Design,development and testing of a novel non-tracking solar cooker

A novel solar cooker that does not require any tracking, has been designed, fabricated and tested and its performance has been compared with the hot-box solar cooker. The performance of the novel solar cooker is almost similar with the hot-box solar cooker though it is kept fixed while the hot box is tracked towards the sun every hour. The overall efficiency of the novel solar cooker has been found to be 29·5%. The payback period varies between 1·30 and 3·29 years depending upon the fuel it replaces. The payback periods are in the increasing order with respect to fuels such as firewood, coal, electricity, kerosene and LPG. The short payback period shows that the use of the novel non-tracking solar cooker is economical. © 1998 John Wiley & Sons, Ltd.     

Novel solar cookers: suitable for small families

This paper presents the fabrication details and on-field experimental studies of two novel solar cookers, suitable for cooking requirements of small families; these are named as small family solar cookers (SFSC-1 and SFSC-2). Small size, good thermal performance, light weight, low-cost and short payback periods are some important features of these cookers. The values of some essential thermal performance parameters, first figure of merit (F₁), second figure of merit (F₂) and standard cooking power suggested by Bureau of Indian Standards and International Standard for box-type solar cookers, have been evaluated by experimental studies and found to be 0.116°C m²/W, 0.466, 30 W and 0.118°C m²/W, 0.488, 50 W for SFSC-1 and SFSC-2, respectively. A comparative analysis of the thermal performances of SFSCs with the solar cookers, developed by many authors, has also been presented here. The payback periods with respect to different cooking fuels for SFSCs have been found to be reasonably short.     

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.     

Computational study of a novel continuous solar adsorption chiller: performance prediction and adsorbent selection

A novel solar adsorption chiller intended for domestic use is presented. The chiller can be integrated with existing solar systems based on flat plate collectors, and, contrary to commercial chillers, it operates continuously. A detailed analysis of both the simple and the heat‐integrated cycle is carried out so as to select the optimal adsorbent and operating conditions. The employed integral thermodynamic model takes into account the inert masses that limit the performance of the chiller, such as the metal frame, the thermo‐fluid, and the non‐adsorbed steam, by introducing heat capacity effects. Given the adsorption equilibrium data, the energy balances, the performance, and the useful thermal loads of the system can be calculated at any operating conditions. The results indicate that silica gel Type A is a more efficient adsorbent compared to silica gel Type RD or Type 3A. Furthermore, the total porosity has a slight effect on system performance, while optimal operation can be achieved when the condenser temperature is less than 326 K and the evaporator temperature greater than 280 K. Copyright © 2006 John Wiley & Sons, Ltd.     

An evaluation on thermal performance of CPC solar collector

The main objective of this work is the investigation and improvement of thermal performance of evacuated CPC (Compound Parabolic Concentrator) solar collector with a cylindrical absorber. Modified types of this solar collector are always combined with the evacuated glass envelop or tracking system. The conventional stationary CPC solar collector has been compared with the single axis tracking CPC solar collector in outlet temperature, net heat flux onto the absorber and thermal efficiency. Numerical model has been analyzed based on the irradiation determined actually and the results have been calculated to predict the thermal efficiency. Based on the comparison of the measured and calculated results, it is concluded that the numerical model can accurately estimate the performance of solar collectors. The result shows the thermal efficiency of the tracking CPC solar collector is more stable and about 14.9% higher than that of the stationary CPC solar collector.     

Theory and performance analysis of a new heat engine for concentrating solar power

The objectives of this paper are to introduce a new heat engine and evaluate its performance. The new heat engine uses a gas, such as air, nitrogen, or argon, as the working fluid and extracts thermal energy from a heat source as the energy input. The new heat engine may find extensive applications in renewable energy industries, such as concentrating solar power (CSP). Additionally, the heat engine may be employed to recover energy from exhaust streams of internal combustion engines, gas turbine engines, and various industrial processes. It may also work as a thermal‐to‐mechanical conversion system in a nuclear power plant and function as an external combustion engine in which the heat source is the combustion gas from an external combustion chamber. The heat engine is to mimic the performance of an air‐standard Otto cycle. This is achieved by drastically increasing the time duration of heat acquisition from the heat source in conjunction with the timing of the heat acquisition and a large heat transfer surface area. Performance simulations show that the new heat engine can potentially attain a thermal efficiency above 50% and a power output above 100 kW under open‐cycle operation. Additionally, the heat engine could significantly reduce CSP costs and operate in open cycles, effectively removing the difficulties of dry cooling requirement for CSP applications. Copyright © 2014 John Wiley & Sons, Ltd.     

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.     

