Analysis of the opportunities and challenges of solar water heating system (SWHS) in India: Estimates from the energy audit surveys & review

A solar water heating system (SWHS) is a device that makes available the thermal energy of the incident solar radiation for use in various water heating applications. SWHS largely depends on the performance of the collector's efficiency at capturing the incident solar radiation and transferring it to the water. With today's SWHS, water can be heated up to temperatures of 60–80 °C. Heated water is collected in a tank insulated to prevent heat loss. Circulation of water from the tank through the collectors and back to the tank continues automatically due to the thermosiphon principle. The hot water generated finds many end-use applications in domestic, commercial, and industrial sectors. India has the highest energy intensities in Asia. Very little investment and priority are being given to increase of the efficiency. On the other hand, the India has a high potential for developing energy production from renewable energy sources (RES): solar, water, wind and biomass. However, these potentials are not studied and exploited enough and the present situation for their utilization is not so good. Although energy is a critical foundation for economic growth and social progress of any country, there are many constraints for RES development in all of them (political, technological, financial, legislative, educational, etc.). Obviously, defining development strategies and new support measures is necessary since renewable energy sources can make an important contribution to the regional energy supply and security. The main purpose of this paper is to explore the solar water heating system (opportunities) in India.     

Sustainability estimation of energy system options that use gas and renewable resources for domestic hot water production

Two possible substitutions for fossil fuel used in heat production are biomass and solar energy. This paper presents an evaluation of various energy sources for hot water production in a heating plant. The heating plant was situated in one of the largest municipalities in the city of Belgrade, Serbia. It produces and delivers domestic hot water and energy for heating to approximately 17,000 households. It is possible to use of using renewable energy instead of fossil fuel for producing the thermal energy for the supply of domestic hot water. Hence, in this paper, an evaluation of the sustainability of different energy options for obtaining thermal energy was considered: 1) from gas combustion; 2) from gas combustion and solar collection 3) from biomass combustion 4) from gas and biomass combustion, and 5) from gas and biomass combustion and solar collection. To compare the different energy systems, the method of multi-criteria analysis was utilised. This method integrates various multi-dimensional criteria and provides an efficient method of estimating the sustainability of complex systems. The obtained results were compared by the General Index of Sustainability which is a measure of the complexity of a system. A basic set of energy indicators that relate to different aspects of sustainable development was defined. In this way, the results in the assessment of sustainability of energy options do not depend on the various analysts in decision making.     

An evaluation of domestic solar energy potential in Taiwan incorporating land use analysis

Solar energy is widely regarded as a major renewable energy source, which in future energy systems will be able to contribute to the security of energy supply and the reduction of CO₂ emissions. This study combined an evaluation of solar energy resources in Taiwan with land use analysis, which allows the potentials and restrictions of solar energy exploitation resulting from local land use conditions to be considered. The findings unveiled in this study indicate that photovoltaic electricity generation and solar water heating have the potential of producing 36.1 and 10.2 TWh of electricity and thermal energy annually in Taiwan, accounting for 16.3% and 127.5% of the total domestic consumption of electricity and energy for household water heating in 2009, respectively. However, the exploited solar photovoltaic power generation in 2009 accounted for only 0.02% of total potential in Taiwan, while the exploited solar water heating accounted for 11.6% of total potential. Market price and investment incentive are the dominant factors that affect market acceptance of solar energy installation in Taiwan. The administrative barriers to the purchase and transmission of electricity generated from renewable energy sources have to be removed before the potential contribution of solar energy can be realized.     

Renewable and sustainable approaches for desalination

Freshwater and energy are essential commodities for well being of mankind. Due to increasing population growth on the one hand, and rapid industrialization on the other, today's world is facing unprecedented challenge of meeting the current needs for these two commodities as well as ensuring the needs of future generations. One approach to this global crisis of water and energy supply is to utilize renewable energy sources to produce freshwater from impaired water sources by desalination. Sustainable practices and innovative desalination technologies for water reuse and energy recovery (staging, waste heat utilization, hybridization) have the potential to reduce the stress on the existing water and energy sources with a minimal impact to the environment. This paper discusses existing and emerging desalination technologies and possible combinations of renewable energy sources to drive them and associated desalination costs. It is suggested that a holistic approach of coupling renewable energy sources with technologies for recovery, reuse, and recycle of both energy and water can be a sustainable and environment friendly approach to meet the world's energy and water needs. High capital costs for renewable energy sources for small-scale applications suggest that a hybrid energy source comprising both grid-powered energy and renewable energy will reduce the desalination costs considering present economics of energy.     

