Solar Panel immersion heater automatic switch.

[Digon]

Hi Digon

Thanks for your update, I am glad you have a good working system. I have been thinking of a fully proportional system but have only found a schematic without any other information on type of current transformers (CT's) set up etc.

Can you list all the parts you used please, so anyone else interested can also build one. And any useful information on the build process would be helpful

My problem is I can't get my head round the fully proportional concept. If you have two CT's measuring solar and house load, then as soon as you have more solar than house load you start to divert surplus to the immersion heater, but as soon as you do, the house load rises and you no longer have any surplus to detect. So how do you then maintain power to the immersion when both CT's are reading the same power levels?

Regards Trader9.

I can't give specifics on the design because it's not my design. But there is another thread on here 40 odd pages long and a few guys on there have designed proportional systems. I pm'd one of the guys and he was extremely helpful getting this built and faultfinding. I know the designer is putting it through CE testing so I think he may be going to sell ready built diverters so won't want his circuit design made public however he may still share the design for personal use if you pm him.
It uses a single ct and can tell which way the current is flowing without having to cancel out the solar from the feed and sends a control signal to the crydom which does all the high voltage work.

 

[loskie]

we're planning to install a small area of Electric underfloor heating to a new bathroom. Will be about 4m2 so will need a consumption of 600w. As there are only us two in the household and we are out for a large prportion of the day I wonder if this type of switch would enable us to use surplus electricity from our 3.6kwp solar pv. I realise that the surplus is not ging to be there exactly when we need it and probably inadequate from Nov to mid March but feel this would be good for us. Also keep the bathroom heated and therefore drier.
Could a similar switch be used for UFH?

 

[MichaelB]

I found this which seems to do the job simply and cheaply www.mgb-stuff.org.uk/solar.htm without all the bells and whistles that EMA and Sunny Boy seem to think necessary.

 

[Scobo]

I found this which seems to do the job simply and cheaply www.mgb-stuff.org.uk/solar.htm without all the bells and whistles that EMA and Sunny Boy seem to think necessary.

Sounds interesting but couldn't see how much it costs. :confused5:

 

[Trader9]

Hi Digon
Thank you for your reply. I will go and read the 40 pages before I decide which way to go.

Regards Trader9

 

[st3ve]

...If this was sucessful I could quite easily change the plumbing to give the option of hot filling the washing machine to save a bit more.

FYI: Many have discussed this I believe, seems like a good idea, but the practicality is that the 'hot plumbed' washing machine / dishwasher will take in the mostly the cold standing water in the pipes leading from your heat store unless the pipes are very well lagged and 'washer is very close to the heatstore - probably unlikely.

Also, consider that for a dishwasher, the rinse cycle would be using hot water which may well bake on the chilli/egg/pasta etc!

 

[Digon]

Attached are a couple of graphs which give an example of how much variation in the amount of power my system was sending to the immersion at two different times of day on a mediocre day.

 

[steve Leese]

There is a very good product on the market called the solar iboost, its produced by Marlec engineering. it dumps your spare pv power to the emursion heater. i saw it at the ecobuild.

 

[madmurg]

There is an interesting thread at the
Solar Energy Management | OpenEnergyMonitor

http://openenergymonitor.org/emon/node/176?page=2
It looks like someone has built a fully controllable solar controller useing zero cross and burst firing. This removes the need to use expensive crydom or phase angle controllers, which cost £70 plus. So you should be able to build yourself a unit for under £50.

 

[solarcat]

There's a system called Greenologic which seems quite good to me, although I've had no luck getting any prices so far. Essentially it's a series of boxes, one reads the generation meter, an you can have one for your immersion water tank and one for each storage heater...when you start exporting the first box sends a wireless signal to the others and asks them to switch their storage devices on...

 

[RS-232]

There is an interesting thread at the
Solar Energy Management | OpenEnergyMonitor


The "OpenEnergyMonitor" thread is a bit too technical for me, with only a basic electrical knowledge, even though it might offer a solution to dumping excess solar power into an immersion heater.

I'd guess that for most of the time, there will not be enough power from say, a 4kW PV system to feed a 3kW immersion heater as well as all the other gadgets in the house, so some have suggested replacing a 3kW element with a 1kW element. The drawback with this is that it won't be much use if you need a supply of hot water quickly.

As a simple alternative, can anyone see a problem with using a dual-element immersion heater, with the 3kW elements operated individually for rapid heating and in series when powered by the PV system? If my maths is correct, this should give an effective load of 1.5kW, which is much more likely to fall within the PV system output.

