Grid-tied solar electric systems are a great way to save money using free power from the sun. However, most grid-tied solar arrays are designed to shut down when they lose grid connection, meaning, even if it is sunny, if the grid is out of power, you are too (They do this as part of UL-listing, because a live grid-tied inverter might accidentally backfeed and harm line workers).
The next generation of battery storage has arrived, giving solar customers clean, reliable, and efficient backup power to reduce their dependence on the power grid.
Why Install Clean Backup Power?
- Quiet, affordable backup power without the burning of fossil fuels
- Take advantage of self consumption – use your day’s solar harvest at night, reducing your dependence on the utility grid, and reliance on Net Energy Metering
- Reduce demand charges by using solar + storage to reduce your power needs during peak daylight hours
How Battery Backup + Solar Power Works
Whether it’s the Tesla PowerWall, cell phone, cordless drill power-pack or golf cart battery, the basic concept is the same: a charged battery stores electrical energy in chemical form for later use.
In most renewable energy applications, a special class of battery, deep cycle batteries, are required, as the constant discharge and recharge of the battery requires more durable construction (in contrast to your car’s battery, which is used for a short burst of energy before it is quickly re-charged by your alternator).
In addition to being able to survive the wear and tear of frequent use and deep cycles, a renewable energy battery will also have a number of other important performance characteristics that determines how well it works in a particular application. Among those are:
- Energy Capacity: Maximum electric usable energy (kWh) stored in a battery.
- Maximum Discharge and Charge rates: The peak power—usually given as maximum current—the battery can either provide or accept without damage.
- Depth of Discharge: What % of the battery’s capacity may be used before it needs to be recharged.
- Cycle Life: How many recharge cycles a battery can undergo before it reaches end of life.
- Calendar Life: How long, in time, a battery can be expected to last before it reaches end of life.
- Energy Density: How much energy is stored per unit of volume.
- Specific Energy: How much energy stored per unit of mass. Energy density and specific energy are related, but distinct. For example, a battery with the same energy capacity may be large and heavy (low energy density and low specific energy), large and light (low energy density but high specific energy), small and heavy (high energy density and low specific energy), or small and light (high energy density and high specific energy).
- Temperature Limitations: The acceptable operating temperature range of a battery. Some battery chemistries may not operate below freezing temperatures, or at very high temperatures, for example. Others generate significant heat either while charging or discharging and thus may need an active thermal management system to keep them from overheating.
- Self Discharge Rates: The rate at which a battery loses charge while not producing energy.
There is no one single battery which optimizes all these characteristics, and in fact even within a particular battery chemistry (Lithium Ion or Lead Acid, for example), battery designers constantly have to make tradeoffs between different characteristics; for example sacrificing maximum discharge rate to increase overall capacity, or trading off cycle life against calendar life. Or trading any of the above against cost. Clearly there is no such thing as ‘the best battery’, there is only ‘the best battery for a particular application.’
We currently offer a number of options for battery storage depending on the design goals of the customer. Here are a few:
ReVision Energy is now a Tesla Powerwall Certified Installer, which means we now offer a customized solar-plus-battery solution that enables you to access the free, abundant power of the sun and reduces your reliance on fossil fuels.
With Powerwall you can store solar energy generated during the day for use any time. During the day, the sun shines on your solar panels, charging your battery. At night, your home draws electricity from your battery, powering your home with clean, sustainable energy 24/7.
Installing Powerwall with ReVision Energy is easy. We take care of everything from system design, to permitting, installation, financing, and ongoing customer service.
Powerwall consists of a 14 kWh lithium-ion battery pack, liquid thermal control system, an integrated inverter and software that intelligently dispatches electricity when it’s needed most. The unit mounts seamlessly on a wall or on the ground, indoors or outdoors, and is connected to the grid to export excess energy, maximizing your opportunity for economic benefit.
