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Abstract Integrating low-carbon technologies (e.g. heat pumps, photovoltaic systems) in buildings influences the stability of the low-voltage grid, which therefore often requires to be reinforced. This article proposes a techno-economic methodology to identify the reinforcements needed to maintain grid stability at the lowest life-cycle cost. Novel contributions include the consideration of three-phase connection of low-carbon technologies as a reinforcement option and the fact that we study to what extent grid reinforcements can mitigate voltage unbalance issues. Additionally, to reduce computing time, a dummy island approach is used, whereby one feeder is modelled in detail and the remainder of the distribution island is represented by an aggregated load. Finally, random repetitions are proposed, to consider uncertainties related to building properties, occupants and the location of low-carbon technologies in the feeders. The methodology is applied to investigate the integration of heat pumps and photovoltaic systems in typical Belgian rural and urban grids. For the rural grid, heat pumps may lead to significant reinforcement costs (up to 1230 €/dwelling), mainly due to voltage stability problems. For the urban grid, heat pump and photovoltaic integration causes low reinforcement cost (

Abstract This paper presents a parametric analysis for a medium to large size (290–500 MW th receiver thermal power) central receiver plant considering the present market trends. The analysis is divided in 4 steps: • Size and location analysis: for a medium to large size central receiver power plant, three turbine power and three different locations that are involved in the development of power tower plants, have been analyzed to assess the impact over the design characteristics of the solar field and receiver sub-systems and over the levelized electricity cost. • Technology analysis: as commercial power tower plants in operation today are mainly using steam and molten nitrate salts, the present analysis compares the two main technologies, without thermal energy storage to evaluate both under similar design conditions. • Storage analysis: thermal energy storage increases the value of electricity produced and the plant capacity factor for both technologies (steam and molten nitrate salts). For this reason, the analysis shows for each optimized solar field and receiver thermal power, the optimum combination of turbine power and thermal energy storage that minimizes the levelized electricity cost, for both technologies. • Component’s cost analysis: market trends are focused on the specific cost reduction by means of larger plant size and through an improved economy of scale. As a result, and based on baseline cost parameters widely accepted in solar industry, an analysis over the specific costs of major components on the electricity cost has been carried out, to lead where the research and development efforts should be made.

Abstract Many organizations in the world are interested in waste management problems and their potential solutions. In order to solve these problems, a Japanese venture company has developed an innovative thermal decomposer for organic wastes called ERCM (Earth-Resource-Ceramic-Machine). The ERCM reactor employs electron injected air to promote the thermal decomposition reaction, while the effect of electron injection into air has not yet been clarified. An experimental work was performed using a fixed bed reactor to explore the effects of different parameters of electron injection into air, the reaction temperature and different feedstock on the syngas generation. The main purpose of this study is to clarify the phenomena occurring in the ERCM reactor where a direct current electric field is produced in the flame reaction zone to enhance the thermal decomposition of wastes. In this regard, a mathematical model for simulating the thermal decomposition of solid waste in the presence of an electric field have been developed. The equations of aero-thermochemistry are coupled to the balance equations for densities of charged species, and the Poisson equation for the electrical potential is solved. The model was validated by the experimental data and showed a good agreement. The results showed that the electric field significantly improves the stabilization of the flame. From the release behavior of CO and CO2, it is noted that the electron injection would affect the char combustion process significantly. Finally the effect of the flame reaction zone generated by the field induced ion wind on the thermal decomposition was investigated.

Abstract With hydrogen becoming more and more important as energy carrier, there is a need for high capacity storage technologies preferably operating at low pressures. Chemical storage in metal hydrides is promising for that purpose, but they require thermal management for hydrogen release and storage, respectively. To overcome this challenge, it is beneficial to store the heat needed for hydrogen release during hydrogen storage in the storage system keeping the additional effort to provide that heat low. In this work, the experimental proof of concept of an adiabatic storage reactor is presented. Magnesium hydride and magnesium hydroxide have been used for hydrogen storage and thermochemical heat storage, respectively. A prototype reactor has been developed and experimentally investigated. It was found that the operating temperature of the materials can be adjusted with the gas pressure in a way to establish a temperature gradient from the MgH2 to the Mg(OH)2 and vice versa. Hydrogen storage and release is enhanced by the thermochemical heating/cooling. A pressure of 9 bar is sufficient to store hydrogen with a capacity of 20.8 gH2 L-1 based on the two materials only, without the steel vessel or insulation. In the heat storage compartment, 300 °C have been reached at 9.75 bar during heat release which is high enough to drive the MgH2 dehydrogenation.

