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Updated 2025-09-10
Solar Power
What is a solar string?
A solar string or a PV string is a number of solar panels that are connected in series.
Solar panels are almost always connected in series to reach a higher voltage, which in turn reduces cable losses. When connected in series, the voltage increases but the current is constant.
For example, if we connect 5 panels with an Impp (current at maximum power) of 11 Amps and a Vmpp (voltage at maximum power) of 37 Volts in series, the solar panel string will have a current of 11 A and a voltage of 185 V.
What is and does an SSO do?
SSO stands for Solar String Optimizer and is the component of the Ferroamp system that manages and integrates solar panels and solar power generation.
- The SSO is a DC/DC converter that converts the voltage from panels into 760 V, which is the voltage on Ferroamp’s DC grid.
- The SSO has an MPPT (Maximum Power Point Tracker) that optimizes solar output from the solar string connected to the SSO. It does this by constantly regulating the current and voltage through the panels up and down to find the optimal level based on the solar radiation.
- The SSO communicates continuously with EnergyHub when the system is operational. It constantly measures how much is produced and sends this to EnergyHub, which uploads the data to EnergyCloud.
- An SSO has a minimum starting voltage of 100 V, which means that in principle it is always required at least 3 panels connected in series to reach sufficient voltage for the SSO to start.
- SSO can handle most panels on the market as long as the maximum current (Impp) of the panels is a maximum of 16 A.
In the Ferroamp system, solar cells are connected to the EnergyHub inverter via solar string optimizers (SSO) and a DC distribution box.
How do I turn solar production on and off?
Go to: EnergyCloud/ System settings/ System configuration
By clicking the button you can turn off or turn on your solar power production. When the button is green, the solar power production is on and the solar cell optimizers are producing, if the button is gray, the solar power production is turned off.
NOTE! EnergyCloud can only control solar power production that is produced through an SSO (Solar String Optimizer), it is not possible to control production that is located on an external inverter.
NOTE! The settings will not be implemented until you have clicked “UPDATE” and sent the settings to your EnergyHub.
How does the presence of SSOs affect the safety of the photovoltaic system?
An advantage of the Ferroamp system from a safety point of view is that the cables between the SSO and the EnergyHub become de-energized if the EnergyHub and SSO lose contact with each other, which happens in the event of a power outage, for example. The only thing that is still energized is the cable between the panel and the SSO. Therefore, Ferroamp recommends placing the SSOs as close to the panels as possible.
I already have a photovoltaic system. Do I need to replace it to use the Ferroamp system?
You don’t need to replace your solar system to use the Ferroamp system. If you want to connect a battery with Ferroamp’s smart control or want to take advantage of any of Ferroamp’s other features, you can do it in two ways:
1. Keep your old inverter and supplement with an EnergyHub.
You will then have access to:
- Dynamic phase balancing- smart metering
- Load Guard and Control of EV Charging via OCPP
- Smart battery management
However, you will not see solar production in your Ferroamp App or in EnergyCloud.
2. Replace the old inverter with EnergyHub. You will then have access to all the functions above, but can also follow the solar production in Ferroamp’s App and in EnergyCloud. The solar panels are then connected to EnergyHub via Ferroamp’s solar string optimizer (SSO).
What factors affect solar power production?
There are a variety of parameters that affect the electricity production that the solar cells deliver. The rated power of the solar cells is normally specified at a solar irradiance of 1000 W/m2 and a panel temperature of 25°C. This is roughly equivalent to the solar radiation on a clear day with blue skies during the summer months. Although the panel temperature often gets higher than 25°C on summer days.
Factors affecting production:
- The position of the sun in relation to the solar cells
The highest effect is obtained from the solar cells when the sunlight falls in perpendicular to the panels. For a south-facing photovoltaic system with a roof pitch of 35°, this occurs in the middle of the day during the month of June. - Clouds
Cloudiness affects solar radiation to the highest degree. On a clear day with blue skies, the highest solar radiation is obtained. On a day with thick cloud cover, low solar radiation is obtained. Many days can also have varying degrees of haze and thin veil clouds that also affect the solar radiation. - Temperature
The efficiency of solar cells is temperature-dependent. Even if the panels’ rated power is specified at 25°C, the actual power on a day with 25°C outside temperature can be significantly lower because the solar cells are heated by the sun. For ordinary crystalline silicon cells (which are the most common on the market), the efficiency decreases about 0.35 – 0.40% per degree Celsius. That is, if the panel temperature rises 10°C, the power from the panels decreases 3.5 – 4%. Please note that panel temperature is not normally the same as the outside temperature. On a sunny day, the panels are heated by the sun, a windy day helps to reduce heating.
The wind affects the temperature of the solar cells. On a windy day, the panels are cooled more efficiently and can deliver more power than a sunny day with no wind, even if the outside temperature is the same. - Shadows
Shadows reduce the power of the solar cells because less sunlight hits the panels. How much the power decreases depends on how many panels in a string are hit and how the power optimization in the system works. - Pollution
Dust, pollen, leaves, algae all contribute to reducing the power of the solar cells. Normally, the panels are washed relatively well by rain in the Swedish climate, but may in some cases need to be cleaned manually. - Aging
All solar cells age and lose power over time. Normally, however, this process takes place very slowly and many manufacturers provide power guarantees of 80-90% of the original power after 25 years. Practical experience shows that this process is normally even slower, although it may vary depending on local conditions. A reasonable assumption could be that the panels lose an average of 0.5% per year.
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