District Cooling Concepts Applied in China.”

“District Cooling Concepts applied in China.”

Bernt Andersson

District Cooling 2016 a Climate Solution Dubai, November 2016

Very limited development of District Cooling systems, first systems developed early 2000; Standard approach for cooling is split units for apartments and building or block level chilled water plants; Indoor design temperature is +26 C (77 F) For District Cooling systems a combination of compression chillers, absorption chillers and Ice Thermal Energy Storage are common; Almost all District Cooling plants with Ice Thermal Energy Storage have dual duty, single evaporator chillers and large heat exchangers between the glycol circuit and chilled water circuit for day time operation as well as heat exchangers between the Ice Thermal Energy Storage and the chilled water circuit; In almost all cases where both District Heating and District Cooling are developed the pipe network is two pipe system that are used for heat supply in winter and cooling supply in the summer;

[email protected] Mean Monthly Temperature Climate Zones Coldest Hottest Severe Cold ≤ -10 °C ≤ 25 °C Cold -10–0 °C 18–28 °C Temperate 0–13 °C 18–25 °C Hot Summer and Cold Winter 0–10 °C 25–30 °C Hot Summer and Warm Winter > 10 °C 25–29 °C Source: Berkely Labs [email protected] Compression Chillers with Ice Thermal Energy Storage Concepts Best Practice Dual duty chillers with two evaporators where the chilled water evaporator is connected in series with the directly connected Thermal Energy storage; Provide the highest daytime COP at the same time as utilising low night time electricity;

Common solution in China Cooling Towers CWR 11 C 11 C Dual duty chillers with single HEX CCWR

evaporator, large heat exchangers Compression District Cooling Water Chillers Network Loop & Dual Duty between the glycol circuit and Chillers CCWS

chilled water circuit for day time 2.5 C CWS operation as well as heat exchangers 2.5 C 2.5 C 11 C between the Ice Thermal Storage 1 C 9 C

and the chilled water circuit; Ice Thermal Storage Result in a lower COP;

BCS BCR

[email protected] Absorption & Compression Chillers with Ice Thermal Energy Storage Concepts Absorption Chillers added to the production mix Steam or Hot Water Condensate Return

In some cases there are 7C Absorption Chiller discussions about using steam 11 C or hot water from existing Cooling Towers CWR power plants as base load 11 C production of chilled water; 11 C CCWR

Compression Then using dual duty chillers District Cooling Water Chillers Network Loop & Dual Duty with ice thermal storage for Chillers CCWS

peak production; 5.0 C CWS 1 C

1 C 5.0 C

Ice Thermal Storage

BCS BCR

[email protected] Absorption & Compression Chillers with Ice Thermal Energy Storage Concepts

Cooling Towers Absorption Chillers also cooling the condensers on compression chillers In one case there is even a

Steam or Hot Water discussion to use an existing Condensate Return

district heating pipeline as 7C

Absorption transmission line for chilled 20 C Chiller water in the summer and put the absorption chillers at the power

CWR plant 35 km away; 11 C CCWS In that case the concept is to

Compression move the cooling towers out of District Cooling Water Chillers Network Loop & Dual Duty the down town area and use the Chillers

return water from the consumers CCWR 4.0 - 5.0 C CWS to cool the condensers of the 1 C chillers and the absorption

chillers will cool the common 1 C 5.0 C return from consumers and Ice Thermal Storage chiller condensers; The aim is to use the

compression machines as heat BCS BCR pumps in the winter season; [email protected] Comparison of three alternative Plant solutions

Dual duty, twin compressor, double evaporator with ice TES; Dual duty, single compressor, double evaporator with ice TES; Dual duty, single compressor, single evaporator with HEX and ice TES;

Optimisation of ice TES size for the three Plant solutions

Five different sizes of ice TES capacity has been analysed; Depending on ice TES capacity the plant configurations has been modified to fit each one of the cases; 16 different plant scenarios has been developed and analysed;

[email protected] Sizing of Chilled Water Plants with Thermal Energy Storage is a complex task;

DISTRICT COOLING DAILY LOAD PROFILE STORAGE LOAD, Discharge mode

200.0 70.0

180.0 60.0 160.0

140.0 50.0 120.0

100.0 40.0

80.0 MW

Cooling demand MW demand Cooling 30.0 60.0

40.0 20.0 20.0

0.0 10.0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Thermal Storage Load Compression Chiller Operation as water chiller

Glycol Chillers in operation to Charge Storage Absorbtion Chiller Load 0.0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Total System Load

Annual Load Curve ENERGY IN STORAGE 200,000 400.0 180,000 350.0 160,000

140,000 300.0

120,000 250.0

100,000 kW

MWh 200.0 80,000

60,000 150.0

40,000 100.0 20,000 50.0 - 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 0.0 District Cooling Load 34 % of DC annual energy supplied by TES 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

[email protected] Most economic operation on a 55% of peak day, but practical?