Design,fabrication and performance evaluation of natural circulation rectangular box-type solar domestic water heating system

This study includes design and experimental analysis of a solar domestic water heating system. Water heating systems with glazed and unglazed collectors were constructed and tested at Dhaka, Bangladesh, at a latitude of 23.7 °N. Collector thermal efficiency and capability of raising water temperature were considered as performance evaluation measures. A typical day analysis showed that collector efficiency varied with time and touched its peak at around 12:00 h. During testing, the efficiency of the glazed collector increased by about 70.3% when compared with the unglazed collector. Average collector efficiency over the whole test period was also estimated to be 57.3% and 33.7% for glazed and unglazed collectors, respectively. Maximum water temperatures measured at daytime user outlets were, respectively, 82.4 °C and 65.5 °C for domestic water heating systems with glazed and unglazed collectors and approximated to be 49 °C and 32 °C higher than the ambient temperature. The glazed collector eventually offered significantly higher performances over the unglazed collector in improving system performance.     

Energy performance enhancement of solar thermal power plants by solar parabolic trough collectors and evacuated tube collectors-based preheating units

Solar steam power plant is the dominant technology in the category of solar thermal power systems. In steam power cycles, there is usually a couple of steam lines, extracted from medium-pressure and low-pressure turbines, to preheat the working fluid before the boiler. This although leads to an increase in the energy efficiency of the cycle, reduces the contribution of the turbine proportionally. Therefore, finding an alternative method of preheating the working fluid would be effective in further enhancement of the efficiency of the system. In this study, the feasibility of using solar collectors for the preheating process in a solar steam power plant is investigated. For this, parabolic trough solar collectors and evacuated tube solar collectors based on a wide range of different scenarios and configurations are employed. The plant is designed, sized and thermodynamically analyzed for a case study in Saudi Arabia where there is a large solar irradiation potential over the year. The results of the simulations show that, among all the considered scenarios, a power cycle aided by a set of parabolic trough collectors as the preheating unit is the best choice technically. This configuration leads to about 23% increased power generation rate and 6.5% efficiency enhancement compared to the conventional design of the plant.     

Improvement of basin type solar still performance : Use of various absorber materials and solar collector integration

Experimental measurements to determine conditions necessary for efficient solar desalination are given. The effects on performance of using various different absorber materials together with the integration of flat-plate collectors with storage systems in basin type solar stills are investigated. Correlations between daily yield (Y, in litres) and solar insolation (I, in MJ/m²day) are found to be, Y = 0.152I − 0.706 (for black-paint absorbers), Y = 0.180I − 0.987 (for charcoal absorbers), Y = 0.225I − 0.467 (for integrated solar collector and storage system, with black-paint absorbers). The calculated daily-average monthly yields for each case are also given.     

配合集热器的盐梯度太阳池热性能实验与分析

构建表面积为1.50 m×1.50 m的小型实验用盐梯度太阳池,并与平板太阳能集热器配合使用,分别对普通太阳池和集热增强型太阳池进行了储热、放热实验。实验研究与理论分析表明:单独盐梯度太阳池的放热量为3.5×103k J,热效率为13.6%;集热增强型太阳池放热量可以达到4.8×103k J,且热效率增至28.1%。另外后者下对流层温度最高可提升10℃以上,从而证明太阳能集热器可以有效提高太阳池热效率,增加下对流层储热量。此外,考虑了放热过程换热器对太阳池下对流层的扰动,对比实验前后的溶液浓度,可以看出实验后太阳池盐度曲线合理,非对流层呈良好梯度分布,太阳池稳定性并未遭到破坏。     

Design performance and economics of a low-cost solar wax melter for the candle industry

Solar thermal energy is a viable energy option for low-temperature applications (< 100 °C), especially in developing countries, where at present fossil fuels (coal and petroleum products) and firewood are inefficiently being used for such applications. The candle-making industry requires solid wax to be melted at about 62 °C. Flat-plate solar thermal collectors can be advantageously used for this purpose. This article describes the conventional method of melting wax and the solar alternative proposed. Experiments conducted using the fabricated solar wax melter of collector area 0·64 m² shows that about 13–15 kg of solid wax could be melted per day. An economic analysis done to compare the cost of the solar wax melter with that of the conventional methods of melting wax indicates the economic viability of the proposed system. It has also been shown how such renewable energy devices could be used for generating gainful employment in rural areas owing to its simple technology, easy use and economics.     

Design, development and testing of a double reflector hot box solar cooker with a transparent insulation material

A double reflector hot box solar cooker with a Transparent Insulation Material (TIM) has been designed, fabricated, tested and the performance compared with a single reflector hot box solar cooker without TIM. A 40 mm thick honeycomb made of polycarbonate capillaries was encapsulated between two glazing sheets of the cooker to minimise convective losses from the window so that even during an extremely cold but sunny day two meals can be prepared, which is not possible in a hot box solar cooker without TIM. The use of one more reflectors resulted in an avoidance of tracking towards sun for 3 h so that cooking operations could be performed unattended, as compared to a hot box solar cooker where tracking ahead of the sun is required every hour. The efficiencies were 30.5% and 24.5% for cookers with and without a TIM respectively, during the winter season at Jodhpur. The energy saving by use of a solar cooker with TIM has been estimated to be 1485.0 MJ of fuel equivalent per year. The payback period varies between 1.66 and 4.23 y depending upon the fuel it replaces, and is in increasing order with respect to the following fuels: electricity, firewood, coal, LPG and kerosene. The estimated life is about 15 y. Therefore, the use of a solar cooker is economical. The double reflector hot box solar cooker with TIM will be a boon in popularising solar cookers in developing countries.     

