Economical Solar Water Distillation System

Content

Chapter 1: Introduction

1.1 Benefits of distillation

1.2 Renewable energy based distillation system

1.3 Solar energy based water distillation system using HDH cycle

1.4 Basic concept of solar water distillation

Chapter 2: Literature review

Chapter 3: Problem definition/aim and objects

3.1 Problem definition

3.2 Aim

3.3 Objectives

Chapter 4: System components and concept

4.1 Components

4.1.1 Solar collector with closed loop oscillator heat pipe

4.1.2 Humidification chamber

4.1.3 Dehumidification chamber

4.2 Experimental dimensions from literature review

4.3 Concept

Chapter 5: Results

References

List of figures:

1.1 Daily per capita water use by country

1.2 Worldwide use of improved drinking water sources in year 2008

1.3 Distillation method

1.4 Renewable energy based distillation system

1.5 Water cycle

2.1 Schematic of the HDH solar system

2.2 Conceptual diagram of solar power-driven humidification dehumidification system for     brackish desolation

2.3 Baffled solar air heater

2.4 a) schematic assembly of SAH system and

b) Front view of collector

4.1 Solar collector

4.2 Humidification chamber

4.3 Dehumidification chamber

4.4 Schematic diagram of water distillation system

List of table

1.1 Cost comparison

Abstract

The aim of our project is to design a water distillation system that can purify water from nearly any sources, a system that is cheap, portable and and depends only on renewable solar energy.

We get motivation for this project from the problem of limited availability of the pure fresh water resources and abundance of the impure water available which can be converted to potable water.The goal of our project is to produce clean drinkable water efficiently by using solar as source of energy.

We have tried to produce pure water the process of solar water distillation as it is available at free of cost.For the people concerned about the quality of their drinking water and unhappy with other methods of water purification Solar water distillation of the tap water or ground water can proved to be a pleasant, energy efficient option due to it is simple in technology and low energy consumption features.

 

 

 

 

 

 

 

 

 

Chapter 1. Introduction

Every year people use around 4000 cubic kilolitres of water,for the purpose of domestic,agricultural and other industrial purposes.This amount of water use also does not include other consumptive uses such as generation of energy,mining and recreation etc.However there is great difference between consumption of water in the developed and developing regions. For example in the year 2004, average water use per capita in U.S. was around 3 times higher than in India. Figure 1.1 shows great disproportion in average use of water per person per day in the year 2006.The world water demand which is around 4200 cubic litres has become approximately tripled over the past 50 years and is estimated to be about 30% of total fresh water supply of the world. By 2025 this fraction can reach upto 70%.

Fig.1.1: Daily per capita water use by country

In addition to the overall water scarcity of the world there is also lack of clean drinking water.World health organization estimates that globally around 880 million people do not use safe drinking water resources.

In Africa only around 60% of the total population use safe drinking water.These sources include household connection, public water, a borehole, protected dug etc.Figure 1.2 shows worldwide use of drinking water in the year 2008.

Figure 1.2: Worldwide use of improved drinking water sources in year 2008

The overall world population is estimated to grow 9.4 billion by the year 2050 and most of these people will live in the developing countries. Acoording to the current estimations if the people continues consuming water at the same rate than more than 2.7 billion people will face water crisis.

The shortage of the pure drinking water in many areas of the world is now a critical and serious problem. Around 80% of the arid countries like Algeria have periodic droughts.According to the current estimations around 1 billion people are living without adequate water supply and around twice of that live without adequate sanitation.About  97% of the water is saline water of the ocean and only remaining 3% is pure drinkable water . Due to the lifting of ground water higher than rate of replenishment has caused intrusion of the saltwater in coastal areas like Konkan and some other coastal areas also.

Many drinking water sources are also gets contaminated by industrial chemical wastes which increases thenumber of  unsafe water resources for use and the situation got even worse during the season of summer.According to current situation around 45% of the municipal drinking water sources in India are contaminated.

Around  ¾ of the earth surface is covered only with water. Out of which 97.5% water is contained by oceans. So the proportion of the fresh water is only 2.5% of the total water. Out of these less than 1% is available as the fresh water as rest is frozen in glaciers.For the people living in the remote and coastal based areas it is very difficult to provide fresh water. sothe water scarcity problem over a large scale needs to be solved. Efficient management of  the available renewable sources can provide solution of the water scarcity problem.

