Efficiency Potential of Solar Thermochemical Reactor Concepts with Ecological and Economical Performance Analysis of Solar Fuel Production

Thermo-chemical conversion of biomass for sustainable aviation fuel/fuel additives

The present study is focused on the design and modelling of a novel Combustion Heat Exchanger (CHE), used for heating and hot water supplies in residential buildings. System design includes a combination of an efficient porous burner and heat exchangers. Combined with an Organic Rankine Cycle (ORC) and a Heat Pump (HP), it is meant to deliver higher energy efficiency as well as reduced greenhouse gas emissions. A numerical model has been developed in STAR-CCM+ to evaluate the design. Furthermore, system level heat transfer calculations were acquired to assist with the design process. A step by step approach was undertaken to investigate physical and chemical phenomena in the system. System dimensions, exchanger location and geometry, air/fuel ratio, porous media models, radiation and combustion were investigated along with different exchanger geometries. A novel spiral heat exchanger was introduced in addition to the common coil designs to exhibit both convection and radiation heat transfers. The results indicated that the exhibition of spiral heat exchanger would result in significantly enhanced heat transfer. Overall heat transfer coefficients of 4-5 times higher in comparison to coils could be expected for spiral exchangers. It was shown that radiation heat transfer accounts for a prominent share in the total heat transfer. Furthermore, the CHE could operate at a wide range of lean air/fuel ratios, enabling further decrease in greenhouse gas emissions. As the last part of the study, further investigations on the regular coil exchangers indicated that these exchangers could still be used with the design, but heat transfer enhancement is required to reduce the dimensions. Such enhancements were tested through shell geometry designs with improved results. Overall, the system shows a promising solution for further reduction of CO2 emissions while improving thermal efficiency.

This thesis presents a system approach with the aim to develop improved concepts for small capacity, high temperature lift air-water heat pumps. These are intended to replace fuel fired heating systems in the residential sector, which leads to a major reduction of the local greenhouse gas emissions. Unfavorable temperature conditions set by the existing heat distribution systems and by the use of atmospheric air, as the only accessible heat source, have to be overcome. The proposed concepts are intended to cover the total application range and to provide the full heat demand without any additional (electric) heat supply. A systematic approach, using a multi objective optimization tool, has been applied to evaluate possible alternate refrigerants, which perform best, regarding to the system COP and the specific heat output. All the optimal refrigerant blends are composed by flammable refrigerants and a potential increase of the COP of 8% (compared to the commercial blend R-407C) has been determined. These potential improvements highly depend on the acceptance to use flammable refrigerants, as can be shown by this evaluation. The standard concepts of small capacity heat pumps suffer from a restricted application range and show highly decreasing performances (COP and provided heat) at extreme operating conditions. From the examination of the thermodynamic cycle, different improved concepts are proposed and are assembled in a generalized super-configuration. The most promising concepts have been built as prototype units and have been tested in laboratory. These concepts are: a) the two-stage compression cycles with economizer heat exchanger or b) with economizer flash tank at the intermediate pressure level, c) the booster-compressor setup, d) the one-stage compression cycle including a new developed hermetic compressor, which enables intermediate injection of saturated vapor flow and e) a small capacity auxiliary cycle for liquid subcooling. In all these concepts the application range could be extended, by achieving reduced discharge temperatures and the heat rate provided at extreme operating conditions could be substantially increased (20%-35%, +100% for the booster setup), using the same compressor and evaporator size. System COP has been improved ( 5%) over a large application range, and specifically in high temperature lift operating conditions. The experimental evaluation reveals the major problem of unbalanced oil migration in two-stage compression cycles (except for the booster concept). An extensive evaluation has been applied, to analyze the oil migration in two-stage compression heat pumps. A new developed measurement technique, using a Fourier Transform Infrared Spectrometry combined with a high pressure supporting ATR cell, has been calibrated (with a lower detection limit at 0.2% - 0.4%, and a sensitivity of 0.1%) with the used refrigerant-oil mixtures (R-134a/POE oil and R-407C/POE oil). It has been applied to perform on-line oil concentration measurements during two-stage and one-stage steady stage and during transitory operating modes. A generalized steady state simulation model has been developed including namely the new developed compressor model with an intermediate injection port, considering the geometrical flow path of the tested prototype compressors. A flow map based extensive heat transfer model is integrated into a finned tube evaporator model and taking into account oil effects on the heat transfer. General models of plate heat exchangers and for capillary tube expansion devices complete this modular simulation model, on which the concepts of the super-configuration can be calculated and some parametric analysis has been performed. An in house developed fluid interface module includes the fluid properties calculation program Refprop and allows to define new mixtures or to use the large number of predefined refrigerants.

