Economics of Cold Store control with the NWCS (Night Wind Control System)

The state of the art in cost effective control of the cold store refrigeration plant, is to make a good deal with the energy supplier about "year ahead" (or even longer) energy prices for base load and peak load. Step two is then to operate the cold store as much as possible in the base load low tariff hours.

When using the NWCS, the cold store must buy electricity on the spot energy market (in the Netherlands: the Amsterdam power Exchange APX)  The price of energy at the spot market is very variable, the APX prices ranged from 0,01 Euro/MWh to 900,00 Euro/MWh  in 2006. The price in fact varies by the hour (for example see tomorrow's APX prices), and by selecting the lowest priced hours it is possible to arrive at a tariff that is substantially below the normal base load tariff.

The savings that can be reached with the NWCS are depending on the "freedom" to choose only the hours with the lowest electricity price. When the refrigeration machines have to work only a few hours per day to cool the cold store, the freedom of choise is large. when the refrigeration machines are practically running continuously at maximum capacity, there is almost no freedom of choise, and consequently the savings are smaller. The same dependency on refrigeration capacity is applicable when using the normal night tariff, but compared to the normal night tariff operation, the NWCS will always arrive at lower costs.

The investments for the NWCS are small, because the imlementation of the NWCS is limited to a change of the refrigeration machine's control system. Typically, the implementation costs are in the order of 12.500 Euro and will have a pay back of only a few months. In most cases the existing control system can be maintained, and the NWCS is used to provide input to the existing control system.