Need for batteries for rooftop solar power plants
For infirm power sources such as solar, batteries are required to make the power source more firm and reliable. Thus, for uninterrupted power supply through rooftop solar, use of batteries is inevitable today.
Types of batteries used for rooftop solar power plants
In practice, the two main types of batteries used in rooftop solar power plants are deep cycle lead acid batteries and Li-ion batteries.
While the lead acid battery variety has been the conventional choice, use of Li-ion batteries is an emerging trend.
How much do different types of batteries cost?
Let us consider the costs of the two main types of batteries – deep cycle lead acid batteries and Li-ion batteries.
Based on international benchmarks, deep cycle lead acid batteries cost about $100 per kWh, and come for about 1000 cycles @ 50% depth of discharge. Thus, you are paying $100 for 500 kWh (1 kWh *1000 cycles*50%), or about 20 cents per kWh.
Li-ion batteries cost about $350 per kWh and have lifecycles of about 2000 @80% depth of discharge. Thus, you are paying $350 for 1600 kWh (1 kWh*2000*80%), or about 22 cents per kWh.
While the per kWh for both might be almost the same, however, the higher per kWh cost of Li-ion battery implies a higher capital expense.
How much will my cost of power increase if I use batteries?
The bigger picture however is that both options are pretty expensive when it comes to energy delivered! If you take the cost of rooftop solar power without batteries to be about 12-15 cents/kWh without batteries, adding batteries increases the cost per kWh by over 100%
What are the other aspects that determine the cost of batteries for rooftop solar power plants?
One practical aspect to be considered in order to minimize the cost of power from batteries is maintenance – which implies both storing the batteries in an appropriate environment and undertaking the recommended maintenance activities regularly.
The above costs are under circumstances when the batteries are maintained well. Poor maintenance of batteries could result in much lower number of cycles, further increasing the cost of the batteries per kWh.