Design Aspects for Large-Scale Aquifer and Pit Thermal Energy Storage for District Heating and Cooling Pit Thermal Energy Storage (PTES)

Per Alex Sørensen PlanEnergi,

INTERNATIONAL ENERGY AGENCY TECHNOLOGY COLLABORATION PROGRAMME ON District Heating and Cooling including Combined Heat and Power 1 Investment cost analysis presented in review report

400 *) water equivalent volume: ] Tank (TTES) Hanover WE Pit (PTES) 350 Hamburg SM: storage medium Borehole (BTES) W: water 300 ΔT: usable temperature difference Aquifer (ATES) **) monetary value 2017 Others Munich 250

Friedrichshafen 200 Eggenstein Chemnitz Neckarsulm 1 150 Crailsheim Okotoks, CA Marstal-1, DK

100 Attenkirchen Neckarsulm 2 Dronninglund, DK Marstal-2, DK Toftlund, DK 50 Braedstrup, DK Gram, DK Vojens, DK

Rostock Investment cost** per m³ water equivalent* [€/m³ per water equivalent* m³ cost** Investment 0 1 000 10 000 100 000 1 000chart: 000 Solites Graph: Solites Storage volume in water equivalent* [m³WE]

INTERNATIONAL ENERGY AGENCY TECHNOLOGY COLLABORATION PROGRAMME ON District Heating and Cooling including Combined Heat and Power 2 The Danish PTES Storage concept

Original objective: To develop cheap thermal storages >50,000 m3 for high solar thermal fractions. That means:

• Soil balance

• Polymer solutions

• Floating lid

• Insulation only in lid

• Water as storage medium

Present objective: to use the storages at 90 oC constantly in 20-30 years

INTERNATIONAL ENERGY AGENCY TECHNOLOGY COLLABORATION PROGRAMME ON District Heating and Cooling including Combined Heat and Power 3 Why use the Danish PTES concept?

Advantages: • Quick charging and discharging. Can be used as peak shawer • Can be utilized also as short time storage • A closed construction • Water as storage medium means good stratification and high thermal capacity/m3 • The same storage can be used as hot water and cold water storage at the same time because it is possible to have cold water in the bottom and hot water in the top due to the inherent stratification • Relatively low construction cost where suitable ground conditions exist

Disadvantages: • Land area required can be difficult to find in urban centres • Lifetime of liner material and lid construction still being demonstrated • Higher construction costs in areas having high ground water levels and where excavated soil is not suitable for use in the bank construction • Maximum temperature 90 oC, due to liner material properties.

INTERNATIONAL ENERGY AGENCY TECHNOLOGY COLLABORATION PROGRAMME ON District Heating and Cooling including Combined Heat and Power 4 PTES Project Example Dronninglund, Denmark

Name of the project: Sunstore 3. In operation from 2014 Location: 9330 Dronninglund, Denmark Owner: Dronninglund Fjernvarme Size of storage: 60,000 m3 Smart District Heating combining heat generation with solar thermal, CHP and heat pumps

Dronninglund and Marstal

HP CHP

35 – 40 000 m² Buffer storage Load/ user STES 50 – 100 000 m3

Graph: PlanEnergi Photo: Dronninglund Fjernvarme

INTERNATIONAL ENERGY AGENCY TECHNOLOGY COLLABORATION PROGRAMME ON District Heating and Cooling including Combined Heat and Power 5 Monitoring results 2018-19

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INTERNATIONAL ENERGY AGENCY TECHNOLOGY COLLABORATION PROGRAMME ON District Heating and Cooling including Combined Heat and Power 6 Temperature stratification 2018-19

Dronninglund 2018-2019 Temperatures - monhtly! mean values 100

90

80

70

60

C 50 °

40

30

20

10

0 Jun 2018 Jul 2018 Aug 2018 Sep 2018 Oct 2018 Nov 2018 Dec 2018 Jan 2019 Feb 2019 Mar 2019 Apr 2019 May 2019

Tbottom Ttop Tmean Linear (Tbottom)

INTERNATIONAL ENERGY AGENCY TECHNOLOGY COLLABORATION PROGRAMME ON District Heating and Cooling including Combined Heat and Power 7 Data for Dronninglund

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INTERNATIONAL ENERGY AGENCY TECHNOLOGY COLLABORATION PROGRAMME ON District Heating and Cooling including Combined Heat and Power 8 Design aspects, polymer liners

Polymer liners (PP or HDPE). Be aware of

▪ Moisture diffusion

▪ Oxygen diffusion

▪ Lifetime exposed to water and to air

▪ Price for liner and mounting

▪ Welding and testing procedures for leakages during mounting

▪ Guarantees

▪ Repairs during operation period

INTERNATIONAL ENERGY AGENCY TECHNOLOGY COLLABORATION PROGRAMME ON District Heating and Cooling including Combined Heat and Power 9 Design aspects, insulation

Insulation material. Be aware of:

• Moisture resistance and possible regeneration from wet

• Thermal expansion

• Pressure resistance

• Price for insulation and mounting

• Guarantees

• Possible to repair during operation?

INTERNATIONAL ENERGY AGENCY TECHNOLOGY COLLABORATION PROGRAMME ON District Heating and Cooling including Combined Heat and Power 10 Design aspects, lid

Lid. Be aware of:

▪ How to get rid of rain water and avoid ponds on the lid

▪ How to get rid of air produced when heating up PTES water

▪ Moisture ventilation

▪ Oxygen diffusion to PTES

▪ Thermal expansion

▪ Price for materials and mounting

▪ How to repair during operation

INTERNATIONAL ENERGY AGENCY TECHNOLOGY COLLABORATION PROGRAMME ON District Heating and Cooling including Combined Heat and Power 11 Design aspects, water quality and in- and outlet

Water quality and quality of in- and outlet. Be aware of:

• Water must be softened

• Salts must be removed (reverse osmosis)

• Water quality (salts, oxygen, conductivity) must be frequently monitored and

• In- and outlet must be in non-corrosive materials if water contains oxygen (stainless steel was used in Dronninglund)

INTERNATIONAL ENERGY AGENCY TECHNOLOGY COLLABORATION PROGRAMME ON District Heating and Cooling including Combined Heat and Power 12 New projects in Denmark. 90 oC constantly

Høje 70.000 m3

▪ Liner work in Høje Taastrup is expected to be finalized in July 2020 and the storage will be ready 1st September 2021

▪ Call for tender September 2020. 2x 500.000 m3

▪ Call for tender end of 2020. 450.000 m3 and 550.000 m3

INTERNATIONAL ENERGY AGENCY TECHNOLOGY COLLABORATION PROGRAMME ON District Heating and Cooling including Combined Heat and Power 13 Thank you for your attention!

Contact: Per Alex Sørensen [email protected] www.planenergi.dk

INTERNATIONAL ENERGY AGENCY TECHNOLOGY COLLABORATION PROGRAMME ON District Heating and Cooling including Combined Heat and Power 14