1. 3 Heating & Cooling (HVAC) Page 39
[When considering sustainability in HVAC the goal is to provide a healthy and comfortable environment with minimal environmental footprint during both installation and over the life of the system.]
Electricians are almost always involved in HVAC work. In some places, the HVAC contractor handles the low- voltage wiring, while licensed electricians install the power cables and equipment.
However the work is distributed, electricians who are aware of the latest efficient HVAC technologies will be better prepared to meet the demands of tomorrow's construction projects. 3
Heating
& Cooling (HVAC)
Page 39
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2. Sustainable HVAC Operating motors, fans and pumps efficiently
[For sustainable HVAC, electricians will be involved in motors, fans, and pumps, new efficient technologies and BMS systems.]
In this chapter, we will discuss electrical components of pumps, fans and motors and how to make them run more efficiently. We will also discuss new technologies in efficient HVAC systems. Most importantly, we will discuss building control systems, which is an aspect of building HVAC that is most affected by electricians.
Operating motors, fans and pumps efficiently
Sustainable HVAC technologies
Building system controls
Motors Pages 39-40
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3. Motors Motors drive fans and pumps in HVAC systems.
[Motors are key components in HVAC systems and need proper connections.]
Dirty breakers, bad connections, and bad terminations can result in constant inefficient operation.
If a connection or termination is good, you should find little or no voltage drop across it.
But if you find more than a tenth of a volt across a connection, it indicates excessive resistance and a need to clean or repair a dirty, corroded, or loose connection.
Motors drive fans and pumps in HVAC systems.
Inefficiency can result from:
Dirty breakers
Bad connections and terminations
Voltage drop of more than a tenth of a volt indicates connection needs repair.
Bad motor connection:
defective crimp
Motors Pages 39-40
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4. Premium® Energy Efficiency Motors
[Know to look for NEMA Premium Efficiency Motors for greater energy efficiency.]
The National Electrical Manufacturers Association (NEMA) NEMA Premium energy efficiency motors program has standards for highly efficient motors which can use the “NEMA Premium” label.
Motor products must meet or exceed the nominal energy efficiency level requirements listed in this program.
NEMA is also defines the testing methods used to establish whether motors meet basic energy efficiency standards, and standards for transformers.
National Electrical Manufacturers Association (NEMA) Premium® Energy Efficient Motors program establishes standards for highly efficient motors.
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Motors Page 40 4

5. Replacement of Motors and Drives
[A properly sized motor will operate most efficiently.]
Replacement of motors and drives will usually be straightforward, though the electrician is the last line of defense against oversizing and should take this responsibility seriously.
Undersizing a motor results in poor function or complete failure of the equipment.
Oversizing equipment is easy and seldom leads to complaints, but it does lead to installing more expensive equipment, and more importantly, to a lifetime of inefficiency and higher operational costs!
An underloaded motor will use substantially more electric energy than one that is properly sized to the load. A set of software tools and guidelines called MotorMaster+ are available free from the U.S. DOE to help practitioners "right- size" motors and other electrically powered equipment.
On the next few slides, we’ll see that variable speed motors, called VFDs and VSDs, can save even more energy and money.
“Right-Size” Motors! (see MotorMaster guidelines)
Undersized motors function poorly
Oversized motors waste energy and money
Use variable frequency drives (VFDs), or variable speed drives (VSDs), to match speeds to loads
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Using Variable Frequency Drives for Greater Control Page 40 5

6. Variable Frequency Drive (VFD)
[VFDs allow for greater control by adjusting the speed of the motor to match the load.]
Variable frequency drives (VFDs), or variable speed drives (VSDs), are systems that control the speed of AC induction motors.
This is achieved by adjusting the voltage and frequency of the electricity supplied to the motor. This technique allows the motor speed of equipment to vary depending on actual operating conditions, rather than operating inefficiently at only one speed.
Varying the speed of your motors allows the equipment to match the actual load required for pumps, fans, and other machinery more closely.
VFDs convert AC power into DC at the rectifier, which is then fed into an inverter using switching circuits to create a simulated AC voltage of variable frequency and current, which then drives an induction motor. By adjusting the frequency of the electric power, the rotational speed of the motor can be adjusted to match loads by a computerized controller.
VFDs allow for greater control by adjusting the speed of the motor to match the load.
Circuit Diagram of VFD
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Using Variable Frequency Drives for Greater Control Page 40 6

7. EXAMPLE: Use VFD to Control Fan Speed
[Adjusting the fan speed with a VFD instead of throttling the output uses much less power.]
Let’s review the example in the manual on page 41.
After a VFD is installed on a motor, the speed of the motor can be adjusted to match the load.
Now lets look at an example that shows how efficiently a VFD can control air movement by adjusting fan speed rather than throttling the output, which wastes a lot of power.
In this chart, the horizontal axis shows how much air the fan can move in cubic feet per minute (cfm). The vertical axis shows the different levels of static back pressure in inches of water.
The yellow and green fan curves in the graph show how much air the fan can move at different levels of static back pressure for operation at two different speeds, the green fan curve at 400 rpm (revolutions per minute) and the yellow fan curve at 600 rpm. The blue line shows how the back pressure increases with air flow if the damper is wide open.
Suppose a fan delivers 21,500 cfm at 600 rpm at a brake horsepower (BHP) of 12.3 at point A on the graph. To reduce the air flow to 14,400 cfm the air flow can be throttled by a damper, a little door that partially closes the duct. With the same 600 rpm fan speed, shown at point B, this increases the back pressure to over 1.6 inches of water and the power consumption to 18 BHP. Power consumption has increased, while providing the desired lower airflow.
Alternatively, by using a VFD and leaving the damper open, the fan speed can be reduced to 400 rpm to achieve the same 14,400 cfm at point C. With the VFD, there is no damper. The power is reduced from 18 BHP to 3.7 BHP.
The advantage of the VFD is that it uses much less power by making the motor speed match the load.
Adjusting fan speed with a VFD instead of throttling the output uses much less power.
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Using Variable Frequency Drives for Greater Control Page 41 7

8. Wiring a VFD
[Programming for a VFD can be altered if power to VFD is cut off. The VFD’s internal on/off controls should always be used.]
A VFD will come with a complete set of specifications indicating what the current draw will be (for wire sizing), the required voltages and phasing, and what control wires need to be connected. (These will run to temperature sensors and similar instrumentation.)
There is one important issue with VFDs that can be particularly troublesome: Most VFDs are programmable, and have a tiny computer which remember schedules and responses to control wires, such as “turn motor up to 75 percent if this temperature exceeds 110°F.” If power to the VFD is cut off, the computer will, in many cases, forget its program and, when power is restored, start up with a default program or just be “always on.”
This of course eliminates all the efficiency benefits. The VFD unit will have contacts to connect an internal on/off switch.
ALWAYS USE THE VFD's ON/OFF CONNECTIONS. DO NOT PUT AN EXTERNAL ON/OFF SWITCH ON A VFD. (UNLESS INSTRUCTIONS EXPLICITLY SAY YOU CAN.)
If you absolutely must use an external on/off switch (and remember, there is a circuit breaker), use one that can be locked “on” or has some equivalent safeguard.
Program can reset when powered off – controller programming may be lost!
Always use VFD on/off connections
Don’t put an external switch on a VFD unless the instructions explicitly say you can.
Variable Frequency Drive Control
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Using Variable Frequency Drives for Greater Control Page 41 8

