Goods News for my DIY ESS - Energy Storage Sytem : Another step reached with 500 EUR of Savings logged by the online portal as of this weekend :)
Since I started logging usage + generation data with the EnergyHive hub in June 2014, it says 502 EUR has been saved on Imported Electricity
But my DIY ESS has been running with Solar Panels since July 9, 2013, and the additional savings figure for the first period should be close to 11 x 20 EUR/month = 220 EUR
So the total amount of Energy Saved on my Utility bill is today around 720 EUR ! after 2 years and 9 mobths of service
And since the price per kWh of Electricity is always going up, the savings will continue to increase faster with time !
Even if I do not care about ROI really, I can now say that 1/4 of the money spent to build my DIY ESS (3,000 EUR) has been payed back in Energy Bill Savings (720 EUR) over the 2 years and 9 months : 720 / 3,000 = 24%
Using cheaper Electricity rates to Charge at night (TOU) during winter, and Solar Surplus during the day, my Energy Storage System automatically tries to match the Power Consumption at home, in conjonction with Solar Generation when available, to have a Net Usage (Home Usage - Generated Power) close to 0W : No Import & No Export = Self Consumption of Solar Production
EnergyHive Free Online Portal enables instructive and user friendly graphs for real time and historical data display
Energy Generation Chart : Imported vs Generated Energy
Another real time way of checking what's going on is through a Logitech Broadcaster Webcam displaying Live on Ustream 2 Wattson units : one with Generation (Solar + ESS), the other with Net Usage (Usage - Generation) : http://www.ustream.tv/channel/chris75sf
I started working on Energy Storage 4 years ago ...
As most of you probably already know, I started looking into Energy Storage several years ago, actually back in 2011 if I remember well ... It all started with my will to install Solar on the roof of our building to start generating free electricity for our home, I actually had this idea years before; Of course nobody in our condo was interested in this and mentioning it a an owners annual meeting was useless (but I tried once at least), so I decided to do it myself anyways, discretely, and living on the last story would make it easier.
I quickly found out that the only solar panels that I could install without touching/damaging the classic Parisian zinc roof were the Uni-Solar PVLs and ordered some from the US through eBay, in 2 lengths, studying the roof layout using Google Maps ... I eventually found a local contractor who would install them and provide the inverter
Since I did not have the approval, I could not resell the excess electricity to the French utility - what all people were doing at that time -, so any Surplus Power would be wasted during the day... That's when I started thinking about Energy Storage
At the same time, I was selling my used 2004 Prius, which I retrofitted with an Enginer PHEV Battery system in 2009, and removed all this from the trunk of course: I had 4kWh worth of Lithium-ion LiFePO4 cells I could use right there ! and I always thought that Li-ion battery would be perfect for this use
Switching ON a Charger to use the Surplus of Power generated during the day was obvious to me, but the opposite, push Power back into our grid at night (or when need during the day), was not more difficult: problem solved after looking at a Green Power Science video on small low voltage inverters !
Previously, in may 2011, after several months looking for the "best" Energy Monitor, I purchased a DIY Kyoto / Energeno Wattson unit, and installed it: I could now see in real time - for the first time - our home Power Usage, that was a mandatory starting point for the rest
Now that I had all the ingredients to make an energy Storage System, I had to build one, because what you could find on the market at that time was just very expensive and/or huge
I experimented with the Battery cells I had in my bedroom for several weeks, using a LiFePO4 charger, Grid Tie Inverter found on eBay (video)
A big question/problem to solve was "How do I safely Charge my LiFePO4 Battery Pack ?" and I found the answer watching my first ever EVtv weekly video on Youtube
Key info you need is: Usage, Generation, and Net Usage (calculated by subtracting Usage - Generation):
- If Positive, your Solar install does not produce enough Power to cover you home loads, and you are using Power from the Grid => You have to use Energy from your ESS
- If Negative, your Solar install produces more Power than your home is using, you are "wasting" Power flowing back to the Grid => You have to Store it into your ESS to re-use it later on
That's rather simple isn't it ? :)
Click the picture to see the details on this conversion to Enphase Micro Inverter
All these years, I have been following the development of the upcoming main stream Energy Storage Systems, and they are finally coming ! Enphase announced their AC Battery first a year ago already, then Tesla announced their Powerwall - "The Missing Piece" - , a lot in advance for both of them, before anybody could actually order one
Also both companies are targeting specific countries where it makes sense Economically : Australia and Germany will be served first because of factors including the Price of Electricity, Feed In Tarif - FIT - rates, Grid Parity, the development of Solar.
