How Residential Solar Coupled with Energy Storage Add to Grid Stability

Credit: iStock/Alessandro2802

There are now more than one million individual solar installations nationwide, with the residential solar market remaining strong, according to the Solar Energy Industries Association. The US installed 1,665 megawatts (MW) of solar PV in the first quarter of 2016 to reach 29.3 gigawatts (GW) of total installed capacity, enough to power 5.7 million American homes.

The next frontier is combining renewable energy such as solar with energy storage, notes Ellen Howe, vice president of corporate development and marketing for JLM Energy. Industry experts concur; pointing out that the technology exists to support that. Challenges facing the residential sector focus on state policy changes, utility buy-in, system financing, proper equipment choice, and finding qualified installers.

Tim Poor, chief commercial officer for Aquion Energy, notes a “definite move” toward a more distributed approach to generating electricity from the traditional utility model of large, centralized power generation stations moving energy through the distribution network of lines and transformers to the end-user.

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“Now that solar costs are lower and there’s a rising interest in sustainability and renewable energy, people can generate a good portion of their own energy themselves and need to rely far less on getting it from the utility or from a centralized source,” he adds.

California’s first state-approved solar-wind-battery storage system has been in place for nearly three years at the 50-acre residential property of John Poswall and Pam Tomlinson-Poswall in Lincoln Hills, CA, where their home is surrounded by themed gardens. Their grid-independent system consists of four Zefr microwind turbines, a 24-kW solar array from Solarz, and the JLM Energy Energizr 100 battery storage system.

Two factors leading the couple to adopt the system was a commitment to be environmentally friendly and Pacific Gas & Electric (PG&E) bills of $1,700 a month. Poswall—an attorney and an author—says those factors, in conjunction with a federal credit, made the economic case for the installation. The couple, which has net metering, gets a net zero bill from PG&E.

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Poswall says the system offers advantages to the utility company in that his home’s system is boosting power and with an additional need for power, the company doesn’t need to build more infrastructure. The system mitigates complexities of the water-energy nexus by taking the irrigation system off of the house and establishing a separate system for the gardens that runs off of solar.

Poswall—who says he’s not mechanically or electrically inclined—says he finds the system to be user-friendly, enabling him and his wife to set the system to automatically operate certain lights in the home or hit a circuit to utilize stored energy.

The Arizona Public Service (APS) Electric Company is partnering with the Arizona Solar Deployment Alliance to install new technology suites into 75 APS customer homes in Phoenix, notes Steven Gotfried, APS spokesperson.

“All of the homes are going to get solar panels, a smart thermostat, and a home energy management system,” notes Gotfried. “Some will receive a combination of battery storage, multi stage variable speed HVACs, and load controllers. This is going to give us a better understanding of how advanced consumer-oriented technologies interact with each other.”

The pilot program will include JLM Energy products. It’s geared to save money for residents and the utility during the more expensive evening peak demand time, notes Howe. JLM Energy devices used in the pilot include a phone app to control thermostats, remotely turn off appliances, and offer push alerts to notify the customer when to avoid using energy-draining appliances as well as offering batteries that automatically charge any excess energy from the solar panels.

“They are going to have the energy storage systems in some of the homes and in others, they’ll have the solar with the energy management systems in our Measurz software,” says Howe.

Until now, Hannah Solar had focused on the commercial sector. “The residential solar game has changed,” points out Pete Marte, CEO, noting the growing interest in solar has made storage more appealing to the residential sector.

Case in point: Georgia’s Solar Power Free-Market Financing Act, which establishes that solar energy procurement agreements (SEPAs), also known as power purchase agreements (PPAs), are a lawful way to finance the construction and operation of a solar electric generation system. It enables a solar company to finance the construction of solar panels for a home, business, or institution in Georgia and be repaid for the system through payment by the property owner for the electricity produced by the solar system.

Another example: the California Energy Commission’s New Solar Homes Partnership (NSHP), part of the California Solar Initiative, which provides financial incentives and other support to home builders to encourage the construction of new, energy-efficient solar homes.