9. Fans: Axial vs. Centrifugal
[It is extremely important to accurately size fans, as fans are usually oversized.]
Fans are everywhere in HVAC systems.
Whatever the scale and application, it is very important that the fan be accurately sized for the task. If it is undersized, the air will not be fresh or will be at the wrong temperature, and if it is oversized (which is more common), there will either be excessive heating and cooling loads.
If dampers are used to bring the air flow down to the correct levels, the power being used to drive the oversized fan is wasted.
The manual gives some tips about how to know if your fan is oversized.
Fan dampers waste energy (and money) when compared to using a VFD/VSD motor controller
Fan dampers reduce air flow by decreasing the volume of air going into fan
They increase the pressure generated across the impeller which increases the amount of power required
Oversized fans waste energy
Use VFD instead of fan dampers for more energy efficient control
Axial fan (more efficient)
Centrifugal fan
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Fans Pages 41-42

10. Pumps: Centrifugal vs. Positive Displacement
[Know examples of different pumps in a building as electricians might be connecting them.]
There are various types of pumps in a building. Some of the more common examples are:
A domestic water supply pump boosts water pressure to the building.
A hydronic heat circulation pump provides heating and domestic hot water to HVAC equipment in the building for space heating.
A domestic hot water circulation pump keeps hot water circulating throughout a building so there will be no lag while hot water passes from the water heater to the fixtures in the building.
Oil burners for boilers and furnaces will have a high pressure, positive displacement pump to deliver the oil to the burner head.
Domestic Water Supply
Hydronic Heat Circulation Pumps
Domestic Hot Water Circulation Pump
Oil Burner Pumps and Oil Circulation Pumps
Centrifugal Pump
Positive Displacement Pump
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Pumps Pages 42-43

11. Component Replacement Plan
[A properly implemented component replacement plan makes sure the building has the right size parts when a piece of equipment fails. This plan should be developed with all involved parties.]
It is important for a building to have a replacement plan to ensure that you have the right equipment ready when a component fails.
When a pump fails on a Saturday, the only thing that matters will be getting it going again, and inefficient, oversized equipment is likely to be the quickest route to restoring service.
If spares have been purchased and stored, the correct equipment can be installed quickly, to the satisfaction of both you and your client.
When replacing an existing pump, you will need to know exactly how the system is intended to work. You should have (or create!) the instrumentation diagram and understand the reasons for all the devices included in your system.
Of course, it will be best to work on this with the plumber or the HVAC company if they are available before the pump fails.
A component replacement plan is technically the responsibility of the building owner or facility manager, but electricians should be prepared to lend technical assistance.
Ensure right sized equipment is ready when a component falls apart
Store spare parts
Have the piping and instrumentation diagrams available
Discuss plan with building manager, plumber or HVAC company
Replacement Parts List
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Component Replacement Plan Page 43 11

12. Heat Pumps Moves heat from a heat source to a heat sink
[Electricians have an important role in heat pump installation because they are used in a variety of green HVAC strategies.]
A heat pump is a machine that moves heat from a low temperature “source” to a higher temperature “sink” or (“heat sink”) using mechanical work, generally supplied by an electric motor.
The simplest example is the room air conditioner, which pulls heat from a room at perhaps 75°F and deposits it outdoors at perhaps 95°F. Heat never flows spontaneously from a cool place to a warm place — it must be pushed. This is what the the heat pump does.
Moves heat from a heat source to a heat sink
(air conditioner)
Roof mounted air-source heat pump
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Heat Pumps Pages 44-45

13. Heat Pump / Air Conditioner Cycle
[The heat pump cycle ejects heat by boiling a refrigerant which is then pressurized and condensed to start the cycle over again.]
This diagram shows how this heat pump/air conditioner cycle works.
The device operates by passing liquid refrigerant through a heat exchanger called the evaporator, where the heat required to boil it into a vapor is taken from the space you are trying to cool.
Once the fluid has been fully converted into a vapor, it is sucked into the intake of the compressor, a special pump that squeezes the vapor to a high pressure. When this vapor is pressurized it also becomes quite hot. The vapor then passes into the condenser, a heat exchanger in which the tube carrying the vapor is connected to fins that eject the heat.
As the compressed vapor is cooled, it condenses back into a liquid, although still at a high pressure. The liquid then becomes cold as it passes through a tiny hole (called an expansion valve) into a region of low pressure.
The cycle begins again as the cold liquid is sucked into the evaporator where it is boiled back into a vapor. Electric power will be used by the compressor as well as by any fans or circulation pumps needed to move the air (or other fluid) being heated or cooled.
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Heat Pumps Pages 44-45

14. Types of Heat Pumps Air-source Water-source Ground-source (GSHP)
[A ground-source heat pump (GSHP) uses the ground or groundwater as the heat source during winter heating and as the heat sink during summer cooling – it is more efficient than air- or water-source heat pumps.]
Air-source heat pumps use the outdoor air as a heat source for heating and heat sink for cooling. Best for moderate climates and may require electric heat as backup.
Water-source heat pumps use a boiler for a heat source and a cooling tower as a heat sink. In large buildings, an array of local heat pumps can move heat efficiently from the center to the perimeter of the building.
Ground-source heat pump (GSHP) uses the ground or groundwater as the heat source during the winter heating operation and as the heat sink during the summer cooling. GSHPs are extremely efficient throughout the year in almost any climate as the water in the system is heated or cooled by the Earth. For colder climates, an auxilliary furnace may be required to provide supplemental heat in winter.
For electricians, installations of GSHPs are relatively standard. The packaged heat pump unit itself will have substantial power requirements but these will be clearly specified. Since this is new technology, be prepared for additional coordination prior to installation.
Note that GSHP is not the same as geothermal energy. A GSHP is powered by electricity generated elsewhere. Geothermal energy is extracted directly from high temperature heat stored deep within the Earth, brought to the surface either by natural geysers or drilled wells. Geothermal energy may be a very useful power source in the future, but it is not used on the scale of individual buildings (except in Iceland!).
Air-source
Water-source
Ground-source (GSHP)
Horizontal closed loop GSHP
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Heat Pumps Pages 45-46 14

