Evaluation of solar cooker thermal performance using different insulating materials

This paper summarizes very briefly the thermal performance of solar cookers with four different insulations readily available in rural areas. A comparison of each one of these is made with the performance of glass wool. This experiment is performed to minimize the cost of the cooker with a view to enhance its widespread application in the rural Indian environment.     

A review of solar thermal technologies

The use of solar energy in recent years has reached a remarkable edge. The continuous research for an alternative power source due to the perceived scarcity of fuel fossils is its driving force. It has become even more popular as the cost of fossil fuel continues to rise. The earth receives in just 1 h, more energy from the sun than what we consume in the whole world for 1 year. Its application was proven to be most economical, as most systems in individual uses requires but a few kilowatt of power. This paper reviews the present day solar thermal technologies. Performance analyses of existing designs (study), mathematical simulation (design) and fabrication of innovative designs with suggested improvements (development) have been discussed in this paper.     

On the outlook for solar thermal hydrogen production in South Africa

Global warming and tightening environmental legislation is putting pressure on divesting from fossil fuel in the energy sector, with the transport sector likely to see the biggest changes. Current alternative energy sources are electric vehicles and hydrogen. Conventional hydrogen production technologies are fossil fuel based, emitting significant amounts of CO₂ into the atmosphere. This paper explores various ways to integrate solar thermal technologies into hydrogen production to generate carbon free hydrogen in South Africa. South Africa's abundant solar resource indicates that the country may become a significant player in the hydrogen market. However, the high capital cost associated with solar thermal energy put solar thermal hydrogen at a price disadvantage against conventional production technologies. Significant market penetration for solar thermal hydrogen is not expected within the next decade, but cost reduction due to improved manufacturing techniques and larger manufacturing volumes might close the gap in the long term.     

Design and development of efficient multipurpose domestic solar cookers/dryers

A truncated pyramid-type solar cooker is designed, fabricated and tested. The truncated pyramid geometry concentrates the incident light radiations towards the bottom and the glazing glass surface on the top facilitates the trapping of energy inside the cooker. One of the salient features of the proposed design is to completely eradicate the need for tracking the sun during cooking, as tracking of sun does not yield better performance. During testing, the highest plate stagnation temperature, under no-load condition, approached 140 °C and under full-load condition, water temperature inside the cooker reached 98.6 °C in 70 min. Two figures of merit, F₁ and F₂, were calculated and their values were 0.117° C m²/W and 0.467 °C l, respectively, meeting the standards prescribed by the Bureau of Indian Standards for solar box-type cookers. Minor modifications in design are recommended to achieve higher temperatures and reduce cooking times. The design also allows trays to be retained for use as a household dryer.     

Employment impacts of solar energy in Turkey

Solar energy is considered a key source for the future, not only for Turkey, also for all of the world. Therefore the development and usage of solar energy technologies are increasingly becoming vital for sustainable economic development. The main objective of this study is investigating the employment effects of solar energy industry in Turkey. Some independent reports and studies, which analyze the economic and employment impacts of solar energy industry in the world have been reviewed. A wide range of methods have been used in those studies in order to calculate and to predict the employment effects. Using the capacity targets of the photovoltaic (PV) and concentrated solar power (CSP) plants in the solar Roadmap of Turkey, the prediction of the direct and indirect employment impacts to Turkey's economy is possible. As a result, solar energy in Turkey would be the primary source of energy demand and would have a big employment effects on the economics. That can only be achieved with the support of governmental feed-in tariff policies of solar energy and by increasing research-development funds.     

Modeling and design of a solar thermal system for hybrid cooking application

This paper proposes a hybrid solar cooking system where the solar energy is brought to the kitchen. The energy source is a combination of the solar thermal energy and the Liquefied Petroleum Gas (LPG) that is in common use in kitchens. The solar thermal energy is transferred to the kitchen by means of a circulating fluid. The transfer of solar heat is a twofold process wherein the energy from the collector is transferred first to an intermediate energy storage buffer and the energy is subsequently transferred from the buffer to the cooking load. There are three parameters that are controlled in order to maximize the energy transfer from the collector to the load viz. the fluid flow rate from collector to buffer, fluid flow rate from buffer to load and the diameter of the pipes. This is a complex multi energy domain system comprising energy flow across several domains such as thermal, electrical and hydraulic. The entire system is modeled using the bond graph approach with seamless integration of the power flow in these domains. A method to estimate different parameters of the practical cooking system is also explained. Design and life cycle costing of the system is also discussed. The modeled system is simulated and the results are validated experimentally.     

Life cycle environmental impact of a thermosyphonic domestic solar hot water system in comparison with electrical and gas water heating

A methodology for the environmental impact evaluation over the life span of a Domestic Solar Hot Water System (DSHWS) is presented. The results are compared to the environmental consequences of the conventional energy form substituted and the total environmental gain is calculated. For the purposes of this analysis, the “Eco-indicator ’99” Life Cycle Impact Assessment methodology was adopted and the materials and procedures of the DSHWS production and utilization are evaluated.     

