energy water nexus: balancing two precious resources in hvac … · 2016-05-25 · trends –...

Energy Water Nexus: Balancing Two Precious Resources in HVAC Systems

Stephen G. Kline, P.E.National Sales ManagerBaltimore Aircoil CompanyApril 29, 2016

Agenda

� Trends – Temps, A/C, Energy & Water� What is the Energy-Water Nexus? � Comparison of Water-Cooled vs. Air-Cooled � Leveraging Energy & Water Efficient HVAC

Systems

Trends – Temperature Changes

Higher ambient temperatures› 2015 – Warmest year in US history› National weather trends1&2

Temperatures impact air conditioning design, size and energy consumption

› New “Extremely Hot” Climate Zone 0

1. EPA. Climate Change Indicators in the United States http://www.epa.gov/climatechange/pdfs/print_temperature-2014.pdf2. National Oceanic and Atmospheric Administration, National Climatic Data Centerhttp://www.ncdc.noaa.gov/temp-and-precip/time-series/index.php

Rate of Temperature Change in the U.S. (1901-2012)1

ASHRAE News: Updated Standard 169, Climatic Data for Building Design Standardshttps://www.ashrae.org/news/2014

Trends – Energy Demand

Market trends suggest that demand for energy will rise dramatically over the next 25 years

1.International Energy Outlook 2013 (EIA-0484(2013)

Global demand for all energy

sources is forecast to grow by nearly

56% from 2010 through 2040 1.

U.S. demand for all types of energy

is expected to increase by 11% by

20402. Commercial sector by 24%.

2.Annual Energy Outlook (DOE-er0383(2014)

Trends – Air Conditioning

• Air-conditioning systems drive many power plant peak loads and have been identified as an energy reduction opportunity.

1. U.S. Energy Information Administration http://www.eia.gov/

U.S. Commercial Electricity Consumption

Other Air Conditioning

Air-conditioning systems account for 12% of U.S. commercial electricity consumption1

Trends – Air Conditioning

There is still a lot of unmet demand for air conditioning

Country

Population

(Millions)

Annual Cooling

Degree Days Ratio to US

United States 316 882 1.0

India 1252 3120 14.0

China 1357 1046 5.1

Brazil 200 2015 1.4

Indonesia 250 3545 3.2Source: Davis and Gertler, PNAS, 2015

Future demand for air conditioning will significantly increase electricity demand

Trends – Water Availability

Trends – Water Usage

1. 2003 National Renewable Energy Lab report

In 2011, 52% of fresh water used in the U.S. was used

for power plant cooling; 5% was used for commercial

applications1.

Population growth› High demand for electricity

› High demand for fresh water

Climate changes› Increasing temperatures

› Changes in precipitation patterns

› Extreme weather events

Water availability & cost increase

driven by:

1. US Department of Energy. Water-Energy Nexus: Challenges and Opportunities.http://energy.gov/sites

2013


1. 2003 National Renewable Energy Lab Report.

On average, 2 gallons of water are consumed per 1 kWh of electricity generated in the U.S.1

Western = 4.42 gal/kWh

Nat’l Avg. = 2 gal/kWh


Water withdrawn is the total volume removed from a water source such as a lake or river. Often, a portion of this water is returned to the source and is available to be used again.

Water consumed is the amount of water removed for use and not returned to its source.

Adapted from “Thirsty Energy: Water and Energy in the 21st Century,” released in February 2009 by the World Economic Forum in partnership with Cambridge Energy Research Associates


Once-Through Cooling(generic coal technology)

Closed-Loop Cooling(generic coal technology)

0.25gallons

Withdrawal Consumption

Hydroelectric

3.64gallons

1.01gallons

0.69gallons

ConsumptionWithdrawal0

gallons

4.5gallons

ConsumptionWithdrawal

Water usage analysis will focus on consumption, not withdrawal

Source: “A Review of Operational Water Consumption and Withdrawal Factors for Electricity Generating T echnologies”, Macknick, etc. National Renewable Energy Laboratory Technical Report 6A20-50900, March 2011

Water Consumption in Power Generation

Generating electricity is water-intensive

Hydro

0.2 gallons

0.67 gallons

0.69 gallons

4.5gallonsWater consumed

to produce 1 kWh of electricity

U.S. Weighted Average

2.0gallons

Sources: National Renewable Energy Laboratory. Illu stration by Andy Warner“Consumptive Water Use for U.S. Power Production”, Torcellini, Long, Judkoff, December 2003

Energy -Water Nexus

Energy and Water are Interdependent

Water is needed to generate electricity (power plant cooling)

Energy is needed to process and distribute Water

Energy -Water Nexus

What is Energy-Water Nexus?

