Performance and testing of large-size solar water heater cum solar cooker

The performance of a novel device has been tested. The device can be used as a collector cum storage type solar water heater during the winter, and, with minor adjustments, it can be used as a hot-box solar cooker. The device can provide hot water at 50–60°C in the evening, which can be maintained at 40–45°C until the following morning. It can also be used for cooking food for about 40 people. The efficiencies of the device as a solar water heater and as a solar cooker have been found to be 67.7% and 29.8%, respectively. The payback period varies between 1.64 to 5.90 years depending on the fuel it replaces. The payback periods are of increasing length with respect to the fuels firewood, coal, electricity, LPG and kerosene.     

Studies on a new combined concentrating oven type solar cooker

This paper describes a combined concentrating/oven type solar cooker. The device can be used for cooking, boiling and roasting of foods on clear days. The cooker makes use of both concentrator and flat-plate collector principles, wherein the sunlight entering the cooker is reflected onto a hood which is provided with a selective solar absorber coating which houses the cooking vessels. Hence, the cooker makes use of both direct and diffuse solar radiation. The important part of this new device is a stationary mode and maximum capture of energy through improved design. The new cooker has been found to be more practical in comparison with either the simple hot box type solar cooker or concentrator type cookers where one needs to direct it to follow the sun. The cooking trial shows that the new device can be used twice a day, even on winter days.     

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.     

Design, construction and study of a hybrid solar food processor in the climate of Costa Rica

During the last 25 years, the author has designed, constructed, studied and promoted solar oven, hybrid solar/electric oven, solar oven cum drier, solar cooker cum water heater and solar still. In different parts of the world, solar cookers have been made, studied, patented, however, their real uses are very limited due to many reasons—unstable climate, economic, cultural, social and single use, etc. In order to overcome part of the problems mainly the last one, author has recently designed one hybrid food processor (multi-purposes device) and studied various technical and practical aspects. It has been used for cooking, heating/pasteurizing water (to inactivate microbes) and distillation of small quantity of water (to remove different minerals) and drying domestic products (fruits, vegetables and condiments/herbs, etc.). For more than three years of use, author has found this to be a useful device, mainly from convenience, fuel saving, economic and also from ecological point of view. This device can be used at any time and for different uses but with the reduced consumption of conventional fuel.     

A truncated pyramid non-tracking type multipurpose domestic solar cooker/hot water system

For impressive dissemination of the solar thermal gazettes, it is imperative to keep on changing the device design features so as to cater to the different demands of diverse section of the society. Domestic solar hot water systems are not suitable for cooking and the capacity of domestic solar box type cookers for water heating is very low. We report truncated pyramid geometry based multipurpose solar device which could be used for domestic cooking as well as water heating. The device is designed, fabricated and tested. Cooking tests approved by Bureau of Indian Standards were performed in different seasons and the device was found to meet the requirement stipulated on two figures of merit. The performance of the design was also evaluated as a hot water system and the maximum efficiency was found to be 54%. The day-time and average night-time heat-loss coefficients were found to be 5.7 W/°C m² and, 3.74 W/C m², respectively, which are comparable to those of flat-plate collector based solar hot water systems. A simple economic analysis illustrate that this kind of multi-purpose design could be financially viable and physically useful.     

Investigations into the functioning of a supply air window in relation to solar energy as determined by experiment and simulation

‘Supply air windows’ under optimum flow conditions function as an efficient heat reclaim device. Heat escaping from the room, through the inner glass pane, is entrained in the air flow between the inner and outer sashes and returned to the room. A low-E coating to the inner glass acts as a barrier to radiation heat loss across the window so very low U-values can be achieved. These same characteristics enable the window to function as a passive solar component. Its efficiency is inferior to that of a dedicated passive solar device due to its transparency, but even so at modest levels of incident solar gain a worthwhile proportion is entrained into the air flow and supplied to the rooms as pre-heated ventilation air supply. These characteristics have been established by laboratory, test cell investigations, and simulations using computational fluid dynamics and ESP-r, a whole building dynamic thermal modelling tool.     

Technical feasibility assessment of a solar chimney for food drying

Solar dryers use free and renewable energy sources, reduce drying losses (as compared to sun drying) and show lower operational costs than the artificial drying, thus presenting an interesting alternative to conventional dryers. This work proposes to study the feasibility of a solar chimney to dry agricultural products. To assess the technical feasibility of this drying device, a prototype solar chimney, in which the air velocity, temperature and humidity parameters were monitored as a function of the solar incident radiation, was built. Drying tests of food, based on theoretical and experimental studies, assure the technical feasibility of solar chimneys used as solar dryers for agricultural products. The constructed chimney generates a hot airflow with a yearly average rise in temperature (compared to the ambient air temperature) of 13 ± 1 °C. In the prototype, the yearly average mass flow was found to be 1.40 ± 0.08 kg/s, which allowed a drying capacity of approximately 440 kg.     