15. Upgrading HVAC Systems
[HVAC systems use a lot of energy in buildings, and electricians will have opportunities to assist on the installation of more sustainable systems.]
HVAC systems are among the largest users of energy within buildings. Like electrical systems, they typically have a life span less than the life of the building, which means that most HVAC systems will be replaced or retrofitted during a building's life.
This work may be motivated either by a major renovation, a tenant change, or an energy-efficiency project.
The energy use of an HVAC system depends very much on the type of system used.
HVAC systems are among the largest users of energy in buildings
Buildings often outlive their HVAC systems
Retrofitting heating and cooling systems can offer great opportunities for energy savings (and jobs)
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HVAC Systems Page 46 15

16. Selection of HVAC Systems
[Air-and-water systems are more complex than air-only systems but use less energy and will require coordination with additional trades.]
The energy use of an HVAC system varies greatly depending on the type of system used.
Water can carry heat more effectively than air, so water is much better than air for transporting heat. Water also needs less pumping energy and allows more efficient heat exchange for a given heating or cooling load. The smaller mass of water moved compared to the mass of air needed to provide a change in temperature makes air-and-water systems much more energy efficient than air-only systems.
In most green HVAC systems, the only air circulated is for ventilation. All heating and cooling is carried using heated or chilled water.
The capital costs of the air-and-water systems are often higher because of the need to run both piping and duct systems throughout the building. However, these costs can often be justified by the smaller space requirements for these systems. These systems will also require coordination with additional trades.
In air-only systems the amount of cooled air to a space is controlled by the use of dampers. In many cases the recently cooled air is then reheated to match the local load, which is obviously very inefficient.
A more efficient way is to adjust the volume of the air, which is best achieved with a VFD. Reducing the air flow in a system by 50% cuts the energy use by about 87% due to the way air flow and pressure are related to fan power.
Water carries heat more effectively than air
In most green HVAC systems, air is only used for ventilation; all heating and cooling is carried in circulating water
Air-and-water systems are more energy efficient than air-only systems
Often air-only systems are controlled by dampers - it’s more efficient to use a VFD
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Types of HVAC Systems Page 46 16

17. Upgrading HVAC Systems
[Electric resistance heating systems are very inefficient and should be replaced in green retrofits.]
Electric resistance heating systems are popular because they are inexpensive to install; however, they are expensive to operate and very inefficient. Although an electric resistance heating system is 100% efficient in the building, If you recall our discussion about site and source energy in Chapter 1, it is actually only about 30% - 33% efficient taking into account the fuel used in generating the electricity.
Even poor-quality boilers and furnaces operate at 60% efficiency, and high-quality condensing units can do as well as 97%, far better than the 30% - 33% of electric resistance heating.
Most green retrofits seek to reduce the amount of electric heating used by the HVAC systems. In large buildings, green retrofits will also seek to increase the efficiency of packaged air handling units, especially those that use electricity for heating, by replacing them with either more efficient units or centralized systems served by boilers and chillers.
Electric resistance heating is cheap to install but…
Expensive to operate
Inefficient because electricity
is generated from fuel at
30-33% efficiency
Electric Baseboard Heating
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Electrical Work in Upgrading HVAC Systems Page 48 17

18. Electrical Work in HVAC Retrofits
[Upgrading electrical work in HVAC systems gives electricians the opportunity to correct mistakes from original construction.]
A great deal of the electrical work involved in upgrading an existing HVAC system will be standard: running conduits and wire racks, installing relay racks and motors, etc.
On larger jobs there should be a complete set of specifications and drawings. On smaller jobs, the electrician may bear a larger share of the responsibility for getting the job done correctly.
Retrofit jobs should be seen as an opportunity to correct existing mistakes and sloppy work.
Wires should be clearly labeled so time is not wasted testing wire after wire when a small component of a complex system fails.
Ties should be neat and snug, but not so tight as to stress insulation.
Every component should be supported mechanically and completely independently of the wiring, which should never be under stress.
All this is just good practice, but it is not always done.
When today's more sophisticated HVAC systems are installed, the impact of small errors can be expensive to find and correct.
Permanent labels on wiring to simplify troubleshooting in the future
Do not strain wire insulation
Opportunity to correct mistakes from original construction
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Electrical Work in Upgrading HVAC Systems Page 48 18

19. Building Control Systems
[Building control systems regulate MEP systems.]
MEP systems provide a properly functioning building, resulting in a comfortable working and living environment.
Control systems can be as simple as a single-zone thermostat on a home heating system or complex systems supported by banks of computers in large buildings with several to hundreds of sensors detecting temperatures, flow velocities, humidity, control set points, and many other system characteristics.
As these systems become increasingly sophisticated, they are able to maintain comfortable indoor environments while using increasingly less electric power and fuel.
Control systems used to manage the operation of equipment in buildings, including HVAC systems, use direct digital control (DDC) and go by multiple names, the most common is building management systems (BMS).
Substantial energy reductions are achieved using these systems by closely matching the output of equipment to the actual loads rather than running equipment at full power and wastefully discarding unneeded thermal energy and pumping power.
Building control systems monitor and control the MEP systems in a building.
The most common are building management systems (BMS).
Control systems
Temperature sensors
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Building Control Systems Pages 48-50 19

20. Building Management System (BMS)
[A BMS reduces energy use in a building by more closely matching demand and output for MEP systems, so all sensors need to be correctly installed and tested.]
A BMS only operates as planned if all of the multitude of sensor wires are correctly connected at both ends. If the signal being reported as the hot water temperature is actually the stack temperature, it will be impossible even for the most elegant control system to keep the building temperatures within prescribed limits.
Every electrician knows that if a power wire is connected incorrectly, there will be circuit breakers tripping or sparks and smoke. However, if a sensor wire is misconnected, it can take weeks to discover the malfunction and trace the problem. Although tedious, getting each and every wire right is the largest single contribution electricians can make to green (or any other) projects.
The more fully electricians understand the functions of the systems they are installing, the less likely errors and mix- ups will occur compromising system operations and efficiency.
If you feel you are being asked to carry out work with insufficient guidance, don't hesitate to ask for more detailed instructions. It will save everyone time and aggravation in the long run.
A BMS reduces energy use by:
Scheduling equipment and operations to meet demand
Controlling temperature, pressure, and humidity in the building, taking weather conditions into account
Controlling fans and pumps to optimize HVAC
Providing data for analysis
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Types of Building Management and Information Systems Pages 48-49 20

21. CASE STUDY: 31 Tannery Project, Branchburg, NJ
First Net-Zero Building in U.S.
31 Tannery Project: First Net-Zero Building in U.S.
The 26,000 square foot shop area is used for servicing Ferreira Construction's heavy road and highway equipment, as well as fleet of trucks and SUVs.
Doors have to be opened and closed all day which makes it difficult to maintain heating or cooling.
In the boiler room, a 14,000 Btu/h gas-fired, low nitrogen-oxide, full modulation condensing boiler (96% efficient in full condensing mode) serves four main loops. The hot water loops are provided with variable speed and temperature controls.
Issues: Radiant flooring is energy efficient and a comfortable method of heating, but it cannot respond quickly. Trying to increase or decrease heat only a few degrees can take hours instead of minutes.
To resolve this issue Ferreira discovered that lowering the radiant flooring a few degrees below the desired building temperature and using the rooftop units to augment the difference, quick adjustments to the building's temp could be made to satisfy occupants.
Success: After the radiant flooring was used for over a year, Ferreira found that the system worked well and efficiently. The cement slab retains the heat and radiates it upward, so mechanics are comfortable in the shop.
Building control data, automation, and control of energy systems are key to minimal fuel and electrical use in this net-zero energy building.
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31 Tannery Project Page 50

