Zero net energy of commercial building

Net Zero Energy Design of Commercial Buildings

A Research Report submitted to the faculty of

San Francisco State University

In partial fulfillment of

The requirements for

The Degree

Master of Science

In

Engineering: Energy Systems

By

Ruchir Hemant Shah

San Francisco, California

December 2015

i

Copyright by

Ruchir Hemant Shah

2015

ii

CERTIFICATION OF APPROVAL

I certify that I have read Net Energy Design of Commercial Buildings by Ruchir H. Shah, and

that in my opinion this work meets the criteria for approving a research project report submitted

in partial fulfillment of the requirement for the degree Master of Science in Energy Systems at

San Francisco State University.

Ahmad Ganji, Ph.D.

Professor

A. S. (Ed) Cheng, Ph.D.

Professor

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Net Zero Energy Design of Commercial Buildings

Ruchir Hemant Shah

San Francisco, California

2015

The vision of Net Zero Energy Buildings (NZEBs) is compelling. In theory, the amount of

energy consumed by the building for an entire year should be less than or equal to the amount of

energy produced by the onsite renewable source.

The main aim of my project is to build maximum number of floors in the building and make it

zero net site energy using roof-top solar photovoltaic (PV) panels. To check weather effect,

project is simulated in three different weather conditions.

Results obtained from the simulation in this project under the three weather conditions show that

a maximum of two floors can be designed in new energy efficient buildings to make them zero

net site energy using roof mounted solar PV. The simulation results indicate that only one floor

can be built as a net zero source energy building if natural gas consumption converted into

electrical energy consumption. To design more than two floors in new construction or to design

more than one floor in existing building to make net zero energy, we need to use building site for

energy production, in addition to the roof-top.

Analysis methods for design and implementation of NZEBs are also discussed. The discussion is

followed by several ways to achieve large-scale, replicable NZEBs performance. Various passive

and renewable energy strategies are implemented, including full daylighting, high-performance

lighting, natural ventilation, infiltration and thermal mass. Ground source heat pumps have been

used for space conditioning as well domestic water heating.

I certify that the Abstract is a correct representation of the content of this thesis.

Chair, Project Committee Date

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PREFACE AND/OR ACKNOWLEDGEMENTS

I want to thank Professor Ahmad Ganji for his immense support and guidance in the

accomplishment of my project. I would like to thank him further for meeting with me every

week and helping me solve all the doubts and providing detailed solutions. This helped me

developed a lot of insights on NZE and gain conceptual knowledge during the span of this

project. Professor Ganji was extremely helpful and generous throughout the project

development.

I would also like to thank Professor A.S Cheng to be my other committee chair professor for his

assistance. I truly thank professor Cheng to support me during my entire stay at San Francisco

State University.

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TABLE OF CONTENTS

Table of Contents………………………………………………………………………………...V

List of Figures………………………………………………………………………………….VII

List of Tables………………………………………………………………………………….VIII

1. Introduction……………………………………………………………………………………1

1.1. Problem Definition……………………………………………………………………….1

1.2. Project Scope………………………………………………………………………..........1

2. Climate Assessment…………………………………………………………………………....2

3. Energy Efficient Buildings………………………………………………………………….....3

3.1. Passive Design…………………………………………………………………………….4

3.2. Building Envelop………………………………………………………………………….8

3.3. Mechanical Systems………………………………………………………………………10

3.3.1. Traditional System…………………………………………………………………11

3.3.2. Heat Pumps………………………………………………………………………...11

3.4. Domestic Hot Water……………………………………………………………………...16

3.5. Lighting…………………………………………………………………………………..17

4. Renewable Energy…………………………………………………………………………….19

4.1. Solar Electric Generation…………………………………………………………………19

4.2. Solar Water Heating………………………………………………………………………20

5. Plug Loads and Occupancy……………………………………………………………………21

6. Modeling Simulation …………………………………………………………………………22

6.1 Building Specification…………………………………………………………………….22

6.2 Modeling Tool…………………………………………………………………………….23

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6.3 Model Specification……………………………………………………………………….24

6.4. Modeling Results…………………………………………………………………………27

7. Simulation Verification………………………………………………………………………..34

8. Future of Net Zero Energy Building………………………………………………………......35

9. References……………………………………………………………………………………..36

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LIST OF FIGURES

Figures Page

1. Night Purge Ventilation………………………………………………………5

2. Daylighting…………………………………………………………………... 7

3. Natural Ventilation…………………………………………………………... 8

4. Horizontal Closed loop Ground Source Heat pump System………………… 9

5. Vertical Closed loop Ground Source Heat pump System…………………….13

6. Pond/Lake Closed loop Ground Source Heat pump System………………….14

7. Open Loop Ground Source Heat Pump……………………………………… 15

8. Window Technology………………………………………………………….16

9. Commercial Building Use Breakdown……………………………………….21

10. Building Schematic…………………………………………………………..22

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LIST OF TABLES

Table 6-1 Tabular inputs used in eQuest for baseline building, Energy Efficient

techniques and Net Zero Energy for different location………………………...24

Table 6-2 Output of new office building with 50,000 Sqft in Phoenix, AZ for different

floors…………………………………………………………………………….28

Table 6-3 Output of new office building with 100,000 Sqft in Phoenix, AZ for different

floors…………………………………………………………………………….28

Table 6-4 Output of new office building with 50,000 Sqft in San Jose, CA for different

floors…………………………………………………………………………….28

Table 6-5 Output of new office building with 100,000 Sqft in San Jose, CA for different

floors…………………………………………………………………………….28

Table 6-6 Output of new office building with 50,000 Sqft in Chicago, IL for different

floors…………………………………………………………………………….29

Table 6-7 Output of new office building with 100,000 Sqft in Chicago, IL for different

floors…………………………………………………………………………….29

Table 6-8 Output of conventional office building with 100,000 Sqft in San Jose, CA for

different floors…………………………………………………………………..30

Table 6-9 Output of conventional office building with 100,000 Sqft in Phoenix, AZ for

different floors……………………………………………………………………30

Table 6-10 Output of conventional office building with 100,000 Sqft in Chicago, IL for

different floors…………………………………………………………………...31

Table 6-11 Comparison between new and existing building parameters for Phoenix, AZ with


Table 6-12 Comparison between new and existing building parameters for San Jose, CA with


Table 6-13 Comparison between new and existing building parameters for Chicago, IL with


Table 6-14 Comparison between RSF building real data and my simulation output………...35

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1. Introduction

Buildings have a significant impact on energy use and the environment. Commercial and

residential buildings use almost 40% of the primary energy in the United State (EIA 2005). The

energy used by the building sector continues to increase, primarily because new buildings are

constructed faster than existing ones are retired. Electricity consumption in the commercial

building sector doubled between 1980 and 2000 and is expected to increase another 50% by

2025 (EIA 2005). To address the growing energy use in the commercial building sector, an

influential community of industry leaders and researchers has committed to pushing the

boundaries of building performance to develop net-zero energy buildings (NZEBs).

Big bold goals adopted by California Public Utilities Commission (CPUC) in 2007-08 was, all

new residential construction in California will be zero net energy by 2020. All new commercial

construction in California will be zero net energy by 2030 (CPUC 2008).

1.1 Problem Definition

At its core, the amount of energy consumed by building for entire year should be less than or

equal to amount of energy produce by onsite renewable energy sources. The National Renewable

Energy Laboratory (NREL) has defined four ways of measuring and defining net zero energy for

buildings; net zero site energy, net zero source energy, net zero energy emissions, net zero

energy cost.

Net Zero Site Energy building produces at least as much renewable energy as it uses over the

course of the year when accounted for the site (Torcellini 2006)

Net Zero Source Energy building produces or purchases at least as much renewable energy as it

uses over the course of a year when accounted for at the energy source (Torcellini 2006).

Net Zero Energy Emission building produces or purchases enough emission-free renewable

energy to offset emissions from all energy used in the building over the course of a year

(Torcellini 2006).