Solar device for the candle industry

A solar device has been developed for manufacturing candles from paraffin wax, utilizing solar energy. The design, operation and performance of the device have been described. It is concluded that the device can be used for saving fuel, minimizing the loss of wax due to the vaporization and labour.     

Simulation for an optimal application of BIPV through parameter variation

The degree of efficiency of Building Integrated Photovoltaic (BIPV) as a shading device and the variation of the electrical power generation over 1 year in a real building has already been experimentally investigated in my earlier research. In this paper, the influence of the angle of the solar cell panel, albedo of earth, building azimuth, and of solar cell panels under shading on the power generation are theoretically studied to further optimize BIPV implementation. For the validation of the theoretical work, experimental results of the Samsung Institute of Engineering and Construction Company building are used with a wind velocity of the weather data (TRY, test reference year) of Suwon area, Korea. The efficiency of the BIPV system as a shading device was compared at different months. In this work, the simulation program SOLCEL, for the calculation of a shading/sunlit area on solar cell module and facade, surface temperature of solar cell module, effective solar irradiance on solar cell module and the power generation of a BIPV as a shading device, was developed and validated. The SOLCEL can be applied to develop a multi functional Building Integrated Photovoltaic which could improve power generation, thermal comfort, natural lighting, cooling and heating, etc.     

Collector efficiency of upward-type double-pass solar air heaters with fins attached

The collector efficiency of upward-type double-pass flat plate solar air heaters with fins attached and external recycle is investigated theoretically. The double-pass device was constructed by inserting the absorbing plate into the air conduit to divide it into two channels (the upper and lower channels). The double-pass device introduced here was designed for creating a solar collector with heat transfer area double as well as the extended area of fins between the absorbing plate and heated air. Moreover, the advantage of external recycle application to solar air heaters is the enhancement of forced heat convection strength, resulting in considerable device heat transfer performance improvement. This advantage may compensate for the remixing at the inlet which decreases the heat transfer transfer-driving force decrement (temperature difference).     

Experimental investigation of high temperature congregating energy solar stove with sun light funnel

A solar stove which uses a light funnel to guide light and congregate solar energy has been designed. Its structure and operation principle have been introduced. The performance tests under the real weather have been carried out and the graphic lines of experiment have been given. The experimental result shows that the maximum temperature inside the stove is as high as 250 °C under the condition of 1.5 m² of lighting area, 70% reflectivity of reflecting aluminum foil inside surface of concentrator and no load (without water inside the coil pipe). When reflectivity is 86% the heat collecting efficiency of the device is about 43%. The collecting power that the stove receives can be up to 500 W. It is an ideal medium and high temperature solar energy congregating device suitable for industrial usage or cooking and other domestic usage.     

On the relevance of mass transport in thin layer nanocrystalline photoelectrochemical solar cells

A comprehensive analysis of the diffusion and migration processes in the steady state operation of mesoporous photoelectrochemical solar cells has been attempted. The dye sensitized TiO₂ nanocrystalline solar cell utilizing the iodide/triiodide redox mediator serves as the system of reference. The porous nature of the semiconductor plays an important role in this process. Efficient design characteristics for such cells are obtained in order to minimize, e.g., the concentration overpotential, thus minimizing one of the sources of loss in such cells.The models developed illustrate operational aspects such as concentration profiles in the cell under the conditions relevant to existing systems, the limiting or maximum possible currents in the nanocrystalline PEC device, and the anticipated mass-transfer overpotential as a function of current density. The geometric and structural properties of the photoanode as well as the relative position of the counter-electrode with respect to the mesoporous film photoanode can be better exploited towards an efficient operation of the solar energy conversion device.The repercussions of the variation of solar cell design parameters are illustrated experimentally by the performance of practical application devices. These serve as evidence towards the plausibility and the validity of a mass transfer model for the electrolyte function in nanocrystalline PECs.     

