Trigeneration systems based on heat pumps with natural refrigerants and multiple renewable sources.

Project Information

TRI-HP

Grant agreement ID: 814888

DOI

10.3030/814888

Project closed

EC signature date 21 March 2019

Start date 1 March 2019

End date 28 February 2023

Funded under

• SOCIETAL CHALLENGES - Secure, clean and efficient energy

Total cost

€ 4 993 080,00

EU contribution

€ 4 993 080,00

Coordinated by

OST - OSTSCHWEIZER FACHHOCHSCHULE
Switzerland

Periodic Reporting for period 3 - TRI-HP (Trigeneration systems based on heat pumps with natural refrigerants and multiple renewable sources.)

Reporting period: 2021-11-01 to 2023-02-28

Summary of the context and overall objectives of the project

The overall goal of the TRI-HP project is to develop and demonstrate flexible energy-efficient and affordable trigeneration systems. The TRI-HP systems are based on electrically driven natural refrigerant heat pumps coupled with renewable electricity generators (PV), using cold (ice slurry), heat and electricity storages to provide heating, cooling and electricity to multi-family residential buildings with a self-consumed renewable share of 80%. The systems developed include advanced controls, managing electricity, heat and cold in a way that optimizes the performance of the system and increases its reliability via failure self-detection. The flexibility was achieved by allowing three heat sources: solar (with ice/water as storage medium), ground and ambient air.
The innovations proposed are reducing the system cost by at least 10-15% compared to current heat pump technologies with equivalent energetic performances. Two natural refrigerants with very low global warming potential, propane and carbon dioxide, were used as working fluids for adapted system architectures that specifically target the different heating and cooling demands across Europe. The newly-developed systems were designed for both new and refurbished multi-family buildings, allowing to cover the major part of Europe’s building stock. TRI-HP systems reduce GHG emissions by 75% compared to gas boilers and air chillers.
Two system concepts were developed for two different combinations of heat sources, i) dual ground/air source and ii) solar with ice-slurry as intermediate storage. These two concepts combined with the two heat pump types developed (carbon dioxide and propane) have led to three complete systems (CO2-ice, propane-ice and propane-dual) that were tested in the laboratory.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

A system simulation framework has been further developed in python to build, run and process TRNSYS simulations. This python package has been made available in GitHub for the TRI-HP partners and it will be open to the general public during summer 2020 (https://pytrnsys.readthedocs.io/en/latest/)

A stakeholder process was carried out to better understand the conditions of market uptake of innovative heat pump systems in different European countries. The objective was to investigate key social and contextual factors that influence the social and market acceptance of renewable heating and cooling systems. The analysis included a literature review and in-depth interviews and stakeholders workshops with change actors in the heat pump markets in Germany, Switzerland, Spain and Norway. Among others, the perspective of heat pump manufacturers, HVAC planners, installers and building owners were taken into account. As a result, we could identify important barriers, drivers and incentives for the adoption of heat pump systems in general and innovative trigeneration heat pumps systems. Besides economic factors, such as high upfront costs, issues of practical implementation and feasibility emerged as important topics. Organisational factors, such as the cooperation between different trades on the construction site, or country specific heating cultures also turned out to be important issues.

We have developed three innovative heat exchangers:
• A compact and reliable supercooler (evaporator) for a heat pump for the solar ice-slurry system.
• A compact, highly-energy-efficient tri-partite gas-cooler as a single unit for a CO2 heat pump. Three heat exchangers were used with an 86 % reduction of weight (5 kg) compared to the 34 kg necessary with an helical counter-flow.
• A compact, highly-energy-efficient dual-source heat exchanger as a single unit for a propane heat pump with a direct heat exchange between brine/air and refrigerant.

Three natural refrigerant heat pumps were designed, manufactured and experimentally assessed. Two of them were designed using propane and one using CO2. One propane unit was using the dual source/sink evaporator/condenser. The other propane unit and one CO2 heat pump used the supercoolers with the icephobic coatings developed within the project. Moreover, the CO2 unit included the tri-partite gas cooler also developed within the project.

An efficiency drift self-diagnosis algorithm for the heat pumps to facilitate maintenance and increase reliability was developed and tested using experimental data of one of the propane heat pumps.
Besides this, an optimal advance energy management (AEM) system algorithm to minimize the energy cost and increase the renewable share was developed based on Model Predictive Control (MPC). The potential benefits of the AEM system was first assessed by means of simulation using different scenarios and conditions in a realistic setup using the pytrnsys simulation environment. Afterwards the AEM was implemented in a hardware and tested in the hardware-in-the-loop system test with a complete system.

Using the hardware-in-the-loop Concise Cycle (CCT) Test, we have demonstrated the autonomous operation of the complete TRI-HP systems in a relevant environment using the accelerated hardware-in-the-loop approach, including the integration of both thermal (heat pump, storage tanks, hydraulics and control) and electrical elements (battery, inverter, PV).
The cost-competitive advantage of solar-ice slurry TRI-HP systems over the conventional solar-ice with a synthetic refrigerant has been proven.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

One of the main progress achieved by TRI-HP was the development of natural refrigerant ice slurry heat pumps with the supercooling method using ice repellent coatings.
For the first time in Europe a supercooling ice slurry heat pump system for residential applications was proven in the laboratory providing a significant step forward in this technology.
Our simulations show that solar-ice slurry systems can have higher efficiencies at similar cost compared to state-of-the-art ground source heat pumps systems with several additional benefits.

A second innovation was the development of a dual evaporator/condenser for a propane heat pump able to use both brine/water and air as heat sources and sinks for heating and cooling respectively. The main progress was to develop a heat exchanger with direct exchanger between refrigerant and heat transfer fluid.

A third advance beyond the state of the art was the development of a tri-partite gas cooler for a transcritical CO2 heat pump, which was design as a very compact unit reducing weight by 86% compared to the previously tested spiral coil version.

The fourth progress beyond the state of the art was achieved at control level. Two main innovations were proven in the laboratory, an efficiency drift self-detection algorithm for the heat pumps to facilitate maintenance and increase reliability and an advance energy management system (AEMS) using model predictive control. The efficiency drift algorithm was proven to detect in the laboratory heat pump performance losses ≥ 10% with a response time lower than 10 minutes, resulting in an improved annual efficiency. The AEMS was experimentally assessed in the hardware-in-the-loop system test achieving a 16 % better heat pump efficiency and a 10 % reduction in system operation cost thanks to the optimization of heat pump use on low electricity price times benefiting from thermal storages to shift the heating and cooling demands.

logotype-complete-blue-eulogo.png

fig2-ice-slurry.png

heat-exchanger-teststand.jpg

fig1-dual-source.png

logotype-eulogo.png