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Energy Independence and Uninterrupted Power A solar photovoltaic (PV) system with battery storage enables you to get the most out of your panels and produce self-sustaining electricity separate from the grid. When blackouts happen in your neighborhood, you don’t want to be left in the dark. Battery storage supplies your critical loads and empowers you toward energy independence. When you pair your solar system with battery storage, you’ll have continuous power to your home, even when the grid goes out.
SOLAR + BATTERY SCENARIO: Somewhere in your exploration of solar energy, you’ve probably have heard quite a bit about batteries. You wonder, are batteries necessary for solar to work? In the most basic sense, yes. A solar system must have a battery to be useful. However, the product you might be thinking of—a consumer home battery, like Tesla Powerwall—is often an optional feature that comes with additional benefits. To gain a deeper understanding, of how batteries and solar energy systems work together, let’s start by considering a simple, abstract solar system. In this system, you have a single solar panel. This panel receives light from the sun during the day. This is when it produces a voltage that can be used to power something like a lightbulb. When a cloud passes between the sun and the solar panel, the voltage might drop slightly. At night, the panel stops producing voltage altogether. This means that the lightbulb only comes on during the day, when there is sufficient sunlight to produce a voltage. However, it’s likely that you’ll want to use your lightbulb when the sun isn’t shining as well. Here's where a battery comes in. A solar battery stores the electricity produced by our solar panel. The power stored by the battery allows you to use it when the sun has set. While there are systems that require actual batteries on-site—specifically, off-grid systems with no utility connection—the vast majority of systems can operate without them. In a grid-tied system, the electrical utility acts as the battery. When the solar panels are producing excess electricity, that excess flows onto the grid where it is “stored”. When the panels are not producing electricity, you can still use electricity by drawing from the “grid battery”. So, if the vast majority of solar systems don’t need batteries on-site to function, what’s all the fuss about consumer batteries like Tesla Powerwall?
TIME-OF-USE STRUCTURES One of the biggest advantages comes when your utility provides a time-of-use rate structure. Most utilities have a diverse set of production facilities: coal, natural gas, wind, solar, and perhaps some hydroelectric. Some of these production techniques are more expensive than others, and the cheapest ones can’t be relied upon at all hours of the day.
Therefore, it’s easy to spin up expensive forms of production, like natural gas ‘peakers’, to accommodate voracious electricity demand ‘peaks’. Utility company don’t like doing this because it costs them a pretty penny. In areas where peak energy demand is a real problem, utility companies often disincentivize the use of electricity during these hours by offering a time-of-use rate structure. Under this structure, a customer pays less for electricity when it’s cheap to produce, and they pay more during the typical hours of peak demand. Here’s where battery storage can be a big advantage. By storing electricity in batteries when it’s cheap and using that stored energy when grid electricity is expensive, a household or business can significantly reduce its utility bill. After a while the batteries will pay themselves off, and the utility customer continues to take advantage of the cheaper rate.
RESILIENCE If you don’t live in an area with a time-of-use rate structure, you can still receive the key benefit of added resilience provided by a battery storage system. By resilience, we mean the ability of your home or business to function normally when the power is out. If you experience frequent outages, you likely have a good idea of how disruptive they can be.
When the grid is down, batteries can keep lights, refrigeration, computers, and other critical electrical systems functioning seamlessly when you most need them. In addition to solving routine service lapses, batteries are increasingly being thought of as a central feature of disaster preparedness plans. When an earthquake, tropical storm, or other large event disrupts utility operations in an entire region for an extended period of time, homes and public facilities equipped with batteries can be vital lifelines for the community. Installing solar alongside batteries is popular when outages longer than a couple of hours are expected, because the batteries can be continually recharged with energy generated from the sun. Contrary to popular belief, this is not achieved with solar alone. Electrical utilities require that solar systems turn off when grid service goes down, because any voltage on the line could pose a hazard to utility workers. However, if your solar system is tied to battery backup, you can disconnect from the grid entirely and operate as an electrical ‘island’. This functionality provided by solar plus batteries affords you maximum resilience and independence from the grid.
Batteries have their limits, of course. Running many high energy appliances—for example, an air conditioner, a clothes dryer, and a hot tub—will probably deplete a fully charged Tesla Powerwall sooner than you’d like. While it’s possible to add additional battery capacity, doing so can be cost prohibitive. More often than not, a battery backup system doesn’t power all of the circuits in your home. Instead, it stores power in a separate ‘emergency loads’ electrical panel. This emergency panel is just like the main electrical panel in your home, with breakers that control different parts of your electrical system. The circuits on this panel receive electricity from the grid under normal operating conditions, and from the battery system during an outage. When designing a battery storage system for your home, Sunlight Solar will work with you to choose which circuits to add onto your emergency loads panel. Careful calculations are required to make sure that your expected energy consumption using those circuits is matched by the capabilities of your battery system. What you choose to backup will depend on your personal priorities, but generally includes more essential items like lights, kitchen appliances, and outlets used to power computers and cell phones. If you have questions about how batteries can help make your home more energy efficient, and save you money, be sure to get in touch with us!