The conflict created by trying to conserve both resources at the same time

How does this apply to the HVAC industry?

Water-Cooled System Air-Cooled System

VS

Energy -Water Nexus

2017 ASHRAE Winter Conference – Las VegasConference Tracks

1. Fundamentals and Applications

2. HVAC&R Systems and Equipment

3. Water-Energy Nexus4. Commercial and Industrial IAQ

5. Mission Critical Design and Operation

6. Effects of Climate Change on HVAC&R

7. Energy Efficient Industrial Buildings

8. Building Operation and Performance

Energy Water Nexus

ASHRAE 2017 Conference Track #3:

The interdependencies between our water and energy systems are clear and are becoming more prominent as development requires the use of more resources while over-use and climate change make some resources scarcer. On the macro level, water is used in all phases of energy production and electricity generation (including renewables); and energy is required to extract, convey and deliver water, and to treat wastewaters prior to their return to the environment. On the micro level, the water-energy nexus is a major consideration for the HVAC&R community in determining equipment and system selection and design as well as building operation. This track will present papers and programs highlighting recent research on this issue as well as technologies and designs intended to reduce the gap between energy and water efficiency.

Air-Cooled vs. Water-Cooled Heat Rejection

Air-Cooled System

• Design day is based on dry bulb temperature

• Larger footprint (more surface area)

• Higher sound level

• Higher energy consumption; lower efficiency

• Consumes no water, at site (no evaporative cooling)

Water-Cooled System

• Design day is based on wet bulb temperature

• Smaller footprint (typically require equipment room)

• Lower sound level

• Lower energy consumption; higher efficiency

• Consumes water (evaporative cooling)

Comparison of Water-Cooled vs. Air-Cooled

500 ton system comparison

Water-Cooled System Air-Cooled SystemOR

ParameterWater Cooled

SystemAir Cooled

System

Chiller Efficiency [Full Load] (kW/ton)1 0.585 1.237

Chiller Efficiency [IPLV] (kW/ton)1 0.38 0.745

System Capacity [Full Load] (Ton) 500 500Average Capacity [IPLV] (Ton) 290 290Condenser Pump (HP) 30 --Cooling Tower Fan (HP) 20 --

Hours of Operation [IPLV] 4380 4380

1. Efficiencies based on ASHRAE 90.1-2013, Path B; California Code of Regulations Title 24- 2016IPLV = 0.01A+0.42B+0.45C+0.12DA = COP@100%, B = COP@75%, C = COP@50%, D = COP@25%

500 Ton System Parameters

Energy Usage

Water-Cooled Advantage:� Reduction in annual energy usage by 37%

� Reduction in peak energy demand by 47%

0

0.2

0.4

0.6

0.8

1

1.2

1.4

Water-CooledSystem

Air-CooledSystem

Water-CooledSystem

Air-CooledSystem

kW /

Ton

Chiller Condenser Pump Cooling Tower Fan

Avg. Energy UsageIPLV Conditions

0.47 kW/Ton

0.75kW/Ton 0.66

kW/Ton

1.24kW/Ton

Peak Energy DemandFull load

37%

47%

Assumptions:Energy rate $0.103/kWhDemand Charge $13.44/kWHrs of Operation (IPLV) 4380

Annual Operating Cost

ElectricityCost

Water Cost TotalOperating

Cost

ElectricityCost

Water Cost TotalOperating

CostEnergy Charge Demand Charge Annual Water & Sewage Cost Annual Chemical Treatment Cost

$66K$15K $81K

$106K

$0

$106K

Water-Cooled 500 Ton System Air-Cooled 500 Ton System

Water-Cooled Advantage:

� Savings of $25,000 annually

� 24% savings on annual operating costs

Assumptions:Energy rate $0.103/kWhDemand Charge $13.44/kWWater rate $2.23/1000galSewage rate $5.3/1000galHrs of Operation (IPLV) 4380

$25K

Water Consumption per kWh

4.64

7.85

5.32

16.74 5.13

7.25

8.39

7.854.15

Gallons consumed per kWh generation

Western states have greatest potential to save wate r with evaporative cooling technology

> 4 gallons/kWh

1.6 to 3.9 gallons/kWh

< 1.5 gallons/kWh

Source: “Consumptive Water Use for U.S. Power Produ ction”, Torcellini, Long, Judkoff, December 2003

