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AndreasPlü8 Jul 2016 12:13Hello,
we still have a question regarding our house construction: We want to install a photovoltaic system in the medium term, preferably combined with a battery storage. Since prices for batteries are expected to decrease in the coming years while quality improves, does it make sense to first install a photovoltaic system with partial self-consumption and feed the surplus into the grid, and then add the battery later to switch entirely to self-consumption? Or are there technical issues or other reasons why this might not be advisable?
Regardless of this, is it sufficient to only make preparations for a photovoltaic system, and what should the scope of these preparations be? For example, we have already planned an empty conduit from the roof to the basement for a future photovoltaic system.
Thank you for your opinions!
we still have a question regarding our house construction: We want to install a photovoltaic system in the medium term, preferably combined with a battery storage. Since prices for batteries are expected to decrease in the coming years while quality improves, does it make sense to first install a photovoltaic system with partial self-consumption and feed the surplus into the grid, and then add the battery later to switch entirely to self-consumption? Or are there technical issues or other reasons why this might not be advisable?
Regardless of this, is it sufficient to only make preparations for a photovoltaic system, and what should the scope of these preparations be? For example, we have already planned an empty conduit from the roof to the basement for a future photovoltaic system.
Thank you for your opinions!
G
garfunkel8 Jul 2016 13:57I would probably have the conduit installed right away. Otherwise, I would be cautious.
In my opinion, the current storage systems are rubbish, and I seriously doubt they will be any better in a few years.
What makes you think that??
If the storage system is meant to become a core component of the photovoltaic system, I would wait until good storage options are actually available on the market.
I wouldn’t make too many preparations either. Until the photovoltaic system is installed, all of that is just idle capital.
In my opinion, the current storage systems are rubbish, and I seriously doubt they will be any better in a few years.
What makes you think that??
If the storage system is meant to become a core component of the photovoltaic system, I would wait until good storage options are actually available on the market.
I wouldn’t make too many preparations either. Until the photovoltaic system is installed, all of that is just idle capital.
T
toxicmolotof8 Jul 2016 15:49Make sure to have the conduit installed during construction. On one hand, it costs almost nothing, and on the other, it will save you a lot of mess and hassle later on.
Your biggest “challenge” will be the inverter, as it also needs to support energy storage.
So if you are considering adding storage later, the inverter must be compatible. This currently adds about 1,000 euros (around $1,100) extra. However, there is no guarantee that compatible systems will still be available in five years, or that you won’t be tied to the manufacturer and their prices at that time.
With this in mind, you are taking a risk with your investment—or you can decide to go without storage now and stick with that choice.
Your biggest “challenge” will be the inverter, as it also needs to support energy storage.
So if you are considering adding storage later, the inverter must be compatible. This currently adds about 1,000 euros (around $1,100) extra. However, there is no guarantee that compatible systems will still be available in five years, or that you won’t be tied to the manufacturer and their prices at that time.
With this in mind, you are taking a risk with your investment—or you can decide to go without storage now and stick with that choice.
Sir_Kermit8 Jul 2016 15:52Hello,
This can't really be answered off the cuff. If you're aiming for a good return on investment, you need to calculate it carefully (or have it calculated). The size of the solar panels, your own consumption patterns, the type of heating system, and feed-in tariffs all play an important role.
But first, the solar panels need to go on the roof— as many as possible, depending on what the roof’s structural capacity and your budget allow. Roof constructions with nail plate trusses usually require extra effort because mounting the panels can be more challenging. These preparatory measures should be discussed in advance with an architect, structural engineer, or energy consultant—just installing empty conduit pipes alone is, in my opinion, not enough. It doesn’t necessarily have to be more complicated, but it’s better to ask first than to have to modify anything later on the roof.
If you're referring to a standalone off-grid solution, that can indeed be quite complicated. A typical photovoltaic system initially requires a bidirectional meter, and if I recall correctly, certain regulatory and tax issues need to be addressed. After all, you are selling electricity, and it is possible that you will also need a business license. This isn't usually a major problem but could depend on the system size. This could then become a matter for a tax advisor.
