The market for renewable energy is in turmoil right now, mainly because of lower utility costs, a desire for energy independence, incentivized solar installations, and low-cost batteries. Homeowners are now trending towards storing energy from solar cells rather than selling it back to the grid. However, that requires selecting storage components wisely.
Although 2016 was the cutoff year for the current solar energy tax incentives, there has been a successful bid to the Congress to extend the incentives up to 2020. As a result, the solar industry finds itself rejuvenated and this is having a reflective effect on the battery-based energy storage systems as well.
This has created a massive surge for ESS or energy storage systems in general, with particular emphasis on RES or renewable energy storage systems. Designers of inverters and power conversion architectures now have enormous opportunities, especially those designing for home applications. For instance, Tesla has announced the Powerwall, a 10-kWh storage system suitable for homes, businesses, and utilities.
Designers and manufacturers are looking at advanced storage options such as ultra-capacitors and battery chemistry such as solid electrolytes, magnesium-ion, lithium sulfur, and next-generation flow and metal-air. The next-generation technologies for energy storage are expected to increase from near zero in 2015, to above $9 billion by 2030. Overall, the demand for batteries will increase from 66 GWh in 2014 to over 225 GWh in 2023
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Traditionally, people assumed that any excess power generated from solar panels and not used by the homeowner would be sold back to the utility. However, they are beginning to realize that saving the extra energy in batteries can help in the evenings, when the energy consumption is the highest and so are the utility rates. In the evenings, when there is no sun, the home can be less reliant on the grid, and be more self-sufficient if it relies on the backup batteries to supply electricity.
So far, people had to buy all parts separately and put them together for a solar system. This included the battery, inverter and metering. However, all this involved multiple voltage conversions leading to unnecessary losses and overall lower efficiency.
Now, all that is changing. You can opt for a fully integrated system. This includes the PV monitoring, the inverter, and the DC/DC conversion to charge the battery. Metering now is highly advanced, with wireless technologies such as ZigBee, providing either computerized or application-based monitoring of the entire system.
However, that does not mean it simplifies optimizing the PV conversion. One still needs MPPT or maximum power point tracking to make sure of capturing the varying PV energy and transferring it to the battery with the minimum of power losses, regardless of the strength of the sun. For instance, this involves using a capacitor for stabilizing the PV voltage and dropping it sufficiently, ensuring the charging voltage matches the battery chemistry.
Although efficiency, cost, and ease of use are all factors critical to the system level, safety is still the highest priority. The emphasis is on isolation including both digital isolators and opt couplers to meet the IEC 62109-1 standards.
