Monday, 29 July 2013

A Smart New Fridge

We got a new fridge in June. The old one had stopped making ice and a guy had come to try and repair it several times before deciding that it needed replacing. It was still under a ten-year guarantee, but only just. I think the ice maker may have been damaged in the move. Not complaining about a new fridge. We have nothing to lose but energy, resource depletion and pollution from the extra parts on their way in and out of the world.

Looking for a silver lining, fridges seem to have become more efficient over the years since we got the last one. 

The sizes are comparable - 500 litres for the old one, 510 for the new - and the rated power consumption of the heat pump has improved around 10% from 110 Watts to 100 Watts. 

The defrosting power consumption has improved much more significantly, from 160 Watts to 93 Watts. That's around 40%.

In other words, the old fridge used more electricity to heat up the pipes inside to melt ice forming on them than it used to cool itself. The new fridge uses slightly less. Of course this is the power used when it's switched on, which is not all the time.

At least I think this corresponds to less power use. It may be that the defrosting is switched on 40% more of the time, and it's using exactly the same amount of power to do the job.

The new fridge has a rated consumption of 200 kWh per annum. That's less than 1 kWh per day. It works out around 23 Watts. So most of the time it's not using any electricity. Either the heat pump or the defroster is on around a quarter of the time.

Defrosting used to be a regular event for fridge-owners, requiring the fridge or freezer to be unloaded and switched off. Now the fridge switches on heating elements in the pipes to stop frost occurring. Presumably the improvement in efficiency that defrosting brings is much greater than the extra energy used defrosting. If the fridge is trying to cool through pipes coated in ice, it is going to do a very poor job since the ice will stop the heat flowing into the coolant in the pipes. The coolant will then get much colder, using much more energy. 

As we know, frost will occur where there is humidity in the air and low-temperature surfaces, which you are likely to get in a fridge. Another approach to defrosting would be to remove all the humidity from the air within the fridge, but this may be less reliable.

I was hoping that there would be more energy saving functions, or at least energy bill saving devices, for example running as much of the freezing and defrosting as possible at night. There is a "shift peak" function, but it just puts off heavier load activity for four or five hours. It doesn't actually have a clock in it, so it wouldn't know whether there is any cheap night-time electricity to use. If it doesn't even know the time, it's not really that smart. 

It has green lights coming on to say "eco", but it would be really nice to have a display of how much electricity it is actually using. 

Another thing that makes it less efficient is the drawer inside. The manual clearly states that to keep the fridge efficient, you should open the doors as little as possible. The most important power saver is probably knowing where everything in the fridge is, although this can be tricky if you have the kind of dietary habits that require 500 litres of fridge. The old fridge had double doors for the main section, with two drawers at the bottom. The one of the left had an egg tray. We used to keep cheese in the one on the right, so we'd open the left door for eggs, and the right door for cheese. 

In the new, but not necessarily improved, model there is only one drawer at the bottom. To open it you have to open both doors. Not the smartest of designs in terms of forcing you to open both doors. The egg tray is now in one of the shelves in the door on the right. Since they have enough headroom to hold a tin of beer, this is not the smartest use of space either. But it's new, so beggars can't be choosers.