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Smart-grid simulation with Polysun software

The planning software Polysun provides the technical tool for smart-grid simulations

Winterthur, 8th August 2013While the term “smart-grid“ is often regarded as an empty word, recalling long-term energy policy plans, the simulation software Polysun is able to provide the technical tool for the simulation of actual smart-grid controllers. The emerging challenge of power-grid stability can be answered by adequately storing the solar energy produced in the peak sun hours. To this end, it is an essential requirement to be able to compare different system solutions with each other, for example electrical storage in batteries and thermal storage.


Example 1: Comparison between battery storage and thermal storage
In the early stages of planning, the client looks for a solution that combines maximal solar energy storage with minimal power consumption from the grid. In a first stage, Polysun helps finding the suitable battery storage and size it adequately. In a second stage, Polysun will evaluate the option of thermal energy storage, which is based on a heat pump supplying domestic hot water. The self-consumption rate of the PV installation can be increased by feeding the PV power excess to the heat pump. Polysun calculates the resulting increase of the PV own consumption rate. Additionally, Polysun enables the user to calculate and improve the annual coefficient of performance of the heat pump and at the same time reduce the power consumption from the grid.


Comparison between battery storage and thermal storage in Polysun Figure 1: Comparison between battery storage and thermal storage in Polysun: PV module, inverter, grid, battery, household loads and heat pump in one simulation.


Example 2: Installation of photovoltaic systems on an east-west pitched roofs
Taking into account the grid stability, it is an advantage if photovoltaic installations are increasingly installed on east-west roofs. The photovoltaic systems with south orientation are causing a problem for the transmission grid with their production peak at midday.


On one hand, a slightly lower energy production is expected for the same module area on east-west roofs. But on the other hand there is a larger usable roof area on east-west roofs and therefore higher yields can be obtained. To evaluate the yield difference Polysun offers the necessary degree of detail in its simulation.


For the evaluation of different photovoltaic systems it is important, that not only the orientation of the module fields is taken into account, but also the selection of the inverter. A low dimensioned inverter has the characteristic to limit the maximal power. As well as the east-west orientation, this has the effect of a better distributed energy production over the day at the cost of a slightly reduced energy production.

3D buildings created with SketchUp
Figure 2: The 3D buildings can be created with the free software SketchUp in a matter of minutes. The comparison in Polysun is as well created quickly and allows a quantitative assessment of the two situations.


Further information
The work in the area of smart-grid is realised in close co-operation with the Power Systems Laboratory of the Swiss Federal Institute of Technology Zurich (ETH) and is supported by swisselectric research as well as the Swiss Federal Office of Energy SFOE. For more information visit

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