2017

Molly Ward, Laurence Skidmore

University of Manchester with Amrita

Vishwa Vidyapeetham University

7/27/2017

Lemongrass Distillery Project

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Contents

Introduction………………………………………………………………………………………………..... 3

History…………………………………………………………………………………………………………3

Aims…………………………………………………………………………………………………………….4

Initial Power calculations……………………………………………………………………………………..5

Amount of LPG needed………………………………………………………………………………………6

PV cells…………………………………………………………………………………………………………7

A visit to the village…………………………………………………………………………………………..8

Discussion of methods………………………………………………………………………………………..10

Boilers…..……………………………………………………………………………………………………..10

Quotations…………………………………………………………………………………………………….10

Calculations for distillation time…………………………………………………………………………….12

How to integrate the hybrid system………………………………………………………………………..17

Development of design 1…………………………………………………………………………………….19

Conclusion…………………………………………………………………………………………………….21

Bibliography…………………………………………………………………………………………………..222

Appendices……………………………………………………………………………………………………23

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Figure 2: 'Current lemongrass

distillery set up'

Introduction:

While being based at the Amrita Vishwa Vidyapeetham Campus in Coimbatore, Tamil Nadu, Molly Ward

and Laurence Skidmore along with two other amrita students will be exploring the use of a Lemongrass

distillery. Currently in the village of Valaramkunum, in the Wayanad district of

Kerala, there is a Lemongrass distillery used to produce lemongrass oil.

Lemongrass oil can be used for a range of items from soap and perfumes to

mosquito repellent. Lemongrass grows abundantly in the areas around the village

which is home to 300 inhabitants in total. There are several tribes within this

village who have their own cultural ways and beliefs. The use of the distillery

allows this abundantly grown plant to be made into a useful product which the

villages can sell and greatly benefit from.

Valaramkunum village was chosen through an initiative called Amrita SeRVe. This

is a program that aims to make 101 places throughout India Self Reliant Villages

that was inspired by the spiritual leader Amma. This includes the villages have a

good source of income, sanitation, education and health. One of the main issues

identified with this village was their source of income which was difficult to come

by due to their unique location.

History:

There are 23 acres of land available in Valaramkunum for agriculture. However, only 4 of which were

being utilised when the project first began through the Amrita University initiative, three years ago.

Originally the village had a batch production distillery system set up but it was highly inefficient. As it

was not a semi-continuous process, once an equilibrium state had been reached production would cease

resulting in far from the maximum amount of oil being produced. In addition the energy source used, fire

wood, was an issue as it was an inefficient source of heat and contributed to deforestation. In addition,

legislation was introduced attempting to reduce the effects of deforestation limiting the access to fire

wood. This resulted in a significant decline in the quantity of lemongrass oil that could be produced and

the majority of villages were forced to travel a round trip of 8km each day for labour intensive

construction or agricultural work, for which there are now almost

entirely dependent on. Here they were often exploited and

underpaid as they were desperate for income.

Through the Amrita Live-in-labs project, after lots of experimental

tests and adjustments, a much more efficient semi-continuous

distillery was set up to produces higher quality lemongrass oil. At

the beginning of the project Amrita students went to the village

and carried out questionnaires to learn about the villages and

what they really needed. The lemongrass distillery was identified

as a clear priority for improvement. Also due to there being a

great problem with alcoholism in the village, mainly with the men

(some of whom at the point where they would prefer to be paid

in alcohol), the project was aimed at working with women. They wanted to help them use the equipment

Figure 1:'SeRVe

poster in the village

of Valaramkunum'

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Figure 3: 'The set-up of a

photovoltaic solar cell'

and pack in the lemongrass as efficiently as possible to get the best results. In addition solar energy was

used for the process, removing the issue of deforestation from collecting firewood. The current set up

utilises sunlight, using a focal point, which is used to directly heat the water into steam necessary for the

steam distillation, as shown in figure 2.Lots of variables needed to be considered while making the design

such as: flow rate, packing density, distillation time and drying time for grass. The final design, calculated

that from the efficient use of 15 acres of farmland, suggests 828litres of oil per year could be collected

from the current set up, providing an additional Rs 800,000 ($12,500) per acre per annum.

This current set up is effective during the sunny months September-May. However during monsoon

season (June-August) the village receives a high amount of rain especially during peak monsoon in June.

In this period there is a lot of over cast and insufficient sunlight harvested to heat up the water.

