Florian Ruesch

Heat storages can assist in the rational dimensioning and operation of thermal networks. They can smooth out peak loads and eliminate the need for fossil-fuelled peak load boilers. Heat surpluses can be stored temporarily. Decentralised storage systems can relieve the load on individual sections of the grid or enable grid densification and expansion. They are also ideal for the efficient integration of decentralised heat generators. This project aims to quantify potential cost and emission savings by implementing decentralised thermal storage systems in various district heating networks. The project will provide recommendations for the dimensioning and operation of these storage systems. Additionally, an Excel user tool will be developed to assist planners in determining the impact of storage systems on power distribution and thermal network costs.

Substituting fossil fuels with renewable energies will not be feasible without a notable expansion of seasonal energy storage. Seasonal thermal energy storages (STES) are expected to contribute significantly to this goal. The project SwissSTES systematically analyses STES potentials such as available and unused cavities, geothermal probe or pit storages and it develops novel STES technologies together with a systemic action and implementation plan for Switzerland. The highly interdisciplinary consortium brings together all relevant stakeholders from science, industry and society to promote the spread of STES in Switzerland. In this context, technical innovations but also social, legal and economic aspects play an important role. Furthermore, regional case studies pave the way for future pilot and demonstration projects throughout Switzerland.

Solar assisted district heating networks are booming in Denmark and are also progressing in Austria, Germany and Sweden. With these large solar thermal systems, low heat production cost below 5 Rp/kWh are reached. In this project, SPF supports district heating operators to find possibilities for the integration of solar heat in their network and analyses how large solar thermal installations can be optimally integrated in biomass heating networks in the Swiss context.

This project is the first to build, measure and optimise a recyclable asphalt collector for the regeneration of geothermal probes.

The background to this pilot and demonstration project is the increasingly dense use of geothermal probes, which leads to long-term cooling of the subsoil. Studies show that there is a considerable need for regeneration, particularly in urban areas. Asphalt collectors, which use heat from solar radiation on asphalt surfaces, are a potential cost-effective heat source for this regeneration. Initial pilot projects have shown that promising yields can be achieved with collector pipes embedded in asphalt. However, in these cases the asphalt was no longer recyclable. Based on simulations, it is assumed that it is also possible to lay the collector pipes in the underlying clean layer (separating layer between the subsoil and the asphalt surface) for the application of geothermal probe regeneration, thus maintaining the recyclability of the asphalt. This will be implemented and investigated in this P&D project.

The seasonal storage of heat in 100 % solar thermal heated single and multifamily buildings has been implemented in a number of projects in Switzerland. The first multifamily building with seasonal thermal energy storage that uses a combination of PV and heat pump instead of a solar thermal system is currently being built in Benzenschwil (AG/CH). In this project, concepts with solar thermal, solar electrical and combined solutions for 100% solar heating are compared, wherefore the entire lifecycle (LCA) of the different system is considered.

Within this project the potential of large thermal energy storages to facilitate the decarbonisation and simultaneous expansion of thermal networks are analysed. Different techniques of short-, medium- and long-term heat storage are considered. The focus is on the replacement of fossil peak load, the increased integration of waste heat, the shift of energy from summer to winter, and innovative approaches of sector coupling to balance production and demand of electricity.

The analyses are carried out on the one hand using representative generic thermal networks, and on the other hand for specific case studies of the participating industrial partners. In this way, generally valid results can be achieved, as well as a high probability to induce real pilot and demonstration projects.

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.

Geothermal heat pumps are efficient heating systems and therefore they can provide a substantial contribution to the reduction of CO2 emissions of the Swiss building park. In reverse operation mode, they can also cover the increasing cooling demand of buildings. However, the SIA 180 standard asks for passive measures to prevent overheating of buildings, even though active cooling could be covered by large extents with pv-electricity. In this project we analyze, under which conditions active cooling is energetically and economically beneficial, assuming elevated borehole regeneration fractions under consideration of entire districts.

