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Jun 27 2016
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Sonnen Battery Systems

Three Reasons Why GE Is Betting on Sonnen Battery Systems

By Uncategorized No Comments

At the beginning of June, German battery system manufacturer Sonnen Inc. announced it had received a significant investment from GE Ventures. According to the company, GE’s investment arm shelled out a “double-digit million Euro” amount for a minority stake.

Until then, it had been mostly Tesla grabbing the headlines introducing its Powerwall a year ago, the first of which are now reaching customers in the US. And competition in the emerging residential storage market becomes tougher as more opportunities are looming.

According to GTM Research’s most recent US Energy Storage Monitor, distributed battery storage will surpass grid-scale storage in the US by 2020. GTM Research forecasts that America’s energy storage market is going to grow 28 times bigger than it is today, reaching 1.6 gigawatts capacity within four years. Roughly half of that will be behind-the-meter in the form of residential or small commercial battery-plus-solar applications.

So why is GE betting on a relatively small German company that just started offering its battery system in the US? The answer boils down to experience, opportunity, and upside.

Experience

Sonnen was one of the first movers in the German market as soon as the question arose how to best store energy from residential photovoltaic (PV) systems after the German government introduced a generous feed-in tariff in 2000. Sonnen understood that batteries will eventually become commodities. Instead of developing better lithium-ion technologies, the company focused on software and system integration. As a result, it was able to offer a competitive battery system for homeowners early while many established players in the German market had to play catch-up.

To date, Sonnen claims to have installed more than 10,000 units, mostly in Germany, while aggressively expanding in markets like Australia, the UK, and the US. Tesla had to learn the hard way what this kind of experience is worth when it was faced with customer complaints about its first units delivered in Germany making too much noise. At least in one instance, the Powerwall was replaced with a Sonnen system. Talk about bad publicity.

Opportunity

There are no two ways about it: Putting a battery in your basement to store energy from your PV solar system is not economical at this point. The money you have to spend for each kilowatt-hour to be put into the battery and taken out later hovers between 40¢ and 80¢ per kilowatt-hour. That’s way more expensive than electricity from the grid, even if you apply a 30 percent federal tax credit, which you might be eligible for if you charge the battery largely with self-generated solar power. Check this video to find more about kilowatt-hour.

The only way to make the numbers work is to have the battery perform different services for the grid, like load shifting or shaving the peak off of the solar production curve, opening up various revenue streams. This is also known as revenue stacking. In its report “The Economics of Battery Energy Storage”, the Rocky Mountain Institute identified 13 revenue streams that residential battery systems will be able to tap in the future.

While there are technological and regulatory hurdles to overcome, once the revenue streams become available, Sonnen system owners will be better equipped to milk them than others. The reason is Sonnen uses batteries with different chemistry than most other companies. It allows for 10,000 charge and discharge cycles over the lifetime of the battery. Most of the competitors offer no more than 4,000 cycles.

Right now, it is hard to make use of this feature because a typical residential solar PV system fully cycles a battery only once a day or 3,650 times over ten years. At this rate, it would take more than 27 years to exhaust the cycle life of a Sonnen system—likely way longer than the calendar life of the battery. But once revenue stacking is available and, for example, a utility uses the Sonnen battery to stabilize its grid while cycling the battery several times a day, the Sonnen product would have a significant advantage.

Upside

This is where it gets interesting. If you think Sonnen’s endgame is to become a battery system provider for residential and small commercial applications, you are thinking too small. Imagine instead that Sonnen becomes its own utility, aggregating all the battery systems into one big virtual storage system that quickly and seamlessly offers a variety of services for its customers and grid operators. Now we are talking about storage as a service, and those companies offering the best software solution for a large amount of distributed storage systems have a competitive advantage.

In Germany, Sonnen already started what it calls “SonnenCommunity.” It is basically a trading platform that enables system owners to share their stored, surplus PV energy via the grid. So far, Sonnen only guarantees participants lower energy costs than they would pay to a regular utility, but no grid-balancing services for utilities. But it is an important first step in that direction.

When introducing “SonnenCommunity”, Sonnen’s German Managing Director Philip Schröder told Energy Storage News: “If storage is [currently] one thing, it is hardware. [And it becomes] a commodity at some point. But we truly believe, along with GE, that community concept will make this more attractive for the customer but also would allow us to monetize many of the features that we have, such as weather data, forecasting.”

