Controlling appliances

[Kombi]

Hello all,

I am having my PV system installed on Monday. In order to make the most of it I am wondering if there is a way in which I can get some appliances (such as immersion heater for example) to switch on when the array is producing enough ? Obviously there would need to be some degree of clever control to avoid permanent on/off on some days but in principle in this possible?

Nicolas

[wookey]

Yes, switch them on when it is sunny :-) Works for washing machine, dishwasher particularly. Very advanaced control system.y

[ecogeorge]

Stick freezers on a time clock so they only run in daylight production time. The better the energy efficiency (insulation) the less freezer temp fluctuation you will see in 24 hrs
Has your washing machine or dishwasher got a timer ? -use that also.
Cook with a slo-cooker during the day.
Do you heat DHW with electric? -shame on you if you do! -put the immersion on a timer but i doubt you'll have 3kw of pv electric spare!
Basically run what you can during daylight only.
rgds George.

[Kombi]

Thanks Wookey... But what do I do when I am away? Quickly run back??

George, not a bad idea the timer for the freezer except it would put internal light off. But well worth considering. Both Fridge Freezer are A+ rated.
The washing machine has a timer, so has the dishwasher so I do indeed plan to run them during the day.
I currently do not heat the DHW with an immersion heater but there is one fitted so the idea is to make the most of the electricity I will be producing as at 3p/kWh exported it is not going to get me rich quickly....

[KenB]

Kombi,

You could use an internet controlled socket.

Turn it on/off from anywhere on the planet, or even by your mobile phone. 

Just need to keep your wireless router powered 24/7.



Ken

[Alan]

Very Dooo able so that every bit of power generated and not used in the house is diverted to the immersion heater or storage heater


You will need two current transformers.

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0351106

One

http://www.united-automation.com/_ProductDetail.phuse?PhuseAction=PyrUUhn1O8sELPSFzFKQvF2fptvIHFGbmMb4An06h9CTdmMLrle8uqrtGZI6eaYm

http://www.united-automation.com/res/media/pdf/X10532EVR25A_Bpdf.pdf

This will give up to 6 K.W. proportional out put in relation to a 0 to 5 volt opto isolated input.



And a programmed PIC Micro.



http://steamboilers.homecall.co.uk/EXP1.JPG

Not been doing much PIC stuff, they may do a pic with a D to A out put. The soldering side is very straight forward. If you want liquid crystal displays and bar graphs a bit more soldering is required.

Here I have been doing it with pulse width modulation and never quite got round to the opto isolation from the mains, still on the to Dooo one day list.

The code is pretty basic, If Navitron / Ken want to market some thing I can get involved, but I don’t seem to get much time to make my wish list smaller.

Regards

Alan

[Kombi]

Thanks Alan,

this looks very interesting. Is there a ready version for complete dummies like me? And what's a PIC micro? I know absolutelky nothing on this side and my soldering skills are best left deep into the attic...

Nicolas

[Outtasight]

For those of the embedded software challenged nature, you can try using an old laptop and a Velleman USB I/O module from Maplins.

I'm controlling my 3kW immersion heater via one of these, reading the power generated from the PV array from the charge controllers, the battery voltage, the charge mode and the brightness of the sun by a home made lux meter.  The aim is very similar in that I want to make use of all the excess solar power from the array when the battery is full while not discharging the battery if a cloud passes overhead or a bunch of other loads like the kettle turn on.

Works well.  Yesterday I managed to consume 5kWh of solar power and still have a full battery at sunset plus a full tank of hot water!

It does require being able to program in C (using a free compiler called CH) or if you've got an old copy of Visual Basic or Borland Delphi it's a complete doddle to program.

See more here:

http://www.navitron.org.uk/forum/index.php/topic,8368.120.html

The module comes with a DLL that provides a simple set of commands to read 4 input switches (e.g. thermostats), read 2 A/D converters (for my lux meter), and output either 8 on/off ports that can directly drive relays or two D/A ports that do either 0-5V analogue or PWM output.

No soldering required (unless you want to save £10 and build the kit version).

It's even USB powered (although you do need an external power supply to drive a relay).