Water purification the process of removal of the  undesirable harmful chemicals, some biological contaminants, suspended solids etc. from the contaminated water. Most of the  water is purified for the purpose of human consumption i.e.drinking purpose, but water purification may also be done for variety of other purposes, which  includes meeting the requirements of pharmacological,chemical and many industrial applications also.

There are many processes available that can be used for water purification.Out of which water should be purifiedby using less expensive distillation technologies over a wide scale to provide fresh water supply.Although many functional distillation technologies exist but in present there is not any cost effective,highly efficient technique for people living on less than $2/day.Out of the available process for water purification water distillation is one of them. The conventional water distillation technologies includes:

1) Thermal distillation

2) Filtration

3) Separation of  fresh water from concentrate by the use of semipermeable membrane and

4) Chemical distillation techniques.

Thelimitations of these conventional distillation systems are that:

1)Their sizes are large and they requires energy as input.

2)These technologies are standardized and complex.

3) These are difficult to downscale to smaller sizes.

4)Difficult to adopt for  the use in rural areas that desperately needs clean and potable water

5)It requires expertise to operate and maintain the conventional distillation techniques.

6)In remote areas which have neither economic resources to run conventional distillation plants nor infrastructure, thedecentralized water production is important.

In addition to the issue of large amount of energy consumption, most distillation systems using

these technologies are driven by fossil fuels which  results in emissions of green house gas  and  large carbon footprint, which have harmful effects on  environment. Fossil-fuel powered

distillation  plants are subjected to  price volatility and oil availability, which makes energy use quite expensive.

1.1 Benefits  of Distillation:

Finally we decided to go by distillation method owing to the following benefits:

1) Distillation produces water of high quality.

2) Maintenance is almost negligible.

3) Usually any type of water can be purified by means of  distillation.

4)  The system does  not involve any moving parts and no requirement of  the electrical energy for  operation.

5) Minimum wastage of water

Fig. 1.3: Distillation method

Table 1.1: Cost comparison

1.2 Renewable EnergyBased Distillation System

Renewable sources of energy are defined as those energy sources which are available freely in nature and they are never exhausting and they can be continuously renewed and replenished.

Renewable Resources are classified as:

1) Solar Energy

2) Wind energy

3) Biomass Energy

4) Tidal Energy

5) Geothermal Energy

In addition to this it also includes Bio fuel which are harvested without the use of Fossil fuels. Non-renewable energy is costly as they require costly exploration and they will become more expensive as the demand increases. Renewable energy produces less carbon emission and helps in reducing the effect of climate change caused by the Non-renewable resources. Figure 1.4 shows different renewable energy resources.

Especially in developing regions Renewable energy distillation is increasingly considered  for large scale implementation due to the limitations of the conventional distillation technology.These systems can be used in remote regions like some rural villages, coastal areas and small islands which are having  available renewable energy sources. As the supply of conventional energy is not possible always or ii cannot be easily implemented in these isolated regions, renewable energy resouces represent the best possible energy supply option for these distillation systems. Renewable energy based distillation system promotes self-sufficiency. The operation and maintenance of renewable energy based systems in remote areas is generally easier than that of conventional distillation units . Also the implementation of renewable energy based distillation  systems encourages sustainable economic development by the utilization of the  local resources.

Renewable energy based Distillation technologies are quite desirable to reduce the scarcity of energy, environmental impact problems and high cost which are  associated with conventional distillation technologies.

Figure 1.4:Renewable energy Resources

Due the fact that conventional desalination processes consumes high amount of  renewable energy, allows for diversification of available energy resources. This situation helps to  avoid the external energy supply based dependence. Since the last two decades, numerous distillation systems which utilizes Renewable energy have been develop. Most of these plants are developed as small capacity based  research or demonstration projects. Renewable energies and distillationtechnologies can be combined in various manners.

Sunlight can be used as source of heat energy that can be used for purification process when combined with the distillation process. It is not necessary to boil the water to distill it. Rather simply elevating its temperature, some short of boiling, will adequately increase its rate of the evaporation. Although the  vigorous boiling hastens the distillation process it can also force  the undesirable residues  into the distillate thus  defeating the  purification.