If GE’s investment enables Sonnen to quickly move forward in that direction, its competitors have a lot more catching up to do.

Jun 20 2016
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should you wash your solar panels?

To Wash or Not to Wash?

By Solar Panel Maintenance : Everything You Need to Know No Comments

The economics of solar panel cleaning

We all know what a fresh cleaning does for windows. The world outside suddenly seems brighter, more vibrant, because sunlight is no longer partially absorbed by a thin film of dirt. The same happens with solar panels. The longer they go without cleaning, the less light hits the solar cells and ultimately gets converted into electricity.

Homeowners with solar panels have to ask themselves two questions. How much energy do I lose from soiling? And is it worth it to clean the panels?

The short answer on panel washing is: no, it’s not worth it.

Soiling losses

“You definitely wouldn’t get your money back after hiring someone to wash your rooftop panels,” says Jan Kleissl, a professor of mechanical and aerospace engineering at UC San Diego and the principal investigator on a study about soiling on solar panels. But it is worth looking at the details of Kleissl’s study and how he reached his conclusion.

The dirt itself does not hurt solar panels. It comes down to economics. To find out if the cleaning cost is justified, we have to calculate the potential losses from soiling. That is more complicated than it may sound because there are a lot of contributing factors.

Solar panels with an aluminum frame, for example, stay dirtier after rainfall than frameless panels. If the panels are tilted five degrees or more, chances are that rain, wind, and snow do a good enough job to keep production up.

In a dry climate or an area with heavy air pollution, soiling losses can add up. Excessive bird droppings can be a problem, too. Even though they are relatively small, they can continuously shade parts of the panel, creating destructive hot spots and panel degradation.

Kleissl and his collaborators looked at 186 commercial and residential solar systems from San Francisco to the Mexican border. The panels hadn’t seen rain or any type of cleaning for 145 days during a summer drought. Efficiency losses amounted to 7.4 percent. That might sound like a lot. Keep reading, and you’ll see it’s really not.

Not many researchers have tackled cleaning for residential systems, but those who have came to similar conclusions. Heinrich Häberlin, professor at the Berner Fachhochschule für Technik und Architektur, Switzerland, saw almost twice as much energy loss due to soiling, but it was not enough to pay for professional cleaning either.

Pay a lot, save a little

Companies in the US charge a fixed fee for cleaning solar panel arrays or they bill by the panel. Either way, the total cost is usually about $120 to $140 for the average residential system.

The amount of solar energy you produce and your cost of buying electricity from the grid vary depending on where you live. In New Orleans, Louisiana, an average-sized, 5 kW system will produce about 550 kWh a month. (Use the National Renewable Energy Laboratory’s PVWatts calculator to look up the energy production for a solar panel system where you live.)

Since energy losses due to soiling range from 7.5 to 15 percent, a New Orleans solar home stands to lose about 40 to 80 kWh of energy per month. At the price people pay for electricity there, 9₵ per kWh, this would set you back $3.75 to $7.50 a month.

Add up the cost of soiling losses for a full year. That’s $45 to $90. You can see that a solar panel washer would make money providing annual cleanings, but you would not.

How about DIY panel cleaning?

You might ask yourself why not take out the garden hose and make it rain on your modules all by yourself? That’s a bad idea for several reasons.

Drinking water contains minerals that will leave a white film on the glass. In a worst-case scenario, a little critter has, unbeknownst to you, damaged one of the wires under the modules. Do you want to risk electrocution?

So you just climb on the roof and use a brush, you think. Well, consider the danger of falling off and breaking every bone in your body. Also consider that solar panel glass is not ordinary glass, it has a microstructure to catch as much sunlight as possible that can be damaged if you use the wrong brush.

If you really have to clean your panels yourself, use a soft cloth and a gentle soap solution. Make sure you don’t step on the panels though. They won’t break, but the cells could get damaged. Professionals work with deionized water and special brushes with very long handles.

In the end, it all might come down to this: When thinking about maintenance, solar panel systems are like cars. You might get away with no maintenance at all for a long time and save some money, or you might have things checked regularly by a professional.

Solar panels, inverters, and wires should be inspected by an expert once a year. So why not find a provider that maintains your system and washes panels as needed, maybe every three to five years?

Besides all economic calculations, clean modules certainly look better—which is, of course, priceless.