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Author Topic: excess power from pv  (Read 34582 times)
Other-Power
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« Reply #45 on: July 04, 2011, 01:28:14 PM »

I reckon that 3-phase immersion heater has got to be the best way to soak up the excess energy.

The Emma thing looks like a fantastic bit of kit, but it canna change the laws of physics captain. If it's feeding a 3KW immersion heater and it's only got (say) 1KW of excess energy to play with, it's either got to draw the other 2KW from the grid or reduce the output voltage to get the current and thus the power to stay at the 1KW level.


The EMMA unit modulates its output, it dose not work as you have explained.

Cheers

Jon
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My advice is based on me spending my money doing this and my job spending others money doing this.
MikeD
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« Reply #46 on: July 04, 2011, 05:52:40 PM »

Modulates it how ?

We talking PWM here or what ?

The spec suggests a current limiting device, in which case it effectively drops the output voltage to achieve the desired current. I'm not saying that's a bad thing BTW, quite the opposite. It's a very elegant solution.
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hernibles
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« Reply #47 on: July 04, 2011, 09:06:19 PM »

I have just had a pv system installed. (18 x 220 sharp panels, sunny boy 4000TL).
I am very happy with the performance and output. (145kwh in a week)
I know it is early days but i seem to have excess of power not being used by myself, and obviously being given back to the grid at a low return.
I would like to try and use this power to heat up my hot water tank.
I have done some searches on the net, and this has already been looked at an implemented using a microprocessor to ensure that that you are only using the excess power.
Does anybody have any thoughts or ideas?

thanks
jonboy


You really don't need to look further than the Navitron forums for an elegant solution.

Check out http://tinyurl.com/6dwps8e .  I made one inspired by that thread and it works. 

THE key component is the Unted Automation load controller.


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billi
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« Reply #48 on: July 04, 2011, 09:52:16 PM »

come one   people , what is  excellent about a device that burns all the power  (one get FIT payment for)  into hot water ?  Feed the grid as well !


Billi
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Alan
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« Reply #49 on: July 04, 2011, 10:48:09 PM »

Quote from Billi. come one   people , what is  excellent about a device that burns all the power  (one get FIT payment for)  into hot water ?  Feed the grid as well ! 

Basic sums Billi. What you produce you use. Like off grid. Very efficient way of using energy.
100 % ( Battery losses not included. )   extrahappy

If you use the grid to power your immersion.

Power from a coal fired power station. Typical efficiency 31 38%   facepalm

Power lost in the grid typically 7%   facepalm

Here power also goes to a heat pump with variable speed drive. Only thing to be careful about is keeping the speed fast enough to splash lubricate the crankcase bearings.


Regards

Alan
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john999boy
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« Reply #50 on: July 05, 2011, 02:03:27 AM »

come one   people , what is  excellent about a device that burns all the power  (one get FIT payment for)  into hot water ?  Feed the grid as well !
I agree with Alan billi.
I'd rather had something keeping my water up to temperature than have to pay to do the same via importing. After all, the immersion will also cut off at the required temperature so EMMA will then feed back to the grid anyway.
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billi
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« Reply #51 on: July 05, 2011, 07:42:17 AM »

Sure ,

But if FIT payments result in an increase (wasteful) of personal consumption  , than the system is wrong ....

Using an immersion as the heating idea for hot water  is wasteful  in my eyes  at the current situation

Where is the space in my garden for a swimming pool to dump my units  hysteria


Quote
If you use the grid to power your immersion.

Power from a coal fired power station. Typical efficiency 31 38%   facepalm

But if you export your unit into the grid  another person in the country uses  your unit with a heatpump  .... what is that efficiency than ?  200-400 %   ?

To buy a thing like Emma for  a couple of thousand euro to  increase my immersion heater runtime , buys me other things more usefull   for example a 1-2 kw off grid PV with Inverter and battery  and spread my grid independency  more towards 24 hours a day  whistlie


Billi
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brackwell
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« Reply #52 on: July 05, 2011, 08:42:00 AM »

If this immersion heater is displacing gas heating then perhaps Billi is correct but otherwise the others are.

 Using a heat pump is perhaps a good idea but in my book the best is charging the electric car - no export,no petrol and pollution,use the batteries to run the house when the sun goes down, use night elec as/if necessary . This way the return on your few pence has become perhaps 10X

Ken
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billt
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« Reply #53 on: July 05, 2011, 08:49:30 AM »

I agree with you Billi. Changing the time that you do your washing to a time when your PV is producing is one thing, as that energy would be used anyway. Gaming the system for what seem to be totally selfish reasons (not giving power away to anyone else, basically; power that has already been paid for handsomely) is not very edifying.
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Alan
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« Reply #54 on: July 05, 2011, 09:10:06 AM »


Reality check needed.

Quote Where is the space in my garden for a swimming pool to dump my units    hysteria

Quote Gaming the system for what seem to be totally selfish reasons (not giving power away to anyone else, basically; power that has already been paid for handsomely) is not very edifying.  hysteria

Don't Do swimming pools.
Water tank has a thermostat on the immersion.
Tank gets hot.
Thermostat turns power off. Excess above house load gets exported to the grid.

Regards

Alan
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MikeD
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« Reply #55 on: July 05, 2011, 09:56:31 AM »

Given that you are going to heat the water anyway, it makes good sense to use your locally generated electricity to do it. As Alan says, once the water is hot any further excess power goes back to the grid anyway, all you're doing is avoiding a pointless and expensive export/import cycle.

Having said that, the idea of spending thousands of pounds on a bit of kit to make it happen looks distinctly iffy to me. The trick is to do it cheaply.
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billi
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« Reply #56 on: July 05, 2011, 10:44:54 AM »

I just got a quote for a heatpump  similar like the ecocent but 300 l stainless steel  boiler tank with heatexchanger for solar or wood   delivered to my door from Germany to Ireland  for 1600 Euro  uses uses 0.7 kw   

Just put that on a timer and let it run during the day    and you still have  some money left compared to the EMMA  to buy 1 kw more PV   hysteria
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Richard Owen
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« Reply #57 on: July 05, 2011, 12:36:13 PM »

I just got a quote for a heatpump  similar like the ecocent but 300 l stainless steel  boiler tank with heatexchanger for solar or wood   delivered to my door from Germany to Ireland  for 1600 Euro  uses uses 0.7 kw   


Details please
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billi
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« Reply #58 on: July 05, 2011, 12:45:57 PM »

http://www.wm-feinwerk.de/water/

1620 Euro  excl.vat
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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
Richard Owen
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« Reply #59 on: July 05, 2011, 12:59:54 PM »

Thank you.
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44 Yingli 230Wp panels feeding into 2x Solar Edge SE5000 inverters.
20x 58mm SE, 20x 58mm SW, Solar Thermal feeding 320l thermal store.
10kW heat pump.
300W of Hydro Power.
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