22. 4 Renewable and Distributed Energy Page 51
[Renewable energy and distributed energy are two different sustainable characteristics of energy generation that are often confused, since many energy sources can be either or both.]
Let’s talk about each concept separately and then discuss examples of each. 4
Renewable and
Distributed
Energy
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Page 51

23. Where is the Energy Generated?
[Where energy is generated in relation to where it's used is an important aspect of how sustainable it is. Understand the differences between central and distributed energy generation and why distributed is considered sustainable.]
In central generation, power is generated at one central location and then transmitted substantial distances across an electrical grid to consumers. Distributed generation occurs close to a load.
Large generation stations powered by coal, natural gas, nuclear power or hydropower are all traditional examples of central electrical generation, while wind and PV farms are newer examples.
Distributed generation occurs close to a load, and reduces demand on the grid.
Examples include rooftop photovoltaics, gas-fired cogeneration, and small local wind turbines.
Distributed generation is considered sustainable because of the lower transmission losses and and the reduction of stress on the grid by reducing peak load.
Central vs. Distributed Energy Generation:
Central Generation: Power is generated at one central location and transmitted long distances across a grid to consumers
Distributed Generation: Occurs close to a load:
Lower transmission losses
Lower stress on grid by reducing peak load
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Basic Background: Energy Generation Pages 51-52 23

24. What is the Energy Source?
[Renewable energy comes from a source that will continue to provide the energy essentially forever without depleting any resource. It is naturally replenished.]
Non renewable sources such as fossil fuels are finite and will run out over time. Renewable sources will not be depleted over time and are therefore considered sustainable.
What are some examples?
Solar thermal
Wind farms
Nuclear power is complex, but (for advanced reactors), available fuel is inexhaustible and operation produces almost no CO2. Safety issues may prevent its widespread expansion.
The advantages of renewable energy in today's resource- constrained world are significant:
Very low emissions of CO2, so renewable energy sources contribute very little to climate change.
No particulates or other pollutants released into the air, resulting in improved health for everyone.
Reduced reliance on scarce fossil fuels increases economic and political stability.
Also, if you recall our discussion about site and source energy in Chapter 1, renewable energy sources such as solar and wind have no thermal losses because we aren’t burning anything, so the site energy is almost equal to the source energy.
Nonrenewable vs. Renewable Energy Generation:
Renewable sources will not be depleted over time.
Very little CO2 emissions
Decreased pollution
Reduced reliance on fossil fuels
Site energy almost equal to source energy
Examples:
Solar thermal
Wind farms
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Basic Background: Energy Generation Page 52 24

25. POP QUIZ: GENERATION: ENERGY SOURCE: Renewable or Nonrenewable?
[The answers are in the book in chart 4.2 on page 52. It’s important to understand why a certain fuel source and mode of generation is central/distributed and renewable/nonrenewable.]
GENERATION:
Central or Distributed?
ENERGY SOURCE: Renewable or Nonrenewable?
Imperial Valley Solar Project, CA
Rooftop solar PV array
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Basic Background: Energy Generation Page 52 25

26. POP QUIZ: GENERATION: ENERGY SOURCE: Renewable or Nonrenewable?
[The answers are in the book in chart 4.2 on page 52. It’s important to understand why a certain fuel source and mode of generation is central/distributed and renewable/nonrenewable.]
GENERATION:
Central or Distributed?
ENERGY SOURCE: Renewable or Nonrenewable?
Imperial Valley Solar Project, CA
Rooftop solar PV array
Central Generation /Renewable Energy
Distributed Generation /Renewable Energy
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Basic Background: Energy Generation Page 52 26

27. POP QUIZ: GENERATION: ENERGY SOURCE: Renewable or Nonrenewable?
[The answers are in the book in chart 4.2 on page 52. It’s important to understand why a certain fuel source and mode of generation is central/distributed and renewable/nonrenewable.]
GENERATION:
Central or Distributed?
ENERGY SOURCE: Renewable or Nonrenewable?
Coal-fired power plant, GA
70 kW microturbine - Cogen
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Basic Background: Energy Generation Page 52 27

28. POP QUIZ: GENERATION: ENERGY SOURCE: Renewable or Nonrenewable?
[The answers are in the book in chart 4.2 on page 52. It’s important to understand why a certain fuel source and mode of generation is central/distributed and renewable/nonrenewable.]
GENERATION:
Central or Distributed?
ENERGY SOURCE: Renewable or Nonrenewable?
Coal-fired power plant, GA
70 kW microturbine - Cogen
Central Generation / Nonrenewable energy
Distributed Generation / Nonrenewable energy
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Basic Background: Energy Generation Page 52 28

29. Radial and Networked Systems
[Electric grids come in two configurations: radial and networked systems. Networked systems are more reliable because multiple routes bring power to an affected area but it easier to install a distributed generator on a radial system.]
The U.S. electric utility industry evolved in a world where all power was produced in large, central power stations.
Current grids still follow that model but the rise of distributed generation allows for a new model because now some power is created at smaller, decentralized locations.
In a radial system, the lines branch out from central points like a tree, and power flows out along the branches. If a branch fails, all the customers farther out along the line are cut off until repairs are made. Radial systems are common in the suburbs and rural areas.
In a networked system, the lines are much more interconnected, with the wires arranged more like the webbed strings in a fishnet, and there are multiple ways of getting power to and from any customer.
Networked systems are typical in large cities and are more reliable than radial systems because if one line goes down, there are other routes by which power can be brought to the affected area.
Distributed generators can be added to either type of network. However, it is easier to assure the safety of the installation of a radial system
Radial and Networked Systems
Radial: Power lines branch out
Networked: Power lines interconnected
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Utility Grid Pages 52-53 29

30. Secure Disconnects
[A secure disconnect on a distributed generator protects utility workers attempting to restore power and can save lives.]
The flow of power from distributed generators can be fed back into the grid if it is producing more power than the building needs at that time.
However it can be dangerous if the grid has gone down and the distributed source continues to generate electricity, as the power could electrocute workers attempting to restore power.
For safety reasons, utilities insist that there be a secure disconnect that will open the circuit should the utility grid go down. Even if the building continues to generate power, for example as an emergency feed to elevators and lights, none of it should feed back to the affected grid.
A secure disconnect on a distributed generator protects utility workers attempting to restore power.
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Utility Grid Page 53 30

