German forum about plant engineering for home: heating system, solar energy, etc ?

131 posts in this topic

Do whatever you want, it's your roof. The PV Forum guys calculate stuff down to 3 decimal places 20 years in the future. They are all over the pros and cons of PV. The general consensus is that a heat pump (assuming UFH) is an absolute no-brainer if you have a south facing PV, especially on a steep roof and have a house that wasn't built in the stone age. I never called your data into question. Why would I? You are assuming that your data transfers to everyone else. That's your mistake really. You are asking me to believe you and disregard the opinions of many well regarded "experts" on the PV forum. 

 

You claimed that anything over 10kWp was a financial error. That's an outrageous claim to make and can be easily shown to be with a simple thought experiment:

If a PV system cost €1 per kWp to install, would I limit myself to a 10kWp or fill the roof(s) available to me?

 

The answer to the above will obviously be to fill the roof with a cheap system, so at some point the cost per kWp will tip the balance in this particular calculation. Generally more kWp -> lower price per kWp because the fixed costs remain the same.

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The only advice I can offer is don't install roof solar panels high enough for birds to get under them and nest. My step-son's neighbor had his professionally installed and is now infested with pigeons. This is far out in the countryside in a relatively new housing development.

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@murphaph

can you please point to data that lead to your opinion?

 

59 minutes ago, murphaph said:

If a PV system cost €1 per kWp to install, would I limit myself to a 10kWp or fill the roof(s) available to me?

once again:

because the strom from a medium is used mainly by you, and this is very attractive financially. The much strom produced by a large system is mainly sold to the grid, which is much less attractive financially.

 

1 hour ago, murphaph said:

I never called your data into question.

Fine. What I am questioning instead is that your opinion is based on data (is it?) that I would like to see and you have not yet shown. Please point us to it. It could well be I review the situation.

 

 

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Yeah a larger system means more export to the grid (mostly in summer) BUT it also means a higher percentage of self produced electricity being used, because in winter a larger array can capture more energy than a smaller one. That's the crux of the matter. And storage tech is not staying static. With a heat pump and concrete screed floors, you already have a rudimentary "battery". We can pump heat into our basement especially and it acts as a great thermal store (all solid concrete walls and ceiling) during the day, to be released at night when the sun stops shining and the heat pump is off. With air source heat pumps you can run them when the sun is shining for maximum energy transfer from the warmer air, using the electricity generated from the sun. But with a small system this will not work in winter.

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10 minutes ago, murphaph said:

Yeah a larger system means more export to the grid (mostly in summer) BUT it also means a higher percentage of self produced electricity being used

No. The larger the PV, the lower the percentage of the PV-electricity used by the household. This regardless of WP or not.

If midday I cook with 1kW, and my PV produces 1kW, I use 100%.

But if the PV produces 10kW and I still need only 1kW, I use 10% and the other 90% goes to the grid.

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Just now, Gambatte said:

No. The larger the PV, the lower the percentage of the PV-electricity used by the household. This regardless of WP or not.

Arrrgh. That's not what I said. Are you not a native English speaker maybe?

 

What you think I said "it also means a higher percentage of the self produced electricity being used"

What I actually said: "it also means a higher percentage of self produced electricity being used"

 

 

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South roof 35 degree no tree but Doppelhaus (my calculations says 55 sqm netto from Dachfenster and chimney shadow). 

Apart the size is that optimal for pv, right? 

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That's too big an investment for anyone here to give you a serious answer on based on such little information. I suggest signing up to PV Forum and using PVGIS to establish your likely harvest. On the face of it good conditions for PV.

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1 hour ago, murphaph said:

That's too big an investment for anyone here to give you a serious answer on based on such little information. I suggest signing up to PV Forum and using PVGIS to establish your likely harvest. On the face of it good conditions for PV.

 

of course I did not want a "serious" answer and I will contact a HB for this. It was just simplechatting with people that I see have already a PV on their roof :) 

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I'm also looking to pick the brains of all the experts out there. I've read most of the thread, but haven't found anything that might be especially helpful to my particular situation.

 

We have an old, but still functioning gas boiler (heating and hot water) and we use our Kacheloffen to heat our downstairs living areas a lot in winter. Important to know is that we live in an old, free-standing, pretty badly insulated, timber-framed house with a shindle facade! I don't believe that we can do much to radically improve the insulation of the house without spending an absolute fortune and changing the essential character of the place.

 

My understanding is that heat pumps are pretty pointless if you can't improve insulation and/or put in or combine with, a floor heating system.  I'm right, aren't I?

