M&E design and modelling of large systems Keith Horsley ... · Hoare Lea Energy Strategy November 2006 Energy consumption and heating & cooling loads from IES model Hydrogeology input

www.hoarelea.comNovember 2010

Ground Source Heat Pump AssociationTechnical Seminar 2nd November 2010

M&E design and modelling of large systemsKeith Horsley – Associate, Hoare Lea

www.hoarelea.comNovember 2010 www.hoarelea.com

One New Change

32,000m2 high grade office

20,500m2 high grade retail

2 open loop wells

Over 200 energy piles

13 ground source heat pumps

1.7 MW capacity


Introduction

Overview of building energy modelling and load estimation

One New Change:Energy strategy and energy modellingSpecification of the ground source energy systemDeveloping the operating strategy for the ground source energy system


Modelling building loads

CIBSE Guide A, section 5 - cyclic calculation over 24 hours.

“Rules of thumb”W/m2 heating and cooling loads in the early stages of design

Results used to size boilers and chillers.But of limited use for designing ground source energy systems.



To correctly size LZC energy systems such as GSES, and to estimate their contribution, annual energy consumption and annual heating and cooling loads are needed.

The energy benchmarks in CIBSE Guide F and TM46 are useful... but not perfect!



Increasingly, the driver for LZC energy systems is a planning requirement for a “renewable energy contribution”, usually as a percentage of the building’s energy demand or carbon emissions.But what is the “renewable contribution” of a ground source heat pump?

0.5MWh elec in

2.0MWh gas in

Boilers

Air-cooled chillers

“Renewable contribution” = 2.0+0.5-1.0 = 1.5 MWh

1.0MWh elec in

1.8MWh heat out

2.0MWh cooling out

GSES



To refine the analysis of LZC energy systems, heating and cooling load profiles are needed.

Degree days give an approximation for heating.

The NCM activity database gives part of the picture.

But more research is required to provide better data.



Building geometryBuilding fabric propertiesGlazing / shading propertiesInfiltrationOccupancyEquipment heat gainsLighting heat gainsVentilation ratesPlant efficienciesControls

Dynamic simulation models


One New Change

Client – Land SecuritiesConcept architect – Jean NouvelDelivery architect – Sidell GibsonConstruction Manager – Bovis LendLease

M&E engineer – Hoare LeaStructural engineer – ArupGSES specialist – Geothermal International


One New Change

32,000m2 high grade office20,500m2 high grade retail55,000m2 total over 11 storeys

Start on site mid-2007Completion October 2010


One New Change

Planning requirement for 10% of the development’s energy usage to be from renewable or low carbon technologies


One New Change

Hoare Lea Energy Strategy Report – May 2005

Energy consumption at One New Change

(Baseline scenario - without contribution from renewable or low carbon energy sources)

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

7,000,000

8,000,000

Offices Retail

Estimated annual

electricity consumption

Estimated annual gas

consumption

Es

tim

ate

d e

nerg

y c

on

su

mp

tio

n (

kW

h/y

r)

Energy consumption estimated based on benchmarksGSES yield and efficiencies estimatedGSES “renewable contribution” = 14%


One New Change

Hoare Lea Energy Strategy November 2006

Energy consumption and heating & cooling loads from IES modelHydrogeology input from ArupHeat pump efficiencies from manufacturersInitial design for 5 borehole pairs + energy piles to meet 10.17% of energy demand

0

1000

2000

3000

4000

5000

6000

7000

8000

Annual energy

consumption, MWh

Annual heating load,

MWh

Annual cooling load,

MWh

Retail

Office


One New Change

Heating and cooling loads

RETAIL OFFICE

Retail condenser loopOffice LTHW system

Office CHW system


One New Change

Final energy strategy submission – January 2008

0

200

400

600

800

1000

1200

1400

Retail heating Office heating Office cooling

Annual load, MWh

Annual load met by GSES,

MWh

Energy input, conventional

plant, MWh

Energy input, GSES, MWh

"Renewable contribution",

MWh

Energy consumption and heating & cooling loads from IES modelGSES input from Geothermal International – number of boreholes reduced; number of energy piles increasedGSES meets 10.93% of energy demand

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

Office Retail


One New Change

How the GSES was specified

“Renewable energy contribution” (kWh per year) the key performance requirementSpreadsheet included in specification to show how this was calculatedAcknowledgement of difference in performance between initial period and future yearsRequirement for GSES contractor to model the system performance based on the heating and cooling load profiles generated by IESMinimum annual COPs for each load connection pointStandalone control system for GSES with open protocol interface to CNS & BMSEmphasis on metering and monitoring to allow control strategy to be optimizedDesign responsibilities itemised for all parties (Hoare Lea, Loopmaster, Geothermal International and Arup)


One New Change


One New Change

The output of the GSES is restricted by:

Peak heating and cooling capacitiesTotal kWh heating or cooling from the ground per dayYield of the open loop wells per dayAvailability of the dry coolers

Also affected by:

External temperature (Can directly cool condenser loop? Cool ground loop?)Condenser loop set point temperature (varies with external temperature)Ground water temperature (Can directly cool condenser loop?)


One New Change

The control system takes into account:

Total condenser system kWh cooling load the previous dayTotal condenser system kWh heating load the previous dayTotal Office CHW kWh cooling load during the previous dayTotal Office LTHW kWh heating load during the previous dayCurrent outside air temperatureMet office weather data (forecast of min and max temps for next 2 days)The total kWh available today from the open loop (based on open loop temperature and maximum daily yield)Variation with outside air temperature of the efficiency of each heating and cooling generator (from factory and site test data) so the available heating or cooling capacity of the ground loop system is used to displace the least efficient device.


Conclusion

Estimation of annual building energy loads and load profiles are important for the appropriate application and design of ground source energy systems

Important to revisit as the design of the building, and the GSES, develops

Dynamic simulation modelling essential for complex buildings, but choice of appropriate assumptions and interpretation of results not straightforward

Consultants’ specifications need to be clear on what is required from whom.

The control and operation strategy is important to ensure the contribution of the ground source energy system is maximised

www.hoarelea.comNovember 2010

Documents

M&E design and modelling of large systems Keith Horsley ... · Hoare Lea Energy Strategy November 2006 Energy consumption and heating & cooling loads from IES model Hydrogeology input