Net Zero Cost Building receives at least as much financial credit for exported renewable energy

as it is charged for energy and energy services by the utility over the course of the year

(Torcellini 2006).

From the above definitions, the modeling simulation in this report is based on net zero site

energy using roof mounted solar PV.

1.2 Project Scope

The project is carried out to determine how many floors can be built in an energy efficient

commercial building to make it a net zero site energy building with roof-top PV system as the

energy source. The results are verified in different climates for all the buildings compliant with

current standards. Two office buildings are taken into consideration each having 50,000 Sqft and

100,000 Sqft areas with maximum number of floors viable. The modelling is carried out in given

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climatic conditions for the cities of San Jose, CA, Chicago, IL and Phoenix, AZ. The modeling

simulation is developed using a ground source heat pump for heating and cooling source .Several

passive architecture energy efficient techniques such as daylighting, energy efficient building

envelope, lighting controls and natural ventilation are applied. In modeling of conventional

buildings, CA Title 24 and ASHRAE 90.1 standards are utilized to check net zero energy

possibilities. The results are compared with a new building to show the effects of energy efficient

techniques.

2. Climate Assessment

Climate is critical variable in the design of a net zero energy project. It influences external

thermal loads of a project and it is also a free source of energy. Simply we can say that net zero

energy project must be climate responsive. Climate classes are:

A. Tropical

B. Arid

C. Temperate

D. Cold

E. Polar

A. Tropical

Tropical climates are characterized by yearlong hot and moist weather with rainfall and

humidity. Example location: Miami, FL

Design Response:

• Reduce cooling load with passive strategies, such as minimizing solar radiation, reduce

thermal conduction, reducing internal heat gain.

• Daylight lowers lighting load and internal heat gain. Natural Ventilation is useful for

some tropical climates.

• Light colors for exterior surface will reflect rather than absorbs solar radiation.

B. Arid

Characterized by lack of precipitation. Can be hot or cold. Example locations: Nevada, Arizona,

New Mexico.

Design response:

• Hot climates are cooling dominated and cold climates are heating dominated.

• Night purge ventilation can also be effective for moderate cooling.

• Provide natural ventilation and solar shading during cooling season.

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C. Temperate

Characterized by warm summer and cool winter. Example location: California

Design response:


• Night purge ventilation can also be effective for moderate cooling.


D. Cold

Characterized by cold winter with snow. Example location: Rochester, NY

Design response:

• Reduce heat transfer through conduction with well insulated building envelop



E. Polar

Extremely cold weather often with no summer season and typically treeless. No Human

population. Example location: Arctic

The simulation is performed for Phoenix, AZ as arid, San Jose, CA as temperate and Chicago, IL

as cool and humid.

3. Energy Efficient Buildings

Energy efficient buildings are the ones that use a minimum amount of energy throughout the

year. To achieve energy efficiency, passive and active architecture strategies play vital roles.

Passive architecture includes, daylighting, natural ventilation, air tightness of the building, and

efficient building envelopes. Active architecture contains mechanical systems in the building like

Heating Ventilation Air Conditioning (HVAC) and Domestic Hot Water (DHW). This section

will provide a brief introduction of passive and active architectures, lighting systems in the

building and their roles in energy efficient buildings.

3.1 Passive Design

Passive design is defined as the use of architecture and climate to provide heating, cooling,

ventilation and lighting. In other words technique which does not require any active systems. It is

one of the most important parameters to a get free source of energy in net zero energy building

for heating and cooling. However, we cannot rely totally on passive design to provide heating

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and cooling so we still need active systems in the building, but the main aim is to minimize the

use of active system’s usage (Hootman 2012).

Passive Strategies Types

This section includes different passive strategy types like, thermal mass, night purge, super

insulation, air tightness, daylighting, and daylighting.

Thermal Mass: In building design, thermal mass is a property of the mass of a building which

enables it to store heat, providing "inertia" against temperature fluctuations. Thermal mass will

absorb thermal energy when the surroundings are higher in temperature than the mass, and give

thermal energy back when the surroundings are cooler, without reaching thermal equilibrium.

Ideal materials for thermal mass are those materials that have:

• High specific heat capacity,

• High density

Any solid, liquid, or gas that has mass will have some thermal mass. A common misconception

is that only concrete or earth soil has thermal mass; even air has thermal mass (Hootman 2012).

Night Purge: Night-Purge Ventilation (or "night flushing") keeps windows and other passive

ventilation openings closed during the day, but open at night to flush warm air out of the building

and cool thermal mass for the next day. Night-purge ventilation is useful when daytime air

temperatures are so high that bringing unconditioned air into the building would not cool people

down, but where night time air is cool or cold. This strategy can provide passive ventilation in

weather that might normally be considered too hot for it (Hootman 2012). Night flushing works

by opening up pathways for wind ventilation and stack ventilation throughout the night, to cool

down the thermal mass in a building by convection. Early in the morning, the building is closed

and kept sealed throughout the day to prevent warm outside air from entering. During the day,

the cool mass absorbs heat from occupants and other internal loads. This is done largely by

radiation, but convection and conduction also play roles (Hootman 2012). Figure 1 will give

more idea about night purge ventilation.

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Figure 1. Night Purge Ventilation

Superinsulation: Superinsulation is an approach to building design, construction, and

retrofitting that dramatically reduces heat loss (and gain) by using much higher levels of

insulation and air tightness than normal. Superinsulation is one of the ancestors of the passive

house approach (Hootman 2012).

It is possible and increasingly desirable, to retrofit superinsulation to existing houses or

buildings. The easiest way is often to add layers of continuous rigid exterior insulation and

sometimes by building new exterior walls that allow more space for insulation. A vapor

barrier can be installed on the outside of the original framing but may not be needed. An

improved continuous air barrier is almost always worth adding, as conventional homes tend to be

leaky, and such an air barrier can be important for energy savings and durability (Hootman

2012).

Air Tightness: can be defined as the resistance to inward or outward air leakage through

unintentional leakage points or areas in the building envelope. This air leakage is driven by

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differential pressures across the building envelope due to the combined effects of the stack,

external wind and mechanical ventilation systems.

Air tightness is the fundamental building property that impacts infiltration. An airtight building

has several positive impacts when combined with an appropriate ventilation system (whether

natural, mechanical, or hybrid) (Hootman 2012).

Daylighting: Daylighting is the controlled admission of direct and diffuse Sunlight into a

building to reduce electric lighting and saving energy. A key feature of energy efficient

commercial building design is maximizing the use of natural daylight to supplant electric

lighting in interior spaces. Natural light entering through windows and skylights is not only free,

but can also provide occupants with a feeling of connection to the outdoors. Moreover, when

properly designed to minimize direct beam penetration, the use of natural daylight provides the

most light for the least amount of internal heat gain an important quality given that even in

northern climates mechanical cooling of interior spaces is often needed for much of the year. The

dynamism of daylight provides visual and thermal comfort, but is also central to the regulation of

human circadian rhythms. Daylight enhances our mood and focus, improves immune system

function, and can even suppress drowsiness (Hootman 2012). Figure 2 will show office room

with daylighting.

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Figure 2. Daylighting

Natural Ventilation: Natural ventilation is the process of supplying air to and removing air from

an indoor space without using mechanical systems. It refers to the flow of external air to an

indoor space as a result of pressure differences arising from natural forces. There are two types

of natural ventilation occurring in buildings: wind driven ventilation and buoyancy-driven

ventilation. Wind driven ventilation arises from the different pressures created by wind around a

building or structure, and openings being formed at the perimeter which then permit flow

through the building. Buoyancy-driven ventilation occurs as a result of the directional buoyancy

force that results from temperature differences between the interior and exterior. Since the

internal heat gains which create temperature differences between the interior and exterior are

created by natural processes including the heat from people, and wind effects are variable,

naturally ventilated buildings are sometimes called "breathing buildings" (Hootman 2012).

Figure 3 will give more idea about building with natural ventilation.

