On-grid domestic battery storage

zeupater

orrery said:

I think that the discussion moved in response to my asking whether siting a system in the loft was a wise move given the elevated temperatures in some lofts - mine is completely unbearable for long periods in mid summer. My point was that my garage (attached to the house) has a much more hospitable temperature range - never going below zero and being reasonably cool (comparatively) in summer. So, I was merely pointing out that there may be, in some cases, good technical reasons to install solar and battery systems in a garage rather than a loft. A system in a garage is also more maintainable than one in a loft.

* other peoples lofts and garages may vary

Hi

Effectively it's the same discussion as in the early days of PV .... Lofts get hot, electronics don't care too much for heat, best put the inverter somewhere other than the loft then if you're looking to prolong it's useful life! ... next consideration ....

Like your case, even though our panels provide shade to some of the roof, it's nowhere near enough to reduce temperatures to bearable levels on warm sunny days, whereas the temperature in the garage (integral) rarely goes anywhere near zero even in periods where we've experienced temperatures dropping to <-20C and not raising above -5C for a number of days .... the thermal mass in the property and the floor slab area in the garage just work against wild temperature swings typical to the UK ... if we were located somewhere with a less maritime climate maybe my position would differ, but that's not the case .... 

As a way of keeping an eye on the need for raising the thermal mass temperature in the winter, I regularly check a number of walls with an infrared thermometer and can't remember structural temperatures in the garage going below somewhere around 8C over the past winter when we were having discussions about levels of insulation & thermal mass on various threads, so in the case where batteries in an enclosure would be generating their own heat to some extent the structural temperature shouldn't be anywhere near low enough to be of concern...

HTH - Z

Grandad2b

zeupater said:

I believe you're overthinking and misunderstanding ....

Quite possibly

In your earlier postulation it seems you were considering somehow insulating an ESS so as to increase the operating temperature to take advantage of a better charging curve during the winter ... the information provided is simply a caution on doing this as it would likely shorten the useful life of the ESS itself & it would be up to you to decide whether this approach would be appropriate to your own position and requirements ....

As for ambient conditions, well that's not the issue, it's the operating temperature of the batteries themselves that is important, and the very fact that you'd be looking to artificially increase that temperature through adding insulation and/or airflow reduction that would be more problematic .... keeping the heat in when the manufacturer has designed the system for heat dissipation wouldn't seem to be a very logical step, nor would choosing to site an ESS in a loft where the ambient temperature in the summer could well reach temperatures ~55C. As mentioned in the previous post, raising the battery cell operating temperature has a detrimental effect of longevity, this has been measured and is the subject of numerous published articles in scientific journals - the 3x faster degradation figure is something I picked up on some time ago and was part of a published study involving various charge cycles & temperatures, but if you want to disagree it's relevance, well that's down to yourself & the decisions you are looking to make, but it doesn't mean the paper's findings were irrelevant in any way ...

What you need to appreciate is that in discussions related to electrical & electronic equipment efficiencies, the inefficiencies are normally directly related to energy conversion into a waste product as a result of resistance, so normally heat ... that's why the laptop I'm using often gets much hotter than the ambient temperature of the room and that's why the design of the equipment includes a fan to protect against premature temperature related electronic component failure ... if I were to deliberately restrict the airflow the anticipated lifespan of some major components would likely fall from an average of multiple decades to mere days or hours. In questioning whether this this would be considered a 'red herring' within battery storage because they're different to 'consumer electronics' you seem to be missing the fact that the ESS contains 'consumer electronics' circuitry in the form of bms, communication, control etc so that's effectively what you have ... consumer electronics packaged amongst and connected to a number of battery packs within an enclosure, so no, it's not a 'red herring', it's fundamental

The question you should be asking is how do manufacturers of electronic components have a clue to lifespans being in the region of decades when none of their components have been tested for decades due to the fact that the technology isn't old enough ... well that's where accelerated lifespan testing at elevated temperatures comes into play, they model & test for failure according to some pretty advanced formulae, however, whatever they use generally conforms to the arrhenius predictive findings, so somewhere around a halving of lifespan for each additional 10C of operating temperature ... okay, it's a rule of thumb, but it's one that generally works & should be considered good enough to get an idea through to someone or quickly test assumptions ... again, it's up to you to accept or not accept the answers to questions you are seeking from others, but it's generally considered good practice to openly research the validity of any offered answers prior to subjecting them to dispute just because they conflict with a preset positional bias, if you're not open to entertain answers to posed questions, then why seek answers in the first place ... 