Solar energy is a very large and  inexhaustible source of energy. The power from the sun which is  intercepted by earth is approximately around 1.8×1011MW., that is many thousand times larger than the present all commercial energy consumption rate on earth. Thus solar energy could supply all the present as well as future energy needs of the world on a continuous basis. Thus the solar energy one of the most promising of all the available non-conventional energy resources. In addition to its size, solar energy has also two other factors in its favor. First is, unlike fossil fuels & nuclear power, it is an environmentally clean energy source. Second one is that, it is free and is also available in abundant. Solar water distillation is the solar based technology with a very long history and their installations were built over around  2000 years ago, although to produce the salt rather than drinking water. Documented use of solar distillators began in the sixteenth century. The energy which is  required to evaporate the water, called the latent heat of vaporization for the water, is around  2260 kilo joules per kilogram (kJ/kg). It means that to produce 1 litre  of pure water by distilling brackish water requires a heat input of  the amount of 2260 kJ. This does not allow for efficiency of the system or for recovery of latent heat which gets rejected when the water vapour gets condensed.

Although 2260 kJ/kg energy is required for the evaporation of the water, to pump one kg of water through 20m head it requires only 0.2kJ/kg. Therefore normally distillation is considered only where there is no local fresh water  source that can be easily pumped or lifted. Human beings usually  need 1 or 2 litres of water a day to live. The minimum requirement for normal life in some of the developing countries is 20 litres per day .Yet out of all these some functions can be performed even with the salty water and thus a typical requirement for distilled water is usually 5 litres per person per day.

1.3 Solar Energy Based Water Distillation System Using HDH Cycle

 

The concept of  solar energy based water distillation system arrives from the concept of  water cycle.

Nature desalinate ocean water through the water cycle by the use of solar energy in the summer season as shown in figure 1.4. In the water cycle, the portion of the ocean’s surface water is evaporated by the solar irradiation of the sun and the water vapour rises upwards and thus humidifying the surrounding air which acts as acarrier gas. The humidified air will rises, convects and condenses thus forming the clouds. The clouds will then  dehumidify  in the form of  the rain.

The manufactured version of this natural process is known as the humidification dehumidification (HDH)  distillation cycle.

Figure 1.5:Water Cycle

The former of the Humidification-Dehumidification  cycle is the simple solar distillation system. The solar distillation system is similar to a greenhouse system in the way  in which it also  captures the solar energy. The incident solar radiation is transmitted through the glass cover or similar transparent material which has  the property totransmits the  incident  solar radiation and it is absorbed as heat by a black surface in contact with the water in the basin of the distillator. Some of the waterevaporates and the water vapor condenses on the surface of the solar distillator, which is at lower temperature since  it is in the contact with  ambient air and collected for the use.

Solar Distillation system is by far the most reliable, least costly method of  the purification of most types of contaminated water especially in the developing nations where there is a scarcity of the fuel or are too expensive. Solar distillation is used to produce the fresh drinking water or to produce pure water for the purpose of  lead acid batteries, laboratories, hospitals and also  in producing commercial products such as rose water. Conventional boiling distillation systems usually consumes three kilowatts of energy for every gallon of water, while solar distillation system uses only the free pure solar energy of the sun. Expensive filtration and deionizing systems are way too expensive to purchase and use and also they will not totally purify the water by removing all the contaminants present. No additional heat or electrical energy is required in solar based distillation systems and even after the sun sets, distillation also continues at a slower pace into the night. This will increase the efficiency and increases the amount of the  daily pure water production.

Humidification-Dehumidification  process is use the fact or is based on the fact that  air can be mixed with the  large quantities of water vapour. As the temperature increases the vapour carrying capability of the air also increases. The humudification-dehumidification  technique is especially suits when the demand for water is decentralized.

Solar-driven humidification-dehumidification technique  has the  potential to fulfill the water needs of people in remote, coastal areas that has no sufficient access to the freshwater. Considering the application of solar humidification-dehumidification technique in this present  developing world, the challenge for the near future seems to be the development of the small, autonomous,  modular, flexible and reliable units the  reasonable cost, in order to serve the segment/portion of  the isolated users. Although more research is needed on humidification dehumidification and the cost of the system, once the further development in the technology is carried out and proven on a larger scale, it can play a very significant role in increasing the  freshwater supply in many of the coastal areas

Several advantages of this technique include:

1) Flexibility in the capacity

2) Moderate installation as well as operating costs

3) The possibility of using the low-grade thermal energy

4)simplicity

5)Operation of the process is easy and does not requires the skilled operators.