Therefore there is not continuous revenue from the lemongrass oil business. This can be a big issue for

those whose main income is from the production of lemongrass oil.

Aims:

Therefore, as Material Science and Chemical Engineer students the current task is to work out how to

improve the present situation so that lemongrass oil can be produced all year round even in the rainy

season, or when limited sunlight is available thus improving the villagers income and livelihood. There are

two possible options which will be considered on improving the current set up:

Firstly there is the option of incorporating a Photovoltaic (PV) cell

which still uses the sunlight as an energy source. However, instead of

the light being directly used to heat up the water, the sunlight is

converted into electricity, when it is initially collected, by the

absorption of photons leading to the release of electrons creating a

direct current. Each photovoltaic cell is comprised of two films of

usually silicon (a semi-conducting material). To ensure there is a flow

of current a sandwich of positive and negative charge between the

two layers of semi-conducting material is required. The top layer of

silicon is n-type doped (negatively charged).Donor impurity atoms,

atoms with an extra electron relative to silicon have been added, to

create free electrons available to conduct a current. Silicon has 4

outer bonding elections and phosphorus has 5 so this is used as the

dopant ion. Then the bottom layer is p-type doped (positive charge) by the addition of boron containing

3 outer bonding electrons. The simple set up can be seen in figure 3. This causes an electric field to form

at the point where the two layers meet, arising from the positive and negative doped regions. Then, as

the photons from the sun are absorbed this knocks out an electron allowing it to move and due to the

electric field it will push electrons out of the silicon junction. This leads to an electrical current to

flow(Dhar, 2013). This way the electricity collected from the PV cells can then be used to heat the water

into steam.

This method is superior to the original solar powered system as it allows for the energy from the sun to

be stored and the electricity to build up. This allows for the water to be heated using an electric boiler to

the required temperature and pressure in times of low sun light whereas the previous system would only

function with enough direct sunlight.

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Figure 4: 'A graph to show the

Energy Input versus temperature to

illustrate phase changes'

The second option is to use Liquid Petroleum Gas (LPG) in a gas boiler to complement the solar heater.

LPG is a flammable hydrocarbon gas containing a mixture of propane (C3H8) and butane (C4H10). These

hydrocarbon gases are pressurized causing them to liquefy. LPG is sourced from natural gas and is also

used for cooking, fuel and heating. Natural gas is the most common fuel used across the world, however

it is usually transported via pipes meaning it cannot be easily transported to remote and rural areas. Since

Valaramkunum is in a very rural area, there are no gas pipes therefore LPG would be needed to be

transported in gas canisters up to the village. Even though initially this may seem like the cheapest/

easiest option it also needs to be taken into consideration that LPG will need to be collected from the

villages further down the mountain and then transported up to the tribal area, a big inconvenience due

to the 8 km round trip .This is a significant factor to be considered although this method may eliminate

sunlight as a limiting factor in the production of oil.

During the time on the project consideration will be made for the amount of power required to heat the

water up to the necessary requirements, how much LPG is needed and the cost of the PV cells.

Calculations of temperature change with time within the distillation column will be carried out to

understand the time required for distillation. Therefore further developing understanding of the process

to identify any alterations will be needed to improve the system further. Then quotations will need to be

collected for a gas boiler, electric boilers and PV cells. A verdict will be agreed upon for the best version

of the hybrid system that should be implemented. Visits to the village will be made to see the current set

up of the distillery and potentially nearer the end of the project if further investigation is needed.

Initial Power calculations:

The water for the steam distillation was required to reach 170OC

with a pressure of around 4 bar and mass flow rate of 5kg/hr.

As you can see from figure 4 there are different stages of heating

with energy input. There are two different types of heat: suitable

heat and latent heat. Suitable heat is the amount of heat required

to raise the temperature of one value to another with no phase

change. Whereas latent heat is where a phase change occurs

without a temperature change. A phase change is that which

involves a change in state, for example from liquid to gas or from

solid to liquid. In the calculations necessary for power, latent heat

of vaporisation will be considered because the phase change from

water to steam is the energy intensive stage of this process.

C-D: Suitable heat for water change temperature from 25 OC- 100 OC of

given mass flow rate

D-E: Latent heat of vaporization of given mass flow rate

E-F: Suitable heat of steam change temperature from 100OC - 170OC of given mass flow rate.

With respect to Figure 4.