31. Selling Energy Back to the Grid
[Net metering is when excess distributed energy is sold back to the utility at the same price as the utility sells power to the customer. This incentivizes distributed renewable energy but it doesn’t account for the cost of maintaining the grid.]
Using the electric energy from a building-mounted PV system is worth considerably more in that building than if the energy were sold back to the utility.
Why? Because the generated energy used on the building's side of the electric utility meter lowers consumption and saves the owner the full cost of the electric energy from the utility which includes cost and maintenance of wires, transformers, and all the other components of the grid that the utility requires to deliver power.
The low price paid for power fed back to the grid has led to a demand for net metering. This is a tariff where the utility pays the building owner at the same rate charged by the utility. This is the equivalent to letting the meter run backward when power is flowing to the utility.
Net metering for distributed energy is not cost effective from the utility’s perspective but it is a convenient way to subsidize desirable technologies. To find incentives in your area visit
Net metering
Find incentives at the Database of State Incentives for Renewables and Efficiency (dsireusa.org)
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Utility Grid Page 53 31

32. Standard Energy Generation Wastes Heat
[Standard energy generation wastes heat and is very inefficient.]
When burning a fuel to produce electric or mechanical power, a certain amount of energy is lost as heat.
In conventional power generation systems, the heat produced in the process is lost. As you recall from our discussion about site and source energy, a typical electric power plant loses 67% of it’s fuel input to waste heat.
A typical power plant can lose 67% of its fuel input to waste heat.
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Cogeneration: Combined Heat and Power Page 54 32

33. A CHP system uses waste heat usually lost to the environment.
Cogeneration: Combined Heat & Power (CHP)
[Cogeneration is efficient because in addition to electrical and mechanical power produced, heat is recovered and used for other purposes.]
Cogeneration, also known as “combined heat and power” or CHP, is the process of generating useable heat and electricity in one machine. A typical cogen unit is natural- gas fired and generates electricity and waste heat.
The use of a cogen unit's waste heat not only makes it much more efficient, but it makes it much more cost- effective as well.
We are going to talk about distributed cogen systems in buildings but it can also be used to make central generation plants more efficient.
Where an engine-type generator making electricity alone might be 20% to 40% efficient, a cogen unit will be 60% to 80% efficient or more if the waste heat is used effectively to avoid burning gas for heat elsewhere.
Finding effective uses for the waste heat can often be a challenge. In many multifamily buildings, the only option is the heating of domestic hot water (DHW). Buildings with hot water (hydronic) space heat are good candidates for cogen.
Cogen is nonrenewable because it burns fuel, but it's efficient!
Cogen captures and uses “waste” heat.
A CHP system uses waste heat usually lost to the environment.
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Cogeneration: Combined Heat and Power Page 54 33

34. Sizing a Cogen Unit Must be sized to load.
[The sizing of a cogen unit is critical. The proper way to size a cogen system is to make sure it is running at full capacity all the time, including both electrical and thermal output.]
The first thing to do is to measure the minimum electric load of the building (called the "base load"). This will determine the first estimate of the cogen unit's maximum size.
This is the maximum size because the excess electricity from a cogenerator usually cannot be sold back to the grid profitably because the fuel source is nonrenewable.
Many people ask whether it is possible to sell excess electricity from a cogenerator back into the grid at the cost of power from the grid— so-called net metering.
Generally speaking, the answer is no, largely because cogeneration still uses fossil fuels, and net-metering is usually used to subsidize renewables.
The next step is to determine the building's thermal (hot water) load and compare it to the thermal output of the cogenerator.
The cogenerator should not produce any more thermal energy than can be used, or it will be wasted.
These thermal loads (hot water, heating, and perhaps cooling) can fluctuate dramatically.
The simplest approach is to specify a cogen unit with a thermal output about equal to the building's smallest hot water load (baseload), but this will probably result in a unit much smaller than the size based on electric loads alone.
Installation of storage tanks for hot water can be added to level thermal loads and meet DHW demand beyond the base load. This adds to the cost of the system and increases the space requirements, but allows larger cogenerators to be installed and operate at full capacity.
Must be sized to load.
Don't make energy you can't use!
A cogen system needs to run at full capacity all the time to be cost-effective.
Design it to meet the electric or thermal base load, whichever is SMALLER.
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35. Sizing a Cogen Unit Average Electrical Demand Domestic Hot
[Storage tanks can be installed to match a building’s fluctuating thermal loads.]
For example, in graph on the left, the electric base load is about 100 kW, so a 100 kW generator would seem right.
But a 100 kW cogen unit would be too big for this building. Why? Because, according to the graph on the right, the DHW load is far less than what would be produced by a 100 kW unit.
The graph on the right shows that the base load hot water demand is about 120,000 Btu per hour. The cogenerator should not produce any more thermal energy than that, or it will be wasted.
As you can see, to put out 120,000 Btu/hr of thermal energy, a 16 kW unit would be more appropriate.
However, 16 kW is probably too small to be practical. To make cogeneration work in this building, it would be necessary to find more thermal loads, or to add a storage tank so the bumps seen in the load above could level out, perhaps to utilize the stored heat. This would then call for a 27 kW cogen unit, a more practical size. With storage tanks, the thermal energy would be stored when demand is below the green line, it could then be used when demand is above the green line.
Note to electricians: Many cogens are WAY oversized and it will be useful to have a handle on these concerns.
Average Electrical
Demand
Domestic Hot
Water Consumption
Existing thermal loads of the building would require only 16 kW unit
Actual power
base load is 100 kW
Adding hot water storage tanks increases thermal load to 27 kW
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Sizing a Cogen Unit Pages 55-56 35

36. Economics of Cogen - Retrofit
[When installed as a retrofit, there are many dealbreakers that may affect the practicality and the cost of a cogen installation.]
A location must be found that allows adequate clearance for maintenance.
The location must also be close to connection points for gas, electricity and waste heat
There must be an allowance for combustion products to discharge.
There must be adequate natural gas capacity or a relatively inexpensive way to provide a new gas line.
Possible deal breakers if the following requirements are not met:
The location must allow adequate clearance for maintenance.
The location must also be close to gas, electricity, and waste heat connections.
There must be adequate natural gas capacity or a relatively inexpensive way to provide a new gas line.
There must be an allowance for combustion products to discharge.
See cost considerations on page 55 of the manual.
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Sizing a Cogen Unit Pages 55-56 36

37. Can Cogen be Used as a Backup Generator?
[Understand the difference between induction and synchronous generators because only synchronous generators can be used as a backup generator but induction generator are much more common.]
Since the electric generator in a cogen unit is basically no different from other standard generators, many people wonder whether a cogen unit could be used as a backup generator in case of a blackout.
Unfortunately, most systems cannot.
The majority of cogen systems employ an induction generator. This type of generator requires voltage from the utility in order to operate. If the utility goes down, the cogen goes down, too.
Some cogens can be supplied with a synchronous generator or an “inverter-based” generator, neither of which requires utility voltage, which could serve as backup devices.
However, there are a number of utility and code restrictions on the use of such systems, so although they are sometimes installed, it can be difficult and/or expensive to do so.
Induction – NO!
Majority of cogen systems
Requires voltage from utility to operate
If utility down, cogen is down
Synchronous – YES!
Does not require voltage from utility
Many code restrictions
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Sizing a Cogen Unit Page 56 37

