What is so exciting about the Tesla Energy announcement is not just the low $3,000 US price point for a 7 kWh wall-mount lithium-ion energy storage unit (and $3,500 for 10 kWh pack) but the fact that this enables so many other energy related solutions.
The Tesla home energy battery pack has a 10-year warranty plus an optional extra 10 year extended warranty and is designed to be mounted on a wall. This "Powerwall" includes thermal management and a bi-directional DC inverter. This is a system that is really designed for home owners with solar on the roof and an electric vehicle in the garage. But bundling such affordable energy storage with DC fast charging stations also makes great sense in commercial applications. For EV drivers this is very exciting because often the problem with getting DC fast charging stations deployed is costs of installing and powering a charger.
When the solar energy collected at a retail shopping location from a rooftop or from a solar canopy in the parking lot can be stored in a battery pack, this means that demand charges can be avoided during peak load times. What are demand charges, you ask? Demand charges are a surcharge an electricity customer pays when their consumption exceeds a threshold. Say that threshold is 35 kWh. Once your electricity demand goes over 35 kWh, you pay a premium. That can really add up if you have electric vehicle drivers using your DC fast charger during peak load times.
With the addition of more affordable energy storage for commercial applications, the business case for DC fast charging can improve significantly. The solar energy collected by the solar panels gets stored in the battery pack and used to charge up the EV without AC to DC conversion loss. Further operating cost savings are also realized by not buying spot priced electricity during peak times. Regardless of whether the DC fast charger juice is sourced directly from solar or not, the energy storage pack can deliver savings. Over the long term a lower cost per EV charge can be realized because the pack can be topped up from free solar energy or it can be replenished from the grid when the rates are lowest.
An example of such a creative tech convergence project is the Benicia, California’s grid-tied, solar-integrated EV (electric vehicle) fast charging station which is optimized by battery energy storage. This first ever project of its kind and it was completed in June 2014 using a 40 kWh energy storage system and 175 kW of solar bundled with a dual port DC fast charging station.
This is the sort of technology convergence that once scaled in production can really help accelerate the adoption of electric vehicles. Surely more of these comprehensive solutions are needed and will inevitably become more mainstream with the recent reduction in energy storage, photovoltaics and DC fast charging station hardware.