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Figure 3. Natural Ventilation

3.2 Building Envelop

Building envelop plays a massive role in the implementation of passive strategies, and so should

be integrated with mechanical and electrical design. The building envelop is a critical element in

the energy performance of any building, but it is absolutely vital for the performance of net zero

buildings. This section will describe important element involved in building envelop and their

effects in energy performance.

Walls: Energy efficient walls are built to minimize heat transfer. The R value, the measure of a

material’s ability to stop the flow of heat is used to compare building material. The higher the R

value greater the material will protect against energy loss. The total R value of wall takes into

consideration all products from which wall is made. Insulation also plays an important role for

energy efficient building.

Thermally massive material have high density and a high specific heat capacity. Material such

as, concrete, stone, masonry and water have the capability to store heat and release heat back into

the environment once the ambient temperature cools. One of the primary benefits of thermal

mass is its capability to even out temperature swings in the interior environment. Thermal mass

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can also be used on the exterior envelop in the hot climate as a means of showing down

temperature swings through the envelope (Hootman 2012).

Windows: When selecting windows for energy efficiency, it's important to first consider

their energy performance ratings in relation to climate and building design. A window's energy

efficiency is dependent upon all of its components. Frames conduct heat, contributing to a

window's overall energy efficiency, particularly its U-factor. Glazing or glass technologies have

become very sophisticated, and designers often specify different types of glazing or glass for

different windows, based on orientation, climate and building design (Haglund 2012). Figure 4

will give details of energy efficient window technology.

Figure 4 Window Technology

Another important consideration is how the windows operate, because some operating types

have lower air leakage rates than others, which will improve energy efficiency.

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Single glazing is a very poor insulator, with an R-value of about 1 (equivalent to U-1). Increasing

the number of panes in a window improves the insulating value of the window, so clear double

glazing has an R-value of about 2 (equivalent to U-0.5), and clear triple glazing has an R-value

of about 3 (equivalent to U-0.33). The values for double or triple glazing can be further improved

by including one or two low-e coatings and an inert gas fill between the panes. The best double-

glazed windows have a whole-window U-factor of about 0.27, while the best triple-glazed

windows which are used in present simulation have a whole-window U-factor of about 0.17

(Haglund 2012).

Infiltration: Infiltration is the unintentional or accidental introduction of outside air into a

building, typically through cracks in the building envelope and through use of doors for passage.

Infiltration is sometimes called air leakage. The leakage of room air out of a building,

intentionally or not, is called exfiltration. Infiltration is caused by wind, negative pressurization

of the building, and by air buoyancy forces known commonly as the stack effect (Athienitis

2006).

Because infiltration is uncontrolled, and admits unconditioned air, it is generally considered

undesirable except for ventilation air purposes. Typically, infiltration is minimized to reduce

dust, to increase thermal comfort, and to decrease energy consumption. For all buildings,

infiltration can be reduced via sealing cracks in a building's envelope, and for new construction

or major renovations, by installing continuous air retarders. In buildings where forced ventilation

is provided, their HVAC designers typically choose to slightly pressurize the buildings by

admitting more outside air than exhausting so that infiltration is dramatically reduced (Athienitis

2006).

Reduced air infiltration combined with proper ventilation cannot only reduce energy bills, but it

can also improve the quality of indoor air. Outdoor air that leaks indoor makes it difficult to

maintain comfort and energy efficiency. As per Department of Energy (DOE) air leakage

accounts for 25–40% of the energy used for heating and cooling in a typical building (Athienitis

2006).

3.3 Mechanical Systems

The design of energy efficient building systems or mechanical systems for a net zero energy

project is depends upon the passive architecture of the building. For most commercial building

types, we cannot expect climate responsive architecture with passive strategies to meet all the

desired interior function of the light, comfort, air quality and hot water all the time. Mechanical

systems required to provide these functions when passive strategies alone are insufficient

(Collyer 2012). This section includes a brief discussion of mechanical systems in conventional

and new construction buildings.

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3.3.1 Conventional Mechanical Systems

For heating in conventional buildings boilers are used to generate steam or hot water and can be

fired by natural gas, fuel oil, or coal. Their combustion efficiencies varies from 78% to 86%.

Furnaces can be used for residential and small commercial heating systems. Furnaces use natural

gas, fuel oil, and electricity for the heat source. Natural gas furnaces are available in condensing

and non-condensing models (Graham 2014).

In large commercial and institutional buildings, devices used to produce cool water are called

chillers. The water is pumped to air handling units to cool the air. They use either mechanical

refrigeration processes or absorption processes. Mechanical refrigeration chillers may have one

or more compressors. These compressors can be powered by electric motors, fossil fuel engines,

or turbines. Absorption chillers are heat-operated devices that produce chilled water via an

absorption cycle. Absorption chillers can be direct-fired, using natural gas or fuel oil, or indirect-

fired. Large and medium-sized air-cooled electric chillers have 0.95-0.85 kW/ton (COP of 3.7 to

4.1) (Graham 2014).

3.3.2 Heat Pumps

For climates with moderate heating and cooling needs, heat pumps offer an energy-efficient

alternative to furnaces and air conditioners. Like refrigerators, heat pumps use electricity to

move heat from a cool space to a warm space, making the cool space cooler and the warm space

warmer. During the heating season, heat pumps move heat from the cooler outdoors into the

warmer environment and during the cooling season, heat pumps move heat from cooler

environment into the warm outdoors. Because they move heat rather than generate heat, heat

pumps can provide equivalent space conditioning at as little as one quarter of the cost of

operating conventional heating or cooling appliances (Energy 2008). Classifications and

operations of heat pumps are described in the following sections.

Air Source Heat Pumps

An air-source heat pump can provide efficient heating and cooling for the home. When properly

installed, an air-source heat pump can deliver one-and-a-half to three times more heat energy to a

home than the electrical energy it consumes. This is possible because a heat pump moves heat

rather than converting it from a fuel like combustion heating systems do (Energy 2008).

Air-source heat pumps have been used for many years in nearly all parts of the United States, but

until recently they have not been used in areas that experienced extended periods of subfreezing

temperatures. However, in recent years, air-source heat pump technology has advanced so that it

now offers a real space heating alternative in colder regions (Energy 2008).

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Ground Source Heat Pump

Geothermal heat pumps (GSHPs), sometimes referred to as GeoExchange, earth-coupled,

ground-source, or water-source heat pumps, have been in use since the late 1940s. They use the

constant temperature of the earth as the exchange medium instead of the outside air temperature.

This allows the system to reach fairly high Coefficient of Performance (COP) on the coldest

winter nights, compared to air-source heat pumps on cool days (Energy 2008).

Although many parts of the country experience seasonal temperature extremes -- from burning

heat in the summer to sub-zero cold in the winter. A few feet below the earth's surface the

ground remains at a relatively constant temperature. Depending on latitude, ground temperatures

range from 45°F (7°C) to 75°F (21°C). Like a cave, this ground temperature is warmer than the

air above it during the winter and cooler than the air in the summer. The GSHPs takes advantage

of this by exchanging heat with the earth through a ground heat exchanger (Energy 2008).

As with any heat pump, geothermal and water-source heat pumps are able to heat, cool, and, if so

equipped, supply the building with hot water. Relative to air-source heat pumps, they are quieter,

last longer, need little maintenance, and do not depend on the temperature of the outside air

(Energy 2008).

A dual-source heat pump combines an air-source heat pump with a geothermal heat pump. These

appliances combine the best of both systems. Dual-source heat pumps have higher COP than air-

source units, but are not as efficient as geothermal units. The main advantage of dual-source

systems is that they cost much less to install than a single geothermal unit, and work almost as

well (Energy 2008).

Even though the installation price of a geothermal system can be several times that of an air-

source system of the same heating and cooling capacity, the additional costs are returned as

energy savings in 5 to 10 years. System life is estimated at 25 years for the inside components

and 50+ years for the ground loop. There are approximately 50,000 geothermal heat pumps

installed in the United States each year (Energy 2008).

