Performance evaluation of solar PV/T system: An experimental validation

In this communication, an attempt has been made to develop a thermal model of an integrated photovoltaic and thermal solar (IPVTS) system developed by previous researchers. Based on energy balance of each component of IPVTS system, an analytical expression for the temperature of PV module and the water have been derived. Numerical computations have been carried out for climatic data and design parameters of an experimental IPVTS system. The simulations predict a daily thermal efficiency of around 58%, which is very close to the experimental value (61.3%) obtained by Huang et al.     

The effect of utility time-varying pricing and load control strategies on residential summer peak electricity use: A review

Peak demand for electricity in North America is expected to grow, challenging electrical utilities to supply this demand in a cost-effective, reliable manner. Therefore, there is growing interest in strategies to reduce peak demand by eliminating electricity use, or shifting it to non-peak times. This strategy is commonly called “demand response”. In households, common strategies are time-varying pricing, which charge more for energy use on peak, or direct load control, which allows utilities to curtail certain loads during high demand periods. We reviewed recent North American studies of these strategies. The data suggest that the most effective strategy is a critical peak price (CPP) program with enabling technology to automatically curtail loads on event days. There is little evidence that this causes substantial hardship for occupants, particularly if they have input into which loads are controlled and how, and have an override option. In such cases, a peak load reduction of at least 30% is a reasonable expectation. It might be possible to attain such load reductions without enabling technology by focusing on household types more likely to respond, and providing them with excellent support. A simple time-of-use (TOU) program can only expect to realise on-peak reductions of 5%.     

HEEP: A new tool for the economic evaluation of hydrogen economy

Under agreement and in collaboration with the Indian BHABHA Atomic Research Centre (BARC), the International Atomic Energy Agency (IAEA) has just released the newly developed Hydrogen Economic Evaluation Programme (HEEP) software, which can be used to perform economic analysis related to large scale hydrogen production. The software could be used to analyse economics of the most promising processes for hydrogen production. These processes are: high and low-temperature electrolysis, thermo-chemical processes including Sulphur–Iodine (S-I) process, conventional electrolysis and steam reforming. The IAEA-HEEP software is also suitable for comparative studies not only between nuclear and fossil energy sources for hydrogen production but also for solely hydrogen production or cogeneration with electricity. The HEEP models are based on economic, technical as well as chronological inputs, and cost modelling. Modelling will include various aspects of hydrogen economy including storage, transport, and distribution with options to eliminate or include specific details as required by the users.     

PV-GIS: a web-based solar radiation database for the calculation of PV potential in Europe

Solar radiation is a key factor determining electricity produced by photovoltaic (PV) systems. This paper presents a solar radiation database of Europe developed in the geographical information system, and three interactive web applications providing an access to it. The database includes monthly and yearly average values of the global irradiation on horizontal and inclined surfaces, as well as climatic parameters needed for an assessment of the potential PV electricity generation (Linke atmospheric turbidity, the ratio of diffuse to global irradiation, an optimum inclination angle of modules to maximize energy yield). In the first web application, a user may browse radiation maps and query irradiation incident on a PV module for different inclination angles. The second application simulates daily profiles of irradiance for a chosen month and module inclination and orientation. The third web application estimates electricity generation for a chosen PV configuration. It also calculates optimal inclination and orientation of a PV module for a given location. The database and the applications are accessible at http://re.jrc.cec.ev.int/pvgis/pv/imaps/imaps.htm.     

Experimental results of different control strategies in a solar air-conditioning system at part load

In this article, different control strategies used in a solar cooling installation are presented and compared, publishing real working data from three summer periods, with the system working at part load.The facility consists of two solar fields that feed a heating system during the winter and a 35 kW Li-Br absorption chiller during the summer period to cool part of an office building.The improvements obtained using control based on critical radiation and a variable flow mass have been compared on the solar plant with a conventional constant flow control. In the same way, the improvements obtained in the yields of a cooling production plant have been compared when programming three different controls: the first one with fixed flow masses, the second adapting the temperature on the condenser as a function of the generator temperature (constant flow mass), and the third adapting the condenser temperature and the flow mass on the generator as a function of the system loads.     

Analysis of a solar PV/battery/DG set-based hybrid system for a typical telecom load: a case study

This paper analyses the technical and economic feasibility of using a hybrid renewable energy source for a typical telecom load in the state of Qatar. The hybrid system considered in this work consists of a solar photovoltaic with storage battery and diesel generator set. For this particular hybrid system, the meteorological data of solar irradiance in Doha city (latitude 25.15 ° North and longitude 51.33 ° East) are taken from NASA surface meteorology and solar energy websites. The solar irradiance in Doha is 5.33?kWh/m²/day on an annual average scale. The data are also taken through the study of load consumption of Qatar telecommunication hybrid power system. The system is designed and its techno-economic analysis is carried out using the Hybrid Optimization Model for Electrical Renewable software. The results show both technical and economic viability of replacing the conventional DG sets with the proposed renewable energy source.     

