Solar thermal

Solar thermal water splitting (STWS) produces renewable hydrogen from water using concentrated sunlight. Because it utilizes energy from the entire solar spectrum to directly drive the redox reactions that split water, it can achieve high theoretical solar-to-hydrogen efficiencies. In two-step STWS, a metal oxide is first heated by concentrated sunlight to high temperatures to reduce it and produce O 2 . In the second step, the reduced material is exposed to H 2 O to reoxidize it to its original oxidation state and produce H 2 . Various aspects of this process are reviewed in this work, including the reduction and oxidation chemistries of the active redox materials, the effects of operating conditions, and the solar thermal reactors in which the STWS reactions occur, and a perspective is given on the future optimization of STWS.

The use of solar thermal collectors is one of the promising options for heating and/or cooling due to the green nature (pollution free) and abundance of the solar energy in many parts of the world. Improvement of thermal performance of solar collectors is important for better energy conversion. In this regard, many studies reported in literature tried to modify geometry of the collectors. On the other hand, nanofluids as heat transfer fluids could be a promising option for the efficiency enhancement of solar collectors. In this study, heating performance of an evacuated tube solar collector system initially operated with water is considered for improvement using nanofluid. The collector (about 20 kW heating capacity) is a part of an absorption cooling system. The aim of the present study is to analyze the effect of Single Walled Carbon Nanotube–water nanofluid on the collector performance. Thermal efficiency improvement is assessed based on comparative analyses between collector working with ordinary water and that with nanofluid. The results indicate that up to 56.7% and 66% of efficiencies are observed when the collector is operated with water and 0.2 vol% nanofluid, respectively. Therefore, nanofluids are promising to enhance the efficiencies of solar collectors.

This paper reviews the current status of microgeneration technologies at the domestic scale. Overviews are given for nine such technologies, grouped into three sections: (a) low carbon heating: condensing boilers, biomass boilers and room heaters, air source and ground source heat pumps; (b) renewables: solar photovoltaic panels, flat plate and evacuated tube solar thermal panels and micro-wind; and (c) combined heat and power: Stirling engines, internal combustion engines and fuel cells.

Reviews of the construction, operation and performance are given for the leading commercial products of each technology. Wherever possible, data are presented from the field, giving the actual prices paid by customers, efficiencies and energy yields experienced in real-world use, reliability and durability, and the problems faced by users. This information has a UK focus but is generally relevant in the international context.

Two issues are found to be prevalent throughout the microgeneration industry. Total installed costs are a premium and vary substantially between technologies, between specific products (e.g. different models of solar panel), and between individual installations. Performance in the field is found in many cases to differ widely from manufacturers’ quotes and laboratory studies, often owing to installation and operational problems. Despite this, microgeneration has demonstrated substantial improvements over conventional generation in terms of fossil fuel consumption, carbon dioxide emissions and energy cost, provided that the appropriate technologies are employed, being installed and operated correctly according to the load requirements of the house and their physical location.

In this paper, the energy performance of a photovoltaic/thermal collector equipped with a direct PV air circulation device is studied experimentally and numerically. In this system, the air circulation through the collector duct is ensured by a low input power DC fan that is directly connected to a PV module of small power capacity. In fact, depending on which period of the year the PV/thermal collector is being employed, a 4 Wp or 12 Wp PV panel is used to supply the electrical power to run the DC fan respectively for cold/winter or hot/summer periods. Therefore, the air flow rate under which the present hybrid collector operates is variable and highly affected by the incident solar radiation intensity. A theoretical model for the present hybrid system, in which air flow rate is introduced as a simple empirical correlation relating flow rate to solar radiation, was developed and obtained numerical results have been validated by experimental ones. Simulation and experimental results have been found in reasonably good agreement in terms of PV cell temperature, outlet air temperature, and electric PV peak power. Moreover, the obtained results revealed that low flow rate PV-assisted air circulation systems, if properly sized, would be very attractive for cold periods and winter conditions because of the high air temperature difference they could produce which is a key parameter for space heating applications. On the other hand, the high flow rate system seems to be very suitable for summer conditions where priority is given for the ventilation of PV modules to lower their cells temperature. The suggested PV/T collector design offers the advantage to be self-energy dependent and seems to have a great potential in remote areas.

Ultra-refractory diborides are currently studied mainly as thermal protection materials for aerospace and military applications. However, their favorable properties (very high melting points and good thermo-mechanical properties at high temperatures) can be advantageously exploited to increase the operating temperature of thermodynamic solar plants in concentrating solar power systems. This paper reports on the spectral reflectance characterization of hafnium and zirconium diborides containing MoSi2 as secondary phase to evaluate their potential as novel solar absorbers. To assess the spectral selectivity properties, room-temperature hemispherical reflectance spectra were measured from the UV wavelength region to the mid-infrared, considering different levels of porosity for each system. Moreover, for zirconium diboride and hafnium diboride composites containing 10 vol% of MoSi2 sintering aid, the thermal emittance was measured in the 1100-1400 K temperature range. Room temperature spectral characteristics and high temperature emittance were compared to that of a monolithic silicon carbide.