There are four basic types of ground loop systems. Three of these -- horizontal, vertical, and

pond/lake -- are closed-loop systems. The fourth type of system is the open-loop option. Which

one of these is best depends on the climate, soil conditions, available land, and local installation

costs at the site (Energy 2008). During a given modeling simulation project, closed loop vertical

system is used. All of these approaches can be used for residential and commercial building

applications.

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Ground Loop

Most closed-loop geothermal heat pumps circulate an antifreeze solution through a closed loop

usually made of plastic tubing that is buried in the ground or submerged in water. A heat

exchanger transfers heat between the refrigerant in the heat pump and the antifreeze solution in

the closed loop. The loop can be in a horizontal, vertical, or pond/lake configuration (Energy

2008).

One variant of this approach, called direct exchange, does not use a heat exchanger and instead

pumps the refrigerant through copper tubing that is buried in the ground in a horizontal or

vertical configuration. Direct exchange systems require a larger compressor and work best in

moist soils (sometimes requiring additional irrigation to keep the soil moist), should avoid

installing in soils corrosive to the copper tubing. Because these systems circulate refrigerant

through the ground, local environmental regulations may prohibit their use in some locations

(Energy 2008).

Horizontal Ground Loop

This type of installation is generally more cost-effective for residential installations, particularly

for new construction where sufficient land is available. It requires drains at least four feet deep.

The most common layouts either use two pipes, one buried at six feet, and the other at four feet,

or two pipes placed side-by-side at five feet in the ground in a two-foot wide trench (Energy

2008). Figure 5 will show closed loop horizontal system arrangements.

Figure 5. Horizontal Closed loop Ground Source Heat pump System

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Vertical Ground Loop

Large commercial buildings and schools often use vertical systems because the land area

required for horizontal loops would be prohibitive. Vertical loops are also used where the soil is

too shallow for trenching, and they minimize the disturbance to existing landscaping. For a

vertical system, holes (approximately four inches in diameter) are drilled about 20 feet apart and

100 to 400 feet deep. Into these holes go two pipes that are connected at the bottom with a U-

bend to form a loop. The vertical loops are connected with horizontal pipe (i.e., manifold),

placed in trenches, and connected to the heat pump in the building (Energy 2008). Figure 6 will

show vertical closed loop system arrangements.

Figure 6. Vertical Closed loop Ground Source Heat pump System

Pond/Lake Loop

If the site has a sufficient water body, this may be the lowest cost option. A supply line pipe is

run underground from the building to the water and coiled into circles at least eight feet under

the surface to prevent freezing. The coils should only be placed in a water source that meets

minimum volume, depth, and quality criteria (Energy 2008). Figure 7 will show closed loop

pond/lake arrangements.

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Figure 7. Pond/Lake Closed loop Ground Source Heat pump System

Open loop Systems

This type of system uses well or surface body water as the heat exchange fluid that circulates

directly through the ground heat pump system. Once it has circulated through the system, the

water returns to the ground through the well, a recharge well, or surface discharge. This option is

obviously practical only where there is an adequate supply of relatively clean water, and all local

codes and regulations regarding groundwater discharge are met (Energy 2008). Figure 8 will

show open loop system arrangements.

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Figure 8. Open Loop Ground Source Heat Pump

Hybrid Systems

Hybrid systems using several geothermal resources, or a combination of a geothermal resource

with outdoor air (i.e., a cooling tower), are another technology option. Hybrid approaches are

particularly effective where cooling needs are significantly larger than heating needs. Where

local geology permits, the "standing column well" is another option. In this variation of an open-

loop system, one or more deep vertical wells are drilled. Water is drawn from the bottom of a

standing column and returned to the top. During periods of peak heating and cooling, the system

can bleed a portion of the return water rather than re-injecting it all, causing water inflow to the

column from the surrounding aquifer. The bleed cycle cools the column during heat rejection,

heats it during heat extraction, and reduces the required bore depth (Energy 2008).

3.4 Domestic Hot Water

In conventional commercial buildings hot water is used for space heating and domestic hot

water, and energy consumption for heating the water in commercial building is less as compare

to other facilities like hotels, restaurants. Here ground source heat pump is used to heat water

used for space heating and for domestic hot water.

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Low Energy Hot Water:

The following ideas can save energy used to produce hot water (Hootman 2012).

Minimize water consumption is the best approach to reducing energy use. Installing low flow hot

water fixtures and appliances is good way to reduce the amount of water consumption (Hootman

2012).

Using Heat pump instead of boilers or electric heater. As per research heat pump are more

efficient than boilers and electric heater (Hootman 2012).

In domestic hot water, placing the heater close to the sink by using point of use water heater

(Hootman 2012).

Using a hot water recirculation loop with a close connection of the point of use (Hootman 2012).

Grouping hot water fixtures close to heater locations (Hootman 2012).

3.5 Lighting Systems

Lighting power density (LPD) limits are a major part of all current building energy codes. LPD

sets maximum limit for the installed power over a specified area which is expressed in Watts per

Square Foot (W/ft2). The LPD limit values found in energy codes are typically based on a space-

type lighting model systems consisting currently available lighting product characteristics, light

loss factors, building construction data, and professional design experience. These factors are

used to calculate appropriate values for each building space type (Codes 2012). This Section

includes description of indoor and outdoor lighting controls.

Indoor Lighting Control

Interior lighting is one of the largest electricity energy end-uses in many commercial buildings

and controls can have a significant effect on their energy use. Interior lighting controls give

occupants control over the electric lighting in a space, and can be used to manage building

lighting automatically. Effectively controlling the space lighting results not only in occupant

comfort, but also in energy savings. Efficient lamps and light fixtures reduce the total installed

lighting power whereas controls generally reduce the amount of lighting used or the amount of

time for which lighting is used. Lighting controls can be classified as those required across the

entire building and those that must be applied space by space (Codes 2012).

18

Manual Control

The basic control provided in all spaces is a wall switch that allows occupants to turn general

lighting on and off. This manual control device must be easily accessible and must be located

such that the lights it controls are seen easily from the control location. Manual controls provide

a minimum level of comfort for occupants. Manual control is not required in spaces such as

corridors, stairwells, or other spaces where turning the lights off would be damaging for entry

and security (Codes 2012).

Under ASHRAE Standard 90.1, for spaces smaller than 10,000 Sqft, one manual control device

is required for every 2,500 Sqft. For spaces larger than 10,000 Sqft, one manual control device is

required for every 10,000 Sqft (Codes 2012).

Automatic Shutoff Control

On/off controls and lighting reduction controls are manual controls that are needed in most

spaces. However, these controls rely on occupants to obtain energy savings. There is no

guarantee that these controls will save energy. When occupants are not present in a space and

during the night, there is ample opportunity to turn lights off. Automatic lighting controls are

required to control the lighting during these unoccupied periods. Automatic controls also

guarantee energy savings from lighting (Codes 2012).

Energy codes require that all building spaces be controlled by an automatic control device that

shuts off general lighting. This control device must turn off lights in response to a time-based

operation schedule, occupancy sensors that detect the absence of the occupants, or a signal from

the building’s energy management system or some other system that indicates that the space is

empty (Codes 2012).

In ASHRAE Standard 90.1, the occupant must be able to reduce the lighting power to between

30% and 70% of full power using the manual control device. The International Energy

Conservation Code (IECC) requires this stepped reduction to be lower than or equal to 50% of

full power. Spaces such as corridors, stairways, electrical/mechanical rooms, public lobbies,

restrooms, storage rooms, and sleeping units are exempted. Also exempted are spaces with only

one luminaire with a rated power of less than 100 W and spaces with an LPD allowance of less

than 0.6 W/ft2. The IECC exempts areas within spaces that are controlled either by an occupancy

sensor or by daylighting controls (Codes 2012).

Exterior lighting control

The following controls are required by ASHRAE Standard 90.1.

