Pure Planet solar panels and battery pilot - getting started with the tech

  • 11 August 2021
  • 19 replies
  • 408 views
Pure Planet solar panels and battery pilot - getting started with the tech
  • Community Manager
  • 7636 replies

I’m about 10 days into taking part in Pure Planet’s solar panel and battery pilot, in partnership with Lightsource Labs.

We’re testing out the installation and set up of solar panels and home battery storage in a series of pilots before offering them to all our Members.

Our aim is to understand the best ways to offer solar panels and battery storage to Members to generate and store their own renewable electricity at home, as well as sell unused energy back to the grid.

For the pilot we’re also using home energy management technology – Tribe – a platform to monitor and optimise live energy generation, storage and usage. 

This post is an introduction to the hardware and software I’ve started using over the last few days. You can read a bit more about the pilot partnership, the participants, and the installation process, too.

First of all, the hardware. The solar panels are on the roof (er, obviously!!) and they generate electricity and feed it into an inverter which converts it from DC into AC for use in the home, or into a battery which stores it for use later. The battery is connected to the fuse board and to a Tribe box.

This Tribe box, which sits next to your electricity smart meter, is the information hub which ‘speaks’ to the Tribe app on your phone, via your home wifi. And it’s the app which gives you information on how you’re using, storing and exporting energy generated by the solar panels.

This infographic probably explains it better:

Tribe diagram

 

The system is set up so that the solar panels power the house first, then top up the battery, then export to the grid, in that order.

This screengrab of the app, of the ‘flows’ section, taken last week, shows the panels generating 2.779 kW of electricity, with the house using 0.336 kW. So the rest is going into the battery, which is at 60% full.

Topping up the battery

Once the battery reaches 100% the system automatically starts to export excess electricity to the grid - Pure Planet buys the electricity and supplies it to other Pure Planet Members. I get paid for this too via Pure Planet’s Smart Export Guarantee tariff.

The app ‘flows’ view changes to this:

Exporting electricity to Pure Planet

It’s pretty cool watching the ‘flows’ change in real time. It responds immediately to changes in the weather. Even a 10-second burst of sunlight as moving clouds race across the sky causes the app flow to show the solar generation ramping up.

Typical daily usage shows the battery at close to zero % in the morning, gradually increasing in charge throughout the morning and afternoon, usually powering the house at the same time. In the evening when the solar panels don’t get any more light, it switches to pure battery mode, and we usually last until the early hours. Unless the EV gets plugged in, in which case the battery drains much faster!

Another interesting observation is that we really don’t need full-on sunshine for the panels to generate electricity. Even on grey, cloudier days, we get close to a full battery by the afternoon, and rain doesn’t seem to make too much difference either. I suppose it’ll be a different story come the Winter, however.

The ‘graphs’ section of the app shows the same information as flows, but as an overview of a day, week or month.

Here’s an example of one day, 4 August, showing PV generation in the morning, the battery  level or ‘state of charge’  (SOC) lasting through the afternoon with some exports. There’s occasional flurries of importing electricity which I imagine is cooking and making coffee. 

Tribe app daily graph

The summary page shows the total consumption by day, month or year.

Loads is where you can add more batteries, and control charging of your EV, for example. I’m not about to add any more batteries for the foreseeable! 

So, that’s my first look at the tech. There’s more to come as we start to try out the Tribe system’s more advanced features. This is when it uses machine learning of my energy usage to start predicting my consumption, and combined with weather forecasts, automate how energy is used more efficiently.

It starts to get really interesting as it means the software can predict when I will need my generated energy, how much to export back to the grid, and how much to retain in the battery.

There’ll be more posts on all that coming soon!

Happy to keep chatting about the app and basic set up here of course.

Read more:


19 replies

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Really interesting @Marc . 👍

I find you can spend too much time looking at the graphs and wondering what used the energy.

If you try to aim for zero grid usage during the summer then you start to be more concerned about peak usage (i.e. cooking, while also having the washing machine and the kettle on).

I also alter my charging behaviour if the app shows the battery is pretty full and there is additional solar so that the energy goes in the car instead of being exported at that point and reimported by an overnight charge.

The combo of battery and panels looks really good and tides you through the evenings nicely. Great that you fill the battery even on cloudy rainy days! Like you say, might be a different story when the sun is lower in the winter.

How come there are imports coinciding with the time when you are exporting?

