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10ECEN2060
Economics of battery storage
Example: the deep dischargebatteries in our lab
Retail cost: $150
Assumptions:50% depth of discharge
20 hour uniform discharge
Average voltage 12.4 V
1000 cycles
Energy of each dischargecycle:
I = (Cp/t)1/k = (63/20)1/1.15 = 2.7A
ED = (2.7A)(12.4V)(20hrs) = 0.67 kWh
Battery capital cost per kWh:
($150)/[(0.67 kWh)(1000 cycles)] = $0.22/kWh
Typically $0.10/kWh for large optimized installations
Battery costs more than the energy it stores!
11ECEN2060
Backup gas generation
Cost of gasoline
Estimated 5 kWh/gallon, $3/gal
$0.60/kWh
Capital cost
$0.50 to $1.00 per Watt
Adds another $0.05 to $0.10 per Watt if amortized over 19 years
12ECEN2060
The value of grid energy
Power supplied by the utility is available
Estimated cost $0.10/kWh in Colorado
Available on demand, very high reliability
To reproduce this in a standalone PV system:
1. Must generate the power with PV; est. cost $0.21/kWh
2. Must store in batteries, est $0.10 to $0.41 / kWh
3. May additionally need other backup power sources, with additionalcosts but substantially improves reliability
Utility bill has a charge for kWh consumed only
Reliability is worth at least as much per kWh as theenergy itself, but is not included in current pricingschemes approved by PUC
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