As for the heatloss example, it's not the heatloss that you need to look at, it's the level of heat retention given a level of heat generation at various levels of insulation under consideration. Heatloss under whatever conditions is a function of the DeltaT between ambient & whatever needs cooling, the heat source is in this case a function of the inefficiencies within the ESS and the resistance to heat transfer would be a function of the original enclosure design PLUS the effective U value of the additional insulation you'd be looking to add to the installation ... effectively, adding insulation simply results in raising the DeltaT between the ESS internal components within the insulated bubble and the ambient temperature to a point where temperature (/energy) input & output reach equilibrium .... it's this raised DeltaT that will impact on the anticipated lifespan of the ESS, with the added possibility of creating a very real fire hazard potential.

Finally, in terms of electronic circuitry & lithium battery physical operating temperatures, 55C should not be considered to be anywhere near a 'massively elevated temperature' ... as mentioned earlier, conditions similar to this could be considered to be regularly achievable as ambient for some locations even in the UK, such as a loft, so add in a considerable number of Ohms as an internal heat source and the equipment temperature will be elevated well above 55C even with an unmodified installation.

HTH - Z

I was indeed thinking about that possibility. And you've put forward a cogent argument explaining why you think it would be a bad idea. Thank you.

It's only by asking the questions that we get the necessary information to make informed decisions.
You're right that my thoughts were brought about by stories of EVs failing to charge and I hadn't understood that a domestic battery system is likely to generate sufficient heat to keep itself above freezing point.

As for your dig about not being open to entertain(ing) given answers, that's your perception. I'm asking questions in order to understand and, at the same time, displaying my ignorance of the subject. Maybe there is another forum where I can do that without being patronised.

Grandad2b

orrery said:

I think that the discussion moved in response to my asking whether siting a system in the loft was a wise move given the elevated temperatures in some lofts - mine is completely unbearable for long periods in mid summer. My point was that my garage (attached to the house) has a much more hospitable temperature range - never going below zero and being reasonably cool (comparatively) in summer. So, I was merely pointing out that there may be, in some cases, good technical reasons to install solar and battery systems in a garage rather than a loft. A system in a garage is also more maintainable than one in a loft.

* other peoples lofts and garages may vary

I wasn't aware that the discussion had included the possibility of putting batteries in the loft. I've heard of inverters being sited there and what I now know about the heat generated by the inverter makes me think that's probably not best practise...

1961Nick

Grandad2b said:

orrery said:

I think that the discussion moved in response to my asking whether siting a system in the loft was a wise move given the elevated temperatures in some lofts - mine is completely unbearable for long periods in mid summer. My point was that my garage (attached to the house) has a much more hospitable temperature range - never going below zero and being reasonably cool (comparatively) in summer. So, I was merely pointing out that there may be, in some cases, good technical reasons to install solar and battery systems in a garage rather than a loft. A system in a garage is also more maintainable than one in a loft.

* other peoples lofts and garages may vary

I wasn't aware that the discussion had included the possibility of putting batteries in the loft. I've heard of inverters being sited there and what I now know about the heat generated by the inverter makes me think that's probably not best practise...

The main reason for siting an inverter in the loft is to avoid having to run 4x bulky DC cables to an inaccessible garage. This has a knock on effect with hybrid systems because the battery has to be near to the inverter.

If your solar inverter needs to be in the loft, my advice would be to install an AC battery system with a separate inverter in your garage.

It's likely that inverter manufacturers expect their equipment to be installed in hot roof spaces & build them to withstand those elevated temperatures. The maximum ambient operating temperature of a typical solar inverter is 60C (although some derating may occur before then), whereas a typical laptop is 35C ambient.

1961Nick

Here's a chart of my battery & inverter temperatures for today. I'm pretty sure the sensor for the inverter (radiator) is attached to the heatsink - fast response time to changes in load.

The battery charge was completed around 2.00am & the inverter was then in standby until EV charging finished at 5.30am. 

cm4ever

1961Nick said:

Here's a chart of my battery & inverter temperatures for today. I'm pretty sure the sensor for the inverter (radiator) is attached to the heatsink - fast response time to changes in load.