Another advantage  of the HDH process is that is that the recovery ratio, the

amount of water produced per kilogram (kg) of water feed, tends to be lower for HDH

than conventional systems. This feature reduces the need for  the brine pre-treatment or disposal processes. Some pre-treatment or bleeding of the water leaving the humidifier in

closed water cycles is needed, however, to prevent accumulation of salt and fouling of the

heat exchangers in the HDH unit.

1.4 BASIC CONCEPT OF SOLAR WATER DISTILLATION

 

The humidification-dehumidification process consists of the three subsystems:

1) The air and/or water heaters, which can uses heat sources like solar thermal,

2)The Humidifier or the evaporator to humidify the air or to evaporate the water  and

3)The dehumidifier or condenser to get distilled water

Basically in this process, the air is heated and humidified by hot water received from a solar collector. It is then dehumidified by the use of the large surface condenser. Most of the latent heat of thecondensation is used for the purpose of preheating the feed.

1.5 Economics of Solar Driven HDHSystem

 

The main  principal components of the Solar energy driven distillation system using humidification-dehumidification system are the solar collector, the humidification chamber and the dehumidification chamber. The solar collector is the main component of a solar distillation unit and any improvement in its efficiency will have a direct impact on the water production rate as well as cost of the product. The solar collector is very crucial component in the HDH system since it is the majority of the system’s capital cost: around  40-45% for the air heated systems and around  20-35%  for water heated systems. Therefore, it is very  important to ensure the reliability of the solar collector as well as to have a high specific water production.

Specific water production refers to  the amount of water produced per m2 of  the solar collector area per day and also it indicates the efficiency of the  solar energy based HDH cycle. At present scenario there are no commercial systems that utilizes a solar air heater for the purpose of the  solar distillation. Representative values for the air temperature rise and the solarirradiation are approximately 50°C and 1 kW/m2 respectively. Under these conditions the best performing air-heating collector has an efficiency of  around 32% only, where solar collector efficiency is defined as the heat gained by air divided by the total incident  solar radiation. Currently, the prices of  the collectors are relatively so high. Only a reduction in these prices through increased collector efficiency and cost-effective materials will enable the cost of the distilled  water to drop to the economical levels which allows the solar thermal units to compete with the conventional distillation techniques.

 

Chapter 2.Literature Review

1.Energetic and exergetic aspects of solar air heating (solar collector) systems

Hakan F. Oztop,  Fatih Bayrak, Arif Hepbasli

The paper relates the  performance of different  solar collectors used for the purpose of air heating and the different factors to improve the efficiency of the solar collectors.The study of flat plate, finned and v-corrugated solar collectors reveals that the v-corrugated collector is most efficient collector and the flat plate collector is the least efficient. Double pass operation of the collector further improves the efficiency compared to the single pass of operation.The main conclusions are of the study are that Solar air collectors can be used to enhance the temperature of air used in different systems and Body added solar air heaters like V-groove, fin etc have more efficiency than that of flat plate collectors also efficiencies are strongly depended on the solar air heater material.

2. A parametric study on a humidification–dehumidification (HDH) desalination unit powered by solar air and water heaters

Cihan Yıldırım Ismail Solmus

This study is carried out under climating condition of Antalya,Turkey in order to analyse the effect of different parameters such as Air mass flow rate, Feed water mass flow rate, Colling water mass flow rate, Cooling water temperature and collector tilt angle on clean water production rate.The system is opreated on CWOA cycle both heated water and air.

In studied HDH system, Air at ambient temperature is heated by 1^st  pass of double pass solar air heater.Then air heated in second pass and humidified in humidification chamber by seawater heated in flat plate solar water heater.Humidified air is passes to the Dehumidifier and condensed water is collected in collecting tank.There is sufficient portion of energy is stored in insulated storage tank at sunset .Hence, destillation process can be also countinued during night.

The study conclude that as the mass flow rate of air and mass flow rate of feed water increases up to optimum point, fresh water production rate increases but after optimum point, fresh water production rate decreases.To gain maximum amount of fresh water production, collector tilt angle is set to approximately at angle of lattitude.