So it will take some time I think to have either one of them installed at my place, but patience, Residential Energy Storage for the Masses is coming for good this time ! :)
Enphase is the leader in Micro Inverters with 4 generations of them since July 2014 and the launch of the M250, producing now up to 250W per solar panel; The advantage is the maximum harvesting of solar power - because it is done at the panel level, whereas a classic solar panel string will be affected by one panel being shaded for example - all inverters produce 240V AC Power which is then routed to the home consumer unit, making their installation is easy. On top of that it comes with great panel level online monitoring solution - called Enlighten - using their Envoy gateway which gathers all the data using PLC and sends it to the cloud.
For Energy Storage, Enphase - now Enphase Energy - continues with this all AC strategy and proposes a small unit called the AC Battery: It contains 1.2kWh of LiFePO4 Battery cells, and a new S275 - S for Storage - bi-directional inverter (or inverter/charger) which is key: Plugged into the same Engage AC cable it will charge and discharge the Battery pack, using AC only, based on the data - communicated by PLC again - of a new gateway called Envoy-S - S for Storage too - which comes with in a metered version: It know how much Power your home is using, and since it already knows the total panel generation, it can easily deduct the amount that should be stored into the AC Battery, or used from it.
The limitation of this is the maximum Power Output: 270W per AC Battery ... But you can add as many as you want to be able to shave home loads properly... But it will cost you 990 USD per unit (wholesale price), so it is scalable, but can become expensive if you need to overcome big Usage peak at home (A/C ON, dryer, EV charging, at the same time for example)
Tesla Motors created Tesla Energy to sell their PowerWall and PowerPack, residential and commercial/utility scale Energy Storage Systems
Tesla had been testing wall mounted residential Backup storage systems in California for the last 2 years at Solar City customers willing to participate in this test program; The pack was already using the Model S battery pack technology and the PowerWall and PowerPack still do. That was interesting but, it was only purely Backup, meaning you store Energy from solar into you system, and release/use it only in case of a Power Outage ...
On April 30th, 2015 Tesla Energy launched the Powerwall (and Powerpack) but I thought Elon Musk did not give much technical information on it, appart from the price of 3500 USD which is actually pretty good (I will focus on the 7kWh Daily Cycling version of the Powerwall because I am not interested in the Backup only version)
Elon Musk said (during the Q1 2015 Earnings Call at 9:15) that "the response has been overwhelming / crazy", and that they are basically "Sold out until mid 2016 when the GigaFactory will be able to take over" with 38,000 Powerwall pre-ordered in the first week !
Since this event, I have been trying to find answers to my questions and some elements came from this video few days after the event (Video Q1 2015 Earnings Call et 35:40 JB Straubel goes into details on the PowerWall (for the first time), on Tesla Motor Club forums or in Inverters manufacturers videos and websites:
Fronius
Until I recently got the most important piece of information (the one I missed all the way since the launch): There is of course a communication going on between the Powerwall and the Solar Inverter, and the protocol used is the well known RS-485
As seen above in my DIY ESS past experience, you need to command the inverter and charger to produce Power and Store Energy from and to the Battery Pack of the ESS, in real time
I got this information from studying the websites and videos of both Solar Edge and Fronius, the two only Inverter manufacturers compatible (for now) with the Powerwall
From Tesla Energy website diagram and JB Straubel explanation, we know that the Powerwall is wired in parallel with the Solar array (, and Inverter), so it is getting the Generated Power Directly from it, at something like 400V, and will be using its DC-DC converter to boost it to an Higher Voltage to be able to Charge the Battery Pack if the input voltage (coming from the solar array) is too low
Writing this post, I realize that Tesla Energy recently updated their diagram to give more information about the Inverter and now says that it is a specific one: "The inverter converts direct current electricity from solar panels, the grid and Powerwall into the alternating current used by your home’s lights, appliances and devices. All Powerwall installations require a compatible inverter. To maximize solar consumption, a meter is also installed to measure solar production and home energy use."