For those skilled in electrical engineering, building your own storage system is feasible, though the inverter is usually purchased. Power management is also a consideration here.
Typical systems operate in a mixed mode, where you use part of the electricity yourself. If I remember correctly, about 30% is commonly self-consumed and the rest fed into the public grid. Regarding storage, either you assemble a battery storage unit yourself from batteries (there are specialized forums on this topic), or you purchase a ready-made system. I was offered 2 kWh (6.4 kWh) of storage for around 5000 euros, and you’ll find varying figures online. When calculating storage costs and lifespan, one source estimated under these assumptions:
Nominal capacity around 6.4 kWh (21.4 kWh) for a daily cycle
System efficiency about 92%
Full cycles, for example 5,000
Price, for example 6000 euros (without installation etc.)
At roughly 23 cents per kWh (only for the storage itself). You’ll find quite different numbers across the web, as storage is a complex subject.
Appliances like washing machines or ovens drain the battery quickly if they run simultaneously. That’s where power management comes into play—if your devices are internet-enabled, you can program them to run only when sufficient electricity is stored. Otherwise, you need to start them manually when a lot of electricity is available.
So: panels on the roof plus storage and I’m independent, is far more complicated in practice than it sounds on paper. Your lifestyle habits also matter.
Conclusion: small storage units are suitable for a cabin, larger ones are for enthusiasts. Preparing for installation of a battery is reasonable; also consider space in the utility room. These are no longer small AA batteries—this could be a small cabinet or more.
Whether costs will rise or fall in the medium term remains to be seen. It’s possible that many manufacturing costs will drop due to improved production processes and larger quantities, but the raw materials needed for batteries are, from my perspective, an unknown factor, as are recycling costs for old batteries.
A small note: our electricity costs are also influenced by politics—we pay for electricity that cannot be produced because wind turbines could generate it, but no one wants the power lines. I can’t estimate this factor.
Kermit
AndreasPlü schrieb:
We want to install a photovoltaic system in the medium term, preferably combined with a storage unit.
This can't really be answered off the cuff. If you're aiming for a good return on investment, you need to calculate it carefully (or have it calculated). The size of the solar panels, your own consumption patterns, the type of heating system, and feed-in tariffs all play an important role.
But first, the solar panels need to go on the roof— as many as possible, depending on what the roof’s structural capacity and your budget allow. Roof constructions with nail plate trusses usually require extra effort because mounting the panels can be more challenging. These preparatory measures should be discussed in advance with an architect, structural engineer, or energy consultant—just installing empty conduit pipes alone is, in my opinion, not enough. It doesn’t necessarily have to be more complicated, but it’s better to ask first than to have to modify anything later on the roof.
If you're referring to a standalone off-grid solution, that can indeed be quite complicated. A typical photovoltaic system initially requires a bidirectional meter, and if I recall correctly, certain regulatory and tax issues need to be addressed. After all, you are selling electricity, and it is possible that you will also need a business license. This isn't usually a major problem but could depend on the system size. This could then become a matter for a tax advisor.
For those skilled in electrical engineering, building your own storage system is feasible, though the inverter is usually purchased. Power management is also a consideration here.
Typical systems operate in a mixed mode, where you use part of the electricity yourself. If I remember correctly, about 30% is commonly self-consumed and the rest fed into the public grid. Regarding storage, either you assemble a battery storage unit yourself from batteries (there are specialized forums on this topic), or you purchase a ready-made system. I was offered 2 kWh (6.4 kWh) of storage for around 5000 euros, and you’ll find varying figures online. When calculating storage costs and lifespan, one source estimated under these assumptions:
Nominal capacity around 6.4 kWh (21.4 kWh) for a daily cycle
System efficiency about 92%
Full cycles, for example 5,000
Price, for example 6000 euros (without installation etc.)
At roughly 23 cents per kWh (only for the storage itself). You’ll find quite different numbers across the web, as storage is a complex subject.