• Building façade and landscape lighting is required to be shut off between midnight or

business closing, whichever is later, and 6 a.m. or business opening, whichever is earlier.

The façade and landscape lighting at this building must be turned off from 2 a.m. through

6 a.m. (Codes 2012)

19

• All other lighting must be reduced by at least 30% of full power using either occupancy

sensors to turn lights off within 15 minutes of sensing zero occupancy, or from midnight

or one hour from close of business, whichever is later, until 6 a.m. or business opening,

whichever is earlier (Codes 2012).

4. Renewable Energy

Renewable energy is generally defined as energy that comes from resources which are naturally

replenished on a human timescale, such as sunlight, wind, rain, tides, waves, and geothermal

heat. Renewable energy replaces conventional fuels in four distinct areas: electricity generation,

air and water heating/cooling, motor fuels, and rural (off-grid) energy services. To that end, this

topic provides general guidance on planning renewable energy systems for net zero energy

buildings, with focus on early planning and concepts needed to achieve effective integration into

a net zero energy building (Hootman 2012). This topic heavily leans on solar electricity from

photovoltaic systems as an important source of renewable energy for net zero energy buildings

and brief discussion on solar water heating.

4.1 Solar Electric Generation

Solar power is the conversion of sunlight into electricity, either directly using photovoltaics

(PV), or indirectly using Concentrated Solar Power (CSP). Concentrated solar power systems use

lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam.

Photovoltaics convert light into an electric current using the photovoltaic effect (Hootman 2012).

A photovoltaic or PV system, is a powerful system designed to supply usable solar power by

means of photovoltaics. It consists of an arrangement of several components, including solar

panels to absorb and convert sunlight into electricity, a solar inverter to change the electric

current from DC to AC, as well as mounting, cabling and other electrical accessories to set up a

working system. It may also use a solar tracking system to improve the system's overall

performance and include an integrated battery solution, as prices for storage devices are expected

to decline PV systems range from small, rooftop-mounted or building-integrated systems with

capacities from a few to several tens of kilowatts, to large utility-scale power stations of

hundreds of megawatts. Nowadays, most PV systems are grid-connected, while off-grid or stand-

alone systems only account for a small portion of the market (Hootman 2012). Classification of

solar cells briefly describes in following section.

Monocrystalline Solar Cells

This type of solar cell is made from thin wafers of silicon cut from artificially grown crystals.

These cells are created from single crystals grown in isolation, making them the most expensive

of the three varieties (approximately 35% more expensive than equivalent polycrystalline cells),

20

but they have the highest efficiency rating between 15-24% (Hootman 2012). Monocrystalline

Silicon is used in this project.

Polycrystalline Solar Cells

This type of solar cell is also made from thin wafers of silicon cut from artificially grown

crystals, but instead of single crystals, these cells are made from multiple interlocking silicon

crystals grown together, hence they are cheaper to produce, but their efficiency is lower than the

monocrystalline Solar cells, currently at 13-18% (Hootman 2012).

Thin Film Solar Cells

These are the cheapest type of solar cell to produce, are relatively new to market and are

produced very differently to the two other types. Instead of using crystals, Silicon is deposited

very thinly on a backing substrate. There are two real benefits of the amorphous solar cell; firstly

the layer of silicon is so thin it allows the solar cells to be flexible and secondly, they are more

efficient in low light levels (like during winter). This however comes at a price; they have the

lowest efficiency rating of all three types – approximately 7% – 9%, requiring approximately

double the panel area to produce the same output. In addition, as this is a relatively new science,

there is no agreed industry wide production technique, so they are not as robust as the other two

types (Hootman 2012).

Array Sizing and Energy Calculation

There is an online tool which is very user friendly called PV Watts. This tool is supported by the

National Renewable Laboratory (NREL). The calculator estimates the electricity production of a

grid-connected roof- or ground-mounted photovoltaic system based on a few simple inputs. To

use the calculator, type the address or geographic coordinates of the system's location, specify

the system size and array orientation, and provide some information about the system's cost and

electricity rates. PV Watts calculates estimated values for the system's annual, monthly and

hourly electricity production, and for the monetary value of the electricity. (NREL 2011)

4.2 Solar Water Heating

Solar water heating (SWH) is the conversion of sunlight into renewable energy for water

heating using a solar thermal collector. Solar water heating systems consist of various

technologies that are increasingly used worldwide. Since solar water heating is not included in

the target simulated buildings, they are not discussed in this report.

21

5. Plug Loads and Occupancy

Plug and process loads (PPLs) account for 33% of U.S. commercial building electricity

consumption (McKenney, et. al. 2010). Minimizing these loads is a significant challenge in the

design and operation of an energy-efficient building. (Lobato et al. 2011). (Lobato et al. 2012)

define PPLs as energy loads that are not related to general lighting, heating, ventilation, cooling,

and water heating, and that typically do not provide comfort to the occupants. The percentage of

total building energy use from PPLs is increasing. According to the U.S. Department of Energy

(DOE), by 2030, commercial building energy consumption is expected to increase by 24%; PPL

energy consumption is anticipated to increase by 49% in the same time frame (DOE 2010).

These trends illustrate the importance of PPL energy reduction to achieve an overall goal of

reducing whole-building energy consumption (Griffith 2007). Figure 9 will show commercial

building energy use breakdown.

Figure 9. Commercial Building Energy Use Breakdown (Griffith 2007)

Occupant Behavior

Occupant behavior affects the building energy use directly and indirectly by opening/closing

windows, turning on/off or dimming lights, turning on/off office equipment, turning on/off

heating, ventilation, and air-conditioning (HVAC) systems, and setting indoor thermal, acoustic,

and visual comfort criteria. Measured energy use of buildings demonstrated large discrepancies

even between buildings with same functions and located in similar climates. Among various

factors contributing to the discrepancies, occupant behavior is a driving factor. Occupant

behavior is also one of the most significant sources of uncertainty in the prediction of building

energy use by simulation programs due to the complexity and inherent uncertainty of occupant

behavior. With the trend towards low energy buildings that reduce fossil fuel use and carbon

22

emissions, getting occupants actively involved during the design and operation of buildings is a

key to achieving high energy performance without scarifying occupant comfort or productivity.

Pilot projects demonstrated that low energy systems, such as natural ventilation, shading to

control solar heat gains and glare, daylighting to dim lights, and demand controlled ventilation,

especially need the interactions and collaborations of occupants. Energy savings from 5 to 30%

were achieved by behavioral studies that motivate changes to occupant behavior (Tianzhen Hong

2013).

6. Modeling Simulation Results

This section includes, conventional and new building specifications, description of modeling

tools used in the project, building validation, which contains my simulation approach and tabular

inputs used for baseline buildings and energy efficient buildings. It also includes simulation

results for new buildings, older buildings and their comparison.

6.1 Building Specification

• Building Type: Office buildings

• Occupancy: 100Sqft/person

• Area: 50,000 Sqft and 100,000 SqFt

• Location: Phoenix, AZ, San Jose, CA, Chicago, IL

• Baseline: ASHRAE 90.1 2013, California Title 24 2013

• Modeling Tool: eQuest by Department of Energy

• Renewable Tool: PV Watts by NREL

• Internal Loads: Task lighting, area lighting, miscellaneous loads, and occupancy

• Miscellaneous Loads: Cooking equipment’s, plug loads, and computer server

Building Schematic

Figure 10. Building Schematic

23

In new construction for heating and cooling, ground source vertical closed loop heat pump is

used. Due to use of a ground source heat pump, there is only electrical energy consumption in

the building. The following energy efficient techniques used in the simulation. Default values in

eQuest have been selected for energy efficient features.

• Daylighting

• Natural ventilation

• Energy efficient building envelop

• Energy efficient lighting and plug loads

• Variable frequency drives

• Ground source heat pump for heating and cooling

• Ground source heat pumps for domestic hot water

Conventional construction, which is built in 1980s uses chillers and boilers for cooling and

heating. HVAC System type is multi zone air handler with hot water heating. No energy

efficiency techniques were used. Following are the details.