With this update, Tesla Energy now clearly says that the inverter is also a charger (like well known energy storage inverter/charger used for years now) which is the only way to Charge the Powerwall with Night Rate (TOU) cheaper Electricity (if you want/decide to do so)
So as I understand it, the Inverter required to be able to use the Powerwall is a specific one, and my/your existing Solar install Inverter will most likely not be compatible and will have to be replaced with one from Fronius or Solar Edge (the only 2 options for now)
Also from this update, they tell a bit more and at last mention that a Specific Meter has to be installed too, obviously, to know the Usage/Generation/Net Usage, and decide from that what the Inverter and Powerwall will do ... Now it all makes sense, because all this information was hidden/not given for months ...
When I learned about the RS-485 protocol being used to communicate (Meter <-> Inverter <-> Powerwall), it reminded me of a interesting discussion 2.5 years ago (on my DIY ESS Kit website):
It was a bit too complex for me (I like to keep it simple), and required a high voltage battery pack to be able to use a regular SMA inverter controlled by RS485 to provide the desired Power Output ...
By the way, SMA recently said it could be Powerwall compatible (they used RS-485 on older solar inverter, Sunny Island and their latest Sunny Boy Smart Energy)
I found this nice preview of the Powerwall Online Portal / Interface
Since the end of September with the visit of India PM Narendra Modi at the Fremont factory we know what the Powerwall looks like from the inside !
How did I choose ?
Max Power Output
What is interesting with the Powerwall is that it can produce 3.3kW with only one unit, which would be perfect for my home, as I rarely use more than that, with few peaks will cooking with stove and oven on at the same time, or maybe when heat pump plus cooking in winter, but it does not last long.
Elon Musk announced 2kW during the Powerwall launch, then said few days later that it could be doubled easily, but now it looks like they settled at 3.3kW (from the website specs)
To match this Power Output with the Enphase AC Battery, you would need 3,300 / 270 = 12 units
Each unit being priced at 990 USD (wholesale), that is going to be at least around 12,000 USD
Efficiency: The less you convert, the less you loose ...
The advantage of the Powerwall is that it is wired directly (in parallel) to the Solar Panels Array and stores Energy without conversion (or a minimal one if boosting up voltage to charge batteries); Eventually to use the Stored Energy there will be a conversion performed by the Solar Inverter to make AC Power
The AC Battery takes AC from the Solar Panels after conversion by the Inverters (1), Charges the Battery Pack using the bi-directional Inverter/Charger S-275 (2) and then releases Power back to AC using the same (3): So we have 3 conversions here, instead of 1; even if Enphase makes very efficient micro inverters, we will have to wait and see what is the overall Energy Loss with these 3 conversions
Design
Well it is a matter of taste, but being able to choose the color of this slim and elegant Powerwall is a plus, I will not be ashamed of hanging it in the main room in my apartment, next to the kitchen/entrance cabinet
On the other side, several AC Battery next to each other will not offer the same visual impact, a bulky look which would be fine in a garage but not inside my apartment ...
On this picture, I would install a Dark Red or White Powerwall to the very right, instead of these two frames, and why not, two units later on, but I think one would be enough for my home as I now know well enough what it needs to run ...
