ᐅ Is a natural stone heating system practical when combined with a photovoltaic system?
Created on: 29 Sep 2012 18:18
M
Mellomacher
Hello, I am currently trying to figure out which heating system makes the most sense.
I have a quote for a heat pump with geothermal drilling plus underfloor heating for 32,000 euros.
An air source heat pump is about 10,000 euros cheaper, so 22,000 euros, but the seasonal performance factor (SPF) of 3.5 is rarely achieved in practice and realistically drops to about 2.8 (energy inefficient).
Ventilation with heat recovery is included in the price, costing about 6,000 euros.
I plan to build a timber frame house with a U-value of 0.14 and triple glazing; the building envelope meets KfW 55 standard. The living area is about 130 m² (1,400 ft²).
I also had a consultant who recommended a natural stone heating system since the building requires little energy.
The natural stone heating would cost around 9,000 euros.
Until now, I was reluctant to consider this option, but looking at follow-up costs and maintenance expenses, the natural stone heating combined with a photovoltaic system becomes attractive.
Assuming an energy consumption of 40 kWh/m² per year, this results in 5,200 kWh without hot water.
That would be about 1,200 euros in electricity costs without a special tariff, based on 0.23 euros per kWh (relatively close to gas prices).
If the actual consumption is 60 kWh/m² per year, that would be 8,500 kWh without hot water, so 1,800 euros in electricity costs (which is expensive).
If I invest the costs of drilling and underfloor heating, approximately 16,000 euros, into a photovoltaic system that produces 8,000 kWh of electricity per year,
then the monthly heating costs would be zero, although loan interest, repayment, and other costs would obviously apply.
Advantages of this heating system are no maintenance costs and a very long lifespan.
The photovoltaic system incurs monthly meter fees, and I still need to inquire about maintenance.
Of course, the photovoltaic system’s performance decreases over time; after 20 years it should still perform at about 85%, and by then smaller, more affordable solar panels will also be available.
The total investment is also around 30,000 euros, with running costs and maintenance close to zero per month.
Is this an overly optimistic calculation, or does it sound reasonable?
I have a quote for a heat pump with geothermal drilling plus underfloor heating for 32,000 euros.
An air source heat pump is about 10,000 euros cheaper, so 22,000 euros, but the seasonal performance factor (SPF) of 3.5 is rarely achieved in practice and realistically drops to about 2.8 (energy inefficient).
Ventilation with heat recovery is included in the price, costing about 6,000 euros.
I plan to build a timber frame house with a U-value of 0.14 and triple glazing; the building envelope meets KfW 55 standard. The living area is about 130 m² (1,400 ft²).
I also had a consultant who recommended a natural stone heating system since the building requires little energy.
The natural stone heating would cost around 9,000 euros.
Until now, I was reluctant to consider this option, but looking at follow-up costs and maintenance expenses, the natural stone heating combined with a photovoltaic system becomes attractive.
Assuming an energy consumption of 40 kWh/m² per year, this results in 5,200 kWh without hot water.
That would be about 1,200 euros in electricity costs without a special tariff, based on 0.23 euros per kWh (relatively close to gas prices).
If the actual consumption is 60 kWh/m² per year, that would be 8,500 kWh without hot water, so 1,800 euros in electricity costs (which is expensive).
If I invest the costs of drilling and underfloor heating, approximately 16,000 euros, into a photovoltaic system that produces 8,000 kWh of electricity per year,
then the monthly heating costs would be zero, although loan interest, repayment, and other costs would obviously apply.
Advantages of this heating system are no maintenance costs and a very long lifespan.
The photovoltaic system incurs monthly meter fees, and I still need to inquire about maintenance.
Of course, the photovoltaic system’s performance decreases over time; after 20 years it should still perform at about 85%, and by then smaller, more affordable solar panels will also be available.
The total investment is also around 30,000 euros, with running costs and maintenance close to zero per month.
Is this an overly optimistic calculation, or does it sound reasonable?
B
Bauexperte2 Oct 2012 11:57Hello €uro,
I have already mentioned that I am not an engineer and have entrusted the calculations to a planning office. However, it seems either you or I might be misunderstanding something. In a natural stone heating system, ventilation heat losses play absolutely no role. The system uses walls, ceilings, floors... the structure itself – for example, the (massive) walls store heat for up to 2 hours – the room air stays consistently warm or cool; depending on the perspective. I don’t know if you have ever worked with such a system? You can think of its effect as comparable to “sunbathing” in the mountains. The outside temperature might be minus x° Celsius (x°F), and yet you hardly feel cold. That is why the rooms do not “suffer” even after extended ventilation phases.