Fig 2.1: Schematic of the HDH solar system

3. Design, Fabrication and Performance Study of a Solar Air Collector for Room Heating By Forced Draught System in Bangladesh

Asma-Ul-Husna, Md.Harun Or Roshid, Mir Masud Rana, and Md.Rakibuzzaman

The performance of an solar air heater with glass as a cover was designed, fabricated and investigated to heat the room. The heated room can be modified to use as the other purposes like to dry the crops. They concluded that the designed heater with a collector area of 1.23m² is expected to get 10oc temperature difference between inlet and outlet temperature of air with wind velocity of 0.8636m/sec. From the experiment they conclude that the maximum collection efficiency of the collector is increases with increase in temperature difference and maximum value is 32.79% at 1:30 P.M. (In 2009, Bangladesh) and the maximum temperature difference is 10 ° C.

4. Solar power-driven humidification–dehumidification (HDH) process for desalination of brackish water

Jun-hong Wang, Nai-yun Gao, Yang Deng, Yong-li Li

The system mainly consists of three units:Humidifier,Dehumidifier and set of PV power generation unit.In the system, brackish water is pumped by PV driven pump in to heat exchanger as coolant.It absorbs the latent heat of vapor by condensation.Further,the preheated water is pumped in to humidifier in which it  is further heated with PV driven heater to required evaporation temperature. This humidified air enters in dehumidifier. Theair releases latent heat and clean water is collected at bottom of humidifier. Salt crystals are also formed in humidifier as side effect.

Fig 2.2: Diagram of solar power driven HDH system for brackish desalination

5. Experimental study of heat transfer and thermal performance with longitudinal fins of solar air heater

Foued Chabane, Noureddine Moummi, Said Benramache

This study contains comparative analysis of single pass solar air collector with and without fins. Study shows that by increasing the mass flow rate, the thermal efficiency of single pass solar air collector increases. It also reveals that with increase in area of absorber plate by means of providing artificial roughness obstacles or baffles in various shapes and arrangements increases the heat transfer  to the flowing air but also increasing pressure drop in collector i.e., power consumption to pump the air flow to cross collector increases.

6. THEORY  OF  BAFFLED  SOLAR  AIR  HEATERS

HO-MING  YEH

There is considerable improvement in the solar collector performance if the space between absorbing plate and glass cover is packed with iron filling which across the heater is very large which results in high power cosumption.When solar air heater is provided with baffles,there is considerable improvement in collector performance as it generates the air turbulance,creates extended heat transfer area and also reduces the pressure drop in air across the heater.The study shows that as density of baffles (w/d_e or L/l) increases,the collector efficiency increases.

Fig 2.3 Baffled solar air heater

7. The effect of using transverse fins on a double pass flow solar air heater using wire mesh as an absorber

M.F. El-khawajah    L.B.Y. Aldabbagh      F. Egelioglu

This paper shows the analysis of experiment in which wire mesh layers are used between the fins instead of an absorber plate.The experiment conclude that efficiency of solar air heater increases with increase in mass flow rate for range of flow rate 0.0121-0.042 kg/s.At mass flow rate 0.042 kg/s,the maximum efficiency obtains by using 6 fins.Also the maximum average temperature difference between the inlet and outlet, ΔT, for the solar air heater with 6 fins is highest for same mass flow rate.

Fig 2.4 Schematic assembly of SAH system and front view of collector

8. Mathematical Modeling of Bubbler Humidifier for HumidificationDehumidification (HDH) Water Desalination System

 

Hafiz M. Abd-ur-Rehman a, Fahad A. Al-Sulaiman

They develope the analytical model of the direct contact heat and mass transfer bubbler humidifier in that study. This model follows the humidification and dehumidification process which is a carrier gas based thermal technique that is used for a small scale decentralized water desalination system. The inlet temperature of both water and air are important factor that need to be analyzed to evalute the performance of the bubble humidifier. The sum of sensible heat flux and latent heat flux gives the total heat flux in bubbler humidifier. Final results shows the increase in perforated plate hole diameter and water column height slightly decreases the heat transfer coefficient. The increase in temperature difference between water and air stream will increase the efficiency of humidifier.

9. The air solar collector

Ben Slama

In the solar collector provide the baffles plate placed between the insulator and absorber. There are different types of baffles in the market, by using this baffles and compare all parameter. When the baffles provide in collector then decrease the air flow velocity and increase the heat transfer coefficient. By this result the efficiency is goes approximate 75 to 80 % is reached with the best configuration of baffles for an at air flow rate is 50 m³/h. for this condition temperature increase in between the 50 to 60˚c. moreover the fact that place baffles in closed order its very benefit to creation of turbulence in flow rate of air.