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Equation required to calculate power (Equation 1):

=mass flow rate

= specific heat capacity of water

Temperature change

Latent heat of vaporization of water

= Specific heat capacity of steam

The energy required in each of the three speperate stages of heating, shown above can be combined get

an overall value of total power needed for distalation.

A 10 - 20% overestimate of the value was calcuated to account for unpredicted heat loss.Using an excel

spread sheet and research, the values of specific heat capacity and latent heat of vapourisation, we

obtained a value of power that would be nessesary to reach the given conditions required.

Table 1: Power calcuations needed for steam to reach required conditions

Power (KW)

Initial calculated value 3.79

Value with 10% buffer 4.17

Value with 20% buffer 4.55

Value of power we aim to supply 5.00

All the values in the table have been calculated through excel which can be seen in appendix A

Amount of LPG needed:

After working out the amount of power needed to ensure the water had reached a temperature of 170OC

at 4 bar, the quantity of LPG needed to provide this amount of power would need to be calculated.

From looking at various sources, the net calorific value - how much heat was given off as it burns - could

be identified. From this it could be calculated how many litres would be required if powered by gas.

It was discovered that 1kg of LPG when burnt gave off 50MJ(Total , 2015).

If 5KJ/s were needed:

If the density of LPG is 0.55kg/l(Total , 2015) (Equation 2)

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Figure 5: 'PV cells present in the

village'

Therefore in one hour 0.00018*3600litres (0.65Liters per hour) would be needed. Complete calculations

are shown in Appendix B.

It should be noted that the heating from LGP will not be 100% efficient. In fact when LGP is burnt on 85%

of the heat is efficiently transferred. However, this is not an issue since in the calculations for power we

added a 20% buffer which takes into account the inefficiencies of heat transfer.

The current cost of LPG (dated 27/07/2017) is found to be Rs49.72 per litre(Economic Times, 2017).

However it has been steadily increasing since march with a rise of RS 9 per litre. Therefore it needs to be

considered that even with the current calculations of overall cost, if the price of LPG were to increase,

this would impact the overall cost in future. Although this value seems small at the moment, if large

volumes of LPG were purchased and transported to the tribal village this will reduce the net profit

available to the villages. This implies it is less likely to be a beneficial long time solution if the price of

natural gas continuous to increase.

PV cells:

Upon arrival at the village we found that there were already many PV cells

in place, used to supply the village with electricity. There are currently two

set ups similar to the one shown in figure 5. The two metal huts built in

the village have the PV cells on the roof with the electricity being stored

within so it can supply the villagers when necessary.

Knowing that PV cells are currently very effective at supplying the villages

with the necessary electricity gives confidence to using PV cells further

supply an electric boiler. Quotations will need to made for initial startup

costs, which may be quite costly. However, little to no running costs

would be involved.

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Figure 6: 'Distillation column'

Figure 7: Solar thermal disc

Figure 8: Focal point

with orientation of disc

being required to

centralise sunlight'

Figure 9: 'Water and oil

separation point'

A visit to the village:

On the weekend of the 28th the team working on the live-in-labs project headed

to the village to do preliminary research on the current set up. In addition they

would to be able see first had the conditions in the village and meet the people

who will benefit from the work being carried out. The Lemongrass distillery itself

would be inspected so any conclusion made will enhance the production of the

oil.

Upon arrival after a ten hour bus journey and a twenty minute trek up a very

steep hill we reached the village. Immediately it was clear that there was

abundant amounts of lemongrass available in the surrounding fields of the

village which can be seen in figure 5. Once ascending to the village we headed

towards the current distillery set up where the lemongrass oil is made, shown

in figure 6, contained within a metal hut. While there our professor on the

project, Dr. Udaya, talked us through the process. This was as follows:

Step 1. The sunlight is collected using a large mirrored

disc with an area of 16m2. This aims the sunlight at

the focal point. As you can see in figure 8 the disc

was positioned so that it would track the sunlight

throughout the day to ensure maximum sunlight was

harvested. Alterations to the positioning of the disc

needed to be made manually once a month to

consider the tilt of the earth, as the sun will be

higher in the sky in the summer compared to the winter. The metal 8mm thick

container is filled with rain water, collected further up the hill. The water is heated

when the focal point is aimed at the centre. As the water vaporises it rises into the

barrel above. Any remaining water moves back down the pipe and is recycled back

towards the focal point. The metal drum, above the focal point, is half filled to allow

for the pressure to build up when steam is produced. Steam remains in the metal

drum until a pressure of 5 bar is reached. At this point, steam is fed into the distillation

column. Temperatures here can reach up to 600 OC and can poetically melt the stainless steel and

insulation if the disc is not correctly positioned can, seen in figure 8. This is

another unforeseen issue that needs to be considered when updating the

current set up, the aluminum is likely to be replaced by stainless steel,

which has a higher melting temperature, in future. This step of heating up

the water to steam usually takes around one hour and thirty minutes.

