Smart-grid application of OTGW

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Smart-grid application of OTGW

Postby Albertwaninge » Tue Dec 13, 2016 8:28 am

For my new to build passive house I am looking for a way to optimize the use of my home-made solar energy. The passiv house will have to rely on electricity for heating, as there is no gas. As the expected heating demand will be no more than 3GJ/year, all kind of high-tech heat exchangers are severly overdimensioned. Heating will be done via low temperature wall heating on three walls.

If I am correct, regulating the circulation of the heat from a reservoir/boiler over the building is standard procedure with OpenTherm. Yet, to make my system smart, I have an extra requirement for the boiler. I want the boiler (with a reservoir of approx. 400 liters) to heat the water when the solar panels are producing more energy than is being consumed by other devices at that moment. Ideally, the domotica server can regulate the power with which the boiler heats the water. That is, when production is, for instance, 250W more than consumption, the boiler heats with 250W. If production surplus is 2,5kW,m the boiler heats with 2,5kW. Only when temperature drops below, say 35°C, 'external' electricity is being used.

I have not been able to find a boiler or heating system which allows me to do this. Is there anyone who has experience with similar installations?
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Re: Smart-grid application of OTGW

Postby vincenttor » Thu Dec 15, 2016 10:09 am

build it yourself with reading the output from your solar panels and the usage at that moment.
If you have a bigger output at that moment then youre usage, switch on a electrical heating element in your tank.
let it switch of when the sun is lower or the usage in the house goes up.

To limit the heating element to the amount of produced energy, i would try to find a 0-10v accepting dimmable psu if that is possible with a heating element.
Then control the 0-10v with a arduino , i mean the output.

make events with limits for example the arduino sets the dimmable psu to 4.5 V , this results in a usage of the electrial element off 300W.

so the event would be something like, if usage is below 100 w and the panels produce between range 300-400 then set heatingelement output 4,5V


that is if i understand correct what you are planning to do.
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Re: Smart-grid application of OTGW

Postby hvxl » Sun Dec 18, 2016 9:31 pm

Via opentherm you can control when water in the boiler is heated. But that's just an on/off type of control. I am not aware of a way to specify how much power may be used to heat the water.
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Re: Smart-grid application of OTGW

Postby Albertwaninge » Mon Dec 19, 2016 5:32 pm

@hvxl, good to know that at least regulating the timing of the heating is an option.

@Vincenttor, that is indeed what I am planning to do. But I would like to know which boilers (brand and model) support such power regulation.
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Re: Smart-grid application of OTGW

Postby marcelr » Mon Dec 19, 2016 10:31 pm

What you talk about sounds very much like a laboratory heating unit, like these ones:
http://www.julabo.com/en/products/heating-circulators

(I have a lot of these units in my lab, for all kinds of purposes).

AFAIK heaters like this are always controlled with an on-off controller, since continuous power regulation of typically 2kW heating elements is quite expensive in terms of power electronics, and not necessary to get a proper temperature regulation. External control of these devices with some sort of computer or micro-controller is easy. In general the buffer to store the heat (typically a reservoir of 20+ Litres) is big enough to attenuate temperature fluctuations induced by the switching heat source. The more expensive types come with a cooler as well, and can maintain temperatures to an accuracy of +- 0.01 deg C, with on-off control only (and a sophisticated control algorithm).

Long story short: it will be hard to find a ready-to-use heater with continuous power control, because for even high-accuracy applications, on-off control is good enough.

There is however, the possibility of AC phase chopper control, in which only part of the sine wave of the current is actually used. This should enable continuous power control. Not sure if these are readily available for 2kW+ power levels.

HTH,

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Re: Smart-grid application of OTGW

Postby vincenttor » Mon Dec 19, 2016 11:00 pm

it seems like i thought, it is probably working with a simple dimmer.

homebrewtalk.com/showthread.php?t=16640 ... amp;page=4

you need a triac dimmer i read on some sites , but also read about a pwm dimmer.
pay attention to the amount of power the dimmer can handle.

The potentiometer you can try to control with an arduino or any other controller,
not sure how to but it should be possible to control from a home automation program
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