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This is of great interest to me. I am in the process of getting solar PV installed at my home (next week hopefully) and I have every intention of getting one of your Mk2 Routers and using it to divert excess power (I am the one who was bugging you on email a few weeks ago ;)).

My issue is I already have solar evacuated tubes on the roof which are very good at heating my cylinder in the summer months. I barely ever have to activate my cylinder heating element in summer. So this means during the months I will be getting the most PV generation, I will already have a cylinder sitting at between 60-80 degrees. 

In winter dumping all excess to my cylinder will work great. But in summer I need to divert to something else. And that something else has been perplexing me! Because, as you point out, most of my other loads in the house would not like being switched on/off rapidly.

So any system that allowed me to divert to something, say a dishwasher, for a guaranteed 2hrs for example, would be perfect for my scenario. The rules surrounding what 'continuous' loads are available and ready for diversion could become quite complex however. Consider the dishwasher again, I would only want that fired up if I had a full load of dishes. So I would need some way of 'enabling' the load so that the PV router would know it is available.

I think we are perhaps getting beyond the realm of an Arduino controller for this sort of thing. This will require more complex automation logic which is responsible for enabling/disabling various loads and potentially even allowing load times to be dynamically set, and then we leave the relatively simple on/off logic you outlined in your post to the PV router. 

I have quite a bit of experience in home automation software, well in one particular piece of software - openHAB (www.openhab.org). I think this would be a perfect fit for this type of control. And I would be very happy to work with you at integrating openHAB with the Mk2 PV router if you think this approach has some merit.

In reality the design will be quite generic, perhaps using MQTT, and then any automation system can be used to interface with the router and enable/disable these continuous loads.

I posted a sizable response to this but got an email saying the post was being reviewed before being shown. That was over 24 hours ago. Has that post been lost or is it still in the 'review queue'?

Yes it was, no it hadn't and yes it was, and I appear to the the only Moderator to have looked at the queue, and I've been out/busy for the last day or two. So don't panic. But thanks for not posting 5 times like some have done.

I've been running many loads successfully for nearly some 2 years including air source heat pumps and battery chargers very successfully with my own modification of the Mk2i code which Robin is well aware of. I have modified the code to run a mixture of anti flicker and normal mode dependent upon the actual load being used. It also prioritizes loads and very rarely does it result in any import from the grid.

summerboy, how do you deal with the electronic controls in most modern dishwashers and washing machines?   After a power-fail, mine "reboots" into a default off state.  I don't think I could set mine up so that it would do its cycle when the mains comes on, I'd need to be there to re-select the cycle etc.

Sumnerboy, if your dishwasher is to be a regular feature of your daily routine, then you should be able to regard it as a continuous load that requires period X of continuous power when criterion Y has been met.  On days when it is full and switched on, it will start up at the appointed time and consume power; otherwise, it won't.

My mother has this kind of system for her dishwasher which she runs overnight on Economy 7.  If the unit is not sufficiently full, then she doesn't switch it on.  So although power is allocated by the 24h timer that's plugged into her mains outlet, no energy is consumed. 

I can't promise any bespoke code for you of this type but would be happy to supply you with some ''Mk2'" hardware to run it on :)

*  *  *

Tinbum, sorry, I can't see any reason for running some loads in normal mode and some in anti flicker.

In anti flicker mode, loads are likely to be cycling at around 0.5Hz (one second on, one second off).  Which of your loads can cope with this kind of treatment yet can't cope with faster rates of cycling?

As I said at the top of this thread, I think loads need to be categorised into two types: those that can be cycled rapidly, such as water heaters; and those that can't, such as battery chargers - or dishwashers.  The latter type I regard as "continuous" loads, and these need to be held on for a minimum duration as you do with your various timers, whatever the weather.

The former type I regard as "conventional" or "general purpose" dump-loads, and they can be used to mop up whatever surplus power is left.  Whether they do so within Normal mode or anti-flicker has no real bearing on anything, IMHO.

If you feel that your code can make a useful contribution to this debate - either in its original form or with my recent additions - please feel free to post it here.

