Photovoltaic Systems Engineeringprofsite.um.ac.ir/~karimpor/pv/lec7_Storage.pdf · 2013. 4. 9. ·...

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Ali Karimpour Apr 2013

Photovoltaic Systems Engineering

Ali KarimpourAssistant Professor

Ferdowsi University of Mashhad

Reference for this lecture:Photovoltaic Systems Engineering Third Edition CRCRoger Messenger, Jerry Ventre

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Lecture 7

Energy Storage

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Energy Storage

The Lead-Acid Storage Battery

The Nickel Cadmium Storage Battery

Other Battery Systems

Batteries

Hydrogen Storage

The Fuel Cell

Potential energy stored, Compressed air, flywheels, Superconducting magnets,…….

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Chemistry of the Lead-Acid CellCharging process

Discharging process

Over charging Gassing

Deep discharging is not ok since cell performance may be affected.

Sometimes it is ok.

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Lead-acid battery is still the most common for relatively economical storage of electrical energy.

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Properties of the Lead-Acid Storage Battery

Charging efficiency is around 95%, Discharging efficiency is around 95%, Overall efficiency is around 90%

High charging rate or discharging rate leads to lower efficiency.

The amount of energy in a battery is commonly measured in Ah and shown by C.

Charging rate or discharging rate is shown by C/x.

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Higher discharge rate less charge being available as energy to a load.

Higher charge rate it takes more energy to fully charged.

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Effects of discharge rates and temperature on the relative amount of charge that a battery can deliver.

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Properties of the Lead-Acid Storage BatteryShallow discharge

Deep discharge

Small amount of calcium combined with the lead to import greater strength to the otherwise pure lead.

Thinner plates with greater area higher starting currentShould not be discharged to less than 75% of their capacity.

Less lead less expensive.

Use antimony to strengthen the lead.

Can be discharged to 20% of their capacity.

Thicker plates with less area lower level current.

Marine application, electric forklifts and PV system use.

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Properties of the Lead-Acid Storage BatteryDeep of discharge affects the number of operating cycles.

Trade off between:- More batteries, shallower discharge and extend the overall lift or- Fewer batteries with dipper discharge rate and lower initial cost.

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The temperature at which the electrodes of batteries will freeze is very important

Where maintenance is inconvenient, maintenance-free, sealed deep-cycle batteries exist, but at least double the price.

Valve regulated to recombine gases.

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An advantage of removable caps is that it is possible to measure specific gravity.

Specific gravity is the most accurate measure of the state of the charge of a battery.

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Chemistry of the Nickel Cadmium Storage Battery

Nickel hydroxide for the anode plates.

Cadmium oxide for the cathode plates.

Potassium hydroxide for the electrolyte.

Charged cell is 1.29 V.

Specific gravity of the electrolyte changes very little during battery operation.

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Properties of the Nickel Cadmium SystemMore robust than lead acid

They can survive freezing and high temperature.

They can fully discharged.

Less affected by overcharging.

Can be discharge at the rates up to C over a wide range of temperature range, while still providing more than 90% of its capacity

Very low internal resistance.

Elimination of charge controller.

Unreasonable to expect it last twice as long as its lead-acid counterpart. (25 year good condition to 8 years in bad ….)

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Properties of the Nickel Cadmium SystemDisadvantages

Memory effect.

Memory effect is predominant in sealed batteries and is not a problem in some other types.

It is hard to determine state of charge.

Toxicity of the cadmium.

Higher price compare to lead-acid.

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Electrolysis of Water (H2O)

http://www.gm.com/company/gmability/edu_k-12/9-12/fc_energy/make_your_own_hydrogen_results.html

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Hydrogen Storage

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Hydrogen Economy Schematic

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Hydrogen Energy Cycle

http://en.wikipedia.org/wiki/Hydrogen_economy

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Hydrogen Storage

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Hydrogen Storage

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Hydrogen Storage

It can be used as a engine fuel to power a vehicle.

Hydrogen + air water + heat (No pollution but small NOx)

Hydrogen + air + Fuel cell water + heat + electricity

High energy density

2 ft3 gasoline is around 614 Kwh

5*60 Ah 12 V batteries is around: 3.5 Kwh

2 ft3 of gaseous hydrogen is around: 27.5 Kwh

2 ft3 of liquid hydrogen is around: 140 Kwh

Storage and transport of the gas is an engineering challenges.

Fuel_cell.FLV

fuel_cell2.FLV

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The Fuel Cell

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How does a Hydrogen Car Work ?

In a hydrogen car, its primary source of power is from one of two ways:

Combustion chamber

Fuel Cell

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Hydrogen-Powered Autos

fuel_cell_car_4.FLV

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Hydrogen-Powered Aircraft

Hydrogen powered passenger aircraft with cryogenic tanks along spine of fuselage. Hydrogen fuel requires about 4 times the volume of standard jet fuel (kerosene).

http://planetforlife.com/h2/h2vehicle.html

But less weight 200 ton 70 tone

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Hydrogen Future

http://www.unido-ichet.org/ICHET-transition.php

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Hydrogen Future

Photovoltaic Systems Engineeringprofsite.um.ac.ir/~karimpor/pv/lec7_Storage.pdf · 2013. 4. 9. ·...

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