• No daylighting

• No natural ventilation

• Building envelop as per CA Title 24 1980 for location in California and ASHRAE 90.1

1980 for other locations

• Lighting and plug loads as per CA Title 24 1980 for location in California and ASHRAE

90.1 1980 for other locations

• No variable frequency drives

• Both electrical and natural gas consumption in the building. Natural gas used for both

domestic hot water and space heating

For sizing of solar array following parameters were used.

• DC system size depends on roof area of buildings. Calculated as, Size (kW) = Array Area

(m²) × 1 kW/m² × Module Efficiency (%)

• Monocrystalline PV module

• Fixed array type

• Array tilt 20 degree

• Azimuth angle 180 degree

• 60% of building roof area is covered with Solar array

Note: For a fixed array, the azimuth angle is the angle clockwise from true north describing the

direction that the array faces. An azimuth angle of 180° is for a south-facing array, and an

azimuth angle of zero degrees is for a north-facing array. All the new buildings are south facing

azimuth angle will be 180 degree for south facing array.

24

6.2 Modeling Tool

eQuest is designed to provide whole building performance analysis to buildings professionals,

i.e., owners, designers, operators, utility and regulatory personnel, and educators. Whole building

analysis recognizes that building is a system of systems and that energy responsive design is a

creative process of integrating the performance of interacting systems, e.g., envelop, fenestration,

lighting, HVAC, and domestic hot water (Hirsch 2012).

PV Watts Online Tool

PV Watts estimates the energy production and cost of energy of grid-connected photovoltaic

(PV) energy systems throughout the world. It allows homeowners, small building owners,

installers and manufacturers to easily develop estimates of the performance of potential PV

installations. PV Watts calculates estimated values for the system's annual, monthly and hourly

electricity production, and for the monetary value of the electricity (NREL 2011).

6.3 Building Specifications

Approach

• Modeled one floor baseline buildings with area of 50,000 and 100,000 Sqft

• Applying ASHRAE 90.1 2013 and CA Title 24 2013 standards and found out annual

electrical energy consumption

• Modeled same baseline buildings for three different locations; San Jose, CA, Phoenix,

AZ, Chicago, IL and found out annual electrical consumption

• Applying energy efficient techniques to baseline building to make it energy efficient

buildings and derived annual electrical consumption for three different locations

• By utilizing PV Watts online tool for sizing the solar array, derived electrical energy

production for one floor energy efficient buildings for all three locations

• Determined electrical energy consumption by gradually increasing floors for energy

efficient buildings for all three different locations

• Simultaneously sizing solar array for different floors to find out electrical energy

production

• After finding electrical energy consumption and production for different floors and

locations, the main aim is to determine maximum number of floors that can be built to

make net zero site energy using roof mounted solar PV.

Tabular Inputs for New Construction

Table 6-1 shows different inputs used in eQuest for baseline building, Energy Efficient

techniques and Net Zero Energy for different locations.

25

Table 6-1 Tabular inputs used in eQuest for baseline building, Energy Efficient techniques and

Net Zero Energy for different locations (San Jose, CA Chicago, IL and Phoenix, AZ)

Components Baseline Energy

Efficiency

Techniques

Net Zero Energy

Cooling: DX Coil EER: 10.4

(ASHRAE 90.1),

EER: 13.4 (B.

Griffith, 2007)

EER: 13.4 (B. Griffith,

2007)

EER: 9.6 (CA

Title 24)

Heating: Ground

Source Heat

pump

COP: 3.1

(ASHRAE 90.1),

COP: 4.2 (B.

Griffith, 2007)

COP: 4.2 (B. Griffith,

2007)

COP: 2.9 (CA

Title 24)

Variable Volume

Fan

Efficiency: 50%

(ASHRAE 90.1)

Efficiency: 70%

(B. Griffith, 2007)

Efficiency: 70% (B.

Griffith, 2007)

Efficiency: 50%

(ASHRAE 90.1)

Domestic Hot Water

Heater Fuel Electricity Electricity Electricity

Heater Type Heat pump Heat pump Heat pump

COP 7 (ASHRAE

90.1)

7 (ASHRAE

90.1)

7 (ASHRAE 90.1)

7 (CA Title 24) 7 (CA Title 24) 7 (CA Title 24)

Ground Source Heat pump

GSHP loop Head 71.6 ft.(ASHRAE

90.1)

71.6 ft.

(ASHRAE 90.1)

71.6 ft. (ASHRAE 90.1)

71.6 ft. (CA Title

24)

71.6 ft. (CA Title

24)

71.6 ft. (CA Title 24)

Ground Heat

Exchange (GHX)

type

Vertical well Vertical well Vertical well

Loop temp: 30 F min and 110

F Max (ASHRAE

90.1)

30 F min and 110

F Max (ASHRAE

90.1)

30 F min and 110 F Max

(ASHRAE 90.1)

Continued on the following page

26

30 F min and 110

F Max (CA Title

24)

30 F min and 110

F Max (CA Title

24)

30 F min and 110 F Max.

(CA Title 24)

Loop Flow Constant with no

Variable speed

drive (VSD)

Variable with

Variable speed

drive (VSD)

Variable with variable

speed drive (VSD)

Building Envelop

Window to wall

ratio

52.3% (ASHRAE

90.1)

30% (B. Griffith,

2007)

30% (B. Griffith, 2007)

52.3% (CA Title

24)

Window Glass

Type

Double clear

(ASHRAE 90.1)

Triple clear /Tint

(B. Griffith, 2007)

Triple clear /Tint (B.

Griffith, 2007)

Double clear (CA

Title 24)

Vertical Glazing

with U Factor

0.57 (ASHRAE

90.1) Btu/h.Ft2.F,

0.40 (B. Griffith,

2007) Btu/h.Ft2.F

0.40 (B.

Griffith,2007)Btu/h.Ft2.F

0.59 Btu/h.Ft2.F

(CA Title 24)

Steel Frame wall

U Factor

0.084 (ASHRAE

90.1) Btu/h.Ft2.F,

0.064 (B. Griffith,

2007) Btu/h.Ft2.F

0.064 (B. Griffith, 2007)

Btu/h.Ft2.F

0.082 Btu/h.Ft2.F,

(CA Title 24)

Roof Metal frame 0.055 Btu/h.Ft2.F

(ASHRAE 90.1),

0.065 Btu/h.Ft2.F

(CA Title 24)

0.023 Btu/h.Ft2.F

(B. Griffith, 2007)

0.023 Btu/h.Ft2.F (B.

Griffith, 2007)

Floors wood

Framed

0.051 Btu/h.Ft2.F

(ASHRAE 90.1),

0.047 Btu/h.Ft2.F

(B. Griffith, 2007)

0.047 Btu/h.Ft2.F (B.

Griffith, 2007)

0.071 Btu/h.Ft2.F

(CA Title 24)

Windows Double Pane

(ASHRAE 90.1)

Triple pane Triple pane

Double Pane (CA

Title 24)


27

Lighting Systems

Area Lighting Fluorescent light Fluorescent light Fluorescent light

Office 1.10 W/Ft2

(ASHRAE 90.1)

0.5 W/Ft2 (B.

Griffith, 2007)

0.5 W/Ft2 (B. Griffith,

2007)

1.10 W/Ft2 (CA

Title 24)

Corridor 0.66 W/Ft2

(ASHRAE 90.1)

0.5 W/Ft2 (B.

Griffith, 2007)


2007)

0.66 W/Ft2 (CA

Title 24)

Lobby 1.30 W/Ft2

(ASHRAE 90.1)

0.5 W/Ft2 (B.

Griffith, 2007)


2007)

1.10 W/Ft2 (CA

Title 24)

Rest rooms 0.98 W/Ft2

(ASHRAE 90.1)

0.7 W/Ft2 (B.

Griffith, 2007)


2007)

0.98 W/Ft2 (CA

Title 24)

Conference

rooms

1.30 W/Ft2

(ASHRAE 90.1)

0.6 W/Ft2 (B.

Griffith, 2007)


2007)

1.40 W/Ft2 (CA

Title 24)

Mechanical/

Electrical room

1.50 W/Ft2

(ASHRAE 90.1)

0.5 W/Ft2 (B.

Griffith, 2007)


2007)

0.70 W/Ft2 (CA

Title 24)

Computer Server

Room

1.50 W/Ft2

(ASHRAE 90.1)

1.1 W/Ft2 (B.

Griffith, 2007)


2007)

0.70 W/Ft2 (CA

Title 24)

Miscellaneous

load

0.75 W/Ft2

(Default eQuest)

0.6 W/Ft2 (B.

Griffith, 2007)


2007)


28

Passive architecture

Day lighting No Yes with Day

lighting Sensors

Yes with Day lighting

Sensors

Occupancy

sensors

No Yes Yes

Natural

Ventilation

No Yes Yes

Night Purge

ventilation

No Yes Yes

Waste Heat

Recovery

No Yes Yes

6.4 Modeling Results

Tables 6-2 to 6-7 show the output of new office building with different sizes, locations and

number of floors.