- Capacity: 1.2kWh of storage in LiFePO4 batteries
- Power: 275 / 550 W
- Weight: 40lbs
That's not much, but enough to start guessing; I think :
{Update}
Through GreenTech Media, Enphase unveiled their LiFePO4 cells source: A Japanese maker which should be actually cheaper than the Chinese (!) and have been providing residential storage systems (UPS): Eliiy Power Co., Ltd
Japanese Eliiy Power 50Ah LiFePO4 cell
- Capacity: the Battery pack could be composed of 7 50Ah LiFePO4 cells wired in series because 7 x 50Ah x 3.32V = 1,162Wh, which can be considered 1.2kWh, and would give a pack voltage of 7 x 3.32 = 23.24V in the range of the Enphase M250 operating voltage below
- New S275 Micro Inverter : This New Special Bi-Directional Grid Tie Inverter, Enphase's 5th generation inverter, is capable of 25W more at 275W; Here it will be charging (from AC) and discharging (into AC) the pack at 275W and this 550W probably means that 2 S275 inverters could be running in one AC Battery units to double power ouput (?)
- Weight: The rather small unit is light enough to be mounted on any wall, since it is actually lighter than some existing inverters and this could be more important than you think because people do not want to waste space in their garage or basement as seen already with Tesla / SolarCity backup only storage systems installed in California (even if this could be mounted anywhere in the house or apartment)
The AC Battery can be added any existing Solar installation, not only Enphase based ones of course; That means that the Bi-Directional Inverter is using AC only, and from what we can see on the drawing below, the Enphase Storage Solution would require Load Controllers (on the every outlet ...) like seen in the SMA Smart Manager Solution
The AC Battery units will communicate with the Enphase Energy Management System (EMS) Control called Enphase Envoy-S using power line (PLC), like it is with the existing M* Grid Tie Inverters of the brand, via their Engage AC Cables, but we also see a WiFi sign near the Load Controllers meaning they will use this to report appliances Power Use to the EMS through a new Envoy Communication Gateway (the Envoy-S that is)
This Envoy-S would know how much Power is in use at home, how much is Generated by the PV array, calculate the difference and tell the AC Battery to Charge or Discharge, to keep the Home Net Usage equal or close to 0W, by Storing surplus PV Power or Using Power from the AC Battery units, to help the PV array power appliances at home during the day and at night when the sun is down
I also think it will be capable of powering on and off these AC outlets through WiFi, triggering loads when surplus PV Power can be used directly by appliances instead of being stored in the AC Battery units
Simply mounted on the wall, these AC Battery units can be added one by one and provide more Storage Capacity and also more Power Output to cover your Home loads, in the end more savings because lower Energy bills from your utility company :)
We do not know the retail price of one unit yet, but I guess it could be around 1,000 USD (?), based on the price of the cells and existing Enphase inverters
For Report, Follow up and Analysis, the Enphase Enlighten Portal will be used, like it is already for a regular Enphase Micro Inverter install; You will be able to see how much Power is beeing stored into each AC Battery unit, how much is drawn from it, its State of Charge and all kinds of interesting graphs from any smartphone, tablet or PC, which is pretty cool :)
So, I think Enphase will indeed deliver a great solution, because it will be scalable, able to integrate to any existing PV install, using a very efficient proven inverter to Charge and Discharge the BAttery Pack, and safe because based on the LiFePO4 Lithium-ion chemistry
I think a big part of it is if you go back to our beginnings, we are not Enphase solar, we are not Enphase microinverter, we are Enphase energy. And so the overall vision was always to participate in a broader energy ecosystem. If you think about storage it's becoming more of an extension of what solar needs, it's not a "are we entering into storage?" it's more of a natural extension of where solar needs to go.
In Hawaii, parts of Europe, Queensland in Australia you are getting to the point where you need storage to be coupled with a solar solution, to actually start getting solar to the point of higher penetration.
So it was a natural extension. We thought it was the right time, where it is still early in the industry days, but when we think there are use cases in all the areas like I talked about. But I think this is now when storage is starting to get more-and-more traction with our solution, where you get price competitive, you get a more modular solution, where people can put a few [AC storage units together] and then expand out.