“That’s telling people if you want to build a new house, you need solar,” says Sara Kissing, vice president and chief operating officer of Concept by US/POWERSTATION 247. “That makes it important.” Changes in solar technology may encourage more adoption, notes Kissing, adding the “panels are getting smaller and produce more energy.”

The three major factors to consider beyond the cost of a solar plus storage system are location, expectation for backup power, and electricity rate tariff, notes Neil Maguire, CEO for Adara Power. “Installers need to offer customers a choice of indoor or outdoor, floor- or wall-mounted, and provide a clear picture of what the system looks like once installed,” he says. “Contrary to popular belief, the Tesla Powerwall rendering which shows the device floating on the wall is not real life—there are inverters, disconnects, and other gear required.”

The second factor is the amount of house loads one can put on a critical load panel to run when the grid goes down. Adara systems are designed to allow everything to be put in the house on the backup panel except for large air conditioning units due to the system delivering 7.0 kW of peak power, says Maguire.

“Finally, the electricity rate tariff must be understood and selected to take advantage of time-of-use rate structures,” he notes. “The solar plus storage solutions allow you to shift PV output into the evening but you may not get paid for that if the rate structure does not support it.”

Copyright 2016 Concept by US corporation
Concept by US’ POWERSTATION 247

Installers need to be trained in these considerations and advise their customers so that every install results in complete satisfaction, Maguire points out, adding that the company has certified more than 100 installers through its full-day training class.

Since solar plus storage is a new concept in the US, one of the biggest challenges in its adaptation in the residential sector is educating homeowners on how the system works.

Kissing says when Concept by US/POWERSTATION 247 conducted market research for its system, the first question a solar installer would get from those having a system installed on their roof is whether they could use the energy on their own. “Of course, the solar installer always has to say no and then they need to educate the end-consumer because most of the end-consumers don’t know that even though they have a solar PV system on their roof, they don’t actually use the energy in their house,” points out Kissing.

“These end-consumers need to be educated that there is an inverter, that they just feed that into the grid and actually the energy they use when they turn the lights on in the house is energy they get from their grid provider,” she adds.

Those who do have battery storage installed also need to know that not all technology is the same. Some companies, such as Concept by US, offer all of the energy storage components in one containment solution. Others also offer the solar panels as a turnkey solution. Otherwise, components of a solar plus energy storage system also are offered separately by many companies.

In some cases when the grid goes down, the battery voltage will dictate how much energy storage can be used, says Kissing. “You can actually use the energy that the battery has in your house, but only for small applications—you cannot run your entire house on a battery with low energy storage capacities,” says Kissing, adding that most batteries on the market have 48 volts of power in contrast to the 96 volts needed to do so.

“If you want to have a bigger system where you can actually use a lot of energy to run your house as a backup or emergency, then your entire garage wall is full of components,” she adds. “You have solar PVs on the roof, you need to have an inverter—sometimes you need two—you need MPP trackers, battery chargers, battery management systems, a battery, and other components. You can buy all of these components from a lot of manufacturers and piecemeal them together.”

That’s where the residential sector loses interest, Kissing contends, adding there are separate installation times and charges, maintenance agreements, permitting, and warranties for all of the components. Additionally, systems connecting to the grid need to be UL-certified, notes Kissing, adding that there are products out there that are not and cannot pass permitting procedures.

In its market research, Concept by US also found end-users don’t want an “ugly” collage of inverters, batteries, and other components in their garage, notes Kissing, adding that the POWERSTATION 247 system is designed to be “a very aesthetically pleasing design in a great shape with chrome corners because we do know how important the garage is to the American family.”

Safety is another concern in residential solar plus storage applications where children may be present in the area where the infrastructure is installed, notes Kissing of the benefit of the POWERSTATION 247 system being housed in an enclosure.

Financing systems is one of the prime concerns of residential end-users and there are now more options. Kissing points out that most of the larger solar installation companies offer leasing and financing options.