A comprehensive techno-economical review of indirect solar desalination

Solar powered desalination has been the focus of great interest recently worldwide. In the past, majority of the experimental investigations focused on solar coupled thermally driven conventional desalination technologies such as Multi-Stage Flash (MSF) and Multi-Effect Distillation (MED). With the advancement in membrane technology and its advantages such as high Recovery Ratios (RR) and low specific energy requirements Reverse Osmosis (RO) desalination has gained popularity. Currently, 52% of the indirect solar desalination plants are RO based with MED and MSF having a 13% and 9% share respectively. Membrane Distillation (MD) based plants represent 16% of the total and have been a focus of recent research efforts. This paper aims to provide a comprehensive review of all the indirect solar desalination technologies along with plant specific technical details. Efforts assessing the economic feasibility and cost affecting parameters for each desalination technology are also reviewed.     

Models of solar radiation with hours of bright sunshine: A review

In the design and study of solar energy, information on solar radiation and its components at a given location is very essential. Solar radiation data are required by solar engineers, architects, agriculturists and hydrologists for many applications such as solar heating, cooking, drying and interior illumination of buildings. For this purpose, in the past, several empirical correlations have been developed in order to estimate the solar radiation around the world. The main objective of this study is to review the global solar radiation models available in the literature. There are several formulate which relate global radiation to other climatic parameters such as sunshine hours, relative humidity and maximum temperature. The most commonly used parameter for estimating global solar radiation is sunshine duration. Sunshine duration can be easily and reliably measured and data are widely available.     

Thermo-concentration cell: A study on saline water in solar stills

Studies on simultaneous utilization of solar stills as a thermo-concentration cell and as a distillation system have been reported. Cell characteristics have been studied. The electrical energy has been found to increase both with the increase in concentration of sodium chloride (salinity) and the temperature of the saline water. This two way utilization of solar stills has an added advantage that overall utilization efficiency of solar energy is increased against a nominal additional input. For application in rural areas where water needs treatment, (distillation) this extra electrical energy may make it more attractive. The possibility of application of such systems in the industrial sector has also been mentioned.     

Design and development of a solar cooker cum drier

A solar cooker cum drier has been designed and developed. In designing this unit, optimum booster-collector geometry has been considered in order to eliminate the requirement of sun tracking. Tilting arrangements have also been provided to capture more solar energy. This dual purpose device has been found useful for cooking food and dehydrating fruit or vegetables.     

Uses of solar energy in Costa Rica

Costa Rica, a small country with the population of 4 million, and without military and hence no military expenditure, promotes the use of renewable sources like Hydro, Mini hydro, Wind, Geothermal and Sun, mainly for electricity generation. Almost 90% of the electricity is produced from these renewable sources. Through different policies and some incentives, etc., private generation is also encouraged and there are some decentralized systems like solar water heaters, swimming pool heaters, cookers, dryers and stills and also photo voltaic panels. The last ones are mostly for the population where there is no electric grid. Depending on the province, 91–99.5% of the population is electrified. Government also encourages the use of energy saving devices specially at domestic and industrial sector. In addition to provide these data, some of the solar energy systems are mentioned.     

Transparent conductors as solar energy materials: A panoramic review

Transparent conductors (TCs) have a multitude of applications for solar energy utilization and for energy savings, especially in buildings. The largest of these applications, in terms of area, make use of the fact that the TCs have low infrared emittance and hence can be used to improve the thermal properties of modern fenestration. Depending on whether the TCs are reflecting or not in the near infrared pertinent to solar irradiation, the TCs can serve in “solar control” or “low-emittance” windows. Other applications rely on the electrical conductivity of the TCs, which make them useful as current collectors in solar cells and for inserting and extracting electrical charge in electrochromic “smart windows” capable of combining energy efficiency and indoor comfort in buildings. This Review takes a “panoramic” view on TCs and discusses their properties from the perspective of the radiative properties in our ambience. This approach leads naturally to considerations of spectral selectivity, angular selectivity, and temporal variability of TCs, as covered in three subsequent sections. The spectrally selective materials are thin films based on metals (normally gold or titanium nitride) or wide band gap semiconductors with heavy doping (normally based on indium, tin, or zinc). Their applications to energy-efficient windows are covered in detail, experimentally as well as theoretically, and briefer discussions are given applications to solar cells and solar collectors. Photocatalytic properties and super-hydrophilicity are touched upon. Angular selective TCs, for which the angular properties are caused by inclined columnar nanostructures, are then covered. A discussion of TC-like materials with thermochromic and electrochromic properties follows in the final part. Detailed treatments are given for thermochromic materials based on vanadium dioxide and for electrochromic multi-layer structures (incorporating TCs as essential components). The reference list is extensive and aims at giving an easy entrance to the many varied aspects of TCs.     