Importing during exports

The schematic seems different to what you describe as the battery is away from the panels. Are there really two inverters? Or does the DC from the panel go straight to the DC of the battery?

If you were on the E7 tariff during the winter, could you import electricity during the night to charge the battery and use during the day?

 

Great update @Marc. That’s enough questions for a Sunday! 😊 

I find you can spend too much time looking at the graphs and wondering what used the energy.

If you try to aim for zero grid usage during the summer then you start to be more concerned about peak usage (i.e. cooking, while also having the washing machine and the kettle on).

I also alter my charging behaviour if the app shows the battery is pretty full and there is additional solar so that the energy goes in the car instead of being exported at that point and reimported by an overnight charge.

Indeed @Mark Pocock Having the panels and battery has changed my EV charging behaviour. Even though we (PP) don’t have an EV tariff yet (coming soon!) I still used to mostly charge overnight, as it was convenient.

Now I’m charging more in the daytime, if I’m at home of course, usually early afternoon if the battery is full and lots of sun. 

Oh, I can def spend too much time looking at the graphs!! (They actually stopped working over the weekend - no data available was the message. All part of this ‘pilot’ I suppose).

Out of interest, do you use an app to monitor your usage?

@Marc Thanks. Great to get a hands on experience. Much more valuable than the pundits pontificating. For some years now solar panels have been designed to work when there is not full sun, solar thermal panels even more so. On a much smaller scale, very much smaller, I have instead a solar panel to keep an outside camera charged up. It is about A5 size. I notice it is working on cloudy days but not as well as sunny days.

@woz I am sure will provide you with a spreadsheet to plot the daily power generated usage!

The combo of battery and panels looks really good and tides you through the evenings nicely. Great that you fill the battery even on cloudy rainy days! Like you say, might be a different story when the sun is lower in the winter.

How come there are imports coinciding with the time when you are exporting?

Importing during exports

The schematic seems different to what you describe as the battery is away from the panels. Are there really two inverters? Or does the DC from the panel go straight to the DC of the battery?

If you were on the E7 tariff during the winter, could you import electricity during the night to charge the battery and use during the day?

 

Great update @Marc. That’s enough questions for a Sunday! 😊 

Excellent questions @25 quid 

I had to check these out with m’learned colleagues, but I have the answers.

How come there are imports coinciding with the time when you are exporting?

This is to do with the granularity of the graph. If the x-axis was at one second intervals we would not see import and export at the same time, but because it is 'zoomed out' we see less granular info.

For example, if the x-axis shows 1 minute intervals and in a given minute I was exporting for 30 seconds and importing for 30 seconds, then we would see both.

 

Are there really two inverters? Or does the DC from the panel go straight to the DC of the battery?

It’s one inverter. This is a DC connected battery so battery and solar share an inverter. An AC connected battery would have two.

 

If you were on the E7 tariff during the winter, could you import electricity during the night to charge the battery and use during the day?

Yes!  I could set the battery up to charge whenever I want, whether to do it at off peak (traditional two-rate approach) or when prices are best (the ‘dynamic’ option).


 

@Marc 

My battery is a Tesla powerwall so I use the Tesla app to monitor everything (except for the Zappi and Eddi which are on the MyEnergi app because the battery just shows them as home usage). In the winter we just charge overnight (plus car heating in time for the morning commute).  In the summer we tend to charge small amounts immediately at the end of the day or during the next day if the car is at home. Larger charges are just deferred to overnight.

 

How come there are imports coinciding with the time when you are exporting?

This is to do with the granularity of the graph. If the x-axis was at one second intervals we would not see import and export at the same time, but because it is 'zoomed out' we see less granular info.

For example, if the x-axis shows 1 minute intervals and in a given minute I was exporting for 30 seconds and importing for 30 seconds, then we would see both.

I get the idea @Marc, but it sets my spider senses tingling. How come the only time there are imports are when there are also exports? That doesn’t hold water. I think there’s a fish out of water and a reporting glitch to be investigated… 😉 

My battery is a Tesla powerwall so I use the Tesla app to monitor everything (except for the Zappi and Eddi which are on the MyEnergi app because the battery just shows them as home usage). In the winter we just charge overnight (plus car heating in time for the morning commute).  In the summer we tend to charge small amounts immediately at the end of the day or during the next day if the car is at home. Larger charges are just deferred to overnight.