38. Types of Cogeneration Systems
[Different types of cogen work for different applications, each with its own characteristics. There is a brief description of each type in the manual but we encourage electricians to get training on the types that you will likely encounter in your work.]
RECIPROCATING ENGINE:
The most common type of cogen unit.
Mature technology.
MICROTURBINE:
Smaller scale turbine engines derived from automotive superchargers.
A relative newcomer to the cogen industry, microturbines continue to increase market share. With far fewer moving parts than a reciprocating engine, they have a large theoretical reliability advantage, but as with any new technology, there have been growing pains.
LARGE-SCALE COGENERATION: Gas turbines for industrial applications.
ENGINE-DRIVEN CHILLERS: Gas engine-driven provides air conditioning and provides heat for domestic hot water.
TRIGENERATION: Produces electricity, heat in winter and cooling in summer.
Refer to your manual for more details on each type of cogen system.
Reciprocating Engine: Most common type of cogen
Microturbine: Smaller-scale, fewer moving parts but new to market
Large-Scale Cogen: Gas turbines (industrial applications only)
Engine-Driven Chillers: Reciprocating engine drives standard cooling compressor
Trigeneration: Produces electricity, heat in winter and cooling in summer
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Cogeneration: Combined Heat and Power Pages 57-58 38

39. Fuel Cells Fuel Cells Page 59
[Fuel cells are a new, very clean technology. The only by-products are electricity, heat and water.]
Like cogen, fuel cells are also a type of distributed energy generation using nonrenewable energy sources.
A fuel cell produces electricity, heat, and water by an electrochemical reaction (not combustion) of hydrogen and oxygen.
If pure hydrogen is used as a fuel, the outputs are DC electricity, heat, and water vapor. For most fuel cells, fossil fuels such as natural gas, biogas, methane, or other hydrogen- rich gases must be converted to hydrogen in a device called a reformer, which emits CO2 and small amounts of other pollutants.
Pure hydrogen fuel cells have a high theoretical efficiency for production of electric power, but available systems convert fuel to electricity at only 40% - 50% efficiency.
However, it is very easy to capture the lost energy as heat, so cogeneration efficiencies can be as high as 85% - 90%.
Installation considerations are similar to other cogeneration packages with respect to wiring, breakers, utility interface etc…
Fuel cells today are not yet cost competitive with more conventional generation or cogen. However, they are very reliable and have very low emissions and have been installed in high-end green buildings. As they become used more widely, prices will drop but will remain high for the foreseeable future.
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Fuel Cells Page 59 39

40. Solar Photovoltaic Power
[Solar PV systems convert sunlight into electricity and are between % efficient, depending on the amount of available solar energy.]
We will provide enough information so that you will understand in general what is happening when you are working on or near a PV installation. We encourage you to take additional courses about solar installation.
Photovoltaic (PV) systems are gaining rapidly in popularity, both on a small (building) scale and in large (utility scale) installations. This is a mature industry with well-developed standards, and we cannot possibly fit a complete description of these technologies and standards into this introductory course.
PV systems use the photovoltaic effect to convert sunlight into electricity through the use of semi-conductor materials like silicon.
The maximum efficiency from solar energy to electric energy is about 50%, but practical efficiencies are closer to %, depending on cell materials, construction, and operation.
The power available from PV cells will also depend on the solar energy available (insolation), which will in turn depend on location, cell orientation, and shading of the cells.
Each 6“x 6” PV cell produces about 3 W at 0.6V DC when aligned perpendicularly to full sunlight. To make this electrical power useful, cells are connected and mounted in larger modules, usually called solar panels, containing between 36 and 216 PV cells. The cells are connected in series, a typical panel might have an output voltage of about V DC.
PV systems convert sunlight into electricity via photovoltaic effect
PV effect occurs in semiconductor materials like silicon
Practical efficiencies between 8% and 20%
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Solar Photovoltaic Power Page 60 40

41. Connections of PV Cells
[The method of connection determines the amount of current and voltage produced.]
The electrical connections between the cells are all made within the panel. Typically, strings of 36 or 72 cells are connected in a series, with larger panels connecting two or more cell strings in parallel.
A connection in parallel means that the current will be high but the voltage will be low. Connection in series means that the current will be low but the voltage will be high. Each connection type has different consequences in case of shading or panel loss.
In a string of cells connected in a series, the current is the same in all cells but the voltage is additive. For parallel connections, the current is additive but the voltage stays the same.
Most commercially produced panels bring the cell strings to a termination point in a junction box mounted on the back of the panel. Alternative connection designs may be used, especially for glass panels, where appearance is important.
Parallel
High current
Low voltage
Series
Low current
High voltage
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Electrical Generation and PV Systems Page 61 41

42. PV Performance
[How a module is connected changes how effectively it operates.]
A typical PV cell or panel will generate the highest voltage when no current is being drawn. This is called the “open circuit voltage." Because there is no current, no power is produced (P = I x V).
Conversely, it will produce the largest current when the output terminals are connected to each other through a zero-resistance ammeter. This value is called the “short circuit current." Since the voltage now equals zero, again, no power is produced.
The current and voltage can also be measured at any intermediate connected resistance, and the result is the I-V curve shown here. One point on the shoulder of this curve will provide the maximum power, and this will be the rated power of the panel. The system should be designed so the panel operates near this point as much as possible.
The product of the open circuit voltage and the short circuit current does not correspond to a power that can be obtained from the module, and don't let a salesman tell you otherwise!
All these quantities are measured at 77°F, with full sunlight. If less sunlight is available, less power will be available from the module.
In addition, most panels operate considerably hotter than 77° F, as they absorb a lot of heat from the sun, and this reduces their efficiency below the rated value.
I-V Curves for a PV module at different levels of insolation. Power output is zero when V = 0 or I = 0, maximum on the shoulder of the curve.
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Solar Photovoltaic Power Pages 61-62 42

43. Storing Solar Power Stand-alone PV system with battery storage.
[Excess power from photovoltaic systems can be stored in batteries when there is no grid connection.]
PV panels produce electricity only when there is sunlight, and this may not coincide with the time that the building needs power.
A stand-alone PV system that is not connected to the grid would use batteries to store power until it is needed.
Stand-alone PV system with battery storage.
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PV Performance Page 62 43

44. Storing Solar Power PV wiring with AC conversion for grid connection.
[With a grid-connected system, if the system doesn’t generate enough power, remaining loads are met from the grid. If there is excess power at times of high insolation, that power can be fed back into the grid.]
The more commonly designed system is connected to the grid and uses an inverter to convert the DC power to AC and uses it to meet building loads.
We will focus here on grid-connected systems, since they are far more common than stand alone battery storage systems.
PV wiring with AC conversion for grid connection.
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PV Performance Page 62 44

