Flexible cooling & heating solution deployed in two sites for greater energy efficiency

One of the biggest challenges of HVAC systems is that heating or cooling energy needs to be generated on demand when the need occurs.

HeatTank Thermal Battery system, developed by HeatVentors, is a solution to produce heating or cooling energy when it is the most efficient, when it is the cheapest, or when waste heat sources or renewable energy sources are available, making it a smart solution for retrofitting existing buildings.

This technology has been deployed in two of the StepUP pilots for improving thermal comfort and increase the energy efficiency of a kindergarten in Budapest, Hungary, and multifunctional building office in Pamplona, Spain.

Degasification achieved in the Budapest Pilot

View of the installation of HeatTank thermal battery in Zóld-Liget Kindergarten

In the Budapest pilot, four pieces of the HeatTank were integrated to the newly constructed heating system relying on two heat pumps. In this pilot, the HeatTank solution served to showcase the degasification potential of the system. 

A classic challenge of degasification is the high supply and return temperatures of the gas boilers. Even when the topic is changing the old gas boiler to a condensation gas boiler (that is more efficient), the heating temperatures can be challenging.

When the heating system (radiators) are designed to for example 80 °C supply and 60 °C return temperatures, decreasing the supply to 60 °C and the return to 40 °C will decrease the heating power of the radiators by about 40%. With a heatpump with 40 °C supply and 30 °C return temperature the heating power decrease is 70%. The result is not this problematic, as it only refers to the design condition state. 

In the kindergarten, a unique solution was used. While renovating the radiator system, a parallel fan-coil system was installed, providing the missing power to the building. On the other hand, this fan-coil system also enables the use of the cooling option of the heat pumps. 

The efficiency of the evaluated boiler depends on the heating temperature (which varies with the weather, with lower outdoor temperatures leading to higher heating temperatures) and the part load of the boiler. With HeatTank, the heating system can operate at its best efficiency. 

The operation strategy and the saving concepts are similar for cooling system, when the external temperature is lower, the cooling efficiency is higher.

The HeatTanks are influencing the needs of the heating/cooling system by adding extra consumption (charging increases the load so the partial load will increase to reach better efficiency) or by supporting the heating/cooling energy production (discharging lowers the partial load, setting an optimal level of operation).

Optimised cooling system in the Spanish Pilot

Installation of the HeatTank in ACR multiuse building

The objective of this pilot was to integrate a cooling system with storage capacity into the existing HVAC system without direct connection to the refrigerant circuit. This was achieved through air-based cooling, demonstrating that it is possible to cool a server room efficiently in terms of electrical consumption.

The HVAC system of the multiuse building was a Variable Refrigerant Flow (VRF) system that provided heating and cooling to various areas of the building.

The key to the integration was the HeatTank, a tank capable of storing cool though Phase Change Materials (PCM). To transfer cool air (provided by an inner HVAC system) to the tank, a heat exchanger converts the cold air to water, which is then stored in the HeatTank. This process is carried out during off-peak electricity hours, optimizing energy consumption.

When cooling is required in the server room, the discharge heat exchanger activates to extract the cold water from the HeatTank and transfers it to the server room, effectively cooling the space.

System components

The system is composed of the following components:

  • HeatTank: a PCM cooling tank.
  • Compact Unit: comprised of an inner HVAC unit, which provides the cool air, and a heat exchanger that converts air into water for storage in the HeatTank.
  • Discharge Heat Exchanger: located in the server room, responsible for providing cooling by using the stored cool from the HeatTank.

Key outputs

  • System Viability: It has been demonstrated that the installation of this innovative technology is both feasible and effective.
  • Development of a Compact Unit: For the first time, a compact unit has been developed that combines the internal HVAC unit and the charging heat exchanger.
  • Potential for High-Cooling-Demand Applications: This technology shows significant potential for environments where cooling demand is constant and high, such as server rooms and data centres.
  • Foundations for New Solutions: This prototype lays the groundwork for designing innovative cooling solutions for buildings, addressing a growing need.

Author: HeatVentors


This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 847053.

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