Solar Builder

NOV-DEC 2018

Solar Builder focuses on the installation/construction of solar PV systems. We cover the latest PV technology (modules, mounting, inverters, storage, BOS) and equip installers/contractors with tips and tools to make informed purchasing decisions.

Issue link: http://digital.solarbuildermag.com/i/1047902

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SOLARBUILDERMAG.COM | 19 The reason Sol-Ark has so much peak power is it packs in twice as many com- ponents as its competitors. It is literally designed to survive a solar f lare or EMP attack, which was the goal for these U.S. vets at the outset. "We didn't just focus on the person who wants to save on an electric bill but focused on emergency responders and state government, but in an affordable manner," Brennan says. "To do this, we basically built a 20-kW inverter and throttled it down. We don't have heating issues because we are not taxing the system." Providing the most powerful, efficient inverter for on or off-grid solar + storage does come with some new school draw- backs, at least right now. For example, Sol-Ark does not meet California's Rule 21 criteria. "That has not been an issue because we just don't export power in California," Brennan says. "We use the solar during the day, batteries at night and grid as a backup." On-grid extras Sol-Ark comes ready to perform the typical on-grid capabilities like time of use and grid sell back but also has a few unique options: Limited home mode. CTs or current sensors are placed on the mains of the house, and instead of just full grid selling or only powering critical loads, limited home mode is an in-between option. The CTs sense when any other circuit not on the critical loads panel kicks on and ramps up the solar power as much as it needs to zero the meter if it can. "Maybe you don't have a net meter agreement to sell back power to the grid, but you can push power to your whole house as long as the grid is up," Brennan says. "If it's down, you can only run criti- cal circuits. We designed Sol-Ark 8K for seamless on-grid capability." A lot of people in rural areas take advantage of this because they either don't want to deal with the electric com- pany or have no incentive to deal with it, so they use that to push as much power as they can to the house. Smart loads. This is a programmable load that's not based on time but rather the batteries' state of charge or how much PV power is being produced. Brennan explains: "We can turn on A/C or the hot water heater at 100 percent battery and solar is producing 2,000 W during the 9 a.m. to 3 p.m. time range when I'm producing excess solar. And if the solar stops producing [or batteries get to 95 percent], they shut off automatical- ly. It's perfect for on-grid time of use and off grid for preserving battery life. Hot water heating takes about six pan- els of energy a day, and air conditioning can take about 12 panels a day, so if just those can be run from PV alone and without the batteries, that will extend the life of the batteries by at least 50 per- cent or more and probably reduce the battery bank size by 30 percent. The Sol- Ark system will also account for and adjust to the degradation of battery health over time. What's old is new again Another question Brennan asks: Why are solar + storage customers waiting for lithium prices to drop when they will be connecting to the grid anyway? Sol-Ark's goal is make an off-grid approach to solar + storage work on the grid without doubling the cost of a system. "We don't think customers need lithium if it's just sitting there for backup; it's a waste of money," he says. "If you are on the grid, then take advantage of it. You can go with lower cost AGM batteries that last 10-plus years. If you have the grid where you are, get AGM batteries and use them as backup or slightly used and don't neces- sarily deep cycle them. If you're totally off grid, then we recommend lithium or car- bon-based AGM that have four to five times the cycle life. You can minimize your usage of the grid, but do it to keep your battery bank at a reasonable cost/size. If you were to try going completely off grid with a traditional size home, the battery cost would make you cry." Chris Crowell is the managing editor of Solar Builder.

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