A technoeconomic simulation model for A hybrid solar water heating system

A simple mathematical model has been developed to evaluate the technoeconomic performance of a hybrid solar water heating system for commercial and industrial applications. Numerical calculations, corresponding to Delhi climatic data and for the prevalent cost of a solar energy system in the Indian market, show that the optimum collector area (meeting nearly 45 percent of the daily hot water demand M litres) is 0–0075 Mm²; either a reduction of about 35 per cent in the present solar collector costs or a more than 20 per cent rise in the cost of presently subsidized diesel oil makes the solar option economic. With the present parameters the cost of useful solar energy is higher than that obtained from the conventional system.     

Optimization of tank and flat-plate collector of solar water heating system for single-family households to assure economic efficiency through the TRNSYS program

Solar water heating systems are widely used in Brazil for domestic purposes in single-family households. The exploitation of the potential energy of the water from the upper tank and the thermosyphon phenomena for hot water circulation constitutes the absolute majority of the residential solar water heating systems in the country. But, these water heating systems are usually sized according to tables provided by the manufacturers, which show the number of plates required based on the size of the family and the number of hot water outlets. This sizing is based much more on intuition rather than on scientific data. For that reason, this work has developed an optimization model for water heating systems design parameters, using a numerical simulation routine, in a long-term transient regime. The optimized design gives the slope and area of the flat plate collector, which results in the minimum cost over the equipment life cycle. The computing procedure was executed considering specific characteristics of the project. A thermosyphon solar water heating system with flat-plate collector for Sao Paulo's climate was simulated. The practice of Brazilian designers and manufacturers is to recommend the maximization of the energetic gain for the winter. This paper has analyzed in economic terms if it is more attractive to increase the gain of solar energy in the winter period, with the consequence of reduction of the solar energy gain along the year, or to adopt the adequate slope, which improves the yearly solar energy gain.     

Evaluation of domestic solar water heating system in Jordan using analytic hierarchy process

In addition to the solar water heating (SWH) system, other domestic water heating systems used in Jordan were considered in terms of benefits and costs using the Analytic Hierarchy Process. In terms of cost, the SWH system was the least expensive. On a percentage basis, the SWH cost about 13% compared to the most expensive heating system, LPG, of about 28%. In terms of benefits, the SWH was also the most beneficial. Approximately, the SWH benefits were about 31%, while the least benefits were obtained from the kerosene water heating system, which is about 9%. By considering both cost and benefit (i.e. cost-to-benefit ratio), solar was also the least expensive, about 7%, with kerosene being the most expensive, over 30%.     

Energy flow through the flat-plate solar water heating system

A simulation model of the flat-plate solar water heating system is used to trace the flow of energy through the system from the collector to storage and load for a system operating under idealised sunlight conditions.     

Technoeconomic optimization of a hybrid solar air-heating system

This paper presents a simple techno-economic model for a hybrid solar air-heating system based on water as the storage medium. The configuration of the system consists of a conventional solar air-heater, water tank for thermal storage, a unit which adjusts the higher air temperature (during peak sunshine hours) to the required limit (by mixing fresh air) and an arrangement for providing auxiliary energy if and when required. A thermostatically controlled electric heater is assumed to be the source of auxiliary energy, in the present calculations. In order to evaluate the performance of the system using the developed model numerical calculations have been made corresponding to the climate of Delhi, India. The calculations have been extended to obtain the optimized values of collector area and storage mass which correspond to the minimum value of useful energy. Numerical results show that the cost of useful energy obtained for optimized values of collector area and storage mass is much less than the cost of electrical heating.     

Experimental and theoretical study on a solar assisted CO2 heat pump for space heating

In this paper, a solar combi-system which consists of solar collector and a CO₂ heat pump is investigated experimentally and theoretically. Two experiments are primarily conducted to show the performance of this solar combi-system under different operation conditions. A system model is developed and validated in TRNSYS to analyze the influence of main components parameters. Subsequently, a multi-parameter optimization is carried out in GENOPT to obtain a final optimal result. The simulated results show that the optimized system can save 14.2% electricity and improve the solar fraction by 8%. The solar fraction of the optimized system can reach 71.1%. Finally, the optimized system performance is studied with the weather and load characteristics in Shanghai. Compared with the CO₂ HP heating system alone, the solar assisted system can save 1790.8 kWh electricity on the basis of year round operation.     

Design and performance of large low-cost solar water heating systems

An analysis is presented for the monthly performance evaluation of a simple design low cost solar water heating systems. A sample of typical results is presented which confirms their suitability as solar heating systems for summer peacking or as solar preheaters for year around loads.     