در تحقیق حاضر، برای تأمین حرارت مورد نیاز گلخانه، یک سامانه ی گرمایش خورشیدی مجهز به متمرکزکننده ی سهموی خطی و جمع کننده ی خورشیدی تخت دو منظوره، پیشنهاد گردید. در این سامانه از یک مخزن برای ذخیره حرارت تولید شده استفاده شد. جریان سیال حامل حرارت در داخل متمرکزکننده به‌صورت اجباری و با استفاده از پمپ انجام گرفت. یک جمع کننده ی خورشیدی در داخل گلخانه نصب گردید که در طول روز، وظیفه گردآوری تابش خورشید و ذخیره حرارت در مخزن و در شب نقش مبدل حرارتی برای انتقال حرارت ذخیره شده در سامانه ی گرمایش، به محیط گلخانه را داشت. ارزیابی سامانه ی پیشنهادی در سه سطح دبی سیال عبوری در متمرکزکننده (0/44، 0/75 و 1/5 لیتر بر دقیقه) و دو حالت با و بدون استفاده از جمع کننده ی تخت خورشیدی انجام گرفت. نتایج تحقیق نشان داد که بیشترین بازده متمرکزکننده در بالاترین دبی سیال عبوری حدود 71 درصد به‌دست آمد. با بالا بردن دبی از 0/44 تا 1/5 لیتر بر دقیقه، به‌طور متوسط ذخیره حرارت در مخزن 32/14 درصد بهبود داشت. با استفاده از جمع کننده ی تخت خورشیدی، به طور متوسط 26/67 درصد و با بالا بردن دبی تا 1/5 لیتر بر دقیقه، 30 درصد در مصرف برق گرم کن کمکی، صرفه جویی گردید. در نهایت، بالاترین مقدار سهم خورشیدی سامانه پیشنهاد شده در تحقیق حاضر، 66 درصد بود که در بیشترین دبی سیال عبوری و با استفاده از جمع‌کننده‌ی تخت خورشیدی مشاهده شد.

Heat of combustion is a thermochemical property that is used for assessing the heating value of solid and liquid fuels as well as the calorific value of food and supplements. It is also used to identify fire hazards of hazardous materials. Heat of combustion has many applications across diverse areas including in jet fuel and propellant formulations, the disposal of combustible waste, the study of foods and supplements for humans and animals, as well as in ecological studies. This study proposes a simple and predictive model for predicting standard heat of combustion. This model was developed using a group contribution approach. The group contribution method represents chemicals according to 220 first-order and 130 second-order groups. The first-order groups are simple groups that describe a wide variety of chemicals, whereas the second-order groups describe polyfunctional compounds and are used to differentiate between isomers. In this study, 680 experimental data points comprising the standard heat of combustion for pure chemicals were collected from open literature. This data set represents various types of groups. The group contributions were regressed using linear regression in MATLAB, yielding an R2 value of 0.9993 with SD, AAE, and ARE values of 71.9892, 53.1008, and 4.6162. The proposed model was found to be predictive and capable of predicting the heat of combustion of various chemicals, which are not only limited to hydrocarbons but also include chemicals that contain groups of alcohol, ester, ether, amine, amide, aromatic, halogen, and sulfur.