Appliances like washing machines or ovens drain the battery quickly if they run simultaneously. That’s where power management comes into play—if your devices are internet-enabled, you can program them to run only when sufficient electricity is stored. Otherwise, you need to start them manually when a lot of electricity is available.
So: panels on the roof plus storage and I’m independent, is far more complicated in practice than it sounds on paper. Your lifestyle habits also matter.
Conclusion: small storage units are suitable for a cabin, larger ones are for enthusiasts. Preparing for installation of a battery is reasonable; also consider space in the utility room. These are no longer small AA batteries—this could be a small cabinet or more.
Whether costs will rise or fall in the medium term remains to be seen. It’s possible that many manufacturing costs will drop due to improved production processes and larger quantities, but the raw materials needed for batteries are, from my perspective, an unknown factor, as are recycling costs for old batteries.
A small note: our electricity costs are also influenced by politics—we pay for electricity that cannot be produced because wind turbines could generate it, but no one wants the power lines. I can’t estimate this factor.
Kermit
A
AndreasPlü8 Jul 2016 17:55Thanks in advance for the answers.
As you can tell, I am a beginner in this field.
We are planning to install an air-to-water heat pump, but photovoltaic systems won’t help much because, due to seasonal factors, there will likely be the least electricity generated when we need power for heating.
My guess is this: Electric cars are currently heavily subsidized. The weak point is the battery storage. There is a lot of research in this area, and Tesla plans to launch an electric vehicle with an acceptable range later this year, with others expected to follow. At the same time, demand for home energy storage systems is increasing. Both trends lead to higher sales, increased production, and should result in lower prices with better performance, similar to photovoltaic systems. These were unaffordable just 20 years ago; today, things look completely different.
So is it really like this: If we install solar panels on the roof now (I don’t expect significant price drops in the next few years), is it not easy to connect them to a future battery storage? Would it be better to just install empty conduits and leave enough space in the utility room?
As you can tell, I am a beginner in this field.
We are planning to install an air-to-water heat pump, but photovoltaic systems won’t help much because, due to seasonal factors, there will likely be the least electricity generated when we need power for heating.
My guess is this: Electric cars are currently heavily subsidized. The weak point is the battery storage. There is a lot of research in this area, and Tesla plans to launch an electric vehicle with an acceptable range later this year, with others expected to follow. At the same time, demand for home energy storage systems is increasing. Both trends lead to higher sales, increased production, and should result in lower prices with better performance, similar to photovoltaic systems. These were unaffordable just 20 years ago; today, things look completely different.
So is it really like this: If we install solar panels on the roof now (I don’t expect significant price drops in the next few years), is it not easy to connect them to a future battery storage? Would it be better to just install empty conduits and leave enough space in the utility room?
Sir_Kermit8 Jul 2016 19:21Hello,
When it comes to the detailed technical aspects, I’m not particularly well-versed either.
Per square meter of panel area, roughly 150 to 300 watts of electrical power are generated (there is also the unit kWp, kilowatt peak), but that’s a separate topic. As a rough estimate, you can consider panel area roughly equal to output power. I quickly found a figure for northern Germany: 10 sqm (108 sq ft) of panels generate about 800 kWh of electricity per year as a rough approximation.
With sufficient photovoltaic capacity on your roof, you can cover part of the electricity needs of your air-to-water heat pump. This happens automatically — the solar system generates electricity and feeds it into the grid via an inverter, minus what you consume directly in the house. The electricity meter must be able to measure both ways, which should be straightforward. Alternatively, you might have a standard meter plus a separate feed-in meter, but only your energy provider can tell you how that specifically works and who pays what.
One idea: the inverter converts the DC power from the storage into proper AC power. If the storage capacity is too small, a larger inverter can stress it too much and shorten the battery’s lifespan. Storage is supposed to last several years. As to exactly how this coordination should be done, please ask solar specialists, as I only know the general technical outline.
Regarding the inverter you will need anyway: this power electronics needs to be cooled, either actively with fans or passively by natural convection, depending on your required capacity.
