Stefan Brunold

In Switzerland the industry share of the total energy demand is 19 %. Half of this energy is used for the conversion to process heat and is mainly provided by fossil fuels [SFOE, Swiss national statistics 2014]. In a feasibility study the use of solar process heat by systems with solar thermal collectors therefore shows great potential and will in more detail examine the integration in the energy supply systems. In this study we restrict to a temperature range below 130 °C. For this purpose, it is necessary to identify the Swiss companies, which have the majority of the thermal energy consumption at temperatures below 130 °C. Furthermore, within the framework of the project, standardized system solutions for the planning and integration of a solar thermal system will be developed on the basis of three case studies. The focus lays on the yield calculation of the plant taking the location into account, the costs for the collector field and integration as well as the CO₂ savings by replacing fossil fuels through solar energy.

There is a lack of knowledge on the lifetime assessment of modern solar selective absorbers. In the project ColourAge, the performance and durability of different aluminium based coatings are studied. The combined effect of high humidity, condensation and temperature on the degradation of optical and chemical properties is assessed. Advanced techniques for materials characterization were used to identify the main degradation mechanisms: surface/interface (XPS, TEM) and chemical (EDX) analysis, as well as optical measurements (UV-Vis-NIR and FTIR spectroscopy).

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.

Together with TVP Solar and Planair SA, an industrial solar thermal system with innovative vacuum flat-plate collectors is being built in this project. A plant with a nominal output of 164 kW will be built on an area of 211 m², which will cover around 8% of the heat demand at the site. SPF's contribution includes multi-year monitoring, levelized cost of heat, energy and exergy calculations.

The aim of the project is the development of a single covered PVT collector with high electrical and thermal efficiency and a self-securing overheating protection realised by absorber shifting. An aluminium roll-bond absorber is used as heat exchanger, which enables good thermal properties on one hand and smart integration of the overheating protection mechanism on the other. The development includes the construction of a prototype on a scale of 1:1, its performance measurement in the laboratory and an assessment of its behavior when exposed on the test roof of the institute.

The service sector accounts for about 16 % of Switzerland's final energy consumption (GES 2017). More than half of the energy consumed in this sector is used to provide low-temperature heat (< 120 °C) for heating, hot water and process heat, which is mainly derived from fossil fuels. For this temperature range, solar heat is a suitable and proven technology, which has been known for a long time from the domestic sector. In the project SolInd2Service, the heat demand in different parts of the service sector is investigated and possibilities to integrate solar thermal systems will be identified.

Subsequently, best-case scenarios will be developed to demonstrate and facilitate methods for the implementation of solar thermal energy in the service sector.

A simple concept of a solar thermal drainback system is developed that can be used as add-on when refurbishing existing domestic hot water preparation in multi-family buildings. Three variants of the concept will be designed by means of energy simulation and calculation of levelized cost of heat. The most promising variant will be sized with thermohydraulic simulations and built in the lab. This demonstrator will be used to analyse and show safe operation conditions and the feasibility of the system concept.

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.

In the project HiPer-PVT we have developed a glazed (covered) PVT collector with a high electrical and a high thermal efficiency. Thanks to an overheating protection mechanism becoming effective at approximately 100 °C, this collector can be easily integrated into a thermal system. The concept of the overheating protection is that once the absorber reaches a predefined maximum temperature, it is brought into contact with the cover glass via a thermally activated lifting mechanism. This increases the heat losses and limits the stagnation temperature.

The interest in solar process heat for industrial applications is increasing worldwide. For future perspectives and realization of further solar collector fields an assessment of the current state is necessary.

Within the framework of the project EvaSP (Evaluation of solar process heat systems) funded by the Swiss Federal Office for Energy SFOE, several solar collector fields used for processes heat in different industrial branches are energetically and economically evaluated. This project will give an overview of the performance of these collector fields as well as suggestions for suppliers and planners. Furthermore, the results of this evaluation will aid entrepreneurs and investors in the decision-making process and support the implementation of solar thermal energy in industry.

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.

In this P&D project the potential of large PVT plants used for ground source regeneration is studied. The complex Oberfeld consists of three buildings. Each of the three buildings has its separate heating system containing heat pumps, earth probes and a PVT solar plant. The PVT plant is one of the largest of its kind in Switzerland. The entire PVT plant consists of a total of 799 PVT collectors and has an overall area of more than 1300 m², distributed over the roofs of the three buildings. The heat from the PVT plant is primarily used for ground source regeneration, but it can also be used to provide heat directly for the evaporator of the heat pump.

Within this 5 years P&D project the interaction of the entire heating system will be optimized and the long term temperature development and behavior of the ground source with solar regeneration will by observed.