Australia is one of the major producers and exporter of agricultural products. Annually, Australian agriculture produces approximately 151 Tg CO2 equivalent emissions. The use of fossil fuels in crop cultivation, harvesting and transportation are considered as the primary source of these greenhouse gas (GHG) emissions. Moreover, agronomic management and crop residues left in the field also contribute to these GHG emissions. Alternative waste management practices include the use of crop residues and agro-wastes as feedstocks for bioenergy production. Anaerobic digestion is considered as sustainable environmental technology to convert industrial sugarcane residues to carbon dioxide (CO2) - neutral biogas. The biogas thus produced can be used to produce heat, electricity and upgrade to biomethane for vehicle use. The produced biomethane can replace the diesel consumption associated with GHG emission in cane transport. Sugarcane is one among the most cultivated crop in the world. Australia alone produced nearly 33.5 million tonnes of cane in 2018 (FAO 2018). These large production of sugarcane lead to an increase in crop residues and agro-wastes from the sugarcane industry. In this study, an investigation regarding the anaerobic co-digestion of crop residues and agro-wastes from sugarcane industry viz, sugarcane trash (SCT) or sugarcane bagasse (SCB) with chicken manure (CM) was investigated in a batch experiment at 37 °C. In spite of various researches conducted till date about co-digestion of lignocellulosic waste with manure, no research data was available regarding the effect of feed ratio on co-digestion of SCT/SCB with CM. This research gap was investigated in this study. In addition to this, steam explosion pre-treatment of SCT/SCB was included to investigate how the pre-treatment influence methane yield among different feed ratios of SCT/SCB with CM. At first, SCT and SCB were subjected to steam explosion pre-treatment (steam impregnation at 130 °C for 5 minutes followed by steam explosion). Later, two sets of biochemical methane potential (BMP) tests were conducted at an Inoculum to Substrate Ratio (ISR) of 2. Co-digestion of untreated and steam exploded SCT or SCB with CM was investigated at feed ratios of 75:25, 50:50 and 25:75 on volatile solids (VS) basis. Assays with 100% untreated and steam exploded SCT or SCB were also included. Chemical analysis revealed that the steam explosion improved the VS content in pre-treated biomass compared with untreated biomass. The increase in VS was 1.6% and 5.7% in SCT and SCB, respectively. On the other hand, a slight reduction in total solids (TS) of nearly 4% and 1% were observed in the case of SCT and SCB, respectively. BMP results showed that the steam explosion had a profound effect on the methane production rates and yields, especially for SCB than SCT. Methane (CH4) yields of 201.8 and 199 ml CH4/gVSadded were obtained during the mono-digestion of untreated SCT and SCB, respectively. The corresponding values for 100% steam-exploded SCT and SCB were 207.5 and 225.6 ml/gVSadded, respectively. In comparison to mono-digestion, the co-digestion of SCB or SCT with CM did not improve the methane yields. Nevertheless, pre-treatment improved the methane production rates and yields of pre-treated biomass than untreated biomass. Among the studied feed ratios, best methane yields of 206.5 ml/gVSadded were obtained when steam-exploded SCT was co-digested with CM at 75:25 ratio. However, methane yields decreased with an increase in the amount of CM added. SCB also showed a similar trend. The best methane yield of 199.5 ml/gVSadded was obtained when steam-exploded SCB was co-digested with CM at 75:25 ratio. Among the tested feed ratios, all co-digestion mixtures except for 75:25 and 50:50 ratios of untreated SCT to CM showed synergistic effects. The best synergistic effect of 18.57% was observed when untreated SCB was co-digested with CM at 25:75 ratio. Kinetic modelling results confirmed that the steam explosion pre-treatment improved the methane production rates and yields by increasing the hydrolysis rate constant values. However, a higher hydrolysis rate constant was noticed for SCT than SCB. The highest hydrolysis rate constant of 0.16 d-1 was achieved at feed ratios of 50:50 and 25:75 of pre-treated SCT:CM. Interestingly, more than 75% of methane in pre-treated assays was produced by Day 11. The study thus suggests that the steam explosion can improve the methane production rates, yields and productivity of SCT and SCB. However, the use of CM as co-substrate did not improve the methane yields when compared to the mono-digestion of SCT or SCB, but a positive synergism was evident in most of the co-digestion feed ratios.

