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Ways to utilize excess solar energy

Green energy is inexorably entering our daily lives. Many households have already acquired small solar power plants, the basis of which is a hybrid solar inverter.

However, owners of such stations often face the problem of excess solar generation, when the panels can generate more energy than is currently consumed. We offer an effective solution to this problem using the SV701,SV705 devices.

1. Using on-grid inverters

On-grid inverters allow you to discharge excess energy into an external electrical network. This is a technically good option, but it comes with a number of difficulties:

• The high cost of such inverters compared to off-grid models;
• Bureaucratic difficulties associated with registration of generation into the network;
• Problems with certification. Many budget inverters do not have the necessary certificates for generating into the network;
• The need to purchase additional equipment (bidirectional electricity meters and generation quality control devices);
• Low tariffs for reverse generation in some countries;
• Lack of access to the external network in remote regions, during natural disasters or military operations.

2. Payload for excess energy

A more affordable solution is to use an additional payload to recycle excess solar energy. Energy-intensive devices such as electric water heaters or space heaters are already present in many homes. However, they have a fixed consumption, and the excess energy from solar panels is variable, depending on the time of day, weather and battery charge level.

More expensive inverters usually have the ability to dump excess solar energy into an additional port using a functionSmartLoador similar. But budget inverters do not have this function. It is for such inverters that our device was originally created in 2025SV701, which provides control of additional load and utilization of excess energy directly. Later we received requests from owners of inverters that have a standard functionSmartLoad. It turned out that this function is not suitable for everyone, since it works through charging and discharging the battery, and the additional inverter port may be occupied by other equipment. Now we have added support for such inverters. Taking into account operating experienceSV701in 2026 we released the next improved version of the device SV705.

Devices SV701, SV705 control a special type of solid-state relay (optotriac) with LA (4-20mA) or VD (0-10V) characteristics and can operate in two modes. The first mode is a regular dimmer with manual remote control of the output power. The second mode is “smart regulation” of power, which allows you to select only excess power from solar panels.

Theoretical foundations

Let's see how it works. Any solar hybrid inverter includes a control unit for the maximum power point of solar panels (MPPT), which allows you to extract maximum power from them at the current illumination. Exists several algorithms searching for this point and it is not known in advance which algorithm a particular inverter uses. What they have in common is that they all determine the point of maximum power on the current-voltage characteristic of the solar panel, always in a fairly narrow voltage range, which is approximately in the zone of 0.7-0.8 relative to the no-load voltage of the solar system. Also, all inverters behave identically in the case when the power of solar energy from the panels begins to exceed the power of all its consumers. In this case, they “step out” from the maximum power point to reduce the generation power by increasing the voltage at the solar input. Observe the performance of your solar inverter when it has enough load to utilize all the solar energy. You will see that the solar input voltage at this moment is always within a certain narrow range. Now watch it when the inverter load is not enough to absorb all the solar energy. You will see that the voltage has moved out of that narrow range and increased.

This is illustrated graphically in the figure below. There are typical dependences of current on voltage and power on voltage for a solar cell. These graphs show where the inverter moves the power take-off point in case of excess solar energy.

It is this pattern that our devices use to controllably increase or decrease the inverter load in order to return the system to the maximum power zone. SV701, SV705 organize a second circuit, external to the inverter, to search for the maximum power point! The device polls the inverter once per second and quickly regulates the load.

The boiler is also a battery :)

I would like to dwell separately on such an energy consumer as an electric boiler. Many solar inverter owners view it as an annoying and power-hungry load on their system. If you connect the boiler directly to the inverter, this is indeed the case. But using a boiler in conjunction with the SV705 allows you to look at it from a different perspective. Hot water is always needed for domestic use. To heat 100 liters of water by 50 degrees (from 20C to 70C) you really need to spend quite a lot of electricity - about 5.8 kWh. But a boiler can also be considered as an energy storage device! With good thermal insulation, it retains thermal energy for a long time. Moreover, the cost of such a 5.8 kWh storage device will be an order of magnitude lower than the cost of a comparable electric battery. Therefore, it is quite reasonable to dump “excess” electrical energy there and then use hot water as needed. Moreover, SV701, SV705 allow you to do this in “smart mode” without overloading the inverter.

Another alternative load for SV701, SV705 may be other types of heaters. For example, an auxiliary heater for heating a house in cold seasons or a pool heater in warm seasons.

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