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Presentation on….

Renewable Energy for Cellphone Towers

By

Gururaja Murthy D,Avanthi Raghavendra

M7th sem. B.E(Mechanical)

SDMCET.Dharwad, Karnataka

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Abstract:

In this paper we have presented the availability of electrical power & usage of conventional energy like diesel for cell-phone towers. We have analyzed the load that is required for a cell-phone tower & requirement of diesel per year. Then we have suggested a possible way of reducing diesel consumption by using the available wind energy resources at that site.

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Objective:

To reduce 1. Running cost of cell-phone

towers.

2. Carbon footprints from cell-phone towers.

3. Dependence of cell-phone towers on diesel generators.

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Analysis of the Problem: (1/2)Power required for a cellphone

tower is 3 to 4 kW (i.e. 72 to 96 kWh per day).

According to TRAI diesel consumption by a tower is 8760 liters per year. (considering 8 hours of operation by diesel generator sets per day)¹

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Analysis of the Problem: (2/2)As of January 31, 2013 there are a total of

585,000 cell-phone towers installed all over India.¹

This accounts for consumption of 585000×8760= 5124.6 million liters of diesel per year by cellphone towers.

Total carbon emission on account of diesel use by telecom towers is estimated to be around 10 MT of CO₂ per year.¹

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Methodology:We have considered a cell-phone

tower which is installed in our college as a reference for selection of a wind turbine.

Generally cell-phone towers will be of 35-40 m height. Considering at a height of 25-30m, where we can mount a small wind turbine, the wind speed is found to be around 8 m/s.

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Load Analysis:(1/4)The cell-phone towers will be

sanctioned to use a maximum power of 10kW (150 A, 52V) ² from electrical board. (i.e. rated power)

But the actual power consumption of cell-phone towers will not exceed more than 5kW in normal usage. We can take 4kW as average power consumption by them.

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Load Analysis: (2/4)

Cell sites

Available electricity

Description

10% >20 hrs. Mainly metro cities of Mumbai, Kolkata,

Chennai, some cities of Gujarat, State of

Chhattisgarh, some cities of Punjab

20% 16-20 hrs. Covers most other major cities and towns in rest of the country.

30% 12-16 hrs. All semi-urban and small towns in all States

25% 08-12 hrs. Most rural areas.

15% < 8 hrs. Mostly parts of Bihar and some towns of

Assam, NE states, UP and J&KTable.1-Power Availability for Tower

Sites³

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Load Analysis:(3/4)From table.1 we can say that 40%

of towers are getting power supply for around 12 hrs. only.

So remaining 12 hrs. should be powered by some other means.

- Batteries: 02 hrs. - DGs : 10 hrs.

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Load Analysis:(4/4)Generally DGs will consume 3lts/hr.

to give the required power.

So 30 liters are required per day & 30×365=10950 liters of diesel for every year.

If you consider the average of all towers diesel consumption it will come around 8760 liters per year.

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Available Wind-Speed:

Fig.1 Monthly average wind speed at a height of 25m. ( Hubli-Dharwad region)⁴

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Power output from Wind Turbine:The power equation of a wind turbine

is: P= ½ ῤ A V³ Cp

Where -ῤ is air density in kg/m³, -A is swept area of rotor in m², -V is wind speed in m/s,

-Cp is power coefficient.Theoretically Cpmax = 0.59, but in

practice Cpmax will vary from 0.15 - 0.22.

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Available Wind Power: (1/2)

Using the power equation and the available wind speed, we have calculated the power that can be generated from wind turbine.

General specifications of a small wind turbine:

1. Diameter of rotor= 3m2. Value of Cp= 0.183. Density of air = 1.14 kg/m³

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Available Wind Power: (2/2)

Fig.2 Monthly average Wind power in kW

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Selection of a turbine: (1/3)

The site is very much suitable for a wind turbine of rating 250W for generation of the rated output throughout the year.

According to TRAI, on an average 8 hours power supply will not be there.

So a total of 8×4kW=32kW is to be supplied by DGs.