DISTRICT COOLING DAILY LOAD PROFILE ELECTRICAL TARIFF

1 120.0

0.9 100.0 0.8

0.7 80.0

0.6 60.0

0.5

Cooling demand MW demand Cooling 40.0

RMB/KWh 0.4

0.3 20.0

0.2 0.0 0.1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Thermal Storage Load Compression Chiller Operation as water chiller

0 Glycol Chillers in operation to Charge Storage Absorbtion Chiller Load 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Total System Load

STORAGE LOAD, Discharge mode ENERGY IN STORAGE

120.0 600.0

500.0 100.0

400.0 80.0

MWh 300.0

60.0 MW

200.0 40.0

100.0 20.0

0.0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 0.0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 [email protected] Dual Duty, twin Dual Duty, Single Dual Duty, single Mode of compressor, compressor, compressor, Single duty Load opeartion double double single evaporator Chillers evaporator evaporator with HEX CW mode COP 100% 5.48 4.96 4.723 5.321 Ice mode COP 100% 3.61 4.09 3.98 -

Percentage of TES Capacity Single duty Dual duty Chillers; chilled water/iceDedicated ice making chiller Annual Energy Water Chillers Supply # of units Total Capacity # of units Total Capacity # of units Total Capacity CW mode/Ice mode % MWh MW MW MW No TES 0% 0 21 184.8

Ice TES 34% 407 6 52.8 9 79.2/56.7

Ice TES 39% 467 4 35.2 10 88/63 1 1.76 Ice TES 41.6% 500 4 35.2 10 88/63

Ice TES 45.2% 552 4 35.2 9 79.2/56.7 2 12.6 2 3.52 Ice TES 52.7% 675 3 26.4 9 79.2/56.7 5 31.5 2 3.52 [email protected] The day tariff is about 4 times the night tariff;

Electrical Energy Cost Chillers 60

45 Million RMB Million 40

30 0 407 467 500 552 675 Dual Duty, single compressor, single evaporator with HEX Dual Duty, Single compressor, double evaporator

Dual Duty, twin compressor, double evaporator Single duty Water Chillers

[email protected] The difference in investment is up to 12% higher for the single evaporator with HEX ;

Investment in Cooling Plant 530

480

430

380 Million RMB Million

330

280 0 407 467 500 552 675 Dual Duty, single compressor, single evaporator with HEX Dual Duty, Single compressor, double evaporator Dual Duty, twin compressor, double evaporator Single duty Water Chillers

[email protected] As the size of ice TES increases the 25 year LCC is reduced;

25 year Life Cycle Cost 115%

110%

105%

100%

95%

90%

85%

80% 0 407 467 500 552 675 Dual Duty, single compressor, single evaporator with HEX Dual Duty, Single compressor, double evaporator Dual Duty, twin compressor, double evaporator

[email protected] We concluded that the 25 year LCC goes down with increased ice TES sizes but does it make sense to have such large TES?

25 years incremental IRR on addtional investment 23%

21%

19%

17%

15%

13% IRRon additionalInvestment 11%

7% 407 MWh 467 MWh 500 MWh 552 MWh 675 MWh Percentage of Annual Energy supplied from Ice TES

Dual Duty, twin compressor, dual evaporators Dual Duty, single compressor, dual evaporators Dual Duty, single compressor, single evaporator with HEX

To answer this question we looked at the incremental investment between a chiller only plant and each one of the ice TES cases with the different chiller configurations and compared to the 25 year benefit generated and the resulting IRR; Financial analysis for the best case with expected tariff levels and technical performance;

South China Project Cash Flow 800,000

600,000

400,000

200,000 RMB1000 x

- 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035

-200,000

-400,000

Annual Net Cash Flow before financing Accumulated Net Cash Flow before financing

[email protected] The most sensitive parameter is that predicted revenues for the project is achieved, a combination of price level and amount of energy sold;

Sensitivity Analysis ROI 20.0%

19.0%

18.0%

17.0%

16.0%

15.0%

14.0%

ReturnInvestmenton % 13.0%

12.0%

11.0%

10.0% Investment +/- 10% Electricity price +/- 10% Operation & Maintenance Revenues from sales +/- +/- 30% 10%

[email protected] The combined solution with absorption chillers, compression Heat Pump/Chillers and ice TES and no cooling towers in the down town area is a very interesting concept; The conclusion from the comparison of alternative plant solutions is that dual duty solutions provide better economics; The optimal size of TES is specific for each and every project and are depending on electrical tariff structures and local circumstances; The key to all District Cooling developments are to match the ramp-up of connection of buildings to the staging of installation of plant capacity;

[email protected] Thank you! [email protected]