Maguire says that most of those who have purchased an Adara system have done so through cash or PACE financing—Property Assessed Clean Energy programs. According to the US Department of Energy, PACE programs allow local governments, state governments, or other inter-jurisdictional authorities, when authorized by state law, to fund the upfront cost of energy improvements on commercial and residential properties, which are paid back over time by the property owners.

Maguire says Adara is now working with a retail energy provider to offer on-bill financing for solar plus storage. “This is a great way to lower the upfront cost,” he notes. The ROI depends on geography, says Howe, adding that she’s seeing ROIs of 48 months on commercial projects.

Geography also drives energy reliability. “In some places, people may prefer to see a backup system,” she says. “Where I live in Colorado, if you’re up in the mountains and around well water, a backup system would maybe make more sense than having grid synergy when you have that affordable power.

“The nice part about the grid synergistic system is we see it working for the most part in conjunction with the grid and obviously the utility companies have invested millions of dollars over the years building out the infrastructure, so the grid synergistic is really the best of both worlds.”

Options abound whether a residential customer seeks to take a piecemeal or an integrated approach to solar plus energy storage. JLM Energy ties solar panels to batteries built to the company’s specifications and connected to the company’s energy management software. “We take a year’s worth of a customer’s utility bills—our software has all of the tariffs in the United States plugged into it—and run their bill, looking at their habits,” notes Howe.

“The software will then make recommendations on what they can do to make small changes that can have impact on their bills. It could be something like running a pool pump at night and not in the middle of the afternoon.”

Partner company solar installer PetersenDean is selling JLM Energy software with its component box to solar customers, notes Howe.

The company offers two products for the residential market: Energizr 100, a grid-independent backup system to keep critical loads running during a power outage. Energizr 100 creates a local microgrid so that grid-tied renewable energy inverters continue to generate electricity through a black-out. When the grid is available, the renewable resources are used to charge the system batteries and excess renewable energy is used for net metering.

When the grid is unavailable or if load demands exceed a pre-specified level, Energizr 100 uses the stored energy from the batteries to power local electrical loads and simultaneously ensure the renewable energy is used to recharge the batteries. In the event the grid is unavailable and the batteries are fully charged, the renewables are controlled to prevent the batteries from overcharging.

The AC loads can be powered by a 48-volt battery, 120-/240-volt renewable energy, 120-/240-volt grid, and 120-/240-volt generator. The system has an output power of 4.4 kW and has cloud-based interface with JLM Energy’s Measurz software.

Energizr 200 is a grid-synergistic system that works with solar power and the utility grid so power can be automatically used, stored, or sent back to the grid. In addition to energy storage, Energizr 200 is designed to work in harmony with smart thermostats and smart appliances.

JLM’s cloud-based software platform, Measurz, is designed to analyze user habits to produce efficiency recommendations helping homeowners meet budget goals. The mobile app enables remote control of appliances such as HVAC systems and smart thermostats.

The driving technology behind Energizr is JLM Energy’s Symmetrical DC Regulation. The system uses a 400-volt battery and bypasses a charge controller to connect the battery directly to solar. From batteries, the system goes directly to the inverter, which bypasses a boost controller. With a fraction of the energy going through the battery, the system is designed to achieve up to 87% overall efficiency.

The Adara Energy Storage System is an 8.6 kWh Lithium-ion energy storage system for residential and small scale commercial buildings. Using the company’s system controller, the Adara Energy Storage System is integrated with an inverter or charger and can be deployed in parallel for higher power and energy needs.

The Adara Energy Storage System contains an array of Lithium-ion batteries with a battery management system to ensure safe, reliable, long-lasting control of the Lithium-ion cells. Adara Power utilizes Lithium-ion Nickel Manganese Cobalt (NMC) batteries.

Adara Power controls the discharge and charge current depending on the cell temperatures and other conditions for longevity. The company uses the battery type for its longevity, energy density, its ability to be recycled or discarded in landfills, and because it requires no maintenance of venting of gases.

The system controller is designed to manage the inverter or charger interface for control of charge and has redundant protection mechanisms to prevent over voltage, over current, under voltage, and over temperature conditions. A cellular gateway to a secure cloud-based repository is designed for remote monitoring, updates, and control. The system is housed in an indoor/outdoor UL-rated enclosure. The system has a 10-year operational life.