Powerwall can provide a number of benefits:
- Increasing self-consumption of solar power generation –Powerwall can store surplus solar energy during daylight hours and use that energy later when the
sun is not shining.
- Load shifting – Powerwall can charge during low rate periods when demand for electricity is lower and discharge during more expensive rate periods when
electricity demand is higher.
- Back-up power – Assures power in the event of a grid outage.
Learn more: https://www.tesla.com/powerwall
Pika Energy: Maine-Made Clean Backup Power
To have a grid-tied array provide power during an outage, you need additional equipment to supplement the grid-tied solar inverter. One option is the Maine-made Pika Energy Island, a system that combines an islanding inverter, solar optimizers, and a battery bank to turn your home into a microgrid.
The Pika Energy Island allows you to bank your solar power when it’s sunny and use it in the evening, giving you more control over your own power and an insurance policy against future changes in utility rates. Under most conditions, the solar provides grid-tied power, powering your home when the sun is out, backfeeding power to the grid when there is excess and taking power from the grid when more power is needed. When the grid goes down, a set of critical loads – such as a well pump, boiler, or refrigerator – is kept running by the battery and solar, as well as generator if you have one. The Pika Energy Island is designed to pair with Pika’s Harbor and Coral smart batteries.
Technically speaking, the Pika Energy Island is a “DC-coupled” clean energy backup solution, meaning, it uses high-voltage DC electronics to communicate between the solar inverter, solar optimizers, and battery bank. Pika Energy’s capabilities are quite sophisticated however in a retrofit situation (adding on to solar customer that already has an inverter) there is some added cost as the existing solar PV inverter would need to be replaced.
Why Pika Energy Island?
- Long warranty life on all components (10 yrs extendable to 20 for inverter, and 25 years on PV Link) backed up by local support from a Maine-based company
- Cost-competitive with other grid-tied solar components
- U.S.-made inverter for grid-tied solar, ready for the seamless addition of next generation smart batteries
Sonnen – a complete backup system
Another equipment option for integrating clean energy power backup is the Sonnen, a complete energy storage solution consisting of electronics, lithium ion batteries, and an enclosure for the entire system. The battery system is “AC-coupled,” meaning, it connects to the AC-grid side of a home and thus can integrate with any existing grid-tied solar photovoltaic array without further modification.
The Sonnen is a product of Germany, where “self-consumption” of solar energy is more common and the level of solar penetration on the grid is significantly higher than it is in the United States. The system is available in a variety of storage capacities and configurations, allowing for extensibility and expansion.
- Continuous output up to 8,000 watts.
- Up to 16 kilowatt-hours of battery storage.
- Guaranteed lifetime of 10,000 cycles or 10 years.
Future-proof Solar Investments
ReVision Energy has been following the developments in battery technologies for years. In the early days, the only kind of solar energy systems were off-grid (battery-only) systems, and then with the advent of grid-tied inverters the obvious benefits of tying up to the grid became clear. Now, technology has come full-circle, and a grid-tied solar customer can enjoy the benefits of being tied to the grid, with the resilience and independence of having battery support.
We carry a number of battery solutions to accommodate the variety of equipment we have installed for 5,000+ customers in four states. For older grid-tied PV systems, something like the Sonnenbatterie offers the simplest interconnection and a clean, convenient package. For new systems, who want to support a Maine-based company and set up their system for battery backup either now or in the future, the Pika Energy Island is an excellent choice. Customers who want to maximize the financial savings of their solar investment can start with a straight grid-tied array for maximum savings and lowest upfront cost, then invest later in a battery backup solution when they are ready. While there is great battery technology on the market already, we expect that this segment of solar technology will rapidly improve over the next 5-10 years.
Learn More About Battery Backup & Energy Storage
ReVision Energy strives to stay at the top of all trends in renewable energy, and solar backup power is one of the hottest topics right now. Our engineers worked with our editorial team extensively for an in-depth, three part series on the current state of backup storage and its implications for the homeowner, and the grid, writ large: