EcoElectric
It seems as if a new type of hybrid battery system is hitting the market every day. These systems are highly technical and their overly simplified specification sheets rarely provide the information required to make an accurate comparison.
Advertisements are focusing on big numbers such as peak ratings at 25 degrees and terms such as ‘battery ready’ and ‘cut the cord’ are being brandished with fool-hardy abandon. Prices which really are too good to be true, will see some homeowners losing very serious sums of money through lack of performance, or product failure.
In the absence of specific advertising regulations, we have developed a quick guide on what to look for, and how to compare hybrid battery systems and spot their limitations.
The very first question you need to ask yourself is do you need, or even want backup power? If the answer is yes then the system costs will in most cases double. If the answer is no, then you’re after a ‘load shifting’ battery system which will take excess solar PV energy and store it for later use at night. You can expect to pay between $10K and $15K for a quality system with this type of capability.
There aren’t anywhere near as many traps with load shifting as excess power is drawn from the grid, and there is no critical backup functionality. A typical design methodology looks at the lowest amount of power you would use every night, combined with a matching amount of spare PV energy. Since batteries of any type are expensive, it makes no sense to size storage if the usage isn’t there. Choose a figure that will get cycled every day and ensure that there is enough PV there to keep it topped up on all, but the darkest of days.
The traps in these systems revolve around cycle life and usable energy. A good PV company will quote their battery systems in usable energy ie kWhrs with a given cycle life at that amount of energy. For example, an LG Resu 6.4 has 6.4kWhr of usable energy but only 90% of that will be used over the stated life cycle of 6000 cycles. Effectively that means the LG is a 5.7kWhr battery. If you’re looking at gels, or lead-acid then you’ve most likely been quoted on a depth of discharge of around 35% with a battery life of 5 years (1825 cycles). Is that system still cheap when you factor in replacing the batteries 3 times?
Another way to look at this is usable energy multiplied by number of cycles equals lifetime energy output. This is a good overall comparison, but be aware that it doesn’t account for other limitations such as maximum discharge.
Due to depth of discharge and its effect on cycle life it is very easy for an unscrupulous company to twist the numbers in their favor. Currently, in many cases it is near impossible to compare various systems as the statistics are often vague and misleading. To counter this we believe there needs to be an ACCC authorized code for battery systems which would include guidelines on advertising. To make comparisons easier for the consumer, all batteries being advertised should be listed as usable energy with a given cycle life, and clearly show its nominal discharge rating at 25 degrees. Such a code would be voluntary – similar to the Solar Retailer Code of Conduct diligently developed by the Clean Energy Council.
Our thoughts on this topic have been somewhat inspired by a recent customer who complained that our SMA LG off-grid capable system was some $10K more than an Alpha Energy Storage System (ESS) from a competing company. The Alpha is a great product with many applications, but in this case it was unsuitable for the site and would result in loss of supply. We found it extremely difficult to explain this to the customer, as the amount of detail provided by our competitor did not outline the limitations, nor did it include any sort of site or load survey. After much analysis, here are the problems we found;
Its unfortunate that in the end we lost this particular quote, as I really do feel as if this customer was overly focused on price and will be disappointed with the overall outcome. One of his statements to me was, “I can’t justify the $10K difference on top of this $25K system.” My question to him was, “Can you afford to spend $25K and have it not meet your needs?”
I’m guessing we will get a phone call in roughly 12 months time due to instantaneous overload. It could also be in 5 years time when the batteries, which having been twice daily cycled reach their end of their life span in a third of the rated time. A key issue here is that poor design issues will not become apparent until well down the track. With that in mind, has your solar company been around for longer than their warranty term? Are they aware that an off-grid capable system often requires re-visits to tune and re-check? Do they include such service in their package, or is it set and forget? Can they shift excess energy and provide bundled hot water for free, or will you be left juggling candles in the rain?
Here are 7 questions to ask when comparing hybrid battery or off-grid systems;
At Ecolectric solar is our passion, so if you’d like to have a yarn about battery systems feel free to give us a call.
Source: EcoElectric. Reproduced with permission.
This post was published on November 24, 2015 3:39 pm
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Trank you for the clarification and details on what to look for in a hybrid or off-grid system.