Cooling with ground source heat pumps – lessons learned from South-Eastern Asian countries

Kasumi Yasukawa1, Isao Takashima2,

Youhei Uchida1 and Gaurav Shrestha1

1 AIST

2 Akita University

Index

Introduction:

✓Why GSHP cooling in South-eastern Asia?

✓concerns in application of GSHP in South-

eastern Asia

Temperature survey

Demonstration projects

Summary

Why GSHP cooling in South-eastern Asia?

Increasing population, expanding industry

Urban heat island phenomenon

➢ Endless increase of electricity demand especially for cooling.

➢ Saving energy for cooling is essential in this region!

Concerns in application of GSHP in

South-eastern Asia

1. Is GSHP applicable in tropical region?

(temperature condition)

2. Is heat exchange rate sufficient? (for closed loop

systems)

3. Is drilling without cementing technically possible

by a local driller?

Introduction

GSHP is used worldwide, but is it applicable everywhere?

Cold

Moderate

Tropics

1. Is GSHP applicable in tropical region?

Monthly average atmospheric and subsurface temperature

Not really in tropics… They need cooling system, but underground is warm.

But it may be applicable in

tropical region if;

• Subsurface temperature is

rather low in the region

and/or

• Cooling demand of the

building is mainly in

daytime.

Introduction

Heat flow

coldheated

Subsurface temperature affected by groundwater flow

At recharge zones (high elevation), subsurface

temperature is lower than at discharge zones.

Underground can be used as cold source at

recharge zone, and may also be in the mid-plain.

Subsurface temperature profile with groundwater

flow in different zones of a plain/basin

1. Is GSHP applicable in tropical region?Introduction

2. Is heat exchange rate sufficient?

(in the heat exchange borehole)

Geology of the most basins and plains in South-eastern

Asia are unconsolidated sediments.

Since unconsolidated sediments have lower heat

conductivity than hard rocks, heat exchange rate in a

borehole must be low.

Therefore longer total drilling length is necessary in this

region. Higher drilling cost -> low cost performance

Is it real?

Introduction

Heat exchange affected by groundwater flow

In monsoon Asia, groundwater level in basins and plains are generally

high, and a saturated sediment has a high “effective heat conductivity”.

In addition, advection effect of groundwater flow may give even higher

“apparent heat conductivity”.

2. Is heat exchange rate sufficient?

Heat Conductivity (HC) of Rocks

A) “heat conductivity”: HC of dry rock

B) “effective HC”: HC of saturated rock

C) “apparent HC”: HC measured at field

with advection effect of groundwater

flow => actual heat exchange rate

➢ In water saturated zones, A<B<C

Introduction

So, even higher heat exchange rate than hard rock may be achieved!

Heat exchange with advection effect of groundwater flow

3. Is drilling without cementing technically

possible by a local driller?

To take advantage of advection effect of groundwater flow, a bare

borehole is needed as the borehole heat exchanger: no cementing,

no casing, and no bentonite mud circulation (formation of mud

cake blocks the groundwater flow).

But in South-eastern Asia, where unconsolidated sediments is

dominant in plains and basins, drillings have been done with

bentonite circulation, cementing and casing to avoid collapse of the

borehole.

Drilling with polymer is a solution.

Can it be done by local drillers?

Introduction

Introduction: Concerns in application

of GSHP in South-eastern Asia

1. Is GSHP applicable in tropical region?

2. Is heat exchange rate sufficient? (for closed loop system)

3. Is drilling without cementing technically possible by a local drilling company?

The answers to these three concern are shown in the following sections.

Introduction

Index

Introduction:

✓Why GSHP cooling in South-eastern Asia?

✓concerns in application of GSHP in South-

eastern Asia

Temperature survey

Demonstration projects

Summary

Subsurface TemperatureProfiles in Thailand

Bangkok

Ayuthaya

Nakhon Sawan

PitsanulokSukhothai

Kanchanaburi

Temperature

survey

Recharge zone

Recharge zone

Discharge zone

Intermediate zone

Discharge zone

Bangkok

Ayuthaya

Nakhon Sawan

Sukhothai

Kanchanabu

ri

Pitsanulok

subsurface (depth:0-50ｍ)

--- annual mean

Temperature

surveySubsurface vs. atmospheric temperature in Thailand Monthly Ave.

Minimum

Monthly Ave.

Maximum

Subsurface

Ref: Yasukawa et al., 2009

Subsurface temperature around Hanoi, Vietnam

Subsurface temperature profiles measured in observation wells in Hanoi region

Temperature

survey

Ref: Yasukawa et al., 2009

• In Hanoi region, GSHP system

may show higher performance

for space cooling than in

Bangkok due to bigger difference

between atmospheric and

subsurface temperature.

