New design tools and controls for load-shifting with radiant systems

Paul Raftery, Carlos Duarte, Fred Bauman & Stefano Schiavon

2 Oct 2019

Acknowledgments

CBEß Stefano Schiavonß Carlos Duarteß Jonathan Woolleyß Jovan Pantelic

EPFLß Caroline Karmann

Taylor Engineeringß Hwakong Cheng

TRC Energy Servicesß Gwelen Paliagaß Jingjuan (Dove) Feng

New Buildings Instituteß Cathy Higgins

ARTIC, Anaheim ↑David Brower, Berkeley ↗SMUD, Sacramento →IDeAs Z2, San Jose ↘Delta HQ, Fremont ↓

3 Oct 2019

Overview

Objectiveß Develop new controls for high

thermal mass radiant systems

Approachß Interview expertsß Review controls and trend data

from existing buildings ß Develop new controls and

iteratively test in simulation ß Demonstrate in two buildings

4 Oct 2019

Interviews with designers

ß Interviewed 11 prominent professionals who have designed over 330 radiant cooled buildings

Findingsß Generally a wide diversity of design and

control solutions - reveals opportunities for standardization and improvement

ß Very rarely leverage thermal mass to shift load.

Example results: Radiant zone control device

How do you control radiant zones? #Two position zone valves 6Modulating zone valves 4Pumps with 3-way control valves at the zone 3

Constant speed pump 1Variable speed pump 1

5 Oct 2019

Trend data from a radiant building (in July)

23 °C 73 °F

27 °C81 °F

Peak building demandPeak electricity pricesWarmest outside temperatures

Noon Noon NoonNoonNoon

6 Oct 2019

Motivation

How can we help designers benefit from the load shifting potential

of radiant systems?

7 Oct 2019

Simulation results: Common control strategy

Results from a single zone energy simulation on the cooling design day.

Conditionsß Variable flowß Constant temperature

(18 °C | 64 °F) ß Modulating valves

0.5 °C (1 °F) band

Advantagesß Simple, familiar controls

8 Oct 2019

Effect of different operating times

Conditionsß Constant temperature

(18 °C | 64 °F)ß Constant flow

(two position valves)ß Constant duration of

operation (9 hours)ß Varying time of operation

9 Oct 2019

Conditionsß Constant temperature

(18 °C | 64 °F)ß Constant flow

(two position valves)ß Constant duration of

operation (9 hours)ß Varying time of operation

Resultß Can maintain comfort

regardless of time of operation

Effect of different operating times

10 Oct 2019

Design/operation possibilities: Afternoon shutoff

Conditionsß Constant temperature ß Constant flow (on/off valves)ß Operates during the morning

and early afternoon

Advantagesß More uniform daily comfort

conditionsß Reduces peak energy chargesß Avoids building peak demand

charges

0.9 °C | 1.7 °F

Less variation than simple proportional controller

11 Oct 2019

Design/operation possibilities: Daytime shutoff

Conditionsß Constant temperature ß Constant flow (on/off valves)ß Operates only during the night

Advantagesß Low energy chargesß No demand chargesß Chilled water plant operates at

night, when dry- and wet-bulb temperatures are lowest

2.2 °C | 3.9 °F

More variation

12 Oct 2019

Design/operation possibilities: Constant flow

Conditionsß Constant supply temperature 4

°F higher than previous cases: 68 °F (20 °C)

ß Operates 24 hours per day

Advantagesß Low peak plant loadß Small chiller, low initial costß High supply water

temperatures

13 Oct 2019

Controls for radiant systems

14 Oct 2019

Overview of the controls (sequences publicly available)

ß First loop responds to slab temperature and controls the radiant zone valve

ß Second control loop adjusts slab setpoint once per day based on previous day’s zone conditions.

ß Choose enabled time period each day. Radiant system is disabled at all other times.

ß Heating or cooling mode separated by at least one day

ß Supplemental zone cooling/heating systems:ß Prioritizes radiant systemß Limits systems operating in opposing

heating/cooling modes on the same day

+

-

Zone valve controller Slab

Slab temp

Zone loads

Error

Slabsetpoint

Proportional controller

-

+

Comfortsetpoint

Error

Peak daily air temp

Preferred: Pulsed flowAlternate: Open/close

15 Oct 2019

Example cooling day operation from field study demonstration

ErrorIndoor air max

Reset slab SP atend of occupied hours

Indoor airSlabSlab setpointManifold valve

Comfort boundsSafety factor

Occupied periodEnabled period

80

75

70Te

mpe

ratu

re[°

F]

