harvesting energy by using waste heat 1

Harvesting Energy from waste heatusing pyro electric

• 36.2% of the energy contained in raw energy sources is useful.

• 57.8% is wasted mainly in the form of heat. • The efficiency in transport sector is only 20-30

%.

Energy Harvesting

• Wind• Water• Solar• Temperature• Vibration

Energy Harvesting Mechanisms

• Piezoelectric energy harvesting• Electrostatic energy harvesting• Thermoelectric energy harvesting• Photonic energy harvesting • Pyro electric energy harvesting

PiezoelectricPiezoelectricity is the ability of certain materials to produce a voltage when subjected to mechanical stress.

Piezoelectric materials also show the opposite effect, where application of an electrical field creates mechanical stress (size modification) in the crystal.

The Piezoelectric Effect

• the ability of certain materials to generate an electric charge in response to applied mechanical stress or vice versa.

PIEZOELECTRIC EFFECT

Sound waves striking a PZ material produce an electrical signal

Can be used to detect sound (and echoes)!

REVERSE PIEZOELECTRIC EFFECT

Applying an electrical signal causes the PZ element to vibrate

Produces a sound wave

Application of Piezoelectric

• POWER GENERATING SIDEWALK• GYMS AND WORKPLACES• POWER GENERATING BOOTS OR SHOES

Pyro electric

Pyro electric energy conversion offers a novel and direct way to convert heat into electricity

Pyro electric effect

• The displacement of the atoms from their equilibrium positions upon heating and cooling results is a result of the pyro electric effect.

• Changes in temperature cause proportional changes in the electric displacement

Pyroelectricity

• the ability of certain materials to generate a temporary voltage when they are heated or cooled.

Pyro electric material

• The most important component in pyroelectric energy conversion is the pyroelectric material.

Performance of pyroelectric materials

• Large pyroelectric coefficient in order to generate a large pyroelectric current

• Large spontaneous polarization so that more charges can be stored on the material’s surface to produce a large pyroelectric current.

• Large dielectric strength to enable large applied electric field during the Olsen cycle without breakdown.

• Small leakage current caused by electrical conduction through the material that reduces the energy density.

• Short discharge time of the surface charges in order to minimize cycle period and to maximize power density.

• Small heat capacity to enable rapid isoelectric heating and cooling processes of the Olsen cycle to maximize power density.

Harvesting of waste heat using pyro electric material

Conculsion

• dealing with small-power energy harvesting from heat, it can be achieved using both thermoelectric and pyroelectric effects

• Temperature gradients are necessary, which is just the main difficulty of thermoelectric energy harvesting. In case of pyroelectric energy harvesting, a time varying temperature is necessary.

• or instance, using a limited temperature gradient due to the limited heat exchange, a maximum efficiency of 1.7% of Carnot efficiency can be expected using a thermoelectric module. On the contrary, a pyroelectric device may reach an efficiency up to 50% of Carnot efficiency