 

I am however wondering if installing a new wood heater would help (or a second more modern version upstairs) and if there's a way of combining the existing wood heater with ...???...the existing gas heating system???

 

Any bright ideas much appreciated!

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On 12.4.2022, 18:52:45, Aussiedog said:

if there's a way of combining the existing wood heater with ...???...the existing gas heating system???

One thing that came up in my research was the possibility to have a wood burning oven with a water reservoir which is attached to the existing heating system thus supplementing the heating of the water tank which circulates through the radiators. 

I have no idea if this is efficient, expensive, sensible etc. but I think it might be worth looking into in more detail. 

 

Wasserführender Kaminofen | Holzofen mit Wassertasche (hark.de)

This is a manufacturer's website so probably quite biased and heavy on the marketing, but a decent starting point. The terminology to search for is, apparently: Holzofen/Kamin mit Wassertasche 

 

Here is the deepl translation of the intro on the website: 

WATER-BEARING STOVE
Thanks to good insulation and efficient extraction and use of heating energy, modern houses require less and less energy. Nevertheless, there is still room for improvement. Legislation requires that at least part of the required energy comes from renewable sources. This can be obtained, for example, by means of solar thermal energy, ground-source or air-source heat pumps, or gas condensing boilers. In addition, a water-bearing stove is becoming increasingly common in the plans of house builders and homeowners.

Such a stove with a water pocket is integrated into the existing or planned heating system and can also be used in combination with a solar system, for example. About two-thirds of its combustion heat is used to heat water, which is then fed into a buffer tank for domestic and heating water. In this way, the heat produced can be felt not only in the room where it is installed, but can be used throughout the house.

EFFICIENT WOOD-BURNING STOVES WITH WATER SUPPLY
Our wood-burning stoves with water supply not only impress with their efficient technology and high cost-effectiveness, but also set visual accents. Especially when it comes to the design of the cladding of your water-bearing stove, you can choose from numerous options. Thus, depending on the model, you can choose from various materials such as soapstone and ceramic stove tiles. The tiles are handmade in Germany and are available in many different colors as well as subtle black or white.

In addition, we also offer a pellet stove water-bearing, which works on the same principle as a water-bearing stove. Instead of logs, however, it burns pressed pellets of untreated wood residues (e.g. sawdust or wood shavings).

STOVE WITH WATER POCKET - MODE OF OPERATION
A water-bearing stove has a water pocket, which is installed around the combustion chamber. The water circulating in it is heated by the fire blazing in the wood-burning stove and is directed to a buffer tank integrated into the heating circuit. At the same time, cool water flows from the storage tank back into the stove water pocket. A thermal control valve ensures that the return temperature to the stove is at least 60 °C.

The jacketed combustion chamber of a water-bearing stove ensures high heat efficiency and low convection heat. The heat temporarily stored in the buffer tank can be called up at any time as needed via the heating system. In the room where the stove is installed, you can also immediately enjoy the pleasant feeling of a fireplace and the radiant heat generated by it.

SAVE HEATING COSTS WITH A WATER-BEARING STOVE
Depending on the intensity of use and the output of the stove with water pocket, the consumption of fossil fuels such as fuel oil and gas can be significantly reduced. This not only leads to a noticeable reduction in heating costs, but also protects the environment.

In the transitional period, up to 100% of the energy requirement for heating and domestic hot water can often be covered by a water-bearing stove, which is an ideal addition to a heating concept that is as sustainable as it is economical.

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On 12.4.2022, 18:52:45, Aussiedog said:

if there's a way of combining the existing wood heater with ...???...the existing gas heating system???

One thing that came up in my research was the possibility to have a wood burning oven with a water reservoir which is attached to the existing heating system thus supplementing the heating of the water tank which circulates through the radiators. 

I have no idea if this is efficient, expensive, sensible etc. but I think it might be worth looking into in more detail. 

 

Wasserführender Kaminofen | Holzofen mit Wassertasche (hark.de)

This is a manufacturer's website so probably quite biased and heavy on the marketing, but a decent starting point. The terminology to search for is, apparently: Holzofen/Kamin mit Wassertasche 

 

Here is the deepl translation of the intro on the website: 

WATER-BEARING STOVE
Thanks to good insulation and efficient extraction and use of heating energy, modern houses require less and less energy. Nevertheless, there is still room for improvement. Legislation requires that at least part of the required energy comes from renewable sources. This can be obtained, for example, by means of solar thermal energy, ground-source or air-source heat pumps, or gas condensing boilers. In addition, a water-bearing stove is becoming increasingly common in the plans of house builders and homeowners.