10.Experimental and theoretical study of a humidification- dehumidification water desalination system using solar energy

J. orfi, M. Laplante, H. Marmouch, N. Galanis, B. Benhamou, S. Ben Nasrallah, C.T. Nguyen

They study humidification- dehumidification(HDH) water desalination system using solar energy by both method experimental and theoratical.The general mathematical model is based on the conservation principles of mass and energy in each component of the desalination unit.This system is based on humidification- dehumidification(HDH) process and the system has two solar collectors, an evaporator, and a condenser. The get some results of Effect of the water flow rate on the production rate of the fresh water by experiments which is shown in below fig.This results shows that there exists an optimum mass flow rate ratio corresponding to a maximum fresh water product.

11. The air collector

Mohamad

The solar water distillation by HDH system is most use in now a day. Using the multiple condensation evaporation process it conclude that heat collecting capacity depends on the condenser surface area and temperature of the cooling water. The outlet temperature of the collector is 65-75 ˚C that time efficiency of 58% and can be produce 6 L/m2 condensate on 1 m2 collector. By the Aquasolar GmbH & co, is show that SEM 3.6 is most suitable for single family, producing up to 50 L/D.

 

12. Experimental investigation of a solar desalination unit with humidification and dehumidification

Y.J.Dai, H.F.Zhang

The given study presents solar desalination system with humidification-dehumidification process.The system has economic advantages of cost free energy and lower operating costs.The unit also improves the effect of  evaporation and it also overcomes the difficulty of increasing evaporation temperature and decreasing condensation temperature at the same time.The amount of pure water produced  per unit hour of the desalination unit is analysed and it is found out that although system has some disadvantages of lower efficiency it can meet the need of producing the fresh water.

13. Development of an active solar humidification-dehumidification (HDH)

desalination system integrated with geothermal energy

Nabil A.S. Elminshawy, Farooq R. Siddiqui, Mohammad F. Addas

The paper analyses about the  the technical and economic feasibility of using a hybrid solar-geothermal energy as a source in a humidification-dehumidification (HDH) desalination system. The developed HDH system is a modified solar still in which air blower and condenser are used at its inlet and outlet respectively.By using this system fresh potable water can be produced at 0.003 USD/L.Analysis shows that the system performs effectively in areas with geothermal water temperature above 60 degree celsius and mass flow rate below 0.15 kg/s.The benefit of the  proposed system is that it can produce fresh water even in the absence of sunlight by only using geothermal energy.

14. Water Desalination Using a Humidification-Dehumidification Technique-A Detailed Review

A.E.Kabeel, Mofreh H. Hamed, Z.M.Omara

From this literature conclude that the simple conventional solar still is more economical then the active solar distillation system for the domestic application. The humidification and de humidification process suitable for the fresh water production small scale. It a low temperatures process where total required energy taken by the solar. Moreover, HDH is simple in operation and maintenance. When the increase the evaporator and condenser surface area then the high rate distillation water will be taken from the tap water.

15. REVIEW OF SOLAR DISTILLATION METHODS

Hiren Patel,  Mrs. Pragna Patel, Mr. Jatin Patel

By the changing parameter of the different components the output of the system can be change. In the solar heater not use of the metallic materials but use copper-nickel alloys then increase productivity, another change in the solar heater that use the forced convection ,dye and external condensers. A single sloped solar still collect more radiation then the other types the sloped solar still at low and high satiation as the ground level. The modification on the dehumidification chamber the change that, increase of sew water mass flow rate through the system 0.3 liters/s to 0.15 liters/s then the productivity increase to 10% to 14%. From the experiment analyses that flashing process through a super heat liquid jet using sew water at the low pressure. The nozzle diameter is not more then 0.4 mm, pressure is limited up to 6 bar.

16. High efficiency of solar heater

a.a.mohamad

From the compare counter-flow solar air heater and single, double glazing conventional solar air heater result out that flow rate of air varied from 0.005 to 0.2 Kg/ms.The maximum temperature difference in glass cover and ambient temperature for range of air flow rate for spacing between the glass cover and absorber plate is 2.5 to 5 cm. when the increase the space between the glass cover then the absorber decrease the flow velocity,then the heat transfer coefficient decrease. The thermal efficiency decrease flow in double glazing convection air heater without any matrix that time efficiency is 10 to 18% and in the single glazing heater thermal efficiency without any matrix is 18 to 25%. Due to that collector minimum heat loss in atmosphere and maximizes heat transfer in to air stream.