Solar cells based on the heterojunction a-C/p-Si

The heterostructure n-CdO/a-C/p-Si is proposed for use as a solar cell device. The heterostructure consists of two semiconductor layers having different optical band gaps. An ultrathin layer of a-C with a narrow optical band gap is located between these layers. The photovoltaic effect in this device has been investigated. It is shown that the short-circuit current I_sc=46 mA/cm² for heterostructure n-CdO/a-C/p-Si corresponds to the values obtained in the best solar cells based on crystalline silicon. It is also shown that the heterostructure n-CdO/p-Si (without a-C) has a short circuit current which is much weaker.     

A new solar concentrating system: Description, characterization and applications

Solar concentrating systems are usually very expensive and require a large space for their installation. This article presents a new solar concentrating device which is low-cost, small-scale, and has very good features for materials treatment. It consists of two sets of mirrors that reflect solar radiation in two steps with a beam array similar to a Fresnel lens. The power density was measured with Gardon-type radiometers. The results are in good agreement with previous work. The system has a nominal power of 2.5 kW, a measured concentration factor of 1040, and a measured focal diameter of 20 mm (90% of power level).     

Utilizing wind and solar energy as power sources for a hybrid building ventilation device

Wind and solar energy are currently used to power many building ventilation devices. Such devices rely exclusively on either solar or wind energy, which limits their usefulness. A low-cost hybrid ventilation device that utilizes both wind and solar energy as power sources was designed to overcome some of the shortcomings of these devices. Wind tunnel testing conducted at the aerodynamics laboratory of the University of New South Wales revealed that the hybrid device had improved operational and performance benefits compared with conventional commercial roof top ventilators, particularly at zero to low wind speeds. This represents a significant step forward and will have an immediate impact in promoting the use of clean energy for the purposes of building ventilation.     

Temperature stratification from thermal diodes in solar hot water storage tank

In this brief note, we have experimentally measured the temperature stratification in a solar hot water storage tank resulting from a simulated solar heating load. Various modifications using a double chimney device that acts as a thermal diode were examined with the intent of maximizing temperature stratification. The greatest stratification was seen with a unique thermal diode arrangement named the express-elevator design, so-called for the direct hot water path from the bottom third of the tank to the top third.     

Solar heat gains and operative temperature in attached sunspaces

Solar heat gains obtainable from attached sunspaces to air-conditioned rooms are evaluated by means of the solution to the optical problem of incident solar radiation absorption through the windows and of the temperature field in the shell separating the sunspace from outdoors and adjacent spaces. The effective absorption coefficient of the sunspace was used for these evaluations as well as the ratio of the absorbed energy of the internal surfaces to the solar energy entering, and the utilization factor of the solar contributions that represent the fraction of the absorbed energy supplied to the indoor air. With reference to a pre-established geometry and to a system of windows made up of clear double-glazing, the solar gains of the sunspace and the adjacent spaces are calculated for some Italian localities at variation of exposure, optical properties and thermal capacity of the opaque surfaces, the amount of ventilation and of the shading device. Finally, the operative temperature was determined for an estimate of comfort acceptability conditions in the sunspace.     

On the comparison of energy sources: Feasibility of radio frequency and ambient light harvesting

With growing interest in multi source energy harvesting including integrated microchips we propose a comparison of radio frequency (RF) and solar energy sources in a typical city. Harvesting devices for RF and solar energy will be competing for space of a compact micro or nano device as well as for orientation with respect to the energy source. This is why it is essential to investigate importance of every source of energy and make a decision whether it will be worthwhile to include such harvesters. We considered theoretically possible irradiance by RF signal in different situations, typical for the modern urban environment and compared it with ambient solar energy sources available through the night, including moonlight.Our estimations show that solar light energy dominates by far margin practically all the time, even during the night, if there is a full moon in the absence of clouds. At the same time, in the closed compartments or at the new moon RF harvesting can be beneficial as a source of “free” energy.     

Influence of the layer thickness and hydrogen dilution on electrical properties of large area amorphous silicon p–i–n solar cell

The aim of this work is to present data concerning the optimization of performances of a large area amorphous silicon p–i–n solar cell (30×40 cm²) deposited by plasma enhanced chemical vapour deposition (PECVD) at 27.12 MHz. In this work the solar cell was split into small areas of 0.126 cm², aiming to study the device performance uniformity, where emphasis was put on the role of the n-layer thickness. The solar cells were studied through the spectral response behaviour in the 400–750 nm range as well as by the behaviour of the AC impedance. Solar cells with fill factor of 0.58, open circuit voltage of 0.83 V, short circuit current density of 17.14 mA/cm² and an efficiency of 8% were obtained at growth rates higher than 0.3 nm/s.