Induction stoves as an option for clean cooking in rural India

As part of a programme on ‘access to clean cooking alternatives in rural India’, induction stoves were introduced in nearly 4000 rural households in Himachal Pradesh, one of the few highly electrified states in India. Analysis of primary usage information from 1000 rural households revealed that electricity majorly replaced Liquid Petroleum Gas (LPG), generally used as a secondary cooking fuel, but did not influence a similar shift from traditional mud stoves as the primary cooking technology. Likewise, the shift from firewood to electricity as a primary cooking fuel was observed in only 5% of the households studied. Country level analysis indicates that rural households falling in lower monthly per capita expenditure (MPCE) classes have lesser access to electricity and clean cooking options than those falling in higher MPCE classes. Again, only three states in India with high levels of rural household electrification report consumption statuses more than 82 kWh per month (the estimated mean for electricity consumption by induction stoves). Overall, the results of the study indicate that induction stoves will have limited potential in reducing the consumption of firewood and LPG if included in energy access programmes, that too only in regions where high levels of electrification exist.     

A brief review of models for computing solar radiation on inclined surfaces

Modelling of solar energy systems requires estimation of the hourly radiation incident on surfaces of different tilts and orientations. Most meteorological stations report radiation values on a daily rather than hourly basis. Again, the value of the diffuse component may or may not be reported. Hence, different strategies may be encountered, for each location, with the common goal of computing hourly radiation on inclined surfaces.

In this study, five different schemes are presented to achieve this goal. In each scheme, certain correlations are required which are discussed in detail. The study is divided into five sections, each dealing with a specific type of correlation. These sections are: (i) correlations between daily diffuse and global radiation; (ii) correlations between hourly/daily global radiation; (iii) correlations between hourly/daily diffuse radiation; (iv) correlations between hourly diffuse and global radiation; and (v) models for computing diffuse sky radiation on inclined surfaces. The last section deals extensively with the anisotropic nature of sky diffuse radiation.

The important aspects of all correlation studies are highlighted, and the relative merits and demerits of their results are brought to light.

Mathematical expressions, where available, for models/correlations are provided so that the reader will have access to a comprehensive study. This information should be useful for modelling purposes in which computation of radiation on surfaces of different orientations and tilts is required.     

A review for the applications of solar chimneys in buildings

As a simple and practical bioclimatic design methodology, solar chimneys are receiving considerable attention for reducing heat gain and inducing natural cooling or heating in both commercial and residential buildings because of their potential benefits in terms of operational cost, energy requirement and carbon dioxide emission. In practical civil buildings, solar chimneys can be installed on the walls and roofs. For the purpose of improving natural ventilation performance and achieving better indoor thermal comfort, solar chimneys are always applied in the form of integrated configurations. Solar chimneys can also be used to combine with natural cooling systems so as to enhance the cooling effect inside buildings. Besides, active solar systems may be utilized to enhance the ventilation performance of solar chimneys. In this paper, the main configurations and the integrated renewable energy systems based on solar chimneys were summarized. Then the suggestions were given. Generally, solar chimney technology has been regarded as an effective and economical design method in low carbon buildings. As for the integrated energy systems based upon solar chimneys, it is still necessary to carry out more experimental investigations to acquire objective data for the system design. Besides, it is suggested to further study the optimization and control strategy of such integrated systems in different climates.     

Valuation and development of the solar hydrogen production

This article considers Algeria as a case study for the evaluation of the solar hydrogen production potential. The study relates to the design of a hydrogen generating station by water electrolysis whose energy resources are solar. The electricity supply is done by a solar tower power plant. The numerical simulation of the hydrogen production for the installation proposed is made while being based on the characteristic equations governing the electrolysis of water, hydraulic pumping system and the solar tower. The hydrogen production rate is given for various values of the solar radiation and several sites of Algeria. The results obtained by the established computer code, and of which the required goal is the determination of the most favorable conditions for a better production of hydrogen, are presented and discussed.     

Paradoxical impacts of electricity on life in a rural South African village

Debates on the nexus between energy and development emphasise that access to modern energy carriers such as electricity improve development outcomes. This paper discusses the impacts of electrification on educational outcomes, gender and power relations, income generation, feelings of inclusion and exclusion and health in the village of Tsilitwa in the rural Eastern Cape, South Africa. It is based on an ethnographic grounded theory study conducted in 2009. The paper shows that the impacts of electricity may not match the benefits cited in the literature, and are not experienced in the same way by everyone in the community. The study uncovers the weakness of ignoring individual and group agency, and the complexity of social settings when advocating interventions to improve quality of life. The paper recommends that researchers and policymakers consider using ethnographic methods to complement other methods and reveal context and its implications on the energy–development nexus that other methods may not capture.     

Design,development and testing of an improved multipurpose solar energy device

This paper reports the design, development and testing of an improved multipurpose solar energy device. The novel feature of the device is that it can be used as a solar water heater and solar still simultaneously and, when required, as a solar cabinet dryer by incorporating minor changes.     

A new type of solar water heater

This investigation reports a new type of solar water heating system without water pipes on the collector surface or a separate storage tank. The water to be heated continuously flows perpendicularly from an upper transparent cover to a porous absorber and is stored in a small volume beneath this assembly. Three different systems were designed, manufactured and tested but only one proved to be successful; this design indicated higher thermal efficiency compared to conventional collectors at high flow rates whereas at low flow rates the opposite is true.