Such a stove with a water pocket is integrated into the existing or planned heating system and can also be used in combination with a solar system, for example. About two-thirds of its combustion heat is used to heat water, which is then fed into a buffer tank for domestic and heating water. In this way, the heat produced can be felt not only in the room where it is installed, but can be used throughout the house.

EFFICIENT WOOD-BURNING STOVES WITH WATER SUPPLY
Our wood-burning stoves with water supply not only impress with their efficient technology and high cost-effectiveness, but also set visual accents. Especially when it comes to the design of the cladding of your water-bearing stove, you can choose from numerous options. Thus, depending on the model, you can choose from various materials such as soapstone and ceramic stove tiles. The tiles are handmade in Germany and are available in many different colors as well as subtle black or white.

In addition, we also offer a pellet stove water-bearing, which works on the same principle as a water-bearing stove. Instead of logs, however, it burns pressed pellets of untreated wood residues (e.g. sawdust or wood shavings).

STOVE WITH WATER POCKET - MODE OF OPERATION
A water-bearing stove has a water pocket, which is installed around the combustion chamber. The water circulating in it is heated by the fire blazing in the wood-burning stove and is directed to a buffer tank integrated into the heating circuit. At the same time, cool water flows from the storage tank back into the stove water pocket. A thermal control valve ensures that the return temperature to the stove is at least 60 °C.

The jacketed combustion chamber of a water-bearing stove ensures high heat efficiency and low convection heat. The heat temporarily stored in the buffer tank can be called up at any time as needed via the heating system. In the room where the stove is installed, you can also immediately enjoy the pleasant feeling of a fireplace and the radiant heat generated by it.

SAVE HEATING COSTS WITH A WATER-BEARING STOVE
Depending on the intensity of use and the output of the stove with water pocket, the consumption of fossil fuels such as fuel oil and gas can be significantly reduced. This not only leads to a noticeable reduction in heating costs, but also protects the environment.

In the transitional period, up to 100% of the energy requirement for heating and domestic hot water can often be covered by a water-bearing stove, which is an ideal addition to a heating concept that is as sustainable as it is economical.

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4 hours ago, fraufruit said:

My only question is how does burning wood benefit the environment?

Here what I read many times:

When trees grow they absorb CO2 in their wood. When you eventually burn them you simply release the CO2 they absorbed during their life. So the cycle plant grow burn repeat long term should be net CO2-neutral.

In fact, this is the argument in favor of growing corn in order to produce ethanol as fuel.

Not sure poor people struggling to buy food will cheer if farmers grow stuff to run our flashy cars and planes, rather than for feeding humans.

 

Not sure I agree. 

What do you think.

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The problem is with the dust from wood burning, which the greenies claim is worse than car fumes.

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Yes, we have a Wasserführende Kaminofen, ours is from La Nordica, and also has a food cooking oven.

 

It is carbon neutral, unlike fossil fuels, but does produce other crap, especially if you are not burning at the optimum temperature. FF's link is informative.

 

In our cellar we have a Pufferspeicher or something, a really big water tank with insulation and strange metal blobs, the water from this circulates up through the back of the fire and gradually that mass of water heats. This then shoves off into the heating system which is usually gas powered. 

So it is what @maxie is considering, I think.

My system would also allow solar to be added as another string to its bow, and we might do that this year.

 

We also want to insulate walls. Presumably solar panels first so as not to mess up recently insulated walls with wires, but that may be irrelevant.

 

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Thanks @maxie and kiplette, that's the kind of system that I'd heard about. Will look into it.

 

@kipletteAre you happy with how it works? Cost v benefit etc?

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Well it struggles to heat the house, which is big and badly insulated, as you say yours is. I am hoping that with insulation we will be in a better place. 

 

In terms of gas consumption, ours is low, so that's good. This year has been free wood, which is brilliant. 

 

I think for me the main learning thing would be to talk to local heating engineers about what you want. We found the oven we wanted first, advertised by a firm who would put it in and fit it to our current system but they are 70km away. In the long term I regret that we didn't think to ask a local firm if they could do what we wanted, rather than assuming that we needed this particular firm because of the oven we had chosen. Maybe we did, I don't know, but we should have asked at least.

 

We feel smug about being able to cook in the oven. Ours is  Holzöfen | TermoRossella Plus Forno DSA 4.0 | La Nordica - Extraflame a forerunner of this, less powerful but looks the same. 

 

There was another TTer with a fancier one, but I can't remember who it was/is.

 

The other thing is a Speicherofen which uses less fuel - it's a thing that relies on heating the mass of brick or whatever around it - takes a long time to heat up, but then doesn't need much to keep going. So you might want to think about that as well. I haven't looked into those, but I think it would be worth a squizz.

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