In summary: the cost of a photovoltaic system is reasonably predictable if you have the financial means. If profitability or even just payback time is not critical for you, go for it. Don’t forget costs for insurance, maintenance, and possibly additional meters.
Storage is a topic on its own; planning the infrastructure for it: yes. Buying it now: probably not.
Kermit
When it comes to the detailed technical aspects, I’m not particularly well-versed either.
AndreasPlü schrieb:Solar yield depends a lot on the region where you plan to live. More sun means more electricity. And there is sunlight in winter too, but the general point is basically correct. That said, an air-to-water heat pump generally operates more efficiently during the day due to higher outdoor temperatures and can be, and should be, powered by the photovoltaic system. So those technologies can complement each other well.
We are planning an air-to-water heat pump, but photovoltaics don’t contribute much since seasonally, when we need electricity for heating, solar output is usually at its lowest.
Per square meter of panel area, roughly 150 to 300 watts of electrical power are generated (there is also the unit kWp, kilowatt peak), but that’s a separate topic. As a rough estimate, you can consider panel area roughly equal to output power. I quickly found a figure for northern Germany: 10 sqm (108 sq ft) of panels generate about 800 kWh of electricity per year as a rough approximation.
With sufficient photovoltaic capacity on your roof, you can cover part of the electricity needs of your air-to-water heat pump. This happens automatically — the solar system generates electricity and feeds it into the grid via an inverter, minus what you consume directly in the house. The electricity meter must be able to measure both ways, which should be straightforward. Alternatively, you might have a standard meter plus a separate feed-in meter, but only your energy provider can tell you how that specifically works and who pays what.
AndreasPlü schrieb:Have you considered that the car itself is a storage device, even a fairly large one? There are even concepts for using electric cars as decentralized storage units, although charging and discharging must be carefully controlled. After all, the car still needs to be able to drive.
My speculation is: Electric cars are currently heavily subsidized. The weak point: storage.
AndreasPlü schrieb:It’s not quite that simple. When cell production ramped up here, the Chinese built large solar factories with substantial government subsidies. Prices then dropped into affordable ranges. Solar cells are manufactured similarly to semiconductor chips found in computers—that is, mass production of semiconductors. Those processes and equipment have been well established for a long time, whereas battery production is still a bit more complex. For now. That gives good prospects that companies, like Tesla, will deliver good prices.
Demand for home storage systems is also increasing. Both lead to higher sales, increased production, and should bring prices down with higher output – like photovoltaic systems. They were unaffordable 20 years ago but look very different today.
AndreasPlü schrieb:If you roughly coordinate the capacities of both system components, that’s a relatively minor technical issue. Technically, many solutions will work, but whether power, costs, and lifespan all align well is another matter—and usually the more important one. Because that costs money and isn’t immediately obvious.
So is it really the case that if we put panels on the roof today (I don’t expect major price drops in the next years) it’s not easy to connect them to a future storage system?
One idea: the inverter converts the DC power from the storage into proper AC power. If the storage capacity is too small, a larger inverter can stress it too much and shorten the battery’s lifespan. Storage is supposed to last several years. As to exactly how this coordination should be done, please ask solar specialists, as I only know the general technical outline.
AndreasPlü schrieb:If you have spare space, definitely yes. Please don’t forget your roof and a potential photovoltaic insurance. Not all home insurance policies cover damages to or caused by photovoltaic systems (which carry several hundred volts), but you can also easily be overinsured. Only an insurance expert can advise you properly.
So better just install empty conduits and leave enough space in the utility room?
Regarding the inverter you will need anyway: this power electronics needs to be cooled, either actively with fans or passively by natural convection, depending on your required capacity.
In summary: the cost of a photovoltaic system is reasonably predictable if you have the financial means. If profitability or even just payback time is not critical for you, go for it. Don’t forget costs for insurance, maintenance, and possibly additional meters.
Storage is a topic on its own; planning the infrastructure for it: yes. Buying it now: probably not.
Kermit
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