Dr. Daniel Carbonell

A solar-ice heating system was designed and installed as part of a pilot and demonstration project. Since 2017, the heating system is supplying a residential and commercial building of 2050 m² of energy reference area with space heating and hot water. The main components of the heating system are 120 m² of unglazed, spectrally selective solar collectors, an ice storage tank with 210 m³ volume, and a two-stage brine-to-water heat pump with 45 kW thermal output (B0/W35). The heat exchangers in the ice storage tank are periodically de-iced in winter and could therefore be designed with a small transfer area.

To complete the deployment of the ice slurry technology using the supercooling water, modelling and design tools for the scalability of crystallizers are required. These tools may ensure a controlled and reliable operation of crystallizers, avoiding upstream ice propagation and exergetic losses, and high-efficiency supercooling release. To achieve this, ModIceCrys aims to develop a CFD-crystallization tool for modelling the ice crystallization process coupled with supercooled water flows. As a first step, the ice crystallization processes in supercooling water will be numerically investigated using the population balance model to obtain a stand-alone crystal growth model in non-flow conditions. Thereafter, a coupled fluid flow and the above-mentioned crystal growth model will be coupled by means of CFD in order to understand the fundamentals of ice growth and its interaction within supercooling water flows. To conclude, the validation of the previous CFD-crystallization model via diverse non-intrusive quantitative flow visualization techniques, such as Particle Image Velocimetry (PIV) and Backlight Shadow Imaging (BIS), is foreseen.

The project HT-PCM aims at providing a feasibility study of using phase change materials (PCM), e.g. erythritol, as storage solution for temperature ranges in between 110 °C to 120 °C. The storage concept is designed to be integrated with solar thermal collectors to provide solar process heat to industries. The proposed PCM solution is expected to decrease cost, achieving a latent energy density in the range of 80 kWh per m³ of storage volume at a cost lower than that of synthetic oil.

In this project, we develop smart planning methods and control strategies for solar neighbourhoods, in order to make optimal use of solar energy, storage solutions, and the interconnection of buildings via electrical and thermal grids. A focus is on the winter heat supply, and alternatives to air/water and geothermal heat pump systems. Exploiting synergies and sector coupling at the neighbourhood scale shall allow to reduce the carbon-intensive winter electricity demand and to provide a high load and production flexibility towards the electricity grid.

The technical approach is to develop efficient computational models that allow a) to compare a large number of system variants in the design phase with regard to different objective functions (costs, emissions, grid flexibility) and b) to realise model-predictive control strategies on a neighbourhood scale.

Within the project Ice-Grid possible application of ice-storage tanks in low temperature thermal networks will be analyzed. In combination with other storages, ice-storage tanks can help to shift the availability of heat or cold. As latent heat can be used at 0 °C within an ice storage, this type of storage is of particular interest regarding the coverage of future cooling requirements. The integration of ice storage tanks into expanding networks with limited sources, such as low temperature waste heat, will be investigated. For analyzing the effects and comparison with state of the art components generic low temperature thermal networks are simulated, and different variants compared.

Within the OptimEase project, a modelling framework is developed that allows for the energetic optimization of groups of buildings by using their synergies. By comparing the optimal solution of a group of buildings with the sum of optimal solutions for each individual building, the economic and environmental benefits of aggregating several buildings is evaluated.

Thermocline is a cost efficient thermal storage system able to reduce capital costs of CSP up to 40 %. The objective of this project is to develop new thermocline concepts that can be applicable to different CSP plants. Detailed simulation of two thermocline concepts will be validated with the experimental data generated in this project. Based on the simulation tools, both concepts will be evaluated and optimized in terms of system integration and LCOE savings on a CSP system level and up-scaling for CSP target applications.

Reducing heat losses from existing residential buildings by refurbishing the building envelope is an important step to reduce the heating demand of buildings. In the EU project PLURAL, prefabricated façade modules are being developed and tested, which enable novel possibilities for energy generation, heat/cold supply and ventilation with the façade. The prefabrication of the façade modules is intended to enable rapid and cost-effective refurbishment in an inhabited state. Three field installations will be used to demonstrate renovations in different European climates. Simulations will be used to analyse components and buildings, and a Big Data management platform and decision-making tool for component selection and integration will be developed.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 958218.