Prinsloo, G.J., Dobson, R.T., Mammoli, A.A. 2016. Model based design of a novel Stirling solar micro-cogeneration system with performance and fuel transition analysis for rural African village locations. Solar Energy 133, p 315-330 doi:10.1016/j.solener.2016.04.014

This paper describes the performance of a hybrid renewable energy system (HRES) integrated with a combined heat and power cogenerative smart microgrid as remote area power supply (RAPS) in deregulated district energy systems. The research focus on 100% renewables follows on from the ideas of the international energy society (ISES) 100% renewable energy drive, the IEEE smart villages initiative, international renewable energy alliance (IREA), the smart electric power alliance (SEPA) and the alliance for rural electrification (ARE). The proposed hybrid biogas based sun tracker concentrated solar hybrid renewable domestic hot water and power generation system. This alternative energy system design is suitable for space heating, household lighting and cooling refrigeration loads in smart villages, eco-estates, game-farms and remote islands. The study highlights the benefits of embedded generation in integrated and interactive smartgrid configurations for decentralised and district energy systems. International development initiatives such as the Alliance for Rural Electrification and the IEEE Smart Village program have been calling on engineers from developing countries to assist in reducing energy poverty through the design and development of custom designed small-scale sustainable renewable energy solutions. This paper describes the thermodynamic and electrical modeling, simulation and synthesis of a novel kit-based concentrating solar power combined heat and power or hybrid solar cogeneration system. It describes the decentralized solar co-generation system based on a combined cycle Stirling micro-CHP system that includes a low maintenance linear free piston Stirling engine with waste heat recovery, ideal for small business, residential or domestic solar home systems. The concentrating solar combined cycle power and energy system has been designed as a cost-effective community shared solar micro-combined heat and power unit to help enable solar energy utilization within the physical and socio-economic reality of isolated rural areas. This modular plug-and-play unit intends to serve as a stand-alone 100% renewable energy solar powerpack in rural microgrid energy distribution network applications where it will deliver around 3 kW of heat and 1 kW of electricity in distributed generation configurations. The focus of this paper is on the model based design approach in which the main components of the proposed solar micro-combined heat and power system have been systematically modeled on the TRNSYS and Matlab Simulink simulation platforms. This discrete digital modeling approach follows the design guide of the National Renewable Energy Laboratory Village Power Program wherein computer models are used to predict system performance. The TRNSYS model application is extended to meet compulsory World Bank and Development Agency funding and humanitarian investment requirements in terms of providing energy reform and fuel transition projections as part of proving the suitability of newly proposed solar technologies for remote area power applications. The proposed computer model applies statistical weather data to explore the performance, feasibility and fuel transition effects for the solar micro-combined heat and power system in terms of electricity and hot-water generation as well as fuel wood replacement at various locations in Southern Africa. The results show the annual power and hot water generation capability of the system for various sites across Southern Africa, and demonstrates a significant potential in reducing fuel wood usage for villages in these areas. This technology and analysis principles would also be valuable in environmental CO2 sequestration analysis, energy sustainability studies, techno-economic analysis as well as cost benefit studies for greenhouse gas (GHG) mitigation and adaptation technologies. Africa is a developing countries situated in one of the most vulnerable continents to climate variability. Climate change threatens food security and water stress from droughts and floods as well as potential extinction of plant and animal species, calling for nature conservation to reverse wood-land degradation, deforestation and erosion.
This universal distributed generation Stirling engine generation system is ideal for decentralized pre-paid energy co-operatives and pay-as-you-go solar home business models towards empowering remote off-grid villages and indigenous communal living in village communities through indigenous local sustainable energy sources. Energy production from thermodynamic micro-CHP system forms the core of a smart energy system infrastructure that makes up the rural energy system able to serve rural village communities-sustainably. It is intended to ensure sustainable rural development by providing sustainable energy that could displace traditional fossil fuels. The system uses indigenous energy resources, and with added photovoltaic PV or wind energy generation to ensure fossil fuel displacement in replacing fuels such as kerosene, paraffin, candles and wood fuel that cause human health issues and illness due to smoke inhalation. Such hybrid biofuel or biogas solar system provide a sustainable green energy solution and household home heating or district heating solution based on zero-net-energy 100% renewables. It is offered as a humanitarian aid technology to help service coalitions in support of entrepreneurial ventures into engineering for change in remote isolated off-grid rural communities at the bottom of the pyramid.
Follow on work describes the cyber-physical system aspects with smartgrid energy management and control modeling for coordination and optimization of the overall village power system. The integrated community solar and community microgrid solutions are novel in the context of thermo-electrical cogeneration, virtual power plants and hierarchical control structures for remote rural islanded village applications. Hybrid photovoltaic PV, eolica wind, small hydro and biogas cogeneration (poly-generation, tri-generation or hybrid-generation) in multi-carrier pico-grid, nano-grid or micro-grid dispatch can be used for power n energy delivery to drive appliances such as direct current DC LED lighting, fridges, radio, satellite TV, entertainment systems, and sanitation in islanded network configurations. This includes a flexible smart energy management in smart-grid architecture, data analytics and smart-meter instrumentation that includes machine-learning and artificial intelligence with mathematical and economic optimization in demand management, automated demand response, demand management and flexible controllable load curtailment. The intelligent energy management system aspects include customer engagement in control automation, intelligent self-learning, predictive optimization, energy profile or load forecasting, solar forecasting and battery energy storage integration in managing energy reserves. With smart-meter dashboard analytics, this will ensure renewable energy integration in dispersed generation with energy storage (battery, fuel-cell, tank) to ensure practical energy management that deals with the uncertainty, variability, flexibility and energy security in small-scale heat and power microgrids.
Highlights include customer engagement and cooperation in community solar energy utilization in physical & socio-economic reality of isolated rural areas; Localized rural electric power solution to ensure self-sufficient prosumer based energy in community smartgrids; Digital numerical modeling of custom designed kit-based concentrated solar tracker Stirling CSP micro-CHP system; Simulation prediction of CSP system performance in isolated rural African contexts to improve resource coordination and energy preservation; Analysis on fuel transition projections & rural energy generation reform; Need for hot water geyser type energy storage and dispatch; Demonstration of the personalized approach to power supply within sociological relevance and sustainability merit of customized community solar technology.
http://www.sciencedirect.com/science/article/pii/S0038092X16300378
https://www.researchgate.net/publication/301659032_Model_based_design_of_a_novel_Stirling_solar_micro-cogeneration_system_with_performance_and_fuel_transition_analysis_for_rural_African_village_locations