Monitoring and operational results of a hybrid solar-biomass heating system

Solar thermal systems, that provide auxiliary energy for space heating, represent a growing opportunity in European countries like Austria and Germany. However, such systems are as yet not widely known in the rest of Europe, unlike thermosyphon water heating systems. In addition, the need for energy conservation and reduction of CO₂ emissions, to combat climate change, demands the use and advance of renewable energy sources in new sectors than for common domestic water heating.The purpose of this research work is to present a full cycle of operational results of a hybrid solar thermal-biomass space heating system in Greece.The hybrid heating system was installed at the Centre for Renewable Energy Sources (CRES), Pikermi, central Greece in September 2005 with the intension to provide all the heat requirements for a specific office block of 60 m² area. The system was analyzed and optimized over a period of 6 months. The solar contribution during the actual measurement period (60% of the operating period) covered 52.9% of the total heating demand.The operational results of this unit from November 2005 till April of 2006 are presented and analyzed. The main parameters presented here include the operation of the system, the results, the coverage fraction (f%) of the solar and the biomass subsystems, the actions taken to increase its efficiency and the technical problems faced along with possible solutions to overcome them.     

Combined micro-cogeneration and electric vehicle system for household application: An energy and economic analysis in a Northern European climate

In recent years, Denmark boosted investments in renewable energy and electrification of transportation. The Danish Agenda proposed that all primary energy consumption will be covered by renewable sources such as wind, biomass and solar by 2050. These changes require significant investment and re-thinking of entire energy infrastructures and types of consumption. The Agenda also suggested, among other things, improving the efficiency of energy systems.In this paper, the interactions between charging an electric car and an innovative cogeneration system for household application (micro-solid oxide fuel cell with an integrated heating system) are investigated. The charge of the electric car by the cogenerator produces waste heat that can be used to partially cover the heat demand of the house. In this way it may be possible to increase overall efficiency and decrease total energy costs. Different innovative strategies are proposed and analyzed to manage charging an electric car and efficiently using the waste heat available. The aims of this study are to make the system grid-independent, to decrease the thermal stress of SOFCs and to determine the nominal power of an integrated heating system. The results show energy efficiency and economic profitability of the system, even if subsidies are not included.     

Exergy analysis of solar energy applications

Solar energy is a clean, abundant and easily available renewable energy. Usage of solar energy in different kinds of systems provides scope for several studies on exergy analysis. In the present work, a comprehensive literature review has been carried out on exergy analysis of various solar energy systems. The systems considered under study are solar photovoltaic, solar heating devices, solar water desalination system, solar air conditioning and refrigerators, solar drying process and solar power generation. The summary of exergy analysis and exergetic efficiencies is presented along with the exergy destruction sources.     

Palestine: RE action plan : Moving away from traditional energy resources

Renewable energy resources show great promise in Palestine. Solar, wind, biogas and geothermal energy resources are the main areas where research and pilot projects are being concentrated (2000–2005). More than 95% of Palestinians use solar energy for domestic water heating so renewable energy is something that many people in the country are already very aware. Consequently, use of renewable energy resources presents a strategic goal for the Palestinian energy authority in order to achieve some degree of economic independence. It aims to minimize the dependence on traditional energy resources that are too expensive and politically controlled. Awny Naim and Mohammad R Al-Agha, Palestinian Renewable Energy Society describe the current situation in the region.     

Review of the phase change material (PCM) usage for solar domestic water heating systems (SDWHS)

The shortage in energy resources combined with the climb in greenhouse emissions is the main incentive beyond the deployment of solar energy resource in various applications. One of the most successful applications is the utilization of solar energy in the domestic water heating systems (DWHS) because 70% of the consumed energy in the residential segment is utilized for space heating and appliances in cold climates 1 . However, the full deployment of solar energy in domestic water heating is only possible when an energy storage system with acceptable price is available. Recently a new tendency for deploying phase change materials (PCMs) as an energy storage system is introduced in several solar DWHS. These systems are known as integrated PCM in solar DWHS and offer several advantages including high storage capacity, low storage volume, and isothermal operation during the charging and discharging phases. The present study reviews various techniques utilized for integrating the PCM in solar water heating systems and the utilized methods for enhancing the heat transfer characteristics of the PCM through the usage of extended surfaces and high conductive additives. Copyright © 2017 John Wiley & Sons, Ltd.     

Comparative analysis of support mechanisms for renewable energy technologies using probability distributions

In this paper, a probabilistic model is developed to assess the effects of different support mechanisms on the financial return of small-scale hydroelectric, wind energy and solar PV systems. Besides, the results from this model are used to compare the economic effectiveness of each mechanism in increasing the profitability of these projects. We focus on three renewable energy support mechanisms: governmental grants, feed in tariffs (FiT) and renewable energy certificates (RECs). We also consider the effect of the carbon credits on the net present value of renewable projects and compare it with the other support mechanisms. The simulation results demonstrate that the feed in tariffs is the best mechanism to increase the profitability of solar PV systems and wind energy projects. Conversely, green certificate mechanism favors the most competitive technology as the hydropower. In addition, it is shown that the governmental grants and carbon credits are secondary support mechanisms compared to FiT and RECs. And, the carbon credits play a more important role than governmental grants as the energy output of the system increase. Finally, it can be concluded that the efficiency of the support mechanisms varies depending on stage of development of the renewable technologies that are implemented.     

Thermal performance, economic and environmental life cycle analysis of thermosiphon solar water heaters

In this paper, the environmental benefits or renewable energy systems are initially presented followed by a study of the thermal performance, economics and environmental protection offered by thermosiphon solar water heating systems. The system investigated is of the domestic size, suitable to satisfy most of the hot water needs of a family of four persons. The results presented in this paper show that considerable percentage of the hot water needs of the family are covered with solar energy. This is expressed as the solar contribution and its annual value is 79%. Additionally, the system investigated give positive and very promising financial characteristics with payback time of 2.7 years and life cycle savings of 2240 € with electricity backup and payback time of 4.5 years and life cycle savings of 1056 € with diesel backup. From the results it can also be shown that by using solar energy considerable amounts of greenhouse polluting gasses are avoided. The saving, compared to a conventional system, is about 70% for electricity or diesel backup. With respect to life cycle assessment of the systems, the energy spent for the manufacture and installation of the solar systems is recouped in about 13 months, whereas the payback time with respect to emissions produced from the embodied energy required for the manufacture and installation of the systems varies from a few months to 3.2 years according to the fuel and the particular pollutant considered. It can therefore be concluded that thermosiphon solar water hearting systems offer significant protection to the environment and should be employed whenever possible in order to achieve a sustainable future.     

Optimum design of hybrid renewable energy systems: Overview of different approaches

Public awareness of the need to reduce global warming and the significant increase in the prices of conventional energy sources have encouraged many countries to provide new energy policies that promote the renewable energy applications. Such renewable energy sources like wind, solar, hydro based energies, etc. are environment friendly and have potential to be more widely used. Combining these renewable energy sources with back-up units to form a hybrid system can provide a more economic, environment friendly and reliable supply of electricity in all load demand conditions compared to single-use of such systems. One of the most important issues in this type of hybrid system is to optimally size the hybrid system components as sufficient enough to meet all load requirements with possible minimum investment and operating costs. There are many studies about the optimization and sizing of hybrid renewable energy systems since the recent popular utilization of renewable energy sources. In this concept, this paper provides a detailed analysis of such optimum sizing approaches in the literature that can make significant contributions to wider renewable energy penetration by enhancing the system applicability in terms of economy.     

Perspectives for solar thermal applications in Taiwan

Taiwan has long depended on imported fossil energy. The government is thus actively promoting the use of renewable energy. Since 2000, domestic installations of solar water heaters have increased substantially because of the long-term subsidies provided for such systems. However, data on the annual installation area of solar collectors in recent years indicated that the solar thermal industry in Taiwan has reached a bottleneck. The long-term policy providing subsidies must thus be revised. It is proposed that future thermal applications in Taiwan should focus on building-integrated solar thermal, photovoltaic/thermal, and industrial heating processes. Regarding building-integrated solar thermal systems, the current subsidy model can be continued (according to area of solar collectors); nevertheless, the application of photovoltaic/thermal and industrial heating systems must be determined according to the thermal output of such systems.     

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.     

Design optimization of a polygeneration plant fuelled by natural gas and renewable energy sources

A new and systematic procedure to select and size a polygeneration plant fuelled by natural gas, solar energy and gasified biomass is presented in this paper. The proposed procedure is based on the superstructure definition, containing a long list of possible configurations for a polygeneration plant simultaneously producing electricity, heat, cold and fresh water. Based on that superstructure, a mathematical programming model was developed and applied to a Spanish tourist resort. Three key aspects were optimized in the mathematical programming problem: energy savings, greenhouse gases (GHG) emission reduction and economic feasibility. The results show, firstly, that the simultaneous production of electricity, heat, cold and fresh water is reliable upon the established assumptions. Secondly, that today higher economic profitability is yet achieved with only natural gas-based technologies, although higher energy savings and GHG reduction are obtained through the gradual increase of renewable energy sources.     