I have not sold this system for several years because I was tired of running into the walls of the big energy providers. Accordingly, I no longer have contact with my former customers. I might still be able to provide some calculations (they should be on the tapes in the respective data backups) – but whether I still have any invoices from the utilities, I doubt it – I’m happy if I gain some space each year following the 10-year storage requirement. In case of doubt, you will have to trust the information I provide.
Kind regards
€uro schrieb:
.. without taking ventilation heat losses into account, which would be urgently necessary.
I have already mentioned that I am not an engineer and have entrusted the calculations to a planning office. However, it seems either you or I might be misunderstanding something. In a natural stone heating system, ventilation heat losses play absolutely no role. The system uses walls, ceilings, floors... the structure itself – for example, the (massive) walls store heat for up to 2 hours – the room air stays consistently warm or cool; depending on the perspective. I don’t know if you have ever worked with such a system? You can think of its effect as comparable to “sunbathing” in the mountains. The outside temperature might be minus x° Celsius (x°F), and yet you hardly feel cold. That is why the rooms do not “suffer” even after extended ventilation phases.
€uro schrieb:
I would be very interested in those results. You could surely provide me with the numbers (calculations, actual energy consumption).
I have not sold this system for several years because I was tired of running into the walls of the big energy providers. Accordingly, I no longer have contact with my former customers. I might still be able to provide some calculations (they should be on the tapes in the respective data backups) – but whether I still have any invoices from the utilities, I doubt it – I’m happy if I gain some space each year following the 10-year storage requirement. In case of doubt, you will have to trust the information I provide.
Kind regards
Hello Building Expert,
I will refrain from comparing this to the expertise of our politicians (ministers) at this point.
Best regards.
Bauexperte schrieb:That is problematic; when working in fields where you lack proper and sufficient training, you are professionally vulnerable and open to any speculation, especially when making general statements.
....I have already mentioned that I am not an engineer and have left the calculations to a design office.
I will refrain from comparing this to the expertise of our politicians (ministers) at this point.
Bauexperte schrieb:Absolutely Nobel Prize-worthy. Ventilation heat losses are always present (infiltration) depending on the building construction (airtightness)! Suddenly, not in this case? How miraculous.
.... In a natural stone heating system, ventilation heat losses are absolutely irrelevant.
Bauexperte schrieb:Why 2 hours? Should it not be only 0.1 or 4 hours instead?
...The system uses the walls, ceilings, floors ... bodies – for example, the (massive) walls store heat for up to 2 hours...
Bauexperte schrieb:What is meant by "perspective"? According to which principles is the return temperature uniform everywhere?
...- the indoor air temperature is always the same, warm or cold; depending on the perspective.
Bauexperte schrieb:Try standing in the shade then, and you will freeze.
....You can imagine the function like a "sun bath" in the mountains. The outside temperature is minus x° and you still hardly feel cold.
Bauexperte schrieb:That is hard to understand since they would benefit from high electricity consumption.
....I have not sold this system for several years now, as I was tired of running into the walls of the big energy suppliers.
Bauexperte schrieb:Hardly, since you have revealed yourself as an unqualified salesperson.
...In case of doubt, you will have to trust my statements.
Best regards.
B
Bauexperte2 Oct 2012 17:18Hello €uro,
Kind regards
€uro schrieb:So, you have no trust in engineering firms?
It is problematic when operating in areas where one lacks proper and sufficient training, as one becomes professionally unstable and open to all kinds of miscalculations, especially when making general statements.
I will refrain from comparing this to the expertise of our politicians (ministers) here.
€uro schrieb:What’s gotten under your skin? I wrote: "With a natural stone heating system, ventilation heat losses absolutely do not play a role." Not a word about them not occurring.
Nearly Nobel Prize-worthy Ventilation heat losses are always present, depending on the building construction (infiltration) (airtightness)! Suddenly not here? How miraculous?
€uro schrieb:Inside a house, there is usually no shadow ...
Stand in the radiation shadow and you’ll get really cold.
€uro schrieb:At that time—17 years ago—RWE earned significantly more from gas than electricity; therefore, their interest in a heating system that would run on the heat pump tariff was close to zero. Only recently have their policies begun to shift. Sooner or later, night storage heaters will likely become more common again, since RWE (like all utilities) does not know what to do with all the electricity from wind turbines.
Incomprehensible, they would actually be pleased about high electricity consumption.
€uro schrieb:More than one thing must be bothering you...
Unlikely, since you have revealed yourself as a professionally untrained salesperson.
Kind regards
Hello building expert,
Yes, as long as they adhere to recognized technical standards (e.g., heating load calculation according to DIN 12831). Otherwise, I would have serious concerns.
No nerves, just annoyed by half-truths or inaccuracies. If, as you confirmed here, ventilation losses do exist but were not considered in the balance, a deficit arises. How is that compensated? The standard heating load (capacity) is completely independent of the heat generator and energy source!
40 kW/m² (430 ft²) is close to a power plant output.