I suppose the heater could be wired to some sort of relay, using a change over switch to select the mode of operation.

 

[Trader9]

Hi RS-232

I have two 3kW heaters in my tank so I use a 3.3kVA isolation transformer with the centre tap earth removed so I have use of 55V and 110V. I then use relays to switch between the two voltages to give me five different loads 160W, 320W 660W 820W and 1.320W. This works well and I have hot water by midday. I use a single Arduino to monitor the solar and house load and do the switching. Since January I have averaged 24% (272kWh) of all generation into hot water that would have gone back to the grid as surplus.

Regards, Trader9

 

[RS-232]

An interesting set-up Trader9, but controlling such a system electronically would be beyond my capabilities! When you say that you have two 3kW heaters, are they combined, as in a dual-element heater, or are they separate units? Also, suppose that you need to heat your water quickly - can you run one or the other heater from 240V (i.e. 3kW)?

 

[Trader9]

Hi RS-232

They are the normal 3kW immersion and the 3kW boost both wired separately. I could wire them in series but I normally rely on off peak heating overnight and then solar all day, so off peak is reduced. Also I don't suppose that 1.5kW will be available that often in the winter. I can always use the boost to heat water if needed.

Come the summer (if ever it stops raining) I hope to switch off the off-peak and run solar only. Did actually manage it for the last week of April when it was like summer. You do need a system that cuts in at a low wattage so you can use it in the winter.

The Arduino is only £22 and you would need two efergy sensors (CT's) four resistors and a capacitor for the sensor interface. I am working on a simpler version using the Arduino directly driving a solid state relay (SSR) and this could be a simple solution, but I am still waiting for the SSR from Hong Kong but all in would be a simple cheap solution if it works. About £70.00

Hell, if I am sixty-four years old and using microprocessors, SSR, Ct's and LED's then it can't be that difficult. I will keep you posted on how my new system progresses.

Regards, Trader9.

 

[madmurg]

There is an interesting thread at the
Solar Energy Management | OpenEnergyMonitor


The "OpenEnergyMonitor" thread is a bit too technical for me, with only a basic electrical knowledge, even though it might offer a solution to dumping excess solar power into an immersion heater.

I'd guess that for most of the time, there will not be enough power from say, a 4kW PV system to feed a 3kW immersion heater as well as all the other gadgets in the house, so some have suggested replacing a 3kW element with a 1kW element. The drawback with this is that it won't be much use if you need a supply of hot water quickly.

As a simple alternative, can anyone see a problem with using a dual-element immersion heater, with the 3kW elements operated individually for rapid heating and in series when powered by the PV system? If my maths is correct, this should give an effective load of 1.5kW, which is much more likely to fall within the PV system output.

I suppose the heater could be wired to some sort of relay, using a change over switch to select the mode of operation.

I too thought it would be difficult to achieve but after a week or 2 browsing the Internet forums I managed to build my own controller and it works great. It really is very easy.
you do not need high wattage from your solar panels as my system heats a full tank of water using just 400w of spare power, a 3kw element will work fine using low wattage. There is no need to change to a 1kw element.

 

[thushar]

There is an interesting thread at the
Solar Energy Management | OpenEnergyMonitor

Solar Energy Management | OpenEnergyMonitor
It looks like someone has built a fully controllable solar controller useing zero cross and burst firing. This removes the need to use expensive crydom or phase angle controllers, which cost £70 plus. So you should be able to build yourself a unit for under £50.

That sounds great.

Do you mean the power controller based solution from kemo electronic? I'm struggling to find the actual circuit or component relates to zero cross & burst firing.Could you please help with a schematic or part no or a link please ?

 

[mitul007]

hi guys you should try SOLAR24 from Engensa ltd. it works really well.

 

[madmurg]

hi guys you should try SOLAR24 from Engensa ltd. it works really well.

Not at £250

 

[echase]

Not at £250

People think they can make something similar for a lot less but the reality is often that after few false starts they have a box full of discarded or blown up parts that, together with the parts that do make their way into a working product, end up costing at least £250. So it is fun designing something yourself but often no cheaper.

Or you design something really simple and cheap that does not cost effectively heat much water.

 

[immerse]

What do you use in the way of an EMI filter? Outfits like EMMA, not to mention the DNOs, are very concerned about EMC, and I wouldn't want to ruin my computer!