Experimental and computational investigation of a new solar integrated collector storage system

The paper discusses a combined experimental-numerical analysis of an innovative solar thermal device to be used as an Integrated Collector Storage (ICS) system providing domestic hot water. In this equipment the collector acts also as a storage unit, without requiring an external vessel. Due to its simple configuration, the ICS device was successfully used in several circumstances, especially in extreme situations such as in post-earthquake tent cities or to reach remote users in Africa. In order to assess the efficiency of this collector, the draw-off process was investigated measuring the value of the mean temperature of the water discharging from the tap as cold water filled the collector. In the present configuration the draw-off is not completely optimised and a detailed analysis was carried out in order to investigate the mixing of cold and hot water in the solar collector during the discharge phase. A series of thermocouples was placed in selected positions around the shield of the collector to investigate the evolution of the near wall temperature. Furthermore, a numerical analysis based on Large-Eddy Simulation (LES) of the mixing process inside the collector was carried out using an open source, in-house, finite-volume computational code. Even if some restrictive hypotheses were made on the thermal boundary conditions and the absence of stratification, the LES results gave interesting findings to improve the collector performance

Experimental tests of solar collectors prototypes systems

Solar thermal collectors represent one of the most widely used technologies for heat production from renewable energy sources. To increase efficiency and to not increase too much cost different type of solar collectors, and in particular of evacuated tube collectors have been realized. In order to compare performance, tests at different conditions and in different configurations have to be performed. The aim of this paper is to establish the performance of a new prototype via an experimental evaluation of the performance in different conditions and configurations of three collectors. The prototype is particular owing to his new head configuration that permits an innovative parallel configuration way. Therefore, parallel and series configurations have been analyzed applying the UNI-EN 12975, in a steady-state regime. The efficiencies of the two configurations have been tested for different flow rates and different inflow water temperatures. The experimental results show that, with the same input flow rate to the single collector, the parallel configuration has higher performance than the series one, reaching 15% higher level of efficiency. Thus, it seems that these prototypes in optimized configuration can lead to a systems improvement, thereby increasing the overall energy production or giving the same energy production with smaller collector area. © 2015 Published by Elsevier Ltd

Rural electrification in central america and east africa, two case studies of sustainable microgrids

This paper deals with the electrification of rural villages in developing countries using Sustainable Energy Systems. The rural electrification feasibility study is done using Hybrid Optimization Model for Electric Renewable PRO (HOMER PRO). The HOMER PRO energy modelling software is an optimization software improved by U.S. National Renewable Energy Laboratory. It helps in designing, comparing and optimizing the design of power generation technologies. In this paper, two rural electrification case studies are modelled and analysed using HOMER PRO. Technical and economic evaluation criteria are applied to study the feasibility of a micro-hydro plant in El Díptamo (Honduras), and a hybrid plant composed of photovoltaic module arrays, Diesel generators, and flow batteries, in a small island on Victoria Lake. For both cases, we show the results of the studies of the daily and yearly loads, of the resources available in the area and the economic evaluation of the chosen plants configuration

Hydrogen-rich gas production by sorption enhanced steam reforming of woodgas containing TAR over a commercial Ni catalyst and calcined dolomite as CO2 sorbent.

The aim of this work was the evaluation of the catalytic steam reforming of a gaseous fuel obtained by steam biomass gasification to convert topping atmosphere residue (TAR) and CH 4 and to produce pure H 2 by means of a CO 2 sorbent. This experimental work deals with the demonstration of the practical feasibility of such concepts, using a real woodgas obtained from fluidized bed steam gasification of hazelnut shells. This study evaluates the use of a commercial Ni catalyst and calcined dolomite (CaO/MgO). The bed material simultaneously acts as reforming catalyst and CO 2 sorbent. The experimental investigations have been carried out in a fixed bed micro-reactor rig using a slipstream from the gasifier to evaluate gas cleaning and upgrading options. The reforming/sorption tests were carried out at 650 °C while regeneration of the sorbent was carried out at 850 °C in a nitrogen environment. Both combinations of catalyst and sorbent are very effective in TAR and CH 4 removal, with conversions near 100%, while the simultaneous CO 2 sorption effectively enhances the water gas shift reaction producing a gas with a hydrogen volume fraction of over 90%. Multicycle tests of reforming/CO 2 capture and regeneration were performed to verify the stability of the catalysts and sorbents to remove TAR and capture CO 2 during the duty cycle

Energy Production Analysis and Optimization of Mini-Grid in Remote Areas: The Case Study of Habaswein, Kenya

