Tuesday, September 06, 2011

For *off-grid* PV solar, we have reached and exceeded fridge parity!

My father has a house at west point, and since the electricity grid (nor the water grid) does not reach there, a combination of power alternatives does the job for off grid. Just a few years ago, the most economical off grid fridge alternative was a gas fridge. A twelve volt power system with four Lead acid batteries for storage and one solar panel (80 W) was enough for a tiny (all 12V) bar fridge, lighting, tv and charging of phones. Now with just 2 80W solar panels and a few extra batteries for good measure, there is enough power for a full size 12V fridge freezer! Being that the house is not always occupied, the fridge can stay on and neither drain money nor waste food. Air conditioners are still most economical with diesel generators run as needed, and gas cannot really be beaten for cooking, but I believe this is a very important milestone for solar over fossil fuels for off-grid purposes. This has required *NO SUBSIDIES*. It is prohibitively expensive to convert a system optimised for greed feed-in to a system optimised for off-grid purposes. This is why greed feed-in is useless in power blackouts - no storage - no internal power regulation - inefficient upconversion from 12V to 240V.

6 comments:

Dr Clam said...

It is prohibitively expensive to convert a system optimised for greed feed-in to a system optimised for off-grid purposes.

Evidence? Your next line, about this being why they are useless in blackouts, is a non sequitur. Our plan is to buy more solar panels when the subsidy expires - and batteries - both of which will be cheaper then - and I don't think the electricianship required to move off-grid will be large compared to the capital cost of that stuff. Unless the mining boom has left only one electrician within 400 km, and he is insane with greed.

Marco said...

A system optimized for off grid purposes requires 12V lighting, refrigeration, tv chargers etc. I was kicking myself because we have just purchased a new 240v second fridge. A rough rule of thumb based on our off grid experience is that you would need about double the panels and storage to stick with 240v appliances than you would with 12v appliances (most electronics wastes a heap converting back down to 12v dc after). 12v systems can be done yourself with the minimum of electrical experience and has little electrocution risk. Changing to a load self management from a demand system can be fraught with gotchas. The next door neighbor spent over100000 dollars on solar +batteries+ standard 240v system and has air cons etc. But failure to manage power means frequent blackouts for them.

Marco said...

It was about $1000 for a 12v fridge. About 320W and 6 lead acid batteries required for Titos modest self-installed system. You would probably need 640W and 12 batteries for the same appliances in 240v installed by electrician.

Dr Clam said...

All very useful information, much thanks!

Jenny said...

I've been keeping a bit of an eye on the power it yourself option. Last time I checked, the cost of batteries (including the cost of disposal - they have a specific lifespan) meant there was no advantage in setting it up compared to running off the grid. I also cringe when I dispose of batteries - they are the one "environmental disposal" issue that I am concerned about...not necessarily because I've decided they are the worst. I think I just picked one to be concerned about & chose one that isn't highly publicised.

Marco said...

Lead acid batteries are actually very recyclable (there is battery recycling stations at the dump).

They are prohibitively expensive for our situation (suburban reliable access to grid), but a 1kw diesel generator would be extremely useful for natural disasters, and cost effective. Rural situations with marginal access to grid makes the battery+solar option much better for both emergency and long term off-grid use. Many rural properties north of Townsville were cut off from the grid for weeks or even months after Yasi.