Try building a partition wall behind grandma’s tiled stove, for example made of cardboard, and stand behind it. The comfort level will vanish. Mr. Stefan Boltzmann has provided enough foundational work on this. There is no need to reinvent established knowledge, only to apply it professionally! In my own planning, I sometimes use electric heating (infrared) for temporarily covering peak loads when additional warm water, for instance, is not possible. Especially with heat pump systems, because it does not make sense to reduce the overall system efficiency due to a small bathroom area.
Are you seriously expecting falling electricity prices? Let’s stick to direct electric heating:
Building with 15,000 kWh/year (energy demand for heating only); exact system sizing assumed:
Gas: $0.07 per kWh; Electricity: $0.19 per kWh
Gas condensing boiler: 18,750 kWh/year => $1,313/year
Air-source heat pump: 4,286 kWh/year => $814/year
Ground-source heat pump: 3,333 kWh/year => $633/year
Electric marble heating: 15,000 kWh/year => $2,850/year
Building with 2,500 kWh/year (energy demand for heating only); exact system sizing assumed:
Gas: $0.07 per kWh; Electricity: $0.19 per kWh
Gas condensing boiler: 3,125 kWh/year => $219/year
Air-source heat pump: 714 kWh/year => $136/year
Ground-source heat pump: 556 kWh/year => $106/year
Electric marble heating: 2,500 kWh/year => $475/year
If system planning is insufficient, significantly higher consumption can be expected.
Overall, this is purely a consumption-side view that must be supplemented by investment and financing considerations regarding economic viability.
I cannot see any absolute or generalized advantage in favor of natural stone heating.
Best regards
Bauexperte schrieb:
...So you have no trust in engineering firms?
Yes, as long as they adhere to recognized technical standards (e.g., heating load calculation according to DIN 12831). Otherwise, I would have serious concerns.
Bauexperte schrieb:
...What got on your nerves? I wrote: "With a natural stone heating system, ventilation heat losses absolutely do not matter." No word about them not occurring.
No nerves, just annoyed by half-truths or inaccuracies. If, as you confirmed here, ventilation losses do exist but were not considered in the balance, a deficit arises. How is that compensated? The standard heating load (capacity) is completely independent of the heat generator and energy source!
40 kW/m² (430 ft²) is close to a power plant output.
Bauexperte schrieb:
...There is usually no shading inside a house...
Try building a partition wall behind grandma’s tiled stove, for example made of cardboard, and stand behind it. The comfort level will vanish. Mr. Stefan Boltzmann has provided enough foundational work on this. There is no need to reinvent established knowledge, only to apply it professionally! In my own planning, I sometimes use electric heating (infrared) for temporarily covering peak loads when additional warm water, for instance, is not possible. Especially with heat pump systems, because it does not make sense to reduce the overall system efficiency due to a small bathroom area.
Bauexperte schrieb:
...RWE… Sooner or later, night storage heaters will become more common again, since RWE (and all utilities) don’t know what to do with the surplus electricity from wind power plants.
Are you seriously expecting falling electricity prices? Let’s stick to direct electric heating:
Building with 15,000 kWh/year (energy demand for heating only); exact system sizing assumed:
Gas: $0.07 per kWh; Electricity: $0.19 per kWh
Gas condensing boiler: 18,750 kWh/year => $1,313/year
Air-source heat pump: 4,286 kWh/year => $814/year
Ground-source heat pump: 3,333 kWh/year => $633/year
Electric marble heating: 15,000 kWh/year => $2,850/year
Building with 2,500 kWh/year (energy demand for heating only); exact system sizing assumed:
Gas: $0.07 per kWh; Electricity: $0.19 per kWh
Gas condensing boiler: 3,125 kWh/year => $219/year
Air-source heat pump: 714 kWh/year => $136/year
Ground-source heat pump: 556 kWh/year => $106/year
Electric marble heating: 2,500 kWh/year => $475/year
If system planning is insufficient, significantly higher consumption can be expected.
Overall, this is purely a consumption-side view that must be supplemented by investment and financing considerations regarding economic viability.
I cannot see any absolute or generalized advantage in favor of natural stone heating.
Best regards
M
Micha&Dany4 Oct 2012 10:07Bauexperte schrieb:
Sooner or later, night storage heaters will become more common again, since RWE (and all utilities) don’t know what to do with all the electricity generated by wind turbines. Hello Bauexperte,
or maybe more likely daytime storage heaters – especially once solar power from photovoltaic systems is added to wind energy. So far, negative prices have already been seen at midday on the Leipzig power exchange – not at night.
Best regards,
Micha
Micha&Dany schrieb:
...So far, negative prices have been recorded around midday on the Leipzig electricity market... How can you, as an end user, benefit from this? Do you get the electrical energy for free or receive a bonus for using it? Best regards
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