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Fifth generation, Low temperature, high EXergY district heating and cooling NETworkS

Periodic Reporting for period 2 - FLEXYNETS (Fifth generation, Low temperature, high EXergY district heating and cooling NETworkS)

Période du rapport: 2017-01-01 au 2018-12-31

District heating networks are a competitive solution for the distribution of thermal energy to customers, especially for northern countries. Nevertheless, due to the typically high operating temperatures (about 90 °C), these systems suffer of relevant heat losses and unexplored integration potential of different available energy sources.
FLEXYNETS tackles these problems by focusing on the development of District Heating and Cooling (DHC) networks working at “neutral” (15-20 °C) temperatures, strongly reducing heat losses. Reversible heat pumps will be used to exchange heat with the DHC network on the demand side, providing the necessary cooling and heating for buildings.
Thanks to the low operating temperature, it will be possible to directly absorb waste heat from usually unexploited sources, like, e.g. supermarket chillers or data centers. Even the heat rejected for building cooling during summer will be fed into the network and recycled for the production of domestic hot water.
It is worth noting that, while in urban contexts not yet exploiting district heating these new networks could represent the main heating and cooling system, in cities already making use of traditional networks the two solutions could coexist. In particular, low temperature networks could be partly supplied by the return pipes of traditional networks. This would allow traditional utilities to sell additional energy with the same infrastructure and with higher generation efficiency, due to the lower return temperature to the supply station.

Project Objectives
FLEXYNETS pursues four main objectives.
First, to reduce transportation energy losses, using a carrier fluid working at a neutral temperature.
Second, to integrate effectively multiple energy sources.
Third, to exploit innovative thermal storage solutions, based on distributed systems.
Fourth, to develop control strategies and policies, allowing customers to be both energy consumers and producers.

Expected Results
The solutions proposed in FLEXYNETS will contribute to:
- Reduce primary energy consumptions and CO2 emissions for heating and cooling
- Integrate waste heat and renewables with proper storage solutions
- Widen the use of intelligent control systems
- Absorb electricity production peaks (due to renewables) through heat pumps
- Improve competitiveness of the European heating and cooling industry
The project is progressing well and is achieving the scheduled results.
A summary of the activities performed in the first 18 months is described in the following.
First of all, substations were defined by ACCIONA. A preliminary set of 10 cases were identified and for each of them a description of the corresponding equipment was given. A subset of a few major cases was then selected in order to carry out detailed simulations in TRNSYS. Simulation models were then developed for both residential and power supply substations by ACCIONA and EURAC.
The implementation of the FLEXYNETS-LOOP concept for a concentrating solar field was done by SOLTIGUA, which studied different cases with simulations. Two solutions to improve flow rate within collectors were compared, namely REC configurations (based on recirculating 3-way valves) and FLEXY configurations (based on on/off 2-way valves). Taking into account the yearly overall energy balance (including pumping consumption as well as solar gains), REC configurations came out to provide better performance and were hence implemented at the EURAC pilot plant, a laboratory specially developed for FLEXYNETS.
At the level of substations, an investigation about the use of large thermal storage systems in a low temperature context was provided by PLANENERGI.
PLANENERGI also carried out an analysis of possible city and settlement typologies, including a literature research and an applied survey on a set of cities in different countries. ‘Reference towns’ were generated for simulating the FLEXYNETS concept in different contexts, in order to understand the applicability of FLEXYNETS within a given environment. Moreover, this work provided the necessary input for the network simulation model simultaneously developed by ZAFH.NET.
On the side of the control system for the EURAC pilot plant, the work was focused on the development of low- and the high-level controls. On the hardware side, a new and cheaper version of a proprietary controller was developed by ENISYST. The control software platform for the EURAC testing facility was completed and delivered in a configurable form. For high-level control, the interaction between the management level and the substation level was discussed. Special effort was spent on the principle design of the management level as a server/cloud based solution and on the interaction between predictive simulation tools and weather forecast data.
Finally, possible interactions of FLEXYNETS with the gas and electricity networks were analyzed, in order to enhance the flexibility of the overall energy system.
The potential impacts of FLEXYNETS are broad and interesting.
FLEXYNETS could indeed contribute to strongly reduce the final energy consumption for space heating and cooling and water heating.

At a macro level, FLEXYNETS could contribute to the European Economy Recovery Plan and improve the competitiveness of the heating and cooling industry. For example, FLEXYNETS could boost the development of the heat pump sector.
The low adopted temperatures could allow the use of cheaper network pipes, thereby possibly compensating the additional investment costs for the introduction of heat pumps.
FLEXYNETS solutions could be suitable even for single city quarters. This would avoid complex political decisions involving the entire urban environment.
Finally, besides the environmental benefits, energy savings would correspond to lower energy bills for users. In addition, FLEXYNETS could create profit opportunities on a new heating and cooling market, transforming users into prosumers. This could be especially interesting for southern countries, where traditional DHC is less diffused and the FLEXYNETS reversibility would find a natural application.

At a more specific level, impacts about FLEXYNETS-Loops, Substations, Planning, Control and Trading are described below.
FLEXYNETS-Loop, a solution to enhance the productivity of concentrating solar collectors, will be placed on the EU and foreign markets within two years from the end of the project. The market will be selected according to the analysis of energy performances and prices made during the project.
FLEXYNETS-Planning production and utilization designs and their integration solutions will be made fully available. These elaborations could be used by engineering offices and researchers in order to plan DHC networks and develop further project results after the end of FLEXYNETS.
FLEXYNETS-Control development will be composed of three main findings: the software platform (copyright ENISYST), an investigation of possible solutions for a low-cost bi-directional heat meter, and the control strategies, that will be made public available through dissemination activities.
FLEXYNETS-Trading approaches and management rules will be made public available in order to stimulate their adoption by decision makers, service companies, general contractors and investors. In the medium term, these measures could be the basis for the development of a dedicated regulatory framework.