Thanks @Mark Pocock 

It’s really interesting (for me, anyway!) how this technology is going to change our behaviours over the coming years. And, of course, future generations will know no different. 

Oh, and I love the car heating feature. Such a simple concept, that the house is defrosting the car’s windscreen, but a powerful one. 

I’ve got 18 months left on the lease of my Nissan Leaf (40kWh battery edition), and I have to admit I’m already stating to have thoughts about which EV I’ll go for next. Pretty sure I will lease again (unless someone rich gives me £40k or so) and I’d love to go for a Tesla. For the range/performance, yes, but also for the in-car tech. 

Hello.  I have had a SolarPV system for over 5 years.  It is a 4Kw  microinverter system generating about 3.5Mwh annually, with an Enphase system feeding surpluis energy to my immersion heater and the rest to the grid.  Cumulatively I am using about 1.6Mwh ( 45%) internally, 0.7Mwh (20%) to immersion heater, and 1.2Mwhh (35%) to grid.  My annual external electrticity consumption is about 1.9Mwh

What would be the advice aboiut the cost/benefit of a battery storage?   At the moment I am thinking that the saving against my current cost of electricity of abour £350/year v cost of battery storage would make the payback period too long to justify the installation 

 

Fab post. Great question @johnasaul — I don’t know, but I suspect you’re right about the payback time.

Thanks for reply.  I was quoted  £3000 for a £5.2KW battery, and as the likelinood of gererating enough to store in the winter is unlikely, I have assumed that the saving wil be about 50% - £200 per year. This equates to 15 years before costs are recovered, perhaps less if electricity costs increase significantly. I have ignored interest costs  As the lifetime of a battery is up to 15 years, then I will just about break even before I have to get a new battery. My conclusion is that the battery costs woiuld need to reduce by half before I wil consider it.

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@johnasaul 

I agree

You’d be better off spending the money on improving insulation (if that is viable).

Did you allow for the fact that:-

Your export to the grid won’t cover charging the battery (or at least that’s what I calculated, with  no inefficiency allowed for  at 5.2kWh a day is more than your current export?)

and

even if you were to save the 5.2 kWh a day from what would be the export you’d lose any feed-in payments so the payback looks worse still

On the other hand if there was a tariff where you could charge the batteries at very little cost that might be worth another look.

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@johnasaul 

The first thing that struck me reading your post, was that there must have been a similar dilemma when getting the panels fitted ( unless they were already there when you moved in ), and probably a greater outlay since panels are quite expensive 5 years ago. As already mentioned, another factor in the payback time is the loss of any export income, although it will always be less than the amount you are paying for your imported energy

Thanks all for your observations.  I am going to wait a while to see if the battery prices come down or there is some subsidy.  My current setup is giving me a 8 year payback, and I automaticaly get 50% export credit,  however much I actually export, so the incentive is to use as much as possibly internally, hence loking at a battery

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I'm sure you're already busy drafting your next update @Marc , can't wait to hear what you've found now you've had the installation a bit longer. This is tech that I'm quite excited to have the chance to get to use in the next couple of years, and I'm very happy that I'm with PP at a time when you're trialling it in such an open way, so this pilot project is very useful.

I'm sure you're already busy drafting your next update @Marc , can't wait to hear what you've found now you've had the installation a bit longer. This is tech that I'm quite excited to have the chance to get to use in the next couple of years, and I'm very happy that I'm with PP at a time when you're trialling it in such an open way, so this pilot project is very useful.

It’s like you’re in the room @Antski :laughing: I am indeed drafting it right how. Just had my monthly statement so energy usage has updated, and I can see how what’s changed already in less than a month. 

I’m waiting for my energy usage to tumble now I’ve binned my old 50” plasma. Maybe I should get my account reviewed?? Who needs solar and batteries! 😉 

I'm sure you're already busy drafting your next update @Marc , can't wait to hear what you've found now you've had the installation a bit longer. This is tech that I'm quite excited to have the chance to get to use in the next couple of years, and I'm very happy that I'm with PP at a time when you're trialling it in such an open way, so this pilot project is very useful.

It’s like you’re in the room @Antski :laughing: I am indeed drafting it right how. Just had my monthly statement so energy usage has updated, and I can see how what’s changed already in less than a month. 

Here it is @Antski fresh from the, er, printers…..

 

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