Process simulation has become an accepted tool for the performance, design, and optimization calculations of solar desalination process units. Solving the mathematical models representing these units and systems is a tedious and repetitive problem. Nested iterative procedures are usually needed to solve these models. Also, the process configurations are characterized by existence of a number of recycle streams. To tackle these problems, several researchers have developed different methods, techniques, and computer programs for the simulation of a very wide range of variety of solar desalination process units and systems. It is of interest in this work to show and demonstrate a new program working under Matlab/ SimuLink environments for solar desalination processes calculation and modeling. Using these environments a visual design and simulation for different types and configurations of standalone (common) and solar desalination processes can be performed. Embedded user block programming with SimuLink is implemented to construct a flexible reliable and friendly user-interface package. The solar heating systems and desalination plant components (named here as blocks), such as heat exchangers, flash chambers, evaporators, pumps, steam ejector, compressor, reverse osmosis membrane, pipes, etc., are stored as icons in a visual library. This library enables the user to construct different configurations by just clicking the mouse over the required units (blocks). The interface aids designers, and operators to perform different analyses and calculations such as energy, exergy, and thermoeconomics. Typical desalination processes such as multi stage flash, and reverse osmosis are presented to show the wide scope and the validity, reliability, and capability of the developed package.

Ultra-high temperature ceramics (UHTCs) are the ideal material for extreme conditions thanks to very high melting points, high refractoriness and good thermo-mechanical properties at high temperatures. This paper reports, for the first time to the best of our knowledge, on the microstructural and optical characterization of several tantalum diboride (TaB2) samples with density values from 67% to full density. Pristine samples have been investigated at room temperature by means of SEM, XRD and spectral hemispherical reflectance measurements. Thermal emittance in the temperature range 1050–1800 K has been measured. Structural, compositional and optical properties after high temperature exposure have been characterized as well and property changes have been explained. The obtained results favorably compare TaB2 over conventional solar absorbers for novel solar plants operating at higher temperatures.

The relative influence of the capillary, Marangoni, and hydrophobic forces in medi- ating the evaporation of water from carbon foam based porous media, in response to incident solar radiation, are investigated. It is indicated that inducing hydrophilic interactions on the surface, through nitric acid treatment of the foams, has a similar effect to reduced pore diameter and the ensuing capillary forces. The efficiency of water evaporation may be parameterized through the Capillary number (Ca), with a lower Ca being preferred. The proposed study is of much relevance to efficient solar energy utilization.