The post-net metering solar industry looms on the horizon, some day, for every state, but in Hawaii it is a reality, which makes it guinea pig. At SPI, Poncho’s Solar and Tabuchi Electric Co. will be presenting the results of their collaboration with J.O.B. Technologies (Aiea, Hawaii), detailing the results of a year-long case study on the post-NEM residential self-supply (non-export to the grid) market in Hawaii.
Analysis of the field data details various types of optimization and integration required to successfully integrate solar PV with electrical battery storage, solar hot water thermal storage, and summertime solar A/C cold thermal storage. By integrating solar PV + battery storage and adjusting the time-of-use (TOU) of the top 4 major household appliances and using Tabuchi Electric’s HEMS (home energy management system), nearly all household energy demands can be met without the need to purchase from the grid.
“In the post-NEM customer self-supply world, the economics of solar PV and saving electricity is quite different than with NEM,” noted John Borland, President of J.O.B. Technologies. “For NEM programs, the amount of cost savings and return on investment is determined by generating the maximum amount of solar PV energy possible and selling back to the grid. The key to the fastest return on investment in the post-NEM world is through achieving a monthly utility bill with Grid-Buy as close to zero as possible. By working with Poncho’s Solar and Tabuchi Electric over the past 15 months, we successfully reduced the monthly daily average Grid-Buy electricity by 96.0% through modifications and improvements to the solar thermal storage system, the inverter, the Home Energy Management System (HEMS), and the hardware and software control system. The average daily Grid-Buy energy in April 2017 was reduced to ~2.7kWh/day from 48.7kWh/day in April 2016. Additionally, 12 days were at Zero Grid-Buy, running on 100% Renewable Energy.”
“Mid 2016, we installed a 7 kW rooftop solar PV system with 27 c-Si modules with the Tabuchi Electric solar inverter and battery storage system,” stated Corpuz Poncho, President of Poncho’s Solar. “Since electrical water heaters in Hawaii can account for as much as 40 percent of the monthly household electrical bill, integrating the solar PV system with solar thermal is essential. To eliminate Grid-Buy needs on water heating, we customized the hot water tank into a thermal storage for Battery Optimized Discharge Hot Thermal Storage.”
The Tabuchi Electric 5.5kW solar PV inverter with 10kWh Lithium-ion storage battery provides multiple flexible modes of operation for users in both NEM-enabled markets, such as California and Arizona, and post-NEM markets like Hawaii.
“Our system monitoring software allows for optimization of energy usage by major household appliances to reduce Grid-Buy, with dynamic battery charging and discharging to maximize savings based on TOU rates,” noted Harumi McClure, President/COO of Tabuchi Electric Co. “The results from this study resulted in improvements to both the software and hardware of our hybrid inverter system. This enabled the Stand-Alone Operation of 21 days with ≤4kWh/day Grid-Buy, and of which 12 days were Zero Grid-Buy. Improvements were made to our new EIBS16GU2 system increasing the critical load panel to 3.3kW and doubling the capacity of batteries to 19.78kWh, and we expect our customers to see further financial savings on electricity and better return on their investment.”
— Solar Builder magazine