Robin, What practical experience of running different loads do you actually have?

None, but I have plenty of experience of providing kit that others can use for this kind of purpose.  As the supplier of this stuff, both software and now hardware, I need to stay on top of my customers' needs.

What practical experience do you have of running loads than need to be operated in Anti-flicker mode rather than Normal?

Thanks Robert - do posts always get reviewed like this, or just for new users?

dBC - yep that is a valid point. But as Robin pointed out I would just manually schedule the dishwasher for the middle of the day, when it is most likely to have the most PV generation, and then the PV router can decide if there is enough to kick it off. It wouldn't be perfect but by tying in rules which monitor weather forecasts (potentially) we can probably improve things further.

It is for these sorts of reasons that I believe integrating the PV router with some more complex home automation software has a lot of merits.

Robin - my solar is getting installed this week so once it is in and operational I will be figuring out exactly what I need and will most definitely be in touch. I pointed another chap from NZ in your directly recently and he has just posted a picture of a PV router all setup and diverting power. Do I get a commission ;)?! 

What are types of dump loads are people using? Tinbum you mentioned battery chargers - what sort of batteries are you charging? Looking for ideas on how else to divert since my evacuated solar tubes will handle all my hot water during the highly productive summer months!

I seem to have confused myself a little bit in my previous post...apologies!

Due to the electronics in the dishwasher, as dBC pointed out, it would need to remain on and powered up so that the timer can kick in when required and run the dishwasher program. So that means I would have to set the dishwasher timer to run at the same time each day (that it was full and ready), and then have my PV Router configured to check PV generation at that 'run time' and decide whether to let the dishwasher run, or shut it off.

So in effect the router would be turning OFF that continuous load if there was not sufficient generation, rather than turning it ON is there was enough. But this requires synching of the dishwasher timer and the PV router 'generation check'.

This is not ideal as my dishwasher only has a 'delay start' timer (which is by the hour), not a 'run at' timer. So I am not convinced running this type of load using diversion is really all that feasible - unless I am missing something...?

What I really need is a 'connected' dishwasher...something I can 'talk' to over IP and control via openHAB. Then the PV Router can just signal openHAB to indicate there is extra power available and openHAB can decide whether it should run the dishwasher. 

Which goes back to my earlier question...what other types of dump load are people diverting to (since it doesn't really look like I can use my dishwasher)?

"Thanks Robert - do posts always get reviewed like this, or just for new users?" Basically, as I understand it, it is users who haven't built up a reputation. I don't know the details of the algorithm it uses, but I think external links have a big influence, as it's intended as an anti-spammer device. I'm flagging you as a "power user", which means it should not catch you again.

Thanks Robert.

Plenty. For a start my chargers, there is no way to run you can run them in normal mode.

Robert - I posted twice this morning, the first one got held back, the second went thru (and is visible in the thread above). Could you release my first post as there were a few questions in there?

Tinbum - what are you charging? Is it a battery bank for use during non-solar periods? 

Tinbum:  Plenty. For a start my chargers, there is no way to run you can run them in normal mode.

Agreed, but are you saying that you can run your battery chargers in anti-flicker mode?  In that case, they are likely to cycle on & off at approximately 1 Hz which does not sound acceptable to me.  Please can we get some agreement over this before moving on.

If your chargers are not cycling on and off, that's because there is sufficient surplus power on your premises for them to be on all the time.  In which case, they could be run just as well in Normal mode.

I would regard a battery charger as being a "continuous" load for which special rules apply.  This is not the same as anti-flicker mode.

Sumnerboy: I pointed another chap from NZ in your directly recently and he has just posted a picture of a PV router all setup and diverting power. Do I get a commission ;)?!

Er, maybe we should discuss terms offline ...

I dispatched two orders to New Zealand recently and noticed that the addresses had similar postcodes.  Both customers were agreeable to being put in contact with other so I was happy to oblige.

Seems that the Kiwi branch of the Mk2 Users' Club is going from strength to strength - and this is your winter!

Tinbum - what are you charging? Is it a battery bank for use during non-solar periods?