POWERSTATION 247 is designed to store solar energy to be used at any time: day, night, and during power outages for grid stability, compensating power peaks and maximizing return on renewable energy investments. It is a fully integrated scalable system of 5 kW, 10 kW, or 15 kW with a battery storage capacity of 17.28 kWh. The free-standing “plug-and-play” cabinet encompasses up to three hybrid inverters, solar MPP-trackers, charge controller and Lithium-ion batteries, field wiring terminals, and disconnect switches.

Hannah Solar, headquartered in Atlanta, GA, is a full-service, North American Board of Certified Energy Practitioners (NABCEP)-certified solar integrator offering engineering, products, installation, as well as service.

Among the services provided: solar design, procurement, construction, and service, and energy storage systems.

The company is comprised of a NABCEP-certified solar photovoltaic installer, licensed professional engineers, master electricians, service technicians, project management professionals, designers, and installers.

The company has teamed up with Sonnenbatterie—a German-based developer, designer, and manufacturer of integrated energy storage systems—to address the growing demand for residential solar coupled with an energy storage solution.

Sonnenbatterie has provided energy storage systems throughout Europe. The company established US headquarters in Los Angeles and established a research and development facility in Georgia. Sonnenbatterie partners with local companies to provide its integrated energy storage system designed to utilize intelligent energy management software to monitor the energy flow—both electricity production and consumption—anytime and anywhere.

Features include remote energy management, peak-shaving, full-home backup, smart-home integration, aggregation of storage networks, and grid-service features.

The information also is designed to help end-users understand their electricity storage through a system touchscreen, enabling them to control, measure, and view a graphical real-time display of all system information. Homeowners also have access to an app for their computers and smart devices to monitor their energy use by the hour.

Another battery option for the energy storage market comes from Aquion Energy, which manufactures the Aspen battery, based on Aqueous Hybrid Ion saltwater electrolyte chemistry.

Tim Poor, of Aquion, says the Aspen battery is designed as a “completely non-toxic, environmentally benign battery that’s very safe and maintenance-free.” It is certified by the independent third-party cradle-to-cradle organization.

Poor points out that the Aspen battery does not possess chemical properties that could lead to thermal runaway, a condition that has occurred with some Lithium-ion batteries. Poor says the company has seen an acceleration of the use of the Aspen batteries in a residential setting, partly in response to concerns over fire.

The batteries come in 48-volt and 24-volt versions and can be connected in parallel, Poor explains. “The advantage of being in parallel is if you have a problem with one battery, it can go offline and the other batteries remain online and the system continues to function,” he adds. “In a series configuration like you would do with lead-acid, if you lose one cell out of the string, the whole string goes down.”

Round trip efficiency—the ratio of energy put in to energy retrieved from storage—is in the mid-to-high 80% range, says Poor. The battery has a 10-year operational life with 3,000 cycles at 100% depth of discharge under normal use, he adds.

It is offered as part of an overall storage system through a network of dealers and installers not only for residential, but commercial and industrial market segments as well. Aquion provides technical support and training for dealers and distributors.

“These are oftentimes the same companies that install solar panels on the roof,” says Poor, adding there’s an overlap in skill sets required to install both, given the power electronics required to convert the voltages to the AC voltage in the home. “You have to go in and out of the battery, so all batteries need a bi-directional inverter,” says Poor.

Kissing says it’s important that residential customers use certified installers. Certified solar installers know codes, know about weather cycles and at what angle the rooftop solar PV systems should be installed as to avoid potential problems.

“Each state has different regulations,” she notes. “Some contractors can also be solar installers and in some states, they need to get an additional license to install solar. They should never trust a solar company that does not have engineers in-house that are educated and certified.

“Everybody in California—especially in the building departments—are taking a look at the construction underneath to make sure it is safe to get the permits for it,” says Kissing. “The US permitting system is good—nobody can hook up the system just like that and not get in trouble for it.”

