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Up to now biorefinery concepts can hardly compete with the conventional production of fossil-based chemicals. On one hand, conventional chemical production has been optimised over many decades in terms of energy, yield and costs. Biorefineries, on the other hand, do not have the benefit of long-term experience and therefore have a huge potential for optimisation. This study deals with the economic evaluation of a newly developed biorefinery concept based on superheated steam (SHS) torrefaction of biomass residues with recovery of valuable platform chemicals. Two variants of the biorefinery were economically investigated. One variant supplies various platform chemicals and torrefied biomass. The second variant supplies thermal energy for external consumers in addition to platform chemicals. The results show that both variants can be operated profitably if the focus of the platform chemicals produced is on high quality and thus on the higher-priced segment. The economic analysis gives clear indications of the most important financial influencing parameters. The economic impact of integration into existing industrial structures is positive. With the analysis, a viable business model can be developed. Based on the results of the present study, an open-innovation platform is recommended for the further development and commercialisation of the novel biorefinery.

Within the last decade, research on torrefaction has gained increasing attention due to its ability to improve the physical properties and chemical composition of biomass residues for further energetic utilisation. While most of the research works focused on improving the energy density of the solid fraction to offer an ecological alternative to coal for energy applications, little attention was paid to the valorisation of the condensable gases as platform chemicals and its ecological relevance when compared to conventional production processes. Therefore, the present study focuses on the ecological evaluation of an innovative biorefinery concept that includes superheated steam drying and the torrefaction of biomass residues at ambient pressure, the recovery of volatiles and the valorisation/separation of several valuable platform chemicals. For a reference case and an alternative system design scenario, the ecological footprint was assessed, considering the use of different biomass residues. The results show that the newly developed process can compete with established bio-based and conventional production processes for furfural, 5-HMF and acetic acid in terms of the assessed environmental performance indicators. The requirements for further research on the synthesis of other promising platform chemicals and the necessary economic evaluation of the process were elaborated.

Many installed solar thermally driven cooling systems suffer from high auxiliary electric energy consumption which makes them not more efficient than conventional compression cooling systems. A main reason for this is the use of non-efficient controls with constant set points that do not allow a chiller power modulation at partial-load and therefore lead to unnecessary high power consumption of the parasitics. The aims of this paper are to present a method to control efficiently solar thermally driven chillers, to demonstrate experimentally its applicability and to quantify the benefits. It has been shown that the cooling capacity of a diffusion absorption chiller can be modulated very effectively by adjusting both the temperature and the flow rate of the cooling water. With the developed approach and the use of optimization algorithms, both the temperature and the flow rate can be controlled simultaneously in a way that the cooling load is matched and the electricity consumption is minimized. Depending on the weather and operating conditions, electricity savings between 20% and 60% can be achieved compared to other tested control approaches. The highest savings are obtained when the chiller is operated at partial load. The presented method is not restricted to solar cooling systems and can also be applied to other conventional heating ventilation and air conditioning (HVAC) systems.

A new photovoltaic–thermal (PVT) system has been developed to produce electricity and cooling energy. Experimental studies of uncovered PVT collectors were carried out in Stuttgart to validate a simulation model, which calculates the night radiative heat exchange with the sky. Larger PVT frameless modules with 2.8 m 2 surface area were then implemented in a residential zero energy building and tested under climatic conditions of Madrid. Measured cooling power levels were between 60 and 65 W m −2 , when the PVT collector was used to cool a warm storage tank and 40–45 W m −2 , when the energy was directly used to cool a ceiling. The ratio of cooling energy to electrical energy required for pumping water through the PVT collector at night was excellent with values between 17 and 30. The simulated summer cooling energy production per square meter of PVT collector in the Madrid/Spain climatic conditions is 51 kWh m −2 a −1 . In addition to the thermal cooling gain, 205 kWh m −2 a −1 of AC electricity is produced under Spanish conditions. A comparative analysis for the hot humid climate of Shanghai gave comparable results with 55 kWh m −2 a −1 total cooling energy production, mainly usable for heat rejection of a compression chiller and a lower electricity production of 142 kWh m −2 a −1 .

Energy supply concepts for zero energy residential building (ZERB) in Shanghai (humid) and Madrid (dry) are discussed in this paper. Simulation is employed as the main research method. Two typical housing models are designed according to the real occupancy condition, the life schedule, the thermostats settings, etc., for the two cities. An energy analysis considering the annual balance of input from the grid and output from renewable power systems is made. Indoor comfortable comparisons between the two models are presented to show optimal design strategies for HVAC under different weather conditions. Also performed is the analysis on the primary energy payback time and the CO 2 equivalent saving in order to evaluate the performance of novel energy systems to verify the feasibility.

On the basis of the Number of Transfer Units (NTU) method a functional relation between electric power for fans/pumps and effectiveness in dry coolers and wet cooling towers is developed. Based on this relation, a graphical presentation method of monitoring and simulation data of heat rejection units is introduced. The functional relation allows evaluating the thermodynamic performance of differently sized heat rejection units and comparing performance among them. The method is used to evaluate monitoring data of dry coolers of different solar cooling field projects. The novelty of this approach is that performance rating is not limited by a design point or standardized operating conditions of the heat exchanger, but is realizable under flexible conditions.