17. Solar desalination with a humidification-dehumidification technique – a comprehensive technical review

Sandeep Parekh, M.M. Faridb, J.R. Selmana, Said Al-Hallaj

From the compare counter-flow solar air heater and single, double glazing conventional solar air heater result out that flow rate of air varied from 0.005 to 0.2 Kg/ms.The maximum temperature difference in glass cover and ambient temperature for range of air flow rate for spacing between the glass cover and absorber plate is 2.5 to 5 cm. when the increase the space between the glass cover then the absorber decrease the flow velocity,then the heat transfer coefficient decrease. The thermal efficiency decrease flow in double glazing convection air heater without any matrix that time efficiency is 10 to 18% and in the single glazing heater thermal efficiency without any matrix is 18 to 25%. Due to that collector minimum heat loss in atmosphere and maximizes heat transfer in to air stream.

 

 

 

 

 

 

Chapter 3: Problem definition/ aim and objects

3.1 Problem definition:

Water purification can be done by many process. In daily life, water is purified by OR purification, UV purification etc., which are highly energy consumable methods. Our project is to distillize the tap water by use of renewable solar energy with the help of Humidification and dehumidification (HDH). As HDH requires less electrical energy to run the system.

3.2 Aim:

The aim of our project is to design a water distillation system that can purify water from nearly any sources, a system that is cheap, portable and depends only on renewable solar energy.

3.3 Objectives:

1. To analyze and determine the main technological characteristics of HDH solar Water Distillation System
2. To promote collaborative initiatives in specific assessment of technical and economic feasibility of HDH solar Water Distillation System.

Chapter 4: System components & concept

4.1 Components

4.1.1. Solar air heater :

Fig 4.1: Solar collector

Evacuated-tube collectors are a more recent technology, introduced in the late 1970s. Several types are available, with the common element being a glass tube surrounding an absorber plate. Because the space inside the tube is a vacuum, which is a far superior insulator than air, these collectors have much better heat retention than the glazing/air space (R-7) design of flat-plate collectors.

Most use borosilicate glass to maximize solar transmission to the absorber plate, and use similar absorber coatings to flat-plate collectors. Frames and manifolds for paralleling multiple tubes are available and can hold 4 to 20 tubes or more. As with flat-plate collectors, multiple banks can be plumbed together to increase system capacity. While overall weights and dimensions are similar between the two types, evacuated tubes usually have an advantage in that individual tubes can be carried to the location and then assembled in place, rather than lifting an entire collector.

The solar air heater is air tight circular collector in which absorber tube is place concentrically of glass tube, between glass tube and absorber tube only air is present and at the both end, neoprene rubber air seals are kept between glass tube and absorber tube which is shown in fig.

4.1.2. Humidification Chamber

Humidification chambers provide a vehicle for imparting moisture and possibly heat to an air stream to assist with patient breathing. The chamber is adapted to hold water in its interior, such that a breathable gas passed over, or through, the water will pick up moisture as it passes through the chamber. In modern chambers the water sprinkles to the hot air which is passes through the humidification chamber. Many such chambers are further adapted to be heated, such that the breathable gas is also warmed as may be desired for many situations. Importantly, it is desired to maintain a sufficient level of water in the chamber to facilitate the desired moisture and possibly heat transfer to the breathable gas.

 

 

 

 

4.1.3. Dehumidifier/condenser

The process in which the moisture or water vapor or the humidity is removed from the air keeping its dry bulb (DB) temperature constant is called as the dehumidification process. This process is represented by a straight vertical line on the psychrometric chart starting from the initial value of relative humidity, extending downwards and ending at the final value of the relative humidity. Like the pure dehumidification process, in actual practice the pure dehumidification process is not possible, since the dehumidification is always accompanied by cooling or heating of the air. Dehumidification process along with cooling or heating is used in number of air conditioning applications.

