Lecture 28
October 30, 2013
Stand Alone PV
San Luis Valley Solar Data (09/11/2010) Good Day [1]
3
San Luis Valley Solar Data (09/12/2010) Bad Day [1]
4
Intermittent Wind Generation
5
Battery
Battery Equivalent Circuits
Lead Acid Battery
Battery Charge Discharge
Household Loads
Household Loads.
Electronic Loads
Battery Types Energy Density.
NaS Batteries For Grid
6h at 1MW
• 1 Operating temperature 300 to 350o C
NaS Battery Characteristics
Picture NaS Battery
Present Value
Levelized Costs
Nickel Metal Hydride
Vanadium Redox Flow Battery
Picture VRB System
Present Value $/kw VRX
Levelized Costs
Zn Air Battery
Zinc-Air Battery Prototype
Zinc – Air Cell
Present Value
Levelized Costs
Li Ion Battery
Li Ion Battery
Types of Li Ion Cells
Big System
Smaller System
Home Li Ion
Present Value Li Ion
Levelized Costs Li Ion
Li Ion Charge, Discharge Curves
Internal Resistance Li Ion Battery
Lead Acid Batteries
1 MW Lead Acid Battery
Big System
Present Value $/kW and $/kWh
Lead Acid
Levelized Costs Lead Acid
Some Limits On Batteries
• 1. Depth of Discharge.
• A. Car Batteries limits to

25% Life 10yr
– At 50% cut life in half. Strengthen with Ca
• B. For solar cells need 50 to 80% This means thicker
electrodes bigger space between electrodes. Sb
• C. Over charging leads to H2O→ 2H2 +O2
• D. Capacity depends on rate of charging and
discharging.
• E. Temperature dependence lower capacity at low
temperatures
State of Charge
• 1. Internal resistance increases as the battery
is discharged or with state of charge
• 2. This makes it hard to calculate watt hours.
• 3. Change to ampere hours and P= Vx I
• 4. Specify in C= Ampere hour capacity
– C/20 means capacity for full discharge over 20hr.
Temperature Dependence of Lead
Acid Battery
Deep Cycle Lead Acid Batteries
Rates of Charge and Discharge
Change Capacity and Life
Series Parallel Connections
Battery Connections
Limiting Voltage for Current of
100 Amps
Hours of System Availability
Solar Cell to Battery Direct
Battery Charging
Typical Derating Chain
An Off Grid System
An Off Grid System
Diesel Backup Efficiency