Economic evaluation and optimization of solar systems for space and domestic water heating

Solar energy will be utilized only if it proves to be economical. In this paper, we evaluate the economic feasibility of the use of solar energy for space and domestic water heating systems for a house in Benghazi, Libya. A comprehensive evaluation considerering 324 cases representing the proper ranges of economic and load factors and based on the annual equivalent cost approach is given. The optimum collector area for each case is determined. The results obtained and relationships developed permit generalizations that can be applicable in other locations.     

International policy issues regarding solar water heating, with a focus on New Zealand

Like many countries New Zealand is moving towards renewable energy targets and has recently (November 2006) announced a revised solar hot water heating subsidy program that is being implemented through the Energy Efficiency and Conservation Authority (EECA). This paper describes the new program and reviews international policies regarding solar water heating to see which aspects have been effective in gaining an increased penetration of solar systems for water heating. In addition, the factors leading to successful policy implementation and the possible downsides of the 2006 New Zealand policy are discussed with regard to international experience.     

Optimal design of a forced circulation solar water heating system for a residential unit in cold climate using TRNSYS

An indirect forced circulation solar water heating systems using a flat-plate collector is modeled for domestic hot water requirements of a single-family residential unit in Montreal, Canada. All necessary design parameters are studied and the optimum values are determined using TRNSYS simulation program. The solar fraction of the entire system is used as the optimization parameter. Design parameters of both the system and the collector were optimized that include collector area, fluid type, collector mass flow rate, storage tank volume and height, heat exchanger effectiveness, size and length of connecting pipes, absorber plate material and thickness, number and size of the riser tubes, tube spacing, and the collector’s aspect ratio. The results show that by utilizing solar energy, the designed system could provide 83-97% and 30-62% of the hot water demands in summer and winter, respectively. It is also determined that even a locally made non-selective-coated collector can supply about 54% of the annual water heating energy requirement by solar energy.     

Cyprus solar water heating cluster: A missed opportunity?

Cyprus is often called the “sun island” because of the amount of sunshine received all year round. The abundance of solar radiation together with a good technological base has created favourable conditions for the exploitation of solar energy on the island. This led to the development of a pioneering solar collector industry in Cyprus, which in the mid-1980s was flourishing. The result was an outstanding figure of installed solar collector area per inhabitant. Nowadays, Cyprus is cited as the country with the highest solar collector area installed per inhabitant, worldwide. This means that the local market for solar thermal collectors (for domestic applications) is now rather saturated. It was only rational to assume that Cypriot firms equipped with their gained expertise and leading edge would have safeguarded a sustainable growth and have an international orientation, focusing on exports in an emerging European and eastern Mediterranean thermal solar market. Unfortunately, this is not the case today.     

太阳能热水系统结合地板采暖在高层住宅中的应用

介绍太阳能热水系统结合低温热水地板采暖系统的工作原理,以上海地区为例,在高层住宅中应用壁挂式太阳能集热器,可以实现太阳能与建筑一体化。对该太阳能系统进行节能效益分析,结果表明,系统的动态回收期为3.98年。     

Technoeconomic optimization of solar natural convection hybrid hot water systems

In this paper a techno-economic model for a hybrid domestic hot water system operating under natural convection mode is presented. Three modes of auxiliary energy supply viz.

• A electric heater fitted in the solar hot water tank.
• B electric heater fitted in a small water tank in series with the solar hot water tank, and
• C an instant electric heater fitted in the tap

have been considered. Taking into account the life and the capital and maintenance costs of the solar and electrical equipments, the cost of useful energy (Rs/kWh) has been calculated for different values of the collector area and the tank capacity, and thereby the optimum collector area and tank capacity (for a given demand), corresponding to minimum cost of useful energy, has been determined. From numerical calculations made for the climate of Delhi, India (a representative composite climate) corresponding to the two cases of monthly hot water demand viz. (i) constant monthly demand, and (ii) variable monthly demand, it is seen that case (C) is the most economic design of the hybrid hot water system; numerical calculations have also been made for this case corresponding to the climates of Srinagar and Madras (representing cold and hot climates). The effect of government subsidy on the optimized values of collector area, tank capacity and cost of useful energy has also been investigated for the climate of Delhi.     

Analysis of a solar water heating system with n-tanks in series

A straightforward analysis of a solar water heating system with n-tanks connected in series has been presented. The long-term performance of the system has also been studied. On the basis of numerical calculations made for four successive days, the following conclusions have been drawn:

1. (1) The fluctuation in temperature variation decreases with increase of the number of tanks connected in series.

2. (2) The variation becomes smooth after the second successive day, which is more desirable from the point of view of users.