Step 2. Once the steam has been produced, it is fed into the distillation

column through a pipe at the bottom of the metal drum. The lemongrass

is packed in from the top of the column and the lid is secured evenly with

C-clamps. Silicon nozzles at the base are positioned to spray the

lemongrass with steam produced in the previous step. Silicon was used

due to the material having a high melting temperature, allowing it to

withstand the high temperature conditions. The temperature can be

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Figure 10: ' Inside the distillation

column where steam is spray

from the bottom through silicon

nozzles'

Figure 11: 'Control panel with

colour coding to make it easy to

use'

Figure 12: 'Image to

show the steepness

of the paths up to

the village'

Figure 13: 'Image showing the

team on the project including the

two English material scientists and

Indian chemical engineers'

monitored throughout the process with four different channels. The main

channel monitored is the third one that shows the temperature of the middle of

the column, with the optimum temperature being 150 O C and an ideal pressure

of 1 bar gauge. Per 10 Kg of lemongrass, 200 - 400 litres per hour of steam is

required.

Step 3. With these conditions vaporised oil and steam within the distillation

column are extracted by the opening of the required red nozzle at the top.

A heat exchanger then rapidly cools the vapour, with cold water flowing

through the inside coulomb and the hot vapour on the outside, which

consequently condenses. A steam trap is necessary to catch excess steam

due the high temperatures and pressure. This works using a nozzle with

holes in it which water can get out but steam can only lift up so can't

escape. This stops a pressure build up due to water back flow and so

prevents a catastrophic failure.

Step 4. Due to the oil and water being immiscible they form separate layers,

with oil droplets forming on the surface which are then tapped off. Excess

water can be removed using a glass separator.

The dials are colour coded as the villages are illiterate and would not

understand numbers or the concepts of forward and backwards. This is part

of the training protocol to enable the villagers to learn to operate the

distillation process. You can observe some of the colour system on the

control box in figure 11.

It was clear after our walk up to village that the option of using a gas boiler as

part of the hybrid system would be very impractical. The hill up to the village

was very steep and sometimes slippery. To carry LPG in terrain especially

during monsoon season when there is heavy rain would be very challenging.

Overall the trip to the village was very beneficial in understand the conditions the villagers

are working in and the current distillery set up. This will allow the team to work more

effectively when discussing the options for the hybrid system.

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Discussion of methods

The most important aspect to consider is the sustainability. One of the main goals of SeRVe is to allow

the villages to be self-reliant. With PV solar cells they can obtain all the power required from renewable

resources whereas the option of using gas in the hybrid system involves using an unsustainable source

from fossil fuels. In addition the villages will have to collect the LPG from nearby towns and carried all the

LPG required up the steep hill, potentially in adverse weather conditions.

However it should also be take into account that if prolonged periods of limited sunlight occur, the PV

solar panels may not produce enough electricity to supply the electric boiler.

In terms of cost, if the PV solar panel option were chosen, no additional money would need to be spent

as they are already in place. However, gas would have to be regularly purchased so would eat into the

net income. In addition the increasing LPG cost as discussed above could become an issue.

Boilers

An electric boiler transfers electricity into heat using Joule heating where a current is passed through a

resistor, creating heat. This method can very efficient as only heat is produced. However, larger electric

boilers can be more efficient than smaller ones. Electric boilers are also limited to heating a limited

amount of water at one time. The option to heat more water or increase the rate of heating is also often

not available.

Whereas a gas boiler will be less efficient as well as the purchase of fuel being required. Only around 60 -

70% of the fuel will be converted into electricity upon combustion. However, gas boilers are normally

cheaper to buy and simply burning more fuel to increase the rate of heating or mass water being heated

can be done easily. Gas is often cheaper than electricity supplied from the grid, although this is not an

issue in the situation because the electricity is produced by the PV cells at no extra cost.