I think now it truly starts getting into the beginning of the market truly taking off. Why storage? It is a natural extension of what we were doing with energy management and I think it's the right time when the market, in a year or two really takes off.
What is the significance of having the Enphase 5th generation S-Series microinverter actually in the battery unit?
The way of thinking about this is if you see solutions out there on the market, there are big massive power conversion systems and you are trying to combine that with massive battery systems and our whole way of thinking was, how can we make this modular and simple, the way we did with solar? It sounds like a catch phrase, but it truly was, "can we do for storage what we did for solar?"
The true breakthrough was this bi-directional microinverter, that's what makes this possible. With that now you have the possibility of connecting that to a very modular, scalable small pack. It's about a 1 kWh to1.2 kWh solution. And you combine that and now you have a complete solution with which people can just plug and play.
You can now size for different needs. Let's say you buy an EV, and you want to charge it later on with cheap solar that you have stored during the day, it's not easy to expand a storage system today. That's where combining those two technologies and making a fully scalable modular box is the exciting part for me.
So modularity is key, but doesn't it add to the cost?
Storage is still new, there are early adopters who irrespective of the cost will put storage in because they think it is the right thing to do. But I think if storage is going to move into the mainstream it's important for people to get something that they can afford on an entry level and try it out.
Modularity is a big part of the value proposition and a big part of the thinking behind making this modular is that our existing installers can go and sell one or two of these, get the customer comfortable with it, demonstrate the benefit and then without any system changes go in and put four more. You just get four units, mount them, connect them in and then you now have six instead of two. And so I think that was giving the customer the flexibility that doesn't exist in the market today, I think that is a big part of the value proposition that we wanted to bring to the market.
The AC battery looks very much like a residential product, is this indicating that residential really is the sweet spot for Enphase?
I don't think so at all. It definitely is an area we know really well and we do really well in. But our new C250 Microinverter System, that pushes us further into the commercial side. Just the same way that we have shown microinverters are scalable with large commercial and we are even in conversations about doing utility scale, the same thinking applies to the AC battery solution.
We can rack them up in a big telecom rack and we are starting to speak with customers of commercial solutions that are 8kWh or 10kWh that you can mount on feeders and serve different parts of the commercial segment.
So yes, we are starting with residential, but given the interest that we have seen we expect commercial to follow very closely behind that.
There is a lot of hype here at SPI about storage technologies and the effect it will have on the PV industry. Do you honestly believe that it will have a major impact?
I think it will. I think there is a factor of timing, maybe that will be two years from now or four years from now, that is the crystal ball question everyone is asking. But I think it has to be. We've seen places like Hawaii, Queensland, Germany, where people simply connect solar to the grid and in a high penetration area it does create a lot of issues for grid stability.
As the industry matures and it continues to integrate with the solar industry, I think it just makes a lot of sense for managing intermittency, providing some peak shifting, I think in a lot of cases it will soon get to a point where to have a high penetration of solar, you are going to need to have some level of storage. It's not an if, it's more a question of when that that will become a reality.
What sort payback period are you talking about with the AC battery?
I think battery storage makes more sense in some areas than in others, that is the overall story with storage. We hope that making it an overall, modular product makes it easier from a price perspective and installation perspective.
The areas where the AC battery makes sense are the ones I keep repeating, Hawaii, Queensland, etc. But I think that as net metering keeps going away, where FITs keep going away, then it starts becoming a bigger financial case. The other part that is exciting is that we are talking to utilities about using our batteries not just for demand response but now the same new microinverter have on the rooftop, it actually provides reactive power. That becomes interesting because the utility can give the homeowner an incentive to provide them with grid stability, rather than paying big rate-based systems that they actually need to buy and put on the feeder.
Like peaking gas plants and the like?
Exactly. So I think that is where the financials will get to a breakthrough phase when the utilities begin to participate to the whole equation. It might be behind the meter, but the utilities can benefit from it and actually give some of the economics back to the homeowner. That's where storage really takes off.
How are you planning to roll out the AC battery?