In «Slurry-Hp I» we have shown the potentials of cost reduction of using the ice slurry technology with the supercooling method for solar-ice applications. First work on supercoolers was done in «Slurry-Hp II» and it is currently being developed in the «H2020 TRI-HP». «Slurry Store» will work towards the development of an ice slurry storage concept for this application. Several options for charging (icing) and discharging (melting) the slurry storage will be experimentally evaluated and a design will be proposed. Last but not least, an ice releaser (cristallizer) to ensure a continuous ice slurry production will be implemented in the laboratory set-up for a capacity of 5 kW.

The SolResHC project addresses research questions related to IEA PVPS Task 16 regarding "Solar Resource for High Penetration and Large Scale Applications".

Specifically, impacts of different weather scenarios on solar heating and cooling are assessed. Simulations for various future scenarios are carried out to determine the impact of weather data on the energy efficiency of different systems providing heating, cooling, domestic hot water and partly electricity for a multi-family house.

Furthermore, the influence of large feed-in from PV and other renewable energies to the electricity grid in Switzerland is analysed with a particular focus on the electricity price.

In SolSimCC, the effects of climate change and user behaviour on the profitability of solar energy systems (photovoltaics and solar thermal) were investigated. The results show only a minor influence of climate change on the profitability of solar plants. However, two changes significantly increase the profitability of solar thermal systems: firstly, the replacement of natural gas with more expensive biogas or syngas, and secondly, the adoption of more realistic heat consumption profiles instead of the idealised profiles often used in simulations today.

Soltherm2050 answers the question of the potential of solar heat in combination with thermal energy storage in Switzerland, identifies the best possible application areas, assesses the opportunities and risks and finally develops a roadmap for promotion and to expand these technologies. The goal is to make the greatest possible contribution to the Energy Strategy 2050, with a focus on a realistic implementation process.

The overall goal of the TRI-HP project is the development and demonstration of flexible energy-efficient and affordable trigeneration systems. The systems will be 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 innovations proposed will reduce 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, will be used as working fluids.

The project is lead by SPF and supported by the research programme H2020 of the European Union – grant agreement ID: 814888

The overall goal of the project is to assess and quantify the potentials of solar-ice systems for multi-family buildings with the possibility to include cooling demands. Special emphasis will be given in quantifying the energy performance using different hydraulic configurations and weather data sets on several Swiss locations. Hundreds of parametric transient dynamic simulations in TRNSYS will be used to quantify the system performance factor under different boundary conditions. The project also aims to develop fast algorithm tools for feasibility checks purposes using machine-learning algorithms trained with TRNSYS simulations.

The idea behind this project is to use the supercooling ice slurry method for solar heating applications. This innovative concept could provide a breakthrough in solar and heat pump systems with ice storages by reducing the cost of the system by 10 %. The cost reduction would be achieved by eliminating the heat exchangers from the ice storage and storing ice in the form of slurry. The slurry HP II project aims to proof the concept of heat exchangers operated with supercooled water using ice repellent coatings.

The goal of the present project is to analyse the technical and economic feasibility of a solar-ice system based on a super-cooling slurry heat pump. The system should achieve higher electricity savings and overall system performance with a comparable return on investment with respect to state-of-the-art ground source heat pump and solar-ice solutions. The anticipated efficiency increase is based on the super-cooler heat exchanger which is always free of ice. The anticipated cost reduction is based on the use of very simple storage vessels that do not need build-in heat exchangers.

Slurry-HP is financed by the Swiss Federal Office of Energy (SFOE).

Ice storages in combination with solar thermal collectors and a heat pump to provide domestic hot water and space heating demands (solar-ice systems) are a promising technology. The project IceEx aims at characterizing heat exchanger concepts for ice storages in solar heating applications. Several heat exchangers, available on the market or recently developed for solar-ice systems, are analyzed by means of experiments and simulations to find an optimum design. Transient yearly simulations are used to assess the system efficiency and energy demand.

This project is financed by the Swiss Federal Office of Energy (SFOE).