HOT|COOL NO. 4/2019 - "Components"



By Finn Bruus, team leader, VEKS and Per Alex Sørensen PlanEnergi

The purpose of the project is fourfold: 1. To develop and demonstrate a PTES that can be operated in a more flexible and advanced way than has been seen to date. Thus, allowing charge and discharge of energy at a daily and weekly basis allowing flexible electricity production from CHP plants and peak shaving in large DH systems. 2. To develop and demonstrate new innovative technical solutions that can solve some of the necessary challenges needed to bring the PTES technology an important step further towards fully commercial scale used as accumulation tank in large DH systems. 3. To demonstrate, that the PTES can replace a similar steel tank and be implemented for less than 1/3 of the costs for a steel tank. The price for the PTES is expected to be 300 DKK/m3 (40 €/m3) compared with app. 1,000 DKK/m3 (133 €/m3) for a steel tank with the same capacity. In addition, costs for connections to the district heating network and pumps must be added for both the PTES and the steel tank. 4. To develop an optimization system for a PTES in a large DH system with a large number of stakeholders (heat producers and consumers). Implementation of the demonstration project will open a new huge market for PTES as a viable tool for DH systems to be effective integrators of fluctuating renewables. It will be demonstrated that the temperature in the upper part of the storage can be constantly fixed at 90°C making them able to replace the more expensive steel tanks. The objective is to make this possible by change of liners, insulation materials and design. Also, it will be demonstrated how advanced operation creates synergy between heat and electricity markets. A comprehensive monitoring program is part of the project. The construction work started June 2019 and the PTES will go into operation in autumn 2021. The construction starts with connections to DH networks, buildings for pumps and heat exchangers and after that the excavation work for the PTES will start.

This article gives an introduction to the “FLEX_TES” 70,000 m3 pit heat thermal storage (PTES) project, where the PTES will be demonstrated in a new function as accumulation tank in a district heating (DH) system with combined heat and power (CHP) from biomass and incineration. The energy content of the PTES will be 3,300 MWh. The use of the PTES means that energy production will increase on CHP and incineration plants, and there will be an optimization towards the electricity price. The electricity price varies, with the variation in wind and solar-based electricity production, but also with the hydro- power production in the countries around DK. In hours with high renewable electricity production, electricity prices are low, and the PTES must cause electricity and heat production to be transferred to plants with relatively low electricity production and vice versa. Furthermore, heat peak load production will be replaced by discharge from PTES. In the future, heat production will be transferred to electricity consuming technologies, such as large electricpowered heat pumps for DH, in hours where the electricity price are relatively low.

The PTES will be owned 50 % by transmission company VEKS and 50% by Høje Taastrup District Heating Company.

The project is supported by the Danish research and development program EUDP.

THE PURPOSE OF THE PROJECT The PTES will be demonstrated in Høje Taastrup DH Company’s distribution system but connected to the large VEKS´ transmission system (Fig 1) as part of the integrated DH system in Greater Copenhagen. This makes it possible for all the CHP plants in the transmission systems of VEKS and CTR to interact with the storage.


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