© ASTRON

Every weekend, an automatic test verifies LOFAR2 Station functionality on four UniBoards in the digital lab. This setup consumes about 500 Watt. The test takes a few hours, but we left the setup always on. Per year this then takes about 5000 kWh, costing 1250 Euro per year at 0.25 Euro per kWh.

Instead of running the LOFAR2 Station functionality, the UniBoards can also run a low power image. If we run this low power image during the week and only load the LOFAR2 image when the test is done, then the setup takes about 250 Watt on average. I mentioned this to Pieter Donker, and he said we can also remote power off and on the UniBoards. Pieter wrote a program to control this remotely and now the UniBoards are powered off during the week and only turn on during the test. The average power consumption now dropped to about 70 Watt, so about 700 kWh per year, and costing about 175 Euros per year. Retrofitting this power saving was about two days work and saves over 1000 Euro per year. Power cycling does influence equipment lifetime, but at fewer than 100 cycles per year, the impact is expected to be limited.

In the future, we should design setups with remote power controls from the start to minimize standby consumption. Every watt-year saved is worthwhile!

Tip: It is easy and fun to do these kWh energy consumption calculations in your head, by assuming that a year contains 25 hours * 400 days = 10000 hours. To get a practical feel for 1 kWh, know that 1 liter of fuel or 1 cubic meter of natural gas contains about 10 kWh. Thus a device drawing just 1 Watt continuously, will cost 2.50 Euro annually and consume as much energy as available in 1 liter of fuel, or 1 m3 of gas, or 4000 1.2V 2Ah penlight batteries.