The battery charge was completed around 2.00am & the inverter was then in standby until EV charging finished at 5.30am. 

Hi @1961Nick could you supply details of the temperature sensors you are using please?

Are they independent from the inverter and batteries i.e. wifi thermometers, if so what make/model are they and how have reliable have you found them?

Although I'm not overly concerned with the temperature of our loft with regard to the solar&storage (where our system is installed), I'm considering increasing the roof ventilation as a whole and need to collect some baseline data to help with considering this possible future change.

zeupater

Grandad2b said:

[ ... ]
As for your dig about not being open to entertain(ing) given answers, that's your perception. I'm asking questions in order to understand and, at the same time, displaying my ignorance of the subject. Maybe there is another forum where I can do that without being patronised.

Hi

Apologies if you consider it patronising to highlight how your reaction to answers given by others comes across .... however, classifying fundamental considerations for electronic circuit longevity as 'red herrings' and questioning the relevance of published scientific journal papers regarding the relevance of heat dissipation & temperature control on the useful cycle life of batteries whilst postulating an alternative viewpoint didn't seem to convey much openness towards entertaining a train of thought at the time ....

Don't get me wrong, the position of entertaining a thought doesn't mean that it should be accepted without challenge, it's just a case that when such conditions arise the norm should include some form of validation exercise, for example, looking for discussions regarding the scientific papers or even reviewing the research at source .... simply limiting the learning process to the same limited subset of knowledge and opinion without source validation often leads to various forms of bias transfer & reinforcement.

So, unlike many looking at this discussion, does my form of bias rely on direct experience in the effects of temperature on large capacity battery systems? .... well yes actually, including the failure of aircon cooling resulting in the cooking and premature test failure of ~20kWh+ battery UPS and damage to a considerable amount of high value electronic equipment circuitry as just one amongst many other examples .... also, having involvement in the design, construction & operation of environmentally controlled test facilities related to performance & accelerated lifespan testing, including that of safety critical components ....so would I be more concerned with permanently raising the DeltaT of electronics & batteries than occasionally operating at somewhere close to the lower design limit, too right I would!

HTH - Z        

1961Nick

cm4ever said:

1961Nick said:

Here's a chart of my battery & inverter temperatures for today. I'm pretty sure the sensor for the inverter (radiator) is attached to the heatsink - fast response time to changes in load.

The battery charge was completed around 2.00am & the inverter was then in standby until EV charging finished at 5.30am. 

Hi @1961Nick could you supply details of the temperature sensors you are using please?

Are they independent from the inverter and batteries i.e. wifi thermometers, if so what make/model are they and how have reliable have you found them?

Although I'm not overly concerned with the temperature of our loft with regard to the solar&storage (where our system is installed), I'm considering increasing the roof ventilation as a whole and need to collect some baseline data to help with considering this possible future change.

The data is from the built in sensor on the inverter which also has a supplementary sensor to attach to the battery bank.

A friend who’s an electrical engineer used a couple of PSU coolers & a thermal relay to add cooling to his solar inverter that is situated in his loft. It reduced the heat sink temperature by 20C on the warmest days last year.

QrizB

I thought I'd bump this thread rather than start a new one

You might recall that I have a home-built storage battery of about 6kWh. I built it from LFP cells that I bought from China, and was really pleased to get the cells for about £120 per kWh. (For comparison, at the time Pylontechs were selling for £400 per kWh.)

Well, CATL have made some interesting announcements regarding their sodium ion batteries (yes this is a press rerlease, not a real journalistic article):
https://finance.yahoo.com/news/catls-mass-production-sodium-ion-004500118.html

They have a lower energy density (per kg and per litre) than lithium ion, which makes them less attractive for vehicular use. However, for static storage that's much less of a problem.

If they can get them to market for US$50 per kWh, it could be a real game-changer as far as energy storage is concerned. If you can save an average of 5 cents a kWh by energy arbitrage, you only need 1000 cycles to break even - that's potentially as little as three years. And using batteries to move electricity from eg. weekends to weekdays could become economically feasible.

QrizB

Thread bump!

There's someone asking about battery storage in the "other fuels" section here.

I've commented, and so has matt_drummer, but if anyone else wants to chip in with an opinion it might help the OP?