The document outlines various solar energy storage systems, including thermal, electrical, chemical, mechanical, and electromagnetic storage. It details methods such as sensible and latent heat storage, electrical storage using capacitors and batteries, and mechanical methods like pumped hydroelectric and flywheel storage. Additionally, it highlights criteria for effective energy storage materials and the operational principles behind each storage technique.

1. SOLAR ENERGY STORAGE
By
Prof. Ashish Bandewar

2. Unit 3 Solar Energy Storage system:-
1. Thermal energy storage
a. Sensible heat – i)Water Storage ii) Packed bed storage
b. Latent heat.
2. Electrical storage
a. Capacitor b. Inductor c. Battery
3. Chemical Storage
a. Chemical b. Thermochemical
4. Mechanical
a. Pumped hydro-electric b. Compressed air c. Flywheel
5. Electromagnetic Storage

3. Sensible heat storage:
Where the addition or removal of heat results in a
change in temperature.
Latent heat storage: (phase change energy storage)
Energy absorbed or released during a change in
phase, without a change in temperature (isothermal).

4. Sensible Storage - Water Storage
• Water is the ideal material which store useable heat.
• It is low in cost and has a high specific heat.
• Convenient when water is used also as the mass and heat
transfer medium in the solar collector and in the load heat
exchanger.

5. Sensible storage - Packed Bed Storage
• It is a large insulated container filled with loosely packed
rocks.
• Circulation of air through the void of the packed is done
• Which results in natural or forced convection between the
air and the rocks.

6. Few points for Bed Storage :-
• Rock is more easily contained than water
• Rock acts as its own heat exchanger
• For storage more than 1000C it can be used, as
water cannot be used.
• Heat transfer coefficient between air and solid is
high
• Low cost storage
• Conductivity of bed is depend on air flow/air
velocity
• Can be used in solar houses or hot air collector
system.

7. Latent heat Storage
• Heat is stored in material when it melts and
extracted from the material when it freezes.
• Material that undergo phase change in suitable
temp range is useful in energy storage if following
criteria satisfied for phase change :-
• Must be accompanied by high latent heat effect
• Must be reversible without degradation
• Must occur with limited super cooling
• Material must be available in large quantities
• Material must be harmless (non toxic, non
inflammable)
• Must have high thermal conductivity in both phase

8. Electric Storage
• Capacitors could store large amount of electrical
energy, Energy stored is , Hcap = ½ x VεE2
• V is Volume of dielectric
• ε is constant
• E is Electric field strength
• Electric energy storable in dielectric (material-mica)
is limited
• Capacitive storage is economical for times no
longer than 12 hours
• Capacitors store electrical energy at high voltage
and low current.

9. • Inductor storage is at low voltage and high current
• Hind= ½ VµHm
2
• µ is permeability of material
• Hm is magnetic flux density
• For Hind to be large both µ and Hm should be large
• High magnetic fields are required
• Reverse operation in case of inductor can discharge
stored energy

10. • Battery is combination of individual cells
• Cell is the combination of material and electrolyte
where energy is stored electrochemically
• This energy is regained as electrical energy
• Secondary batteries are important for solar
application (Re-Chargeable batteries)
• Exa – lead-acid , nickel-cadmium, iron-air, nickel-
hydrogen, sodium-suplhur etc
• Anode and cathode immersed in electrolyte

11. • Chemical storage in the form of fuel
• To store in battery by photochemical reaction
brought about by solar radiation
• This battery is charged photochemically and
discharged electrically whenever needed
• Thermochemical energy storage are suitable for
medium or high temp applications
• For storage, reversible reactions appear to be
attractive A+B AB
• Forward reaction takes place with absorption of
heat from solar energy ( Heat is stored )
• Reverse reaction caused to liberate heat.

12. Mechanical energy storage
1. Pumped hydroelectric storage
• In hydroelectric power plants, once the water has
been run downhill to turn the turbines it flows out to
sea; pumped hydro lets us pump that water back up
hill, to re-use for power generation again and again.

13. 2. Compressed air energy storage
• A compressor/wind turbine is used to store
compressed air in pressurized storage tank.
• Later this compressed air is used to drive turbine
which will generate electricity when there is demand

14. 3. Flywheel storage
• Flywheel is driven by electric motor during off peak
hours stores mechanical energy
• The rotation of flywheel can be used to operate a
generator to produce electricity when required

15. Electromagnetic energy storage/ Superconducting
magnetic energy storage (SMES)
• SMES material suddenly loose all resistance to the
flow of electricity when cooled below very low
temp
• If maintained below this can carry strong electric
currents
• Superconducting materials like niobium titanium
alloy at temp – 263oC
• Electromagnetic field produced by an electric
current flowing through wire coil can store energy.