PV Systems

Description

In the past, numerous homes had PV systems installed. Nowadays, home owners are concerned that the photovoltaic (PV) system on their roof may not only have advantages, but could possibly cause health risks, because of the electromagnetic fields caused by the system.

PV systems in operation generate both, static and alternating electric and magnetic fields. The strength of the fields depends on the design of the inverter, the performance of the system and also the extent, in which the modules in series or parallel are interconnected.

Due to the direct current of electricity in the PV cells, the fields are mainly static fields and therefore less critical for the health. We are permanently exposed to static electric and magnetic fields by nature. The static electric field above ground in the open, in good weather, can reach a value of 150 volts per meter. The natural magnetic field of the earth has an induction by 40.000 nanotesla.

Electrical fields can hardly penetrate into buildings and moreover, can be shielded easily. However, magnetic fields on the other hand penetrate building envelopes full force and are very hard to shield. The PV system generated electric field can therefore be neglected within the house.

Biologically much more effective than static fields are alternating fields. These arise in PV systems in addition to the static fields by reactions from the network and by superimposition of the PV-circuit DC current flowing with AC shares. How large the alternating field share in the PV-circuit is, depends on the electrical properties of the inverter.

For the lowest possible production of electrosmogs by a PV system, the inverter should have a transformer, to prevent system perturbation on the modules (galvanic isolation). Unfortunately, due to the higher costs and somewhat lower efficiency, inverters with a transformer are rarely installed. It depends on the properties of the inverter, how strong the DC flowing through the branch lines of the PV system, is superimposed by AC shares.

In the long run, keep at least 1 m distance from the PV system.
Measurements on PV systems have shown that the alternating magnetic field share in 1 m distance already decreases under international precautionary values (under 200 nano tesla). Electromagnetic emissions, which could lead to increased health risks under permanent exposition, can therefore only be expected if beds or other areas of permanent residence are located just behind or below the modules.

Beds and other permanent residence areas should have at least 1 m distance from the current-carrying parts of the system and especially to the inverter. The cables of the branch line between the modules and the inverter should be twisted around each other to weaken the magnetic fields. Additional precautionary measures appear to not be necessary or useful.

In case of larger systems, the NS distribution installation should not be omitted from consideration. The greater the power of the system, the more energy is being fed into the network. These currents can create a remarkable magnetic field. This situation can be solved with the appropriate location of the inverter or with a surface shield. 

Pictures

In this example, the inverter was installed on the side turned towards the animals. With the surface shield on the wall and on the floor, the magnetic fields are kept away from the animals

20130705 172138        20131025 092439        20131107 143938       20131209 134236  
Wall and floor shielding   Floor shielding with
checker plates
     
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