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A new dynamic method for solar collector testing is developed. It is characterized by using the Laplace transformation technique to solve the differential governing equation. The new method was inspired by the so called New Dynamic Method (NDM) (Amer E. et al (1999) [1]) but totally different. By integration of the Laplace transformation technique with the Quasi Dynamic Test (QDT) model (Fischer S. et al (2004) [2]), the Laplace – QDT (L-QDT) model is derived. Two experimental methods are then introduced. One is the shielding method which needs to shield and un-shield solar collector continuously during test period. The other is the natural test method which doesn't need any intervention. The new L-QDT model with the shielding method are tested by TRNSYS (Klein S. et al (1988) [3]) simulation. Experiments were carried out at Technical University of Denmark by using the L-QDT method and the natural experimental method. The identified collector parameters are then compared and analyzed with those obtained by the steady state test method and the QDT test method. The results comparison shows that the L-QDT method and the natural experimental method are also valid. It can be concluded that the new Laplace test method can obtain reasonable and accurate collector parameters under transient weather condition. [ABSTRACT FROM AUTHOR]

• An experiment of SGHP system and the detail description of combi-storage are presented. • Five daily operation modes are identified using the contributions of the energy inputs. • The dynamic thermal behaviors of the combi-storage are investigated and analyzed. Experimental investigations on thermal behavior of a combined solar and ground source heat pump (SGHP) system for a single-family house are presented. The SGHP system was installed at the Lyngby campus of Technical University of Denmark. Detailed experiments were carried out on the system in 2019 under real weather conditions covering domestic hot water (DHW) consumption and space heating (SH) demand. Depending on the contributions of the energy inputs to the combi-storage, five typical daily operation modes are classified. The focus of the investigations is on the dynamic thermal behaviors of the heat storage under different operating conditions. When the combi-storage was primarily heated by solar energy, the inlet stratifier in the storage performed well, ensuring thermal stratification and a good utilization of solar energy. Water temperature in the storage reached up to about 68℃ at the end of the solar heating process. When the combi-storage was primarily heated by the ground heat, the water temperature near the outlet for SH was kept at a temperature range from 26℃ to 31℃ in the heating process to ensure the outlet temperature level of SH, and the water temperature near the outlet for DHW was in the temperature range 47℃∼51℃ in DHW volume. When there was no heat input to the combi-storage, the pre-stored heat can meet the daily heating demand, and the number of days on this mode was up to 9.4% of the total experimental days. The paper gives valuable inputs for researchers and engineers who plan to integrate the combi-storage in a renewable heating system with solar collectors and ground source heat pumps. [ABSTRACT FROM AUTHOR]

This paper presents experimental investigations on a combined solar and ground source heat pump (SGHP) system for a single-family house. The SGHP system was installed at the Lyngby campus of Technical University of Denmark with horizontal ground heat exchanger (HGHE). Detailed experiments were carried out on the system in 2019 under real weather conditions and the heating demand for domestic hot water (DHW) and space heating (SH). The focuses of the investigation are energy flow analysis and performance assessment on the SGHP system. The results showed that the yearly system seasonal performance factor of the SGHP system (SPF SHP) was 2.8, and the maximum monthly SPF SHP was up to 5.7 in April with the highest solar radiation. Directly utilized solar energy for the combi-storage was 500 kWh lower than the annual solar heat for charging the ground, and it accounted for 36.6% of annual heat input of the combi-storage, the rest of the heat was supplied by the heat pump system that consumed 84% of total electricity energy. Different from the large fluctuations of monthly solar fraction due to solar radiation, the monthly renewable heat fraction was within the range from 57% to 83%, and the yearly value was 65%. [ABSTRACT FROM AUTHOR]

• Comprehensive analysis of country-specific boundary conditions and success factors. • National heat supply systems and incentive policies are essential. • Role of district heating utilities in Denmark for solar district heating success. • Technological solutions and best practice examples of large-scale systems. • First-hand market research on China shows higher market penetration than assumed. Large-scale solar thermal systems are a cost-efficient technology to provide renewable heat. The rapid market growth in the last decade has been concentrated on a small number of countries, with the outstanding position of Denmark followed by China, Germany and Austria. This paper provides a comprehensive overview of the market and common technological solutions for large-scale solar thermal systems in these countries. Country-specific factors, including solar resources, heat supply systems, competing technologies, promotion schemes and business models, which put these countries in a leading role, are analyzed in detail using an integrated assessment framework. For each country, a best practice solar heating system is introduced. The analysis shows that heat supply by large-scale solar thermal systems is a mature technology with a broad field of applications and that mainly country-specific boundary conditions regarding the heat supply system and incentive policy are responsible for the preeminent role of these four countries. The unique role of district heating utilities in Denmark, which are subject to a national emissions trading system and often act both as investors and operators of large-scale solar thermal systems, can serve as a role model for other countries. [ABSTRACT FROM AUTHOR]

• Solar assisted heat pump system with buffer tank as source for heat pump. • Uncovered photovoltaic-thermal collector used to charge buffer tank in periods without irradiance. • Transient simulation model validated with experimental measurements. • Yearly performance of system including parameter variation. • Modulating heat pump with thermal mass modelled via scale factor and extra pipes. Solar thermal energy systems combined with heat pumps are becoming popular solutions for covering space heating and domestic hot water demand in European Union households. There is a great potential for developing high performing systems by combining components in systems in new ways. This study focuses on the performance of a system consisting of heat pump, photovoltaic-thermal solar collector and two storage tanks. This system is proposed to potentially have better performance compared to air-to-liquid heat pump system while being less costly compared to a liquid-to-liquid heat pump system with ground sourced heat exchanger. The system was set up at the Technical University of Denmark in 2017, for providing domestic hot water. A simulation model of the system was created in the transient simulation software TRNSYS and the data from the experiment were used for its validation. The modulating heat pump was modelled via a function applied to the scale factor and the thermal mass of the heat pump was taken into account by including additional pipes around the heat pump. The performance of the system was assessed using selected key performance indicators. A parametric analysis was performed identifying component sizes that improved the system's performance. The improved system produced 55% more electricity, had 23% lower electric consumption and wasted 11% less heat by minimizing heat losses compared to the demonstration system. The improved system had a solar thermal fraction of 0.58, a solar electrical fraction of 1.51 and a renewable energy fraction of 0.75. The system was however oversized compared to the load applied to the system as it was built to cover only domestic hot water demand. For the system to be economically attractive it must cover a larger load. [ABSTRACT FROM AUTHOR]