Factoring the costs and the manual labour involved with using the gas option it would suggest the

electric boiler is the best option. However up to date quotations of both types of boilers need to be

collected along with further investigation before a decision can made.

Quotations:

Comparison of prices of a variety of gas/electric boilers and PV cells needed to be carried out to get a

understanding of the full cost. It also needs to be taken into consideration that extra pipes, values and

fitting will be needed.

Getting Quotations for the boilers:

From research, a convenient website, www.Indiamart.com was discovered which acted as a comparison

website for electric boiler suppliers. Through Indiamart, enquires were sent to the suppliers of both

electric and gas boilers that seemed to fit the requirements. A call from India mart was received to

confirm our interest in the boilers and ask for our permission to send details on to the chosen suppliers.

Here a potential challenge was realized, as it was difficulty in understanding accents over the phone both

ways, making communication difficult. Later in the day, a call was received from the first supplier from Hi

Therm Boilers PLT. The communication issue was a big problem so the supplier instead emailed the

detailed they needed to know (Boiler capacity and pressure). Communication via email was deemed to

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Figure 14: ' Image of

potential gas boiler to be

used'

Figure 15: ' Image of 5kW

Electric boiler from WGM

Intelligent Automation

Solutions

be a much more effective method and a decision was made to directly email the suppliers, though the

contact information provided by Indiamart. Requests were mainly sent for an electric boiler due to

already having a quotation for a gas boiler, provided in advance by Dr Udaya, and the greater likelihood

of utilising solar PV cells opposed to LPG. The progress of each request was documented on a spread

sheet (as can be seen in appendix C. Colour coding was used to make the progress clear.

In addition, with the suppliers that could not be contacted by email, Añü Deep

made communication via the phone. Also, one of the top choices for companies

is actually based near one Añü Deep's house so is able to visit the head office in

person.

Gas boiler:

Aramama Kitchen Equipment, based in Coimbatore, meeting our requirements

with the stainless steel version costing Rs. 44,000.

Also the supervisor of the project has a quotation for another gas boiler already

so the main aim was looking for electric boilers.

Electric boiler:

After extensive emailling and contacting suppliers two suppliers met the

speciforcations with reasonable prices.

WGM Intelligent Automation Solutions,head quaters at Bangaluru (six hours

away), with an AG-1000 model for Rs. 55,000. Capacity up to 8.4 Kg/ hr. Details can

be seen in an attached document.

Almech Enterprise, based in Coimbatore, with the Mini Boiler model for Rs. 67500

(Stainless Steel version). Capacity of5 Kg/hr. Addition details are shown in an

attached document.

A third quote was received from Hi Therm Boilers, meeting the specifications but

was deemed too expensive at Rs. 135000

Further contact with the supplier can be made closer to the time of purchase

when the hybrid system will be constructed, during the up and coming drier

months by the chemical engineering students based at Coimbatore campus.

PV cells:

Several suppliers were contacted through the Indiamart website and individually. As of yet no quotations

have been received although communication has been made The suppliers of the original PV cells

currently at the village could also be contacted.

With the previous research carried out, extensive quotation collection and a visit to the village, it was

decided that using PV solar cells as an energy source, with an electric boiler producing the additional

steam necessary, would be the superior option. However both options need to still be considered as the

design element of the hybrid system has not yet been looked at.

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Calculations for distillation time:

Previously, the amount of power needed to heat the water in the boiler to 170OC was calculated. The

next stage in the process of producing the oil is the distillation of the lemongrass itself. With this

calculation an extra component needs to be taken into consideration, the oil. For this project it is said

that 10kg of grass per batch is to be used. What amount of energy will be required to distil all the

lemongrass?

Lemongrass has a 2.5 wt.% of oil along with excess moisture present. Similarly with previous calculations,

there will be two stages in heating, the suitable heat to raise the temperature of the grass and the latent

heat of vaporisation for both the grass and water.

Suitable heat for raising temperature of grass (Equation 3):

It is assumed there is a moisture content in the grass of about 45%.

Considering that oil has a low heat capacity relative to the water and lemongrass and a very low mass

present (only 250g), the energy required to heat the oil can be considered as negligible.

When using the equation 3 and substituting in the correct values, around 20MJ of energy is needed.

