Techno-Economical Analysis of Built-in-Storage Solar Water Heating System in Pakistan

Transcription

1 Techno-Economical Analysis of Built-in-Storage Solar Water Heating System in Pakistan R.A. Jabbar Rachna University of Engineering and Technology, Gakhar, Gujranwala, Pakistan ABSTRACT Energy is an essential element for continued human development and economic growth. Providing adequate and affordable energy is essential for eradicating poverty, improving human welfare, and raising living standards worldwide. For sustainable development, it is crucial to ensure supply of adequate, consistent and secure supply of energy. Renewable energy is being rapidly promoted all over the world due to its distinctive advantages renewable resources are abundant, inexhaustible and environmentally friendly. Solar water heating is one of the most prominent and fast growing renewable energy technologies. Solar water heating has huge applications within domestic and industrial sectors in Pakistan. This work provides a brief overview of the present energy equation of Pakistan and an analysis of hot water requirements in the country. As part of the presented work a built-instorage solar water heater of 80 litres capacity has been developed and installed in Pakistan. Results of the installed system have been measured over a period of three months. The monetary and embodied energy payback periods for the installed heating system have respectively been found to be 1.4 years, and 191 days. The Carbon pay back period for the system has been calculated to be equivalent to 176 days. It has also been found that that over the life time of 20 years the solar water heater has a potential of delivering 21.5 MWh of energy thus having a life time saving potential of USD INTRODUCTION Prosperity in any society is subject to an adequate and consistent provision of energy. It is crucial to adopt energy strategy with least dependence on vulnerable energy supply channels such as imported oil from foreign/overseas countries. Such strategies must be multifaceted - should enhance the use of renewable, next-generation energy resources, conserve energy resources by increasing fuel efficiency, and increase domestic supplies of conventional energy resources. M. Asif School of Engineering, Napier University, 10 Colinton Road, Edinburgh, EH10 5DT, UK m.asif@napier.ac.uk The depletion of fossil fuels which contribute to 80% of world s primary energy supply, and environmental impacts associated with presently used energy modes have emphasised the need for an alternate solution to meet global energy needs without inflicting any serious environmental impacts. Renewable energy sources are the answer to these energy and environmental challenges. Renewables such as solar, wind, hydropower and biogas are potential candidates to meet global energy requirements in a sustainable way. Solar energy has the potential, not only, to play an important role in providing most of the heating, cooling and electricity needs of the world, but also to solve global environmental problems. The most wide spread thermal use of solar energy, so far, has been for water heating. Solar water heating is an energy efficient, cost effective and environmentally friendly renewable energy technology that has a huge potential in domestic and industrial applications. For most countries around the world solar water heaters can provide up to two-thirds of the total hot water requirements cutting down the energy cost and also the associated environmental impacts. The efficiency and reliability of solar water heating systems have significantly increased over the last three decades while the cost has come down. Improvements to materials, a rating system for consumers, and more attractive designs, have all helped to make systems more successful. In particular, over the last ten years there has been a significant increase in the use of domestic solar water heaters across the world. In 2003, solar water heaters received 21% share of the total investment, US$22 billion, in renewable energy sector worldwide [1]. China, for example, a leading player in solar water heating market, saw its solar water heating market grow by 30% in the year [2]. The present work aimed to study the prospects of solar water heating in Pakistan. Built-in-storage type of design has been adopted in the work due to its favourable characteristics. The heating system consisted of an 80 litres capacity heater that was locally developed using the technology available within Pakistan. The heater was operated for 2 months to gather the data to evaluate its performance. Results of technical and economical assessment have been presented in the work.