Table 6-2 Output of new office building with 50,000 Sqft in Phoenix, AZ for different number of

floors

Table 6-3 Output of new office building with 100,000 Sqft in Phoenix, AZ for different number

of floors

Floors Roof Area Annual

Electricity

Consumption

Annual

Electrical

Production

Net Zero Site

Energy (roof

mounted

solar PV)

1 50,000 Sqft 446,480 kWh 944,471 kWh Yes

2 25,000 Sqft 462,130 kWh 475,018 kWh Yes

3 16,670 Sqft 480,060 kWh 311,931 kWh No


Electricity

Consumption

Annual

Electrical

Production

Net Zero Site

Energy (roof

mounted solar

PV)

1 100,000 Sqft 870,360 kWh 1,888,942 kWh Yes

2 50,000 Sqft 900,800 kWh 944,471 kWh Yes

3 33,330 Sqft 918,520 kWh 623,862 kWh No

29

Table 6-4 Output of new office building with 50,000 Sqft in San Jose, CA for different number

of floors

Table 6-5 Output of new office building with 100,000 Sqft in San Jose, CA for different number

of floors

Table 6-6 Output of new office building with 50,000 Sqft in Chicago, IL for different number of

floors


Electricity

Consumption

Annual

Electrical

Production

Net Zero

Site

Energy (roof

mounted

solar PV)

1 50,000 Sqft 378,190 kWh 824,189 kWh Yes

2 25,000 Sqft 390,060 kWh 413,649 kWh Yes

3 16,670 Sqft 397,330 kWh 275,248 kWh No


Electricity

Consumption

Annual

Electrical

Production

Net Zero

Site

Energy (roof

mounted

solar PV)

1 100,000 Sqft 748,640 kWh 1,648,377 kWh Yes

2 50,000 Sqft 761,470 kWh 824,189 kWh Yes

3 33,330 Sqft 770,620 kWh 550,496 kWh No


Electricity

Consumption

Annual

Electrical

Production

Net Zero

Site

Energy (roof

mounted

solar PV)

1 50,000 Sqft 328,430 kWh 677,148 kWh Yes

2 25,000 Sqft 336,070 kWh 339,882 kWh Yes

3 16,670 Sqft 342,030 kWh 230,000 kWh No

30

Table 6-7 Output of new office building with 100,000 Sqft in Chicago, IL for different number

of floors

Net Zero Energy of Conventional Construction

• Building Type: Office building

• 1980s construction

• Area: 100,000 SqFt

• Location: Phoenix, AZ, San Jose, CA, Chicago, IL

• Modeling Tool: eQuest by Department of Energy

• Renewable Tool: PV Watts by NREL

• Occupancy: 100 SqFt/person

• No passive architecture

• Standard Chillers and Boilers

• Baseline lighting density (CA title 24, ASHRAE 90.1)

• Baseline building envelop (CA title 24, ASHRAE 90.1)

• No Variable Frequency Drive

The section from Tables 6-8 to 6-10 gives an output of conventional construction office building

for 100,000 Sqft with different locations and number of floors


Electricity

Consumption

Annual

Electrical

Production

Net Zero

Site

Energy (roof

mounted

solar PV)

1 100,000 Sqft 664,490 kWh 1,354,297 kWh Yes

2 50,000 Sqft 676,660 kWh 677,148 kWh Yes

3 33,330 Sqft 683,640 kWh 338,574 kWh No

31

Location: San Jose, CA

Table 6-8 Output of conventional office building with 100,000 Sqft in San Jose, CA for different

number of floors

Location: Phoenix, AZ

Table 6-9 Output of conventional office building with 100,000 Sqft in Phoenix, AZ for different

number of floors

Note: One floor can be converted into Net Zero Source Energy in both San Jose, CA and

Phoenix, AZ if annual gas consumption converted into electrical consumption.


Electricity

Consumption

Annual

Electrical

Production

Annual Gas

Consumption

kBtu

Net

Zero Site

Energy

(roof

mounted

solar PV)

1 100,000

Sqft

903,150 kWh 1,648,377

kWh

1,248,900 Yes

2 50,000

Sqft

944,250 kWh 824,189

kWh

1,296,900 No

3 33,330

Sqft

972,840 kWh 550,496

kWh

1,370,300 No


Electricity

Consumption

Annual

Electrical

Production

Annual Gas

Consumption

kBtu

Net Zero

Site

Energy

(roof

mounted

solar PV)

1 100,000

Sqft

1,151,600 kWh 1,888,942

kWh

771,300 Yes

2 50,000

Sqft

1,215,500 kWh 944,471

kWh

831,840 No

3 33,330

Sqft

1,265,600 kWh 623,862

kWh

893,550 No


32

Location: Chicago, IL

Table 6-10 Output of conventional office building with 100,000 Sqft in Chicago, IL for different

number of floors

Comparison between New and Conventional Building Parameters

In this section from Tables 6-11 to 6-13 gives comparison between new and conventional

building parameters for 100,000 Sqft for different location

Table 6-11 Comparison between new and conventional building parameters for Phoenix, AZ

with different number of floors.


Electricity

Consumption

Annual

Electrical

Production

Annual Gas

Consumption

kBtu

Net Zero

Site

Energy

(roof

mounted

solar PV)

1 100,000

Sqft

962,800 kWh 1,354,297

kWh

1,960,000 No

2 50,000

Sqft

1,012,000 kWh 677,148

kWh

2,008,000 No

3 33,330

Sqft

1,047,300 kWh 338,574

kWh

2,051,000 No

Sector Floors New building Conventional building

Space Cooling

1 233,030 kWh 245,200 kWh

2 256,780 kWh 293,700 kWh

3 268,280 kWh 317,900 kWh

Space Heating

1 0 337,360 kBtu

2 0 437,830 kBtu

3 0 499,610 kBtu



33

Table 6-12 Comparison between new and conventional building parameters for San Jose, CA

with different number of floors.

Hot Water

1 68,230 kWh 393,930 kBtu

2 68,230 kWh 394,000 kBtu

3 68,230 kWh 393,940 kBtu

Ventilation Fans

1 34,580 kWh 98,200 kWh

2 43,170 kWh 113,900 kWh

3 51,470 kWh 120,600 kWh

Pump & Auxiliary

1 18,520 kWh 48,900 kWh

2 20,900 kWh 62,800 kWh

3 21,520 kWh 69,300 kWh


Space Cooling

1 141,510 kWh 155,520 kWh

2 155,550 kWh 179,700 kWh

3 162,860 kWh 191,800 kWh

Space Heating

1 0 773,200 kBtu

2 0 821,900 kBtu

3 0 895,400 kBtu

Hot Water

1 70,150 kWh 475,700 kBtu

2 70,150 kWh 475,000 kBtu

3 70,150 kWh 474,900 kBtu

34

The space heating shows negligibly small at San Jose, CA and Phoenix, AZ; most probably due

to higher thermal mass and higher U value of insulation. The same building was simulated using

boiler for space heating keeping all the other parameters same. The result was shown to be, 2800

kBtu. Repeated simulation were made and small values were shown for space heating which may

be an artifact of the simulation.