High temperature annealing of sprayed SnO2: F layers in a silicon solar cell process with screen-printed contacts

In order to improve the solar cell conversion efficiency, a thin film of doped tin oxide (SnO₂: F) has been deposited by the spray-pyrolysis technique on a monocrystalline diffused silicon wafer. Subsequently, the layer must undergo the firing step of screen-printed contacts with temperatures up to 830 °C. After annealing, one notices with the naked eye the appearance of speckles disturbing the uniformity of the as-deposited blue-coloured SnO₂:F. Characterizations such as XPS, FTIR, RBS, XRD, SEM, Hall Effect, four point probe...etc, are all consistent to reveal a net increase of the SnO₂:F layer resistivity which leads to efficiency degradation. Annealing the thin films under CO and 90% N₂–10% H₂ atmospheres was investigated to seek possibilities to preserve the expected improvements. Unlike forming gas, CO reducing ambient was found to be very effective for the high temperature contact firing with no thin film conductivity deterioration.     

The economic effect of electricity net-metering with solar PV: Consequences for network cost recovery,cross subsidies and policy objectives

Net-metering is commonly known as a practice by which owners of distributed generation (DG) units may offset their electricity consumption from the grid with local generation. The increasing number of prosumers (consumers that both produce and consume electricity) with solar photovoltaic (PV) generation combined with net-metering results in reduced incomes for many network utilities worldwide. Consequently, this pushes utilities to increase charges per kW h in order to recover costs. For non-PV owners, this could result into inequality issues due to the fact that also non-PV owners have to pay higher chargers for their electricity consumed to make up for netted costs of PV-owners. In order to provide insight in those inequality issues caused by net-metering, this study presents the effects on cross-subsidies, cost recovery and policy objectives evolving from different applied netmetering and tariff designs for a residential consumer. Eventually this paper provides recommendations regarding tariffs and metering that will result in more explicit incentives for PV, instead of the current implicit incentives which are present to PV owners due to net-metering.     

Dynamic modelling of a low-concentration solar power plant: A control strategy to improve flexibility

This paper deals with a dynamic analysis on a low concentration solar power plants coupled with Organic Rankine Cycles (ORC), which can be an alternative to PV systems because of their capability of providing a smoother electricity production due to their thermal inertia. At least within certain restraints, moreover they are able to exploit diffused solar radiation.The dynamic model of a plant with static Compound Parabolic Collectors and an ORC system, using a rotary volumetric expander, was developed using the simulation tool AMESim. All the main components of the plant are modelled: solar collectors field, heat transfer fluid circuit, heat exchangers and the ORC system. The plant response to the radiation of different days was analyzed to quantify the daily production and the trend of various plant parameters. Real ambient conditions were employed for the simulations by using data obtained by historical series.The results showed that the employment of a volumetric expansion device with variable rotating speed allows the plant to operate at different radiations and ambient temperatures without the need of any storage system or external heat sources. Results can be extended to other applications, such as low temperature waste heat recovery or geothermal systems.     

Design of a hybrid polygeneration system with solar collectors and a Solid Oxide Fuel Cell: Dynamic simulation and economic assessment

Solid Oxide Fuel Cells (SOFC) are very promising energy conversion devices, producing electricity and heat from a fuel directly via electrochemical reactions. The electrical efficiency of SOFCs is particularly high, so that such systems are very attractive for integration in complex polygeneration systems. In this paper, the integration of SOFC systems with solar thermal collector is investigated seeking to design a novel polygeneration system producing: electricity, space heating and cooling and domestic hot water, for a university building located in Naples (Italy), assumed as case study. The polygeneration system is based on the following main components: concentrating parabolic through solar collectors, a double-stage LiBr-H₂O absorption chiller and an ambient pressure SOFC fuel cell. The system also includes a number of additional components required for the balance of plant, such as: storage tanks, heat exchangers, pumps, controllers, cooling tower, etc. The SOFC operates at full load, producing electric energy that is in part self-consumed for powering building lights and equipments, and in part is used for operating the system itself; the electric energy in excess is eventually released to the grid and sold to the public Company that operates the grid itself. The system was designed and then simulated by means of a zero-dimensional transient simulation model, developed using the TRNSYS software; the investigation of the dynamic behavior of the building is also included. The results of the case study were analyzed for different time bases, from both energetic and economic points of view. Finally, a thermoeconomic optimization is also presented aiming at determining the optimal set of system design parameters. The economic results show that the system under investigation may be profitable, provided that it is properly funded. However, the overall energetic and economic results are more encouraging than those claimed for other similar polygeneration systems in the recent literature.     

Cost‐competitive methane steam reforming in a membrane reactor for H2 production: Technical and economic evaluation with a window of a H2 selectivity

Techno‐economic viability studies of employing a membrane reactor (MR) equipped with H₂ separation membranes for methane steam reforming (MSR) were carried out for H₂ production in Korea using HYSYS®, a well‐known chemical process simulator, including economic analysis based on itemized cost estimation and sensitivity analysis (SA). With the reaction kinetics for MSR reported by Xu and Froment, the effect of a wide range of H₂ selectivity (10‐10,000) on the performance in an MR was investigated in this study. Because of the equilibrium shift owing to the Le Chatelier's principle, great performance of enhancement of methane conversion ( ) and H₂ yield and reaction temperature reduction was observed in an MR compared with a packed‐bed reactor (PBR). A window of a H₂ selectivity from 100 to 300 is proposed as a new criterion for better MR performance of MSR depending on potential applications from in‐depth analysis of and H₂ yield enhancements, a H₂ purity, and temperature reduction. In addition, economic analysis to evaluate the feasibility of an MR technology for MSR was carried out focusing on a levelized cost of H₂ based on itemized cost estimation of capital and operating costs as well as SA. Techno‐economic assessment showed 36.7% cost reduction in an MR compared with a PBR and revealed that this MR technology can be possibly opted for a cost‐competitive H₂ production process for MSR.