As with many system manufacturers, JLM has trained in-house system installers and also works with dealers that have installed solar for years. An electrician needs to install the system, Howe points out, adding “it’s not for a layman to install.”

The regulatory support has not caught up with the technology and demand, notes Poor. On one hand, there is a 30% tax credit through the Solar Investment Tax Credit (ITC) “which if you install batteries with that, you also can apply that credit toward the batteries as well.”

However, each state’s public utility commission needs to take action to make permitting and availability of installing storage in a home easier.

“In some places they fight it and make it difficult to get permits, so it slows down the process,” says Poor. “It really does vary state by state.” He cites the example of Hawaii, which he points out has the highest electricity costs in North America. “Solar is playing a big role in their energy mix, but they also need batteries and after fighting the installation of grid-connected batteries for a long time, they started a self-consumption program,” says Poor.

“When you have solar panels on the roof during the day, generally the loads in your home are not as high as they are in the evening, so you are generating a surplus of energy,” he adds. “You’re making more than needed during the day time when the sun is shining, so you can export that energy back onto the grid.

“Or you can say you created that energy: it’s your equipment, it’s your solar panels and you can save that energy in a battery and use it later throughout the day when you need it. That’s called self-consumption.”

It’s done quite a bit in Germany where the driving factor is less about economics and more about the consumer wanting to have a degree of independence from the grid, says Poor, adding that with the proper solar panels and batteries, a homeowner derive up to 75% autonomy from the grid.

Feed-in tariffs are another influencing factor. “If you have surplus energy that you are creating during the day, you can export that back onto the grid,” he says. “In a lot of places in the US, it’s called net metering and they just spin the meter backwards so you get full credit for every kilowatt hour that you produce and put onto the grid against your basic electricity bill.”

Poor points out that there is an efficiency loss in all batteries, “so why incur that efficiency loss if you can get 100% credit by spinning your meter backwards?”

Some utilities don’t favor that because “they’re finding that as more customers zero out and reduce their energy bill, the burden of paying for the cost of the distribution system the utility owns—all of the poles, wires, and electrical equipment out there—gets distributed across a smaller revenue base and it becomes difficult to maintain consistent energy prices.”

Residential storage is taking hold in Europe, Australia, and Japan, notes Poor, adding that net metering is common there. It’s starting to change in the US, he says, pointing out that Hawaii has limited net metering and the practice is on the radar in Arizona and New Mexico.

The fundamental argument among US utility commissions is that the allocation of their distribution system’s fixed costs are not balancing out with those using renewables plus storage paying less to have the same access to the grid as others who pay more, Poor points out.

“There needs to be a policy in place to support distributed renewable energy that includes economic incentives and utilities embracing a distributed model versus fighting it,” contends Poor.

Trends indicate that this is starting to happen, as people install energy storage systems in their homes for backup in the wake of weather events that have knocked power out from hours to weeks, he adds.

Howe says policy changes in some states are driving the adoption of the solar plus storage technology. Salt River Project in Arizona has added demand charges, Howe points out. “If you’re generating solar during the day and net metering during the day but then you come home and your high energy hours are between 5 p.m. and 8 p.m., you’re getting these demand charges because there is no way to save that solar power to use at that time you really need it,” says Howe.

Howe says JLM Energy looks at utilities as suppliers and partners “because we see them as a force multiplier for adoption,” she notes. “When you look at the states with very aggressive distributed energy benchmarks, how are the utilities going to get there? They’re not going to get there just by adopting utility-scale solar or wind. When they can look at turning entire neighborhoods into microgrids, it’s going to make it better for them because they’re going to be able to bring more distributed energy resources online,” says Howe.

“I know sometimes consumers get very frustrated with [utilities]. Part of our business model is to tell them by becoming a little more proactive and managing their energy, they have more choice and control over the equation and eventually can potentially get to that zero bill.”

Kissing points out, “We have population growth like crazy. We’re getting more people who will be connected to the grid. The grids get more and more destabilized by more houses being connected. We need some options for the conscious energy user.” BE_bug_web

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