Seawater desalination using renewable energy sources

The origin and continuation of mankind is based on water. Water is one of the most abundant resources on earth, covering three-fourths of the planet's surface. However, about 97% of the earth's water is salt water in the oceans, and a tiny 3% is fresh water. This small percentage of the earth's water—which supplies most of human and animal needs—exists in ground water, lakes and rivers. The only nearly inexhaustible sources of water are the oceans, which, however, are of high salinity. It would be feasible to address the water-shortage problem with seawater desalination; however, the separation of salts from seawater requires large amounts of energy which, when produced from fossil fuels, can cause harm to the environment. Therefore, there is a need to employ environmentally-friendly energy sources in order to desalinate seawater.After a historical introduction into desalination, this paper covers a large variety of systems used to convert seawater into fresh water suitable for human use. It also covers a variety of systems, which can be used to harness renewable energy sources; these include solar collectors, photovoltaics, solar ponds and geothermal energy. Both direct and indirect collection systems are included. The representative example of direct collection systems is the solar still. Indirect collection systems employ two sub-systems; one for the collection of renewable energy and one for desalination. For this purpose, standard renewable energy and desalination systems are most often employed. Only industrially-tested desalination systems are included in this paper and they comprise the phase change processes, which include the multistage flash, multiple effect boiling and vapour compression and membrane processes, which include reverse osmosis and electrodialysis. The paper also includes a review of various systems that use renewable energy sources for desalination. Finally, some general guidelines are given for selection of desalination and renewable energy systems and the parameters that need to be considered.     

Life cycle assessment of a solar thermal collector

The renewable energy sources are often presented as ‘clean’ sources, not considering the environmental impacts related to their manufacture. The production of the renewable plants, like every production process, entails a consumption of energy and raw materials as well as the release of pollutants. Furthermore, the impacts related to some life cycle phases (as maintenance or installation) are sometimes neglected or not adequately investigated.The energy and the environmental performances of one of the most common renewable technologies have been studied: the solar thermal collector for sanitary warm water demand. A life cycle assessment (LCA) has been performed following the international standards of series ISO 14040. The aim is to trace the product's eco-profile that synthesises the main energy and environmental impacts related to the whole product's life cycle. The following phases have been investigated: production and deliver of energy and raw materials, production process, installation, maintenance, disposal and transports occurring during each step. The analysis is carried out on the basis of data directly collected in an Italian factory.     

Renewable energy resources as an alternative to modify the load curve in Northern Cyprus

The average annual increase in electricity consumption and peak demand in Northern Cyprus (N. Cyprus) during the past 20 years have been 7.1 and 5.5%, respectively. In recent years, the demand for electricity has been stretched to its limits in winter. This raised the question of whether renewable energy resources could be utilized to reduce the level of peak demand. Indeed, Cyprus being a Mediterranean island, enjoys an abundance of solar energy, and preliminary studies showed that a considerable potential of wind energy is also available. Utilization of renewable energy for space heating, water heating, pumping and power generation would increase electrical reserve margins, raise system load factor, improve load following capabilities, and reduce the need for capacity expansion. Currently, solar water heating which leads to a saving of at least 72 GWh energy per annum and a significant reduction in CO₂ emission has been extensively used in N. Cyprus. In N. Cyprus, despite the availability of renewable energy resources constructing renewable base-load, electrical power stations has not been found feasible. However, constructing such systems is recommended for two reasons: firstly, as a supplement to saving fuel and secondly, expanding capacity. In this context, the economic analysis for both solar and wind energy systems, has shown a reasonable internal rate of return (IRR). Although, the IRR is higher for wind energy systems, the availability of wind is limited to a few locations and therefore energy distribution is required.     

Energy consumption of a residential building: comparison of conventional and RES-based systems

The energy needs of a typical one-family house in the Thessaloniki area for heating, cooling and domestic hot water production are calculated. The calculations are based on the typical average daily consumption of hot water and on the degree-day method for heating and cooling. The results are finally translated into thermal energy consumption, assuming the typical Greek situation (heating with diesel oil boilers and conventional radiators, cooling with local air-to-air split-type heat pumps and hot water production with electric heaters). The same energy needs are assumed to be covered by a vertical closed loop ground heat exchanger combined with a water-to-water heat pump system with fan-coils for heating and cooling and a thermosyphonic solar system for domestic hot water production. The ground heat exchanger/heat pump system efficiency is determined using data from an existing and continuously monitored similar system installed in the broader area of Thessaloniki. The solar system load coverage is calculated using the f-chart method. The energy consumption of the renewable energy systems is calculated and compared to that of the conventional system. The results prove that significant energy savings can be achieved.