Data analysis on solar irradiance and performance characteristics of solar modules with a test facility of various tilted angles and directions

We examined and evaluated the output characteristics and the deterioration lowering factors of modules installed under various conditions (module directions and tilted angles) based on the data collected at the multi-position test facility, which was produced and installed in order to conduct evaluation using design parameters (correction coefficient). This report introduces example data and the results of our evaluation.     

Performance evaluation of solar dryer system for optimal operation: mathematical modelling and experimental validation

An analytical moisture diffusion model which considers the influence of external resistance to mass transfer is developed. The methodology to determine constant and variable moisture diffusion coefficients, D_eff is proposed. A laboratory model of mixed-mode solar dryer is constructed to perform 16 experiments for different performance dependent variables under simulated indoor conditions. The potatoes (Solanum tuberosum) of Kufri Safed variety have been chosen as the test food product. The range of variables investigated is absorbed thermal energy (150–750 W/m²); air mass flow rate (0.009–0.022 kg/s); loading density (1.08–4.33 kg/m²) and sample thickness (5–18 mm). The efficiency results have been analysed to identify the value of each process variable leading to optimal operation of dryer. The study reveals that dryer with sample thickness of 8 mm and loading density of 4.33 kg/m² can operate optimally for absorbed energy of 450 W/m² and air mass flow rate of 0.017 kg/s.     

Performance test of a box‐type solar cooker: effect of load on the second figure of merit

In this paper thermal performance test experiments for first figure of merit (without load) and second figure of merit (with load) of a box‐type solar cooker were conducted as per Bureau of Indian Standards. The values of second figure of merit (F₂) were determined for different loads of water and the results show that F₂ depends on the quantity of water loaded in a solar cooker. Therefore, it is recommended that the performance test method should specify the amount of water which is to be taken. Copyright © 1999 John Wiley & Sons, Ltd.     

Research on performance of mixed absorption refrigeration for solar air-conditioning

A novel lithium bromide/water mixed absorption refrigeration cycle that is suitable for the utilization of solar air-conditioning and can overcome the draw-backs of low system overall efficiency of traditional solar absorption refrigeration air-condition systems is presented. The accessorial high pressure generator was added in the cycle. The lithium bromide solution flowing out from the high pressure generator was mixed with the solution from the low pressure absorber to increase lithium bromide solution concentration and decrease pressure in the high pressure absorber. The performance of a mixed absorption refrigeration cycle was analyzed. The theoretical analysis shows that the highest COP is 0.61, while the highest available temperature difference of heat resource is 33.2°C. The whole coefficient of performance of the solar air-conditioning using mixed absorption cycle is 94.5% higher than that of two-stage absorption. The advantages of solar air-conditioning can be markedly made use of by the cycle. __________ Translated from Journal of Huazhong University of Science and Technology, 2006, 34(8): 62–64 [译自: 华中科技大学学报]     

Experimental and simulation studies on the no-load performance assessment of a domestic solar dryer

Solar dryers have been tested with various simple and complex design modifications for better efficiencies. This article attempts to investigate the effect of a very simple design modification on the no-load performance of a natural convection domestic solar dryer (NCDSD). A direct-type domestic solar dryer has been developed with an air cavity surrounding the drying chamber. To compare the effect of air cavity, a domestic solar dryer without air cavity has also been developed and both the dryers were tested simultaneously under the climate of Hisar, India. The values of thermal efficiency were calculated along with convective heat transfer coefficient from absorber plate to the drying air. Both the dryers were also analyzed by developing finite element models in COMSOL multiphysics computer software. The no-load thermal efficiency for the domestic solar dryer without and with air cavity was found to be 22.68% and 34.08%, respectively. The values of coefficient of correlation for modeled and actual drying tray temperatures for dryer without and with air cavity were 0.980466 and 0.9833917, respectively. The proposed finite element model would be helpful in the design and development of NCDSDs.     

Energy for sustainable development: A case of developing countries

Today, there are 1.4 billion people around the world that lack access to electricity, some 85% of them in rural areas. Without additional dedicated policies, by 2030 the number of people drops, but only to 1.2 billion. Some 15% of the world's population still lack access, the majority of them living in Sub-Saharan Africa. The number of people relying on the traditional use of biomass is projected to rise from 2.7 billion today to 2.8 billion in 2030. Addressing these inequities depends upon international recognition that the projected situation is intolerable, a commitment to effect the necessary change, and setting targets and indicators to monitor progress. A new financial, institutional and technological framework is required, as is capacity building in order to dramatically scale up access to modern energy services at the local and regional levels. In this paper, we discussed the energy situation of the developing countries for sustainable development.