Heat loss also needs to be considered, with the following assumptions:

One-dimensional steady state heat transfer

Uniform density of container

Constant external temperatures

Time for temperature to reach 170OC is negligible

Heat transfer is via conduction

A time of 1.5 hours for distillation

Considering the distillation column is of cylinder in shape, the following equation can be used to

calculate the heat loss through the walls of the cylinder, including a 6 mm layer of Asbestos used

as insulation. (Equation 4):

As the two materials are in series, the total thermal resistance can be shown as

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Initially equal to zero, the value is kept

shut until the required temperature is

reached.

where R1 is the thermal resistance of the stainless steel and R2 is the thermal resistance of the

asbestos.

(Thermal Conductivity, Stainless Steel) (Engineeringtoolbox)

(Thermal Conductivity, Asbestos) (Engineeringtoolbox)

(Height of cylinder)

(Temperature Gradient)

(Inner Radius)

(Outer Radius, Stainless Steel)

(Outer Radius, Insulation)

A value for heat loss was obtained with and without insulation applied, and showed the insulation

provided a significant reduction in heat loss. Asbestos is ideal for use as thermal insulation with a low

thermal conductivity, required due to the high thermal conductivity of stainless steel.

A value for the total heat required in the distillation coulomb was then calculated, (equation 5). Detailed

calculations can be seen in appendix D.

Next calculations were carried out to determine the variation of temperature within the distillation

column as a function of time, using differential equations. (Equation 8)

Energy in- Energy Out= Accumulation (A) (Equation 6)

= rate change of enthalpy of grass (Equation 7)

(Equation 8)

Only important once T .

When Vapour Pressure Boiler Pressure, vaporisation of the water within the lemongrass

will begin to occur. As time increases so will pressure. It is important that once T is

reached that the amount of water vaporising at T is calculated.

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Equation 8 can be further developed to apply it to the given situation:

If:

(equation 9)

Then can be pulled out the differential due to it being a constant, you get the final equation

(equation 10).

Starting with calculating the temperature change as a function of time up to 100OC, only the first two

sections of equation need to be considered.

As water content is 45% and with a mass of5.25kg of dry grass used, then:

Equation 10 is integrated, values of time (s)are substituted in give temperature as a function of time up

until 100OC. Detailed working can be seen in appendix E with a brief run through below.

=5.25 Kg

= 1500 J/gK

= 4180 J/gK

It is known that accumulation (A) = before the value is opened.

While performing these calculations, there was a realisation that we did not consider the change in

enthalpy with temperature. Once we factored in the temperature dependence of enthalpy the following

boundary conditions could be applied.

When T=300K, t=0. Therefore the below equation is obtained.

6(Equation 11)

After rearranging to make the subject, a graph was plotted to illustrate temperature variations

with time up until 100OC, before vaporising occurs. Therefore at this point the mass of water will change

in the grass and Partial Pressure will be greater or equal to Boiler Pressure.

For part of the calculation a

mixture specific heat capacity will

need to be used since both water

and grass are being heated.

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0

20

40

60

80

100

120

0 200 400 600 800 1000

Tem

pe

ratu

re (

oC

)

Time (s)

T (oC) vs t (s) below vapourisation

0

20

40

60

80

100

120

600 650 700 750 800

Tem

pe

ratu

re (

oC

)

Time (s)

T (oC) vs t (s) below vapourisation

The graph clearly shows a linear relationship between time and temperature up till 100OC, however once

this point has been reached vaporisation occurs meaning the calculations used need to be altered to

observe the trend as time continuous. It can be seen that roughly 11 minutes required to reach the

desired temperature. Furthermore the data suggests that there is no temperature increase until 9

minutes, which could be considered usual. However the main timings which are to be concerned is the

overall time for heating at 11 minutes, which will be confirmed by the supervisor. The results could be

explained by the large distillation column and high volume of grass heated. Heating rate should now be

considered once vaporisation begins.

Firstly, as vaporisation occurs it should be noted that there will be a vapour pressure increase. This can be

calculated using the Antoine Equation, describing the relationship between vapour pressure and the

temperature of a pure compound.

(Equation 12)

Figure 17: ' A graph showing how the temperature changes over time in the

lemongrass distillation column with in input of steam of 5 Kg/h '

Figure 16: ' A graph showing how the temperature changes over time in the

lemongrass distillation column with in input of steam of 5 Kg/h '

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There are two versions of this equation that can be used where the temperature and pressures units and

different. For this version Kelvin and Pascal's are used.