Yes, I have a large battery bank that I use for powering everything when the sun is down so it needs charging every day.

Agreed, but are you saying that you can run your battery chargers in anti-flicker mode? In that case, they are likely to cycle on & off at approximately 1 Hz which does not sound acceptable to me. Please can we get some agreement over this before moving on. If your chargers are not cycling on and off, that's because there is sufficient surplus power on your premises for them to be on all the time. In which case, they could be run just as well in Normal mode. I would regard a battery charger as being a "continuous" load for which special rules apply. This is not the same as anti-flicker mode.

Yes and with no problems at all other than substituting one small component within them. I've been running them for nearly 2 years like this. The chargers running in AF are 1kw each, and yes they cycle on and off as, no, there isn't sufficient power to keep them on all the time. I've also been running them with a meter with a 1000J bucket. As the chargers ramp their output they don't operate at 1Hz. It's taken much very fine tuning but it works perfectly and it doesn't result in import from the grid. 

My sequence is;

load 1 (charger 1) cycles on/off in AF first

once there is 1kW+ of suplus Pv then 1 will therefor be on constantly and charger 2 will cycle on/off in AF

once there is 2kW+ of surplus PV then 1 and  2 will be on constantly and charger 3 will cycle on/off in AF

once there is 3kW+ of surplus PV then 1,2,3 will be on constantly and charger 4 will cycle on/off in AF

once the is 4kW+ of surplus PV charger 4 (3kW) will come on (with timers not in AF) and 2,3,4 will go off

at 4kw+ charger one cycles in AF again and so the sequence continues.

For anyone having a battery bank that has cost £1000's the first priority is to charge them with every single bit of surplus power available. Imagine a really dull rainy day in mid December. You simply can't do that with them as a continuous load.

Which goes back to my earlier question...what other types of dump load are people diverting to (since it doesn't really look like I can use my dishwasher)?

I've modified a tumble drier for use with mine. (Also made it automatically change rotational direction at the same time, that's why someone gave me it as their clothes always ended up in a ball inside)!

Also use an air source heat pump and I am planning on a ground source heat pump for cold days when it  will be more efficient than the ASHP.

tinbum, what sort of batteries are you using.... lead acid, lithium ion etc?  Just about every battery technology benefits (in longevity and charging speed) from various charging algorithms designed for that chemistry.  For example lead acids like a constant current phase, followed by a constant voltage phase, followed by a trickle phase.   How do you manage that while pulsing the supply to the charger?

The batteries are lead acid (Rolls). I work on the principle that its better to be putting something in than not, and they are working in the bulk stage.

It must also be remembered that its only 1kW that is turning on and off. I also have direct DC PV charging to the batteries and with solar charging you are always at the mercy of the sun.

The actual charging is done in 3 stages bulk, absorb and float which are controlled by the MPPT solar DC charger and the charger (Trace) that is number 6 on the diverter. In my scheme above I have slightly simplified it because the actual charger loads will actually reduce as the batteries charge and as more chargers come on.

Once I have the 3 phase meter problems sorted I will be changing my system as I will be installing 3 sunny backups, one on each phase. They will do most of the battery charging along with the DC MPPT charger. There will still be some charging using the Mk2i but from the PV on my other 3 phase supply.  

My sequence is;

load 1 (charger 1) cycles on/off in AF first

once there is 1kW+ of suplus Pv then 1 will therefor be on constantly and charger 2 will cycle on/off in AF

once there is 2kW+ of surplus PV then 1 and  2 will be on constantly and charger 3 will cycle on/off in AF

once there is 3kW+ of surplus PV then 1,2,3 will be on constantly and charger 4 will cycle on/off in AF

So far, this is just how my Mk2i rev5 sketch works.  Only the lowest priority load is cycled (in either Normal or anti-flicker mode as selected), and all higher priority loads remain fully on.  To drive multiple outputs is just a matter of allocating the IO pins for them; the necessary control logic is already within the sketch.

once the is 4kW+ of surplus PV charger 4 (3kW) will come on (with timers not in AF) and 2,3,4 will go off

This is the "continuous load" idea which is the main reason that I started this thread.   As I see it, "continuous" loads become part of the background consumption and therefore play no part in the the primary activity of the Mk2 which is to balance energy consumption against energy generation.

at 4kw+ charger one cycles in AF again and so the sequence continues.

Yes, if there is any surplus power while the "continuous" load is on, it will be diverted to the first available conventional load in whichever mode is selected, either Normal or AF.

As I see it, the extra functionality for "continuous" loads could be incorporated into the latest version of Mk2i rev5 code (rev5e) with very few changes.  It may be best for the RF overhead to be removed, otherwise it all gets rather complicated. 

On the Downloads page of my website, there's a multi-load Mk2 sketch without RF called Mk2_multiLoad_CAT5_2.ino (sorry, the name gets scrambled when the file is downloaded).

Yes, if there is any surplus power while the "continuous" load is on, it will be diverted to the first available conventional load in whichever mode is selected, either Normal or AF.

I can allocate this for any individual load and not as a global setting. So for example my heaters/ immersions etc are in normal mode but chargers in AF.

So far, this is just how my Mk2i rev5 sketch works. Only the lowest priority load is cycled (in either Normal or anti-flicker mode as selected), and all higher priority loads remain fully on. To drive multiple outputs is just a matter of allocating the IO pins for them; the necessary control logic is already within the sketch.

In my code the turning off sequence is much altered from yours. Certain items may have initially been held on by a timer but once that time is up it doesn't mean that load will actually turn off. So what was a low priority load at the beginning may actually become a high priority load. For example you wouldn't want an ASHP on when the PV wasn't going to be good enough to drive it without import, eg first thing in the morning. But when the first few loads are on its probable that the PV has got to a sufficient level to be able to drive it. You then want to continue using that as its COP is greater than 1, which is what an element is. All the time you don't want import though so the original higher priority loads become the low priority and switch on and off so the ASHP remains on.  

As I see it, the extra functionality for "continuous" loads could be incorporated into the latest version of Mk2i rev5 code (rev5e) with very few changes.

The basis is already done, as you'll see in the copy of my sketch that you have.Your description in the first post is basically just how my code works i think.

Re making my code available I'm happy to do, but more on a one to one basis as through the code is not complex using it and setting it up correctly is.

I can allocate this for any individual load and not as a global setting. So for example my heaters/ immersions etc are in normal mode but chargers in AF.

Given that your system is operating in AF mode when supplying surplus power to your battery chargers, I'm really struggling to understand why you might want to use "normal" mode for your heaters/immersions.  Why not stick with AF mode throughout?

In most cases I would think most people will use the Mk2i in normal mode and to be honest I would. Initially with your early versions of the sketch, which mine is based on, it was vital to have very accurate calibration if AF was to be used or there would be import from the grid. (Iv'e not checked your newer AF method yet). My meter had a very small energy bucket, about 1/3 of the 'standard' meter so that became even more vital.

I think having normal mode results in less possibility of import as the energy bucket should be nearer the center and so should a load elsewhere be turned on or the PV reduces theres a bit more left in it for its reaction.   Having it in also just gives greater flexibility, who knows what someone is going to power next!

OK, that makes sense.  In simple terms, "normal" mode is indeed the safer option in which to run a MK2 Router.  However,  once a system has been properly calibrated and found to be working satisfactorily in AF mode, I see no reason to ever revert to normal mode.  The only advantage of  "normal" mode is that the action happens more quickly when minimal surplus power is available.  Otherwise, between the infrequent bursts of power, it could appear that the Router is not actually doing anything.

Iv'e not checked your newer AF method yet

While updating your sketch recently, I replaced the legacy AF logic with that from Mk2i rev5d which forms part of my standard multi-load control mechanism.  This newer algorithm does not have twin energy thresholds; instead, it uses just one threshold (the mid-point of the energy bucket) plus its knowledge about the passing of time.   IMHO, there are some key benefits to this approach, one of which is that the system no longer requires accurate calibration.  The reason for this is that time, unlike energy flow, is already known in absolute terms.