AbstractThe UK government heat strategy is partially based on decarbonisation pathways from the UK MARKAL energy system model. We review how heat provision is represented in UK MARKAL, identifying a number of shortcomings and areas for improvement. We present a completely revised model with improved estimations of future heat demands and a consistent representation of all heat generation technologies. This model represents all heat delivery infrastructure for the first time and uses dynamic growth constraints to improve the modelling of transitions according to innovation theory. Our revised model incorporates a simplified housing stock model, which is used produce highly-refined decarbonisation pathways for residential heat provision. We compare this disaggregated model against an aggregated equivalent, which is similar to the existing approach in UK MARKAL. Disaggregating does not greatly change the total residential fuel consumption in two scenarios, so the benefits of disaggregation will likely be limited if the focus of a study is elsewhere. Yet for studies of residential heat, disaggregation enables us to vary consumer behaviour and government policies on different house types, as well as highlighting different technology trends across the stock, in comparison with previous aggregated versions of the model.

Abstract Efficient operation of thermoelectric devices strongly relies on the thermal integration into the energy conversion system in which they operate. Effective thermal integration reduces the temperature differences between the thermoelectric module and its thermal reservoirs, allowing the system to operate more efficiently. This work proposes and experimentally demonstrates a topology optimization approach as a design tool for efficient integration of thermoelectric modules into systems with specific design constraints. The approach allows thermal layout optimization of thermoelectric systems for different operating conditions and objective functions, such as temperature span, efficiency, and power recovery rate. As a specific application, the integration of a thermoelectric cooler into the electronics section of a downhole oil well intervention tool is investigated, with the objective of minimizing the temperature of the cooled electronics. Several challenges are addressed: ensuring effective heat transfer from the load, minimizing the thermal resistances within the integrated system, maximizing the thermal protection of the cooled zone, and enhancing the conduction of the rejected heat to the oil well. The design method incorporates temperature dependent properties of the thermoelectric device and other materials. The 3D topology optimization model developed in this work was used to design a thermoelectric system, complete with insulation and heat sink, that was produced and tested. Good agreement between experimental results and model forecasts was obtained and the system was able to maintain the load at more than 33 K below the oil well temperature. Results of this study support topology optimization as a powerful design tool for thermal design of thermoelectric systems.

Abstract Radiation energy transfer is modeled as the enthalpy flux of photons across the boundary of a thermodynamic system. It is proved that this energy transfer process can be treated as heat transfer. Compression work must be applied to the system to push the photons out. The energy transfer rate and maximum conversion efficiency computed from the model are identical to those determined from the Stefan–Boltzmann law and the Carnot efficiency for blackbody radiation.

Abstract PV-blind embedded double skin facade (PVB-DSF) is a promising facade system for building energy efficiency. This paper developed a coupled thermal-electrical-optical model for analyzing, evaluating and optimizing the system performance. The ray-tracing method, radiosity method and net radiation method are used for the optical model. The single diode RP-model and Lambert-W function are adopted in the electrical model. The airflow network and energy balance equations are coupled for system thermal model. A complex simulation algorithm is proposed for the thermal-electrical-optical model solution. A series of experiments were implemented for model verification. The comparisons between simulation and measurement data show a good agreement. Specifically, the relative mean square error (RMSE) for simulation result in optical model is 2.02 W/m2 in sunny day and 5.21 W/m2 in cloudy day; 2.24 V for output voltage and 1.47 W for output power; 0.67 °C, 0.41 °C and 2.17 °C for external, internal glass pane and PV-blind. On top of that, the model is used as a tool for understanding the system performance under different configurations and position of PV-blind, solar cell efficiency and airflow rate. PV-blind angle and width under different spacing settings are optimized for balancing system energy performance and indoor daylighting comfort level. This study offers a useful simulation tool and a deeper understanding of PVB-DSF, which is beneficial for the design, control, optimization and evaluation of this effective glazing facade and can contribute to building energy efficiency.