45. Additional Components of PV Systems
[The power generated in a PV cell is DC, but the power used in most buildings is AC. This means that the panels have to be connected to an inverter to convert the DC power to AC power.]
Conversion of power from DC to AC can occur at the panel, for a collection of panels, or for an entire system.
There are advantages and disadvantages of providing inverters at each scale, based on cost, complexity of wiring, and output. In general, it is most energy efficient to connect PV modules that have similar solar exposure, including orientation, shading, and size.
An inverter can be provided for each of these subarrays.PV modules within each subarray may be connected in parallel or in series.
Special solar inverters are used to convert DC power to AC power. These incorporate a controller that controls the conversion from DC to AC and also maximizes the power output using a maximum power point tracking (MPPT) algorithm. This algorithm adjusts the impedance seen by the module so it is always operating close to the maximum power point described earlier.
The wiring for these systems is straightforward once the different components are understood. DC wiring at 24 V to 48 V DC connects the modules to each other and to the controller/inverter, and standard wiring gauge requirements for the expected current must be followed.
Remember, these are different from AC wire gauge requirements!
DC to AC Conversion:
PV cells provide DC power
Building systems are AC
Inverter converts DC power to AC power
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Solar Photovoltaic Power Pages 62-63 45

46. Inverters Outdoor connection requires: Protection from corrosion
[Practical considerations for inverters installation include weatherproofing, thermal expansion and eventual maintenance.]
The connections to the modules are outdoors and must be protected from corrosion and be sufficiently slack to allow for thermal expansion and contraction. The connections should also allow for the removal and replacement of modules as failure is possible. It should also be possible to disconnect a broken module until it is replaced while leaving the array functioning.
The inverter creates AC power that can be connected directly to the building systems using standard wiring, but the presence of a power source within the building means that a secure disconnect will be required to ensure that power cannot be fed back onto the utility lines in the event of a failure of the utility grid.
Outdoor connection requires:
Protection from corrosion
Sufficient slack to allow for thermal expansion and contraction
Allowance for the removal and replacement of modules
DC to AC PV system string inverter
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Additional Components of PV Systems Pages 62-63 46

47. Building-Mounted Systems
[It is important that PV panels be installed at the proper orientation and angular placement with no shading.]
PV modules produce the most power when the sun falls directly perpendicular to the module face. Any other angle decreases its effectiveness.
For building-mounted PV systems, the optimum orientation for a solar panel facing directly toward the equator (south in the northern hemisphere) at an angle to the horizontal slightly shallower than the angle of latitude. Latitude is the angular distance measured from the Earth's equator.
This angle provides optimal output when totaled over a year but panels are are often angled more horizontally to take advantage of the longer hours of daylight in the summer.
If a panel is partially shaded, the output of the whole cell string or module is lost, and the output from other parts of the array may be reduced, depending on the wiring arrangement. Avoid placing panels in shade whenever possible.
For roof arrays, panels need to be placed far enough apart in the north-south direction so that they do not overshadow one another. In some configurations the effect of mutual shadowing is enough that the maximum output from a whole roof may be achieved with panels lying flat and next to each other rather than elevated at an angle, but spaced further apart.
Maximize on-building systems:
Orientation: Perpendicular to the sun, facing south at an angle to the horizontal, slightly shallower than the angle of latitude
Shading: Avoid shading! Reduces output of whole cell string
Placement: Avoid overshadowing
Roof mounted PV system
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Types of PV Systems Page 63 47

48. Large-Scale Systems Types of PV Systems Pages 63-64
[Large scale solar systems are far more feasible in the Southwestern areas of the U.S. where insolation is highest.]
Insolation: the amount of radiating power from the sun on a given surface.
A PV module in Albuquerque, N.M., will produce about 70% more energy in a year than the same panel would in New York City, due to the much greater solar availability.
This figure shows available solar energy across the U.S. The availability of so much sunshine makes it practical to setup solar power plants selling to the utilities at so-called “busbar” prices (the cost to utilities of producing electricity.)
As more restrictions on carbon emissions are imposed, we can expect busbar prices to rise and solar power plants to become increasingly viable.
However, because they have little to do with buildings directly, we will not discuss them further here.
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Types of PV Systems Pages 63-64 48

49. New PV Technologies are Reducing Costs
[New PV technologies are becoming less expensive.]
There is a continuous drive to increase the efficiency of PV cells and to reduce their price. Cost per watt has dropped on average, from $11/W in 1998 to $6/W in
Amorphous thin film technologies have lower efficiency but may provide lower overall cost
Higher-efficiency cells such as the HIT PV cell which is a hybrid of a thin-film and a crystalline cell may also lead to lower cost PV.
As you can see on this chart, over the last decade, the installed cost-per-watt for PV modules has been falling steadily.
Solar panels are expensive and installations are frequently partially funded through subsidies. There is currently a 30% federal tax credit for residential PV installations and for other renewable technologies. There are also many state incentives and subsidies, which can be found at
Amorphous thin film technologies have lower efficiency but may provide lower overall cost
HIT PV cell development may also lead to lower PV cost
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Solar Photovoltaic Power Page 64 49

50. Simple Payback Analysis
[A simple payback analysis shows you how many years it will take to recoup the investment through lower annual utility costs.]
The actual capital investment of $115,000 is the purchase price minus all available incentives and tax credits.
This installation is expected to result in savings of $15,000 per year as a result of decreased electric bills
Dividing savings into the actual capital investment shows a simple payback period of 8 years.
That is, after 8 years, the investor will have recovered the initial investment, and sees a pure savings of $15,000 per year from then until the system's end of life, which is expected to be between 20 and 25 years for current systems.
Note: this is just a sample, numbers may not be accurate.
50 kW rooftop solar PV system
Analysis Categories
Cost
PV panel cost with installation
$300,000
Federal tax credit (one-time)
- $90,000
State energy program incentive
- $95,000
Net invested capital
= $115,000
Anticipated operated savings/year
+ $15,000
Payback period
$115,000 / $15,000 =
8 YEARS
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New PV Technology Page 64 50

51. PV Installer Certification
[Certifications for installers are becoming more prevalent in the photovoltaic industry.]
On the national level two organizations prevail:
North American Board of Certified Energy Practitioners (NABCEP).
Underwriters Laboratory (UL)
Regional certifications usually refer to state licensing regulations. Some states also require installed systems to be audited for code compliance and estimated production before an individual or contractor will be listed as an approved PV installer.
Some manufacturers of photovoltaic equipment offer certifications for installation of their products which may be required for service work or may open up different pricing structures not available to those without the training.
Even without legal or contractual requirements, certification may be worth pursuing. Increasingly, training has become an important way to distinguish oneself in a highly competitive market.
National certification:
Underwriters Laboratory
Regional Certification
Manufacturer Certification
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Solar Photovoltaic Power Page 65 51