Minergie 2017 and MukEn 2014 define framework conditions that lead to more solar collectors being installed or not. The project will clarify which factors are decisive for the choice and use of solar collectors. Based on the existing standards, fundamentals and tools are to be improved so that an increased use of solar heat can take place.

The aim of this project is the development of a fully configured and modular scalable solar thermal system for use in industry at various sites (production sites) and applications (heat sinks). For this purpose, a universally applicable smallest unit for heat supply is developed, which is adapted for the widest possible range of heat sinks. This unit consists primarily of a solar thermal heat generation system, and if applicable in combination with waste heat recovery and coupling to a district heating network. As an alternative to solar thermal, photovoltaics combined with heat pumps or possibly a combination of both approaches are investigated. Based on this, financing models are derived.

SPF has carried out three projects from 2017 – 2020 on the topic of Legionella in hot water systems. In the LegioSafe project (2018), a literature study was conducted on legionella, temperatures in drinking water systems, and the occurrence of legionella in systems with solar thermal water heating. In 2019, a field study was conducted including 110 buildings in «LegioSafeCheck». More than 300 shower water samples and over 100 samples from the lower area of heat water tanks were taken and analysed for Legionella. One year later, in the project LegioSafePlus, exclusively buildings in which legionella > 1000 CFU/L were found in at least one shower water sample in 2019 were further monitored and re-sampled. The results were made available for the standardisation work of SIA 385/1:2020 and are described in three final reports. Results of both field studies were summarised in an article published in «hk gebäudetechik». Due to installation deficiencies identified in the field, a leaflet on the correct combination of hot water circulation and central cold water admixture was produced with the help of suissetec, GKS and Swissolar as well as EnergieSchweiz.

Fully solar heated single and multifamily houses are already technically feasible. The seasonal storage in these systems is associated with corresponding investment cost and demand for storage volume. This project analyses whether cost and used storage volume can be reduced with the combination of solar thermal with a PV driven heat pump system. Therefore, an existing system will be monitored and new innovative concepts are simulated and optimized. The project is carried out in collaboration with Lucerne University of Applied Sciences (HSLU) and Jenni Energietechnik AG.

Requirements and possible sites in Switzerland

The Drake Landing Solar Community has raised worldwide attention, when covering 100% of space heat for an entire quarter of single family houses with a concept of solar thermal collectors and a central borehole storage. In this project it was analyzed weather a similar concept can be realized in Switzerland. Therefore the legal conditions were summarized and the economic requirements were evaluated. A GIS based analyze shows, which locatios are specially suited for such a concept based on solar irradiation and geological conditions.

Solar assisted district heating is widely used in countries as Austria, Germany and Sweden and is booming in Denmark. Heat production costs below 0.05 CHF/kWh where recently reached. With this feasibility study district heating networks of the canton of St. Gallen are analyzed in terms of the feasibility and the cost-benefit ratio of an integration of large solar thermal collector field. A further goal is to make contact between collector manufacturers and network operators as well as to initiate the realization of several large collector fields.

SWSG is supported by the canton of St.Gallen and the Swiss Federal Office of Energy (SFOE).

The are no universal guidelines or thresholds for reflected sunlight in the public space. In this project, physical parameters for an objective description and quantification of a «discomfort glare» from reflected sunlight are elaborated. Furthermore, the scattered reflection (bidirectional reflectance distribution function, BRDF) of several glass types and other materials of the building envelope is measured in order to generate an extensive database. This database can help to evaluate the «discomfort glare» from solar installations and other surfaces of the building envelope already in the planning phase. New materials or surfaces can be compared with standard materials of the database in order to assess their effect concerning glare from reflected sunlight.

Low temperature district heating networks, in which borehole fields serve as seasonal storage on a low temperature level for efficient decentralized heat pumps, are emulated in dynamic simulations. Based on the analyses of existing networks, means for optimizing the energy efficiency by global regulation strategies or the use of new renewable energy sources will be proposed.

This project receives funding from the Swiss Federal Office of Energy SFOE and is carried out in cooperation with the industry partners Amstein+Waltert AG and Vela Solaris AG.