A,B and C are specific constants for certain pure compounds. For this calculation the values for water

above 100 OC are needed:

A=3.56

B=644

C=-198

(NIST , 2017)

The Antoine equation is used to calculate in equation 13, below.

The equilibrium situation is then considered in equation 14.

(Equation 13)

(Equation 14)

The operating temperature is 1.4 bar and is already known. Therefore can be calculated for equation

10.

Similarly to the calculations carried out before vaporisation, integration and rearranging of the equation

10 needs to be carried out, this time including the end segment (considering vaporisation).

To find equation 14 is used.

Re arranging then integrating equation 14:

However, a mistake was made somewhere in this calculation and the value for the time required was

unrealistically high. But due to illness, our supervisor being unavailable for consultation and a shortness

of time, the calculation was unable to be corrected. However we may be able to correct the calculation

at a later date, when back in the UK.

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Figure 18 : 'Shown the layout of

design plan 1 for the hybrid system'

How to integrate the hybrid system

After the calculations for the distillation and boilers, it should be considered how the boiler will be

integrated into the current system.

Things to consider:

Combined flow rate of solar thermal steam and steam produced from electric/gas boiler needs to

equal 5kg/h.

Requires a system which has an equilibrium state, so as solar thermal steam flow rate slows

down then more steam is required from the electric/gas boiler.

Pressure build up will need to be carefully monitored.

Minimal heat loses in transportation of steam.

How to feed the water into the boiler.

Cost of alterations to the original design.

Location of manufacturing source, needs to be nearby such that any faults with equipment can

be easily fixed.

Design plan 1:

This design would mean minimal alterations to the current design, due to simply being able to feed in

another pipe contain the steam produced from the electric/gas boiler. However, monitoring of the steam

produced from the solar thermal heating would be needed to ensure there is a constant flow rate of

5kg/hr into the distillery. Therefore the mass flow rate would need to be measured at points A and B and

equate to 5kg/hr at point C. A system would need designed to measure the flow rate at these three

points to keep a constant balance. A way to supply the boiler with sufficient water would also have to be

found. A third concern is that a 5 bar pressure is required to be reached before steam can be released in

mass

flow

rate C

mass flow rate B

mass

flow

rate

A

Electric / gas boiler

Solar

thermal

disc

Water drum

Focal

point Distillery

18 | P a g e

Figure 19 : 'Shown the layout of

design plan 2 for the hybrid system'

Figure 20 : 'Shown the layout of

design plan 2 for the hybrid system'

the current set up. With low sunlight, this might not be reached, so the solar PV heating may be over

relied upon compared to the alternate options.

Design Plan 2:

With the current set up having the distillation column inside the metal hut to keep it protected from the

elements the gas/electric boiler would also need to be covered. When considering this option, the steam

would need to be pumped out of the hut to the water drum until a 5 bar pressure is reached, then back

into the distillery. In this time there could be a sizable heat loss, making it more inefficient, suggesting

this design is not the best option. Furthermore care would need to be taken with feeding in the steam so

the pressure build up isn't too high although the remainder of the distillation set up would not need to

be changed.

Design Plan 3:

mass

flow

rate C

mass flow rate B

mass

flow

rate

A

Electric / gas boiler

Solar

thermal

disc

Water drum

Focal

point Distillery

Electric heater

Solar

thermal

disc

Water drum

Focal

point Distillery

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Figure 18 : 'Shown the layout of design plan 1 for the hybrid

system'

Design plan 3 involves inserting an electric heater into the water drum to directly heat the water and

compliment the solar heating within the drum. Considering this design, the heat supplied to the water

from the electric heater would have to be controlled to avoid overheating, as this could lead to a

pressure build up. In addition, the potential for corrosion or the build-up of scale on the heater would

have to be investigated, as this would reduce the efficiency of the heater. This, in concept, may be the

simplest option but could be the more difficult to implement, as with design 2 a new drum would need to

be installed along with temperature and pressure monitors, and would not be available for a gas boiler

After considering the different designs it is clear that option one would be the most suitable for the

particular set up. It will involve the least alterations along with being one of the easier designs.

Development of design 1:

For all these different designs the main

variable that needs to be considered is the

mass flow rate which always should be

equate to 5kg/hr, no matter the

contribution of the solar thermal set up.

