Cut operational costs for potable water supply!
Transportation of potable water from its source to the user is impossible without conveying units. The energy demand therefor depends on the geodetical heights in the individual supply territories, but also on the efficiency of pumps and the pipeline system configuration. In dependence of transport velocity, pipe surface and pipeline system configuration, pressure losses incur which have a negative affect on the annual current cost. The overall consumption of public water supply in Germany is approx. 3 milliards kWh/a.
It is called for saving energy. The committee of experts for conveying units deals with this topic and makes interesting suggestions in its W 611 sheet, some of which are reported in the following:
Potable water storage tanks allow for uniform operation, especially peak consumption can be economically covered. It must however be made sure that the water level is only as high as this is operationally necessary and that the feeding point lies below water level.
Attention should be paid to optimise the pipe inside diameter and select the proper material. As to roughness of the pipe, stainless steel performs extraordinarily well, for it has a very low roughness 'k' on the one hand, on the other there is hardly any risk of deposition or ad-herence which would narrow the cross section and increase the loss of pressure. If there should occur some deposition all the same, this can be easily removed from the plane surface. The biggest pressure losses in the water work, however, are not found in the straight pipeline but in the required fittings, armatures and gauges. Therefore, it must be paid attention that these components are arranged in a way which is favourable for flow-through. This begins already with the inlet and 2000 outlet constructions in the tank. While for example the discharge strainer has a resistance coefficient of 2.2, this is only 0.03 of a flow-accommodating discharge tulip.
After optimisation of pumping station equipment the pressure loss can be significantly reduced. With nearly the same investment costs this may be an annual financial advantage of some thousand Euro.
Saving energy starts with optimal planning which determines the general framework for how high the operational cost will be later. The possibilities of improvement are not limited to new constructions. Also refurbishing with the right choice of material, armatures and pipeline arrangement can durably save energy costs.
Roughness coefficient k (mm) for straight pipes
- uninsulated cast pipe 0.250
- insulated cast pipe 0.125
- galvanized steel pipe 0.125
- stainless steel pipe < 0.050