Due to decreasing supplies of fossil fuels and increasing environmental pollution, the introduction of a more fuel efficient electrical power system in aircraft applications is necessary. One possibility to improve the efficiency is to run the auxiliary power unit (APU), which provides electric energy on airplanes, with an efficient proton exchange membrane fuel cell system (PEMFC). The hydrogen for this concept can be provided by partial catalytic dehydrogenation (PCD) of Jet fuel stored onboard. The difference of this alternative thermochemical catalytic process to the more common reforming process is that no water is needed as a reaction partner. Therefore, no CO is generated, which would poison the catalyst in PEMFC. Other than gaseous hydrocarbons, no gaseous side products are expected. Beyond that, a high hydrogen purity of 98 vol.-% can be achieved. The partial conversion of jet fuel of about 10 to 15 % allows further use of the converted fuel in combustion processes on board. Since the composition of kerosene is very diverse, suitable reaction conditions for a process concept of the PCD of kerosene Jet A-1 have to be defined and the efficiency of the process has to be evaluated. In this thesis, two different process concepts for PCD of jet fuel are developed and their efficiency is evaluated by process simulation. One process concept is designed to run with regular kerosene Jet A-1, which involves a desulfurization step of the jet fuel before the PCD to reduce catalyst deactivation by sulfur poisoning. Since the sulfur containing components in Jet A-1 are found in the higher boiling range of kerosene, the desulfurization is accomplished by thermal distillation of desulfurized Jet A-1 fractions by rectification. The second concept is designed to run with desulfurized kerosene which differs in its chemical composition from regular Jet A-1. The first part of this thesis deals with the experimental characterization of the fuels. As the hydrogen yield, conversion of the fuel and product compositions highly depend on the composition of the hydrocarbon groups in kerosene, the detailed chemical composition of kerosene Jet A-1 was investigated and model components have been defined. These model components represent the hydrocarbon groups in the Jet fuel and they can be used for the design of model mixtures to experimentally investigate hydrogen yield, product composition, conversion rates, stability of the catalytic reaction and the reaction conditions. The catalyst used for the experimental investigation is platinum with tin on an aluminum oxide carrier. The experimental results using the model components show, that the hydrocarbon group of cycloalkanes leads to high hydrogen yield and stable reaction conditions. On the other hand, n-alkanes lead to catalyst deactivation by carbon formation on the catalyst surface and side reactions, thus causing a decline of hydrogen purity of the product gas by evolution of gaseous hydrocarbons. In a next step, the previously defined reaction conditions from the model mixture tests are applied to real kerosene. Due to the content of long chain hydrocarbons of up to 22 carbon atoms causing catalyst deactivation by carbon formation, the stability of this reaction is strongly reduced in comparison to the model mixtures. So far, a more suitable catalyst for more stable process conditions does not yet exist. In the second part of the thesis, the experimental results of the model components and model mixture are used for modelling the two process concepts for PCD in the process simulation. To achieve the highest possible system efficiency, a heat and material integration of the two process concepts is accomplished within the process simulation. For the definition of the system efficiency, the hydrogen yield is a key figure since it is the output of the process. The electric efficiency of both process concepts includes system losses of the fuel cell and product gas conditioning. With the experimentally investigated hydrogen yields of the model mixtures, a system efficiency for the process concept, including the desulfurization of the Jet fuel, of 17% is achieved. The process concept working with desulfurized Jet fuel has no additional energy demand for the desulfurization and achieves for system efficiency a value of 20.7%. To compete with a regular gas turbine APU, with average efficiency of 15 to 18%, the fuel cell APU system provided with hydrogen from PCD of kerosene has to be advanced to higher hydrogen yield. This could be accomplished by the development of design fuels for aircraft applications which suit PCD conditions and catalyst development. The results in this work can provide the boundary conditions for these investigations.

The key barrier to wider use of heat pumps is cost effectiveness when compared to other forms of heating. Despite growing environmental concerns heat pump adoption is not growing as quickly as had been expected by many. Falls in the price of fossil fuels mean heat pump costs are likely to have to fall and / or efficiencies will have to rise before more users choose heat pumps. Large ammonia heat pumps can be cost effective and this paper will consider elements of the design of heat pumps that can enhance payback including providing guidance on cost effectiveness of extra heat exchangers and non standard arrangements. Control concepts are considered with regard to maximising the heat output and efficiency. Calculations of the performance across a range of heat outputs and operating conditions for a specific system are used to demonstrate the possible variations of different operating concepts.

There are many reasons why heat transfer and heat exchangers play a key role in the reduction of greenhouse gas (GHG) emissions. Reduction of the final energy consumption and improvement of the power conversion efficiency mean less prime energy consumption, resulting in overall GHG emission reduction. A fuel cell cycle is a promising power conversion method, with high efficiency and producing only water or water steam by using hydrogen. Some renewable energy sources, e.g., biomass and solar energy, have net zero GHG emissions or have no GHG emissions at all. In all these aspects, heat transfer and heat exchangers are very important. In addition to these indirect effects, heat transfer and heat exchangers can also have direct effects on GHG emissions in various situations. In this paper, several examples are reviewed and illustrated, to demonstrate why heat transfer and heat exchangers are important in the development of energy systems generating low emissions of GHG. It is found that the attempt to provide efficient, compact and cheap heat transfer methods and heat exchangers is a real challenge for research. In order to achieve this, both theoretical and experimental investigations must be conducted, and advanced modern techniques must be adopted.

