New Zealand Engineering Firm offers Home Energy Storage

May 14, 2015 by Jeff Shepard

Power Concepts NZ Ltd. (PCNZL) announces the development of a complete home energy storage system with fully integrated bi-directional inverter, battery storage and grid interface, delivering 5kW. The system is compact, light-weight and highly efficient. PCNZL, an independent research and development company specializing in innovative power electronics, has designed this system especially for home and small commercial installations. The IP of the PCNZL Home Energy Storage system is available for purchase or licensing.

Key features of the system include: A bi-directional grid-tied inverter with efficiency above 95% all the way up to full load and a no load power less than 10 watts. Safe 24v LiFePO4 battery modules designed for easy installation and service. A sophisticated battery management system which actively balances cells and enables full use the energy contained in each cell. A grid interface and data monitoring which delivers grid synchronization data for the inverter, provides statistics on household generation and use, and manages load. Light-weight modular design and flexible housing allowing easy installation in difficult-to-access locations.

“Patent protection has been granted for key innovative features. A prototype has been built and core functionality verified. The system has been designed to maximize ease of manufacturing and PCNZL can assist in putting the system into production if required,” observed PCNZL’s CEO, Chris Fotherby.

“In the past year the interest in home energy storage systems has accelerated beyond most people's expectations. PCNZL found itself in the fortunate position of having many of the components for a home energy storage system already developed and has been able to quickly develop the remaining parts to make a complete home energy storage system. Our system is highly efficient, compact, lightweight and easy to install, making it ideal for residential settings and small commercial premises. Unlike most existing energy storage systems, the individual components - inverter, BMS etc .- have been designed from scratch to work with each other, forming a fully integrated system. This contrasts with the recently announced Tesla Powerwall home battery which needs to be connected to a third party inverter,” Fotherby continued.

“The PCNZL inverter is rated at 5kW and works with safe 24V battery modules. Until now it has not been possible to achieve high efficiencies from a high power inverter designed for such a low supply voltage. Our inverter, however, has an efficiency that peaks at over 97% and remains above 95% all the way up to full load. The inverter no-load consumption is less than 10W, minimizing the load that the inverter itself places on the batteries overnight and at other times when the house load is low. The inverter responds rapidly to changes in the house load so that the grid current flowing into or out of the house can be accurately controlled at all times.

“Our 24V battery modules contain a sophisticated BMS that not only balances the charge in the individual cells, but can also actively transfer charge between cells while the battery is charging or discharging in order to make full use of all the energy contained in each cell. Modules can be plugged into and unplugged from the system while it is running, and each module can periodically disconnect itself from the system and measure its own capacity. These features ensure that the system is easy to maintain and that the expected battery service life is actually achieved.

“Our grid interface measures the grid voltage and current at the house's grid connection and contains a relay to disconnect the house from the grid in the event of a blackout, letting the inverter power the essential circuits in the house. The grid interface has a high speed fiber-optic link to the inverter which allows the two devices to be located completely independently and minimizes the changes required to the house wiring.

“The PCNZL system is ‘ac coupled’ so it can be retro-fitted to an existing solar installation with no changes to the existing system. It also makes our system compatible with the large number of installations now using micro-inverters which convert power directly to ac at each panel.

“By aggregating control of our inverters it would be possible to provide electricity utilities with a number of grid support functions, such as frequency/voltage regulation, grid support in the event of transmission line faults or a generator trip, and active harmonic reduction. This opens additional possible revenue streams to both households and the aggregating company.

“As a technology development company specializing in power electronics, we know it takes a long time to develop an energy storage system similar to ours where all the components are fully-integrated and designed to work together. Acquiring the IP for this system would allow companies wishing to participate in this lucrative market to jump start their product development,” concluded Fotherby.