Harnessing the Thermoelectric Effect for Sustainable Energy Solutions

Abstract

The thermoelectric effect has been proven as a source of cooling and small power generation as defined by the Peltier-seeback effect.Thermoelectric modules,optimized by semiconductors, have been used for temperature regulation by operating as a heat pump to maintain computing devices and integrated circuits at optimum temperatures for improved processing efficiency.

Thermoelectric modules have also been used to capture microwatt electrical power from personal computing and other small scale devices by way of utilizing the waste heat rejected through its heat sink.

In modern data centers and server farms,water method cooling of electronics has been widely adapted as a more efficient cooling method than standard air conditioning and ventilation system due to its vastly larger thermal capacity.However, even high density electronics cabinets and processing units for waste heat recovery by standard thermodynamics cycles and heat pumps.When applying the thermoelectric effect to the temperature difference between the heat source of the processing electronics and the heat sink of a water cooling system,potential exists for practical and economic energy recovery.

Indroduction

Problem Statement

It is very difficult to transmit the electricity everywhere like at military camp, mountainous area, where there is no electicity that is why people suffer from various hazards.In hospitals because of absence of electricity sometimes the expensive medicines, vaccines are useless.Because of compressor the chloroflurocarbon also produces.which is very harmful for us.It is also not portable.

Objective

Our main objective is where the electricity is not available there this prototype will be applicable like at military camps, at hospital , at mountainous place.

It is solar based so no need of supply for this refrigerator.It is also pollution free.It doesnot produce chloroflurocarbon.It is compressorless so cost and weight also less.

Literature Review

For building this project we researched about the following: The study shows how the manufacturer’s datafor thermoelectric cooler as well as for thermoelecrric generators can be used to extract parameter of the proposed model.The model could be helpful for analyzing the drive requirement of TECs and loading effect of TEGs.Another important application pf proposed model is when the performance of the TEM needs to be analyzed under specific conditions such as heat leakage,non-ideal thermal insulation etc.Using the model can analyzed not only existing modules,but also specify an optional module for a specific problem.The present model is compatible with electric circuit simulators for DC,AC and transient simulation types and will thus be an excellent tools for solving problems of temperature control.

Components

1. Thermoelectric Module
2. Solar Panel
3. Heat Sink
4. Charging Circuit
5. Regulator IC
6. Power Supply
7. ON/OFF Switch
8. Temperature Display
9. Wire
10. BLDC Fan

Thermoelectric modules are operate on the peltier effect.The peltier effect is a temperature difference created by applying a voltage betwwn two electrodes connected to a sample of semiconductor material.This phenomenon can be useful when it is necessary to transfer heat from one medium to another on a small scale.

The solar panel converts sunlight into DC electricity to charge the battery. This DC electricity is fed to the battery via a solar regulator which ensures the battery is charged properly and not damaged. DC appliances can be powered directly from the battery, but AC appliances require an inverter to convert the DC electricity into 240 Volt AC power.Some DC appliances can be connected to the regulator to take advantage of the Low energy Disconnect and protect your

A heat sink transfers thermal energy from a higher temperature device to a lower temperature fluid medium. The fluid medium is frequently air, but can also be water, refrigerants or oil. If the fluid medium is water, the heat sink is frequently called a cold plate.heat sinks for electronic devices must have a temperature higher than the surroundings to transfer heat by convection, radiation, and conduction. The power supplies of electronics are not 100% efficient, so extra heat is produced that may be experimental to the function of the device.

Design Calculation

Theoretical equations are utilized to determine the parameters of the thermoelectric module, including the figure-of-merit, maximum temperature difference, voltage, current, and power output. Additionally, calculations for solar panel sizing and battery charging time are conducted to ensure optimal system performance.

TEC module calculation

Basic Model for TEC

The following theoretical equations (1-4) for a TEC are provided in many handbooks and papers [7-10]:

To simplify, define SM, RM and KM by equation (5-7):

SM = 2sN (5)

RM = 2ρN/G (6)

KM = 2NkG (7)

Then, equations (1, 2 and 4) can be expressed as equations (8-10):

The parameters s, ρ and k are fundamental physical properties of the TEC materials and SM, RM and KM are the physical characteristics of the TEC as a device. The figure-of-merit, Z, is directly related with the ability of a TEC to pump heat and is a criterion to evaluate the quality of the TEC [11]. All these parameters are necessary constants in calculations or simulations using the above equations. Unfortunately, none of these are generally listed in the manufacturer’s catalogue. What the manufacturers usually list are ΔTmax, Imax, Vmax, and Qmax at a specified hot side temperature Th.

Expressions for ΔTmax, Vmax, Imax and Qmax

• Inspection of equation (8), reveals that DT varies as the square of current I when Qc is zero, as shown by equation (11).
• Differentiating equation (11) with respect to I leads to equation (12): Setting equation (12) equal to zero and solving for I to maximize ΔT leads to equation (13)
• Equation (13) is the prerequisite to produce the maximum temperature difference ΔTmax, and the current is defined as the maximum current Imax.
• The voltage at this time is defined as the maximum voltage Vmax. Now, inserting the value of Imax from equation (13) into equation (11) results in equation (14) for ΔTmax
• Replacing ΔT and I with ΔTmax and Imax in equation (9), an expression for Vmax can be obtained, as shown by equation (15).
• Usually performance specifications for a TEC lists ΔTmax, Imax , Vmax at a specific hot side temperature Th. Replacing Tc with (Th– ΔTmax) in equations (13) and (14), equations (16) and equation (17) are obtained.