52. Wind Power: Utility-Scale
[Wind power is a great sustainable solution for central energy generation in remote areas with high wind speeds]
Wind power is emerging as one of fastest-growing sources of electric power in the U.S., with new “farms” of turbines being announced weekly in the Great Plains, the Adirondacks, and off-shore.
This is encouraging from a sustainability point of view, because wind power reduces the need for fossil fuel and nuclear plants to provide us the power we need.
The basic operation of a wind turbine is straightforward — the wind blows through a “turbine,” which is basically a large set of blades that look like the propeller of an airplane, and force it to turn. This rotational motion is passed on to an alternator, which produces the electric power. Most large systems have three blades, which will be 150 to 300 feet long (1 football field!) for a 1.5 to 3.0 MW turbine.
When properly designed and operated, wind turbines can extract up to 50 percent of the power present in the wind they intercept.
The power present in wind varies with the cube of the wind speed. This means that if the wind speed is doubled, the available power is 8 times greater.
So if you are going to pay substantial money for a wind generator, it only makes sense to put it where the wind velocities are highest.
Since this is a course for electricians who work in buildings, rather than utilities, we won’t cover wind technology in detail.
Effectiveness depends on wind speed and consistency.
Off-shore wind farms
Mountain ranges
Great Plains
Wind farm near Tehachapi, CA
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53. Wind Power: Building-Mounted Systems
[Wind energy is not a good solution for cities because wind patterns are not consistent enough to produce enough energy and building-mounted turbines cause structural stresses which makes installation difficult.]
Wind turbines are substantially less cost-effective in cities. Even though the wind on top of buildings is higher than at street level, it is much less consistent because the terrain is so much choppier
Wind turbines cause structural stresses on buildings – this is less of a problem in new buildings where the structural design can accommodate them but sometimes this can be a dealbreaker in existing buildings.
The usual utility interconnection issues will apply, including the need for an automatic disconnect in the event of utility grid failure, but the treatment will be the same as for any small, distributed generation system.
Concerns:
Not cost-effective
Less consistent
Stresses to existing building
Machine failure in densely populated environments
Brooklyn Navy Yard, Brooklyn, NY
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54. Tidal Turbines Harvest energy in the tides. Tidal Turbines Page 68
[Tidal turbines are a good additional source of renewable power.]
The tides, ultimately powered by the gravitational pull of the moon, contain enormous amounts of power which is, unfortunately, hard to extract.
A small tidal dam, which traps high tide and extracts power as it runs out, has been operational at the 20 MW level at the Bay of Fundy in Canada for years, and there are now proposals for a much larger system to trap more of the bay's waters.
Large turbines are immersed in the water and as the tides flow in and out, blades force a generator to turn and produce power much as a wind turbine does.
This system shown here has been successfully demonstrated and is now being built out to a 30-turbine array with a capacity of 1.0 MW.
For the electrician who is actually working on the project, it is simply another source of AC power, and requires no special skills or knowledge but will require special coordination issues for installation.
Harvest energy in the tides.
East River Turbine, RITE Project, New York, NY
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55. Electric Vehicle Charging Systems
[Charging stations for electric vehicles are becoming more common and electricians can take additional courses to learn detailed installation techniques.]
While electric vehicles aren't a form of energy generation, they do involve a new technology that electricians working in buildings are coming into contact with more and more.
Electric vehicles have many advantages over conventional internal combustion vehicles: drastic reduction of air pollution, reduced greenhouse emissions, and less reliance on oil.
The 3 levels of electric vehicle charging have different voltage and amperage requirements
Currently Levels 1 and 2 are available. Level 1 uses a typical residential 120 volt single phase outlet but charge time can take up to 15 hours. Level 2 using 208/240 volts can charge a car 4 to 5 times faster and is expected to be widely used in commercial and residential settings as the charge times are more manageable.
Level 3, still under development, will provide DC power at the plug, since the large rectifier and associated cooling would not fit easily inside the vehicle.
It is important for electricians to keep up to date with this technology as it develops. There are many new training opportunities for certification in these technologies and we encourage GPRO students to take advantage of them.
Electric vehicles are cleaner to run than internal combustion vehicles.
As they become more common, electricians will find more opportunities in EVSE (Electric Vehicle Service Equipment).
Electric vehicle charging system, Syracuse, NY
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56. CLASSROOM EXERCISE #2 BASIC PV DESIGN
NOTE: THIS CAN BE GIVEN FOR HOMEWORK.
1. What size array can be installed? How many panels can be included and what is the total area?
Assume panels can touch. There are two ways to lay the panels out, as seen below:
Choose A:28 panels, 28x39x65/144 = 493 sf.
2. If the peak power available at this roof angle is 93 W/sf, what is the peak output of the array?
P=493 sf x 93 W/sf x 0.12 = 5,500 W = 5.5 kW
(0.12 = 12% efficiency)
3. What is the total installation cost? The cost after incentives?
Cost =$6/W x 5,500 W = $33,000 installation cost
Cost after incentives =
$33,000
- (0.3 x $33,000 = $11,000) = $22,000
- (.25 x $22,000 = $5,500) = $16,500
Payback is shorter after incentives.
A homeowner is considering installing PV panels on an existing roof. See details on page 70.
What size array can be installed? How many panels can be included and what is the total area?
If the peak power available at this roof angle is 93 W/sf, what is the peak output of the array?
What is the total installation cost? The cost after incentives?
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57. CLASSROOM EXERCISE #2 BASIC PV DESIGN
Using the map on the next page, how much energy do the PV panels produce in a year?
[For NYC] the light green = 0.42 kwh/sf/day, so Energy = 0.42 kwh/sf-day x 493 sf x 365 days = 75,580 kwh.
Your answer will vary depending on which region you choose.
5. How much is saved in energy costs per year?
Annual savings = 75,580 kwh x $0.20/kwh = $15,116/year
[Note to instructor: this is a high annual cost of electricity, most regions of U.S. are lower.]
6. How long is the payback period? (See Figure 4.20 in manual for Simple Payback Analysis)
Cost/savings = $16,500 / $15,116 = 1.1 years
[Note to instructor: this is an extremely low payback period, future editions will show 5-8 year payback.]
7. Give two or three reasons for converting electricity from the PV panels to AC, rather than leaving it as DC and storing the energy in batteries for back-up during power outages. (Compare to using a fuel powered generator during the outage.)
Batteries are only 70-75% efficient
No losses for use and sell-back with the utility, especially if net metering is available.
Batteries are expensive; one would never buy enough to last more than one day.
Storing enough fuel for a generator is easy.
Using the map on the page 71, how much energy do the PV panels produce in a year?
How much is saved in energy costs per year?
How long is the payback period? (See Figure 4.20 in manual for Simple Payback Analysis)
Give two or three reasons for converting electricity from the PV panels to AC, rather than leaving it as DC and storing the energy in batteries for back-up during power outages. (Compare to using a fuel powered generator during the outage.)
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