2 2. SOLAR WATER HEATING A solar water heater utilises solar energy to heat water. Solar water heaters can operate in any climate. Performance varies depending, in part, on how much solar energy is available at the site, but also on how cold the water coming into the system is. The colder the water, the more efficiently the system operates. Solar water heaters can provide significant fiscal advantage since they have quite a small pay back period. In addition to the financial benefits, substantial an amount of emissions, such as carbon dioxide, sulphur dioxide and the oxides of nitrogen (CO 2, SO 2 and NOx) can also be avoided with the use of solar water heaters. Solar water heaters are normally made up of collectors, storage tanks, and, depending on the system, electric pumps. There are three basic types of collectors: flat plate, evacuated-tube, and concentrating. Solar water heaters can have active or passive water circulation system; the former uses an electric pump to circulate water while the latter has no pump. Solar water heaters with flat plate collectors normally come in two main types; built-in-storage and thermosyphon. A Built in storage water heater combines flat plate collector and storage tank in one unit. The built-in-storage heart possesses several advantages over the thermosyphonic type. These are as follows: Higher efficiency owing to the fact that firstly, no thermal losses occur while water is flowing through connecting pipes, and secondly owing to no loss of efficiency due to poor bond conductance (between the plate and tubes of a collector used in thermosyphon system) and fin efficiency which may occur in the less expensive flat-plate collectors. Also they are compact in structure, which is not the case with thermosyphon system and is a draw back from the aesthetic standpoint. Moreover built-in-storage heaters are cheaper due to their simplicity of construction [3]. Solar water heating, besides its domestic role, has a wide array of applications within commercial (such as swimming pools, laundries, hotels and restaurants) and industrial sectors (such as food and beverages, process, and textile industries). Around the world, water heating accounts for as much as % of the total energy consumed in domestic sector. In the USA and UK, for example, water heating respectively consumes 18 and 23% of the domestic energy [4, 5]. While in the industrial sector, water heating may account for a significantly higher share of energy. In the textile sector, for example, water heating can account for as much as 65% of the total energy used during process such as dyeing, finishing, drying and curing [6]. The efficiency and reliability of solar water heating systems have significantly increased over the last three decades while the cost has come down. Improvements to materials, a rating system for consumers, and more attractive designs, have all helped to make systems more successful. In particular, over the last ten years there has been a significant increase in the use of domestic solar water heaters across the world. In 2003, solar water heaters received 21% share of the total investment, US$22 billion, in renewable energy sector worldwide [7]. China, a leading player in solar water heating market, saw its solar water heating market grow by 30% in the year On the other hand several European countries are experiencing an even healthier growth. Reported figures indicate a healthy growth in 2004 in several countries, even though the total market is still small. Belgium s market grew by 62%, Estonia by 67%, Hungary by 50%, Ireland by 67%, Malta by 41%, Portugal by 67% and Slovenia by 64% [8]. 3. ENERGY BUDGET OF PAKISTAN Pakistan is a fossil fuel based energy economy that heavily relies on imports of fossil fuels to meet its energy requirements. Pakistan s commercially exploitable energy resources consist of coal, gas, oil, hydropower, nuclear power and a large base of traditional fuels in the form of fuel wood, agricultural and animal wastes. An analysis of Pakistan s energy supply market indicates that the country is a net importer of energy. The current energy supply matrix is a composite of various technologies. Oil and gas form the bulk of primary commercial energy supply mix of Pakistan, contributing 82.5% (oil: 38.3%, gas: 43.8%, LPG: 0.4 %,) as shown in Fig. 1 [9]. The other sources include; coal: 5.4%, hydro electricity: 11.3% and nuclear electricity: 0.9%. The installed electricity generation capacity in Pakistan on June 2005 was 19,379 MW comprising 6,494 MW of hydro, 9,254 MW of gas fired, 3,019 of oil fired, 150 MW of indigenous coal fired and 462 MW of nuclear. Figure 2 shows a Sankey diagram for the energy matrix of Pakistan for the year 2005 [10]. The per capita primary commercial energy consumption of the country in was approximately 0ne-fifth of that of the world average. Over the same period, the per capita electricity generation was 562 kwh and consumption was 402 kwh. While the world average per capita electricity consumption was about 2,429 kwh, six times greater than that of Pakistan [11]. Import ed oil 32% LPG 0% Hydro 11% Indigenous oil 7% Nuclear 1% Coal 5% Gas 44% Fig. 1 An overview of primary energy market for Pakistan,