We are beta testing it next year, in the U.S., Europe and Australia. Then the full launch will be in all of those places, one after the other. We are trying to go global on this really fast. That's because the use cases for the AC battery are not only in the U.S., it is in California, Hawaii, maybe the north east. So to capture the whole market you have to go to different places.
The beauty of that is that our microinverters are used everywhwere today, and so we understand those markets, the technical requirements etc. and so it's the exact same requirements that we are putting inside. Yes there are some regulatory differences with storage between markets, but they are not new markets for us, so we are prepared to enter all of those pretty quickly.
The AC battery has a storage capacity of 1.2 kWh with an estimated lifetime of 10 years. Enphase plans to begin rolling it out in the second half of 2015.
As solar energy becomes more common we may need energy storage to help stabilize the grid. Image source: SolarCity
Within the next 25 years every home will not only be connected to the electric grid, they'll have their own energy storage system that will keep the lights on in a power outage and help make energy more efficient for everyone to use.
That may seem like a wild concept but some of the most forward thinking companies in energy predict that energy storage will soon be accompanied with every solar energy system in the U.S. With as fast as the residential solar industry is growing it's only a matter of time before a battery box may be hanging in your basement.
Storage solutions are here
Companies have been testing storage solutions for years but they're finally starting to see the light of day in the consumer market. SolarCity (NASDAQ: SCTY) has launched an energy storage solution for the home and a commercial offering with the help of Tesla Motors(NASDAQ: TSLA) . The system isn't meant to be a way to go off-grid but it'll keep the refrigerator working and the lights on in a power outage.
SunPower (NASDAQ: SPWR) has introduced a similar small storage system and is offering it in new homes built by KB Home (NYSE: KB) . Like SolarCity, the goal isn't to allow homeowners to go off-grid, but storage will instead be used for backup power in case of emergencies.
Inverter maker Enphase Energy (NASDAQ: ENPH) jumped into the game this week with an AC battery that's meant to be an easy to install addition to residential and commercial solar projects. Enphase is making the product modular so more than one battery can be put in a home, and it's supposed to allow for smarter energy storage for nighttime or high consumption usage instead of just drawing energy from the grid.
SolarCity's commercial energy storage solution, built by Tesla Motors
Why energy storage is the future of energy
These energy storage solutions may seem like small steps but they're part of a much larger move into making distributed energy production smarter and more efficient. Right now, homes and businesses that have solar systems are pushing power to the grid or drawing from the grid at unpredictable times, forcing utilities to run spinning reserves and putting strain on the local distribution network. If built properly, even small energy storage systems can smooth out the load on the grid and make the entire network more efficient.
As the cost of solar power comes down the industry will grow to nearly every home and I think these energy storage solutions will become a standard offering as part of a solar system. As that critical mass is reached, storage will become even more important as a way to stabilize the grid, even with small storage systems. That's why I think it's only a matter of time before we all have energy storage systems.
Where to make money in energy storage
Companies are rushing to get into energy storage but the winners may not be who you think. Batteries are already a commodity product around the world and most energy storage systems are using lithium ion batteries that are essentially plug and play in the market.
Instead, the companies integrating batteries and solar systems will be the big winners long term. For example, SunPower's energy storage solution is also the solar system's inverter, turning DC solar electricity into AC power we use in the home. This full solution is where the value is added, not just in the batteries.
SolarCity is doing something similar, although it isn't yet an inverter manufacturer. But as Tesla Motors builds out its Gigafactory and batteries become a more common offering I would be surprised if they didn't start making inverters with energy storage included.
This is also the strategy Enphase Energy is taking, being the point of contact for the grid, energy storage, and the solar system.
Energy storage will be another important tool in the kit for solar companies in the future and those who can integrate it effectively will be a step ahead of competitors. As SunPower and SolarCity add energy storage look for them to continue to be big winners in this space but keep an eye on Enphase Energy. It is moving into more of an energy management role and that's a better way to add value to this space than just supplying a commodity product like inverters to the market.
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