Another advantage of this system is that it works particularly well for smaller loads such as your bank of 1 kW battery chargers.  This is because more time is available when deciding whether a given load will suffice, or whether an additional load needs to be added or removed.  With the original 2-threshold system, nothing happens until one of the thresholds is reached, then decisions need to be made very quickly.  This benefit of the newer algorithm is greatest with smaller loads.  When cycling large (3kW) loads, the two systems having exactly the same timing limitations.

I'll give it a try and see how it compares!

We all enjoyed some fun discussing this sort of thing here last year.

Clearly storing surplus PV energy is proving very successful when heating water for later domestic use. The big advantage in doing this is that we are using existing infrastructure.

A more radical idea might be to design a very high temperature heat storage device like an old fashioned brick bread oven but using modern highly efficient insulating materials. So when you want to cook that pizza just open the door and pop it in. No need to switch it on.

It would bring back the need for skill in cooking - no gas mark 6 simplicity here!

Brian

The beauty of using water to store the heat is there is nothing better in terms the quantity of heat in a given volume and convenience. Most of the time it is easy to handle and you can use the heat without needing to transfer it to something else.

Hydrogen has a rather higher Specific Heat Capacity but it needs a large volume to get the same weight and it can be unforgiving if you handle it wrongly.  Helium is a little less bad but still hardly convenient.

Anyone else noticed that a really big techy guy in the states has leveraged his car batteries into his PV storage marketplace?

This battery is very interesting http://www.aquionenergy.com/

Local storage has reached grid parity.

Interesting... When I read "a really big techy guy in the states has leveraged his car batteries into his PV storage marketplace" I immediately thought of: www.teslamotors.com/powerwall

One of the first things I noticed about the Aquion site was no pricing. In general I've noticed that when a price isn't listed on a page, it's usually pretty steep.

Bill, you are correct, I was referring to the Tesla Powerwall, If I could only buy them in bulk. They have limited availability unless you were able to pre-buy a unit. I mentioned the Aquion battery because it looks very interesting compared to lead-acid or lithium-ion. Aquion is local to me so I am hoping to pay them a visit. I have a tremendous need to divert energy to batteries or water heating loads due to changes in the net-metering policies where I do business.

I'd love to have a few of their 10 kWh units myself! I'm hoping they get their plant built on time, and are able to ramp up production quickly. Maybe they'll drop in price once Tesla sells enough of them to recover the R&D costs.

Phase change storage materials probably offer some promise depending on application. Lithium Nitrate looks promising for storing heat for cooking.

Hi all, new to the forum, I am an active contributor on various ev forums I am registered on.

My position is coming from a lithium battery view. I have been using lifepo4 lithium for about 2 years in a Toyota Prius that I converted into a plug in Prius by fitting in controls systems and a 7.5 kWh lifepo4 battery.

there is no charge curve or profile charge requirements for lifepo4 lithium, just charge at constant current until the charger output voltage matches the battery pack voltage, at this point no current flows and the battery is full.

in practice though, I run my packs alittle lower in total pack voltage, I also allow at least 10% capacity at full and low charge limits only using at the most 80% of the battery capacity, this will prolong the battery life. I have run my plug in Prius and covered about 10000 miles mostly in ev mode and seen very little to no degradation in the battery capacity.

so, could this be termed a standard load, as there is no special charging requirement? ( for lithium only)

also, in relation to batteries, Nissan Leaf vehicles are starting to show up in salvage yards, they are sought after by ev enthusiasts but I'm sure a steady stream of supply will be available within a couple of years, these batteries at 24kwh capacity (I'd only use 20kwh max though to extend life) are great for projects with energy storage. I managed to pick up a battery myself 2 moths ago, 16kwh is now in use in my Prius, the other 8kwh and the older Prius 7.5kwh  lifepo4 is going to make up my battery store for energy storage.

I'm Looking for a pv excess diverted to divert excess pv electricity into heat store then battery store plus the plug in Prius, more complicated than a standard set up but I'm sure is a do able project

thanks. Anthony.

An Everhot electric range cooker might fit your culinary bill!