     

Experimental study of the burning-cave hot water soil heating system in solar greenhouse

In the northern China areas, the traditional heating methods are widely used in solar greenhouse, for example: electric heating, hot air heating, hot water heating, burning-cave heating etc. If copying the assuring building indoor environment of constant heating ways into solar greenhouse, it will further increase building energy consumption, thus improving the efficiency of energy utilization, establishing appropriate growing environment, and realizing the agricultural waste recycling are important ways of consistent with the Chinese conditions, construction of sustainable development, improving the efficiency of the greenhouse production. To solve the problem of traditional heating method for high heating energy consumption, the inharmonious between greenhouse air temperature and soil temperature, uneven soil temperature, the research build the burning cave hot water soil heating system of solar greenhouse experimental platform in accordance with principle of energy cascade utilization. This experiment platform will transfer burning cave internal heat into soil heating system. The soil is evenly heated by system. Through testing the actual operation effect of the burning cave hot water soil heating system of new solar greenhouse, electric heating system, no taking any heating measures system, burning cave hot water soil heating system of solar greenhouse can improve the soil average temperature 5 ∼ 6 °C. This research provides experimental basis for practical applications and promotion.     

On the effects of solar radiation variations on solar heating system performances

The effect of solar radiation availability on the performance of different solar heating systems has been studied. The systems include a solar water heater, passive solar houses and district solar heating systems with seasonal heat storage. Also, different collector orientations and collector types have been investigated. The hourly radiation data were generated by a simple computational simulation procedure. It was found that district solar heating systems with concentrating collectors and passive solar houses showed the largest variations for the given conditions.     

Methodology for estimation of potential for solar water heating in a target area

Proper estimation of potential of any renewable energy technology is essential for planning and promotion of the technology. The methods reported in literature for estimation of potential of solar water heating in a target area are aggregate in nature. A methodology for potential estimation (technical, economic and market potential) of solar water heating in a target area is proposed in this paper. This methodology links the micro-level factors and macro-level market effects affecting the diffusion or adoption of solar water heating systems. Different sectors with end uses of low temperature hot water are considered for potential estimation. Potential is estimated at each end use point by simulation using TRNSYS taking micro-level factors. The methodology is illustrated for a synthetic area in India with an area of 2 sq. km and population of 10,000. The end use sectors considered are residential, hospitals, nursing homes and hotels. The estimated technical potential and market potential are 1700 m² and 350 m² of collector area, respectively. The annual energy savings for the technical potential in the area is estimated as 110 kW h/capita and 0.55 million-kW h/sq. km. area, with an annual average peak saving of 1 MW. The annual savings is 650-kW h per m² of collector area and accounts for approximately 3% of the total electricity consumption of the target area. Some of the salient features of the model are the factors considered for potential estimation; estimation of electrical usage pattern for typical day, amount of electricity savings and savings during the peak load. The framework is general and enables accurate estimation of potential of solar water heating for a city, block. Energy planners and policy makers can use this framework for tracking and promotion of diffusion of solar water heating systems.     

Fuzzy model representation of thermosyphon solar water heating system

The aim of this paper is to focus on improvement in prediction accuracy of model for thermosyphon solar water heating (SWH) system. The work employs grey-box modeling approach based on fuzzy system to predict the outlet water temperature of the said system. The prediction performance results are compared with neural network technique, which has been suggested by various researchers in the last one decade. The outlet water temperature prediction by fuzzy modeling technique is analyzed by using 3 models, one with three inputs (inlet water temperature, ambient temperature, solar irradiance), next with two inputs (inlet water temperature, solar irradiance) and last one with single input (solar irradiance/inlet water temperature). An improved prediction performance is observed with three inputs fuzzy model.     

Transient analysis of parallel plate forced circulation solar water heating system

In this paper, a transient analysis of a forced circulation solar water heating system with and without heat exchangers in the collector loop and storage tank has been presented for a parallel flat plate collector. The effect of various water heating system parameters on its performance have been studied. Numerical calculations have been made for a typical cold day viz. 26 January 1980 in Delhi.     

基于气象数据的家用太阳能热水系统利用优化方法研究

太阳能热水系统每天的太阳能制热水量及用户在不同季节天气中的热水需求量会不同,但家用太阳能热水系统的水箱容量都普遍偏大,在冬季或阴雨天使用辅助能源加热的整箱热水有剩余,造成辅助能源的浪费。提出依据天气状况利用历年气象数据预测太阳能制热水量的方法,从而自动控制水箱水量来提高家用太阳能热水系统热利用效率。在自动控制器中录入各地区历年太阳辐射量数据库和各种太阳能热水系统的太阳能制热水量计算程序,用户可依据当天天气预报的天气状况使用自动控制器就能预测出当天的太阳辐射量可能加热的热水量,再根据自身的热水需求情况选择是否增加辅助能源热水量。此方法在满足用户使用需求的同时提高太阳能有效利用率,也避免浪费不必要的辅助能源。研究以太阳能资源较贫乏地区(Ⅳ区)的南宁市为例进行实验验证,结果可预测出当天太阳辐射制热水量,并能够控制热水出水温度与目标水温的偏差在5℃以内。