ᐅ Intelligent Control of Photovoltaic System

Dear community,

I am currently exploring the use of a photovoltaic system for our upcoming new-build project. Most likely, it will be the classic combination of an air-source heat pump and a photovoltaic system (including storage).

In a book, I came across some very interesting application scenarios and wondered whether the control systems of photovoltaic installations are really that smart.

The following application scenarios (when using an energy storage system) would be ideal for our house:
- Combination of heat pump and photovoltaic
- Pool heating
- Electric vehicle wallbox

Example of a control logic: charge the car at night only if stored energy is available; heat the pool only during the day with pure solar energy; and so on.

What is the reality like? How would you implement such logics?

Thanks!

There are countless possibilities. Ultimately, it depends on what is installed in your house and what the mentioned devices are capable of on their own. Heat pump with SmartGrid? Feed-in meter with IR interface or data output? Bus system in the house with logic functions? Inverter with Modbus interface? HomeManager or similar control components for the photovoltaic system? Switchable sockets/outlets for the pool heating? Control options for the wallbox?

gregman22 schrieb:

Dear community,

I am currently exploring the use of a photovoltaic system in our upcoming new construction project.
It will likely come down to the classic combination of an air-source heat pump and a photovoltaic system (including storage).

I read about some really interesting applications in a book and wondered whether the control systems of photovoltaic systems are actually that smart.

The following use cases (when using an electricity storage system) seem very useful for our house:
- Combination of heat pump + photovoltaic
- Heating the pool
- Electric vehicle - wallbox

Control example: Charge the car at night only if stored electricity is available. Heat the pool only during the day with pure solar energy. And so on.

What is the reality like? What logics would you implement and how?

Thanks!

-> Combination of heat pump + photovoltaic
... is not a problem as long as you find professionals for both trades who work with you to implement YOUR requirements. Technically, it’s quite manageable in terms of complexity and effort. Before buying, make sure the devices (especially the heat pump) have a suitable control input.

-> Electric vehicle - wallbox
Control example: Charge the car at night only when stored electricity is available. Heat the pool only during the day with pure solar energy. And so on.

... That is of course nonsense; I would never do it that way. The home battery, if anything, will only hold the electricity the house needs at night. Everything else is neither efficient nor technically feasible nor reasonably affordable.
An average car battery is probably around 45-50 kWh, while an affordable photovoltaic battery is about 4-10 kWh. You can see there’s quite a gap.

It’s best to charge the car during the day with pure surplus solar power. Better wallboxes (such as SMA, to a limited extent Zappi, and probably many others) can do this.

... The energy demand of a small pool is quite large; the photovoltaic system won’t really make much of a difference—unless you install 30 kWp or more on the roof. For that, consider buying a dedicated heat pump for the pool. But with all the other necessary or comfort features, the pool will become very expensive.

I see. If you have the right expertise, a lot is possible. My expectations are certainly not astronomical. However, as a prospective homeowner, I find it quite challenging to consider the project as a whole. We are now starting detailed construction planning with a general contractor. It feels like strong silo thinking dominates in such a project. Everyone focuses on their own trade but shows little interest in how it all works together with other components.

i_b_n_a_n schrieb:

-> Combination of heat pump + photovoltaic system
... is no problem if you find people for both trades who will implement YOUR wishes together with you. Technically, it’s really manageable or not too complex. Before purchase, make sure the devices (especially the heat pump) have a suitable control input.

-> Electric vehicle - wall charger
Example control: charge the car only at night when stored electricity is still available. Heat the pool only during the day with pure solar energy. Etc.

... Of course, that’s nonsense, I would never do it like that. Because the home battery will, if at all, only supply the electricity the house needs at night. Everything else is neither efficient nor technically feasible or reasonably affordable. Electric car battery of an average car is probably 45-50 kWh, affordable battery for photovoltaic systems about 4-10 kWh. You see, there is a small discrepancy there.

It’s best to charge the car during the day with pure surplus electricity; better wall chargers (SMA, somewhat also the Zappi and many others probably) can do this.

... The energy demand of a small pool is so large that the photovoltaic system won’t really make much difference unless you get 30 kWp or more on the roof. Maybe buy a suitable separate heat pump for the pool. But with all the other required or comfortable extras, the pool will get very expensive.

I have little to add to that. All plausible comments that I will take into account. I cannot yet say how many kWp our roof will provide.

Fuchur schrieb:

There are countless possibilities. Ultimately, it depends on what you already have in your house and what the mentioned devices are capable of themselves. Heat pump with SmartGrid? Feed-in meter with IR interface or data output? Bus system in the house with logic? Inverter with Modbus interface? HomeManager or similar control components for the photovoltaic system? Switchable sockets/connections for the pool heater? Control options for the wall charger?

These are still completely unknown to me. I have little knowledge of these specific technologies so far.

gregman22 schrieb:

I can’t say yet how many kWp our roof will provide.

You’ll be very glad later on if you stop thinking of the roof and the photovoltaic system separately from now on. A few centimeters (inches) more roof overhang, slightly repositioning a roof window, placing the satellite dish on the facade, choosing the right roofing material (metal), commissioning the carpenter to handle the substructure at the same time – there are many details like these that make the photovoltaic system larger and more cost-effective with little extra effort.
And size is the only thing that matters. If you don’t have one yet, it’s hard to imagine how little such a system produces when there are just a few clouds. So don’t be afraid of 30, 40, or 50 kWp – it pays off!

PS: I wouldn’t buy a battery storage system at the moment; payback is practically impossible. It’s better to retrofit later when prices have dropped by about 60%.

If you can program all of this yourself, it’s no problem at all. But try to find a contractor who can handle this for different trades and then be available in a few years if something doesn’t work or needs to be changed. For that reason, my electric boiler and solar boiler are controlled by the best control system in the world: my right hand.