3 Presently, Pakistan is facing severe energy challenges indigenous oil and gas reserves are running out, energy demand is rapidly increasing, gap between demand and supply is growing, concerns about secure supply of energy are increasing and fuel cost is rising at an unprecedented rate. For sustainable development, it is crucial to ensure supply of adequate, consistent and secure supply of energy. Renewable energy resources that are sustainable are abundantly available in Pakistan in various forms such as hydelpower, solar energy, wind power and biomass. To address the growing energy challenges, it has become inevitable for the country to diversify its energy market through harnessing renewable energy resources. the total energy consumption in textile industries [12]. Hot water is also essential in a number of other industries such as chemical, food and beverages, and hotel and tourism industries. Based on the energy consumption figures within domestic and industrial sectors in Pakistan, it has been estimated that water heating accounts for 10-12% of the total national energy demands. The significance of solar water heating can also be highlighted from the perspective of its environmentally friendly characteristics. Pakistani textile industry is facing a tough challenge in the form of global environmental standards. To sustain its role in export markets, Pakistan has to comply with international environmental protocols. Pakistan Agricultural Research Council has warned that Pakistan's textile exports face a bleak prospect in the coming years unless the government adopts focussed measures to address the concerns relating to environment and updating of technology. In fossil fuel run textile units, toxic emissions into the air and ground water are the major environmental concerns. 5. THE DEVELOPED SOLAR WATER HEATING SYSTEM 5.1. CONSTRUCTION OF SOLAR WATER HEATER Figure 2: Energy flow chart for Pakistan (Values provided in Millions of Tonnes oil equivalent) 4. SOLAR WATER HEATING APPLICATIONS IN PAKISTAN Pakistan has huge demand for water heating in domestic and industrial sectors. It is reported that almost 44% of the total primary energy in Pakistan goes into domestic sector. Hot water also accounts for a substantial portion of energy consumed in domestic sector. Similarly the demand for water heating is enormous within the industrial sector. The local textile industry has been the backbone of Pakistan's economy. It contributes more than 60% to the total export earnings of the country, accounts for 46% of the total manufacturing and provides employment to 38% of the manufacturing labour force. Hot water accounts for as much as 70% of The solar water heater was constructed by the research team using locally available technology in Pakistan. The two main components of the developed heater were water storage tank and insulation envelope. Water storage tank also plays the role of thermal collector by absorbing incident solar radiation. The water storage tank consisted of 1 mm thick sheet of base material and had dimensions of 1m х 1m, with a depth of 0.08m. The capacity of the water storage tank thus is worked out to be 80 litres. The tank was constructed through bending and welding of 1 mm thick aluminium sheets, which formed the top, bottom and sides. The top surface of the steel boxes was painted with blackboard paint to act as the absorber plate. Water inlet and outlet valves, each of the size of 0.025m, were respectively provided on the side and top of the box. The storage tank needs to be insulated to protect from convection heat loss. For this purpose, the storage tank was wrapped with 0.05m of glass wool insulation on all sides and bottom and housed in an outer wooden box. The top black painted surface of the box was covered with a 4mm thick glass sheet to maintain an air gap of 0.025m. The steel assembly was used to mount the heater at an angle of 22, this being the optimum angle for maximising the annual solar gain OPERATION OF SOLAR WATER HEATER The solar water heater was fully instrumented to enable the measurement of hourly variation of ambient air and water temperature and its longitudinal stratification. A