To do Alan's scheme you'd just have to feed the induction coil outputs to the Velleman A/D converters, fiddle with the values of the buffer amp gain resistors to get a decent reading. Then you simply use the PC program to decide when to turn on one or more of the 8 loads you can control or pulse them slowly by software or use the PWM or analogue outputs to "dim" one big load like a heater using the triac chopper he used.

I've used the 7 spare outputs on the board (each has a LED) to make a bar graph for the lux meter so that I can see when it's getting bright enough that the heater might start to come on.

[InertiaM]

I'm really interested in all the replies so far.  Just starting to head down a solar PV route, and want to make sure I consume as much as possible in the most efficient way.  Have been programming PLCs for the last X years (X being a number between many and too many), and always wanted to 'control' our house!  I now have the perfect excuse    I expect I'll use a networked PLC to do the control, and just create a PC program to display the information.

It does require being able to program in C (using a free compiler called CH) or if you've got an old copy of Visual Basic or Borland Delphi it's a complete doddle to program.

I have a genuine copy of VB6 if anyone wants it.  Send me a PM.

[ericw]

If you just want to switch things on or off you can simplify things by utilising the fact that the direction of the current in a single current transformer on the supply cable will reverse as you go from supplying current to absorbing current.
So its then a matter of sensing the magnitude of the output during one of the mains half cycles (pick up a phase reference with a wire wrapped around the input cable)  this can be done with a simple microprocessor (eg PIC) without additional circuitry. This can then drive the power switching arrangement either as a pulse width for phase type control or a counter output to drive binary weighted load switches.

[Kombi]

Thanks for all your replies. I need to try to absorb the info (including Outtasight's link)before doing anything else but it very much looks like all of this is way beyond my meagre capabilities... Some of you ought to consider offering all inclusive package... I like the idea of charging a battery bank to have power when the PV stop producing but with a 3.85kW array I think I might need a garage full of batteries. Daily consumption varies between 9 and 12kWh/day. If I add the cost of the batteries, plus charger, controller and the rest, is it worth going down this route?

[Baz]

The real problem here is that not all, well in reality 99% of people, can't make pcbs and program micros, or even laptops so what they need is a simple box that does the business.
In other areas this is recognised so specialised charge controllers etc exist.

Here there seems to be an opportunity for a small business to make a box of tricks that measures the current and has a few relay controlled mains sockets that are switched on depending on the current available - say 100W, 500W, 1Kw.

On the techie side this doesn't even need a computer, just a few comparators.

If you are running a whole PC to do these things have a look at 'Misterhouse' a free home control program that does just about anything.

[Baz]

BTW don't try to run a 6kw load off a PV array using a switched mode controller without a battery bank thinking it will balance when say only 1kw is avalable. During the off phase no power is drawn so energy is wasted, during on phase it's massively overloaded so probably rather unhappy.

Also no sense in running a 3kw heater during the day with a grid tie when you only have 1kw available. 2/3 of the power is coming at daytime grid rates so you would be better waiting to nightime rate taking all the power at half the rate.

[Alan]

Proportional control is the way to go.  I need to calibrate the current transformer to the 0 to 5 volt control for the triac. On the list to Dooo one day, but not far out.

I only had one day over Easter to play.

Generated    16.4 K.W.
Imported    1 K.W
Export       1.7 K.W

420 ltrs water at 61 Deg C and no heat required for under floor system.

That made other problems with pumps running in the night to transfer  / dissipate heat. The to doo list gets longer.


Don’t use Efergy type clamp meters for displaying pulse width modulation or triac control. They get very confused. You need to take a step back in time and have an amp meter with a moving needle.

Stepped loads will always waste power.

Regards

Alan

[EccentricAnomaly]

BTW don't try to run a 6kw load off a PV array using a switched mode controller without a battery bank thinking it will balance when say only 1kw is avalable. During the off phase no power is drawn so energy is wasted, during on phase it's massively overloaded so probably rather unhappy.

Doesn't that depend on the switch mode controller?  Anything decent ought to be smoothing the input current, if only to prevent RF interference, I'd have thought.