Water Usage Comparison

Cycles of concentration = 6 Air-Cooled Water-Cooled

Energy Per Ton of Cooling (kW) 1.24 0.66

Water Used Per kW Generation (Gallons) 4.64 4.64

Water Used To Generate Power Per Ton of Cooling (Gallons) 5.75 3.06

Water Used In Cooling Tower Per Ton of Cooling (Gallons) 0.00 2.20

Total Water Used Per Ton of Cooling (Gallons) 5.75 5.26

of water used to generate 1 kWh of electricity

California Weighted Average

4.64gallons

In certain states, water-cooled technology can use less overall water usage compared to air-cooled systems

Water Usage Comparison

Cycles of concentration = 6 Air-Cooled Water-Cooled

Energy Per Ton of Cooling (kW) 1.16 0.60

Water Used Per kW Generation (Gallons) 4.64 4.64

Water Used To Generate Power Per Ton of Cooling (Gallons) 5.39 2.78

Water Used In Cooling Tower Per Ton of Cooling (Gallons) 0.00 2.20

Total Water Used Per Ton of Cooling (Gallons) 5.39 4.98

of water used to generate 1 kWh of electricity

California Weighted Average

4.64gallons

In many climates, water-cooled technology will have less overall water usage compared to air-cooled systems

Total Cost Comparison


� Payback Period of less than 2 years

� Life span of Water-Cooled System ~20 years vs. 15 years for Air-Cooled1

� Total Water-Cooled System financial benefit ~$465K at the end of 20 years

$465K Savings

500 Ton System Cost Equipment & Install Annual Operati ng Avg. Life 1

Air-Cooled System $192K $ 106K 15-20 years

Water-Cooled System $ 235K $ 81K 20-30 years

1. Selecting Chillers, Chilled Water Systems by David Grassl. http://www.csemag.com

$-

$500

$1,000

$1,500

$2,000

$2,500

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Th

ou

san

ds

YearsWater Cooled System Air-Cooled System

Less than 2 Year

Payback

Other Comparative Examples

Operating an Efficient District Cooling Plant in Water-Stressed Regions

• IDEA’s Website: http://www.districtenergy.org/past-webinars-2/


Impact of Air-Cooled System vs. Water-Cooled System on:

� Annual energy use� Peak energy demand

� Operating cost� Water consumption

Source: Operating and Efficient District Cooling Plant in Water-Stressed Regions. Part 1: The Energy-Water Nexus by Roy Hubbard



� 48% reduction in annual energy consumption

� 51% reduction on peak energy demand

� 31% savings on annual operating cost

Saving Energy = Saving Water

Energy savings = 0.561Ton

kW

0.561Ton

kWhrkW

Gal

−X 2

hrTon

Gal

−

Power plant water savings* 1.12

Air cooled = 1.12 gal more water at the power plant per ton-hr of cooling

When to use Water-Cooled vs. Air-Cooled Systems?

• PG&E study simulating three sizes of chiller plants in three climatic zones.1

› Recommended chilled water plants greater than 300 Tons shall employ water-cooled chillers

› Resulted in air-cooled equipment restrictions in California Title 24

1) PG&E Codes and Standards Enhancement Report: Code Change Proposal for Cooling Towers, http://www.energy.ca.gov/title24/2005standards/archive/documents/2002-04-23_workshop/2002-04-11_COOL_TOWERS.PDF


1) http://www.energy.ca.gov/2012publications/CEC-400-2012-004/CEC-400-2012-004-CMF-REV2.pdf

• Title 24: 2013 Building Energy Efficiency Standard› Section 140.4


Large Buildings (> 300 tons)› Water cooled systems provide clear-cut economic and

environmental justification.

Mid-size Buildings (100-300 tons)› Air cooled systems may offer first cost incentive to sacrifice energy

efficiencies of water cooled systems.

How to Leverage Water-Cooled Systems?

Saving Energy & Water with Water-Cooled

Systems

How to leverage Water-Cooled Systems?

Temperatures vary by location, season, and time impacting cooling load and energy use

Energy Saving Tip: Utilize lowest temperatureTake advantage of ambient Wet Bulb temperatures

ASHRAE 0.4% Wet Bulb Temperatures

Location Wet Bulb CWT Energy Savings

Baltimore, MD 78°F 85°F 0.57 kW/TR Base

New York, NY 76°F 83.5°F 0.55 kW/TR $2K

Los Angeles, CA 70°F 80.5°F 0.53 kW/TR $4K

Seattle, WA 66°F 76.0°F 0.49 kW/TR $6K

Denver, CO 65°F 75.0°F 0.48 kW/TR $9K

How to Leverage Water-Cooled Systems?