Rural electrification in remote areas of developing countries has several challenges which hinder energy access to the population. For instance, the extension of the national grid to provide electricity in these areas is largely not viable. The Kenyan Government has put a target to achieve universal energy access by the year 2020. To realize this objective, the focus of the program is being shifted to establishing off-grid power stations in rural areas. Among rural areas to be electrified is Habaswein, which is a settlement in Kenya’s northeastern region without connection to the national power grid, and where Kenya Power installed a stand-alone hybrid mini-grid. Based on field observations, power generation data analysis, evaluation of the potential energy resources and simulations, this research intends to evaluate the performance of the Habaswein mini-grid and optimize the existing hybrid generation system to enhance its reliability and reduce the operation costs. The result will be a suggestion of how Kenyan rural areas could be sustainably electrified by using renewable energy based off-grid power stations. It will contribute to bridge the current research gap in this area, and it will be a vital tool to researchers, implementers and the policy makers in energy sector

The Potential in Water Supply and Sanitation Services of the On Site Production of Sodium Hypochlorite (OSEC) Driven by PV Solar Source

This study aims at evaluating the impact of an On Site Electro Chlorination (OSEC) device, a system for the sodium hypochlorite production, on the improvement of health and hygienic standards in Mesoamerica focusing on Chiapas-Mexico and Costa Rica, as well as in Africa, Western Sahara (Refugees Camp) and Tanzania. The threat of infectious diseases and the importance of cleaned and treated water with the consequent high impact on the vulnerable population have been studied in each of the above countries. In this framework the production of low cost sodium hypochlorite through a stand-alone system powered by PV solar source could be a good starting point in improving sanitation conditions, assuring the disinfection of water and clothes, and improve food safety. The cost analysis shows that producing sodium hypochlorite with an OSEC solar system could lead to 10 to 15 times saving with respect to the purchasing of it at market price, above all in developing countries. Furthermore, the LCA study highlights the low environmental impact of the on-site production of sodium hypochlorite through qualitative and quantitative data that demonstrate how this system has pollutant emissions from 14 to 56 times lower than the equivalent industrial process (N factor). The paper describes as well possible practical applications of the sodium hypochlorite in the African and Latin American context. Additionally, it demonstrates the potential to create an impact on the social context and microenterprises specialised in the production of hygiene and sanitation products, managed by local people selling at affordable prices and reaching the poorest villages of developing countries

Real time power management strategy for hybrid energy storage systems coupled with variable energy sources in power smoothing applications

Abstract As the renewable energy sources (RES) production is strongly influenced by multiple geographic factors and highly variable, the need for both energy storage integration and robust real-time power management strategies development is obvious. Wind power represents the largest generating capacity among RES, being at the same time the most fluctuant. The capability to overcome the great disadvantage of wind power variability supports rising its penetration while preserving current operation modes of power systems, so new fashions to achieve this target are of great interest. This paper aims to prove the robustness of a recently introduced power management strategy, able to operate in online conditions, based on simultaneous perturbation stochastic approximation (SPSA) algorithm. To this regard, two different real datasets for wind power profiles with different statistical features are employed. The power management strategy is implemented on a hybrid energy storage system comprising a battery and a flywheel, modeled in Simulink/Matlab. The objectives of the proposed strategy are to reduce the instantaneous power ramp of the profile injected to the grid while smoothening the power profile exchanged by the battery in order to preserve it. Simulations are performed in representative conditions selected on statistical basis. It is demonstrated that the SPSA based power management achieves similar performances in all simulation conditions, proving to be robust. As a performance indicator, the reduction of the power ramp in reference to the 90% CDF threshold is evaluated. It is remarked as an 80% power ramp reduction is obtained towards the grid in both sites. Moreover, the further target is achieved in terms of battery lifetime extension; specifically, the fluctuation of the power profile exchanged by the battery is smoothed by 63% in the first site and 48% in the second, with respect to the flywheel one

Rural Electrification in Central America and East Africa, two case studies of sustainable microgrids

This paper deals with the electrification of rural villages in developing countries using Sustainable Energy Systems. The rural electrification feasibility study is done using Hybrid Optimization Model for Electric Renewable PRO (HOMER PRO). The HOMER PRO energy modelling software is an optimization software improved by U.S. National Renewable Energy Laboratory. It helps in designing, comparing and optimizing the design of power generation technologies. In this paper, two rural electrification case studies are modelled and analysed using HOMER PRO. Technical and economic evaluation criteria are applied to study the feasibility of a micro-hydro plant in El Díptamo (Honduras), and a hybrid plant composed of photovoltaic module arrays, Diesel generators, and flow batteries, in a small island on Victoria Lake. For both cases, we show the results of the studies of the daily and yearly loads, of the resources available in the area and the economic evaluation of the chosen plants configuration