• Winter in Hanoi is cool and humid.

GSHP heating may also be used

in the winter for heating/drying.

Temperature

survey

✓Is GSHP applicable in tropical region?: Yes, at least based on temperature survey results.

Even in Bangkok, a discharge zone, subsurface temperature is lower in daytime in hot season.

✓But is it really applicable? OK, let’s do demonstration experiments!

Subsurface temperature vs. atmospheric temperature in Hanoi region

Index

Introduction

Temperature survey

Demonstration projects

Summary

GSHP Demonstration Projects in S-E AsiaPlace Period Subsurface Heat

ExchangerSurfaceSystem

Note

1. Kamphaengphet(DGR), Thailand

2006.10 –2008.3

57 m deep boreholewith double U-tube

Water-water chiller, fan coil

First experiment in tropic.Mostly made in Japan.

2. Ciang Mai (DGR), Thailand

2008.3 -2010.7

80 m deep boreholewith single U-tube +60 m horizontal tube

Same as above Moving the above system to another site.

3. Bangkok (KasetsartUniv.), Thailand

2010.7 -2012 ?

200 m horizontal tube Same as above Moving the above system to another site.

4. Bandung (ITB), Indonesia

2013.7 -2015?

200 m horizontal tube Remodel fromair-cond.

Cooling efficiency 25 % up (first comparable data).

5. Bangkok (Chulalong-korn Univ.), Thailand

2014.5 – 50 m deep boreholewith single U-tube x 3 (150 m)

Combined chiller& fan unit

Confirmation of highperformance.

6. Bandung (Western Java Energy Mineral Institute), Indonesia

2015.3 –2016?

100 m deep borehole with single U-tube

Remodel fromair-cond.

Heat exchanger made in Indonesia.

7. Sarabri (Chulalong-korn Univ.), Thailand

2015.6-2016.11-

300 m horizontal tube300 m horizontal tube

Combined chiller& fan unit

Machine made in ThailandRemodel from air-cond.

8. Pathumthani(Geology Museum, DMR) Thailand

2015.3 50 m deep borehole with double U-tube x 2 (400 m)

Combined chiller& fan unit

Mostly made in Japan.No cementing borehole for higher heat exchange.

9. Hanoi (VIGMR), Vietnam

2016.10- 50 m deep borehole with double U-tube x 2 (400 m)

Combined chiller& fan unit

Mostly made in Japan.No cementing borehole for higher heat exchange.

Blue: AIST and Akita Univ., Black: Akita Univ. … and local institute or university

Demonstration

Projects

Case 1: First GSHP experiment in tropical Asia with borehole heat exchanger in

Kamphaengphet.A GSHP system was installed at DGR office for room air-conditioner.

System performance and subsurface heat exchange capacity were monitored

over a year.

Demonstration

Projects

Experiment (Oct. 2006 -)

The room to be cooled

• Borehole was completed with normal

cementing and casing.

• Temperature change in the borehole and the

surroundings were monitored.

• All materials except for surface piping were

imported from Japan.

Heat pump

Borehole

Heat

Exchanger

Heat exchanger

(double U-tube)

Demonstration

Projects

Result of experiment in Kamphaengphet

System COP of 3 was achieved during stable operation period.

COP = provided heat / electricity consumption= (Toutlet – Tinlet)×Q2 / We

COP

HP operation temperature

Cooled room temperature

Outside temperature

Original room temperature

Demonstration

Projects

Result of experiment in Kamphaengphet

Result

Cooling system worked well and at a stable operation period

after adjustment of controlling temperature settings of the heat

pump, system COP of 3 was achieved.

Lessons learned:

To be economically feasible, careful setting and adjustment of

the HP parameters are necessary for higher performance.

In this experiment, the temperature of circulation fluid has risen

which reduces COP. For higher COP, a) a longer heat exchanger

and b) a borehole without casing/cementing is needed.

For cost reduction, use of local material is needed.

Demonstration

Projects

Experiment at Chulalongkorn University (from May 2014)

Second Presidential Office

(Right Hand Side is for Drilling)

Second Floor for Experiment

(Room Size: 2.8mX4.7m)

Case 5: Efficiency comparison with old system at Chulalongkorn University, Bangkok.

Demonstration

Projects

Drilling and Pipe Setting (Feb. 2014)

Drilling for 50m

Mud Flow by Drilling Cuttings Check for Geology

PE Pipe Setting to 50m Depth (100m length)

Just after 2 Drillings/Pipings

Recover Now (July 2014)

U-tube: only the end part is from Japan

Demonstration

Projects

Well 1

(10m+15m)

Well 2

(50m)

GHP

Outer

Unit

System Outline

Room for Cooling

GHP

Inner

Unit

Old AC

Data Logger

HP by Colona Co.

