Traditionally, District Heating and Cooling (DHC) networks distribute energy from a centralized generation plant to a number of remote customers. As such, actual DHC systems suffer from:

• Significant heat losses

• Highly unexplored integration potential of different available energy sources (e.g. renewables and waste heat) into the network

• High installation costs.

FLEXYNETS will develop, demonstrate and deploy a new generation of intelligent district heating and cooling networks that reduce energy transportation losses by working at “neutral” (15-20°C) temperature levels. Reversible heat pumps will be used to exchange heat with the DHC network on the demand side, providing the necessary cooling and heating for the buildings.

In this way, the same network can provide contemporary heating and cooling.

Moreover, the heat normally rejected by buildings (for example through a common split unit), will be fed into the network by the heat pumps (which are working in “cooling mode”) and recycled by other heat pumps that are producing domestic hot water.

In the same way, these networks allow to recovery and recycle waste heat available along the network path, even at very low temperatures, contrary to traditional District Heating Networks, that can harvest thermal energy only at high temperature (greater than 100°). Following this logic, it is possible to reuse also the waste heat e.g. from supermarkets’ chillers, data centers and several industrial processes.

Moreover, working at low temperatures reduces the heat losses to the ground, increasing the network efficiency.

This system does not substitute nor is opposed to traditional district heating networks.

In urban contexts not exploiting district heating yet, this new generation networks can represent the main heating and cooling system.

In cities already making use of district heating, low temperature DHC networks can use thermal energy from the return pipes (in addition to waste heat), which otherwise is considered as waste heat by the network utility. This allows them contemporarily to sell additional energy with the same infrastructure and makes the network more efficient, reducing the return temperature to the station.

The project is organized in different work packages, where the main topics are: (i) analysis and simulation of possible substations (including optimized solar solutions), (ii) analysis of possible network configurations, (iii) development of proper control strategies and smart metering solutions, and (iv) testing in dedicated laboratories.

Two laboratories will be exploited, a Spanish laboratory managed by Acciona and an Italian laboratory under development at Eurac. The Spanish laboratory is focused on tri-generation technologies. The Italian laboratory is being developed at Eurac and will be directly designed to test network related aspects, focusing on distributed generation and low-temperatures solutions coupled to heat pumps. At the same time, the Eurac laboratory will include cogeneration equipment and a solar field.

The laboratory being developed at Eurac is directly designed to test the Flexynets concepts in conditions as close as possible to a real application. It will therefore comprise several substations, including:

• A piping network for the distribution of heat and cold. The network will be designed taking into account the multiple connections with the heat sources and sinks. Different types of pipes will be considered, aiming at testing various insulation conditions.

• A small trigeneration system for the production of heat, cold, and electricity. This system is an example of the kind of waste heat sources which can be considered in the innovative low-temperature DHC concept. The availability of a trigeneration system will allow to deal with real issues, like network management strategies and variable temperature of the sources.

• Reversible heat pumps to simulate the network users: at the moment are planned up to 10 network users.

Although the main goal of the laboratory is to test low temperature networks, the laboratory will be built to make possible testing (in stationary and dynamic conditions) also:

• Control logics for traditional high temperature (up to 100°C) networks

• Individual technologies for the production of cold and heat such as boilers, absorption and compression refrigerators, cogenerating units with thermal power up to 100 kW.

So it will be possible to provide consulting to companies interested in testing their equipment, in a broad range of operating regimes.

Both research in general and the laboratory in particular are addressed to:

• District heating networks operators.

• Equipment and components for district heating networks producers that are interested in testing their products in pseudo-real conditions.

• Local administrators interested in developing policies dedicated to encourage the use of low temperature waste heat and in making more efficient the traditional district heating networks.