat transfer). If used for heating, the useful work is the energy transferred to the higher temperature. If used for cooling, the useful work is the energy removed from the
lower temperature. For a given amount of work (energy) in, the energy transferred to the higher temperature is greater than the energy removed from the lower temperature.

• Basically its easier to add heat then remove it due to the first law of thermodynamics

Question 24

Saturated vapour pressure and boiling point

Answer 24

A liquid boils when its saturated vapour pressure becomes equal to the external pressure on the liquid. When that happens, it enables bubbles of vapour to form throughout the liquid. If the external pressure is higher than the saturated vapour pressure, these bubbles are prevented from forming, and you just get evaporation
at the surface of the liquid.

Question 25

What is cogeneration? And how does it work?

Answer 25

A gas turbine or re is used to create electricity, and the waste heat produced is used as a useful byproduct - in
the form of heat - water heating, space heating etc. This is recovered through a heat exchanger from the exhaust, but also very often from a cooling jacket (another heat exchanger) around the engine or combustion
chamber

Question 26

What are the advantages of cogeneration?

Answer 26

An increase in useful output for energy put in - therefore increased efficiency!

Question 27

What is CHP?

Answer 27

Combined Heat power, another name for the Cogeneration process

Question 28

What is Combined Cycle Generation? And how it works?

Answer 28

Coupling of a gas turbine cycle + steam cycle using the waste heat from the gas turbine to produce more electricity. CCGT (Combined Cycle Gas Turbines) are one of the two types of large scale gas turbines used in the electricity grid, the other being Open Cycle Gas Turbines (OCGT). CCGT are more expensive to build, but more efficient to run - therefore are used as ‘baseload’ style gas, where as OCGT are used as ‘peaking’ plants, where they are needed much less often.

CCGT plants typically have generation
efficiencies of 55% to 60%.

Question 29

What are the advantages of CCG?

Answer 29

CCG is useful in that it is a more efficient use of gas to produce electricity. Efficiency reaches ~60% - a single gas turbine would have an efficiency of ~40%

Question 30

What is absorption cooling? How does it work?

Answer 30

Using waste heat to be able to cool. This is the 3rd part of a trigeneration system - the first two being the elements of cogeneration.

Says refer to lecture slides but no real how it works. Basically uses solar thermal energy to seperate to heat NH3 and H2O solution, then NH3 heat is released and an expansion valve is used similar to Refrigeration cycle. The cycle also uses a regenerator and pumps. (Hope they show the diagram)

Question 31

How does Absorption cooling save energy?

Answer 31

A pump is pressurising liquid, as opposed to air in a compressor. Air is less dense, therefore requires more
energy to run a compressor than a pump.

Question 32

What are the advantages and disadvantages of absorption cooling?

Answer 32

Advantages: lower maintenance costs, lower running costs, and quieter operation (pump vs compressor).

Disadvantages: Large space required (especially for the solar collectors if that is the way that waste heat is
being collected). Larger capital cost than other options.

Question 33

What determines laminar vs turbulent flow ?

Answer 33

Renolds number above 4000 is turbulent

Question 34

What is a VSD ? What does it do?

Answer 34

A variable speed drive is a device (most often electrical in this course) that is used to run a motor at variable speed (and power). They can control motor speed in a number of ways.

Question 35

What is a VFD?

Answer 35

Variable Frequency Drives are a very common type of VSD. They control synchronous and induction motors by varying the frequency. Only work for AC motors.

VFDs work by rectifying incoming AC, into DC, then inverting it back to AC at the desired frequency.

Question 36

Explain why cogged V belts are more efficient than conventional V belts

Answer 36

Better physical coupling connection due to less slippage. Less stretching of the belt due because the
inside doesn’t need to be compresses as much as the belt goes around a sheave (the pulley). Less
stretching = less loss and reduced wear. Because they wear slower they stay efficient for longer.

Question 37

For a fan or pump system, driven by a 3 phase induction motor, explain why when the flow rate is adjusted away from 100% flow using a throttle valve instead of a VSD, large amounts of energy can be wasted.

Answer 37

Throttling valves are similar to resistors in electrical circuits. They resist the flow of fluid, and create a pressure drop. This itself is an energy loss. It also changes the operating point of the pump, as it increases the derivative/slope on the system curve likely moving away from the maximum operating point of the pump, as well as losing energy to friction losses and pressure/velocity changes.

Question 38

For electric motor systems what is meant by whole of system design and why does this have the greatest potential for energy savings in comparison to considering only individual
components? Discuss five important aspects of an electric motor system that should be
considered in an effort to reduce energy usage.

Answer 38

1. pump size
2. Duct size
3. maintenance
4. system design
5. motor efficiency