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Selection of a turbine: (2/3)It will be better if we go for

installation of 4 wind turbines of 250W rating so that we can get: (0.25kW×4)×24hours=24kWh.

The remaining 8kW can be fed by DGs thereby reducing 75% of diesel consumption.

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Selection of a turbine: (3/3)We have chosen a wind turbine, M-300

(a product of Machinocraft Energy Systems) of 300W rated output which is having the following specifications:

Parameter M-300

Rated power(W) 300

Rated wind speed(m/s) 07

Startup wind speed(m/s) 2.5

Survival wind speed(m/s) 50

Rotor diameter (m) 2.5

Rotational speed (rpm) 400(max)

Table.2 Specifications of M-300 Wind Turbine⁵

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Selection of Batteries: (1/3)The storage capacity of batteries

should be around 26kW.

We have the following batteries available in the market:

1. Lead-Acid batteries2. VRLA batteries3. Tubular batteries4. Lithium ion batteries

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Selection of Batteries: (2/3)Out of these it is found that Tubular

batteries are having more no. of life cycles where as Lithium-Ion batteries are having more storage capacities.

Tubular batteries provide a life of around 8-10 years if used and maintained properly.Discharge No. of cycles

80% 1200

50% 2500

20% 5000

Table.3 Discharge & cycles of Tubular Batteries ⁶

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Selection of Batteries: (3/3)We have chosen Corvus energy batteries for storage since it has got greater storage capacity of 6.5kW. ⁷

We will get 26kW of storage capacity if we use four batteries.

Specification

AT6500-250-48

Max volts (V) 52

Min volts(V) 32.4

Current(A) 150

Capacity(kWh)

6.5

Weight(kg) 65

Dimensions(cm)

59×33×38Fig.3 corvus battery Table.4 Specifications ⁷

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Cost Estimation:

Parameter Wind Turbine DGs

Equipment 300000 270000

Storage(battery) 250000 -

Running cost (per annum) - 464280

Total (INR) 550000 734280

• The following table will give you the details of price of the equipment:

Table.5 cost estimation

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Economic benefit analysis:The required power from DGs per year

is 4kW×8hrs×365days=11680kWh.

Of which 1kW×24hrs×365=8760kWh will be generated from wind turbines.

Source of

generation

Total units

generated

Required

units

Energy

saving

Amount saved

(per annum)

Off-grid wind

turbine

8760kWh 11680kWh 75% 348210 INR

Table.6 Economic benefit analysis

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Pay back period:From table.5 the investment on

Wind turbine & batteries is INR 550000

From table.6 the amount saved per annum is INR 348210.

So we can get the invested amount in (550000÷348210) =1.6 years ≈ 2 years.

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Environmental Benefits:Normally one liter of diesel produces

2.65kg of CO₂ emissions.⁸

We have reduced 6570 (75%) liters of diesel consumption per year

We can reduce 6570×2.65kg =17.4Tons of CO₂ per tower and hence can reduce the carbon footprints in the atmosphere.

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Conclusions:We can install small wind turbines

(SWT) on cell-phone towers to reduce the diesel consumption.

Elimination of DGs is also possible if available wind speed is more sufficient to produce the required power of that cell-phone tower.

We can reduce the running cost of the cell-phone towers.

The invested amount will be retained in 2 years

The emission of CO₂ by DGs will be reduced by an amount of 75%.

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References:

¹http://www.thehindubusinessline.com/industry-and-economy/info-tech/telecom-towers-consume-over-5-bn-litres-of-diesel-a-year-deora/article4481889.ece² BSNL Office, Hubli.³Consultation Paper No 3/2011, TRAI, “Consultation Paper On Green Telecommunications”⁴http://www.synergyenviron.com/tools/wind_data.asp?loc=Hubli%2C%20Karnataka%2C%20India

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References:⁵ http://www.machinocraft.com/m300.php

⁶ http://luminousrenewable.com/downloads/Battery-Selection-Installation.pdf.

⁷ http://www.corvus-energy.com/energy_module.html

⁸ http://www.ecoscore.be/en/how-calculate-co2-emission-level-fuel-consumption

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Thank You….