Table 6-13 Comparison between new and conventional building parameters for Chicago, IL with

different number of floors.

Ventilation Fans

1 17,830 kWh 71,200 kWh

2 20,790 kWh 76,200 kWh

3 23,100 kWh 78,500 kWh

Pump & Auxiliary

1 12,350 kWh 41,260 kWh

2 13,620 kWh 51,500 kWh

3 14,460 kWh 56,800 kWh


Space Cooling

1 89,010 kWh 152,130 kWh

2 102,650 KWh 184,000 kWh

3 117,520 kWh 200,000 kWh

Space Heating

1 33,260 kWh 1,416,500 kBtu

2 36,870 kWh 1,475,000 kBtu

3 40,210 kWh 1,517,350 kBtu

Hot Water

1 55,910 kWh 532,500 kBtu

2 55,910 kWh 533,000 kBtu

3 55,910 kWh 533,650 kBtu


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Summarization of Results

New building: By roof mounted solar array and by using energy efficient techniques it is

possible to make buildings a net zero site energy, two floors can be built regardless of location

and area. For more floors, then it has to make use of surrounding space like a parking lot.

Conventional Building: By simulating and sizing solar array for conventional buildings with

same area and location, it is observed that only one floor can be zero net site energy using roof

mounted solar PV if natural gas consumption is converted into electrical consumption. With

comparatively high electrical energy consumption to that of new construction, further floors

cannot be make zero net site energy using roof mounted solar PV. As it is conventional

construction, there is no ground source heat pump installed in the building so has both electrical

and natural gas consumption. By having natural gas consumption, it is very difficult to make

more than one floor zero net site energy using roof mounted solar PV.

7. Simulation Verification

To verify simulation, I modeled similar building whose results are available to us. In this case I

modeled Research Support Facility (RSF) office, which is Net Zero Energy located in Colorado

(Hootman 2012). I used all the energy efficient techniques to verify my simulation project.

Project Data (Hootman 2012):

Building Area: 222,000 Sqft

Floors: 4 story building

Location: Denver, CO

Ventilation Fans

1 14,390 kWh 65,820 kWh

2 16,700 kWh 80,500 kWh

3 17,800 kWh 85,500 kWh

Pump & Auxiliary

1 10,080 kWh 50,270 kWh

2 11,490 kWh 61,300 kWh

3 12,410 kWh 67,300 kWh

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Climate Zone: 5B; Cool, Dry

Occupant: 822

Occupied hours per week: 50 Hrs.

Roof Area: 69, 950 Sqft

Data Center Energy: 65 Watts/person for 1200 occupants on campus will be 683,280 kWh/year

Total Energy Consumption: 2254 MWh/yr

My simulation Output:

Data Center Energy: 65 Watts/person for 1200 occupants on campus will be 683,280 KWh/ year

Total Energy consumption: 2285 MWh

Table 6-14 Comparison between RSF building real data and my simulation output

Points RSF building real data Simulation output

Final Design Energy Use

intensity

33.2 kBtu/ft2/yr 35.12 kBtu/ft2/yr

Annual Energy consumption 2254 MWh/yr 2285 MWh/yr

By modeling RSF building and getting output similar to real data verifies all the energy efficient

techniques used in simulation project.

8. Future of Net Zero Energy Building

Net zero energy (NZE) is still a relatively new movement; only a small percentage of current

building construction has a goal of NZE. However, efforts are increasing, with a doubling in the

number of commercial NZE buildings over the last two years. Policies and programs can

dramatically change the landscape for Net Zero Energy (NZE) buildings. California Public

Utilities Commission (CPUC) adopted the big bold Initiative, which focused that all new

residential and commercial construction be NZE by 2020 and 2030 respectively. As per my

view, reduction, reuse, and renewables are three main steps towards zero net energy. Reduction

must come first, ideally by load reduction followed by efficiency measures. Reuse comes next,

with a focus on creatively putting waste energy in the systems back into beneficial use.

Renewable will produce energy which will help to achieve net zero design. Below are my

suggestions which can be helpful towards future of Net Zero Energy Buildings.

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• Passive architecture is a fundamental prerequisite for net zero energy buildings.

Appropriate use of passive architecture can reduce in significant amount of heating and

cooling load.

• Use of ground source heat pump instead of boilers and chillers for heating, cooling, and

domestic hot water can reduce in significant amount of electrical consumption in the

buildings and there will not be any natural gas consumption in the buildings.

• Using energy efficient lighting fixtures and lighting controls can lower electrical

consumption

• Using variable speed drives can lower electrical consumption

• Waste heat recovery technique is also very useful towards energy reduction process

• Reduction in building plug loads and behavioral changes also very important towards net

zero energy.

9. References

Athienitis, A. 2006. Design and Optimization of Net Zero Energy Solar Homes. ASHRAE Report,

American Society of Heating, Refrigerating and Air-Conditioning Engineers Inc.

Griffith, B., N. Long, P. Torcellini, and R. Judkoff. 2007. Assessment of the Technical Potential for

Achieving Net Zero-Energy Buildings in the Commercial Sector. Technical Report,

National Renewable Laboratory.

California Public Utilities commission. 2008. Accessed December 6, 2015.

http://www.cpuc.ca.gov/NR/rdonlyres/C27FC108-A1FD-4D67-AA59-

7EA82011B257/0/3.pdf.

Codes, E. 2012. "Lighting Development, Adoption and Compliance Guide." Building Technology

program. September. Accessed December 2, 2015.

https://www.energycodes.gov/sites/default/files/documents/Lighting_Resource_Guide.

pdf.

Collyer, B. 2012. Zero Net Energy Program. Pacific Gas and Electric Company Report, San

Francisco: Pacific Gas and Electric Company.

Department of Energy. 2008. Accessed December 6, 2015.

http://energy.gov/energysaver/solar-water-heaters.

—. 2008. Accessed November 18, 2015. http://energy.gov/energysaver/heat-pump-systems.

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—. 2009. eQUEST. Sepetmber. Accessed November 2015. http://www.doe2.com/equest/.

Haglund, K. 2012. Department Of Energy. Northenstar. November. Accessed November 18,

2015.

http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/measure_g

uide_windows.pdf.

Harrell, G. 2009. ENERGY MANAGEMENT SERVICES. PhD Thesis, Tennessee: National Renewable

Laboratory.

Hirsch. 2012. eQuest Introductory Tutorial. Tutorial, Camarillo: Department of Energy.

Hong, T., H. Lin. 2013. Occupant Behavior: Impact on Energy Use of Private Offices. Publish

Report, Ernest Orlando Lawrence Berkeley National Laboratory, 12.

Hootman, T. 2012. Net Zero Energy Design: Commercial buildings, New jersey: John Wiley &

Sons, Inc.

Kwatra, S., J. Amann, H. Saches. 2013. Miscellaneous Energy Loads in Building. Published

Report, Washington: American Council of Energy Efficienct Economy.

National Renewable Energy Laboratory (NREL). 2011. PV Watts. Accessed December 10, 2015.

http://pvwatts.nrel.gov/pvwatts.php.

Sheppy, M., C. Lobato, S. Pless, L. Polese, and P. Torcellini. 2012. Assessing and Reducing Plug

and Process Loads in Office Buildings. Fact Sheet, Denver: National Renewable Research

Laboratory.

Torcellini, P. 2006. Zero Energy Buildings: A Critical Look at the Definition. Published Report,

Denver: National Research Laboratory, 15.

Torcellini, P., S. Pless, and C. Lobato. 2010. Main Street Net-Zero Energy Buildings: The Zero

Energy Method in Concept and Practice. Case Study, Phoenix: National Research

Laboratry.

Zero net energy of commercial building

Engineering

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