ᐅ Thermal Solar: Photovoltaic System for Domestic Hot Water Production
Created on: 7 Apr 2016 21:29
T
T21150Thread for relaxation – I don’t want to start a fundamental discussion.
Steffi is working late shift, and I have some peace and quiet.
I did some calculations, although I initially overcomplicated things. But it can be simpler.
Since installation, the photovoltaic (PV) system has produced an average of 2.26 kWh per day.
I know the house and heating system well and understand that without the PV system, we would need about 4.5 kWh/day (using gas) just for hot water generation in our home. We are not exactly sparing with hot water. Both of us shower at least once daily, and I have the energy-wasting habit of pre-rinsing dishes with hot water before loading them into the dishwasher (because the machines don’t handle dirt well and tend to break prematurely).
So, the solar coverage rate is roughly 50% based on a simplified consumption estimate (the real calculation would be more complex). It was calculated at 62%, which I find acceptable. In North Rhine-Westphalia, summer 2015 was mostly rainy and gloomy, unlike other regions where it was sunny and good.
Presumably, under normal weather conditions, around 60% coverage would have been achieved, based on calculations.
From my observations, however, the PV kWh don’t count quite so directly; there are significant losses.
I estimate about 30% less efficiency because a lot of the heat ends up at the bottom of the storage tank, which doesn’t provide immediate benefit (stratified storage tank).
Overall, it’s a good result, which somewhat surprised me.
Conclusion:
- Heating drinking water doesn’t cost much
- The PV system provides roughly the share calculated in the energy performance certificate, even with an east-facing orientation. This is a calculated estimate; the real figure is lower but tolerable.
- The investment cost: *look away*, check it off.
- I would not invest the money again, but now that I have it, I don’t want to miss it because I like gadgets. Technically, it’s nice because it’s simple and fundamentally works (which many things nowadays don’t).
Thorsten
Steffi is working late shift, and I have some peace and quiet.
I did some calculations, although I initially overcomplicated things. But it can be simpler.
Since installation, the photovoltaic (PV) system has produced an average of 2.26 kWh per day.
I know the house and heating system well and understand that without the PV system, we would need about 4.5 kWh/day (using gas) just for hot water generation in our home. We are not exactly sparing with hot water. Both of us shower at least once daily, and I have the energy-wasting habit of pre-rinsing dishes with hot water before loading them into the dishwasher (because the machines don’t handle dirt well and tend to break prematurely).
So, the solar coverage rate is roughly 50% based on a simplified consumption estimate (the real calculation would be more complex). It was calculated at 62%, which I find acceptable. In North Rhine-Westphalia, summer 2015 was mostly rainy and gloomy, unlike other regions where it was sunny and good.
Presumably, under normal weather conditions, around 60% coverage would have been achieved, based on calculations.
From my observations, however, the PV kWh don’t count quite so directly; there are significant losses.
I estimate about 30% less efficiency because a lot of the heat ends up at the bottom of the storage tank, which doesn’t provide immediate benefit (stratified storage tank).
Overall, it’s a good result, which somewhat surprised me.
Conclusion:
- Heating drinking water doesn’t cost much
- The PV system provides roughly the share calculated in the energy performance certificate, even with an east-facing orientation. This is a calculated estimate; the real figure is lower but tolerable.
- The investment cost: *look away*, check it off.
- I would not invest the money again, but now that I have it, I don’t want to miss it because I like gadgets. Technically, it’s nice because it’s simple and fundamentally works (which many things nowadays don’t).
Thorsten
Addendum. Yesterday the weather was generally favorable, especially in the morning and throughout the afternoon. It was practically the first time this year that the system operated properly.
The system generated 9.1 kWh (this is a calculated value from the system).
And it heated the 300 liters (79 gallons) of water from 34°C (93°F) in the morning to 49°C (120°F).
A maintenance was performed in autumn 2015, during which several parameters were adjusted in the system (fluid flow behavior over temperature) – according to the latest specifications from Buderus. I have to say: this really made a difference, the system is now running more efficiently.
I am satisfied with the results from yesterday.
The system generated 9.1 kWh (this is a calculated value from the system).
And it heated the 300 liters (79 gallons) of water from 34°C (93°F) in the morning to 49°C (120°F).
A maintenance was performed in autumn 2015, during which several parameters were adjusted in the system (fluid flow behavior over temperature) – according to the latest specifications from Buderus. I have to say: this really made a difference, the system is now running more efficiently.
I am satisfied with the results from yesterday.
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