Demonstration

Projects

26

27

28

29

30

31

4 8 14 196 7 20 26 27 28August 2014

25

Cooling Operation of GHP and Old Air Conditioner

200W/h

800W/h

600W/h

400W/h

Atmospheric Temperature Room Temperature (Start 10am Stop 4pm, 6hrs)

Temp. (oC)

• 6 hour operation per day

• comparison not at the same time

Air Conditioner

GHP

by Sasimook Chokchai,

Chulalongkorn Univ.

Demonstration

Projects

GSHP cools the room more efficiently

than the old air conditioner

(1) Ratio of Average Power Consumption:

(213+293+423+357+203)/(615+667+702+695+573)=0.458* (Save 54%)

(2) Underground Heat Exchange Rate : 1.42oCx25 L/min.=35500cal/min.=2473W

(2473/150m=16.5W/m)

(3) COP: 2473Wx0.7?(Heat Exchange Efficency)/297.8W=5.8

* Correct old AC efficiency: 1489/(3252x0.68)=0.673 (Save 33%)

Cooling Operation of GHP and Old Air Conditioner Aug. 2014, 10:00-16:00 (6 hours)/day

Yellow Italic is Data of Old Air Conditioner by Sasimook Chokchai,

Chulalongkorn Univ.

Demonstration

Projects

33% higher efficiency than new air conditioner was confirmed!

Case 7: GSHP with Horizontal Heat Exchanger in Churalongkorn Univ., Saraburi.

Objective is cost reduction for drilling

Upper left：

Heat exchanger

of carpet styleUpper right：

Heat exchanger

of coil style

Lower left：

Ground source

heat pump

Lower right：

Fun coil unit in

office

June, 2015

Demonstration

Projects

Results of the experiment in Chulalongkorn University, Bangkok and Saraburi

Comparison of the performance with a new air-con was done in

Bankok as the first time.

Local material for heat exchange pipes are used in both Bangkok

and Saraburi. The pipe connection caused small leakages.

Horizontal system in Saraburi shows OK performance (may not be

as good as vertical system, but good cost performance).

Lessons learned

GSHP system in Bangkok showed 33% higher efficiency than a

new air-con.

For installation cost reduction, effective combination of

horizontal and vertical system is recommended.

Case 8: Golden Jubilee National Geological Museum, DMR, Pathumthani

Demonstration

Projects

DGRの掘削機（利根ボーリンク製）

泥水の比重計測

錘とUチューブを接続

Installation of pipe

GSHP unit

Heat Exchangers (50m deep)

Demonstration

Projects

Fun coil unit of GSHP system

室内機

Souvenir shop at 2nd Floor

ResultImprovement achieved

➢ Heat exchanger pipes were connected by Electric Fusion System to avoid

leakage.

➢ Thai crews drilled two heat exchangers with 50m depth: no cementing, no

casing for higher heat exchange rate.

Necessary improvement

➢ Drilling with mud circulation was conducted: it took one week to be

completed, including the time for washing away the mud cake (bentonite).

Demonstration

Projects

Master plan of system arrangementFCU : Fun Coil Unit

HP : Ground Source Heat Pump

HX : Borehole type heat exchanger (50m depth)

Case 9: VIGMR, Hanoi, Vietnam(October, 2016)

Vietnam Institute of Geoscience and Mineral Resources (VIGMR)

Demonstration

Projects

Results➢ VIGMR completed drilling of two heat exchangers (50m deep) in three

days, with Synthetic Polymer as drilling mud, which it easy to use.

(Same system arrangement as the one in Geological Museum in Thailand.)

Lesson Learned:

✓ Drilling borehole without bentonite, cementing or casing can be done by

local driller efficiently, by using polymer as mud fluid.

Drilling machine (no casing, no cementing for higher heat exchange rate)

Demonstration

Projects

Preparation of heat exchange pipeInstallation of pipe from 2nd floor

GSHP unit Fun coil unit in DG’s room

Demonstration

Projects

In Hanoi, heating system is not common. It’s nicely warm in cold season!

Summary

Acknowledgement➢ These collaboration researches have been done under CCOP Groundwater Sub-

Project “Development of Renewable Energy for GSHP System in CCOP Regions.”

• Experimental operation of GSHP systems for cooling only has beenconducted in Thailand, Indonesia and Vietnam.

• To be economically feasible, careful setting and adjustment of thesystem parameters are necessary to get higher performance withhigher electricity savings.

• High performance has been confirmed at a test site in Bangkok.

• System with local manufacturing would be a key for cost reduction.

• Cost performance may be optimized by selection of horizontal orvertical heat exchangers depending on local subsurface condition.

• Drilling technology (no cementing, no casing, no bentonite) wouldbe a key for higher heat exchange rate by vertical borehole.