 

 

 

 

 

 

 

4.2 Experimental dimensions from literature review

 

Absorber tube		Glass tubes
No. of tubes	04	No. of tubes	04
Material	Aluminum	Material	Borosilicate glass
Coating	Dull black powder coating	Emissivity	0.7
Emissivity	0.38	Transmissivity	0.9
Absorptivity	0.9	Thickness	2.2 mm
Thickness	0.6 mm	Length	1500 mm
Diameter	38 mm	Diameter	54 mm(ID) 60 mm(OD)
Length	1510 mm	Collector area	1.65 m2
Spacing between two tubes	650 mm	Spacing between two tubes	30 mm

 

4.3 Concept

The evacuated solar collector absorbs heat from incident solar radiation. The air is provided as inlet to the bottom of the solar collector, it absorbs heat from the collector and air goes to the upwards due to the creation of density difference. Then heated air provided to the humidification chamber. Simultaneously water is sprinkle in heated air. So air gets humidified. The humidified air is further provided to the dehumidification chamber where it condenses. And pure water is produced which is collected in the collecting tank.

Fig 4.4: Schematic diagram of water distillation system

 

 

 

 

Chapter 5: Result

After the experiment, we expect that ppm (parts per million) of tap water is reduced and comes in range required for distilled water.

REFERENCES:

1. A parametric study on a humidification–dehumidification (HDH) desalination unit powered by solar air and water heaters by Cihan Yıldırım Ismail Solmus
2. Collecting performance of an evacuated tubular solar high-temperature air heater with concentric tube heat exchanger by Ping-Yang Wang, Shuang-Fei Li, Zhen-Hua Liu
3. Design, Fabrication and Performance Study of a Solar Air Collector for Room Heating By Forced Draught System in Bangladesh by Asma-Ul-Husna, Md.Harun Or Roshid, Mir Masud Rana, and Md.Rakibuzzaman
4. Development of an active solar humidification-dehumidification (HDH) desalination system integrated with geothermal energy by Nabil A.S. Elminshawy, Farooq R. Siddiqui, Mohammad F. Addas
5. Energetic and exergetic aspects of solar air heating (solar collector) systems byHakan F. Oztop,  Fatih Bayrak, Arif Hepbasli
6. Experimental and theoretical study of a humidification- dehumidification water desalination system using solar energy by J. orfi, M. Laplante, H. Marmouch, N. Galanis, B. Benhamou, S. Ben Nasrallah, C.T. Nguyen
7. Experimental investigation of a solar desalination unit with humidification and dehumidification by Y.J.Dai, H.F.Zhang
8. Experimental study of heat transfer and thermal performance with longitudinal fins of solar air heater by Foued Chabane, Noureddine Moummi, Said Benramache
9. High efficiency of solar heater by a.a.mohamad
10. High temperature collecting performance of a new all-glass evacuated tubular solar air heater with U-shaped tube heat exchanger by Pin-Yang Wang, Hong-Yang Guan, Zhen-Hua Liu, Guo-San Wang, Feng Zhao, Hong-Sheng Xiao
11. Mathematical  Modeling of  Bubbler  Humidifier  for Humidification Dehumidification (HDH) Water Desalination System by Hafiz M. Abd-ur-Rehman a, Fahad A. Al-Sulaiman
12. REVIEW OF SOLAR DISTILLATION METHODS by Hiren Patel,  Mrs. Pragna Patel, Mr. Jatin Patel
13. Solar desalination  with  a  humidification-dehumidification technique  –  a comprehensive  technical  review by Sandeep  Parekh”,  M.M. Faridb,  J.R.  Selmana,  Said  Al-Hallaj”’
14. Solar desalination with a humidification-dehumidification technique – a comprehensive technical review by Sandeep Parekh, M.M. Faridb, J.R. Selmana, Said Al-Hallaj
15. Solar power-driven humidification–dehumidification (HDH) process for desalination of brackish water by Jun-hong Wang, Nai-yun Gao, Yang Deng, Yong-li Li
16. The  air  solar collector by Ben Slama
17. The air collector by Mohamad
18. The effect of using transverse fins on a double pass flow solar air heater using wire mesh as an absorber by M.F. El-khawajah    L.B.Y. Aldabbagh      F. Egelioglu
19. THEORY  OF  BAFFLED  SOLAR  AIR  HEATERS by HO-MING  YEH
20. Water Desalinatin Using a Humidificatin-Dehumidification Technique-A Detailed Review by A.E.Kabeel, Mofreh H. Hamed, Z.M.Omara