In Italy and many European countries energy production from biomass is encouraged by strong economic subsidies so that renewable energy plants, anaerobic digestion plant producing biogas in particular, are getting large diffusion. Nevertheless, it is necessary to define the environmental compatibility as well as technological and economic issues dealing with the emerging renewable energy scenario. This evaluation should take into account global parameters as well as environmental impacts at regional and local scale coming from new polluting emissions. The environmental balances regarding new energy plants are of primary importance within very polluted areas such as Northern Italy where air quality limits are systematically exceeded, in particular for PM10, NO2 and ozone. The most important environmental shortcomings that should be solved or at least minimized as far as biogas production and utilisation are concerned are: 1. macro-pollutants emissions from biogas engine at the local scale and low fuel utilization index (biogas plants generally don't recover all thermal energy at disposal); 2. indirect GHG emissions, mainly involving post-methanation emissions from the digestate storage; 3. ammonia emissions from the storage and land spreading of digested materials, low fertilising efficiency of manure and digestate, nitrate contamination of groundwater. The described emissions and energy inefficiency could involve negative environmental balances at the local scale, conflicting with the possible benefits arising from biomass energy production. An alternative technological choice for biogas valorisation could be biomethane production (also called green gas) through biogas purification and upgrading processes in order to remove CO2 and trace components. Biomethane production and its injection into natural gas grid (or its use as a transport vehicle fuel) could bring about strong energy and environmental benefits such as higher energy efficiencies and lower specific emissions (district heating CHP units, combined cycle gas turbines, methane powered vehicles). The present study mainly aims at analysing biogas upgrading techniques under the aspects of energy consumptions and environmental sustainability, with a specific focus on minimizing methane losses from the process by means of suitable design and operative choices (temperature, pressures, sorbents, recirculation strategies, etc.) that are fully described and simulated. The considered upgrading techniques are based on the principles of physical and chemical absorption and pressure/vacuum swing adsorption (PSA). The analysis highlights that there are strong differences among the examined upgrading techniques, as far as specific sorbent flows, absorbing tower dimensions, methane losses, power required, recoverable heat and environmental impacts (use of resources, gaseous releases of odorous and polluting molecules, GHG balances) are concerned. In particular, all the analysed upgrading techniques could be designed in order to achieve very low methane slip, below 0.1%, except PSA for which methane losses are hardly reducible below 2%, even at very high energy consumptions. The actual range of methane slip for the considered technologies is 0.1÷5% whereas the energy consumption to upgrade biogas lies in the range 0.05÷0.54 kWhe/m3 of raw biogas. The following analysis reports also some economic evaluations including electric energy costs, thermal energy requirements, biomethane sale incomes and external costs due to environmental impacts of biogas production+upgrading techniques. Within the described cost-benefit approach, the best overall balances seems to be assured by absorption with DEPG and chemical absorption with MEA. Finally, the last part of the present work shows a technical analysis of a specific digestate treatment process that could help reaching both the reduction of GHG and ammonia emissions and, at the same time, the production of fertilizers. The present analysis therefore confirms that biogas/biomethane technology is absolutely ready and suitable to reach very high levels of productivity, efficiency and environmental performances at sustainable costs and the right technological approach could solve many environmental problems regarding nitrate contamination of groundwater, ammonia emissions and global warming issues

It is current interest to make good use of asphalt pavements and airport runways as environmentally friendly solar collectors for the heating and cooling of adjacent buildings as well as to keep the pavements ice-free directly. The process of extracting heat energy from asphalt pavements was investigated in this study. Water flowing through copper tubes inserted within small laboratory prepared asphalt concrete slabs was used as heat exchanger. The rise in water temperature as a result of flow through the asphalt concrete slab was used as the indicator of the efficiency of heat exchange. Thermal conductive fillers were utilized to improve the thermal conductivity of asphalt concrete and thus resulting in an improved efficiency of asphalt collector. Experimental results showed that the heat energy obtained from solar irradiation can be enhanced by means of Conductive Asphalt Concrete (CAC). The circulating water has a cooling effect on decreasing the high temperature within asphalt concrete and thus reducing its risk of permanent deformation. Focus is on mixture design to prepare an effective heat exchanger that is capable to extract a maximum heat from asphalt pavements.