Chiller account for ~81% of Water-Cooled System energy consumption

Energy Saving Tip: Take full advantage of your cooling towerSupply lower condenser water temperatures and use free cooling during cold weather operation

�2% reduction in chiller energy consumptionper degree below 85⁰F

� Reduce cooling system annual energy usage

by as much as 40%with Free Cooling

Water Usage in Cooling Towers(per Ton at peak conditions)

Drift

Evaporation

Blow Down

Blow down (via cycles of concentration) is the only significant variable to control in cooling towers for reducing water usage

TOTAL WATER USAGE

Evaporation66%

Blowdown33%

Drift1%

Evaporation83%

Blowdown16%

Drift1%

3 Cycles (~2.7 gallons/ton)

6 Cycles (~2.2 gallons/ton)

Blowdown

Also known as “bleed”

When water is evaporated in a cooling tower, dissolved solids and minerals are left in remaining water

Blowdown is required to control total dissolved solids cycles of concentration (COC)

To prevent scaling and fouling of heat transfer surfaceTo ensure efficient operation of cooling tower and HVAC system

Reducing Blowdown

Blowdown can be reduced by:

Optimizing cycles of concentration

Increasing COC has diminishing returns while significantly increasing risk

Reducing Blowdown

Maintaining / protecting bleed valve

Blowdown water with a high concentration of solids can block the solenoid valve open. Protect bleed valve with an upstream filter / strainer

Maintaining / calibrating conductivity meter

Regular cleaning and calibrating of conductivity meter will provide

accurate bleed control and minimize water consumption

Blowdown can be reduced by:

Improving control of bleed system

Reduce Blowdown

Materials of Constructions: Higher grades of materials of construction is one way to increase the cycles of concentration, reduce water usage and protect against leaks

Manufacturer water quality guidelines reflect potential water savings with different cycles of concentration:

› G-210 galvanized steel

› 301 stainless steel



› Fiberglass and polymer coatings

Evaporation

Water is “consumed” by evaporation, but not “lost”

or destroyed, unlike other resources such as oil

or natural gas

Evaporation Rules of Thumb2.0 gpm / 1,000,000 btuh3.0 gpm / 100 tons

Can be used for calculating peak make-up flow rates, sizing make-up piping, and water treatment

These “rules” overestimate annual water usage

Reducing Evaporation

Evaporation rate is reduced as the WB falls***More sensible heat transfer occurs

Drift

Also known as “carryover”, water droplets entrained in the cooling tower discharge air

Waterdeck

surface

WarmMoist

Air Flow

Waterdeck

surface

Cold Water Out

Dry Air In Dry Air In

MoistAir Out

Hot waterin

Hot waterin

Drift

Drift eliminator performance is rated at maximum percentage of loss allowed

Typical crossflow cooling tower is 0.005%, or .00005 of cooling tower design flow, or less

Counterflow cooling tower is typically is 0.002% or less

Reducing Drift

Replace obsolete drift eliminators

Check drift eliminators are installed correctly and are not damaged, fouled, or blocked

Be sure cooling tower is operating with proper fan speed control

Be sure cooling tower water pressure and / or flow rate are set properly

Protect the cooling tower from excessive winds

Reducing Water ConsumptionS

ave

Wat

er

Hybrid Technology

� Optimizes water use and energy use based on cooling load and water availability

Sav

e W

ater

� Balances use of water and energy

Adiabatic Fluid Coolers

Reducing Water Consumption

Alternative sources of water› Rain water

› Reclaim or recycled water

› Air conditioning condensate

Reusing blowdown water from cooling tower› Irrigation

› Recycle for uses such as washing/washdown

Monitoring water quality is important component

Reducing Water & Energy Use

• Increase the size (surface area) of the cooling tower:› Decrease the fan motor size› Lower sound level

Oversized

and slowed

down

40 HP15 HP

Top = 85 dB(A) @ 5’

Nominal 500

ton cooling

tower

Top = 76 dB(A) @ 5’

Maintenance is Key

Saving Energy = Saving Water

Summary• Global demand for energy, water, and HVAC is increasing

• Air conditioning systems consume significant energy and drive peak energy demands

• Consider not only water usage at the site, but also the power plant. Energy-water nexus

• Water-cooled systems are often more energy efficient, and therefore more water efficient, than air cooled systems

• Additional methods to save water and energy on water cooled systems

Energy Water Nexus: Balancing Two Precious Resources in HVAC Systems

Stephen G. Kline, P.E.National Sales ManagerBaltimore Aircoil CompanyApril 29, 2016

energy water nexus: balancing two precious resources in hvac … · 2016-05-25 · trends –...

Documents