In addition, Qmax occurs also at a specific hot side temperature when I = Imax and ΔT =0C.

Method I to Calculate SM, KM and RM

• Although the three TEC physical characteristics parameters SM, RM and KM are unknown, as noted earlier, vendor datasheets usually give the four maximum parameters ΔTmax, Vmax, Imax and Qmax, and in addition there are four equations (15-18).
• Any three of the four equations can be used to solve and get expressions for SM, RM and KM. Method I in this article uses only three equations ΔTmax, Vmax and Imax, and leaves the fourth for Qmax alone. In this way, equations (19-22) are obtained from equations (10), (15-17) to determine Z, SM, KM , and RM.

Calculation of solar panel

Here is the formula of charging time of a lead acid battery.

Charging time of battery = Battery Ah / Charging Current

T = Ah / A

Where,

T = Time hrs.

Ah = Ampere Hour rating of battery

A = Current in Amperes

example:

Suppose for 120 Ah battery,

First of all, we will calculate charging current for 120 Ah batteries. As we know that charging current should be 10% of the Ah rating of battery.

Therefore,

Charging current for 120Ah Battery = 120 Ah x (10/100) = 12 Amperes.

But due to some losses, we may take 12-14 Amperes for batteries charging purpose instead of 12 Amp.

Battery Capacity Rating Calculator Formula and Equations

Suppose we took 7 Amp for charging purpose,

then,

Charging time for 120Ah battery = 120 / 7 = 17.14 Hrs.

But this was an ideal case…

Practically, it has been noted that 40% of losses occurs in case of battery charging.

Then 120 x (40 / 100) = 48 …..(120Ah x 40% of losses)

Therefore, 120 + 48 = 168 Ah ( 120 Ah + Losses)

Now Charging Time of battery = Ah / Charging Current

Putting the values;

168 / 13 = 12.92 or 13 Hrs ( in real case)

Therefore, an 120Ah battery would take 13 Hrs to fully charge in case of the required 13A charging current.

Selection of solar panel

Voltage at maximum power V =17.50V

Current at maximum power I=0.28A

We know the equation of power calculation,

Power: P= V x I

= 17.50 x 0.28

= 4.9 W

Power generated by solar panel= 5 watts Battery12V, 7Ah current

Power = V x I Power

= 12x7

= 84Wh

Time required charging the battery = 84/ 5

= 16.8 hrs.

Note-Time varies because of intensity of sun radiations at different days. Voltage = 12 V

Current = 1.5 Amp

We know the equation of the backup battery time of sprayer,

= (Power stored in battery / Power Consumed by motor (pump))

= 84 1.5×12

= 4.67hrs

Therefore the battery time spray = 4.67 hrs.

Components with specification:

1. TEC module : 12 V, 5 A , 90 w
2. Solar panel : 12 V , 10 A , 25 w
3. Heat sink : 4
4. Regulator IC : 12 V , 20 A
5. Filter : 12 V to 15 V
6. BLDC fan: 12 V
7. Rectifier: 12 V,10 A
8. Voltage regulator : 7812,12 V
9. ON/OFF switch: 12V,10 A
10. Temperature display: -52c to 200c

Size of the Solar refrigerator :

Height = 609.6mm

Width = 457.2mm

Temperature of the refrigerator:

Cooling of refrigerator = 10.12 c

Advanteges

• No moving parts.
• High reliability and durability.
• Relatively low cost and high effectiveness.
• Compact size and high effectiveness.
• Easy for maintenance.

Disadvantages

• It is not applicable during rainy season.

Conclusion

The integration of thermoelectric principles with solar energy presents a promising avenue for sustainable cooling and power generation solutions. By leveraging semiconductor technology and innovative design approaches, thermoelectric-based systems offer a viable alternative to traditional cooling methods, particularly in off-grid environments. Continued research and development in this field hold the potential to address energy challenges while mitigating environmental impact.

References

1. Horway J.B. (1961). "The Peltier Effect and Thermoelectric Transients". University of Louisville.
2. Jaspalsinh B. (2012). "A Design Method of Thermoelectric Cooler". International Journal of Mechanical Engineering (IJME), Vol. 5, No. 1.
3. Mayank Awasthi, K.V. Mali (2012). "Design and Development of Thermoelectric Refrigerator". International Journal of Mechanical Engineering and Robotics.
4. Dai Y.J., Wang R.Z., Ni L. (2003). "Experimental Investigation on a Thermoelectric Refrigerator Driven by Solar Cells". Renewable Energy, 28, 949-959.
5. Astrain D., Vian J.G. (2005). "Computational Model for Refrigerators Based on Peltier Effect Application". Applied Thermal Engineering, 25(13), 3149-3162.