4 total of five thermocouples were used to measure the longitudinal temperature stratification within the heater by means of a direct temperature read-out device. The ambient temperature was recorded via thermocouples as well as a Stevenson screen based mercury-in-glass thermometer. The heater used to be filled in with fresh water every morning at 6 am and drained out at 5pm. The data were recorded between these hours on an hourly basis. Bearing in mind that the main purpose of the experiments was to obtain the value of the bulk temperature of the heated water at the days end, the entire body of heated water used to be discharged in an insulated drum and the water used be stirred well in order to obtain the mixed water temperature. Over two months of performance data were gathered to analyse the performance of the developed heater THERMAL PERFORMANCE OF SOLAR WATER HEATER The developed solar water heater was operated over a period of two months, from 20 April to 20 June The results for 60 days were available to investigate the performance of the heater. It has been found that during this period, on average daily basis the heater increased the temperature of 80 litres of water by 40.1 C. The average daily energy output from the heater is calculated to be 3.7 kwh (13.3 MJ). Referring to work done by Muneer and Asif [4], the average daily energy out put of the heater over one complete year has been estimated to be equal to 2.92 kwh (10.5MJ). The average daily input, energy received by one square meter surface area of thermal collector, as obtained from the work of Raja [13], is calculated to be equal to 4.8 kwh (17.25 MJ). The efficiency for the solar water heater therefore has been found to be 60% ECONOMICS OF SOLAR WATER HEATER The total cost incurred during production of solar water heater has been calculated to be USD 54. Based on the average daily energy output from the heater the annual energy output has been estimated to be equal to 1075 kwh (3870 MJ). In industrial applications normally furnace oil is used to generate energy. The price of furnace oil has rapidly increased over the last few years as shown in Fig 3. Comparing against industrial applications, an economic payback for the developed heater has been calculated to be equal to 1.4 years as shown in Table 1. It is also important to keep in mind that the consistent and rapid rise in the fossil fuel price is bringing down the pay back period for solar water heating at same speed. It has also been estimated that over the life time of 20 years the solar water heater has a potential of delivering 21.5 MWh of energy thus having a life time saving potential of USD3506. Price of furnace oil (USD/MWh) LIFE CYCLE ANALYSIS OF SOLAR WATER HEATER The LCA investigations carried out for the presently designed solar water heater cover embodied energy and environmental impacts associated with the construction of the heater. Estimates for the total embodied energy of materials involved have been determined. The main materials involved in the construction of solar water heater include: aluminium, glass, glass wool insulation, galvanised steel and rubber. Based on embodied energy figures for the respective materials provided by Berg [14] and Buchanan [15], total embodied energy of the solar water heater has been calculated to be equal to 2013 MJ. Environmental impacts associated with the heater have been expressed in terms of carbon generated by each material during its production. Table 1: Life cycle assessment of solar water heater Entity 1984 Quantity (kg) Embodied energy (MJ) Carbon released (kg) Monetary Costs (USD) Aluminium Glass Glass wool Rubber Galvanised steel Brass General steel Total Annual saving Payback period -years (days) (191) 0.5 (176) Table 1 summarises the results of embodied energy and environmental impacts estimations of the heater. Keeping in mind the average daily amount of energy produced by the heater, the embodied energy pay back 1994 Years Figure 3: Furnace Oil Prices for Power Sector in Pakistan ( ) (500)

5 periods for the heater has been calculated to be equivalent to 191 days. Basing on the Carbon emission values, as provided by Berg [14], for the individual materials used in heater construction, it has been estimated that the amount of Carbon released during construction of heater is 36.7 kg. Comparing against furnace oil run industrial applications, the annual Carbon saving from the solar water heater has been calculated to be equal to 76 kg, thus giving a Carbon payback period of 176. [13] Raja, I. and Twidel, J., Statistical analysis of measured global insolation data for Pakistan, Renewable energy, 4, 1994 [14] Berge, B., The Ecology of Building Materials, Architectural Press, [15] Buchanan, A. and Honey, B., Energy and carbon dioxide implications of building construction, Energy and Buildings, CONCLUSIONS Solar water heating has enormous scope within domestic and industrial sectors of Pakistan especially in textile industries where hot water accounts for as much as 70% of the total energy demands. It has been found that solar water heating has significant fiscal and environmental advantages. The economical payback period for solar water heater has been found to be equal to 1.4 years. The embodied energy payback period has been found to be 191 days. It has been estimated that the amount of Carbon released during the construction of heater is Annual Carbon saving for the heater has been calculated to be equal to 76 kg respectively thus giving a Carbon payback period of 176 days. REFERENCES [1] Annual investment in renewable energy: ; Renewable Energy World; February [2] Solar Thermal Systems on the Up; Renewable Energy World; July 2005 Refocus, Volume 5, Issue 3, pp 18-21, [3] T. Muneer, S. Maubleu & M. Asif, Prospects of solar water heating for textile industry in Pakistan, Renewable & Sustainable Energy Reviews, 10, 2006, [4] Muneer, T.; Solar Energy, KEMPS Engineering Year Book; Miller Freeman; [5] 6&CategoryID=949 (Accessed October 2005) [6] Vijayaraghavan, S. Encyclopaedia of energy; Volume 5; Academic press; London; 2004 [7] Annual investment in renewable energy: ; Renewable Energy World; February [8] Solar Thermal Systems on the Up; Renewable Energy World; July 2005 [9] Fossil fuel overview, Ministry of Petroleum and Natural Resources, Islamabad, Pakistan; [10] Pakistan Energy Yearbook 2005, Hydrocarbon Development Institute of Pakistan, Islamabad, Pakistan. [11] Energy Information Administration (EIA), [12] Encyclopaedia of energy, Volume 5, Academic press, London, 2004.

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