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Experiences & Questions about
Solar Energy for Self-consumption
As mentioned in a article from the prestigious CC/CA Inverter Manufacturer SMA, the future for Self-consumption of electricity produced with solar energy is very promising.
“Natural” self-consumption in a private home
To determine self-consumption, the average consumption of solar energy must be compared with the amount of energy generated by the solar power plants. Consumption depends on how many and what kind of electrical appliances are used as well as the number of people living in the household and what their consumer habits are. The amount of generated energy, on the other hand, depends on the power and location of the PV plant as well as the prevailing weather conditions.
Background: Why promote self-consumption?
The reason for promoting self-consumption is to lessen the burden on regional medium and low voltage grids. At least until further progress is made in building a modern power grid, which is capable of distributing fluctuating amounts of energy in all directions and with very little loss.
Self-consumption lessens the burden on power grids in two respects: Energy that is consumed at the same location where it is generated no longer has to be transported over the grid. In addition, energy needed for consumption does not have to be purchased via the public power grid. One of the reasons why self-consumption is so effective is that it highlights one of the special advantages of photovoltaic systems: the good correlation between power generation and energy demand over time. As an example of this correlation, solar power plants supply the most power at midday, which also happens to be the time when power is needed the most.
Aside from its ability to lessen the burden on power grids, self-consumption can generally be viewed as a future-oriented issue – especially in light of the so-called grid parity that will be achieved in Germany over the next couple of years: For once the cost of solar energy is equal to or less than the cost for conventional energy from a wall outlet, it makes sense for each solar power plants owner to use as much self-generated energy as possible.
It is nevertheless possible to increase the amount of self-consumption that is automatically present in private households. The easiest way to do that is to change consumption behavior: Whoever shows initiative and only uses major electrical appliances during hours of strong irradiation can increase their share of self-consumption by up to ten percentage points.
The number of appliances that can be switched on at the same time is of course limited by the current power of the PV plant – switching on too many appliances will result in “wasted” potential for self-consumption. Major electrical appliances should therefore be started successively rather than simultaneously. Specific example: Do not switch on the washing machine at the same time as the dishwasher or oven. Instead, switch them on one after the other or let them run in a time-delayed manner. To this end, a convenient monitoring solution for displaying the current solar power such as SMA’s Sunny Beam remote display is extremely helpful.
Combining the power monitoring device of a PV plant with an electric switching apparatus allows for the implementation of automated solutions for increasing self-consumption. The same basic rules apply here as well: Only switch on appliances if power is available in sufficient quantities and is not being used for other purposes – otherwise switch them on later or one after the other. To this end, such systems should not only be able to determine their power generation, but also their current rate of power consumption. Otherwise there is a risk that appliances which are currently running and which consume all or just some of the available PV power will be ignored. In the worst case scenario, an aditional peak load would be generated and exceed the amount of energy supplied by the PV plant – the connected appliance would then have to draw at least a part of its energy from the grid.