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dwilliams
For most days over the first week we have not had ideal generation weather. Apart from one mainly rainy day we have had cloudy starts, lots of high fair weather cloud and a few short but intense periods of sunshine. Even so, performance seems to be getting better. Charging seems to be quicker and the battery is lasting longer. Maybe Lithium batteries need time to condition?

Anyway, last evening the battery topped out at 96% and for the first time has continued to provide power until 0225 this morning. A somewhat odd (in my opinion) feature of this system is how it “defers” the generation. I expect many of you will be able to look at the weather conditions at any moment of time and make a good guess about how much your system is generating. From the very first day I noticed that when I would have thought the system would be generating, say, 1700w the SolaX system showed it to be about 700w. When the sun finally set I had clocked up a rather disappointing 8-9 Kwh when I might have previously expected 15-16Kwh. However, by the next morning my generation meter had caught up and all was well. This is because the “missing” generation is recorded later as the battery is discharged.

If you have a look at the attached screenshot from today you will see on the top graph how the battery is finally exhausted about 0225 hours (2). Although the sun set many hour earlier you can see from the bottom graph how the Yield is still running high past midnight, tapering down to cease as the battery becomes exhausted. I have absolutely no idea why there appears to be a sudden demand as shown at (1).

Kevin and others have previously asked if there is any facility to top up the batteries from off-peak power. I asked exactly the same question prior to purchase and was told well yes, but currently no in the UK. There is certainly a setting in the configuration that allows you to set 2 “charge from grid” periods. Both of these are shown enabled on my system but it doesn't actually do it. It was explained to me the reason is that SolaX think it would be frowned upon to buy power at off-peak (6p) and then effectively sell it back as generated power at your FIT rate as your battery discharges … because of the deferred generation feature. However, it seems that the same question is being asked by others, and it is not an unreasonable requirement in the winter when sun is in short supply. It is my understanding that they are “working on it”.

While researching this prior to purchase I came across 2 documents, one from Parliament and another from OFGEM which seems to see the option to “time-shift” your use of power as being something to be encouraged in the future. I will upload those documents for others to see.
dwilliams
Here is one of the OFGEM documents I refer to:
dwilliams
Here is the other OFGEM document:
dwilliams
And here is the Parliamentary document:
WendyNorthrop
Hi,
You should refer your installers to Scottish Power's Cruachan hydro-station, it has been operating for over 50 years. ( I have visited the installation: it is an exceedingly interesting location near Oban in Scotland)
As a matter of course water is pumped up to a holding lake using off-peak power and released at times of high-demand… the generated power is sold back at a higher rate.
Furthermore if our electricity-grid is to meet demand more effectively, it must be re-designed to store surplus electricity: regardless of the cost or mode of generation.
I occurs to me that the wide-spread use of electrical storage-heaters is another example of low-cost energy storage which is designed to off-set higher running costs and peak-time demand…
Thank you for your interesting posts
dwilliams
Hi Wendy, our installers did mention a hydro-power plant as you describe as a precedent for selling back power at a higher rate than it was imported. Also, I made the point that people have been time-shifting demand and usage for years with storage radiators, immersion heaters etc.

I am pleased that you find my posts interesting and I am presently compiling an update after doing a bit of tweaking. Hopefully I will get that finished and uploaded in the next day or so. It is clear that many people, myself included, see the ability of a system to charge from the grid at off-peak rates to use during peak periods as an absolute must. I can now say for sure that the SolaX X-Hybrid certainly can do this although I have personally left the setting as disabled for now.
gevans
My 4Kwh PV system was installed in July 2011 and has run unattended since then and I'm quite happy with its output and the FIT collected.

I have been considering the possibility of battery backup but I'm unsure how to measure my base load to see whether it would make economic sense. I realise that the answer is probably very simple but as a “Plug-and-Play” PV user, I should welcome any suggestions here.

Secondly, rechargeable Lithium batteries have a typical advertised life of 1,000 cycles (about 3 years with daily charge/discharge cycles). Can you tell me what evidence is there that Lithium batteries for PV system backup have a longer lifetime than this ?
dwilliams
Hi, I hope you got my email and attachment with the Lithium battery technical details. With regard to measuring your base load there are several ways. There are many devices on the market, I personally have used an Efergy device for years http://efergy.com/eu/#in-home-displays. If you go that way be careful because I have found that in the day time the measurement can be skewed by your PV generation. This is more of a real-time/now measurement of your usage which changes constantly.

A simpler and perhaps more accurate way would be to use your normal electricity meter. Ideally on the hour, say 2200, before bedtime take a reading including the decimal point. When you get up and before putting on the kettle, toaster etc. take another reading, ideally on the hour again. Note the units used and divide by the number of hours. This should account for all the things that are constantly running like central heating, cordless telephones, anything you leave on standby. Do this over a number of nights to get the most accurate picture. It is important that you do not run anything with a big demand overnight like a washing machine or dishwasher as this could seriously skew your results.
dwilliams
Our battery storage system has been installed and working for over 2 weeks now. Looking at the graphs and considering how and when we are using energy has given me a much better idea of how the system works.

We have been on an Economy 7 tariff for many years. During BST the off-peak periods are from 2330 to 0130 and again from 0330 to 0830. I didn’t see how this would work well with my belief that battery storage worked by storing during the day and discharging during the night … wrong again.
Now the ideal situation would seem to be to maximise our use of imported off-peak power from the grid (roughly 6p a unit) thus ensuring that the majority of our valuable self-generated PV and stored battery power is used the minimise our need to import peak power (roughly 15p a unit).

I mentioned in an earlier post that the SolaX X-Hybrid system has a setting called Work mode. There are then 2 options, Self-Use & Force Time Use. Since installation ours has been on Self-Use and I understand this is the preferred setting for the majority of customers who just want a plug & play solution. The “problem” with Self-Use is that you see all that lovely stored energy being discharged 24 x 7 to meet demand, even during the off-peak tariff periods. Time for a bit of tweaking!

Within the option Force Time Use you can set 2 distinct discharge periods. I have set them to accord to the minute with the PEAK tariff periods. After 36 hours or so you can see the effect on the graphs so let’s step through Tuesday 24/5 a pretty good generating day, and Wednesday 25/5 which was less so.
I did the tweak a little after 0600 on 24/5 and it took immediate effect. The battery did not discharge power to the house and neither did the solar generation which started at 0645 that day. Instead, the solar generated power was diverted exclusively to the battery which charged from 20-30% until 0830. At 0830 the off-peak tariff period ended and the system switched to ensure that the solar + stored battery power was used to power the house (this is where the blue line below the 0W line switches to above the line). You can see it was a generally good solar generation day until 1200 and then more fair weather cloud developed. Solar generation, the green line, tapers off and ends around 1930 but the blue line continues to bob along at 0W as the battery alone powers the house. You can see an occasional dip in the blue line as demand exceeds what the battery can supply so we pay for a little from the grid at peak rate. The battery, which had charged to near 100% capacity during the day, continues to power the house right through to 2330 hours. At 2330 hours the setting in Force Time Use comes into effect and power is drawn exclusively from the grid but at off-peak rate. This continues through midnight and we pick up the next day on the bottom graph.

EDF doesn’t let you have a continuous 7 hours of off-peak electricity but rather switches back to peak-rate for 2 hours at 0130. At 0130 the setting in Force Time Use comes into effect and power is drawn from the battery once again and this continues until 0330 when off-peak rate resumes. From 0330 until 0830 we import grid power at off-peak again. Meanwhile, solar generation starts again soon after 0600 and the batteries get a good head start charge until 0830 … and so it has continued each day thereafter. A rough calculation of what that means in monetary terms is included on the graph.

Further updates and analysis to follow in due course.
AndyT
Hi there, I have not seen Heat Batteries mentioned, so please excuse me if I do.
I was fortunate enough to become a trialist of the SunampPV and it was fitted in March 2015.

This is a direct link http://wattson.energyhive.com/dashboard/AndyT
You can select views by day month or year and how much was being exported before the SunampPV was fitted.

Storing excess generation in phase change materials (PCM) a salt solution as latent heat, the SunampPV preheats the cold supply to the combi boiler. It's fair to say been working very well.

When I was made redundant in May last year I decided to ask Sunamp if they had any vacancies, and they took me on. Since then I increased the size of the heat battery from 5kWh to 10kWh.

If anyone would like some non-sales information on this technology I would be pleased to help.

Kind regards
AndyT
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