NON-CONVENTIONAL WASTE-DERIVED FUELS FOR MOLTEN CARBONATE FUEL CELLS

EU Agriculture hast to cope with global challenges such as climate change mitigation or making farming more efficient. The active management of agriculture practices using appropriate technologies and practices, as Precision Agriculture, could reduce greenhouse gas (GHG) emissions while increasing agriculture productivity and income. However, information on the uptake and impacts of the use of precision agriculture technologies in EU is so far sparse and site specific. \nThis technical report assesses the impact of Precision agriculture technology (PAT) on GHG emissions and farm economics. To this end, a typology of PAT was created in order to identify those that had the greatest potential to reduce GHG emissions. Secondly, five case studies were selected with the aim of identifying a combination of EU countries, precision agriculture techniques and arable crop types that could realise the maximum potential economic and environmental benefits of adopting PATs. A survey was applied to 971 adopters and non-adopters on the selected study cases with the aim of assessing the reasons behind uptake and the economic and environmental impacts of different. Finally economic and environmental impacts were investigated though a partial budgeting analysis and Miterra-Europe model respectively. \nResults indicate that although most farmers were aware of PAT, uptake rates are low among surveyed farmers. High investment costs, farm size and age were identified has fundamental hampering adoption. The survey reveals that adoption barriers might be overcome by boosting economic incentives aiming at improving economic performance both directly and indirectly. However, nonmonetary incentives such as technical advice or training also seemed to be interesting for surveyed farmers. The results of the survey also showed that information points such as peer-to-peer learning, visit to trade fairs, researchers and industry dealers had a positive effect on enhancing PAT uptake. The results of the partial budget analysis, where capital costs of the technologies are not included, indicate that impacts are highly variable by country, farm type and size and by technology. The results of the environmental impact analysis showed that the introduction of PAT might have positive effects on the environment, with reductions in GHG emissions from the fertiliser application, fertiliser production and fuel use.

Sustainable Energy Transitions in sub-Saharan Africa: Impacts on Air Quality, Economics, and Fuel Consumption

Nowadays, one of the main alternatives for a more rational use of energy in heating applications is the heat pumping technologies. The market is dominated by two kinds of heat pump systems: the electrically driven vapor compression heat pumps (EHP), which are the most widely used in residential heating applications and the thermally driven heat pumps (TDHP), that are usually based on a sorption process. In this thesis, theoretical and experimental investigations of a concept of thermally driven heat pump, based on the coupling of a vapor compression heat pump cycle and an organic Rankine cycle, are presented. The system is named here as ORC-ORC. The studied concept uses a single stage centrifugal compressor directly coupled to a single stage radial inflow turbine. The shaft is rotating on gas bearings, which allows the system to be oil-free. Like most of the other TDHP's, this system has the advantage to work with a variety of fuels or heat sources like wood pellets, natural gas, solar heat, geothermal heat or waste heat. The concept studied in this work is a gas red system for space heating and domestic hot water production in small residential buildings. A systematic approach has been used to evaluate, in term of energy efficiency, the potential of ORC-ORC systems and to propose optimal design specifications at different levels of the design process. The method is based on the optimization which allows to identify the best configurations at each design step with respect to the designer choices. This approach is divided in three steps. In the first step, a model of the complete system has been developed based on a process integration approach. This step allows to quickly determine whether the system is potentially attractive or not, for given conditions, before going deeper in the design process. The results show that, in general, it is advantageous for the ORC evaporation to be supercritical. In the second step, based on the process integration results and heuristic rules, a suitable system heat exchanger network has been generated and modeled. The predicted values of the coefficient of performance (COP) at design conditions, for the different situations, are in the range 1.30 and 2.19. In a last step, the off-design characteristics of the compressor-turbine unit are considered, in order to evaluate the COP as well as the heating capacity range that can be covered with a specific compressor-turbine unit design. For this purpose, a model of the compressor-turbine unit has been developed. Experimental investigations have been carried out with R134a as working fluid. A first simple test rig has been developed to test the selected ORC evaporator in supercritical conditions. The measurements have allowed to calibrate and to validate an in-house supercritical evaporator simulation tool. An ORC-ORC prototype has been developed and built. Commercially available equipment has been used, except for the compressor-turbine unit that has been designed especially for this application. The targeted operating point, with an HP evaporation temperature of 0 °C and a condensing temperature of 35 °C, has not been reached, because of experimental difficulties which caused some delay. A maximum temperature difference of 20 °C between the HP evaporation and the condensation has been achieved, which corresponds to a compressor pressure ratio of 1.9. Measurements have been performed with compressor-turbine unit rotational speeds up to 171 krpm. The theoretical investigations shows that the proposed ORC-ORC concept is an interesting alternative of thermally actuated heating device for small residential buildings. Concerning the experimental investigations, although a number of problems have been encountered during the tests, it has been demonstrated that the proposed concept is feasible with today's technology.