Hüdig answers this question

We have been using vacuum-assisted dewatering pumps for groundwater lowering and general pumping for over half a century. The HC468 and HC488 series are electrically driven units with a particularly small ecological footprint.

The ongoing discussion about the use of low-emission drive systems has not left us unscathed. We are repeatedly asked whether it is possible to use solar power systems in combination with our electric dewatering pumps.

The yield of a photovoltaic system depends on various factors, such as the system efficiency, global radiation, orientation, shading, ambient temperature, and so on. In addition, an energy storage system must be used, which serves as a buffer for the night time. This must be long-lasting, allow a high number of charging cycles and be charged in parallel by the solar system within the daytime or solar time. Energy storage is becoming more efficient, but currently a 90kWh battery storage can be as expensive as a mid-range car.  In order not to go beyond the scope of this article, we calculate the following average values and factors for the following example:

- 300Wh /m² output of the solar plant

- 250 EUR/m² for the solar system

- 25.000 EUR for a 90 kWh energy storage system

- Inverter approx. 300 EUR

- 40.000 EUR for a 150 kWh energy storage system

- Inverter approx. 500 EUR

- 12 hours of solar radiation / 12 hours of shading and darkness

- Average power demand of the HC468/15 approx. 7,4kW/h

- Average power demand of the HC488/15 ca. 11,8kW/h

- 0,30 EUR /kWh

If these figures are taken into account in a calculation, the following investment values result which would be necessary for the operation of the plant:

HC468/15          
- ca.50m² Solar surface a 250 EUR/m²     = 12.500 EUR
- Energystorage90 kWh                           = 25.000 EUR
-Inverter                                                      =      500 EUR
Total:                                                        = 38.000 EUR

HC488/15          
- ca.80m² Solar surfac a 250 EUR/m² =    20.000 EUR
- Energystorage150 kWh                   =    40.000 EUR
- Inverter                                            =        800 EUR
Total:                                                  =   60.800 EUR

For the calculation examples shown above, the acquisition costs of the respective vacuum units and accessories must also be added. These costs are negligible in the final analysis, as they would be incurred in both cases, in mains operation and also in battery operation.

If we now assume an electricity price per kWh of 30 cents (and rising), the additional costs of the solar-powered drive will be amortized after 126,000 hours (14.38 years) for the HC468/15 and 229,000 hours (26.17 years) for the HC488/15. From an economic point of view, this calculation currently does not add up, since the payback period is much too long due to the high initial costs. Other problems, such as the chronic lack of space on construction sites (especially in inner cities), add to the difficulty.

From an ecological point of view, this model produces almost no emissions, but the statement is only valid if the manufacturing process of the pumps, solar collectors, energy storage, etc., as well as the later following recyclable material disposal are disregarded.

Conclusion:

With our electrically operated vacuum systems, we are already making a contribution to reducing CO2 emissions when using green electricity. For reasons of economic efficiency, it is not foreseeable at the present time that this plant can be reasonably operated with energy from solar plants in the near future.