Therefore this needs to be measured using

a mass flow rate meter. Since design one is

being used there would be two mass flow

meters at point A and point B shown on

design plan 1, figure 18. When putting the

theory into practice, the ideal situation

would be to insert the steam boiler close to

the distillery column, so that less heat is

lost during transport along pipes. The

current steam inlet is a point A on figure

6before the pressure gauge. For this a T shape pipe will need to be installed.

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Figure 21 : ' Design plan

for integrating both

boilers in the hybrid

system'

Figure 6 : 'Distillation column'

Main alteration to consider:

Connection from solar PV source to electric boiler

Connection from rain water collection site to electric boiler

Monitoring of mass flow rate from solar thermal steam

Control over mass flow rate from boiler to ensure mass flow rate of 5kg/hr

Addition of junction for two types of steam

Potential valve to prevent backflow of steam

Mass flow controllers can be used to measure and manage the rate of steam that will flow into the

boiler, but will be calibrated to a set value. In this case the value may need to vary depending of the

volume of steam produced from the solar thermal set up.

Due to starting a week late, we were unable to progress any further so additional research will be

untaken by the two permanently placed chemical engineering students, who are completing this as their

final year project. We have come to a conclusion over the hybrid system and the theory will be put into

practice by Añü Deep and Akhilesh Ravindran.

A

Steam from

gas/electric

boiler

To ensure only a capacity of 5kg/hr of steam enters

the distillery column there will be varying but

continuous flow of steam produced from the solar

thermal system, then additional flow from the boiler.

The main task is to control the mass flow rate of

steam from the electric boiler with varying mass flow

rates from the solar thermal system. Safety measures

will need to be implemented to ensure there is no

pressure build up leading to catastrophic failure.

Options such a computer chip monitored system will

need to be considered.

Valve to

prevent back

flow

Steam from solar

thermal

Electric boiler

Mass flow

rate meter

Mass flow

rate meter

21 | P a g e

Unfortunately, due to the limited time and resources available the research will have to be continued by

the two chemical engineering students, who will be based on this project for the following two years,

rather than ourselves. With the time on the project coming to an end we are unable to provide

contribute further.

Conclusion

During the time spent at Coimbatore Amrita Vishwa Vidyapeetham campus a lot of the theory work

behind the hypothetical hybrid system has been carried out. The unpredictability of projects such as this

require flexible working and being open to doing whatever work was necessary to push progress

forwards.

Initially we were under the impression most of our time on the project would be spent in the village

building the hybrid system, when in fact, the project was in earlier stages. Power and heat calculations

still needed to be performed to determine the energy needed for the system. Quotations were needed

for electric boilers, gas boilers and PV cells. This task was very successful considering the language/accent

barrier issue. Different set ups for the hybrid system were considered and a decision was made on the

most effective design. In addition, being 2nd year Material Science students some of the calculations were

unfamiliar. However, with occasional lecture style sessions with Dr Udaya(our supervisor for the project)

a greater understanding of the maths and workings was obtained. With the struggles of having people

swapping projects, dropping out and lost luggage, we arrived at the project a week behind schedule.

Therefore a lot of work had to be done in the now limited three and a half weeks which were available.

All things considered we believe we were very effective with our work and completed as much as

possible in the time available.

What is important is that the preliminary stages of the project where still carried out and the top choices

for the boilers have been made, allowing the next stages of the project to begin with those still on the

project. It should be mentioned that this project has already been running for three years and is expected

to continue for two - three further years until the village is fully self-reliant. It will be exciting to hear

about the progress made in future and how the work that has aided in moving the project forward.

Participating in the project has been highly beneficial for us both. We have gained an invaluable life

experience along with learning a lot more technical skills in addition to consolidating what we have learnt

over the past two years at the University of Manchester. We have had to be flexible and adapt to

changing circumstances and hope we have given as much to the project as we have gained in return. We

will aim to remain in contact with everyone based on this project and will provide any further assistance

should it be needed. It has been a thoroughly enjoyable experience and we hope that we have helped

the process of the project as much as we can in the time spend at the campus.

22 | P a g e

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https://www.livescience.com/41995-how-do-solar-panels-work.html

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http://economictimes.indiatimes.com/industry/energy/oil-gas/lpg-prices-raised-by-rs-86-steepest-

hike-in-indias-history/articleshow/57416002.cms

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from Engineeringtoolbox: http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

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Appendix A

Appendix B

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Appendix C

Appendix D

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Appendix E