Off

On

0:00 6:00 12:00 18:00 0:00 0:006:00 12:00 18:00

16 Oct 2019

Example thermal comfort comparison in one zone

8 16Hour

Baseline Intervention

8 16

78°F

70°F

Daily air temperature profiles

17 Oct 2019

Example thermal comfort comparison in one zone

0.94°F

0.47°F

Average day-to-day variability

Intervention

8 16 8 16

78°F

70°F

Hour

Baseline

18 Oct 2019

8 16 8 16

78°F

70°F

Example thermal comfort comparison in one zone

12.3% 0.6%

InterventionExceedance percentage of total occupied hours

Hour

Baseline

19 Oct 2019

Sacramento Municipal Utility District East Campus Operations Center (SMUD)

ß Five story, 200K ft2

ß LEED Platinumß Low WWR and well shadedß Single tenant; 900 occupantsß Sacramento, CA

ß Cooling season weathersummary 2017-2019ß Max: 111°F ß Daily averages

• Mean: 74°F | Range: 30°F• Day-to-day variability: 2.7°F

20 Oct 2019

Baseline Intervention

Group A and B zones cool whenever

needed during the day or night

Group A zones cool only from morning to early

afternoon

Group B zones cool only during the night

ß Baseline: May – Nov 2017ß Controls implemented in Siemens

Apogee systemß Split zones into two groupsß Intervention: May – Nov 2018ß Compared results

Tested new control sequences

21 Oct 2019

SMUD radiant system thermal comfort performance in all zones

Variability: 0.42°FGroup A: 0.46°FGroup B: 0.35°FExceedance: 8.9%

Variability: 0.29°FGroup A: 0.28°FGroup B: 0.30°FExceedance: 1.1%

Baseline Intervention

22 Oct 2019

SMUD radiant system zone performance

Radiant system operationß Proxy for pump consumptionß Actuated far less timeß Daily average ON time

• Baseline: 2-4 hours• Intervention: 0.5 - 1 hour

ß Some days does not turn on at allMorning &Afternoon

Night

23 Oct 2019

Resources

Please share, use and give us feedback.

24 Oct 2019

Free webtool (steady-state performance): radiant.cbe.berkeley.edu

Applications:ß Heating and coolingß Floor and ceiling systemsß Radiant systems with and without

insulation and/or surface coveringsß Metric and I-P units

Calculates:ß Steady-state capacity (ISO 11855)ß Number of circuits, pipe length and

pressure drop

25 Oct 2019

Free webtool (transient performance): radiant.cbe.berkeley.edu

ß Transient results from over 2.5 million simulations

ß 13 user selectable design parameters incl. time and duration of operation

Outputsß 24-hour cooling day

design valuesß Surface heat fluxß Hydronic heat capacityß Operative temperature

26 Oct 2019

Controls publicly available in resources: radiant.cbe.berkeley.edu

ß Sequences of operation available

ß English language, editable Word document

ß Can be implemented in existing automation systems

ß EnergyPlus examples available

ß Available as a measure in OpenStudio

Resources

27 Oct 2019

Design concept leveraging thermal storage

28 Oct 2019

Example design concept leveraging thermal mass

Daytime (45-60 °F water)

Night-time (60-68 °F water)

ß All-electric: Air (or ground) source heat pump for heating and cooling

ß Dedicated outside air system (DOAS) and radiant can operate at different times and different temperatures, using the same heat pump

ß Reduced design capacityß Closed circuit cooling

tower (fluid cooler) for economizer operation

80-90% of annual radiant cooling

~50% of annual DOAS cooling

29 Oct 2019

Closing remarks

30 Oct 2019

Annual grid greenhouse gas emissions

Source: Recurve.

When solar panels generate power.

31 Oct 2019

Need for energy storage

ß Getting the storage we need to make the grid renewable is a huge challenge.

ß Storing energy in concrete is as cheap and easy as it’s going to get.

Source: Recurve.

32 Oct 2019

New HVAC designs should leverage inherent thermal storage

in buildings.

33 Oct 2019

Questions?

Paul Rafteryp.raftery@berkeley.edu

New design tools and controls for load-shifting with radiant systemsAcknowledgments OverviewInterviews with designersTrend data from a radiant building (in July)Motivation��How can we help designers �benefit from the load shifting potential�of radiant systems?�Slide Number 7Slide Number 8Slide Number 9Slide Number 10Slide Number 11Slide Number 12��Controls for radiant systemsOverview of the controls (sequences publicly available)Example cooling day operation from field study demonstrationExample thermal comfort comparison in one zoneExample thermal comfort comparison in one zoneExample thermal comfort comparison in one zoneSacramento Municipal Utility District East Campus Operations Center (SMUD)Tested new control sequencesSMUD radiant system thermal comfort performance in all zonesSMUD radiant system zone performance�Resources��Please share, use and give us feedback.Free webtool (steady-state performance): radiant.cbe.berkeley.eduFree webtool (transient performance): radiant.cbe.berkeley.eduControls publicly available in resources: radiant.cbe.berkeley.edu��Design concept leveraging thermal storage��Slide Number 28Closing remarksSlide Number 30Slide Number 31��New HVAC designs should �leverage inherent thermal storage�in buildings.��Questions?